A / *< OF 5- "6 II J13HSN03 d>' ^ ! jUhsnod l -*© -I- -m -N> «8 -€ 1 ! 3 5 if! i jj llil I t" I! lii r o — T- 8 I 8 fa J The shallowest air saturation depth to date is the 26-foot program of LORA (English, 1973) . The most significant feature of the LORA program is the fact that both aquanauts safely surfaced with no decompression after spending 24 hours at a depth of 26 fsw (which included four excursions to 35 fsw). Further details of this program are discussed later. The deepest saturation on nitrogen-oxygen is 120 fsw, which was achieved in the NOAA-OPS program. During this program, the subjects made upward excursions to a depth of five fsw and downward excursions to a depth of 300 fsw. This program also is described in detail later. Larson and Mazzone (1967) reported on the first program designed specif- ically to study vertical excursions from air saturation. Following a series of dry chamber studies using dogs, a similar series of studies was conducted using 13 human subjects. Air was breathed both during the saturation and excursions. The saturation depth was 35 fsw, with excursions as deep as 165 fsw. With one exception, only a single excursion was made by each pair of subjects following a 24-hour period of saturation at 35 fsw. Table 1 shows the excursion times and decompression profiles. Table 2 shows the results of the human and animal excursion series. TABLE 1 Excursion times and decompression profiles* Depth and Bottom Time of Excursion Decompression to Surface 165 ft for 30 min 135 ft for 60 min 117 ft for 90 min 100 ft for 120 min Ascent to 10 ft at 5 fpm 2 hrs on air at 10 ft 1 hr on 2 at 10 ft Ascent to surface at 2 fpm 105 ft for 150 min Ascent to 20 ft at 3 fpm 20 min on air at 20 ft Ascent to 10 ft at 2 fpm 2 hrs on air at 10 ft 1 hr on 2 at 10 ft Ascent to surface at 2 fpm 100 ft for 240 min Ascent to 20 ft at 3 fpm 40 min on air at 20 ft Ascent to 10 ft at 2 fpm 2 hrs on air at 10 ft 1 hr on 2 at 10 ft Ascent to surface at 2 fpm * (Larson and Mazzone, 1967) TABLE 2 Description and results of animal and human excursion series* A. * Animal Series B. Human Series Saturation exposures 7 Excursions 165/30 13 135/60 8 117/90 4 109/120 4 105/150 4 100/240 3 Total 36 Saturation exposures 15 Excursions 165/30 6 135/60 4 117/90 1 109/120 2 105/150 2 100/24Q 2 Total 17 Cases of decompression sickness... Cases of decompression sickness * (Larson and Mazzone, 1967) Larson and Mazzone constructed a no-decompression curve for downward ex- cursion dives from saturation at 35 fsw (Table 3) . It was their opinion that the total absence of bends during the study suggests that these data "may err on the conservative side. " The excursion times calculated and tested during NOAA OPS (Hamilton, Kenyon, Frietag and Schreiner 1973) for a depth of 35 fsw are also shown in Table 3 for comparison. (The NOAA OPS program will subsequently be described in detail.) It is seen that the excursion times tested during NOAA OPS are considerably shorter than those tested by Larson and Mazzone. A study was conducted for the Tektite I program to determine the safe surface interval between direct surfacing from a 42-foot saturation depth (on a normoxic breathing mixture) and the onset of decompression sickness (Edel 1970) . This experiment also was designed to develop treatment tables to be used in the event of bends following accidental surfacing. Six subjects were saturated in a normoxic atmosphere at 42 fsw. All six were decompressed to the surface in one minute. Two subjects each remained at the surface for 10, 15 and 20 minutes prior to recompression to 42 fsw. No symptoms were noted for the 10 or 15 minute groups. One subject in the 20-minute group developed serious neurocirculatory symptoms after 19 minutes, which dissipated rapidly upon recompression to 60 fsw. Based on these experi- ments, "a surface interval of 15 minutes after accidental surfacing before recompression to 60 feet, was accepted as safe against the liability of dys- barism" (Beckman and Smith 1972) . TABLE 3 Allowable bottom times (min) for various depths Depth (Feet) From Surface (U.S. Navy) From 35 Feet (Larson and Mazzone) From 35 Feet (NOAA OPS) 165 5 30 25 135 10 60 46 117 17 90 — 109 20 120 — 105 22 150 108 100 25 240 143 Table 4 was developed during the Tektite I program for treatment of ac- cidentally surfaced divers and for use as an emergency post-saturation decom- pression schedule beginning at the 40 fsw stop. During the open-sea phases of Tektite I and II, support divers were trained to retrieve a surfaced aqua- naut and recompress him within 2-3 minutes, which was well within the recom- mended safe surface interval. The limits for excursions to 25 and 100 fsw breathing air used during the 42-foot Tektite program were four hours. While several upward excursions to 25 feet were made, the seafloor topography did not permit downward excur- sions beyond a depth of 65 feet. The Tektite II program also included laboratory studies of vertical ex- cursions from a normoxic (94.8 percent N 2 and 5.2 percent 2 ) saturation at 100 fsw (Edel, 1970) . Two subjects each were used in ascending and descend- ing excursion experiments. In the downward excursion tests, the subjects spent six hours at 175 fsw breathing air, followed by a three-minute ascent to 103 fsw with no symptoms of bends noted. In the upward excursion tests, the subjects ascended from 100 fsw to 70 fsw. One subject spent eight hours at 70 fsw breathing air; four hours doing weight lifting exercises, followed by four hours of rest. The other subject spent four hours at 70 fsw breathing N2-O2 while performing physical exercise. TABLE 4 Tektite I and II treatment and emergency decompression schedule for use in 50-foot missions (saturation depth 42 fsw) Depth Total Breathing (fsw) Time 20 decompression time 20 media 60 Oxygen + 5 25 Oxygen 55 20 45 Air + 5 50 Air 50 20 70 Oxygen + 5 75 Oxygen 45 20 95 Air + 5 100 Air 40 20 120 Oxygen 4- 15 135 Air 25 60 195 Air 4- 5 200 Air 20 90 290 Air 20 30 320 Oxygen 4- 5 325 Oxygen 15 90 415 Air 15 60 475 Oxygen + 5 480 Air 10 120 600 Air 10 60 660 Oxygen + 5 665 Oxygen 5 150 815 Air 5 60 875 Oxygen 4- 5 880 Air Surface Total decompression time: 880 min, or 14 hr and 40 min. Total 100% oxygen inhalation: 4 hr and 50 min. Both subjects returned to a depth of 103 fsw without incident. Based on these studies , the Tektite Medical Board agreed to allow upward excursions from 100 fsw to 75 fsw for four hours, and downward excursions to 175 fsw for four hours, with a 12-hour interval between any descending excursion arid an ascent to 75 fsw (Beckman and Smith 1972) . In 1972, the FLARE (Florida Aquanaut Research Expedition) program was conducted off the southeast coast of Florida) . Twenty-five marine scientists in teams of three, saturated for five days on the seafloor at depths ranging from 42-45 feet. The overall operation is depicted in Fig. 2. - ,V/.il *^ : Fig. 2. Artist's conception of project FLARE Vertical excursions were carried out as follows: upward excursions were limited to 20 fsw. No-decompression schedules were established for downward excursions by modifying the US Navy Standard Air Table I-II, No-decompression limits, and repetitive group designation table for "No-decompression" dives, see Table 5. Table 5 was used in accordance with directions given in the US Navy Diving Manual for Tables 1-11, 1-12, and 1-13 with the exception that the surface interval noted in Table 1-12 is considered the interval taken in the habitat. Further, when following a descending excursion by an ascending excursion the diver had to be in repetitive group E or lower to go to 30 fsw and in group B or lower to go to 20 fsw. Aquanauts were instructed to plan their daily diving schedules in order to make any antici- pated ascending excursions prior to a descending excursion. The most notable aspect of the FLARE program relating to vertical excur- sions was the manner in which decompression was achieved. Because the habitat Edalhab was not a pressure vessel, the aquanauts were required to utilize the small decompression chamber located on the deck of the support ship LULU. The procedure called for the aquanauts (one at a time) to ascend from the habitat to the surface next to the support ship. The support crew assisted the aquanaut up the ladder and into the waiting double-lock deck decompression 8 TABLE 5 No decompression limits and repetitive group designations for downward vertical excursions from a saturated depth of 35 to 45 fsw Depth From Surface (ft) Limit of Time at Depth (min) Repetitive Group A B C D E F G H I J K L M N O 60 65 70 75 80 85 90 100 120 140 160 300 300 300 300 300 300 180 90 40 25 10 60 30 20 15 10 5 5 120 60 40 30 20 10 10 5 200 100 60 40 30 20 20 10 5 300 150 90 60 50 30 25 20 10 5 200 120 90 60 40 30 25 15 10 300 150 110 80 50 40 30 20 15 5 200 145 100 70 50 40 25 20 10 300 180 120 90 70 50 30 25 200 150 100 90 60 35 300 130 120 100 70 40 200 140 110 80 300 180 130 90 200 150 240 180 300 chamber„ Once the first- aquanaut was safely inside and recompressed to the saturation depth, the procedure was repeated with the other aquanauts. This entire procedure had been rehearsed until the elapsed time between the aqua- naut leaving the seafloor and being recompressed in the chamber was only two minutes. This was well within the 15-minute safe surface interval determined during the Tektite I program. Decompression was accomplished using the sched- ule shown in Table 6. This schedule is based upon the one successfully used in the Tektite II program, but was modified in the following manner: Because of transient reduction of pressure to sea level during transfer from habitat to deck chamber, a 40-minute period of oxygen breathing was carried out in the habitat just prior to ascent. As an added safety fac- tor, a 30-minute period of oxygen breathing at 50 fsw was carried out in the deck chamber as soon as the last aquanaut was recompressed to sat- uration depth. Some 30-minute oxygen-breathing periods during decompres- sion were consolidated into 60-minute periods. The decompression stop at five fsw was eliminated. In its place was a 30-minute period of oxy- gen breathing at 30 fsw, followed by ascent to the surface on oxygen. The 25 excursions to the surface for decompression as described above were achieved without incident and became routine by the end of the mission, although two bends cases were reported during decompression. The advantages of this procedure with respect to cost, the lack of the need for a diving bell and simplicity are obvious. A nitrogen-oxygen saturation excursion program has been underway for the past four years in Cartagena, Spain (de Lara 1975). It is being conducted by the Spanish Navy and is referred to as the TONOFOND Experiments. Ten TABLE 6 Standard decompression schedule for Project FLARE Elapsed Time Depth Duration Breathing Medium °2 Dose Cum. 2 Dose Notes (min) (FSWG) (min) (UPTD) (UPTD) Bottom 40 Air 116 116 In habitat Ascent Surface Air Transfer to DDC Bottom Air Air Recompression in DDC 1 50 30 °2 0, 96 212 Compress 1 F/sec 30 4- 30 120 Air Decompress 1 F/sec 150 155 25 5 170 Air Air Decompress 1 F/min 325 25 60 o 2 130 342 385 4- 5 Air 390 20 200 Air 590 i 5 Air 595 15 20 Air 615 15 60 o 2 102 444 675 15 40 Air 715 15 60 °2 102 546 775 15 20 Air 795 + 5 Air 800 10 30 Air 830 10 60 °2 90 636 890 10 40 Air 930 10 60 °2 90 726 990 10 40 Air 1030 1 5 °2 10 736 1035 30 30 °2 71 807 1065 1 30 °2 51 858 1095 Surface 18 hr: 15 min 10 saturation experiments, using three or four subjects each, have been conducted to date. Table 7 summarizes the TONOFOND experience and reveals a remarkable similarity to the allowable excursion times determined by the NOAA OPS pro- gram. In several cases the TONOFOND excursions were significantly larger than those allowed by NOAA OPS but, in most cases, the times were comparable. If the results could be adjusted for differences in habitat oxygen, the dif- ferences in allowable excursion time would be even less. No symptoms of decompression sickness were observed following any of the excursions from saturation. Two cases of decompression sickness did occur however, several hours after completing decompression. Both cases responded successfully to treatment. A significant decrease in nitrogen narcosis was observed as compared to exposure to the same depths when diving from the sur- face. III. THEORETICAL BASIS FOR EXCURSION DIVING Most, if not all, theorists in diving physiology accept the concept that an excursion to a deeper depth, when saturated at depths greater than one atmosphere (absolute) , can be conducted safely by using a conventional diving table on a "differential" basis. Thus, a diver saturated at 100 fsw could descend to a depth of 180 fsw and remain for the same period of time as he could when diving to 80 fsw from the surface. It has been demonstrated repeatedly, however, that longer excursion times can be used from saturation than from the surface. Although the underlying mechanism is not clear, the concept has been exploited such that excursion diving from saturation is now a practical, effective tool. A pragmatic ap- proach has been used in the development of this capability (Schreiner and Kelly 1971) . Their study formed the computational basis for the NOAA-OPS experiments described in this document. The mathematical "model" used was developed primarily by Schreiner, following the work of Haldane, Workman, and others. The basis for the model is that gas is transported in the body by the blood, which is assumed always to be equilibrated with tissue. This concept is termed a perfusion limited model. According to this model, gas is taken up or given off by the tissues exponentially as a function of the difference in inert gas partial pressure between the lungs and the tissues. For purposes of decompression theory, the tissues of the body are concep- tually divided into compartments which exchange gas at different rates. If during decompression, the release of gas from these tissue "compartments" exceeds a predetermined value, decompression must be stopped for a period of time. The critical set of factors in this approach is the matrix of gas loadings against which the running totals of inert gas partial pressures are compared. The "matrix" used for the NOAA-OPS computations was derived empirically, by analyzing the gas loading patterns of nearly 200 actual dives during which 11 o •H co co W (j to fi -H «—» CO c O n •H CN p g ■H u X w (1) g H •H O •H Eh en < g m 4J -P o n & CD PQ S o 00 ft +J vfj >«D *£> 00 00 00 00 O -H S Q 0O 00 -vf ^f •H ^-, -P CO U rrj P Q Q — oo oo in o H h oi n ^f en CN CN ^T CM "sT kD KO ^f <£> cyiCNvD ^r m o CO CO Pn O CO S CM O o 3 t C O •H a T! tp CD CI P •H to no 1 X rH CD H rd CO 3 CI) -P g () •H rfj Eh * * * 12 accurate records had been kept. Those gas loadings which did not result in decompression sickness were accepted as safe, while those which produced de- compression sickness were considered to be unsafe. Using the computer- generated gas loadings, a manual selection process was employed, such that some judgment was necessary in producing the completed matrix. The NOAA-OPS project required computation of no-decompression excursions for depths ranging from 30 to 300 fsw. The computations took into account the gas loadings in each tissue compartment at the beginning of an excursion as well as gas uptake and elimination during the excursion. The loadings were compared with the matrix to determine an excursion time which did not violate the gas loadings permitted by the matrix. Since a substantial amount of gas may remain in the slower compartments until the next excursion, and due to a lack of repetitive excursion data, the entire sequence of excursions was planned in advance. Because operational requirements also include the need for ascending ex- cursions, such calculations were part of the NOAA-OPS program. Although no body of data was available for use in preparing a matrix for ascending excur- sions, it is known that gas is released slowly enough to allow short upward excursions. Data from surface decompression experience and from a few ascend- ing excursions made during the Tektite I Program were used to form crude curves showing the time /depth range of safe ascent. These data, plus tolerable gas excesses known to be acceptable in the slow compartments, allowed computation of a set of short ascending excursion tables. As with descending excursions, ascents are affected by gas loadings existing at the beginning of the excur- sion. It must be kept in mind that while the concepts of tissue compartments and gas loadings imply inviolate principles, and the notion that divers' bod- ies behave according to man-made equations, this is far from true. For ex- ample, the occurrence of asymptomatic bubbles is not considered by the theory. Fortunately, the concepts can be made to work in practice and several hundred excursions have safely been conducted, both in the laboratory and in the open sea. Further work is necessary to understand and expand the theoretical basis for excursion diving in order to improve the effectiveness of the working diver. IV. LABORATORY STUDIES Several laboratory (chamber) experiments have been conducted for the pur- pose of studying air or nitrogen/oxygen saturation diving, involving extensive vertical excursions. In some programs, the laboratory experiments were de- signed specifically as a pre-cursor to open-sea studies, while in others no immediate field program was anticipated. This section will address those laboratory experiments in which the vertical excursions were the principal area of interest. 13 IV-A. NOAA OPS The NOAA OPS program was initiated and sponsored by the National Oceanic and Atmospheric Administration (NOAA) and carried .out by the Union Carbide Corporation in response to a need to extend scientific diving in the ocean. The biomedical research program was planned and executed by personnel of the US Naval Submarine Medical Research Laboratory (NSMRL) , New London, Connecticut. Purpose ; The purpose of the program was to develop and test decompression proce- dures and vertical excursion profiles, to study adaptation to nitrogen nar- cosis, and to assess further the stresses of two weeks of nitrogen saturation (Hamilton, Kenyon, Frietag and Schreiner 1973). Tables were needed which would serve the entire depth range in which a nitrogen-based habitat might be located. Location: Union Carbide Corporation, Environmental Physi- ology Laboratory, Tarrytown, New York Dates: October 17 1972 to January 25, 1973 Duration: NOAA OPS I — 18 days NOAA OPS II - 16 days Saturation NOAA OPS I — 30, 90 feet Depth: NOAA OPS II - 60, 120 feet Breathing Storage gas — Normoxic Gas: Oxygen — 4.2 to 10.5% Excursion gas- Air Subjects: NOAA OPS I and II — 3 Facility: The experiments were performed in the Experi- mental Diving Facility operated by the Environ- mental Physiology Laboratory of the Union Carbide Research Institute.* * This facility was dismantled in 1975 and relocated to Tarrytown Labs, Tarrytown, New York. Facility Description : The facility is shown schematically in Fig. 3. Four chambers comprise the complex, each largely independent of the others in operation and intended function. The main lock of the White Whale is a 5.5 x 7.5 foot cylinder with a volume of 138 cubic feet. The entry lock, 41 inches in diameter, adds another 37 cubic feet of volume to the system when it is open to the inside. 14 I ©WATER DELUGE SYSTEM TANK ©TELETYPE ©COMPUTER SYSTEM ©LOCKER ©TABLE ©COMMUNICATIONS ©EXPERIMENTAL APPARATUS ©ENVIRONMENTAL ANALYZERS © HOT WATER TANK © COLD WATER TANK @ DEHUMIDIFIER STAIRWAY & GAS STORAGE ?S divingT ; LOCKER | !© SHOP Fig. 3. Experimental diving facility used for NO A A- OPS . The Purisima chamber consists of two interconnected spheres each five feet in diameter. The two chambers are designated A and B, with A connecting to the main lock of the White Whale. Two hatches between A and B permit them to be pressurized independently. The primary function of the 7 5-foot North Sea Hilton is to provide a living area in which divers wash, eat and stretch out or stand up during long saturations. 15 The White Whale DDC is rated to 675 fsw, Purisima to 1,000 fsw and the North Sea Hilton to 600 fsw by the ASME code for unfired pressure vessels. Most operations were conducted from the control module including pressuri- zation, mask breathing, gas selection and pressure, supply and chamber pres- sure, timing, electrical system and fire extinguishing controls. Appropriate instruments were available for measuring gas composition, temperature, timing experiments, communicating, recording and video taping. An IBM 370 computer was used for developing the diving and excursion matrix and for the analysis of biochemical data. A 316 Minicomputer was used for maintaining a time base for experiments on subjects and for recording environmental data such as tem- perature and pressure. Divers : Six, male subjects were used during NOAA OPS ranging in age from 19 to 39. Five of the six divers had previous diving experience in the Union Car- bide Laboratory. All were qualified scuba divers, in excellent health, and eager for the experience. Procedure ; (Calculation of the excursion matrix) The overall experimental plan for the project called for the use of a data base from which new excursion tables could be developed. The best data available were used to serve as a base for formulation of the new matrix. The data had to have certain characteristics. To be of maximum utility, they had to come from well-documented exposures of a suitable population in which decompression sickness had been encountered occasionally. Dives in which the mission or emotional involvement of the participants prevented ac- curate documentation of either the profile or decompression results would be of limited value. Another special requirement was to have a broad range of exposures, as the nature of excursion diving from saturation dictates the need for variable matrix elements throughout a wide range of both times and depths. Because the NOAA OPS program involved saturation as well as no-decompression excur- sions during saturation, both slow and fast half-time tissue compartments were involved. The data acquisition began with the nitrogen matrix developed by Workman (1965) which reflects the considerable experience of the US Navy in air diving, The search was expanded by direct inquiry to sources known to have well- documented data not considered in Workman's matrix. A listing of dives and their sources is given in Table 8. A total of 84 dives were processed which represented 189 man-exposures. To use the gas loading matrix method of making the transition between past experience and future operations, a technique was developed permitting the weighting of each dive. Times, depths, and severity of each incident 16 TABLE 8 Data used in the development of the NOAA matrix 32/02 Origin of Data Number Number Depth Total bottom of of of time of Dives Divers Dives Dives (min) Insitute for Aviation 1 2 2 3m 6660 Medicine of the DFLVR, 2 6 2 3m 15000 Germany 2 11 90m 5 1 3 12m 480 1 3 15m 450 2 3 18m 450 1 3 21m 360 1 3 24m 360 2 6 27m 240 1 3 30m 240 1 3 33m 180 1 3 36m 180 1 3 39m 180 1 2 30m 3000 1 2 40m 3000 1 1 50m 3000 1 1 60m 3000 1 1 70m 2280 1 1 70m 3000 1 2 20m 8640 Naval Submarine 1 1 55fsw 313 Medical Center, 1 1 55fsw 319 New London , Conn . 1 1 55fsw 30 1 1 58fsw 23 1 2 45fsw 3600 1 1 45fsw 1602 U.S. Navy 2 4 33fsw 1440 Experimental Diving 5 8 33fsw 2160 Uni t , Washington , D . C . 3 4 99fsw 360 3 4 99fsw 540 1 4 99fsw 720 3 6 140fsw 90 3 6 140fsw 120 6 12 140fsw 180 8 16 140fsw 240 3 6 140fsw 360 17 TABLE 8 (cont.) Origin of Data Ocean Systesm, Inc. , Tarry town, N. Y. 1970-1971 J&J Marine, Houston, Texas Number Number Depth Total bottom of of of time of Dives Divers Dives Dives (min) 1 2 200fsw 30 1 2 400fsw 10 1 2 400fsw 30 1 2 300 fsw 35 2 2 33fsw 1440 1 2 30fsw 1440 2 4 115fsw 360 6 12 106fsw 360 1 1 130fsw 720 2 5 132fsw 720 2 6 137fsw 720 of decompression sickness were considered, as well as the gas loading history of each compartment. Equivalent procedures also were followed for profiles which did not result in decompression sickness. Quantitative probabilities were assigned to each element in the matrix. Subjective judgement was used instead of comprehensive statistical analy- ses. This proved to be efficient and effective for the data used. The matrix which resulted from this analysis is shown in Table 9. Note that M-values decrease with increasing half-times, and, that they increase by about 10 or 12 feet with each additional 10-foot depth increment. Although this matrix allows the computation of successful tables, it has defects which might be remedied by additional data. For example, following the increase with depth beginning with the sixth compartment, a discontinuity is seen between 80 and 90 fsw. There is every reason to believe that these functions should be represented by smooth curves. More data however are needed in order to properly smooth them. After completing a workable matrix, the no- decompress ion excursion bottom times were computed. The criterion for a no-decompression dive was simply that no compartment tt value should violate the appropriate M-value. That is, the M-value is applicable to the point 10 fsw deeper than the storage depth. The compartment which allows the least amount of time at the bottom is the controlling tissue and that time is the no-decompression time for that depth. The NOAA OPS descending excursion profiles were calculated ac- cordingly. With saturation diving, not only is there the water and sea floor below, but also there exists an environment above the storage depth, which generally 18 TABLE 9 NOAA OPS constraint matrix 32/02 M-values for each compartment with halftime values in min Depth 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 fsw 5 10 20 40 80 120 160 200 240 320 480 640 720 1000 1280 250 380 360 335 333 330 330 327 315 314 313 311 308 307 302 297 240 370 350 325 32 3 320 320 315 304 303 302 300 297 296 291 286 2 30 360 340 315 313 310 310 304 293 292 291 289 286 285 280 275 220 350 330 305 303 300 299 292 282 281 280 278 275 274 269 264 210 340 320 295 293 290 288 281 271 270 269 267 264 263 258 253 200 330 310 285 283 280 277 269 260 259 258 256 253 252 247 242 190 320 300 275 273 270 266 258 249 248 247 245 242 241 236 231 180 310 290 265 263 260 255 246 2 38 237 2 36 2 34 231 230 255 220 170 300 280 255 253 250 244 235 227 226 225 223 220 219 214 209 160 290 270 245 243 240 232 224 216 215 214 212 209 208 203 19 3 150 280 260 235 233 230 220 212 205 204 203 201 198 197 192 187 140 270 250 225 223 219 208 201 194 193 192 190 187 186 181 176 130 260 240 215 213 208 196 189 183 182 181 179 176 175 170 165 120 250 2 30 205 198 193 183 178 172 171 170 168 165 164 159 154 110 240 220 195 183 180 170 166 161 160 159 157 154 153 148 143 100 230 210 175 170 167 158 155 150 149 148 146 143 142 137 132 90 220 200 160 158 156 142 141 139 138 137 135 132 131 126 121 80 210 190 150 148 145 119 118 118 118 118 118 118 118 115 110 70 200 180 142 138 132 114 113 113 113 113 113 110 109 104 99 60 190 168 134 128 120 108 107 106 105 104 102 99 98 93 88 50 172 152 128 113 106 98 97 95 94 93 91 88 87 82 77 40 154 136 117 98 93 88 86 84 83 82 80 77 76 71 67 30 136 120 102 84 80 76 75 73 72 71 69 66 65 60 57 20 118 104 87 70 67 64 63 62 61 60 58 55 54 50 47 10 100 88 72 56 54 52 51 51 50 49 47 44 43 40 37 has not been accessible. To ascend shallower than the storage depth is in effect to begin decompression. According to the M-value concept, if the tt values are below the M-values, then it is safe - with some degree of confi- dence - to ascend another 10 fsw. This process continues until a diver sur- faces or is as shallow as he wishes to be. The M-values, however, imply that the diver is going to spend an indefinite amount of time at this shallower depth and does not consider the probability of bends for a brief period of violation. In fact, a diver can exist in a state of supersaturation which violates the M-value for a brief period of time, with an acceptable probabili- ty of bends, as long as he returns within a time limit which is consistent with that probability. Using this concept, ascending excursion times were computed. 19 In order to safely and effectively carry out the program, a total dive profile was devised for both phases. Gas loadings were accumulated continu- ously in the 11 compartments (up to 480 minutes) for each two-week exposure. The first excursion was begun with the gas loadings that prevailed at the end of 41 hours of equilibration at 30 fsw. After this excursion, re- equilibration to 30 fsw was allowed prior to the second excursion and so on. This resulted in one continuous gas loading record for the entire period. The excursions computed and tested for NOAA OPS I and II are given in Tables 10 and 11. TABLE 10 Excursions computed and tested (NOAA OPS I) Depth Dive time Day Time 1700 fsw 30 (min) 1 2 30 3 1000 120 62 3 1400 120 60 4 1000 85 316 5 1000 200 10 5 1400 200 10 6 1000 100 104 6 1400 100 100 7 1000 150 30 7 1400 30 7 2000 90 8 9 1000 175 300 10 1000 60 35 10 1400 40 20 11 1000 200 51 11 1400 200 50 12 1000 40 10 12 1400 60 35 13 1000 250 22 13 1400 250 22 13 1730 90 14 1500 Remarks Go to 30 fsw Go to 90 fsw Ascending excursion Ascending excursion Begin decompression Decompression complete Computations for OPS I excursions were "square wave", in that a 10- minute dive implies departure from habitat and arrival at excursion depth at the same instant, and the reverse at the end of the excursion. In practice, the corners were cut so as to approximate the same gas- pressure exposure in tests as was calculated. 20 TABLE 11 Excursions computed and tested (NOAA OPS II) Depth Dive time Day Time 1900 fsw (min) 1 2 120 3 1000 250 53 3 1400 250 53 4 1000 75 37 4 1400 55 9 5 1000 55 8 5 1400 75 39 6 1000 200 360 7 1000 300 18 7. 1400 300 18 7 1800 120 8 0848 60 9 1000 150 72 9 1400 150 72 10 1000 115 347 11 1000 5 13 11 1400 5 16 12 1000 200 22 12 1400 200 22 12 1600 60 13 1121 Remarks Go to 120 fsw Ascending excursion Begin decompression Arrive at 60 fsw Begin decompression Surface In OPS II the computations were improved so as to account for compressions and decompressions. These were not included in bottom times. The tests followed the calculated profile quite closely. Because of the lack of any significant signs or symptoms of decompression sickness, the computed allowable time for OPS II was extended by 25% for the ascending excursions. These tests resulted in mild bends pain in one subject, suggesting that the original computations approached the safe limits. The excursion depths were chosen to provide a good range of testing, and to provide suitable exposures for performance monitoring. For example, 200 fsw and 250 fsw were repeated as often as possible to permit replication of tests during excursions. The environmental parameters existing during the program are shown in Table 12. 21 TABLE 12 NOAA OPS environmental parameters Parameter Oxygen (per cent atm) OPS I OPS II Saturation depth (fsw) 30 90 120 60 Typical range 10.5 - 11.0 0.20 - 0.21 5.2 - 5.6 0.19 - 0.21 3.9 - 4.6 0.18 - 0.21 7.2 - 7.8 0.20 - 0.22 High 12 .8 0. 24 7 .0 0. 26 5 .6 0. 26 8 .5 0. 24 Low 9.3 0.18 4.6 0.17 3.5 0.16 6.6 0.19 Carbon Dioxide (mm Hg) OPS I 30 6.5 - 8.5 13.8 4.2 90 6.0 - 8.0 12.8 2.0 OPS II 120 4.0 - 6.5 12.3 2.0 60 7.5 - 9.5 17.5 4.2 Temperature (°C) OPS I 30 22.7 + 1°C 40 22.7 ± 1°C 120 23.0 ± 1°C 25.8 17.0 60 25.0 ± 1°C 29.9 23.1 Relative Humidity (per cent) OPS II 120 65 - 75 96 39 60 50 - 60 66 35 22 Experim e nts ; An extensive series of physiological and medical experiments were, carried out during the program. These experiments are listed in Table 13. Descriptions of each of these studies can also be found elsewhere (Schaefer and Dougherty 1976; Langley 1973, Kinney, Luria, Strauss, McKay and Paulsen 1974; Kinney, Luria and Strauss 1974; Moeller 1974; Schmidt, Moeller, Hamilton and Chattin 1974; Langley and Hamilton 1975). General Procedures ; The program was divided into two 2-week saturation exposures. The saturation depths were 30 and 90 fsw, and 60-and 120 fsw in NOAA OPS I and II respectively. TABLE 13 NOAA OPS biomedical experiments Assessment of Decompression 1. Nitrogen washout 2. Doppler Ultrasonic 'bubble detection 3. Throughpass ultrasound 4. Bone density Nitrogen Narcosis 1. Psychomotor and cognitive performance 2. Somatic evoked brain responses 3. Visual evoked brain responses Tolerance of Exposure 1. Biochemistry 2. Dental-Oral tissue response 3. Aerobiology 4. Salivary microbiology 5. Immunology and ecology 6. Psychology Longitudinal Health Study The order of excursions was varied because of the interaction of ad- jacent profiles and to avoid any consistent patterns. It was considered important to test ascending excursions the day after a long descending excursion. The order of presentation of the excursions is shown also in Tables 10 and 11. Two excursions were conducted each day. One at 1000 and one at 1400 hours. Pre- and post-saturation bounce dives were conducted to observe the effect on narcosis of direct descent to the same depth from saturation. When possible, the same depths were used for excursions from various storage 23 depths. These bounce dives also provided a baseline for use of the bubble detecting apparatus. Three were scheduled before and after each satura- tion (although not all were accomplished) . Work routines of under 10 minutes were used. A particular excursion may have had one, two, or three such cycles. Each of the three, chambers was arranged for certain activities and the divers moved about according to a rotation schedule. For descending excursions, performance tests and measurements of evoked brain response were administered upon arrival at the excursion depth. Near the end of an excursion, attention was focused on decompression studies including the nitrogen washout, ultrasonic and Doppler experiments. During ascending excursions, the decompression studies began at the beginning of the excursion and continued until after recompression to saturation depth. During the first week of NOAA OPS II, one subject was stricken with influenza and was decompressed from 120 fsw to the surface without incident. Medical coverage in NOAA OPS consisted of pre- and post-dive examination of the divers and medical surveillance during the dive. The examinations were given as part of the Longitudinal Health Study, an ongoing program at New London. This is a thorough medical and dental examination, and by a diver's entry into the program he will be given periodic examinations, including long bone x-rays as long as the program continues. Decompression Procedures ; The saturation decompressions carried out are shown in Table 14. Three divers were decompressed from 90 fsw, one diver from 120 fsw and two divers from 60 fsw. In addition, two divers were decompressed from 120 feet to 60 fsw. Decompression was conducted in a continuous mode for both NOAA OPS I and II. A continuous decompression means that at no time does the rate of decompression exceed a maximum level, based on a given criteria. It also means there are no decompression stops, although a stop can always be inter- posed if needed. In NOAA OPS I decompression from 90 fsw began three hours and eight minutes following a 22 minute descending excursion to 250 fsw. It was com- pleted 21 1/2 hours later with no signs of decompression sickness being ob- served. The criteria used were modified Ocean Systems Inc. and US Navy he- lium saturation procedures. Decompression for NOAA OPS II began three hours and 38 minutes after a 22 minute, 200 fsw excursion. Continuous decompression procedures were employed using 1/4 fsw intervals for the greatest possible gas elimination. The total decompression time from 60 fsw was 17 hours and 11 minutes. The final rate of ascent was 34 min/ft which was necessary only for the last two fsw. Oxygen breathing was not employed for decompression purposes, how- ever, it was used for nitrogen washout studies performed by NSMRL for short, periods of time. The oxygen was increased to 20.8 ± 0.2% before the start of decompression. No symptoms of decompression sickness were reported. 24 TABLE 14 Summary of decompressions from NOAA OPS saturation NOAA OPS I Criteria: Modified Ocean Systems Inc. and U.S. Navy helium saturation procedures . 90 fsw to sea level (Time: 1380 min) - 6 min/ft to 60 fsw -15 min/ft to 40 fsw -15 min/ft to 30 fsw -20 min/ft to 20 fsw -25 min/ft to 10 fsw -30 min/ft to sea level Oxygen 8 -*■ 11% Oxygen 17 ■*■ 21% Oxygen 21% Oxygen 21% Oxygen 21% Oxygen 21% NOAA OPS II Criteria: 480 min compartment; Matrix 32/02; continuous; 1/4 fsw intervals . 120 fsw to surface (for sick subject) (Time: 1842 min) - 6 min/ft to 90 fsw - 6 min/ft to 70 fsw -15 min/ft to 47 fsw -20 min/ft to 18 fsw -25 min/ft to sea level 120 fsw to 60 fsw (Time: 888 min) - 6 min/ft to 92 fsw -20 min/ft to 80 fsw -24 min/ft to 60 fsw 60 fsw to surface (Time: 1032 min) - 6 min/ft to 30 fsw -22 to -27 min/ft to 20 fsw -27 to -30 min/ft to 10 fsw -30 to -34 min/ft to sea level Oxygen 16.4% Oxygen 21% Oxygen 21% Oxygen 21% Oxygen 21% Oxygen 7.5% Oxygen 7.5% Oxygen 7.5% Oxygen 21% Oxygen 21% Oxygen 21% Oxygen 21% 25 NOAA OPS decompression times were much shorter than those used for Tektite and FLARE. Because the small number of subjects involved in NOAA OPS provided little statistical confidence in the results, they must be viewed with caution. It should be pointed out that although the decompression pro- files in saturation diving are dependent on a single limiting compartment (the slowest) , the rates can change as the matrix changes with depth. A significant relevant factor is the rate of pressure reduction. Early satu- ration decompression (Hamilton, Maclnnis, Noble and Schreiner 1966) began with a large initial first stop of perhaps 25 fsw to set up a gradient, which may, in fact, produce bubbles. The fastest travel used in NOAA OPS was a six minute-per-foot ascent. As an additional precaution, the divers were required to ingest more fluids than usual and encouraged to move around frequently, although they were allowed to sleep during decompression. One reason for a greater rate of ascent than used by others, even though the half-times of the limiting compartments are similar, is the fact that a variable matrix was used which permits a faster rate of ascent for a given compartment at greater depths. Another factor to consider is that no oxygen breathing was used during any decompressions. There is no doubt that oxygen helps in decompression and is indispensible in treatment, but its benefits in clearing the slowest compartment may be limited. More studies are needed in order to resolve this issue. Results : Two 14-day, dry chamber saturation experiments were completed. Three subjects took part in each experiment which involved saturation at depths of 30, 60, 90 and 120 fsw. A total of 18 ascending and 15 descending excur- sions were- successfully completed constituting over 75 man-excursions. A technique was developed and utilized for extracting data from pre- vious dives, using a combination of computer and manual methods. Tables were computed using the new matrix and a decompression model involving 11 gas loading compartments was constructed in which the longest limiting half- time used was 480 minutes. This method produced successful tables on the first approach. Descending excursions included depths ranging from 85 to 300 fsw while ascents ranged from 30 to 65 fsw above the saturation depth. Excursion times ranged from eight minutes to six hours. The excursion profiles derived from the matrix are shown in Tables 15 and 16. The permissable excursion times shown in these tables are not exactly the same as those shown earlier on Tables 10 and 11 due to a general effort to be conservative in the publica- tion of recommended excursion profiles. The criteria and instructions for use of these tables are summarized below. More detailed information including examples of excursion dives may be found in the NOAA Diving Manual (1975) . 26 30 85 90 95 100 105 110 115 120 TABLE 15 No- decompress ion ascending excursion times (min) Habitat Depth fsw 10 Excursion Depth ( fsw ) 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 30 35 40 45 50 55 60 65 - 8 70 " " 75 - - 80 - 85 - 90 - 95 - 100 - 10- - 111) - - - ||=, - - uo - * No time limit 48 60 * * * * 37 48 60 * * * * 31 40 52 60 * * * * 24 31 40 52 60 * * * * 18 2 5 32 42 60 * * * * * 13 18 2 5 32 42 60 * * * * 7 13 18 25 32 42 60 * * * 8 14 20 27 34 44 60 * 8 14 20 27 34 44 60 9 15 21 28 36 47 60 9 15 21 28 36 47 60 16 23 30 37 48 60 * * * 10 16 2 3 30 37 48 60 * * 6 12 18 24 31 40 52 60 * 6 12 18 24 31 40 52 60 7 13 18 25 32 42 60 13 18 25 32 42 60 * * 7 13 18 25 32 42 60 * 7 13 18 25 32 42 60 TABLE 16 No-decompression descending excursion times (min) habitat Depth Excursion Depth (fsw) fsw 80 85 90 95 100 105 110 115 UP 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 I \n 235 24n 24S ;S0 350 267 156 • • 283 113 91 78 68 60 55 50 45 40 36 32 28 24 22 18 15 13 12 1 1 10 9 8 229 143 108 89 ?7 68 61 54 46 41 37 34 31 28 25 22 20 16 14 13 11 10 301 240 202 147 112 92 80 70 59 50 44 39 35 32 30 28 25 23 21 17 15 13 • 323 253 210 181 137 108 91 69 56 48 42 38 34 31 29 27 25 23 22 21 18 • * 350 267 219 187 164 140 86 64 53 45 40 36 33 30 28 26 24 22 21 20 • * • 314 245 203 174 153 137 86 63 52 45 40 36 32 30 27 25 24 22 21 • * • * 284 224 187 161 142 127 85 63 52 15 39 35 32 29 27 25 23 22 » » * » 315 236 191 162 145 128 111 85 63 51 44 39 35 32 29 27 25 23 » * * * • 279 213 174 148 129 114 103 84 62 5: 44 39 35 31 29 26 25 • » • • » • » •. 288 228 191 165 145 95 66 S3 45 40 35 32 29 27 • »•••»*♦••• 317 225 215 122 70 55 47 41 36 32 29 • •••••••••••• 328 265 225 95 66 54 46 40 36 » • • * » • • * 339 275 168 97 68 55 47 • • » • • « • » • • • • • '• • • 306 227 143 113 80 »**••***•••••♦•• 341 281 193 135 »»»•...»..»»•••• 354 308 262 9 9 12 11 16 14 19 18 20 19 21 19 22 20 23 21 25 23 27 25 32 29 41 37 62 52 109 93 174 129 294 257 347 303 10 9887766 12 11 10 9 9 8 8 7 16 14 13 12 11 10 9 6 18 17 15 13 12 11 10 9 18 17 17 15 13 12 11 10 19 18 17 16 16 14 12 11 20 19 18 17 16 15 14 13 22 20 19 18 17 16 16 15 23 22 20 19 18 17 16 15 27 25 23 22 22 19 18 17 33 30 28 26 24 23 21 20 46 40 37 33 31 28 26 25 72 59 50 44 40 36 33 31 107 77 62 53 46 41 38 35 176 132 83 65 5S 48 43 39 270 243 163 91 68 57 49 44 329 291 261 237 101 72 59 $1 * No time limit 27 Criteria for Computation 15 compartment decompression model, only 11 in use Half-times 5-480 min. Matrix 32/02. Inert gas: nitrogen only. Habitat gas composition: P0 2 = 0.2 atm, balance N 2 . Excursion gas: Air Excursion times rounded down to next minute. Validation Tested at Habitat depths 30, 60, 90, 120 fsw. Descending excursions tested: 85-300 fsw. Ascending excursions tested: 5-85 fsw. J- factors: Ascending: Some tests done with times increased by 25%: Times calculated for depth 5 fsw shallower than presented here. Descending: Times calculated for 5 fsw deeper; descent time was not included in bottom time for test dives (OPS II) . General Criteria A dive which loads slow tissue (half-time) compartments prejudices sub- sequent dives which are limited by these compartments. No-stop dives, how- ever, which are short, do not appreciably affect subsequent dives after a suitable time interval. A most important factor is the degree to which a given dive approaches the time limit for that depth; one which runs to the maximum allowable time will likely have more effect than one which does not. A four-hour period at storage depth should precede any repetitive dive. Descending Excursion A short descending excursion from saturation has little effect on sub- sequent descending dives, short or long (following the four-hour interval at storage depth) although it may have an effect on subsequent ascents. An 18-hour interval should be observed if limits were approached. Following a six- hour excursion 30 fsw below storage depth, a subsequent ascending excursion, if it approaches limits, should not take place sooner than 36-hours. Following a long excursion only a few feet below storage depth, subsequent: ascents should be safe if computed from the depth of the first excursion, rather than from storage depth. Begin timing excursions on departure from the habitat depth (bottom time includes descent time) . Descend at a moderate rate keeping in mind that a slow descent is preferred, but reduce bottom time. Return to storage depth at any desired rate up to 30 fpm. 28 Ascending Excursions Ascending excursions do not prejudice subsequent ascents or descents, but a four-hour interval is recommended. Begin timing ascents on arrival at excursion depth (bottom time does not include transit times) . Ascend at 10 to 20 fpm. Descend at 60 fpm or faster if desired. If bend symptoms are noted, return immediately to the storage depth. If return to storage depth is delayed by ear problems, it is preferable to discontinue descent (or even momentarily ascend a bit) and clear the ear, rather than incur ear damage in order to adhere strictly to the table. Repetitive Dives Excursion diving from saturation may be sensitive to recent diving his- tory. General rules cannot easily be given. Procedures conservative enough for all eventualities will make the practice inefficient in normal usage. For this reason, good judgement must be the controlling factor. The guide- lines given here are intended to provide the background necessary to enable good judgement to be used. Many factors change the conditions, such as cold, workloads, equipment used, experience, etc. All such factors must be con- sidered in any situation. The suggestions given here are based on computed gas loadings and have been given only limited testing. They may need to be modified in the light of relevant experience and are not intended to be precise. Biomedical Experiments The biomedical studies carried out were listed on Table 13. Generally speaking, no serious problems were encountered. The results of these experi- ments may be summarized as follows. 1. Nitrogen Washout OPS I - in saturated excursion dives three subjects were exposed to air pressure equivalent to 30 fsw for one week and performed subsequently two excursion dives to 150 fsw. Following decompression back to 30 fsw, the subjects breathed oxygen. Expired air was monitored in the three sub- jects in intervals with a mass spectrometer. In one subject who experienced mild knee pain, nitrogen bursts were found repeatedly in the expired air during decompression while breathing oxygen. The occasional nitrogen bursts were associated with sounds which might have been due to bubbles as detected with the Doppler ultrasound bubble detector. OPS II - Nitrogen bursts were detected on four occasions: Following decompression to 5 fsw from 60 fsw, two subjects had bends symptoms (itching, tingling) at the same time. One subject had symptoms following a decompres- sion from 120 fsw to 75 fsw. Another subject had the same symptoms follow- ing ascent from 120 fsw to 55 fsw. Both of these subjects also had bends symptoms such as itching during the time the nitrogen bursts occurred. 29 The finding of nitrogen bursts following a complete initial washout during oxygen breathing has been interpreted as nitrogen elimination from "silent" nitrogen bubbles, due to a nitrogen gradient set up by oxygen breath- ing. Lung function tests carried out on some of these subjects at normal atmospheric pressure did not reveal signs of any abnormalities, e.g., air trapping. 2. Doppler Ultrasonic Bubble Detection No unequivocal bubble sounds were heard during NOAA OPS I and II. In- terpretation is continuing to determine the nature of certain unidentified sounds. Spectral analysis of sounds is in progress. 3. Throughpass Ultrasound No attentuation was noted, although this technique has been successful in detecting bubble formation in animal decompression. That no bubbles were detected is not conclusive proof that none were there, however, other testing seems to corroborate the conclusion that few or no bubbles were present during decompression. 4. Bone Density In NOAA OPS I, one subject showed a clear reduction in bone density. A second subject showed a net decrease in density, but results were less definitive. The third subject showed no change in density. 5. Nitrogen Narcosis This study was intended to discover if there were deleterious neuro- behavioral effects of prolonged exposure to normoxic hyperbaric nitrogen and, if so, would such exposures provide resistance to narcosis during ex- cursions tc greater depths. At the beginning of saturation, performance equalled or exceeded that obtained in pre-saturation control tests, and it continued to improve slight- ly, but regularly, at saturation depths throughout the exposures. Evidently, the cognitive and perceptual-motor functions tested were not impaired by residence in the normoxic equivalents of 120 fsw, or less. Performance decre- ment during downward excursions varied directly with depth and inversely with duration of saturation exposure. On excursions, the divers generally described the narcosis as being about equivalent to an air dive to a depth equal to the excursion depth minus the saturation depth. A certain amount of this subjective judgement is undoubted- ly related to the feeling of both divers and investigators that this is what should be expected. This concept apparently does not hold true at all depths, since divers making excursions to 300 fsw from 120 fsw saturation were de- finitely and seriously affected. There was some adaptation but it was not sufficient to make 300-foot diving with air safe, even from a 120 fsw satura- 30 tion depth. On the other hand, at 250 fsw, divers were able to feel narcosis but felt safe. Even from 60 fsw, divers at 200 fsw felt narcosis but did not elicit symptoms as marked as they would have if making the same excur- sion from the surface. 6. Psychomotor and Cognitive Performance. Performance on all tests continued to approach a final level asymptotical- ly during exposure to habitat nitrogen partial pressure levels. Exposures to increased PN2 during excursions caused substantial depth-dependent re- sults in most performance scores. Despite the restrictions on sample size imposed by the nature of the study, subject illnesses unrelated to exposure parameters, and tracking test equipment malfunctions, the evidence for the trends just described is clear. Absence of performance impairment during residence at 120 fsw or less was most likely due to the narcotic potency at these depths being below the threshold of detection with the tests used. The progressive amelioration of narcotic effects during excursions with time under saturation was probably a result of a combination of factors, and not necessarily only adaptation. From a practical point of view it seems certain that duration of satura- tion exposure and frequency of excursion to a particular depth would invari- ably covary. Under those circumstances diving operations should be planned to capitalize on the dramatic decrease in performance impairment with suc- cessive excursions. A detailed description of the psychomotor program may be found in Schmidt, Moeller, Hamilton and Chattin (1974) . 7. Somatic Evoked Brain Responses (EBR) Somatic EBR showed occasional but not completely consistent pressure- dependent decrements on exposure of subjects to increased PN2. In most cases this decrement was reduced if the subject was adapted to nitrogen. A defi- nite reduction in control (e.g., not on excursions) EBR was seen in one sub- ject during adaptation at 90 fsw, as compared to pre- and post-dive values. EBR data agreed in general with observations on performance but is not con- ,.. sistent among all subjects. Moderate neurologic adaptation was indicated.' Reliability of somatic EBR for assessing diver response to narcosis was in- conclusive. 8. Visual Evoked Brain Response (VER) Some measures of the VER showed decrements commonly seen in narcosis, and some did not. Those that did show decrements also showed evidence of adaptation. The adaptation was not complete however since, the data at the end of the saturation period did not show a complete return to the levels measured at the surface. Analysis of the EEG's of the diver-subjects during the course of the two-week saturation period at depth revealed two changes. First, the frequency and the amplitude of alpha activity was reduced when compared to surface measures made prior to and following the saturation period. 31 Second, the amplitude of theta activity rose considerably for two of the men; there was no change in theta for the other three during the same time period. There is some preliminary evidence here for adaptation. The lack of decrement and hence adaptation in some subjects may be a reflection of their high level of experience in the diving environment. 9. Tolerance of Exposure No objective data yet available indicate in any way that the subjects had difficulty living in the hyperbaric nitrogen environment. However, all three subjects exposed to 120 fsw were feeling i]l during the course of that week. As mentioned earlier, one subject was so sick with influenza, he had to be removed from the experiment. The other two subjects were not feeling well, either. With three subjects known to be sick, it could not be determined how much effect the hyperbaric nitrogen had on their well-being. This experiment was deeper by 20 percent than the Tektite II test which disclosed essential- ly no difficulty (Lambertsen and Wright 1973) . The question remains as to whether some of the illness seen at 120 fsw in OPS II was due to the nitro- gen. Observations by both subjects and experimenters concluded that it was not, and that even deeper saturation could be safely carried out with nitro- gen. 10. Biochemistry Hematology - Plasma fibrinogen fluctuated during individual dives — ap- parently responding to pressure changes — and was notably elevated during the 120 fsw saturation. Platelets decreased at 90 fsw and increased at 120 fsw, i.e., they were lower during the second week of each experimental ser- ies after being slightly elevated during the first week. Decompression from saturation seemed to have produced increased platelet levels. A marked lengthening in whole blood clotting time (mea,sured only in OPS II) occurred during the 120 fsw saturation run and after final decompression. A possible rise in total RBC's or a change in normal hemoglobin-hematocrit relationship seemed to occur after final decompression in each series. Whd te blood cell counts showed considerable fluctuation. Serum chemistry - Sporadic increases were seen in activity of lactic dehydrogenase, creatine phosphokinase, glutamic-oxalacetic transaminase and alkaline phosphatase which frequently could be related to major changes in environmental pressure. Urine - Total urine protein output showed marked fluctuations, the peaks of which also appeared to follow major changes in pressure. Peaks of excre- tion of calcium, phosphate, osmolarity, urea nitrogen, steroid hormones, and to a somewhat lesser extent, creatinine, coincide with the 60', 90* , and 120' series of pressure exposures. Hydroxy-proline excretion (an index of bone metabolism) appeared to increase in the higher pressure exposures. 32 11. Dental-Oral Tissue Response During OPS I, small erythematous areas were noted on the palate of two divers after decompression. During OPS II, the same type of response was observed after decompression from bounce dives to 200 and 250 fsw. Some evidence of oral hygiene deterioration was manifested in "canker sore" formu- lation. Visual observation and symptomatic suggestion of palatal response to decompression suggests an additional source for monitoring tissue reflections of gaseous saturation. The methodology for quantitating such phenomena cur- rently is being refined. 12. Aerobiology Since the total viable particle counts were essentially unchanged during OPS I, the sampling time was extended, during OPS II, producing interesting profiles. The density of bacteria-laden parti cula seemed to parallel ac- tivity patterns relative to illness and foreign intrusion. Viable particula increased markedly on days immediately subsequent to viral illness of one subject and to entry of a new subject and to visitations by guests. 13. Salivary Microbiology Logistic problems during OPS I made conclusions concerning assays of fresh specimens highly speculative. All samples from OPS II were quick- frozen on site and then transported for processing. The following results relate primarily to data obtained during OPS II. While overall salivary bacterial counts remained essentially constant throughout baseline, experimental and post-dive periods, specific organismal groups showed considerable variation. One result of habitat living was manifested by increased growth on EMB media. Variations in salivary staphy- lococci, streptococci and lactobacilli seemed to parallel oro-pharyngeal involvement in illnesses observed in three subjects. Bacterial counts subsequent to thawing of frozen specimens were gen- erally lower than those of corresponding fresh specimens, however the degree of reduction was usually no more than one lOg-^g per ml. The salivary micro- flora appeared to reflect environmental adaptation and oro-pharyngeal ill- ness patterns. 14.. Immunology and Ecology Divers provided nasal washings daily, which were frozen and analyzed for immunoglobulins. Concomitant serum immunoglobulin analysis was performed. Analytical emphasis was placed on quantitation of the serum and secretory immunoglobulins, transfer proteins and protease inhibitor levels in pre-dive, dive, and post-dive periods. Instrumentation difficulties have prevented completion of these analyses. 33 15. Psychology (NOAA OPS I only.) Some moderately intense signs of anxiety and ten- sion were observed in one subject. Information was obtained pertaining to the correlation between pain tolerance and other subjective symptoms as a function of pressure variation, particularly during excursions. There was no substantive evidence that emotional stresses were cumulative under these environmental conditions. The changes in subjective indices of stress were small in OPS I and did not appear to covary with pressure fluctuation. Therefore the program was not continued in OPS II. 16. Longitudinal Health Study The NOAA OPS subjects participated in a longitudinal health study, a continuing medical survey of Navy officers and men, and a few civilians, engaged in diving and submarine activities. The intent is to learn about special medical factors affecting this group. Participants are given a thorough medical examination at the beginning and periodic examinations sub- sequently. No general medical findings were encountered in these examina- tions that could be related to the exposure to the nitrogen environment. Conclusions : In brief, the NOAA OPS program demonstrated the viability of living at depths up to 120 fsw in a normoxic atmosphere and the techniques of making vertical excursions on air to depths ranging from 5 to 300 fsw. The program paved the way for using air much more extensively than heretofore thought possible. In addition, it spawned several subsequent programs which were carried out both in the laboratory and in the open sea. Several of these programs are described in this report. IV- B SHAD (Shallow Habitat Air Diving) _ Introduction : The SHAD program was initiated in January 1972 at the Naval Submarine Medical Research Laboratory (NSMRL) to further evaluate the biomedical feasi- bility of long-term residence in a compressed air environment. Vertical excursions were carried out to establish profiles that could be utilized by the air-saturated working diver and to obtain information relating to emergency conditions that might be encountered. The fundamental difference between this program and NOAA OPS is that the SHAD divers breathed air both as a storage and excursion gas. Air satu- ration diving by its very nature embraces potential limitations related to oxygen toxicity, nitrogen narcosis, and gas density. As already described, previous studies have revealed the nature of some of these problems. Experi- ments at the storage depths planned for the SHAD program were conducted 34 first using a model animal system without evidence of adverse effects. As a result of these observations plus those obtained during a three-day manned air exposure at 50 fsw, the SHAD program was designed to place men in a compressed air environment at 50 and 60 fsw for a maximum of 30 days. A no-decompression excursion dive regimen permitting excursions between 5 and 250 fsw was constructed on a mathematical basis similar to that employed in the NOAA OPS I and II. Purpose ; SHAD was designed principally as a biomedical feasibility program. As such, a multi-disciplinary scientific effort was undertaken to evaluate the divers both for obvious physiological limitations and such subtle physi- ological variances as could be anticipated. Emphasis was on pulmonary physi- ology, visual physiology, psychophysiology, hematology, and the chemistry and biochemistry of both urine and blood. Numerous additional biomedical studies also were completed. Location: Naval Submarine Medical Research Laboratory, (NSMRL) , New London, Connecticut Dates: SHAD I - October 1973 SHAD II - May 1974 SHAD III - December 1974 Duration: SHAD I - 29.5 days SHAD 11-28 days SHAD III - 9 days Saturation Depth : SHAD 1-50 feet SHAD II - 60 feet SHAD III - 50 feet Breathing Gas: Storage - Air Excursions - Air Subjects: SHAD 1-2 SHAD II - 2 SHAD III - 3 Facility : The hyperbaric complex at NSMRL was utilized for the SHAD program. The same chamber complex was used in Project Genesis, the preliminary pro- ject that evolved into the US Navy's SEALAB program (Bond 1970) and in Tektite I, a long term man-in-the-sea project that employed a nitrogen/oxygen breath- ing mixture (Pauli and Cole 1970) . 35 The principal hyperbaric chamber for SHAD was nine feet in diameter, with an inner lock 15 feet long and an outer lock nine feet long. Independ- ent life support systems for controlling carbon dioxide, temperature and humidity were available in each lock. A small item transfer lock was avail- able in the inner lock. Independent lighting, as well as visual and audio communication systems were present in each lock. Manual, chamber-mounted controls were used to maintain a constant storage depth (±0.5 fsw) and to add oxygen for maintenance of the required oxygen partial pressure. Depth, temperature, humidity, carbon dioxide, carbon monoxide, and oxygen levels were manually recorded from redundant monitoring systems, with trace gas impurities being monitored by gas chromatographic techniques. Sanitary fa- cilities were available in the outer lock. Biomedical equipment was either retained inside the complex or transferred into the chamber when required. An immersion tank (wet pot) was not available. Mask-supplied contingency gases were available at all times. A second, double-lock chamber was available for emergencies. The pro- jected available surface interval for the saturated diver would have permitted safe transfer into this second chamber as well as to other chamber facilities accessable within the surface interval. Divers ; All subjects taking part in SHAD had volunteered and were qualified US Navy divers under 30 years of age. Procedure ; Four manned air saturation dives were carried out as part of the SHAD program. The general characteristics of these dives are shown in Table 17. Each of the nine saturated divers was given a complete physical examination and baseline biomedical tests prior to the dive. In addition, each diver was cross-trained in the data aquisition techniques used during the experi- ments . The biomedical tests carried out during the SHAD series are shown in Table 18. With the exception of pulmonary function evaluations and human factors evaluations on excursion dive days, most data collection occurred on a one- or two- day cycle. Pulmonary function evaluations utilizing a wedge spirometer were made about four times each day during the initial days of each dive but on a decreasing frequency as the dive progressed. As time permitted, pulmonary function evaluations also were made during each de- scending excursion. Human factors evaluations were conducted prior to and during ea.ch excursion to 100 fsw or greater. A pre-cordial Doppler detector system was used during every ascent to determine the presence or absence of circulating gas bubbles. Consistent with the program goals, a medical officer entered the chamber each morning and examined the divers. The re- sults of the biomedical monitoring and physical examinations were used to determine whether the dive would continue. 36 TABLE 17 General characteristics of SHAD dives* Dive Date Storage Depth (fsw) No. of Divers Duration, Total (days) Mean Oxygen Level (AtA) Mean Carbon Dioxide Level 3 ' Mean Temperature (°F) a Mean Relative Humidity (%) No. Ascending Excursions No. Descending Excursions Decompression Time (min) Decompression Sickness Pre SHAD I SHAD I SHAD II SHAD III Sept 1973 Oct 1973 Mar 1974 Dec 1974 50 50 60 50 2 2 2 3 2.25 29.5 28 9 0.51 0.51 0.57 0.61 0.111 0.092 0.099 0.172 78.0 76.8 73.0 75.8 76.0 62 52 74.7 4 4 14 11 6 57.4 810 1680 2778 c yes (2) No No yes (1) Compressed air with oxygen make-up was the only gas employed a Storage depth values except for SHAD III , where a weighted mean reflective of the eight hours per excursion day spent at 100 fsw, was employed per cent, surface equivalent c includes treatment regimen with 100% oxygen and recompression ( ) indicates number of divers affected 37 TABLE 18 Principal biomedical evaluations in the SHAD program Pulmonary Pulmonary function (FVC, FEV, FEV 2 , MEFR, MIFR, MW) Gas exchange (BTPS, BPM, V t/ Paco 2 , Vco 2/ RQ) [I] Inspired/expired gas analysis Excercise tolerance Carbon dioxide tolerance Mixed venous blood gases Vision Visual evoked response EEG Fundus photography Night vision sensitivity Visual fields and acuity Color vision [I] General Physical Parameters General physical examination Weight Rectal temperature Blood pressures EKG (scalar and vector) Urine Human Factors Adaptive tracking Mental arithmetic Short term memory Sentence comprehension Pattern recognition Audiograms Ear conduction [I] Bone density [III] Precordial doppler a Long bone radiographs 24 hour volume, Ca, P04, Na, K, hydroxy proline, creatinine, urea, 17-hydroxysteroids, osmolarity, protein, ketone, sugar, blood, micro- scopic cells. Blood RBC, WBC, and differential, PCV, Hb, MCV, MCH, MCHC, reticulocytes, platelets, Ca ionic and total, Na, K, CI, osmolarity, LDH, SGPT, SGOT, CPK, alkaline phosphatase, bilirubin, creatinine, glucose, BUN, protein total and fractions, albumin, haptoglobin, T3 , T^ , T7 , and lipoproteins on SHAD I only. Oral Physiology Parotid fluid (stimulated) Microbiology Aerobacteriology , skin, oral, nasal, potable water, mechanical environment [ ] Indicates SHAD dive in which a particular study was not employed a employed in pre-SHAD I 38 A typical day began at 0600 and ended at 2300. In SHAD I and II peri- odic two-hour rest periods were scheduled each morning and afternoon. Ex- cursion dives and lengthy testing regimens (for example, exerci.se tolerance) interrupted the rest periods. In SHAD III, the eight-hour excursions included a brief rest period. Four-hour rest and recreational periods were scheduled on most evenings. All excursions were conducted without decompression prior to returning to the storage depth. The individual excursion profiles, surface intervals, and decompression times are shown in Tables 19 through 22. TABLE 19 Pre-SHAD I dive profile Elapsed Time at Dive Time Depth Depth Time of Day Day (min) Event (fswg) (min) hr :min :sec Comment 1 0.0 L 12:35:00 1 1.7 R 50 3 2641.7 L 50 2640 08:48:40 Travel 6 min/ft 3 2821.7 L 20 Travel 15 min/ft 3 2971.7 L 10 Travel 20 min/ft 3 3071.7 L 5 Travel 30 min/ft 3 3215.4 R 18:22:20 * Total time at depth: 1 day, ; 20 hrs , 12 min. Total decompression time: 9 hrs, 33 min, 40 sec, * Both divers exited chamber with minor knee pains. 3 3433.1 L 3 3435.1 R 60 3 3510.1 L 60 3 3540.1 R 30 4 3690.1 L 30 4 3720.3 R 22:00:00 22:02:00 23:17:00 23:47:00 02:17:00 02:47:13 Treatment table 6.** ** ** ** ** ** Intermittent 100% oxygen, air breathing as per table instructions. Both divers exited chamber with mild residual pain and difficult respiration. The pre-SHAD I decompression regimen was accomplished through sequential pressure decreases of three inches of sea water while the compression regimen for the remaining three dives was accomplished by sequential pressure decreases of six inches of sea water (simulated) . The first dive in this series, pre- SHAD I, was designed primarily as a chamber habitability evaluation and did not involve as extensive a biomedical evaluation program as was subsequently employed. 39 TABLE 20 SHAD I dive profile Elapsed Time at Dive Time Depth Depth Day (min) Event (fswg) (min) Time of Day hr:min:sec Comment 1 1 9 9 9 9 12 12 12 12 14 14 14 14 16 16 16 16 17 17 17 17 19 19 19 19 20 20 20 20 21 21 21 21 22 22 22 22 23 23 23 23 0.0 1.5 11432.9 11435.5 11453.5 11458.6 15754 15757.2 15763.1 15769.4 18618 18621.2 18627.1 18633.3 21807.5 21809.6 21815.6 21821.9 22951.5 22954.0 22972.0 22977.2 26126.2 26128.8 26147.5 26152.7 28051.2 28058.8 28076.8 28082.6 28723.2 28725.1 28767.9 28771.4 30155.5 30158.4 30189.1 30190.1 31890.6 31892.3 31935.3 31938.7 L R L R L R L R L R L R L R L R L R L R L R L R L R L R L R L R L R L R L R L R L R 50 50 200 200 50 50 235 235 50 50 235 235 50 50 235 235 50 50 200 200 50 50 200 200 50 50 200 200 50 50 150 150 50 50 5 5 50 50 150 150 50 18.0 5.9 5.9 6.0 18.0 18.7 18.0 42,8 30.7 43.0 11:39:20 10:11:16 10:36:54 10:16:22 10:31:46 10:12:24 10:30:42 15:06:51 15:21:15 10:10:53 10:36:35 15:05:30 15:32:30 23:10:32 23:41:56 10:22:33 11:10:45 10:14:54 10:49:30 15:09:54 15:58:00 S.I. = 18:49:38 S.I. = 10:40:37 S,I. = 23:04:09 S.I, = 28:20:14 40 TABLE 20 (cont.) SHAD I dive profile Elapsed Time at Dive Time Depth Depth Time of Day Day (min) Event (fswg) (min) hr :min:sec Comment 25 34770.6 L 50 15:09:55 25 34772.6 R 15 25 34829.6 L 15 57.0 25 34830.2 R 50 16:09:31 25 35248.4 L 50 23:07:45 S.I. = 6:58:14 25 35250.1 R 150 25 35298.9 L 150 48.8 25 35303.2 R 50 Day 26 00:02:33 26 35917.3 L 50 10:16:40 S.I. = 10:14:07 26 35919.0 R 150 26 35962.0 L 150 43.0 26 35965.4 R 50 11:02:13 26 36211.9 L 50 15:08:44 S.I. = 4:06:31 26 36212.3 R 75 26 36272.3 L 75 60.0 26 36273.5 R 50 16:10:20 27 37358.1 L 50 10:14:54 S.I. = 18:04:34 27 37359.0 R 100 27 37417.3 L 100 58.3 27 37419.1 R 50 11:15:54 27 38138.0 L 50 23:14:50 S.I. = 11:58:56 27 38139.8 R 15 27 38194.0 L 15 54.2 27 38195.3 R 50 Day 28 00:12:08 28 38869.2 L 50 11:25:03 S.I. = 11:13:55 28 38872.1 R 5 28 38902.7 L 5 30.6 28 38903.5 R 50 11:59:21 28 39150.0 L 50 16:05:50 S.I. = 4:06:29 28 39152.6 R 200 28 39170.6 L 200 18.0 28 39175.6 R 50 16:31:26 30 41610.2 L 50 28 days 21:30:12 09:06:00 Start decompression Travel rate 6 min/fsw 30 41700.2 L 35 Travel rate 15 min/fsw 30 42075.2 L 10 Travel rate 33 min/fsw 30 42240.2 L 5 Travel rate 36 min/fsw 30 42420.2 R 22:36:00 Total time at depth : 28 days, 21 hrs, 30 min, 12 sec. Total dec :ompre jssion time: 13 hrs . 30 min. 41 TABLE 21 SHAD II dive profile Elapsed Time at Dive Time Depth Depth Day (min) Event (fswg) (min) Time of Day hr:min:sec Comment 1 0.0 L 1 2.3 R 8 9852.2 L 8 9853.4 R 8 9912.9 L 8 9915.2 R' 12 15601.0 L 12 15601.8 R 12 15661.8 L 12 15663.3 R 14 18780.0 L 14 18780.9 R 14 18840.7 L 14 18841.9 R 16 21360.0 L 16 21361.6 R 16 21421.5 L 16 21424.5 R 17 23235.0 L 17 23238.4 R 17 23258. 4 L 17 23263.1 R 19 25695.0 L 19 25698.3 R 19 25704.1 L 19 25710.6 R 20 27120.0 L 20 27123.6 R 20 27144.9 L 20 27145.8 R 22 30010.0 L 22 30012.3 R 22 30043.5 L 22 30044.3 R 22 30 300.0 L 22 30302.6 R 22 30322.5 L 22 30327.3 R 23 31440.0 L 23 31441.5 R 23 31501.5 L 23 31504.5 R 23 31739.9 L 60 60 100 100 60 60 100 100 60 60 100 100 60 60 150 150 60 60 200 200 60 60 250 250 60 60 5 5 60 60 15 15 60 60 200 200 60 60 150 150 60 60 59.5 60.0 59.8 59.9 20.0 5.8 21.3 31.2 19.9 60.0 14:00:00 10:12:13 11:15:13 10:01:00 11:03:13 15:00:00 16:01:55 10:00:00 11:04:31 17:15:00 17:43:16 10:15:00 10:30:40 10:00:00 10:25:46 10:10:00 10:44:21 15:00:00 15:27:24 10:00:00 11:04:33 15:00:00 S.I. = 23:29:10 S.I. = 4:15:39 S.I. = 18:32:36 S.I. = 3:55:27 42 TABLE 21 (cont.) SHAD II dive profile Elapsed Time at Dive Time Depth Depth Time of Day Day (min) Event (fswg) (min) hr :min:sec Comment 23 31740.6 R 23 31800.6 L 23 31802.0 R 24 32885.4 L 24 32886.1 R 24 32946.0 L 24 32947.3 R 24 33179.8 L 24 33182.0 R 24 33213.3 L 24 33214.0 R 25 34320.0 L 25 34323.4 R 25 34344.9 L 25 34345.9 R 25 35100.0 L 25 35102.3 R 25 35122.3 L 25 35126.9 R 28 38520.0 L 28 38670.5 L 28 39069.0 L 28 39300.0 R 29 39789.0 L 29 4002.0 L 29 40200.1 R 100 100 60 60 100 100 60 60 15 15 60 60 5 5 60 60 200 200 60 60 45 19 12 12 5 60.0 59.9 31.3 21.5 20.0 26 days 18 hrs. 489.0 16:02:06 10:05:31 11:07:30 15:00:00 15:34:17 10:00:00 10:25:53 23:00:00 08:00:00 21:00:00 05:09:00 12:00:07 S.I. = 18:03:25 S.I. 3:52:30 S.I. = 18:25:43 S.I. = 12:34:07 Start decompression Travel rate 10 min/ft Travel rate 15 min/ft Travel rate 33 min/ft Sleep hold Travel rate 33 min/ft Travel rate 36 min/ft Total time at depth: 26 days, 18 hrs. Total decompression time: 1 day, 4 hrs, 07 sec. 43 TABLE 22 SHAD III dive profile Elapsed Dive Time Depth Day (min) Event (fswg) Time at Depth (min) Time of Day hr :min:sec Comment 1 0.0 L 1 1.7 R 2 1403.0 L 2 1404.8 R 2 1883.0 L 2 1908.0 R 3 2838.0 L 3 2839.5 R 3 3317.9 L 3 3337.9 R 4 4278.0 L 4 4279.6 R 4 4758.0 L 4 4773.0 R 5 5718.0 L 5 5719.7 R 5 6197.9 L 5 6208.5 R 6 7158.1 L 6 7159.6 R 6 7638.0 L 6 7641.0 R 7 8598.0 L 7 8599.8 R 7 9078.0 L 7 9079.7 R 8 10020.0 L 8 10170.0 L 8 10395.0 L 8 10537.2 8 10553.6 L 10554.2 R 8 10580.0 8 10590.0 8 10595.0 8 10605.0 8 10610.0 8 10620.0 8 10625.0 8 10635.0 8 10658.0 L 8 10848.2 R 50 50 100 100 50 50 100 100 50 50 100 100 50 50 100 100 50 50 100 100 50 50 100 100 50 50 35 20 18 18 28 28 28 28 28 28 28 28 28 28 24 478.2 478.4 478.4 478.2 478.4 478.2 6 days 2 3 hrs 10:42:00 10:05:02 18:30:00 10:00:03 18:20:00 10:00:00 18:15:03 10:00:00 18 : 10 : 34 10:00:05 18:05:03 10:00:01 18:01:43 09:42:00 Travel at 2 ft/min S.I. = 15:30:03 Travel at 2.5 ft/min S.I. = 15:40:00 Travel at 3.3 ft/min S.I. = 15:44:57 Travel at 5 ft/min S.I. = 15:49:31 Travel at 16.7 ft/min S.I. = 15:54:58 Travel at 30 ft/min Start decompression Travel at 10 min/ft Travel at 15 min/ft Travel at 54 min/ft Holding 18:35:36 PP pain only bends 19:02:00 On 2 19:12:03 Off o 2 On 2 Off o 2 19;17:00 19:27:00 19:32:00 On 2 19:42:00 Off o 2 19:47:00 On 2 19:57:00 Off o 2 20:20:00 Travel at 54 min/ft 23:30:11 Sleep hold 44 TABLE 22 (cont.) SHAD III dive profile Dive Day Elapsed Time (min) Event Depth (fswg) Time at Depth (min) Time of Day hr :min:sec Comment 9 9 10 10 11239.0 12183.0 12723.0 12798.3 24 6 6 06:00:00 21:45:00 06:45:00 08:00:20 Travel at 54 min/ft Sleep hold Travel at 12.5 min/ft Total time at depth: 6 days, 23 hrs. Total decompression time: 1 day, 22 hrs, 18 min, 20 sec. The decompression procedures used in the SHAD program were based on those used in NOAA OPS I and II, with modifications for the air environment. The decompression schedules employed in SHAD II and III were derived in part, at the NSMRL and may be seen in Tables 21 and 22 respectively. Results : A total of 3,516 man-hours of air saturation were safely completed. Eight ascending and 31 descending excursions were conducted between the depths of 5 and 250 feet. Significant, environmentally-related medical changes were not observed during the saturation periods. A minor external otitis was observed during SHAD I and II, which responded to routine treatment. The health problems, both medical and dental, that did occur were typical of those normally en- countered at the surface. Significant forced vital capacity reductions were not observed during pre-SHAD I, SHAD I, or SHAD II. During SHAD III, however, one diver had a reduction in forced vital capacity following the fourth, fifth and sixth excursion dives. Near-baseline level was reached during the intervening residence periods at 50 fsw. The maximum reduction in vital capacity was 9.6%. Predicated on current procedures, the cumulative oxygen dose of SHAD II exceeded the limits required to produce a 10% vital capacity decrease by more than 800%. Three of the nine divers had symptoms of decompression sickness. In each case, a combination of recompression and pure oxygen breathing was em- ployed in the therapeutic treatment and on each occasion, changes indicative of oxygen toxicity were observed. The US Navy Standard Treatment Table 6 was used for the pre-SHAD I divers resulting in symptoms of both pre-convulsive 45 central nervous system disorder and pulmonary toxicity. After using the treatment procedure for SHAD III (see Table 22) , a 24% decrease in forced vital capacity was measured in one diver. However, it returned to the base- line level during the remainder of the decompression regimen. Although there were no symptoms of oxygen toxicity at storage depth, the consistent observation of such symptoms and/or related changes during bends treatment cannot be overlooked and must be taken into account when planning air saturation missions. These changes suggest that some altera- tion occurred in the divers that precluded their ability to accommodate to what would normally be a routine treatment procedure employing 100% oxy- gen. When such an alteration occurred, it did so within two days (pre-SHAD I) and was not observable with the techniques employed in the SHAD program. Ascending excursions involving a maximum pressure differential of 1.67 atm. (55 fsw) were evaluated. They were used in both non-repetitive and repetitive combinations with descending excursions. No symptoms of decom- pression sickness occurred except for skin itching that is commonly found in dry chamber dives. Circulating gas bubbles were occasionally detected at the end of the excursion periods. These did not occur, however, after the repetitive descending excursions that followed the ascending excursions. Measurements indicated significant reductions in red blood cell mass in both SHAD I and II. The decline, initially noted on about the 10th day, continued until the dive was completed. Maximum reductions of red blood cell mass of 12.5% in SHAD I and 19.3% in SHAD II were observed during the period immediately after surfacing, but subsequently returned to baseline levels in each diver. No significant alterations were determined in either the blood or urine chemistries or biochemistries, although a total data analysis has not been completed. Visual fields, visual acuity, and EEC did not exhibit significant changes in SHAD I or II (Kinney et at. 1974) . Retinal arteries and veins constricted during the first week of each dive and remained so throughout each exposure. Visual evoked responses and various tests in the human factors test battery demonstrated the anticipated changes during the deeper excursion dives of SHAD I and II. Data analysis for SHAD III has not been completed. While narcosis was evident during the deeper excursions, it did not limit the diver's effectiveness with regard to the completion of assigned tasks. The results of the human factors test battery suggested some accom- modation to narcosis during the deeper excursions as the dives progressed. The utilization of an arbitrary 60-minute excursion time limit in SHAD I and II precluded the testing of maximum excursion times at depths equal to or less than 100 fsw. SHAD III, however, clearly demostrated the possi- bility of a full eight-hour working day at a depth of 100 fsw, operating from a storage depth of 50 fsw. Data analysis has not been completed with respect to the general applicability of the repetitive dive sequences used in the SHAD program. 46 Summary ; The SHAD program has further documented the feasibility of mans' resi- dence in air at 50 and 60 fsw for extended periods as well as the availa- bility of an air excursion matrix ranging from 5 to 250 fsw. Significant insight into the ranges of oxygen partial pressures to which man can accom- modate has also been acquired. The higher oxygen partial pressures experi- enced while at storage depth, however, seem to be a potential hazard if oxygen treatment is necessary. Further work needs to be done to better understand and reduce this hazard. The SHAD results have provided additional information which should en- hance the utilization of air saturation procedures in a multitude of diving and tunneling endeavors. IV-C SCORE (Scientific Cooperative Operational Research Expedition) PHASE I Introduction : The conclusions of the NOAA OPS I and II experiments indicated that residence in a normoxic nitrogen environment at increased ambient pressures for periods of one week does not appear to cause a significant degradation of cognitive and psychomotor function. On the contrary, there seemed to be an adaptation to nitrogen narcosis which extended to the deeper excur- sion dives. Cognitive and psychomotor performance during compressed air excursions from saturation was significantly improved over performance dur- ing dives to the same depths from the surface. The SHAD program further verified these conclusions using divers saturated in an air environment at depths of 50 and 60 fsw. In each of these programs, however, vertical excursions were made such that decompression was not required prior to re- turning to the storage depth. In order to increase useful bottom time as well as further verifying these earlier studies, excursion profiles were developed which require de- compression prior to returning to storage depth. Evaluation of these new excursion profiles was carried out in the laboratory and in the open-sea along with further tests to determine whether there was any impairment of cognitive, psychomotor, or physiological functions. Purpose : To saturate divers on air at a depth of 60 fsw and to make excursions to depths of 200, 250 and 300 fsw for periods of one hour using profiles which include decompression prior to returning to the 60-foot storage depth. 47 Location: F. G. Hall Laboratory for Environmental Research, Duke University, Durham, North Carolina Date: January 27 - February 10, IS 7 5 Duration: 14 days (5 days saturation) Saturation Depth: 60 feet Breathing Gas: Storage - air; excursions - air Subjects: 8 Facility : Duke University Laboratory The core facility, a multichamber environmental complex with supporting laboratory space, occupies a three-story area of the Medical Center (Fig. 4). For these experiments the hyperbaric part of the complex used was a cylindrical chamber 36 feet in length, with an internal diameter of 10 feet 6 inches, divided into two compartments, spherical lock, and a treatment compartment (marked C in Fig. 4) . The wet chamber, D, is immediately be- neath the sphere, C. All compartments have multiple windows, access plates for penetrations of biomedical sensors, communications systems, and independent capabilities for pressurization and ventilation. The five compartments on the ground floor level have internal gas circulation systems for control of humidity and temperature. These systems have been modified in the deep diving com- plex for removal of carbon dioxide as well. Fire control systems are based on inundation with water and pass- through locks for introduction or removal of materials. The five compartments on the ground floor are pressurized, ventilated, and controlled in all respects from a console. Controls are automatic pneumatic, manual pneumatic, and manual. Communication between console operators and occupants of the chambers utilizes headset-microphone systems, a microphone-loud speaker system, television and chamber windows. Divers : Two teams were selected of four men each, with a fifth as a standby in the event of illness. One experienced Duke Chamber diver was selected from each group to make dives in the wet chamber. All divers were exper- ienced and. ranged in ace from 26-40. Complete medical examinations and long- bone x-rays, respiratory function tests, EEG, EKG, auditory, vestibular and visual tests were made to ensure the health and safety of the subjects. Pro c edure : Baseline data were collected from all subjects for one week prior to the saturation di.ve. These data included: 48 o Performance tests 1) Arithmetic test. Two figure by one figure multiplication (e.g. 6 68x9 = ) (testing time = 1 min) . 2) Ball bearing test. Picking up ball bearings with tweezers and plac- ing them in a tube of the same diameter (testing time = 1 min) . 3) Signs and symptoms questionnaire. 4) Digit span forward. Numbers are read out which the subject has to repeat forwards. The numbers increase in length one at a time until the subiect makes an error (testing time = 3 min) . 5) Time estimation. The subject is required to estimate the passage of randomly selected times ranging from 6 to 24 seconds (testing time = 3 min) . F G. HALL LABORATORY ENVIRONMENTAL CHAMBER COMPLEX One Torr - 7.8 Ato One Ata -7.8Ata One Torr- 31.3 Ata One Ata -31 3 Ata (wet pot) Instrumentation Platform Operational Level Mezzanine Machinery Level Carrel Space Detailed areas depict related laboratories and offices. Fig. 4. Duke University experimental diving facility used for SCORE (Phase I) 49 Hematology and Blood Chemistry The reduction of circulating platelet count in divers decompressed from a hyperbaric environment has been reported by several investigators and was discussed in a recent review (Philp 1974) . It has since been conf irmed by other investigators (Valeri, Feingold, Zuroulis r Sphar, and Adams 1974). Information concerning this phenomenon as it relates to saturation diving is, however, scanty. The suggestion has been made, based on the results of animal experiments, that platelets adhere to, and aggregate around, in- travascular bubbles and subsequently disappear from the circulation either because of a shortened life-span or because they become trapped as minute thrombi in the microcirculation. In order to better understand this phe- nomena further, studies were made during the SCORE program. Blood Samples Twenty-ml blood samples from a forearm vein occluded with a wide tourni- quet were collected into disposable plastic syringes using disposable 20- gauge needles. The blood samples were immediately distributed into test tubes containing the appropriate anticoagulant. To minimize blood loss, not all divers were sampled on all occasions. All ten subjects were sam- pled on Day 1 and before the 200-f sw bounce dive (Day 2) ; five after the 250-fsw bounce dive (Day 3); four before the 300-fsw bounce dive (Day 4) ; ten before the saturation dive (Day 6) ; four shortly after completion of the last (300-fsw) excursion dive; four after another 24 hours (Day 10) ; and eight after surfacing from the excursion dive (Day 11) . Seven were sampled 24 hours later and six were sampled 48 hours later. Four of these six had participated in a final 300-fsw bounce dive the previous day. Hematology Red-cell counts, white-cell counts, hemoglobin concentration, packed- cell volume (PCV) and corrected sedimentation rate (CSR) were conducted by the diagnostic service of Duke University Medical Center; all counts were performed electronically. For purposes of comparison, red blood cells were counted in a hemocytometer with a microscope. Blood Chemistry The activities of lactic dehydrogenase (LDH) , creatine phosphokinase (CPK) , alkaline phosphatase (ALP) , glutamic-oxaloacetic transaminase (GOT) and glumatic-pyruvic transminase (GPT) were measured in plasma by the meth- ods described previously (Philp, Freeman, Francey, and Ackles 1974). Bubble Detection Additional data were obtained using a Doppler bubble detector with an over-the-heart sensor during decompression following excursions. 50 The subjects started the performance tests at the surface and continued regular and frequent practice to reduce the learning effect as far as pos- sible within the time available. Control studies were performed at depths of 200, 250, and 300 fsw during which the subjects descended from the surface and remained for 15 minutes while taking performance tests. Further control data were obtained upon reaching the 60- foot saturation depth. During all excursions, performance tests were administered and blood samples obtained. A 300-foot dive was conducted the day following the decompression to surface as a post-dive control. Experiments to test for possible adaptation to increased nitrogen partial pressures were run prior to and post dive as well as at the satura- tion depth and during excursions. Three excursion profiles were provided by Tarrytown Labs to Duke Uni- versity for testing. As a safety precaution, an additional five profiles (abort tables), with shorter bottom times, also were provided. The following criteria were used in the computation of all profiles: 1. Breathing gas: air (20 percent oxygen, balance nitrogen). 2. Saturation level: 65 fsw, divers returning to 60 fsw. 3. Instantaneous compression to excursion depth. 4. Excursion calculated at a depth 5 fsw greater than that listed for the profile; i.e., 255 fsw for 250 fsw excursion. 5. Initial ascent rate of 30 fsw per minute. 6. Rate of ascent between stops of 10 fsw per minute. 7. Decompression stop time rounded to next whole minute. 8. All calculations based on the "smoothed" constraint matrix. Table 23 shows the excursion decompression profiles provided. The rationale used for the selection of a saturation level of 65 fsw was that these tables would be used in the field where repetitive diving over the course of several days would be done without the backup of a com- puter or residual nitrogen tables. The return to 60 fsw was dictated by the depth of the habitat. In using a five fsw greater excursion depth the same reasoning was used as in the original work; that is, all depth gauges are not equal, so it is better to allow for possible error. The decompression schedule used for return to the surface is shown in Table 24. This table is based on the assumption that the compartment with the longest half-time is the controlling compartment for a saturation de- 51 TABLE 23 Excursion decompression profiles for a 60-fsw habitat Excursion Excursion Stop time (min) / Stop depth (fsw) Total Depth Time Ascent (fsw) (min) 150 140 130 120 110 100 90 80 70 Time* 30 1 3 3 9 200 60 5 3 4 3 19 30 | 3 7 6 4 3 22 250 60 9 9 45 15 1 4 3 18 30 l| 7 6 4 4 34 300 2- 3 3 7 7 3 45 9 10 55 60 2 3 3 3 5 10 10 9 44 103 * Ascent time to first stop was 30 fsw/min Ascent time between stops was 10 fsw/min compression. An initial ascent at six minutes per fsw was scheduled to the depth at which the calculated inert gas partial pressure loading for the compartment reached the value specified in the constraint matrix for that depth. Decompression then proceeded at the rate required to clear the next 1/4 fsw shallower. The rate was approximated over one fsw inter- vals and in time blocks of whole minutes per fsw. Air was the only breath- ing gas used for this decompression. The saturation at 60 fsw began on February 2, 1975. The excursions were carried out in accordance with the following schedule: Day 1 1800 Compress to 60 fsw using air. Day 2 0927 Team A compresses to 200 ft for a 60 min bottom time. 1502 Team B compresses to 200 ft for a 60 min bottom time. 52 TABLE 24 Air decompression from air saturation at 60 fsw Depth Rate of (Ft) Decompression Time (min) 60 to 30 6 min/ft 180 30 to 28 22 min/ft 44 28 to 26 23 min/ft 46 26 to 24 24 min/ft 48 24 to 22 25 min/ft 50 22 to 20 26 min/ft 52 20 to 18 27 min/ft 54 18 to 16 28 min/ft 56 16 to 13 29 min/ft 87 13 to 10 30 min/ft 90 10 to 8 31 min/ft 62 8 to 6 32 min/ft 64 6 to 4 33 min/ft 66 4 to 2 34 min/ft 68 Time at 68 min 68 1 foot Total 17 hrs. 15 min 53 Day 3 0912 Team A compresses to 250 ft for a 60 min bottom time. 1502 Team B compresses to 250 ft for a 60 min bottom time. Day 4 0911 Team A compresses to 300 ft for a 60 min bottom time. 1500 Team B compresses to 300 ft for a 57.4 min bottom time. Day 5 2000 Begin decompression from 60 ft to the surface. Day 6 1315 Subjects surface. Results : T wo-Hundred Foot Excursions : No problems attributable to bends were noted. One subject reported pain in the left elbow during the excursion. Symptoms were exacerbated by decompression. The pain became progressively worse over the course of the three hours after arrival at storage depth prior to his reporting it to the medical officer. He was treated with oxy- gen and recompressed to 100 fsw. When no relief was reported, subjects were decompressed to storage depth. The diagnosis was made that this sub- ject had bursitis, a pre-existing condition in his other elbow. Further treatment consisted of hot towels for the elbow. Two-Hundred Fifty Foot Excursions : On February 4, 1975 subject HT re- ported bilateral numbness of his fingers and backs of hands following the morning excursion to 250 fsw at return to 60 fsw, plus 10 minutes. Prelim- inary diagnosis was a vasoconstrictive phenomenon due to the elevated par- tial pressure of oxygen. To confirm the preliminary diagnosis, the subject was asked to breathe one cycle of 25-minute duration, at 60 fsw, after which he reported no exacerbation or relief of symptoms. Following immersion of his hands in warm water, temporary relief was obtained. Final diagnosis was that subject HT was susceptible to the effect of elevated oxygen par- tial pressures, and that the symptoms reported were indicative of oxygen toxicity. No symptoms of decompression sickness were reported following the 250- fsw excursions. Doppler bubble sounds were heard on subjects HT and DS, the two subjects exposed to the treatment regimen the previous evening. There were no bubbles detected in the other six subjects during the periods in which they were monitored. Thre e-Hundred Foot Excursions : The 300 fsw excursions were conducted on February 5. Subject HT was not allowed to participate in the morning excursion as he reported the tips of his fingers were still numb. Following a report that the symptoms had cleared, he was added to the afternoon ex- cursion. The morning excursion proceeded without incident, but at 54 minutes into the afternoon excursion, subject HT went into convulsions. Following 54 completion of the convulsions and resumption of a normal breathing pattern, decompression to storage depth began (at 57.4 minutes into the excursion) and proceeded without incident. Ten minutes after return to 60 fsw, subject WM reported bilateral deep upper arm (triceps) pain. Ten minutes later, at 1800, WM and tender FR (JR was locked in from the surface) were compressed to 100 fsw. On arrival, WM began breathing 50 percent oxygen in nitrogen. After 10 minutes, the subject was switched to 50 percent oxygen in helium, for the remainder of the 25-minute treatment. After the treatment cycle, during which symptoms were relieved, subject WM was switched to a breathing mixture of 20 percent oxygen in helium and was decompressed on the 300-foot for 60-minute excursion decompression profile from the 100 fsw level. At 70 fsw, WM reported numbness of fingers and was asked to breathe chamber atmosphere (air) for the remaining 13 minutes of the decompression profile. After the initial switch to held ox, WM experienced urticaria which cleared as treatment progressed. On arrival, he said "Skin feels tight," over the left aspect of the upper arm — a condition which continued through surfacing. Following the treatment of WM (2000 hours), subject HT went into shock (BP 80/40, pulse 80 and weak), and was rapidly administered 200 cc of Lac- tated Ringer's solution, followed by an additional 1000 cc over the next three hours. Over the next seven hours, 1000 cc of D5W 5 percent dextrose in water were administered and then 1000 cc of Lactated Ringer's at 15 drops per minute to keep the IV open. It was felt that this was a continuation of the oxygen-toxicity problem he had been experiencing. Performance Tests The results of the performance tests are summarized in Table 25. An analysis of the data determined that the standard errors of the mean were both variable and high, in some cases exceeding the percentage changes them- selves. Thus, in spite of the fact that considerable practice was offered prior to the dive, the variability of results was high. Such variation could be attributed to many factors in addition to depth and inert gas narcosis such as fatigue, motivation, learning rate, etc. Recognizing the dangers of averaging percentages, it is apparent from Table 25 that the poorest performance was elicited during the presaturation bounce dives. The slight improvement shown during tests at 60 fsw satura- tion are minor and may simply reflect continued learning. The results ob- tained, during excursions show considerable decrement during the 300-foot excursions (and post-saturation bounce dives) compared to those data obtained at 200 and 250 fsw. There appears to be some improvement in performance during the 200- and 250-foot excursions compared to the initial bounce dives to those same depths. Some learning is still present however, as can be seen by comparison of the pre- and post-saturation dives to 300 fsw. Thus, the improvement in the excursion results compared to the bounce dives may be a function of learning rather than a physiological adaptation to narcosis. LO CN O P P CU co o fd O PQ (0 -P CU 4H W > M O p -H P eu 4-1 Q w p a) 4H O o 3 o o CO PQ a cu o o •H fd p m rd u +J 3 CO co P o fd -p Pn co fd C P O 4H •H -- W P 3 VO CO U O X P ft w (d o •H p fd H 3 -P o rH CO rH CN 1 + + 1 + O rH CM v£> H ro 1 + 1 1 cn ro CN CN H H (N * I + 1 I I ro rH ro ro ro + + + I + r-» cn 00 + + + o ^r + in ro cn H H (M ^O I I I I c ■H C B U fd -H id a p cu co co PQ W p X! rH -H CU +JH Dig (d (d -h -h, S PQ Q Eh X! I I I I I I I I I CO CT> CN + + I O LO ro + 00 o ^r H r- H "vF oo i i i i i I s " CF> LD i«Q I I I I I I H ro ro «s!< rH CN H CN I I I I I £ . •H >h f3 -H fd ft p o 0) CO CO o PQ H ro P ,C rH -H CU P rH tn g frt rrt -H -H, S PQ Q Eh X CO CN I LD I CO ro ro + <7> CT> I CO CN + CO |x C rd in o c o •H P td !H -p fd co -P o o <4H I o co m o tn c •H fi C •H cn CU .Q P fd •a cu c -H fd P o fd P fd a 56 Observations of the behavior of the two groups also indicated little or no adaptation during the deep excursion dives as compared to bounce dives, At 300 fsw, the subjects were obviously euphoric (in group B especially) , with considerable hilarity, confusion, and slow-witted reactions to instruc- tions from the outside control crew. When the oxygen convulsion occurred at 300 fsw, for example, the experienced inside controller was urging im- mediate decompression, although he is normally well aware of the dangers of decompressing an individual during a convulsion. Vital Capacity Measurements of vital capacity were made during the saturation dive, at pre- and post-excursion periods, and pre- and post-saturation to check for evidence of pulmonary oxygen toxicity (Clark and Lambertsen 1971, Widel et at. 1974). The results shown in Table 26 indicate a marked decrease in vital capacity in two of the subjects based on 10% being defined as a significant decrease. TABLE 26 Results of vital capacity measurements Subjects 200 Pre ft Post 250 Pre ft Post 300 Pre ft Post Post Saturation H.T. 5.97 5.98 6.21 6.02 6.2 5.0** 5.65 (-5.4%) T.B. 4.76 4.62 4.00 4.39 4.0 4.0 4.01 (-15.8%) R.J. 5.60 5.41 5.60 5.50 5.3 5.35 5.5 (-0.9%) A.O. 5.03 5.88 6.19 7.60 4.6 7.6 4.2 (-20.8%) D.S. 4.00 4.22 4.40 4.25 4.51 4.4 4.2 (+5.0%) M.B. 6.70 6.67 6.68 6.61 6.80 6.65 6.65 (-0.7%) J.H. 6.00 5.71 5.95 5.85 5.85 5.42 5.91 (01.5%) W.M. 5.81 5.82 5.40 5.40 4.90 5.59 5.30 (-8.8%) Total 44.14 44.31 44.43 45.62 42.16 44.01 41.47 — +0.4%* +0.1%* +3.4%* -4.5%* -0.3%* -0.06%* * % change from 200 ft. pre-saturation dive ** Subject H.T. not feeling well during this period 57 Considering the decrease in vital capacity, and the other signs of oxy- gen toxicity described earlier, such as the overt convulsion and the numb- ness of fingers, it must be inferred that saturation-excursion procedures, as performed in the present study, carry a definite risk of both pulmonary and central nervous system oxygen toxicity. Hematology and Blood Chemistry Platelet studies There was a significant loss of platelets after the 250-fsw bounce dive with a slight recovery prior to saturation. The lowest counts were obtained following completion of all the excursion dives from saturation depth at which point the mean percent loss was 28.0 ± 6.18 (SEM) (P < .02). After surfacing from the saturation depth, the counts were still significantly depressed. There was a trend toward recovery thereafter except for the groups which performed the 300-fsw bounce dive in which there was a further (15.0% ± 5.48 SEM) reduction in count. Platelet aggregation studies indi- cated that the fall in circulating platelet count was accompanied by a marked and statistically significant reduction in sensitivity of platelets ADP-induced aggregation. This trend persisted in the group which did the post-saturation 300-fsw bounce dive. Hematology Red-cell counts (performed electronically) and PCV showed evidence of a significant anemic response which was most pronounced in the sample col- lected at saturation depth following completion of all the excursion dives. Visual red-cell counts and hemoglobin concentration showed similar but not statistically significant trends. White-cell counts were noticeably and significantly increased after the 250-fsw bounce dive and prior to the sat- uration dive. No significant changes in corrected sedimentation rate were observed. Blood Chemistry In the majority of divers, changes in plasma enzymes activities were minimal. However, two subjects showed relatively large increases in cer- tain plasma enzymes. One demonstrated elevated LDH and CPK levels immediate- ly following the pre-saturation bounce dive to 250 fsw. CPK continued to increase to a maximum of 22 times control value post- saturation, followed by a decrease 24 hours post-saturation. The maximum enzyme changes occurred after he suffered from apparent oxygen-induced convulsions following the 300-fsw excursion dive. A second subject exhibited elevations in LDH, GOT, GPT after the 300- fsw excursion. These enzyme activities reached a maximum of +82.8%, +364.1%, and +1177%, respectively, immediately post-saturation. 58 Decompression ; The decompression to the surface began at 2000 hours, 6 February, and continued until 1315 hours, 7 February, and was uneventful. Doppler bubbles were heard on several of the divers during the ascent to the first stage, which cleared after the rate slowed. One subject had Doppler bubbles after surfacing, but did not experience symptoms of decompression sickness. Summary It is concluded that, so far as the present study is concerned, there is insufficient evidence to support an adaptation to nitrogen narcosis in compre ,sed air saturation-excursion diving. Based on the risk of oxygen convulsions, it was recommended that no compressed air excursions be made to 300 fsw when saturated at a storage depth of 60 feet with air as the breathing mixture. Due to symptoms of bends during decompression from the 300 fsw excur- sion, it was recommended as a precaution that excursion times to 250 fsw be reduced from 60 to 45 minutes bottom tim e under open-sea conditions. The lack of symptoms of oxygen toxicity and inert gas narcosis in studies, where the subjects breathed a normoxic mixture at storage depth and used air only on excursions, suggests that while working air excursions beyond. 250 fsw should not be made from air saturation, they perhaps could be car- ried out from a normoxic saturation. The latter has two advantages. The first is in possibly allowing divers to "adapt" to a higher nitrogen par- tial pressure, thus reducing the narcotic impact of deeper air excursions. The other, rather obvious, advantage is the reduction of oxygen partial pressure in the storage breathing gas. It is recommended at the present time, therefore, that air saturation be limited to depths of 60 feet and that air excursions from 60-foot air saturations be limited to 200 fsw for periods up to one hour. In special circumstances, however, with thorough training of divers and extra care being given to safety procedures, it should be possible to extend the excur- sion depth to 250 feet for periods of one hour. While it is recognized that the 250-foot excursion depth was used in the SCORE program, it is es- sential to provide a safety margin of sufficient magnitude to allow for those individuals who are especially sensitive to nitrogen narcosis and oxygen toxicity. Further data are needed before recommendations can be made regarding repetitive dives made under these conditions. V. FIELD STUDIES Many open sea programs have been and are continuing to be carried out in which extensive vertical excursions are iticide. The programs contained in this section are those which had as a primary objective, the test and 59 evaluation of advanced excursion diving procedures which had previously been studied in the laboratory. In each project described, every effort was made to conduct the dives with maximum safety and to document the re- sults as accurately as possible under open-sea conditions. V-A LORA Introduction : In 1973 a shallow water habitat program was carried out by members of the Memorial University of Newfoundland. Location: St. Phillips, Newfoundland Date: August 22-23, 1973 Duration: 24 hours, 16 minutes Saturation Depth: 26 fsw Breathing Gas: Habitat - air Excursions - air Aquanauts : Two Water Temperature: 54.5°F Habitat Temperature: 70-78°F Facility: LORA Habitat - an 8 x 16 foot structure Purpose : To evaluate the habitat facility under operational conditions, to con- duct routine hull maintenance; to observe fish behavior during a 24-hour cycle, and to test a new decompression procedure. Excursions : Four excursions were made by the two divers to a depth of 35 fsw. Three, excursions were for 60 minutes and one was for 75 minutes. No difficulties were encountered on any excursions. Decompression : Upon completion of the fourth excursion, the two aquanauts spent 8 hours in the habitat at the storage depth of 26 fsw after which they proceeded directly to the surface with, no decompression stops. No symptoms of bends were noted by either diver. 60 Summary : The investigators concluded that "the divers did not reach full satura- tion at hatch depth," but that "the length of the dive was such that this was approached." The 8-hour "soak" period at the 26 fsw storage depth fol- lowing the fourth excursion, was required to allow the nitrogen taken up during the excursions to be released and the tissues to reach equilibrium with that depth. The authors further concluded that, "It is possible to surface directly when fully saturated at the hatch depth (26 feet) " (English 1973) . During the period February 12-15, 1975 an additional saturation dive in Newfoundland was made using LORA. The saturation depth was again 26 fsw. The habitat was under the ice with a water temperature of 28.6° F. A total of 36 man-excursions to a depth of 35 fsw were made by the three aquanauts. The average excursion time was 38 minutes with the longest being 54 minutes. Upon completion of the mission, the aquanauts breathed oxygen for six 20-minute periods with 5-minute periods in between breathing habi- tat air. This was necessary to allow the divers to surface as quickly as possible following the last excursion. Following this procedure, the aqua- nauts entered the water and swam directly to the surface. Eighteen hours later the aquanauts flew from Newfoundland to Montreal. No symptoms of decompression sickness were noted. V-B H ydro -Lab Introduction : The Hydro-Lab Underwater Research Program was a long-range scientific and educational program centered around the Hydro-Lab, a manned habitat that operated at either ambient or surface pressure. The program was operated under the auspices of the Perry Foundation, Inc., Riviera Beach, Florida. Although a few earlier dives were made, the principal program began in February 1971. As of December 1975, the Hydro-Lab system saturated 319 diver-scientists in teams of 2-4, at the habitat hatch depth of 42 fsw. The average satura- tion time was six days for each team. An additional 24 divers were satu- rated at a depth of 60 fsw for 5-7 days, making a total of 343 saturated diver-scientists. The shortest mission was 24 hours and the longest was 13 days. There have been over 100 separate missions. Table 27 shows the dates and number of divers saturated since 1971. Purpose ; : The Hydro-Lab Program was devoted primarily to providing marine scientists with a facility and an opportunity to conduct extensive studies relating to marine biology, geology, ocean dumping and other aspects of marine re- source development. The Program also included studies of chemistry, physics, 61 TABLE 27 Summary of Hydro-Lab saturation missions Dates February 1971 - December 1971 January 1972 - December 1972 January 1973 - December 1973 January 1974 - December 1974 January 1975 - December 1975 Total Number of Divers Saturated 24 53 99 113 54 343 physiology, as well as ocean technology. As new diving procedures were developed they were tested using Hydro-Lab and subsequently used on a rou- tine basis to provide additional flexibility to divers conducting marine resource studies from Hydro-Lab and elsewhere. Location: Date: Duration: Saturation Depth: Excursions to: Breathing Gas : Aquanauts : Visibility: Bottom Water Temperature Surface Currents: Sea State: Facility: 1.2 miles (123°) off Bell Channel Light, Lucaya, Grand Bahama Island February 1971-December 3975 1-13 days saturation 42, 60 fsw 250 fsw storage - air excursions - air 2-4 per team 40-125 feet 24.0-29.5°C 0-0.5 knots 0-15 feet (short period) Hydro-Lab, shown in Fig. 5, normally rests at a depth of 47 feet, although the bottom hatch is at 42 feet„ The area is surrounded by large coral heads. Coral channels continue a short distance seaward into 70-80 feet 62 Photo: Dick Clarke Fig. 5. Hydro-lab habitat. .of water. A drop-off or wall beginning at a depth of 150 feet is approxi- mately 1,200 feet from the habitat. Figure 6 depicts the bottom topography surrounding Hydro-Lab. Hydro-Lab is an 8 x 16 foot cylindrical chamber with an attached 3 x 10 foot submarine dry transfer tunnel. It contains two bunks, air conditioner, dehumidifier, electrical panel for 110 AC and 12 volts DC, communications radio, sound power phones, CO2 scrubber, air inlet valves, and emergency and oxygen breathing masks. It also has a diver lockout trunk, portable toilet, interior 110 and 12 volt lights, 63 "f «««*»■ m »«, | * «*^ft* Ilk*. «w* u*oA»c>r»$), *| C®«*.1 Fig. 6. Bottom topography of Hydro- lab site. exterior 1000 watt light, seven windows (one of which is four feet in di- ameter) , 12-volt emergency batteries, tables, fresh water shower and hatch attachments . The habitat can support 3-4 scientists for periods up to 14 days. The life support system maintaining the habitat from the surface is built into a 23-foot fiberglass boat hull. This contains a 24 h.p. Lister diesel generator (7.5kw AC), a high pressure (3000 psi) air compressor, a low pres- sure (200 psi) air compressor, 250-gallon fuel and water tanks and a 12V DC system. The total system is completely self-sufficient, eliminating the need for a manned support vessel overhead. The system maintains internal breath- ing air, high pressure air to fill scuba tanks, supplies fresh water and generates electrical power to the habitat. Life support is designed to oper- ate more than seven days with only minimum on-site maintenance. An emer- gency system within the habitat can support four persons for several days. 64 A trunk with intermediate hatches allows diver lockouts should the habi- tat be at atmospheric pressure. The lockout trunk can be operated by either a diver located within the trunk or by someone within the habitat. Decompres- sion takes place and is controlled from within the habitat itself. A captured-air stand-up booth large enough for four men was used outside the habitat as a safety and bottom air- filling station. A four-man decom- pression chamber with a 225 fsw capability is located on shore at the Inter- national Underwater Explorers Club. Divers can normally be transported from the habitat to this chamber in 10 minutes. Scientific laboratory space was also available at the shore facility. Divers : The age range of Hydro-Lab aquanauts was from 18 to 56 with an average age of about 30. Of the 343 aquanauts about 11% were females having an aver- age age of 27.5 years. Aquanauts were selected based on the merits of scien- tific proposals submitted, physical condition, and diving experience. Each aquanaut was required to have a current physical examination. In addition, a pre- and post-dive examination was administered at the Hydrc-Lab site. Aquanauts also submitted a resume of diving experience and certification. Divers saturating for the first time received an on-site diving check-out prior to their mission. Certification alone was not considered to be suf- ficient for a diver's acceptance, although lack of it was not necessarily grounds for rejection. Some divers had limited diving experience, but were allowed to saturate due to the nature of their work and their ability to conduct it safely. Limitations on excursion-diving from Hydro-Lab, although based partially on previous experience and certification, were based mainly on performance during the open sea check-out dive. Divers who performed poorly were either rejected entirely from saturation diving or were limited to short excursions. The Hydro-Lab program had two full-time operational personnel: the project manager and assistant manager. Each team was required to bring at least two additional support divers. Procedures ; Prior to the availability of the NOAA OPS vertical excursion profiles in 197 3, excursions from Hydro-Lab beyond a depth of 90 fsw were not permitted, This was a safe practice since the present excursion profiles allow a 5-hour excursion to 90 fsw from a 40-f sw saturation and un] imited time from a 60- fsw saturation. The following procedures were used for all deep excursions from Hydro- Lab: Pre -Excursion 1. The dive plan discussed with and approved by the Hydro-Lab management. 65 2. A transect line placed from Hydro-Lab to the maximum depth of tbe excur- sion. 3. Buoys placed along the transect line from the Hydro-Lab to the edge of the submerged wall at a depth as near as possible to the saturation depth so the aquanaut maintains the saturation depth unti] reaching the wall. 4. Prior to each excursion beyond 600 feet swimming distance from Hydro-Lab, the divers contacted Hydro-Lab base by radio, reviewed the excursion plan, and received approval. Excursion Rules 1. The excursion was cancelled if conditions were, in the opinion of the Hydro-Lab management, too rough, water visibility poor, currents too strong, or other-wise unsafe. Only under special, pre-planned circumstances were excursions made to depths greater than 200 fsw. 2. Each diver departed Hydro-Lab, using a full set of double 72 foot 3 scuba tanks, with an "octopus" regulator, or equivalent. If necessary, the divers were accompanied by a surface support boat. All excursions below a depth of 130 fsw required a surface support boat. A surface support diver was in the water to monitor the saturated divers if deemed necessary by the Hydro- Lab management. Spare scuba tanks were in the surface support boat or on the bottom to serve as emergency air supply or for extended excursions. 3. Aquanauts were required 1 to maintain visual contact with the transect buoys or the transect line at all times during excursions. 4. Aquanauts proceeded at the pace of the slowest swimmer along the tran- sect line, maintaining the saturation depth. 5. Bottom time for the excursion began when the aquanauts went below satu- ration depth. 6. Aquanauts swam slowly down the buoy line, and changed to an unused set of double tanks if necessary. If the used set of tanks did not contain at least 1000 psi, the excursion was aborted. 7. Excursion times normally were conducted in accordance with NOAA OPS no- decompression tables. Decompression excursions required separate tables and special equipment. 8. When extra tanks were on the bottom at the conclusion of an excursion, or when the tank pressure reached 600 psi for any aquanaut, all aquanauts returned to the extra set of doubles. They changed to these if the set used on the excursion had less than 1000 psi. If the excursion was made without extra tanks on the bottom, all aquanauts returned to the saturation depth when the tank pressure reached 1000 psi for any one aquanaut. 66 9. The aquanauts ascended at 30 feet per minute up the buoy line, and re- turned to Hydro-Lab at the pace of the slowest swimmer, maintaining the sat- uration depth, except in the case of a decompression excursion where they held at each decompression stop during the swim back. 10. Bottom time for the no-decompression excursions ended when the aquanauts returned to the saturation depth. For decompression excursions, bottom time ended at the moment of ascent Decompression : The aquanauts decompressed inside the habitat. Prior to commencing the mission, the Hydro-Lab management instructed the team on decompression pro- cedures which were carried out by the aquanauts themselves upon completion of the mission. The decompression schedule used for 42- foot saturation mis- sions is shown in Table 28. Following decompression, a surface support diver swam tc the habitat to assist the aquanauts in locking out and ascending to the surface. Aqua- nauts remained near the shore-based recompression chamber for 24 hours and did not fly for 36 hours after completing decompression. One three-man, 60-foot saturation mission was carried out in which decompression was accom- plished in accordance with the schedule shown in Table 29. Other decompres- sions were successfully carried out using Table 24 including several from a saturation depth of 42 fsw. In using Table 29, the saturation depth is selected from the left hand column; the first stop, gas mixture and time from the middle column; and all subsequent stops from the right hand column. For example, for an 80- foot normoxic saturation, the first stop is 60 fsw on air for three hours. The next stop is at 55 fsw on air for five hours, etc. Results ; A total of 100 no-decompression and four decompression excursion dives were made from a 42-foot saturation depth to depths greater than 125 feet and to 200 feet respectively. In October 1973, a series of 16 no-decompression excursions from 42 fsw saturation were made by two aquanauts to depths ranging from 50-200 fsw. Fig. 7 summarizes the depths and times. No symptoms of bends were noted during any of these excursions. Fig s 8 illustrates the excursion profile used by 25 different aquanauts in making excursions to a depth of 130 fsw in July and August 1974. These excursions required each aquana.ut to swim approximately 3,000 feet and involved a 33-minute bottom time. No symptoms of bends occurred during any of these excursions. The maximum bottom time for a 130- foot, no-decompression excursion is 70 minutes, so the lack of bends is not surprising. Longer bottom times were not attempted because the divers were college students participating in an advanced scientific diving training program. 67 TABLE 28 Hydro-Lab decompression profile from an air saturation at 42 fsw Depth (ft) 42 to 24 24 stop 24 to 20 20 stop 20 to 16 16 stop 16 to 12 12 stop 12 to 8 8 stop 8 to 4 4 stop 4 to surface Rate of Ascent (ft per min) Time (min) 9 180 4 180 4 180 4 75 4 80 4 90 4 Breathing gas air air air air air air air oxygen air oxygen air oxygen air Decompression Time 9 hours 33 min. air 4 hours 5 min. oxygen Total 13 hours 38 min. Also in July 1974, a series of excursions was made by three aquanauts to depths of 150 fsw and 200 fsw from a 42-foot saturation depth. Fig. 9 is typical of the 150-foot excursions and represents a total of 12 excursions made by two females and one male aquanauto Bottom times at 150 fsw were between 21 and 42 minutes for ten of the excursions. The ether two excur- sions were "bounce" dives to 150 feet as part of a longer excursion at a shallower depth. As in each Hydro-Lab excursion, a swim of about 3,000 feet was required. Seven 200-foot excursions made by the same three aquanauts are shown in Fig. 10. In all of these excursions, the primary mission was to collect biological specimens and to photograph the deep reef wall. The 68 TABLE 29 Decompression schedules following normoxic/air saturation exposure* First Stop Subsequent Stages Saturation Time Time Depth Range Depth Gas At Stop Depth Gas At Stop (fsw) (fsw) (hr :min) (fsw) (hr :min) 96-100 80 Air 3:00 75 Air 4:00 91-95 75 Air 3:00 70 Air 4:00 86-90 70 Air 3:00 65 Air 4:30 81-85 65 Air 3:00 60 Air 4:30 76-80 60 Air 3:00 55 Air 5:00 71-75 55 Air 3:30 50 Air 5:00 66-70 50 Air 3:30 45 Air 5:00 61-65 45 Air 3:30 40 Air 5:00 56-60 40 Air 4:00 35 35 Air Oxygen 0:30 1:00 51-55 35 Oxygen 1:00 35 35 30 Air Oxygen Air 0:30 1:00 2:00 46-50 30 Air 2:00 30 25 25 Oxygen Air Oxygen 1:00 0:30 1:00 41-45 25 Oxygen 0:30 25 25 20 Air Oxygen Air 0:30 1:00 3:00 36-40 20 Air 1:30 20 15 15 Oxygen Air Oxygen 1:00 0:30 1:00 31-35 15 Oxygen 1:00 15 15 10 Air Oxygen Air 0:30 1:00 4:00 26-30 10 Air 2:00 10 5 5 5 Oxygen Air Oxygen Air 1:00 0:30 1:00 0:30 22-25 5 Oxygen 0:30 5 30** Oxygen Oxygen 1:00 0:30 0-21 No Decompression Surface *This table was calculated* based on a normoxic storage breathing gas. Be- cause the Hydro-Lab atmosphere was air, the decompression began at the 46- 50 fsw level (the air equivalent depth) following a saturation at 60 fsw. **Not used during Hydro-Lab program 69 e o u m CO +■> p q rd P D 1 fO O -P >i ,Q (1) fti e co c -H CO ^ 3 O X (1) c c ■H CO CO Q) U & O o I o xaivwvas ao laaa mi Hiaaa 70 50- SATURATION I ,v ioo_ 125. 20 30 TTMF TN MINUTES 60 Fig. 8. No-decompression profile used by 25 aquanauts for excursions to 130 fsw from air saturation at 42 fsw, TIME IN MINUTES Fig. 9, Typical nc-decompression profile used by three aquanauts for 12 excursions to 150 fsw from air saturation at 42 fsw. 71 SATURATION TIME III MINUTES Fig. 10. Typical no-decompression profile used by three aquanauts for seven excursions to 200 fsw from air saturation at 42 fsw. bottom time for these excursions was 18 or 19 minutes with no symptoms of bends occurring. During a different mission in August 1974, a series of 13 excursions was conducted without incident to depths of 165-175 fsw by four divers tc carry out geological and oceanographic studies. These excursion profiles are shown in Fig. 11. In December 1974, a series of no-decompression excursions was made to depths ranging from 180-200 fsw by the two operations directors of the Hydro- Lab program (Figs Q 12 and 13) „ They all were made from a 42-foot air satu- ration and were carried out without incident. It may be noted that some of the excursions depicted in Figs. 12 and 13 have longer bottom times than those allowed by the NOAA OPS tables. This is because during these initial excursions the bottom time ended once the aquanaut left the maximum depth attained rather than when the storage depth was reached. The two, two-man excursions made to a depth, of 200 and 80 feet for periods of nine and 28 minutes respectively are shown in Fig. 14. The final no- decompression excursion was made to 165 feet for 31 minutes and is shown in Fig. 15. No symptoms of bends were noted during or following any of these excursions. 72 40-1 SATURATION SATURA7IC 40-, 5 10 15 20 25 TIME IN MINUTES a. 25 Minute 3-Man Excursion to 165 Feet SATURATION 40-, 5 10 15 TIME IN MINUTES b. 18 Minute 4-Man Excursion to 175 Feet SATURATION 1 i 5 r 10 i 15 TIME IN MINUTES c. 15 Minute 3-Man Exc ursion to 175 Feet 20 5 10 TIME IN MINUTES d. 17 Minute 3-Man Excursion, to 1 75 Feet Fig, 11, No-decompression, profiles for 13 excursions to depths of 165-175 fsw from air saturation at 42 fsw. During this same December 1974 mission, two, two-man decompression ex- cursions were made to a depth of 200 feet as shown in Fig. 16. The purpose was to demonstrate the feasibility of conducting decompression excursions from Hydro-Lab prior to the SCORE project. The decompression times computed by Tarrytown Labs (Table 30) were actually doubled during these excursions to ensure a satisfactory safety margin. Biomedical Program : During several Hydro-Lab missions, an integrated, self-contained Doppler bubble detector with monitoring and recording equipment was provided for 73 SATURATION 50- K 100- 150— 200- -//- J SATURATION -1 1 I—Tj^T 1 200 10 20 30 o n TIME IN MINUTES TIME IN MINUTES a. 10 Minute 2 -Man Excursion to 130 Feet b. 14 Minute 2-Man Excursion to 180 Feet 30 10 . _ SAJURAIIOf 50- 100- 150- 200. T- 40 -I 10 20 30 TIME IN MINUTES 25 Minute 2-Man Excursion to 190 Feet Fig. 12. No- decompress ion profiles for six excursions to depths of 180-190 fsw from air saturation at 42 fsw. use by the Applied Physics Laboratory of the University of Washington. The aquanauts were trained to make recordings after each excursion and during decompression. In this manner, data from a large population of divers were collected and the use of equipment in the field was demonstrated. Even though there were some technical problems, good recordings were obtained from sev- eral teams of divers. In no instance either a^ter excursions, including those to 200 feet, or during decompression, were bubbles detected. While this does not preclude the existence of bubbles, it does indicate that the decompression tables and the excursion profiles probably were on the con- servative side c Other biomedical studies included measures of vital capacity, metabolic rate, cardiovascular function, brain wave activity, stress, fluid volume 74 150_ TIME IN MINUTES Fig. 13. Twenty- seven minute two-man excursion to 200 fsw from air saturation at 42 fsw. in 20 TIMF IN MltlllTF.S Fig. 14. Two-man exursions to 200 fsw and 80 fsw from air saturation at 42 fsw. 75 TIME IN MINUTES Fig. 15. Two-man excursion to 165 fsw from air saturation at 42 fsw. regulation, and blood chemistry. Because none of these studies were directly- correlated with excursion dives, they will not be discussed here. It will suffice to say that the results were all negative with the exception of blood chemistry. Hematology and Blood Chemistry Two studies were conducted during the Hydro-Lab program. In the first study (April 1973), 20 young-adult divers, 19 male and 1 female, served as the experimental subjects Each subject was saturated for three days at a depth of 42 fsw. Descending excursions did not exceed a depth of 130 fsw. Decompression was carried out according to the schedule shown in Table 28 The divers were university graduate students completing the "Scientist-in- the-Sea" training program, and their instructors. Twenty-five ml blood samples were collected from a forearm vein, occluded with a wide tourniquet, into disposable plastic syringes using disposable 20-gauge needles. The blood was immediately distributed into test tubes containing the appropriate anticoagulant for a particular test. Samples were collected the day before the dive, 30 min before the dive, 30 min after decompression, and daily for three days thereafter where possible. Although it was not possible to main- tain strict fasting conditions at the time of sampling, an effort was made to collect, samples just before a meal, so that alimentary lipemia was mini- mal . 76 SATURATION 100 150 200 50 100 150 A I L'RATI ON 200 20 k 1 1 ( 1 20 40 60 80 100 b. Forty-seven-minute, two-man decompression to 200 feet £J- Fig. 16. Decompression excursion profiles for four excursions to 200 fsw from air saturation at 42 fsw. In the second study (August 1973), twelve healthy, young-adult males, all members of the University of Western Ontario diving Club, served as volun- teers. The depth, decompression profile, and swimming excursions were the same as in the first study except that the dive extended over five days, including decompression time. Blood was collected, from each diver 48 hours, 24 hours, and immediately pre-dive; once during the dive (dive day 2 or 3); and immediately, 24 hours, 48 hours, and 72 hours post-dive. Each in-dive blood sample was vented with a 20-gauge needle and decompressed in the trans- port pot from 2.4 ATA. Decompression took at least 10 minutes. Sample volume was kept to the necessary minimum (20-25 ml) and blood was always collected before a meal to minimize alimentary lipemia. 77 TABLE 30 Decompression schedule for excursions to 200 fsw from air saturation at 42 fsw* Depth Rate of Ascent Time (ft) (ft per min) (min) 200 to 90 30 4 90 Stop — 5 90 to 80 10 1 80 Stop — 4 80 to 70 10 1 70 .Stop — 3 70 to 60 10 1 60 Stop — 6 60 to 50 10 1 50 Stop — 16 50 to 42 10 1 Total 43 Minutes * The lock-out submersible Johnson-Sea-Link was standing by as a back-up system during these excursions. Drug Administration Two members of each saturation team of four divers were assigned randomly to a treatment group or a placebo group. The treatment group received 300 mg three times daily of VK744CL2 (chemical name: 2- [ ( 2-aminoe thy 1) amino] 4-morpholino-thieno [3,2-d] pyrimidine dihydrochloride) for 24 hours before the dive, during the dive, and for three days thereafter. The placebo group received capsules identical in appearance and number but containing lactose. Drug administration was timed so that two blood samples were collected prior to medication and one, i.e., the pre-dive sample, after the subjects had taken four doses (1200 mg) . Double-blind procedure was followed throughout and each diver was coded separately so that in the event of a possible drug reaction, his medication could be identified without compromising the entire project. This never occurred. A member of the Hydro-Lab staff held the drug code . 78 When the results of the hematology and blood chemistry program were ana- lyzed, it was found that, with one exception, all of the subjects in both saturation-dive groups demonstrated a drop in circulating platelet count after surfacing. The extent of the drop ranged from 11.6 - 55.6% with most subjects showing the lowest count 24-48 hours after surfacing. Because all subjects did not. show maximum decrease on the same day, the mean maximum drop for the six subjects was calculated (34.5% ± 7.25 SEM (p < 0.001). The daily mean-percentage decreases were statistically significant in the 24-hour (p < 0.01) and 48-hour samples (p < 0.05). The seventh subject was not included in the calculations because he was thrombocytopenic prior to the saturation. It was concluded that saturation exposure of up to seven days in Hydro- Lab does not elicit significant tissue damage, as indicated by the normal isoenzyme pattern following decompression. Loss of platelets however, does occur and although not of sufficient magnitude to warrant concern, suggests that microbubble formation may occur during very safe decompressions. Com- plete details of these studies may be found in Fhilp, Freeman, Francey and Bishop (1975). It should be noted that the decrease in circulating platelets during the Hydrc-Lab studies was not found in the NOAA OPS program. This differ- ence in findings may be due to the fact that in Hydro-Lab the aquanauts made a rapid ascent to a depth of 24 fsw and then stopped every four feet for the remainder of the decompression. In NOAA OPS, on the other hand, the decompression was continuous throughout, which may have prevented small bubbles from forming and serving as a nucleus for the agglutination of platelets. Much additional work is required in order to identify the physiological or pathological significance of post-decompression thrombocytopenia and to de- termine the effects of repetitive diving, saturation diving, abnormal plate- let function and drug-induced alterations in platelet activity. Summary : The Hydro-Lab program has provided a facility for a significant number of excursion dives. There were no cases of bends following any excursion and no hard evidence of bends following decompression. A total of four out of 343 saturated aquanauts were recompressed as a precautionary measure fcllowing symptoms that would make the administration of hyperbaric oxygen desirable. v ~ c PRUNE I (Puerto Rico Undersea Nitrogen Excursion) Introduction ; PRUNE I was the sixth in a series of 10 missions designed to assess the marine resources along the Southeast Coast of Puerto Rico. Although the PRUNE program took place in about 100 fsw, all of the other nine missions took place at depths of 50 to 60 feet and were exclusively marine scientific 79 efforts. Over 50 marine scientists and engineers were saturated during these 10 missions. The work was carried out under the auspices of the Marine Re- sources Development Foundation with support from the Puerto Rican Government and NOAA. Purpose : PRUNE I involved marine biological surveys, underwater color visibility experiments, a biotelemetry study, a cosmic ray physics program, and the field evaluation of ascending excursion profiles. Topographical constraints did not perir.it the testing of descending excursion profiles as the maximum depth within a safe swimming distance of the habitat was 130 feet. Location: Ten miles off the Southeast Coast of Puerto Rico Date: April 24 - May 4, 1973 Duration : 14 days Saturation Depth: 95 fsw Breathing Gas: Habitat - 90-96% Nitrogen, 4-10% Oxygen Excursions - Air Aquanauts : Four Water Temperature: 74 °F Habitat Temperature: 80°F Habitat Humidity: 50-60% Facility: La Chalupa Habitat La Chalupa has a 48* x 20' x 10'8" barge-like exterior structure containing two steel chambers, each 8' diameter x 19' long (Fig. 17). One chamber is a living compartment with two 41" windows, four water beds, a desk, storage space, a small freezer, and a sink. The living compartment is capable of withstanding 50 psi internal pressure and is used as a decompression chamber when the habitat is surfaced at the end of a mission. The other chamber is capable of withstanding 50 psi external pressure and is the control com- partment. It has one 41" diameter window, a decompression control station, a galley, electrical controls, TV monitors, and other equipment. In an emer- gency, this compartment, can be used as a decompression chamber on the sea floor to a depth of 100 fsw. Both compartments have a transfer lock attached to an upper hatch, per- mitting transfer of personnel and equipment to a capsule located on the deck of the barge when the chamber is at pressure other than ambient. These cap- sules may also be used to evacuate personnel to the surface, under pressure 80 Fig. 17. La Chalupa habitat. in the event of an emergency. An unmanned life support buoy, located on the surface, provides the habitat with power, high and low pressure air, and fresh water. The sub port, or wet lab, a captured air-space located between the living and control chambers and open at the bottom, is used for entrance into the habitat, dry access between living and control compartments , storage space for scuba gear, a shower, a toilet, and 35 feet^ of work space on stainless steel tables. In case of loss or removal of the life support buoy, the habitat is equipped with emergency batteries capable of operating CO2 scrubbers and emergency lights for 48 hours. Additional emergency facilities provide for seven days of air, food, and scrubbing capabilities. High pressure air cyl- inders on the habitat contain 5600 standard cubic feet (SCF) of compressed air which could be used to operate the habitat air system, and to surface and de-ballast the habitat in event of loss of air compressors or life sup- port buoy. 81 Aquanauts ; The aquanauts were experienced male divers between the ages of 32 and 45. Each was required to undergo a physical examination including a complete series of long bone x-rays, and a physical conditioning program. Two had been saturated previously in open sea experiments. Procedure ; Once each day an ascending excursion was made by two or three divers. The divers followed the habitat umbilical to the prescribed depth and main- tained physical contact with it for the entire excursion. Wrist depth gauges were used which were calibrated daily with the master gauge in the habitat. The ascent rate was approximately 30 feet per minute. All excursions were made breathing air from either a standard set of double scuba cylinders or a hookah (breathing hose) attached to the habitat. The excursion times were calculated during the NOAA OPS program, espe- cially for use during PRUNE I. The times permit longer excursions than those tested during NOAA OPS, partially because only one excursion was made each day (see Tables 10 and 11, Section IV-A) . Further, the seafloor topography did not. permit preceeding downward excursions of any consequence. Thus, the calculation of tissue loadings was less complicated. The excursion times also were longer than the published tables because an additional margin of safety was introduced for general use in the NOAA Diving Manual (1975) . The divers constantly checked the time during each excursion and ques- tioned one another for any symptoms of bends. On long excursions the time was passed observing local reef inhabitants. Excursions were made on 10 successive days at times selected to be compatible with other planned acti- vities. Visibility and current conditions varied. The maximum current ex- perienced during an excursion was 0.8 knots. Results ; Twenty-three man-excursions were successfully completed. Two excursions each were made to depths of 25, 30, 40, 50, and 60 fsw. Table 31 gives a brief summary of these excursions and their results. In general, no real bends were noticed, although a few niggles were observed by one diver during some excursions. These symptoms are noted in the table. Decompression : Upon completion of the 14-day mission, an uneventful 49-hour and 20-minute- decompression was completed (Table 32) using the schedule calculated for Tektite II (Miller, Vanderwalker, and Waller, 1971) . Summary ; The absence of significant problems during either the NOAA OPS studies or PRUNE I, suggests that the ascending excursion tables developed and published 82 TABLE 31 Results of ascending excursions from a saturation depth of 95 fsw Excur . Depth Duration Habitat No. of Mix, N/0 2 Equipment Divers Symptoms (ft) 60 60 50 50 40 40 30 30 25 25 (min) 55 55 30 31 18 18 7 7 2 2 96/4 95/5 Hookah . . do . 90/10 do 95/5 94/6 96/4 94/6 95/5 95/5 93/7 Scuba .do do do do do do 2 None . 2 Niggle, right knee. 2 Niggle, left elbow. 3 None . 2 Slight niggle, right knee. 2 None . 2 Do. 3 Niggle, right knee. 3 Niggle, left elbow. 2 None . Same diver each time. are safe for use under the conditions prescribed. As more information on vertical excursion profiles becomes available, it will facilitate selection of the most effective depths at which to place ocean floor laboratories. Al- so, the upward excursion data will add to the margin of diving safety by dem- onstrating the depth limits to which saturated divers can ascend briefly should they become lost or injured. V-D PRUNE II (Puerto Rico Undersea Nitrogen Excursion) Introduction ; PRUNE II, conducted one year after PRUNE I, was the tenth in the ser- ies of eleven missions described in PRUNE I. Three of the same divers took part in both PRUNE I and II. As with PRUNE I, the aquanauts were required to undergo a physical examination prior to and following the mission. 83 TABLE 32 Decompression schedule used for PRUNE I and II** Depth Time at Stop Breathing (fsw) (min) * Mixture 103 - 90 10 Air 90 60 Air 85 90 Air 80 100 Air 75 110 Air 70 120 Air 65 360 Air 60 140 Air 55 160 Air 50 160 Air 45 10 Oxygen 45 150 Air 40 130 Air 35 20 Oxygen 35 150 Air 30 360 Air 25 30 Oxygen 25 150 Air 20 150 Air 15 50 Oxygen 15 120 Air 10 160 Air 5 60 Oxygen 5 110 Air Total: 49 hr, 20 min; oxygen breathing, 2 hr, 50 min * Ascent rate between stops, 1 ft per min. Last 5 min of each stop used to ascend to next stop ** Lambertsen (in Pauli and Cole, 1970) Purpose ; This project was designed principally to test the NOAA OPS descending ex- cursion profiles to a depth of 300 fsw, and to measure objectively any evidence of inert gas narcosis, using tests of time estimation and mental arithmetic. A secondary objective was to conduct a survey of benthic marine organisms. 84 Location: Date: Duration: Saturation Depth: Breathing Gas: Aquanauts : Water Temperature: Habitat Temperature; Habitat Humidity: Facility: Dive Site: Ten miles off the Southeast Coast of Puerto Rico March 18-29, 1974 11 days 106 fsw Habitat - 90-96% Nitrogen, 4-10% Oxygen Excursions - Air Four 74°F 80°F 50-60% La Chalupa Habitat (see PRUNE I for description) The habitat (Fig. 17) was located approximately 10 miles off the south- east coast of Puerto Rico at a depth of 110 feet (saturation depth 106 fsw) . The topography of the dive site was dominated by three major features: a broad terrace, an uninterrupted buttress reef on the outer edge of the ter- race, and a relatively steep terraced dropoff on the outer side of the reef into deep water as shown in Fig. 18. The buttress reef (probably a submerged ancient reef) was continuous and without spur and groove features for at least one-half mile (probably 20-30 miles) on either side of the site. This ridge had a relief of 45 feet and was approximately 400 feet wide. Its location, seaward of the habitat, made it necessary for the divers to ascend from the saturation depth of 106 fsw to a depth of 65 feet on each excursion to reach deep water seaward of the buttress reef. The bottom on the outer edge of the Puerto Rican Shelf, seaward of the buttress reef, dropped away in a series of ill-defined terraces from a depth of approximately 100 feet on the outer side of the terrace to 130 feet. The slope was approximately 20 degrees. Beginning at about 130 feet, the slope steepened to about 80 degrees. At about 150-160 feet the dropoff forms a vertical rock wall. This steep escarp- ment continues down to about 210 feet where a steep sediment talus slope laps up onto the walls forming a sloping bottom of 30-40 degrees. At a depth of 270 feet, this sediment slope with some rock outcrops, decreased to approxi- mately 20 degrees. There was an impression by the divers that the bottom slope increased again farther downslope, but the declivity was not measured. 85 I' 1 ' I' l l 'i- .'"II »'":im|i. i i rrH' i ,m;i.' ':' i ' ■v'l'l I ■ ■' |q 1 1 nib ■■ 1 1 .1' .1 « •>' i'f»» ' 01 li N l It I *° l i »"!,■: M I, IP ij/l.i I b li i in ;i Mi .1 b i •;' hih I 1 -,, , b '''' i ' in ■ I i*»|l'l|' ii"o ■} I eg ', 1,,'uv i r«s , i , © 1 ' Si 'Mm' lil-i'v'.'i'.-i M'.''!'= ' .'ife.: 1 n U L +J -H > •H T3 W OH M-l >i A S 1 o 8 00 •rH Cm -'.i ^iiV.:-,!.!.;'!,. '■!; "« 86 Diving Procedure ; Two divers made each excursion. Air was supplied via a 700-foot hose (hookah) attached to the habitat and was used for all excursions. A single one-inch hose was used for the first 550 feet. At this point, a "T" valve was inserted so that each diver had an individual 150-foot hose. The divers wore a full-face diving helmet (Kirby Morgan Band Mask, KMB-8) connected to the air hose. The helmet also contained hardwire communication to the habitat. In addition to the hookah, each diver wore a set of double 72-foot ^ scuba tanks as an emergency backup system. These tanks were manifolded so that the air from both tanks could be shunted directly into the diving helmet or breathed through a separate regulator attached to the scuba tanks. When two divers were making an excursion, the other two were in the habitat manning the communication system, logging times, and recording data. Because of the length of the hookah, approximately 225 feet of it was permanently anchored to the bottom as shown in Fig. 18. Rigid floats and weights were strategically placed along the next 400 feet so that the hose formed a long catenary reaching almost to the surface. This arrangement meant that the divers had only to pull the final 75 feet of hose across the coral- strewn seafloor. Upon reaching the 120- foot depth, the section of hose form- ing the catenary was hauled down so as to lie flat on the bottom and was tied to a coral head. The diners then had sufficient hose for making the primary descent. The ascent over the buttress reef while hauling and manipulating the hookah hose required a considerable expenditure of effort by the divers. For this reason, these excursions can readily be classified as working dives. Bottom time began on departure from 120 feet and ended upon leaving the maximum excursion depth. Testing Procedure ; Three tests were selected to assess the impact of depth and time in the water on psychological performance: an auditory vigilance task (Kennedy 1971) , a short-term (immediate) memory task (Digit Span, Wechsler 1955) , and a time- estimation task (after Pfaff 1968) . The auditory vigilance task was found not to be usable at depth because the exhalation noise from the divers 1 masks masked the stimulus. Some problems occurred with the administration of the short-term memory test; however, it will be discussed along with the more successfully administered time-estimation test. The method of time estimation selected for this study was the production method in which the experimenter verbally stated a given interval (standard) and the subject, in the water, was instructed to delimit verbally the begin- ning and the end of the interval (judgment) that he estimated to be equal to the given standard. For example, the subject in the water would make his estimate by saying "start" at the beginning and "stop" at the end of the es- J timated interval. A timer located in the habitat used to record the estimate would begin counting at 1/100 sec on the start command and was stopped on 87 the stop command by the experimenter in the habitat. The standards ranged from a stimulus period of 4 to 24 sec and were randomly ordered. In conduct- ing the digit span test in a fashion similar to Wechsler, the experimenter read sequences of four to ten digits to the diver who then repeated them back on command either in the same or reverse order. Results ; Ten, two-man excursions were made to depths ranging from 160 to 265 feet. The excursion profiles are shown in Table 33. Because of the required ascent over the buttress reef, the excursion times had to be modified. Table 34 shows the depths of each excursion, the times allowed at each depth without the buttress reef according to the NOAA OPS tables, the modified times taking the buttress reef into account, and the times actually spent at each depth. While the limits of the NOAA OPS excursion profiles were not tested be- cause of the required ascent over the buttress reef, the feasibility of making deep excursions using air was further demonstrated. Ignoring the problems of handling the long hookah hose, the excursions were uneventful with one exception. On excursion nine, one diver's hookah separated and he was forced to remove his diving helmet and use the backup scuba tanks to return to the habitat from the 120-foot temporary tie-off point shown in Fig. 18. There were no respiratory problems or symptoms of bends during any of the excursions. One diver experienced light headedness at a depth of 265 feet on an excursion scheduled for 275 feet. The dive was aborted at 265 feet and both divers returned to a depth of 200 feet and completed the excur- sion. The other diver on this excursion reported no symptoms of narcosis. The major findings of the time- estimation study were threefold: (1) all subjects made significantly longer time estimates at depth than they did on the surface, (2) this effect was uniform across all time standards, (3) some subjects were more affected than others. Group average estimates for the eight time standards at four pressure levels are illustrated in Fig. 18. Individual performances are shown in Fig. 20. Baseline estimates at surface pressure ranged from 90 to 95% true. All of the estimates made at depth were clearly longer than those made on the surface. Although the underlying cause for this finding is not clear, the trend observed is consistent with results of other studies (Bachrach and Bennett 1973; Baddeley 1975; Thomas, Walsh, Bachrach, and Throne in press) where time estimation was used as a human performance measure in stressful situations. The results of the digit span test were difficult to interpret since lack of time on many excursions yielded incomplete data for all subjects and learn- ing appeared to occur throughout the mission as shown in Table 35. The varia- bility in responding on the digit span was so great across subjects that sta- tistical evaluation could not be made. One subject did worse at depth (IK) , one did better (SK) , and the others remained roughly equivalent to surface performance (JM, AW) . Though inconclusive, it is interesting to note that some of the divers were able to repeat back a series of up to eight or nine 88 m 5 co m o •P fd c o •H -P rd P P rd co § co cm ro X! o o rH CM CO CM "^ rH IT) CMCMCMCMCMrHCMiHOOOO rHOOt^r^CMrHrOCM ooooomLnooLn v£)0000OOCMCMLnu-1*£> rHiHiHCMCMCMCMCMCMCM pHCMCO^LDvOr^OOCTirH T3 P M-l O O CM O P a) -a c •H Ti x: p o > •H T) CD C o c •H CO •H CO o u ^ fd c c a) c en o o •h n CO -P lTg o x m -H T3 CD -H CO E a rd CO O CD a p o o S3 rd 43 O M-l CD ^3 CD >i fd p CO 89 140 FSW 100 FSW 160 FSW 180 FSW 200 FSW ; n- I £3 ^ 100% (PERFECT ESTIMATE) Fig. 19. Average group estimates of eight time standards at four pressures. 140 o 130 80 p 1 FSW 100 FSW 180 FSW 200 FSW /.-■■^ lb 40 TIME IN MINUTES "60 W 20 Fig. 24. Swimming excursion profile two--used for eight man-dives . 100 60' SATURATION 75- 100- = 150 175 200" 30 40 TIME IN MINUTES 70 Fig. 25. Swimming excursion profile three — used for eight man-dives. 60' SATURATION 75' 100- 150 175 200- 10 20 3 40 50 TIME IN MINUTES 60 70 Fig. 26. Swimming excursion profile four — used for ten man-dives. 101 6T SATURATION 40 50 TIM IN MIXUTES Fig. 27. Excursion profile used for 13 submersible lockout dives. 240 to 250 feet. An excursion usually lasted 36 to 38 minutes between depart- ing from and returning to the hatch depth. The remaining 7-9 minutes of the permissible 45-minute excursion time was used during compression, opening and closing the hatch, storing the air hose and preparing for decompression. No symptoms of bends were experienced during any of the lock-out dives or during decompression back to the 60-foot storage depth. The divers were observed during the excursions by the submersible pilot and observer from the forward compartment and each dive was recorded on video tape. Several aquanauts reported some subjective feelings of inert gas nar- cosis. The degree of narcosis varied considerably but none of the aquanauts felt that it interfered with carrying out the tasks at hand. Biomedical Results : Medical Data Many of the divers developed multiple, white pustules of the skin, espe- cially over the back, chest, and upper arms. Bacterial culture of some of these divers showed the presence of Staphylococcus aureus consistently. Subject L.S. developed nausea, vomiting, diarrhea, and fever shortly after decompression from saturation. White-cell count and differential count were suggestive of a bacterial infection and a tentative diagnosis of staphylococcal 102 enteritis was made. Treatment consisted of intravenous fluids and kaopectate per os and recovery was uneventful. Subject S.E. became nauseated during the first 250-fsw lockout and vomited into the mouthpiece. On returning to the submersible, the subject became limp, experienced blurred vision, and again vomited. Recovery appeared to be complete within two minutes. A similar incident occurred the following day during the 250 fsw lockout and this subject was prohibited, on medical grounds, from further deep excursions and lockouts. No treatment was given other than rest and no further problems were encountered. Subject J. P. developed otitis media following decompression from satura- tion and was given tetracycline antibiotics per os. Subject J.H. collapsed shortly after returning to shore following decom- pression. He recovered sufficiently to walk, with assistance, to the on-site recompression chamber where a 60-fsw treatment table was started. The sub- ject continued to improve during the treatment and consumed several hundred milliliters of fluids consisting of orange drink and water. A tentative diagnosis was made of hypoglycemia and dehydration brought on by abstinence from fluid and food during the nearly 18 hours of decompression. Recovery was uneventful. Platelet Studies When the mean percent change in circulating platelet count of the divers was calculated for each sample day there were no statistically significant changes, although there was a trend for counts to be depressed slightly 24 hours post-saturation. When examined individually, four of the divers had reductions in platelet counts greater than 30%. In two of these (38% and 35%) , this occurred in the sample collected at saturation depth (60 fsw) after completion of all of the deep excursions and lockout dives. Subject J.H. , who was treated for decompression sickness as a precaution- ary measure, had a 32% reduction in the post-saturation sample and subject S.E. , who experienced difficulty during the lockout dives, had a 31% reduc- tion 24 hours after decompression from saturation depth. For reasons of logistics it was not possible to obtain control data for platelet aggregation on one team (four subjects) of divers. The remaining six, however, showed a marked and statistically significant reduction in sen- sitivity of platelets to ADP-induced aggregation in the sample collected dur- ing saturation but after completion of the excursion and lockout dives. Evi- dence of this trend was still present after decompression from saturation depth, becoming variable thereafter. The four remaining subjects showed a trend for aggregating activity to be increased in the post-saturation samples as compared to the ones collected during saturation, suggesting that the ac- tivity followed the same pattern as in the other six divers. 103 Hematology A slight (13.3% ±1.49 SEM) but statistically significant (P < .001) in- crease in the mean red-cell count 48 hours post- saturation was the only note- worthy change in red-cells, hemoglobin concentration, or packed-cell volume. No noteworthy changes in plasma enzyme levels occurred. Platelet Function Studies In three previous studies of divers using the Hydro-Lab habitat, signifi- cant reductions in circulating platelet counts were observed (Philp et al. 1974, Philp et al. 1975). On these occasions the saturation depth was 42 fsw and a different decompression profile was utilized. In the SCORE open- sea dive there was no statistically significant loss of platelets. By con- trast, reductions in platelet counts were marked and highly significant in the Duke SCORE Phase I experiments. These data indicate a relationship be- tween the risk factor for decompression sickness and the loss of platelets and further suggest that the SCORE open- sea excursion profile was the less hazardous of the two. Platelet aggregating activity, however, was depressed by the same order of magnitude in both situations. The possibility that the higher O2 exposures encountered in the SCORE Phase I experiment might have been a contributing factor to the platelet loss cannot be discounted. However, the fact that a marked and significant loss of platelets occurred following the 250-fsw bounce dive, a dive which was associated with a 100% incidence of skin bends (pruitis) but which had a bot- tom time of only 13 min. would argue that decompression stress (i.e. bubble formation) is the primary causal agent. Further details are discussed in Philp, Freeman, and Francey (1975). Summary : Phase II of SCORE clearly demonstrated the feasibility of conducting open- sea working decompression excursion dives on air to depths up to 250 feet from an air saturation storage depth of 60 fsw. The open- sea program further verified the excursion decompression schedules tested in the Phase I labora- tory program. If inert gas narcosis was present, it was not, in the opinion of aquanauts or observers, of sufficient magnitude to impair cognitive or psychomotor performance. The program also demonstrated the viability of com- bining habitat and submersible operations into a cohesive scientific effort. VI GENERAL CONCLUSIONS A number of general conclusions can be drawn, based on the analytical work, laboratory tests and field operations described in this report. 1. The use of gas-loading analysis of previous diving experience affords an excellent starting point for computation of new decompression procedures, 104 This approach has led to a matrix of limiting values (the NOAA OPS matrix) which has been used for computation of many of the decompression proce- dures reported here. 2. Evidence, to date, shows that saturated divers can work safely while breathing air at depths greater than those at which they could operate with equal safety from sea level. The extra depth, based on subjective impressions, is approximately equal to that of the habitat. This accom- modation to the higher nitrogen environment becomes effective in about one day, and reaches a maximum in two-to-three days. 3. Descending no-decompression air-excursion dives with depth changes up to 180 fsw have been made in the laboratory from saturation at depths to 120 fsw in a normoxic nitrogen atmosphere. 4. Air-excursions to depths of 250 fsw with bottom times up to one hour can be safely conducted from saturation at 60 fsw with appropriate decom- pression stops. 5. Air-excursions to 300 fsw from air-saturation at 60 fsw are unsafe due to the possibility of oxygen toxicity. 6. The practical limit for excursions with saturation normoxic mixtures has not been established but is not likely to be greater than 300 fsw. 7. Ascending air-excursions with operationally useful times and depths can be made safely from a nitrogen/oxygen storage mixture. Such excur- sions, however, are limited to about 60 fsw above saturation depth. 8. The risk of nitrogen narcosis is still a considerable problem at deeper depths and it is recommended that divers be selected for minimal sensi- tivity. An oxygen toxicity sensitivity test would also be advisable. 9. Only the most highly trained, competent and balanced individuals should be permitted to make excursions to 250 fsw and then only after thorough training on the equipment to be used and the tasks to be accomplished. No reliance should be placed on individual divers' comments as to their ability to function at such depths. 10. Efficient decompression from nitrogen/oxygen saturation can be ac- complished without breathing pure oxygen by mask. 11. The occurance of oxygen toxicity symptoms during bends treatment (SHAD II) suggests that an alteration occurs in some saturated divers that precludes their ability to accommodate to what would normally be a routine treatment procedure with 100% oxygen. 12. There is a point, apparently, in the range 0.5 to 0.6 atm oxygen partial pressure, where a change in red-cell production occurs but which is too low to invoke symptoms of oxygen toxicity. This adaptive process 105 can continue for many weeks and can result in severe debilitation on re- turn to sea level conditions. 13. A post-dive reduction in circulating platelet count following air- saturation has been confirmed. 14. Based on available evidence, air- saturation should not be conducted at depths beyond 60 fsw. 15. Evidence currently available indicates that normoxic nitrogen/oxygen saturation exposures can be conducted to depths of 120 fsw. The limit for such exposures, however, has not been established. VII APPLICATIONS OF SHALLOW HABITAT AIR DIVING The operational programs which have been conducted thus far, serve not only as steps in a broad development program, but also serve as outstanding examples of the applicability of shallow habitat excursion diving. For ex- ample, the SCORE operation which used decompression excursions, particularly showed that excursions can give scientists convenient access to greater depths more efficiently and for longer periods than had been possible previously. Scientific observations and experiments, resource survey and management, pol- lution analysis, archaeology and commercial harvesting, all are examples of missions which can be aided by the use of shallow excursion techniques. The recent expansion of the off-shore industry similarly offers various possibilities of using shallow excursion techniques. While many tasks require deep diving, there still is much work at depths less than 250 feet. The lay- ing of pipeline in this depth range is but one of the possible types of jobs. These and other potential applications depend, as do many areas of tech- nology, on trade-offs. To evaluate these techniques properly they must be compared with other options. The basic purpose of the programs described in this report were to reach open-sea work areas using vertical excursions from shallow saturation depths with air as the excursion breathing gas, and nitrogen as the sole inert gas. The traditional methods, by comparison, in- clude surface diving (with air or "mixed gas," e.g., helium-oxygen), and satu- ration without vertical excursions, (e.g., air or mixed gas saturation) at approximately the working depth. The shallow excursion technique permits longer work periods in the air diving domain, and because of accommodation to narcosis, it permits the use of air to be extended into the shallow end of the mixed-gas or helium domain. At the other end of the continuum, we have seen that relatively shallow work- ing dives can benefit from air-saturation. For example, the US Navy Diving Tables allow a 30-minute no-decompression dive at 90 feet, whereas a diver can spend a six-hour no-decompression excursion to this depth from an air saturation at 42 feet. To achieve approximately the same working time, using 106 USN Standard Air Decompression Tables, a diver would need to make three dives and three decompressions totalling about five hours and ten minutes. At 150 feet, one hour of work costs about two hours of decompression time (using US Navy tables) . Using helium (mixed-gas) , the depth can be extended, such that at 250 fsw an hour of work may cost three hours of decompression, and two hours' work requires nearly four hours of decompression. In contrast, from a saturation depth of 85 fsw a diver can make a six-hour excursion to 150 feet and return to the habitat with no decompression stops. Another factor to be considered is gas cost. For example, four hours of work at 250 fsw breathing a helium-oxygen mixture open circuit will require on the order of $200 worth of gas, more than ten times the cost of air. Thus the cost trade-offs depend on depth, work required, equipment availability and the cost of gas. A typical job requiring four to six hours per day, for several days, of work at 250 feet would clearly be more cost-effective using shallow habitat excursions. Existing closed-circuit equipment which works but which has not reached commercial acceptability due to complexity, reliability, and cost would per- mit the four-hour dive just mentioned to be performed with nominal cost for gas. Rebreathers have proven to be effective in scientific diving and will eventually be used more extensively by the working diver, although at the present time are very expensive. Another cost factor demonstrated in SCORE, SHAD II, and especially in the Hydro-Lab program is the use of an air-based habitat to depths of 60 fsw. When air is used as the storage gas, it can be easily vented, thus avoiding the cost of recirculating scrubbers and CO2 absorbent chemicals. Although it is cheaper by far and more available than helium, the cost of nitrogen must be considered in all but the shallowest air operations. The usefulness of the air-excursion technique is not limited to diving. Caisson and tunnel work may prove to be just as profitable an application. This suggestion was made several years ago by Behnke (1968) and again by per- sonal communication in 1974. As Behnke points out "The urgent requirement for Metropolitan rapid transit and conduits for waste disposal, power lines, etc. will necessitate large-scale subterranean (and subaqueous) pressurized tunneling. Current work in compressed air is not only prohibitive in cost but incurs as well decompression hazards, notably bone necrosis. The pres- surized Habitat and excursion principle should eliminate current decompres- sion problems . . .The pressurized Habitat should permit greatly augmented work- time attended by minimal decompression and elimination of decompression haz- ards." While tunnel workers would not be expected to spend long periods (one to two weeks) under pressure, a work schedule involving saturation of three to four days at depths of 30 to 40 fsw followed by a single decompression to the surface is certainly within the realm of practicality. At the present time, tunnel workers can spend two 45-minute periods each day at a depth of 112 feet with each period requiring a decompression of about 28 minutes. 107 By contrast , using the nitrogen/oxygen excursion tables, these same men could work for four hours at a depth of 100 fsw and return to a storage depth of 40 fsw with no decompression required. If such a work schedule were carried out for four days, the total work time per man would be 16 hours if only one such shift per day were done. This compares to seven and one-half hours a week using two 45-minute work periods. At the end of four days a single de- compression of about 11 hours from the 40 fsw saturation depth would be re- quired. Thus, over twice the amount of work would be achieved and only one decompression, instead of the ten now required during a typical five-day per- iod. Many variations on such a schedule could be made depending upon the re- quired working depths. In addition to the increased work output, the signi- ficant reduction in the number of decompressions should benefit the workers by reducing the immediate incidence of bends and the long term incidence of osteonecrosis. Concomitantly, insurance costs should go down because of the added safety margin. From an engineering standpoint, all that would be needed would be some type of compartmentation in the operational pressurized tube. VIII FUTURE REQUIREMENTS The shallow habitat excursion and subsequent field operations, culminat- ing in 1975 with the SCORE project have demonstrated new techniques of diving. This is just a start, however, and much more investigation is needed to give the underwater scientist, engineer, explorer and worker added working time and safety. Further studies should include the development of: 1. Longer decompression excursion times from both air and normoxic ni- trogen habitats. 2. Repetitive decompression excursion procedures, in which excursions can be computed taking into account previous excursions and habitat in- tervals . 3. Additional emergency surfacing procedures from saturation for depths in excess of 50 fsw. 4. An updated NOAA OPS matrix which includes experience gained since 1972. 5. New excursion procedures for use from an air or nitrogen habitat in which helium/oxygen is used as the breathing mixture. 6. Appropriate decompression procedures for the excursions mentioned in #5. 7. Maximum practical limits in such areas as: 108 a. Time-depth profile for air saturation exposures taking into ac- count oxygen toxicity b. time-depth profile for excursions on air c. saturation depth for normoxic (or other non-air) nitrogen habitat environments d. depth at which adaptation to nitrogen narcosis permits safe div- ing, both for air and nitrogen/oxygen mixtures 8. Treatment tables for use when oxygen toxicity is present. Such tables must consider the accumulated oxygen exposure and developing toxicity. 9. Finally, there is a need for further study of the phenomenon of "adap- tation" to nitrogen narcosis. 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Research report no. 6-65. U.S. Navy Experimental Diving Unit, Wash., D.C. 1>U.S. GOVERNMENT PRINTING OFFICE! 19 7 6-210-801/366 112 PE " N STATE UNIVERSITY LIBRARIES A000071510LJ30