7 'D-A48 300 MANNED TESTING OF TWO CLOSED-CIRCUIT

OXYGEN UNDERWATER i/il

I BREATHING APPARATU..(U) NAVY EXPERIMENTAL DIVING UNITI PANAMA CITY FL H J SCHWARTZ SEP 84 NEDU-13-84

UNCLASSIFIED F/G 6/1 NL

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O NAVY EXPERIMENTAL DIVING UNIT

qtt MANNED TESTING OF TWO CLOSED-CIRCUITOXYGEN UNDERWATER BREATHING APPARATUS:U.S. NAVY EMERSON RIG AND FENZY P0.68

CDR H. J. C. SCHWARTZ, MC, USNR

SEPTEMER 198

NAVY EXPERIMENTAL DIVING UNIT

ditrbtiz i's u .j-nd"

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*j~ -~- ~K. - F.

DEPARTMENT OF THE NAVYNAVY EXPERIMENTAL DIVING UNIT

PANAMA CITY, FLORIDA 32407 Its NuPw RWn To$

NAVY EXPERIMENTAL DIVING UNIT

REPORT NO. 13-84

MANNED TESTING OF TWO CLOSED-CIRCUITOXYGEN UNDERWATER BREATHING APPARATUS:U.S. NAVY EMERSON RIG AND FENZY P0.68

CDR H. J. C. SCHWARTZ, MC, USNR

SEPTEMBER 1984

Reviewed andSubmitted by: Reviewed by: Approved by:

LH.)J. C.* SCHWARTZ E. D. THALMANN FRANK E. EISSINGCDR, MC, USNR CDR, MC, USN CDR, USN

Senior Medical Officer Commanding Officer

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4. TITLE (and Subtitle) S. TYPE OF REPORT & PERIOD COVERED

MANNED TESTING OF TWO CLOSED-CIRCUIT OXYGENUNDERWATER BREATHING APPARATUS: U.S. NAVY FINALEMERSON RIG AND FENZY P0.68 6. PERFORMING ORG. REPORT NUMBER

7. AUTHOR(a) S. CONTRACT OR GRANT NUMBER(@)

CDR H. J. C. SCHWARTZ, MC, USNR0

9. PERFORMING ORGANIZATION NAME AND ADDRESS 1q. PROGRAM ELEMENT. PROJECT. TASKAREA A WORK UNIT NUMBERS

'NAVY EXPERIMENTAL DIVING UNITPANAMA CITY, FL 32407-5001

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SEPT 198413. NUMBER OF PAGES

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ISa. DECLASSIFICATION/ DOWNGRADINGSCHEDULE

16. DISTRIBUTION STATEMENT (of Shia Report)

Approved for public release; distribution unlimited.

17. DISTRIBUTION STATEMENT (of the abotract ontered in Block 20, iI different from Report)

III. SUPPLEMENTARY NOTES

It. KEY WORDS (Coninfue on reverse side If neceeoory end Identify by block number)

SELF-CONTAINED UNDERWATER BREATHING APPARATUS (SCUBA)OXYGEN CANISTER DURATION EMERSON RIGCARBON DIOXIDE GRADED EXERCISECLOSED-CIRCUIT BREATHING RESISTANCEOXYGEN TOXICITY FF.NZY PO-6R

20 ABSTR4ACT (Coe.nu on see~ ide it neceaery and Identify by block nuanber)

The breathing characteristics of two types of closed circuit oxygenself-contained underwater breathing apparatus at a pressure equivalent to 30feet of sea water were studied in the Ocean Simulation Facility of the NavyExperimental Diving Unit. Breath-by-breath curves of inhaled and exhaledoxygen and carbon dioxide levels and inspiratory/expiratory pressure curveswere recorded. For the first type, the U.S. Navy Recirculating UnderwaterBreathing Apparatus, Closed-Circuit, Oxygen (Emerson Kig), the carbon dioxide

DO I AN3 1473 EDITION OF I NOV 65 Is OSOLETE ULASFE

S N012 LF.04661SECURITY CLASSIFICATION OF THIS PAGE (When Dale Eftf*PO)

% I. . E 1 1 II J . - . E * E I-

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SECURITY CLASSIFICATION OF TH~IS PAGE (Who* Does Entae.

absorbent canister duration at 70*F (21*C) exceeded the arbitrary cutoff of240 mintues with diver-subjects doing moderate work; at 40*F (40C) thecanister duration vas 199 minutes. For the second type, the Fenzy P0.68, thecanister duration at 70*F (210C) was 95 minutes, and no studies were done at40OF (40C). Both types were able to support divers doing hard work. Fivecases of oxygen toxicity were seen, including three-.divers with mild symptoms,one with a near-convulsion, and one with a convulsion.

UNCLASSIFIED

SECURITY CLASSIFICATION OF TH4IS PAGEf1Thof Doea Entered)

*~..% *.** **** *.* ****i.*. . . . . . . . . . . . . . . . . . . . . . . . .

ABSTRACT

The breathing characteristics of two typqs of closed circuit oxygenSelf-contained Widerwater t~ahn partsiat a pressure equivalent to 30

*feet of sea water were stud ed in thd Ocean Simulation Facility of the NavyExperimental Diving Unit. Breath-by-breath curves of inhaled and exhaledoxygen and carbon dioxide levels and inspiratory/expiratory pressure curveswere recorded. For the first type, the U.S. Navy Recirculating UnderwaterBreathing Apparatus, Closed-Circui, Ox en (Emerson Rig), the carbon dioxideabsorbent canister duration at 70 411 (21 4) exceeded the arbitrar; cutoff of240 mintues with diver-subjects doing moderate work; at 40F (4 C) thecanister duration was 12minutes. For the second type, the Fenzy P0.68, the

caPiter duration at 70 F (21'C) was 95 minutes, and no studies were done at40 FPI Both types were able to support divers doing hard work. Fivecases of oxygen toxicity were seen, including three divers with mild symptoms,one with a near-convulsion, and one with a convulsion. .- 5./1d/

. . . . . .. ..

ASion For0-'Y WORDS~• NT.S GRAM

The bU announced '

Self-Contained Underwater Breathing Apparatus (SCUBA). r uiaeto 0 - .

feetof sa waer wre su~edin te'Ocan Smulaion acil t ot a

,OxygenCarbon Dioxide oClosed-Circuit Vt N y R c uUd r t

Oxygen Toxicityde ,t.Canister da2ration,) 7 h

-- ;raded Exercise, i -Av.

Breathing esistance -onFenzy P0.68

Emerson Rig

40F,- oh yps ee bl t upor dvesdonghadwok.Fle:".ii: "

cass f xygn oxcit wresee, ncudig hre dves ithmid ympom, ::i" :S

....................................................... ........................ . .....

Manned Testing of Two Closed-Circuit Oxygen Underwater BreathingApparatus: U.S. Navy Emerson Rig and Fenzy P0.68

IJINTRODUCTION

The U.S. Navy Recirculating Underwater Breathing Apparatus, ClosedCircuit, Oxygen (Emerson Rig or Emerson UBA) has been in use since 1963 and isscheduled for replacement. Several closed-circuit oxyger Underwater BreathingApparatuses (UBA's) are being considered as the replacement for the EmersonUBA. One of the units being considered is the Fenzy P0.68 produced by LaSpirotechnique I.C. Industrielle et Commerciale (06510 Carros Industries (T),France.) It offers the advantages of lighter weight, 15.5 lbs compared with35 lbs for the Emerson UBA, and commercial availability, whereas the Emerson

ak UBA is no longer manufactured.

Unmanned testing of the Fenzy P0.68 at the Navy Experimental Diving Unit(NEDU) in 1981 (1) showed that it had slightly better breathing characteris-tics than the Emerson UBA when measuring total breathing resistance and workof breathing. The canister duration was significantly shorter than theEmerson UBA.

In addition to testing the characteristics of the UBA's, a goal of thestudy was to evaluate diver performance at a pressure equivalent to 30 feet of

sea water (FSW) breathing 100 percent oxygen. The current U.S. Navy DivingManual (2) limits the use of oxygen UBA's to 45 minutes at 30 FSW due tocentral nervous system (CNS) toxicity. Some evidence suggests that such anexposure limit may be too conservative. Donald (3), in 1947, reported twoconvulsions in 20 exposures of resting divers to 30 FSW breathing 100 percentoxygen for up to 2 hours. The level of inspired carbon dioxide, which appears

to affect oxygen toxicity, was not reported in this wartime study. In aprevious NEDU study in 1953, no cases of CNS oxygen toxicity occurred at 30

FSW in 11 subjects breathing 100 percent oxygen for 57 minutes (4). Theconditions which provoke symptoms of oxygen toxicity have been the subject ofsubstantial investigation in the past several decades. Factors which areknown to increase individual sensitivity to oxygen toxicity include anelevated inspired carbon dioxide, low temperature, immersion, and work. Therelative contribution of each of these factors is unknown.

This report describes the results of a series of manned dives at the NEDUOcean Simulation Facility (OSF) in November and December 1981 (NEDU Test Plan81-53.) Graded exercise studies and canister duration studies were done withboth UBA's which were instrumented to study breathing gas composition.

MATERIALS AND METHODS

The studies were carried out during 30 dives in the wet pot of the OSF.The chest level of the Diver-Subject was at a depth equivalent to 30 FSW.Standard Emerson UBA's and Fenzy PO.68's were used, but both were modified touse an external oxygen supply by means of a whip connected to a 72 cu. ft.oxygen cylinder. Divers breathed via the standard closed circuit mouth-

pieces. Both UBAs are described and illustrated in reference (1).

. . ... . . . . . - -

Two water temperatures were used. For the 40*F (4.4*C) studies, eachdiver wore a crushed foam neoprene dry suit with Thinsulate undergarments, theU. S. Navy Passive Diver Thermal Protection System. For the 70*F (21.1*C)studies, each diver wore a 1/4 inch neoprene wet suit.

Emerson UBA

The Emerson UBA consists of an oxygen supply bottle, an oxygen add valvewhich provides for a continuous flow and a manual add bypass, a double hosebreathing circuit with one way valves, two breathing bags, and a canister toremove C02 containing 6 pounds (2.7 kg) HP Sodasorb.

Fenzy P0.68

The Fenzy P0.68 is similar in function to the Emerson UBA with severalsignificant differences in design. The oxygen add valve is a demand typelocated in the single breathing bag, and the canister contains 3.7 pounds (1.7kg) HP Sodasorb.

Subjects

The Diver-Subjects were seven U.S. Navy divers, ranging in age from 20 to37 years. Each had passed a standard USN oxygen tolerance test prior tobeginning diving training. The divers were well conditioned and prior to theexperimental series were capable of running 8 km per day and pedalling 175watts for 8 minutes on a dry bicycle ergometer. The Diver-Subjects werecarefully instructed about oxygen toxicity and were drilled in emergencyprocedures in the OSF wet pot. During the training period, they made testpool dives with both the Emerson UBA and the Fenzy P0.68 for thoroughfamiliarization.

Instrurnentation

Gas samples from the UBA canister effluent and from the mouthpiece wereobtained by capillary sample lines equipped with micrometering valvespositioned as close to the sample point as possible. After passing throughthe micrometering valve, the vas sample left the UBA and went through anunbroken I mm I.D. sample line to the gas analysis station outside of thechamber. The delay time to the surface was less than 2 seconds which providedrapid response to variations in gas composition without significant mixing inthe sample lines. The gas samples were analyzed for P02 and PCO2 with a massspectrometer (Chemetron Medspect 2.) Breath-by-breath curves from themouthpiece were recorded on an 8 channel strip chart (Grass Polygraph Model7-162-40.)

The inspiratory/expiratory pressure differential (4P) was measured at themouthpiece of the UBA by a differential pressure transducer (Validyne DP-9with a 5 psi diaphragm) referenced to ambient water pressure at the level ofthe sternal notch. The transducer was calibrated by a water manometer beforeeach study. The AP was recorded on the strip chart. Canister outlet P02 andPC02 were recorded both on the strip chart and on a computer (Hewlett PackardModel 1100.) Other recorded functions included heart rate, oxygen supplybottle pressure, and for the dives in 40*F water, rectal temperature.

2

Pulmonary function tests were performed on each diver immediately before andafter each canister duration test.

Experimental Procedures S

The experiment was divided into two parts; the first part consisted ofCO2 absorbent canister duration studies, and the second part was gradedexercise studies. Any given Diver-Subject did not do both parts of the studyon the same day. Diver work rate was provided by a specially designed-electronically braked pedal mode ergometer (Warren E. Collins, Braintree,MASS) modified for submerged use (6). During the canister duration study, theDiver-Subject pedalled the ergometer at 50 watts for 6 minutes and rested for4 minutes, repeating the sequence until the canister effluent PCO2 reached7.6 mmHg (1% SEV), or for a maximum of four hours, whichever came first. Thegraded exercise study consisted of 10 minutes of rest followed by 7 cycles of6 minutes work and 4 minutes rest. The work rates were 25, 50, 75, 75, 100, .125 and 150 watts respectively. Diver-Subjects all pedalled at 55 to 60revolutions per minute. Previous studies using similar methods showed anestimated oxygen consumption while pedalling at 150 watts of approximately 3liters per minute (7). The ergometer was mounted on a horizontal frame sothat the Diver-Subject was approximately in a swimming position (prone orslightly head up)..

Standard U.S. Navy purging procedures were done at the beginning of eachdive to obtain an inspired oxygen concentration of at least 95%. The gassample micrometering valve was adjusted to give continuous gas flows ofapproximately 350 to 700 cc (actual) per minute). Continuous gas sampling -

rapidly increased the oxygen concentration to over 98%. Divers were told tonotify control immediately if any symptoms of oxygen toxicity occurred. Anair breathing standby diver accompanied each Diver-Subject.

RESULTS

UBA Breathing Characteristics

Canister breakthrough is defined as the time at which the canistereffluent PCO2 reaches 3.8 mmllg (0.5% SEV). When possible each test wascontinued beyond canister breakthrough to a PCO2 level of approximately 7.6mmlig (1% SEY) in order to more easily measure the end point. Therefore, thetime on 100 percent 02 exceeds the canister breakthrough time except whencanister breakthrough had not yet occurred when the study ended. At 70*F,three runs were stopped at the arbitrary 4 hour cut-off, and two runs werestopped by symptoms of oxygen toxicity. At 400F, one run was stopped due to asymptom of oxygen toxicity, and one run was stopped by ergometer failure.Table 1 gives the results of 5 warm and 6 cold water canister duration studieson the Emerson UBA.

Table 2 gives the results of the 4 canister duration studies using theFenzy P.68 in 70oF water. The time on 100 per cent 02 is longer in all cases..than the canister breakthrough time for the reasons noted above.

3

• •.....

Figures 1, 2 and 3 illustrate the average canister durations for theEmerson UBA at 700F, at 400F, and for the Fency P0.68 at 70OF respectively.Mean canister effluent PC0 2 in Z SEV + one standard deviation is plotted at 50minute intervals. An additional 25 m-nute value is plotted for the FenzyP0.68 study.

Table 3 gives the results of the 5 graded exercise studies at 70F usingthe Emerson UBA. Several data points were not recorded due to plugging of thecapillary gas sample line from the mouthpiece by saliva. Table 4 is similarto Table 3 and gives the results of the 6 studies done at 40°F. Table 5 is 0also similar to Table 3, and gives the results of the four studies done on theFenzy P0.68 at 700F.

Table 6 summarizes the average time and standard deviation of thecanister duration studies. The study was stopped arbitrarily at 4 hours andin that time no canister breakthrough was observed in the Emerson UBA at 70°F.In those 3 runs which were stopped arbitrarily, the average canister outletPC02 in SEV at 4 hours was 0.36% + 0.04%.

Oxygen Toxicity

The five cases of oxygen toxicity encountered during the 30 dives of this pstudy are listed in Table 7. There were three Diver-Subjects who had minormanifestations and two who had major symptoms of oxygen toxicity. In the"near-convulsion", the subject noted dyspnea, fatigue, and tunnel vision nearthe end of a graded exercise. He stood up, rapidly climbed several steps ofthe wet pot ladder, stopped, began breathing chamber air, and appeared unableto speak for several minutes. He continued climbing out of the wet pot withhelp, spoke with the Medical Officer and lay in a chamber bunk. Within tenminutes he became lethargic, and remained hard to arouse for two hours. Heremained amnesiac for the events from the onset of symptoms until waking inthe bunk. The event had many characteristics of a convulsion, especially thepost-ictal lethargy. However, there was no definite rigor, and therefore wascalled a "near-convulsion". p

The other major symptom also occurred toward the end of a gradedexercise. The Diver-Subject stopped pedalling and ascended two steps of theladder. He then had a generalized convulsion with tonic-clonic movements ofall extremities, lasting one minute. Within eighteen minutes, he was able torecall events before and after the convulsion, but had trouble releasing hisright hand grip. The inspired PCO2 was approximately 1% SEV at the time ofthe convulsion, which was the highest PC0 2 observed for any Diver-Subject atthe time of symptoms.

No diver had any sequelae following symptoms.

4

- . . . .. 7. : K>:: Kc-1115 9 * .. °.:

DISCUSSION

UBA Breathing Characteristics

The Emerson UBA performed reliably, was able to support a diver doinghard work, and had long canister durations with a predictably flat curve ofnear zero canister outlet PC02 until near the time of canister breakthrough.

The Fenzy P0.68 had a very short canister duration and extremevariability between dives, even when the canister was packed by the same 0individual. Although the UBA supported a diver doing hard work, elevatedinspired (canister effluent) PC02 early in the sequence of graded exercisessuggested a problem with channeling in the canister. The Fenzy P0.68 canisterholds only 3.7 pounds (1.7 kg) of HP Sodasorb compared with the Emerson UBAcanister which holds 6.0 pounds (2.7 kg), which may explain some of thedifference in performance. Other design differences such as shape and flow Bpath which are known to affect canister performance were not evaluated. Theshort canister duration at 70*F resulted in a decision not to test the UBA at400F, since HP Sodasorb is less effective at colder temperatures.

Oxygen ToxicityA

The onset of oxygen toxicity symptoms has been shown in the past to berelated to higher P02 , higher inspired PC02 , higher work rate, immersion inwater, and to undefined individual susceptibility factors. These factors wereexamined in the present study. The effect of inspired P02 at 30 feet wascompared with a previous study conducted using a Draeger LAR V 100% 02rebreather which used very similar methods to the present study except for the ....shallower depth of 25 FSW (5). In the previous study, 12 canister durationdives were performed with mean durations of 226 + 23 minutes at 700F, and 124+ 9 minutes at 400F. Only one Diver-Subject had symptoms of tinnitus, andThat case was not regarded as a true oxygen toxicity symptom. Twelve gradedexercise dives were performed, with no symptoms noted.

No clear trend regarding inspired PC02 was seen in the present study.During the graded exercise studies with the Fenzy P0.68, one subject had a ...convulsion; his inspired CO2 was 8.1 mmHg which compared with the three othersubjects who did not convulse and had inspired C02 levels of 9.12 mmHg, 1.5mmHg, and 3.8 mmHg.

Higher work rate appeared to be related to earlier onset of oxygentoxicity symptoms in the present study. The two cases of the most serioussymptoms occurred during graded exercises at work rates of 100 watts and 150watts, and times of 59 minutes and 83 minutes respectively. The three othercases of symptoms occurred during 50 watt canister duration studies at 152 ""minutes, 165 minutes, and 220 minutes, and all three were milder symptoms. -The udde range of times to symptoms and the lack of symptoms during most divestends to confirm the wide individual susceptibility to oxygen exposure thatothers have noted.

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The present limit in the U.S. Navy Diving Manual for oxygen diving at 30FSW is 45 minutes. This limit appears appropriate for divers doing hard work

since the earliest symptom in the present study, a convulsion, occurred at 59minutes during a high work rate. At moderate work rates the earliest symptom

occurred at 152 minutes, suggesting that at moderate work rates the present ."

limit is conservative and could be extended.

SUMMARY

In summary, both the Emerson UBA and the Fenzy P0.68 were able to supportworking divers at 30 FSW. The Emerson UBA had a canister duration of

approximately 2 1/2 hours at 40*F (4*C) and in excess of 4 hours at 70*F

(210 C). The Fenzy P0.68 had a very short and inconsistent canister duration

time.

Five cases of oxygen toxicity symptoms were observed including one

convulsion and one near convulsion.

6

p|

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.. . . . ... .. . . . . . . ..- .

REFERENCES

01. Middleton, J.R.; Unmanned Evaluation of Six Closed-Circuit Oxygen

Rebreathers, Navy Experimental Diving Unit Report No. 3-82, July 1982.

2. U.S. Navy Diving Manual, Vol. 2, Revision 1, U.S. Government PrintingOffice, Washington, D.C. 20402, p. 14-2, July 1981. 0

3. Donald, K.W.; Oxygen Poisoning in Man, British Medical Journal, Vol. I,No. 5, 1947, pp 667-719.

4. Lanphier, E.H., and Dwyer, J.V., Jr.; Diving With Self-ContainedUnderwater Breathing Apparatus, Navy Experimental Diving Unit ReportNo. 11-54, April 1954.

5. Piantadosi, C.A.; Evaluation of Modified Draeger LAR V Closed-Circuit SOxygen Rebreather, Part II: Manned Testing; Navy Experimental DivingUnit Report No. 5-79, August 1979.

6. James, T.W.; Modified Collins Pedal-Mode Ergometer: Development and -

Medical Tests, Navy Experimental Diving Unit Report No. 1-76, June S1976.

7

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TABLE 1. SUMMARY OF CANISTER DURATION STUDIESAT 30 FSW

EMERSON UBA

Canister

Effluent

Time On Canister Breakthrough PCO2

100% 02 Time (Min to 0.5% (%SEV) atDiver (*Note) (Min) PCO2 SEV) Completion

70*F (210C)

A (1) 250 >250 0.345%

C (1) 254 >254 0.405%

D (1) 244 >244 0.345%

E (2) 153 >153 0.045%

F (2) 227 >227 0.250%No Breakthrough

Mean 226 ±42 NotedI _______________________

40OF (40C)

A 205 166 1.05%

D 196 143 1.34%

E 201 1701.4

F (3) 215 ______ ___ 0.28%

G 205 181 1.32%

H (2) 174 143 0.78%

Mean 199 ±14 161 ±17

*Note: (1) Stopped at arbitrary limit of 4 hours at work.(2) Stopped due to 02 toXicity Symptom.(3) Stopped work due to ergometer failure; diver then

remained at rest for 37 minutes; canister breakthroughdid not occur.

8

. .. . . . . . . . . . .. . .

TABLE 2. SUMMARY OF CANISTER DURATION STUDIESAT 30 FSW

FENZY P0.68 0

CanisterEffluent0

Time On Canister Breakthrough PCO2Diver0 Time (Min to 0.5% (%SEv) at

Diver___(Min) PCO2 SEV) Completion

70OF (210C)

D First Run 145 102 1.00%

D Second Run 89 22 1.05%

E 37 14 1.10% .

F 104 35 1.28%

Mean 95±45 43±40

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TABLE 6. AVERAGE CANISTER DURATION TIME TO 0.5Z SEV

EMERSON RIG FENZY P0.68

70OF (210C) >240 Mini 43 + 40 Mini

40*F (2C) 161 +17 Mini

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