Behaviora1ESectiveness j s 1 at N ATA

Jaseph P. O'Rcllly CINCUI.ATII .'Q COPY Sea CI a,",, ~asilory

IIKH A VIORA L F FFFCTIV 5,'NESS AT l6 ATA

JosephP, O'Reilly

Report,on SeaGrant project, Human perlortnancein the Sea R/32 - 01j.

SeaGrant TechnicalReport V N II l I-SF. AG RA NT- TR-73-0 l April, l 973

Thiswork is a resultof researchsponsored by !VOBISOffice of SeaGrant, Department of Commerce,under Grant iN'o. 2-35243 and Stateof HawaiiAiarine .Affairs Coordinator's Office, lask Order 3, 7971!. 77te .~.S,Government is authori=edto produce.and distri- butereprints for governmentalpurposes notu ithstamling any r opy- right notations tlrat may appearhereon. ACKNOWLEDGEMENTS

The author wishes to recognize the numerousindividuals who assisted this study by offering both ideas and equipment, particularly: Mr. Frank

Ahern, Dr. Meric Ansberry, Dr. Nathan Burbank, Dr, Robert Cole, Dr. Louis

D'Avanzo, Dr. Suk Ki Hong, Mr, Al May, and Dr. Terence Moore. Additionally, the project would have been seriously handicappedwithout. the invaluable extra effort offered by the dive team members: Mr. William Berryman, Mr.

Cyrus Carey, Mr. Gary Chiswick, Mr. Edwin Hayashi, Mr. James Morlock, and

Mr. Ben Respicio. TABLE OF CONTENTS

Page

INTRODOCTIPN

METHODS 13

RESULTS 29

DISCUSSION S4

COXCLuSIOVS 62

APPENDIX 63

REFERENCES 69 I NTRODUCTI ON

Exploration and potential colonization of the ocean bottom have

received international interest, as population pressures and resource

demands increase. Experimental programs such as SEALAB, Man in Sea,

Conshelf, Tektite, and Makai Rangehave demonstrated the feasibility of

saturation diving, at least in terms of maintaining life support at depth, while effectively increasing functional underwater work per hour of decom- pression. While such projects have established that divers can operate in

He-02 environments to depths of 2000 feet COMEXchamber dive, L972!, inves- tigations of human performance in hyperbaric environments have failed to keep pace with technological capabilities.

To insure diver safety and effectiveness, there is considerable need

for increased documentation of performance capabilities under hyperbaric

conditions, Typical exploratory programs have provided only casual in for- mation on the behavioral effectiveness of divers in mixed-gas environments,

and these reports have tended to yield conf li cting, often contradictory, observations.

Inert-Gas Narcosis

Although respiratory embarrassment, thermoregulatory losses, muse]e tremor, and convulsions contribute to performance loss under pressure, it

is generally recognized that the narcotic or intoxicating effect attendant with breathing inert gases under pressure is a primary cause of observable behavioral changes. The etiology of narcosis appears to be increased par- tial pressure of the inert gas interrupting synaptic transmission in the

central nervous system NS!, possibly augmentedby a synergistic increase in tissue C02 tension associated with changing P level and density of the 02 breathing mixture Bennett 4 Elliott, 1969; Hesser, Adolfson g Fagraeus,

1971! . Performancedecrements have been reported consistently during exposure to compressedair above4 ATA pressure Adolfson, 196S; Adolfson g hfuren,

1965; Albano, Criscuoli 5 Giulla, 1962; Baddeley, 1966; Baddeley f, Flemming,

1967; Bennett, 1963, 1966, 1967, 1971; Case 5 Haldane, 1941; Criscuoli

Albano, 1971; Frankenhaeuser,Graff-Lonnevig 4 Hesser, 1963; Kiessling 5

Maag, 1962; Shilling F Willgrube, 1937!. Significant performance loss attributable to nitrogen narcosis has been demonstrated at press~res as low as 2 ATA Poulton, Catton g Carpenter, 1964!. The existence of nitrogen narcosis is well documented, although some disagreement exists over the severity of narcotic effects at various depths, with different measurement instruments, and between ocean and chamber conditions.

information concerning the narcotic effect of helium is far less con- sistent. While there is someevidence of narcosis with hyperbaric He-02 at pressures as low as 7 to 10 ATA Baddeley g Flemming, 1967; Thomas,

Walsh 5 Bachrach, 1971!, other investigators have found no appreciable narcosis at depths as great as 36 ATA Bennett g Towse, 1971; Biersner,

1971; Biersner f Cameron, 1970; Bowen, Andersen g Promisel, 1966; Brauer,

1968; Brauer, Way, Jordan 5 Parrish, 1971; Fructus, Brauer g Naquet, 1971;

Hamilton, 1966; Hamilton 5 Fructus, 1971; Summitt, Kelley, Herron 5

Saltzman, 1971; Weybrew5 Parker, 1968!.

He-02 Muse!e Tremor

A consistent behavior problem noted with early studies using hyperbaric

He-02 was loss of motor ability, characterized as muscle tremor, balance disturbances, and loss o f coordination Bennett, 1966! . A "high-pressure nervous syndrome" HPNS! has been postulated Brauer et al., 1971! to account for neuromuscular imPairment rePorted at depths ranging from 10 tp 31 ATA e.g.: Bennett, 1965, 1966; Bennett 4 Dossett, 1966; Bennett p Towse, 1971,

Buhlmann, Matthys, Overrath, Bennett, Elliott g Gray, 1970; Hamilton,

Maclnnis, Noble 5 Schreiner', 1966!. Bennett 967! has suggested that helium tremor was caused by raised CO2 tension due to rapid compression and high PO Rate of compressionapparently affects helium tremors, since 2 several studies reported negligible tremor with slow rates Bachrach, Thorne g Conda, 1971; Brauer, 1968; Cabarrou, 1966; Hamilton, 1966; Schreiner,

Hamilton, Noble, Trovato 5 Maclnnis, 1966; Weybrew, Greenwood g Parker,

1964! ~

With muscle tremor effectively eliminated, most studies have reported little significant behavioral impairment with He-Oz saturation diving to 60

ATA. However, most of these dives have concentrated on physiological and technological considerations as new limits for depth and endurancewere attempted. Psychologicalexperimentation has been relatively restricted, and has failed to generate a systematic approachfor the interpretation of results or adequate standardization of tasks necessary for comparative evaluations. While psychological investigations of helium narcosis have provided equivocal results, there is sometheoretical basis for anticipating a size- able narcotic effect with hyperbaric He-02. Bennett, Poulton, Carpenter

Catton 967! note: "The most widely held view is that the minimumpressure of air likely to producean effective deteriorationof performanceis at 1.00ft ata abs!. Basedon calcula- tions comparingoil-solubilities, a similar level of narcosis maybe expectedwhen breathing oxygen-helium at about 400 ft 3.1 ats abs!" p. 54!. Narcosis and Task Complexity

Although the diversification of measurements employed in studies o f

inert gas narcosis has been distinguished only for its lack of standardiza t ion, there is considerable evidence that narcotic effects vary with the task chosen. Several studies of nitrogen narcosis have reported the amount of observedbehavioral decrement to be a direct function of task complexity Baddeley,deFigueredo, Curtis 5 Williams, 1968,'Case 5 Haldane, 1941; Kiessling g Maag,1902; Shilling 6 Willgrube, 1937!. Additional studies utilizing nitrous oxide N20! as the narcotic agenthave also demonstrated that themore neurologically complex the task, the greater the degreeof performanceimpairment with increasednarcosis Biersner,1972; Di ckson, Lambertsen 5 Cassils, 1971! . Thereis lessevidence that severity of heliumnarcosis is similarly relatedto performanceloss, but recentuse of a sensitive,complex behav- ioralschedule with lower animals has provided quantifiable measures of per- formanceloss with lie-02, even at suchlow pressures as7 and10 ATA Thomas 5 Bachrach,1971; Thomas, Walsh g Bachrach,1971! .

TheNeed for Systemati c Inquiry Giventhe disparity of resultsconcerning inert-gas narcosis, several reviewershave suggested that the selection of narrowlydefined measures maybe inappropriate to determine theexistence of narcosis Jennings, Walsh5 Bachrach,1971! . An evaluativemethod that considersthe overall behaviorofthe organism would bemore able to exposeanysystematic effect~ onperformance. Thus,the existence of narcosis might be recognized asa systematicchange in a varietyof behaviors,rather than an in a randomlychosen activity. Kiessling and Maag962! presenteda rationale for a hierarchical schemeof behaviororganization based on their observationthat during nitrogen-inducednarcosis, more complex behaviors were depressed earlier and to a greater degreethan simpler tasks. Similar results have been demonstratedfor mentaldeterioration occurring with hypoxia McFarland, 193S! and depressantdrugs Steinberg, 1954!. Introducing his conceptionof a behavioralapproach to the study of inert-gasnarcosis, Jennings 968! speculatedthat as behavior complexity increases, the disruptive effects of nitrogen should increase. !/is system- atic approachwas based on a hierarchicalorder of behavioralfunctioning, suchthat well-established operant responses e.g., habit! representeda very low level of behavioral complexity, while such cognitive processes as problem solving were consideredto be behaviorally far morecomplex. The present study attemptsto apply systematicbehavioral methodology to the analysis of performanceunder helium narcosis. It was hypothesized that a behavioral hierarchy, such as that postulated by Kiessling and Maag, and by Jennings, doesexist; and, i f Bennett's 966! assumption of synaptic transmission blocking accurately defines the phenomenonof narcosis, there should be a direct relationship between the level of task complexity or V'9 involvement! and the degree of performance impairment. noted with increased pressure.

A Model for Behavi oraI Anal ys i s

In developing a systematic behavioral approach to the study of narcosis, the present study utilized measurementtasks varying along a dimension roughly equivalent to the degree of neurological complexity considered to he operating in the various stages of human information processing, since the functional contribution of a diver to an ocean system is heavily dependent upon his information-processingcapabilities.

For ease in analysis, the information-processing model developed w~ consideredto be comprisedof several arbitrarily labeled processingstages

reflecting increasing levels of neurological complexity. Measurementtask

were then selected for these hierarchical levels of behavior, each task

demandinga different degree of ChISinvolvement. A fundamentalerror in earlier studies wasthe failure to recognize variousdegrees of cortical involvementrequired for the behaviors under consideration.While narcosis has been identified with lossof cognitive functioningand motor deficit, therehave been few systematic attempts to determinethe degreeof performanceimpairment on various tasks as a func- tion of neurologicalcomplexity. The present study was initiated as a first stepin thedevelopment of a systematicapproach to the studyof helium narcosis;it doesnot endeavor to isolate precise cognitive components, but concentratesona hierarchicalranking of severaltasks commonly employed in narcosisinvestigations. Analogously, noattempt will bemade to justify themodel on existing neurological structures; its functionis onlyto deli- neatethe sequence of cognitive involvement thought to beoperating in the rangeof humanbehaviors. Consideration of ontogenetic developmental sequencesalsoprompted theselection of thevarious stages, providing a measureof response complexity and,by implication, the degree of CNSin- volvement. Forpurposes of discussion, theinformation-processing modelwas devel- opedonfive levels: Sensory Transduction, ArousalLevel, Skill Acquisition ~ Memory,andDecision-Making. ~ Sensoryprocessing is thought to be basic to all levelsof informationacquisition and learning; it is classifiedas thelowest order ofcomplexity, although ChISfunctioning is recognized as contributingtoall information operations beyond themost rudimentary se» y reporting and fundamental reflexes. ~ Arousal level vigilance state! and attention are classified as the next most complexbehavioral responses, based on the nature of the Reticular Activating System, which next influ- ences information-gathering. ~ Skill acquisition or motor learning!, in- volving sensory and perceptual components as well as a complex gradation of muscle responses and components of memory and learning, is considered next most behaviorally complex. ~ Memory encompasses several information- processi~g operations, two of which will be differentiated in this model: short-term memory and long-term memory. Both stages are intimately related to learning and decision-making, but short-term, or immediate, memory is primarily concerned with instant-storage capacity and limited-duration retrieval. Long-term, or associative, memory requires awareness and rehear- sal rote learning! and has more advanced storage and retrieval properties.

e Decision-making, or reasoning ability, is considered to involve components of all other processing stages and substantial cerebral activity; it is viewed as the highest order of behavioral complexity in the information- processing model.

Sel ecti on of Tasks

Several tasks were chosen as representative of the various levels of

the behavioral model, with primary interest placed on the later stages re-

quiring complex neurological activity. Corresponding to the five-stage

model are five categories of responses: sensory, react.ion time, psychomotor,

memory, and cognitive functioning. A sixth category, personal ity measures,

was added, reflecting the individual's capacity to moderate his information

processes. Personality variability should affect complex cogni tive processes

more directly than such functions as gross motor activity. Sensory Measures

Visionand hearing were selected as sensoryareas of principal concern, althoughother sensory capacities particularly vestibular functioning have beenfound to be affected by compressionand/or decompression{Rubenstein p

Sumaitt, 1971!. Visualacuity measures were not considered,due to the extendedtrain- ing andbottom times required. However, a recent study has reportedno changein visualacuity, Titmus stereopsis, intraocular pressure, accommoda- tion,and exophoria withincreasing concentrations of N2D Biersner, l972!, indicatingat the least that narcosis without accompanying pressure change fails to alter mostvisual functions. Studiesofperceptual narrowing have indicated significant changes in peripheraldetection with increased stress, particularly when associated withanxiety during simulation dives Weltman 5 Egstrom, 1966; Weltman, Smith5 Egstrom, 1971!. In preparation for stress comparisons onfuture wetdives, it wasdecided tomeasure peripheral-field changes asaffected bypressure. Assessment ofdepth-perception changesafter continued expo- sureto limitedvisual fields was also included. Auditorychanges inhyperbaric environments arecomplex, based on shiftingsound spectra under pressure andaltered transmission medium How- ever,no permanent hearing shifts have been noted in diversand submariners withconsiderable hyperbaric experience Coles,l963; Shilling 6 Everley. l952!,with the rare exception ofoccasional bilateral hearing losses of obscureorigin Harris, 197l!. Some hearing shiftis expected underPres sure,aIthough thereis littlemiddle-ear hearing loss Adolfson 6 F»ur~ 1967!.Fluur 5Adolfson {1966!report threshold elevations of 30 4odb inmiddle-frequency hearingrangeunder He-02 pressure to ll ATA. papersby Fant, Lindquist, Sonessonand Hollien 971! and Morrow971! adequatelydiscuss speechdistortion at high pressure, which is the most obvious auditory alteration. To test for transient hearing losses from ex- posureto high ambientnoise andhyperbaric He-02 audiometricreadings were planned for the present dive.

Reaction Time

Reaction time of divers operating in hyperbaric environments may be fundamental to survival, and ultimately to continued developmentof satura- tion diving. As a result, reaction time has often been included in diving research; unfortunately there has been little standardization of tasks across investigations. Both simple speedonly! and choice time and accu- racy! reaction-time measureshave been demonstratedto be affected by inert- gas narcosis Bennett, 1965; Bennett, Dossett g Ray, 1964; Dicksonet al., 1971; Frankenhaeuseret al., 1963; Kiessling 5 Maag, 1962; Shilling g Willgrube, l937! . Simple reaction t'ime is clearly a vigilance function in- volving attention and perception, directly influenced by the Reticular Activating System Lindsley, 1958!. Choice reaction time has an additional componentof memory,and -- dependingon the level of practice andtask complexity -- an element of decision-making.

PsychomotorTests

1. Motor Coordination

Thediving literature distinguishestwo principal varieties of psycho- motor involvement occurring at depth: involuntary muscle tremor associated with the HPNS,and loss of voluntary eye-handmotor coordination. Measure- mentsof both types were consideredfor this study. Thepresent study wasenvisioned as a preliminary to an operational wet dive to 16 ATAscheduled for late 1972, and was concernedwith the effects of He-O~on motorability within both wet and dry hyperbaric environments.

As a result, psychomotortesting was confined to measures appropriate for both chamber and ocean application. The confines of the habitat precluded the introduction of an assembly task e.g., Bowenet al., 1966; NJeltman,

Christianson 5 Egstrom, 1970!; however, two tasks were incorporated that appeared suitable for laboratory and ocean testing. The Minnesota Rate of

Manipulation Test MRN'! was selected for its standardized procedures Betts, 1946!, its factor weightingson grossmotor manual dexterity Fleishmang Bllison, 1962!, and its prior use underwater Ono5 O'Reilly, 1971; O'Reilly,

1969! ~

A secondpsychomotor task, patterned after the screwplatetest of Baddeley966!, was includedto measurefine-motor performance. While not standardizedto sucha degreeas the Purduepegboard used by Kiessling4 Haag,1962!, the screwplatetest has similar fine-motor characteristics and hasbeen effective in bothhelium and open-ocean environments Baddeley et al., 1968; Baddeley4 Flemming, 1967!.

2. Nuscle Tremor

Numerousreports of heliumtremor have occurredin the literature Albano,1970; Bennett, 1966; Brauer, 1968; Buhlman et al., 1970;among others!.The occurrence of helium tremors at moderatepressures appears to beextinguished withslow decompression rates Bennett, 1967; Brauer, 1970! ~ and was not noted on a sensitive muscle-force transducer in the habitat Aegir the same chamber used in thepresent study! during a recent17 ATA oceandive Bachrachet al., 1971!. To verifythese findings, several ele- mentarytremor measures were contemplated for the presentdive.

10 Hemory Tests

Short- and long-term memory ability have been demonstrated to decrease with nitrogen narcosis, with short-term memorymost impaired Biersner,

1971, 1972; Steinberg 5 Sumxaerfield, 1957!. Apparently consolidation into permanentmemory from short-term memory is impaired, although previously learned material remains largely intact and subject to retrieval under moderate nitrogen narcosis. The degree to which short-term capacity is affected relative to impairment of associative memory is not clear. Addi- tionally, memory loss under He-0> appears minimal; Biexsner Q Cameron 970! report no memory loss at pressure to 31 ATA.

A dichotic listening tape was introduced as a sensitive measure of short-term ox immediate memory Broadbent, 1954; Neufeldt, 1966! . A stan- dard associative memory test used by Dickson et al. 971! was included as a measure of memory intermediate to short- and long-term. The task itself is characteristic of long-term memory and requires organizational strategy, but the time interval appears close to qualifying as short-term.!

Cogni ti ve Factors

A lack of standardized measures and vague conceptualizations of cogni- tive functioning have handicapped clarification of the degree to which narcosis affects the higher order cognitive processes. Attempts at detex- mining an objective physiological correlate of cortiral functioning have yet to producea reliable measureto replace the traditional paper-and-pencil psychological tests subject to learning and motivational variables.

Critical flicker-fusion frequency measures have proven to be unaccept- able Bennett g Cross, 1960!, and evoked-potential investigations currently are controversial Ackl.es 5 Fowler, 1971; Bennett, Ackles 4 Cripps, 1969;

Bevan, 1971!. EEGamplitude and frequency alterations have demonstrated.

11 potentia I 1 va ue as indicatorsof narcosis,but are not yet widely accept Albanoet al., l962, Bennett4 Glass,1961; Juilien, Roger5 Chatrian, 19S3. Roger,Cabarrou 5 Gastaut, 1955; Van Tassel, Knight 5 Lambertsen,1971! . 'Ihemost consistent indicators of cognitivedecrement have been the

psysychological 0 tests. Unfortunately,there has been no standardized usage jn theliterature; numerous forms of arithmetictests have been developed, as wellas an undistinguished assortment of psychometric tests purporting to measure"mental ability". Perhaps themost empirically rigorous attempt to unifythe various concepts andclarify the field of mental-ability testing hasbeen the development of a set of standardizedtests defining numerous cognitivefactors The Kit af ReferenceTests for Cognize,veFactors, French, Ekstrom4 Price, 1963! . Use of thefactorially distinct tests has been adoptedbynumerous investigators; several of these tests have exhibited somesensitivity tonarcosis-induced change Dickson et al., 1971!.Selected scalesfrom this series were included in the present study. It washoped that judicious selection of tests designed tomeasure performanceatseveral stages ofthe information-processing modelwould allowa systematicanalysis ofdiver behavior under helium narcosis. It was hypothesizedthatimpairment dueto narcosis wouldbe differentially observed onthe tests, with performance losshighly related todegree ofneurological complexityof the measuringtask. %THOOS

The primary emphasis of the saturation dive was centered on the measurenentof thermal regulation under hyperbaricHe-02 saturation. To accomplish this, a team of 3 investigators was trained in handling instru- mentation, measuring skin temperature, and collecting breathing gas,

Bicycle ergometer runs, cold pressor tests, measured caloric intake, and similar regimens comprised the physiological experiments, which are reported else~here Moore, Morlock, Lally 5 Hong, 1972!.

Scheduling of the physiological and psychological tests was closely coordinated, to allow an unprecedented opportunity for behavioral assessment under hyperbaric conditions . A pre-dive control period was scheduled, but exigencies of the situation failed to allow adequate preparation time for several planned psychological measurements, so that some cancellation and substitution of tasks became necessary.

The Habitat, Aegir

A saturation dive to 16 ATA with six subjects performing extended measurement tasks required a sizeable hyperbaric chamber; the submersible habitat, Aegir, owned by Makai Range Inc., was secured for the project. The

Aegir has a working pressure limit of approximately 19 ATA, a duration cap- ability of 14 days, and living and working space for six divers. The habit.at is 72 feet long and consists of three separately equipped, integrated pres- sure chambers Figure 1! . Living quarters occupied one chamber, while a second functioned as a laboratory and control center. The habitat was mooredat the Makai Rangepier at MakapuuPoint, Oahu,Hawaii!, approxi- mately 30 yards from the deck control room, and remainedsurfaced throughout the investigation. Communicationswere provided by a closed-circuit tele- vision, an electrowriter pen arrangement, and a helium-speech unscrambler

13 ttt

Cl tg

0 L 0 L tll L speakerunit, all locatedin the laboratorycylinder. Additionally, a standardintercom unzt connectedall chambersto the control roomtopside. primary verbal communicationswere placed through the unscrambler,an effec- tive devicefor mitigatingthe loss of intelligibility in heliumspeech. Complexmessages and critical data were transmitted throughthe pen writer, or werelocked in andout of the habitat with thrice-daily meals. The pre- senceof excellent communicationdevices, several view ports providing visual accessto the pier, periodic use of the medical lock for personal

requests, and occasional verbal interactions with families undoubtedly pro- vided considerable reassurance to the divers and served to attenuate anxiety

and stress reactions which might be more exaggerated during an open-ocean dive.

SUbjects

Space limitations dictated the maximum crew for Aegir. Six men were

selected from numerous volunteers: three from Makai Range and three from the Department of Physiology, University of Hawaii. The habitat commander,

a. veteran of numerous saturation dives, chose two Makai divers experienced

in habitat operations and deep diving, but with no saturation exposure.

The Makai divers thus tended to view the experience as a training operation as well as a scientific experiment. Each University subject was an experi- enced SCUBAdiver, although n.onehad mixed-gas or saturation experience,

Data collection and instrument maintenance were assigned to the University crew; life support andchamber operations were the responsibility of the Makai divers. All menshared the watch and participated in the physiological andpsychological tests. Theaverage age of the diverswas 31.2, with a rangefrom 22 to 42. TheMakai subjects were more experienced SCUBA divers, with an averageof 12.3years of diving as comparedwith 3.7 yearsfor the

15 University subjects. Five of the menwere married; four had children.

Interestingly, five of the six subjects had older brothers, one was firstborn, nonewas an only child. Radloff and Helmreich 968! found a significant correlationbetween firstborns and increased fear and lower performancein SEALABII, agreeingwith several other fear studies Darley

6 Aronson, 1966; Helmreich 6 Collins, 1967; Zimbardo 6 Formica, 1963!.

Apparently laterborns those with older siblings! exhibit less fear under stressful conditions. That most subjects were laterborns might be consid- ered unusual, since firstborns are more likely to volunteer for hazardous duty Perry, 1966!, volunteer for psychology experiments Capra 6 Dittes,

1962!, go to college Altus, 1966!, and achieve more eminence Schachter,

1963!. Radloff and Helmreich provide a summaryof birth-order relationships and an intriguing theory to explain them.

Dive History

Figure 2 depicts the dive profile of the Aegir Habitat for equivalent depthand pressure. As noted, the dive occupied10 days, starting on the afternoonof Day 1 with compressionto 8.6 ATA50 feet!. After 17 hours at this pressure,including two testing sessionsand an overnightstop, t.he habitatwas compressed on Day 2 to 16 ATA00 feet!. This pressure was maintainedfor 43 hours,until the afternoonof Day4, whendecompression wasinitiated. Decompressionencompassed Days5 through10, with stopsfor rest and evening sleep, Controltesting occurredon two daysprior to the dive, andapproximately twoweeks following its termination;all coat>o> conditionsare identified as Day 0 pre-test!, or Day0' post-test!~ Twodivers reported mild compression pains which dissipated rapidly with time; neither of thethesemen exhibited noticeable performance impairment directly attributable to thithis mi!dpain . No majordiscomfort was reported

16 + 4 C!

TlME HR! I 2 3 4 5 6 7 8 9 l0 DAY

Figure 2. Aegir internal pressure by day, measuredin atmospheresabsolute ATA!.

by the divers while at depth, althoughone demonstratedmild URI symptoms, Mostdivers had difficulty adjusting to the narrowtemperature-comfort zone commonwith He-02. Testing and watch routines were readily established, and life-support operations passed without major incident. The long decompressionphase was relatively passive, since most of the psychological andphysiological tests were administeredat maximumdepth during the first four days!, A serious caseof decompressionsickness bends!was experienced by the habitat commander,who had a history of such complications.The bends resulted in the remainingcrew adopting makeshift sleepingarrangements in the laboratory,while the medicalofficer entered the living chamberand administered 0~ to the diver. The"bent" diver re- coveredwell and egressedshortly before the remainingcrew. The latter stageof decompression50 ft andup!, with its imminentthreat of decom- pressionsickness and explosive fire hazard,proved to be the only really

stressful period of the dive.

17 SensoryTests

~pert eral Field ~itadent

Sealevel con tro] measureswere taken on Day0, as we1 1as measurement afterthe divers reached He-O~ saturation levels at l6.l ATAon Day 5. Each diverwas measured at 12 points along a standardstand -mount edSchwei g ger-t ype perimeter.The device provided an eye support and fixation point, and could berotated through 360' about the point of fixation. Thetarget was a white sphereapproximately 2 mmin diametersuspended froma blackwand. Subjects wererequired to indicateverbally when the targetappeared in the visual field. Testingwas accomplished at a small table situated in theliving chamber;illumination was constant across conditions. Z. ~Audtometrand Sound-Level ~Readin s Animpulse precision sound-level meter Bruel 5 Kjacr 2204, with octave filterset 16l3, microphone 4145!and audiometer headphones Beltone, Model l0-A!were included inthe habitat to measure ambient noise levels and pos- siblehearing shifts under hyperbaric He-0~. A suspectedmalfunction in the audiometerphones kept this measure from being repeated after the first test- ingsession at16.1 ATA Day 3!. Sound-levelreadings weretaken at periodic intervals throughoutthe dive.

A depth-perceptionapparatus wasincluded, constructed of two vertical rodsattached toa movableguide and enclosed in a uniformlyillumi««d woodencase. Depth estimations weretaken from 5, lOAand 15 Eeet in frowst ofthe case, using binocular vision. Two trials at each setting were pre- sented,with distance randomized acrosstrials. Therelative alignment of a stationarytarget with the movable matching rodwas measured in cent"~~~s.

l8 Although included in the dive protocol, essential measurements scheduled prior to dive termination were not securedbefore powerreduction during passage through the flammable zone. Depth measurementscollected on Day 2

8.6 ATA! and Day 4 6. 1 ATA! showed no change and will not be further ana-

lyzed in this report.

Reaction-Time Tests

A simple reaction-time test was designed for the study, provide

speed responses to onset of a light or a buzzer. This apparatus failed

under pressure, and the results were excluded from analysis.

A measure of choice reaction time was also included in the dive, pro-

viding sequential two-choice discriminations of visual and auditory stimuli

and requiring appropriate left-right movement of one hand to terminate the

signal. A prototype apparatus designed for the University of Colorado was employed, enabling measurementof reaction time from stimulus onset to ter-

mination, and response errors. Subjects received a series of 25 Visual sig-

nals: randomly presented blue or yellow lights. Following the visual trials, 25 Auditory pulses were presented through stereo earphones: the audio dis- crimination required identification as to relative "high" or "low" frequency

level. Both discrimination tasks required an appropriate right or 1 eft

movement of a hand-held switch to terminate the signal and stop the timer. A third testing series followed the auditory trials; this constituted a randomizedpresentation of visual-only, auditory-only or complementary visual and auditory signals, Eighteen of the 5G trials in this Combined series contained bimodal signals, none of which required conflicting re- sponses;}6 trials were visual-on}.y, 16 wereauditory-only, In all there were IGOreaction-time trials, repeat.ed in an identical sequenceon Daya 0

19 ATA!.Day 3 6.1 ATA!,and Day 7 ATA!. OnDay 1 8.6 ATA!and Day 2 6.1 ATA!,only the visual series of 25 trials waspresented. Intertrial interval wasrandomized and reaction time wasmeasured in hundredthsof a

sacmd.

Reactiontime speed!closely approximatesthe vigilance function asso- ciated with arousal level, and representsthe secondstage of behavioral complexity. producingappropriate responses in a forced-choice situation requires attention to stimuli, recognition, and association and reflects a higherlevel of informationprocessing than is necessaryfor responsespeed. Accordingly,error responsesvill be discussedas a higher level information- processingcapability, associated with memory and decision-making.

PsychomotorTests Severalmeasures of motor coordination were included in the testing routine,the most common of which was the Minnesota Rate of' Manipulation Test ~%Ãl',a recognizedtest of grossmotor functioning. The MRÃI' consi sts of 64disks, 38 mm in diameter,which fit into holesin a formboardapproxi- mately25 cm by 100cm. Variousmanipulation tasks are possible; selected forthis study were: one-hand ~placin, one-hand ~Tutnin, and one-hand ~hislacin . TheMRMT was positioned ona counterin the laboratory, where eachsubject was timed as he completed two trials per testingsession on eachof thethree subtasks. The tasks were presented in a set order,with responsesrestricted to thepreferred hand. Testswere administered on Day 3 6.1 ATA!and Day 7 ATA!,as well asa pre-divecontrol test onDay 0. h secondpsychomotor testwas included, patterned after the ~Screw late Testdesigned byBaddeley 966!. A 22-cmby 33-cm plate supported by17-cm legshad 32 7-cm holes positioned in two 4 x4 arrays.Carriage bolts ini- tially werepassed through the 16 holes in onearray and backed by hexagonal

20 nuts. The subject was timed as he transferred the bolts and nuts from the first array to the second. Unlike the MAN', which requires mostly gross eye-hand coordination, the screwplate test necessitates fine-motor manipu- lation of components to shift the bolts and nuts. Obtained scores were total time to shift 16 bolts and nuts, number of components dropped, and number of loose nuts defined as loose I/4 turn! . If a nut was dropped on the table, it was to be recovered; but a nut dropped on the dech could be replaced from a container. The screwplate test was performed on a Labora- tory counter on Days 0, 2, 4, 7, 8, and 9. An additional task requiring eye-hand coordination was provided pri- marily for subject enjoyment. The Hand Maze "Lahyrintspel" by Brio,

Sweden! required two-dimensional manipulation accomplished by knobs control- ling a 23-cm by 27-cmplane on which a raised mazeand numberedholes were strategically located. The task required maneuvering an ll-mm steel bearing through the maze; the score obtained was the numberof holes successfully negotiated. The mazewas administered in the evenings on Days I throiigh 9, with each diver restricted to seven trials a trial ended when the bearing entered a hole!. The best five out of seven scores were analyzed for a daily average score. The task served several funct ions: primarily it provided some measure of entertainment and competition amongthe divers in this regard, it was well received!; additionally, it served as a rough measure of skill acquisition or motor learning! under He-Oz. A simplemaze-tracing procedure Test Ss-l, fromthe Kit of Reference TeStsfor Cognitive Faotora! was included in the testing protocol as a counterpartto the HandMaze psychoaotor task. TheMaze T~racin test has been identified as a measureof spatial scanning, reflecting sp

21 movements. It wasincluded primari ly for subj ect interest, to providean interesting variation fromthe other paper-and-penciltasks. Ss-I was

adnninistered on Days 0, I and 3.

Nenery Tests ShOrt-ternnenetY Wae teSted bY PerfntmenCe Ona nithntic ~bistenin ~Tae. A 12-minutebinaural cassetterecording was included in the habitat alongwith a cassetterecorder and earphones and several music tapes f'or recreationalpurposes!. After a brief tapedintroduction, the subject listenedto threeseries of numbers.The first serieswas comprised of 10 presentationsof fournumbers, two simultaneously presented to eachear. Thesewere followed by 10 sets of 3 digits to eachear, andconcluded with I0 setsof 4 digitsto eachear. Thestimuli weredrawn from Inglis 0 Caird 963!,and are presented in Table I, by inputchannel. Recording was accomplishedsuchthat two numbers, one from each series, were heard simul- taneouslyby the subject. A correctscare was obtained for eachnumber successfullyidentified after the dichotic presentation. Thememory tape wascompleted twice: at sealevel Day0!, and14 ATA Day 4! . AsAssociative M~emo r test Ma-l,t' he Picture-Number Test! was selected fromthe Kit af' A'ef'crease Testefor G'ognitiueFactors. The test required thesubject tolearn number associations to a series of picturesdepicting commonobjects. Thetest wastimed, and the scoreobtained reflected the numberof correct associations recalled during the testing phase. testwas administered onDay 3 6.1ATA! and during post-testing Day 0'! ~ Rehearsaltime for thelearning segment of the test, was 4 minutes,which indicateslittle necessityforcomplex storage but provides some indication of rote learning ability.

22 TABLE 1. NUMBER SERIES USED IN DICHOTIC LISTENING TAPE

Listening Task Left Channel Right Channel

2 digits per ear 39 72 85 17 38 46 65 29 73 58 26 31 41 63 52 14 61 92 94 85

3 digits per ear 592 174 793 461 479 836 584 719 437 692 816 243 312 957 259 618 941 386 615 827

4 digits per ear sess 294 I. 9754 8362 6542 7918 9356 4271 1627 3859 5427 1362 2851 6493 3174 2968 5742 3698 4138 2965 aSynchronized tape supplied by F. Ahern, University of Hawaii.

23 Cognitive Factors

N~r~ tests have been developed pu&o~lng to measure var1aus face~s of cognitive ability. For standardization, the Xz',tof Reference Testa foz

Cogentt'.ua Pactore re wasw selected as the basic sourcefor psychologica1paper-

and-pencil tests. An attempt was madeto select tests with prior use in

hhyper b aric ' resresear arch or that reflectedvarious cognitive factors investigated

by others.

The cognitive factors tested and their schedules were:

Perceptual Speed P-2 Number Comparison! Days 0,1,3 P-3 Identical Pictures! Days 0,2 Spatial Orientation S-1 Card Rotation! Days 0,2 S-3 Spatial Orientation! Days 0,4 Flexibility of Closure Cf-2 Hidden Patterns! Days 0,2 Inductive Reasoning I-3 Figure Classi fication! Days 0,3

TestsP-2, S-l, andCf-2 had been used previously in hyperbaricresearch: I -3was chosen in place of theLetter Sets Test I-1! previouslyused. P-3 andS-3 were included for their interestingformats, in aneffort to maintain thesubjects' active interest over extended repetitive testings, and to test forresponse stability by providing additional measures antwo of thefactors- Ratherthan incorporate oneof themany versions of mathematicsability testspreviously used, an attempt was made to providea moreappropriate measureofcognitive functioning byhaving the subjects calculate repetitive divedecompression stopsbased onNavy Dive Manual compressed-air tables~ Dive-tablecalculations were considered more functional indicators of mathe- maticalfacility than the traditional addition or multiplication test~- Severaldecompression problemswere developed bythe author and rank« >n fivedegrees ofmanipulative complexity. Threetestings were scheduled, withfive problems persession, one randomly selected from each level of

24 comp].exity. Each problem was presented on the standard Dive Manual format Appendix!. Time to completethe five problems,number of errors, andnumber of oper'ations correct were scored for each testing on Day0 ATA!, Day 2

6.l. ATA!, and Day 6 8.5 ATA!.

Personality Correl ates

FormB of the SixteenPersonality Factor Questionnaire ~16PF was administered to al 1 subj ects during the pre-dive control peri od, providing a measureof personality. The 187-item test purports to identify 16 inde- pendent dimensions of personality Cattell, 1963!. There is some evidence that stress-response interpretations can be significantly improved with per- sonality, adjustment, and social variables are considered e.g., Haythorn

Altman, 1967; Nelson 5 Gunderson, 1962!.

Anxiety has been shown to affect performance, physiological responses, and self perceptions in a stressful situation Appley 4 Trumbull, 1967;

Persky, 1962; Weinstein, Averill, Opton 5 Lazarus, 1968}, and i.s essential

'to the understanding of behavioral responding in a stressful environment.

Twomeasures of anxiety were selected for this study: a measure of consis-

anxiety level The Taylor Manifest Anxiety Scale, T-MA!, and an imme- diate, time-dependent daily anxiety level the Multiple Affect Adjective CheckList, ~MAACL Weiner, Dorman,yersky, Stach, Vorton 6 Levitt, 19633. The Manifest Anxiety Scale Taylor, 1953! was administered during the p e-«sting period, and provided a measureof trait anxiety for the subjects. TheMAACL is a standardized scale providing measuresof anxiety, depression, hostility Zuckerman5 Lubin, 1965!. The MAACLwas administered in a general"form both pre- andpost-dive, and in a "daily" form eachevening, TheMAACL has previously beenincorporated into hyperbaric research,

25 measuringsubject stress reactions to chamber diving Weltman, Smith g

Egstrom, 1971!, and has been found sensitive to situationally induced stress

A nonstandardized daily attitude questionnaire Appendix! also was

administered each evening. The test contained 12 unidimensional scales soliciting descriptionsof affect, interest, and sociability. Nine bipolar semanticdifferential scales per Osgood,Suci 4 Tannenbaum,1957! provided,

a daily measure of attitudes about the dive. Both the MAACLand the self- rating questionnairewere administeredeach eveningand were completed at

the divers' leisure. A post-test debriefing questionnairewas administered approximately two weeksafter the dive. The questionnaire see Appendix!focused on the sub- ject's perceptionof his role, critical incidentsof the dive, andsubjective judgementsof success,difficulty, etc. A short sociometricseries was in- cluded to identify diver interactions. ln general,the personalitytests were designed to providesome under- standingof the individual perceptions of the divers, as well asa general measux'eof group daily affect. Extremefluctuations in pexsonality were not antici p ated as the divee wwasnot considexedphysically exhausting or exces- sively stxessful.

Psycho]ogica1Testing Schedu!e

The testing schedulefor thoseose measures actually administered is sum- marized in Table 2, with the testses s identified i as to their general category A disproportionate numberof testsests werew administered during the first days, reflecting the author's p artir icular interest in behavioral effective- nessimmediately after experiencinging increased pressure.

26 dJ 4 cCI b0 4 -'8 cd III f- dl U c4 I cd cld I IJD I cg I cd 0 IJI ID 0 4

I cJ! IJI dJ dJ I I 0dI V I cd cd cd LJJ I N dJ N dJ cd 0 V 0 I I ! I I-I

V V ~ A I dJ 0 0 0 r5. cd O ~ I V 0 cd 0 4 0 0 dJ dJ dl dI 0 dJ dl IJI ICI cd cd g~ cd E 0 m ~cd ~cd C4 0 9 p 4 0 3 3 dJ ILI dJ E N 4 4 cd cd V ccl cd V V cd V K i X ch X X M K LJJ X m

4 0

'0 '0 0 0" dI0 0 " ILI dJ g cd cd -H 0 Xl In E E 0 ~w 0 E0 ! FQ ! U

dJ dJ ID V al V 4 dJ ILJ dl O a 0 0, E 0 0 Jl LJ

v! 4 u;

cd Lfl In 00

27 Severaladditional measures were considered for the dive, supplementing rep]acing those used. Inadequatepreparation time forced cancellation of

an evoked-potential study; it was replaced by additional cognitive tests. A measureof time estimationwas considered, but the associated electronics failed underhigh chamberhumidity. No differences in time production esti- mateswere found for the single series of measurementscompleted. Tremortasks werecontemplated for the investigation, but the sensiti- vityyof measurementwas adversely affected by environmentalfactors, and the tests werediscontinued. The mooring arrangement of the Aegir at the MakaiRange pier permittedslight but erratic lateral movements,and wave actionin the harborproduced an additional periodicmovement of the habitat. Movementinduced by divers' passage across the laboratorydeck plates also interferredwith the precisionof tremormeasurements . RESULTS

Sensory Testing l, ~Periheral Field M~ai~in

Peripheral field mappingdisclosed no appreciabledifference between control and 16-ATA testings. No diver exhibited a clear field alteration, althoughconsiderable retest variability wasfound {Table 3!. Of a total 144points retested, {12 per eye,24 per diver!, 42 exhibitedat least a 5' loss from sea-level control measurements,39 showeda 5' or better gain over control measurements,and 62 points did not appreciablydiffer. Only one largegroup-average difference was recorded; for the left medial210' meri- dian an average improvementof 12 17' of visual field over control measure- mentswas found at increasedpressure. Sinceno supportingpattern of visua.' shifts was evident at the remainingpoints, this averagegain mayreflect an artifact of the lighting or experimentertechnique. In general,there was no evidencethat peripheralvisual fields undergodiminutio~ under pressure, or that exi.stingstress effects of the saturationdive directly alter peri- pheral visual ability. 2. ~Audionetrand Sound-Level ~Readin s Ambientnoise levels within the habitat wereappreciably higher than normalliving andworking situations {Table 4! . All tabledata were recorde withthe sound-levelmeter {SLM! hand-held and facing the rear bulkhead.Th consistentlyhigh C-scale readings relative to A andB scalesindicate pre- dominantnoise at frequenciesbelow 700 Hz, which was corroborated byoctave bandanalyzer readings. {These readings differed from earlier measurements of AegirnOiSe level at 130ft [5ATA], Which eXhibited a uniforlA nOise distribution acrossall scales[A = 70db, B =75 db, C =72 db] 1 .! Personalcommunications, D. Thorne to J. Pegg,Makai Range.

29 TASLE3. GROUP-AVERAGEDIFFERENCES IN DEGREE OFVI SUAL FIEI 0 FORPERIPHERAL MAPPING AT SEALEVEL AND AT 16 ATA

Visual Field Gain or Loss, in degrees Left Eye Perimeter Plane Right Eye lateral! 0' -O. SO +5.50 30' -1. 50 +1.00 60' -3. 67 -5.17 caudal! 90' -0. 67 -4. 67 120' +l. 83 -2. 50 150' +0.50 -4. 17 medial! 180' +5.50 +0.33 210 -l. 83 +12. 17 240' -2. 33 +3. 37 crani al ! 270' -2.50 -3. 00 300' +1.67 -2. 33 330' -3,00 -0. 83

TABLE4. SOUND-LEVELREADINGS IN AEGIR LIVING AREA, SLM HAND-HELD The sound-levelmeter was held so the microphonefaced the rear bulkhead.!

Readings on Three Testing Daysa Meter Day 3 Day 4 Day 6 Scale 6 ATA! 4 ATA! 8.5 ATA!

52 db 55 db 53 db 65 61 68 82 68 84

31. 5 80+ 78 63 70+ 69 125 60+ 65 64 250 60+ 54 52 500 50 52 49 1 K 40 53 49 2 K 38 46 44 4 K 30 46 39 8 K 46 42 16 K 35 31.5 K 22 Testingtimes differed slightly across the 3 readings: Day3 -- 8:00p.ra., Day 4 -- 9:30p.m., Day 6 -- approx.9-00 P m' Timewas probably not as important as types of competing«s"s ~ outside weatherconditions, and other activities that could r»se the ambient noise level.

30 A single measuring series with the SLMmicrophone stand-mounted in the center of the living quarters and directed towardsthe ceiling yielded appre- ciably higher readings than those noted above Table 5!. Scale C was again relatively higher than A or B, and all filter bands registered between 70 and 90 db. To determine the source of chamber noise, various items of noise- generatingmachinery were systematically eliminated. Theprincipal noise- emitting machinery were the CO~ scrubbers and the dehumidifiers, with the scrubbers off, some drop in ambient noise was recorded. However, with all machinery off there was still an appreciable noise level in the habitat.

The higher values of Table S might be the result of testing time afternoons were noiser than evenings! and activities occurring simultaneously on the testing day, as well as SLMmounting characteristics,

TABLE$- SOUND-LEVELREADINGS IN AEGIRLIVING AREA,SLM MOUNTED The microphonewes stand-moontedfacing the cei I ing. !

a Readings under Three Conditions

Meter All equipmenton. Dehumidifiersoff. Dehumidifiersoff. Scale Scrubbers on. Scrubbers off.

64 db 62 db 60 db

7S+

105+ 98+ 95+

a Readings taken at 3:00 p.m. on Day 3. All octave band filter readings were 70 to 90 db. Audiometric testing was initiated on Day 3 at 16.1 ATA, in conjunction with the sound-level readings of Table 5. As reduction in noise level was not appreciable with life-support equipment off, and since the habitat com- manderwas hesitant about shutting the equipment down for the length of time necessaryfor testing, measurementswere taken with life-support equipment operating -- providing a very noisy environment. Table 6 portrays the re- sults of' the 16-ATA audiometry tests. The exceptional consistency of results, particularly the considerable loss at frequencies of 1000 Hz and lower, gen- erated speculations that the audiometer headset was adversely affected by pressure or humidity. However, considerable low-frequency ~asking from the high-noise environment must also be considered.

Reaction Time

Figure 3 depicts performance speeds on the choice reaction-time tasks.

A series of Retest by Subject Analyses of Variance determined that no sig- nificant difference betweenspeed of reaction existed for the various retests on the Auditoru F 2.38, df 2,10,.p n.s.! or Combined F = 1.88, df =

2,10, p n.s.! stimulus conditions. However, a significant difference in reaction times to Visual stimuli was noted F = 2.87, df = 4,20, p < .05!-

A range test of results on the five testings of visual choice reaction time indicated that significant speeddifferences p < .05! occurredfrom Day 2 to Day 3, with Day 2 first 16 ATAtesting! reactions faster than those of Day 3 second 16 ATAtesting!.

~In testing for nonchanceoccurrence, three standardstatistical tests were used throughout:

Wo-tailed t-test. Two- and three-way treatment by subjects T X 5!, factorial design analysis of variance Meyers, 1966! . Newman-Keulsprocedure of the studentized range test Winer, 1962! .

32 TABLE 6. RESULTS OF AUDfPMETRYTESTING

Frequencies: 125 250 500 750 1000 1500 2000 3000 4000 6000 8000

Frequencies: 125 25P 500 ESP 10PP 1500 2000 3000 4000 6000 8000

Testing conducted at 3 p.m. an Day 3.

33 NEG

AL

0 1 2 3 + 5 e 7 8 9 GAY 1 88 Nkl N.l II ll.5 8.5 8 55 1.5 PRESSURE < ~ Figure 3. Reaction-timeperformance speeds on Visual, Auditory, and Combined tasks n ~ 6!.

OTAL 3

23

20 UAL O

1O GITORY

0 1 2 3 g 5 8 7 8 9 0 A~ 1 8,6 i6,1 ~.i lg 115 85 g 3.5 1.3 PRESSURE t ATA !

Figure 4. Reaction-time choice errors on Vi sual, Audi tory, and Combined tasks n 6! . While reaction time remained relatively stable across testings, errors in responsejudgment increased significantly fromcontrol to high-pressure conditions Figuze 4!. Total errors from all three series! were foundto increase very significantly across testings F 8,86, df = 2,10, p < .Ol!, as did errors on stimuli presentedin the Combinedcondition F = 7.6S, df = 2,10, p < ,Ol!. Rangetesting determinedthat Total errozs on Oay7 did not differ from those on Day 3, but Combinederrors on Day 7 were signif- icantly greater than on Day 3 p < .05! . In analyzing the effects of stimulus modalityon responsejudgment, bothVisual and~ditozd errors werefound to increaseover control values, althoughneither trend quite reachedsignificance: Visualerrors F 2.92, df 2,10, . 10> p> .05!, A~uditorerrors F ~ 5.26,df 2,10, . 10» p .05!. A 3-wayAnalysis of Variance,contrasting errors on the threestimulus modes acrossthree testings for six subjects,disclosed a significantdifference betweenstimulus conditions F = 10.7S, df = 2,10, p < .01!, with Combined seriesgreater than Visual or Auditoru Cans,ideringthat therewere 50 trials for Combinedand only 25 for eachof the otherseries, the larger absolutemagnitude of errors is not unexpected.! Thelower error rate for A~uditorresponses noted in Figurea isnegated whenauditory-only stimulus trials occurringwithin the Combined series are considered.As noted in Table7, auditory-onlypresentations initiated 49~ of the Combinedmode errors, althoughcomprising only 32~oof the presenta- tions. Whenresponses onall auditory-onlytrials were considered, there wasa significantdifference in errors committed across the three testings F = 11.28,df = 2,10,p < .01!; withDay 3 andDay 7 errorssignificantly greaterthan Day 0 errors p < .01!,but not different from each other. Yo similarsignificance wasnoted on trials requiring responses to visual-only sti~li F 3.3g, df 2,10, .1O > P > ~OS!, Primarily due to high subject vari abi lity,

TABLE7. REACTINI-TIRE COHBINED SERIES ERRORS: ANALYSIS BY SENSORY CHANI!IEL

Mo. of Errors on 3 Days 't of Sensory Tot al Nodal ity Day 0 Day 3 Day 7 Errors

Visual 3 7 234 n 16!

Auditory 13 4A n 16!

Visual auditory n = 18]

Total errors 14 26 100%

Testing visual-only against auditory-only errors acrosstests and sub- jeCtS demOnStratednO Significant stimuluS-mOdediffere~Ce F = 0.010 l,S, p ~ n.s.!. &us, there wasno significant iifference betweenthe two sti uluSmodeS ViSual and auditOry! On infOrmation-proCeSSingoperatiOnS- vigilance speed!and retrieval accuracy errors! were not significantly different for the twoinformation channels employed.

PsychomotorTests

Fourof the six diverscompleted all three testings of the MRMI' Figure S! Timeto completion speed! was not significantly altered acrosstestings for all threesuhtests: ~placin F = 4.52,df = 2,6, .10 > p > .05}, T~Tnin »> p > .05!, and ~Dislacin F = 0.45, df = 2,6, p = o.s ! foap!ation risesfor 0~latinand ~Tutntn tended to increaseon Day

36 over control or Day 7 values, but failed to reach an acceptable level of statistical significance.

60 c 56 0 525 TURNING

~ 48 PLACING

Z ~ DISPLACING g 40

~ 56 Q 5 I O O 0 i 2 3 4 5 6 7 8 9 DAY 8.6 is.i iS.>V ii.s 8.5 6 a.5 i.S PRESSURE ATA! Figure5. COmpletiOntiIneS far 3 SubtaSkSOf the MinnesotaRate Of Mani pu 1 at i onTes t n 4! . Thefunctional S~crew late Test provided significant performance change acrosspresentations for thefour administrations completed byall sixsub- jects DaysDm 2, 7, 9! F = 5.30,df = 3,15,p <.025!. ijnlikeearlier resultswith compressed air, Screwplate testing time to completiondidnot increaseunder pressure; rather, performance improved over control conditions »gure6! . Rangetesting identified no significant difference in time per- formancebetween Days 0, 2, and7; performanceonDay 9 wassignificantly

improvedover earlier testings. Foursubjects completing all six testadministrations Days 0, 2, 4, 9! demonstrated es sentia ly1 thes arnebehavioral improvement overt ice as notedabove F = 4.70,df = 5,15,p <.0]!. Therange tests established thatperformance wassignificantly faster on Days 8 and 9than on Days 0. 2, and 4, and with Day 7 results intermediate.

3 s similarly, results of testing on Days 5, 6, 7, 8, and 9 did not significantly differ from each other. Performance on Days 1, 2, 3, and to some degree Day

4, was significantly different from that observed on the last five days

-9!. Learning, as measuredby improvedperformance, appeared to increase rapidly after Day 4.

I6

~ l4 HAND MAZE M I2 CL ~ O B

CO

Z

0 i Z Z 4 5 B 7 e 9 DAY B.Bi6,i IB.I I4 II.5 B.5 e a5 I.S PRESSURE{ 4TA! Figure7. Psychomotorperformance on MazeTracing n 6! andHand Maze n = 5!.

Thepaper-pencil Maze T~racin speed test Ss-1!also produced sidniti- cantly improvedperformance on retesting underpressure F = 17.79, 2,10,p <.001! . BothDay 1 andDay 3 resultswere significantly improved over control values. Nosignificant differencewas found between ween DaDay Day3 scores,although there was a tendencyfor group-averageperforman« to decreaseslightly at the greaterpressure Figure 7!.

39 Nemory

Fivesubjects completed. both series on the sensitivemeasure of short- te~ smmsty,the Pichotic ~Listenin T~ae. There were no significant differ- ecesapparent between control and hyperbaric performance levels oneither the4-digit series,6-digit series,or 8-digit series Table8!.

TABLE 8. GROUP-AVERAGEERRORS FOR FIVE DI VERS ON THE SMORT-TERMMEMORY DI CHOTIC LI STENING!TAPE

digits per ear! X SD X SD df = 4!

1.00 2.24 0.40 0. 55 0. 53 n. s. !

3.80 0.83 2. 80 1. 92 1. 05 n. s. !

15.60 3.78 15. 80 3. 70 0. 17 n. s. !

Associative Mern~toperformance on the Ma-l Pictuxe-Number Test! strated a significant decrement between sea-level control and testing at 1 ATA t = 2.60s df = S, p < .OS!. A 25%loss in rote learning ability can bc noticed from Figure 8. Thus, operating in a helium environmentat depthdid not significantly affect inaeediatememory capahiiity on the hichotic ~Listenrn T~ae,hut did depressfunctioning on the AssociativeM~emo task ~

Cognitive Factors

Resultsof the cognitive paper-and-penci],tests were somewhateQuivo Of thesix testsreflecting four cognitive factors, performance unde»yp baricconditions decreased for threeand showed some slight improvementf

40 tvo Figure 8!. Onetest, inductive ~reason a -3! vas mistimedat depth and was discarded from further consideration.

~ 130

a 12

0 K~ IOO0 O 9 CF-2 0

8

0

CL

SL 2 4 6 8 10 IR 14 16 PRESSURE AT@ !

Figure 8, Group-average performanceon cognitive and Associative Hemory tests. Results are I isted as a percent of sea- level control values. Cf-2 completed by 5 subjects; a 1 1 othe rs had n 6. !

Based on two-tailed t tests, performanceunder hyperbaric He-02 was found to be significantly reducedfrom sea-level controls on ~erce tuel ~seed df = 4, p < .05!, and~satial orientation S-1! t = 3.06, df = 5, p < .05! . Neither of the tests exhibiting improvedperformance at depthhad re- suits significantly better than chance:peerce tuel ~seed F-2! F = 3 42 df = 2,10, .10 > p > .OS!, and~satial orientation S-3! t = 0.42, df = 5, p = n s.!. Thediscrepency between these two cognitivemeasures and the other three maybe dueto test construction artifacts unrelated to the factors

41 The number-comparison test P-2! utilized an undesirable

scoring procedure; based an test structure, it is possible to receive scoring credits for itemsnot answered.Occasionally a series af these non-response correct items occurred,providing difficulty in delineating whenthe ending

point of the timed test actually occurred. Suchwas the case for 4 out oE 6 diverson bothDay 0 andDay l. Anaccurate comparison of timed performance was not possible based on improper test structure. Thespatial orientationtest S-3! wasconsidered extremely confusing anddifficult by subjectsat their first exposure Day 0!, althoughaddi- tional pre-test practice wasallotted for discussionof the task. lt is possiblethat a learningeffect wasevidenced during the secondtesting on S-3; cognitivetest with morecomprehensible tasks might not be expected<> exhibit suchan effect. Fortunately,the cognitive factors associatedwith thesequestionable tests were sampled by othertests in the battery",P-3 and S-1performance scores both demonstrated appreciable loss in cognitivefunc- tioning ability with increasedpressure. Thesubstitution of dive-tablemanipulations for standardizedarithmetic testsintroduced additional performance bias and interpretive di fficulties- Therewas same tendency forpractice effects to assistperformance onthe secandtesting l6.l ATA!,particularly for thosedivers who had never used tablesor had used other forms. One such diver had difficulty adjusting to thestandard Navy form; he exhibited performance times substantially lower thanthe other divers, failing to completeall problemsafter an extended testingperiod. As a result,a "timeper operation" score was substituted far "timeto finish".Analysis of this measure indicated a significant per- formanceimprovement acrosstests {Figure 9! {F= 4.32, df = 2,lO.p Multiplerange testing determined 'thattime on Day 2 wassignificantly faster thanon Day 0; time/operationonDay 6 wasnot significantly different from

42 values for either Day 0 or Day 2. Although group total errors increased substantially with increased speed{Day 0 7, Day 2 17, Day6 * 10! sub- ject variability reducedthe possibility of statistical significance F

0.94, df = 2,10, p = n.s.!.

IS

IS IME / OPERATGN l4

l2

IO / I / 0 l20 2 I4 S4 5 4 T 9S av 4.4 IS.I IS,I i 4 1 15 45 5 54 i.S Paf$8URE aTA ! Figure9. Timeper operation and errors conmitted ondive- table ari thrretic test {n ~ 6! .

personal july Tests

1. General~Grou Characteri sti cs Subjectscores differed significantly from published aduIt norms onlyone of the sixteen personality tactors ofthe 16PF Table 9! Aegi~ subjectsscored significantly higher on Factor 8 ameasure of intel 1igence! . Onan individual basis, very few of the divers registered responses outs

43 1, There was a tendency for several individuals to score low on Factor A, reflecting more aloofness in social situations, tending not to make good group members. There was a tendency for most to be bright and conscientious Factor B! . On.emotional stability Factor C!, two subj ects scored very low, reflecting lack of frustration tolerance, some immaturity, a tendency to worry, 4. Two subjects scored high in agressiveness or dominance Factor E!, reflecting a high degree of competition. S. All subjects but one were very normal on ego strength Factor G!; the exceptionregistered somedegree of casualness or undepend- ability. 6. Several subj ects scored high on Factor l4, reflecting some uncon- ventionality, coupled with absent-mindedness, minimal responsi- bility on practical matters, often with high internal anxiety. 7. TWoindividuals were found to register high on Factor Q3, char- acterized as poor sel f-sentiment formation, denoting lack of self- control and to some degree lack of consideratio~ for others. 8. Onesubject registered high on Factor Q4, reflecting sometension, anxiety, and excitability.

TABLE9. COHPARlSONOF GROUP-AVERAGERESPONSES ON THE 16PF FOR DfVERS AND ADULT MALE NDRMSAMPLE

Fact,or X SD X SD df = 791!

A 6. DO 2. 97 8.89 4.31 1.64 8. 50 1. 97 6.78 2-00 2. 104' 16. OO 4. 81. 16.60 4.20 0 34 F. 11, 83 4. 62 10.82 3 ' 69 0.66 F 13.33 3. 83 12. 92 4.39 0.22 12.67 1.50 14.26 3 -29 1.. 18 12.00 3.10 14. 57 3. 29 1. 14 GI L 8,67 2.06 9.68 3. 12 0. 79 6,83 2.56 7. 94 3.07 0.88 12.00 4.DG 10. 05 3.85 1.24 9. 17 1.83 10.20 2.65 0. 95 0 9.50 2.81 10.70 4.25 0.69 Ql 9,33 1.86 9.86 2.91 0.44 Q2 9. 83 1.47 10,22 3.14 0 30 Q3 12. 50 3, 15 12.12 3.00 0,31 q4 11, 50 4.85 11 70 4.21 0.11 >t valuesignificant beyond .05 level; all othersare nonsignificant.

44 In general, there wasno indication of excessiveincompat ability among the divers; most remainedsociable and cooperativethroughout the dive. There wassome evidence of covertanxiety amongseveral. Individualsregistering lack of responsibility and undependabilityon the 16PFalso were those failing to complete assigned. tasks and psychological tests. Trait anxiety, as measuredby the T~alor Manifest A~nxiet Scale T-MA!, was unusually high for two subjects, moderate for one, and low for the other three. This anxiety dimension appeared to agree fairly well with 16PF inter- pretations, but not with scores on the MAACL-General,which appears to measure more situational stress. Divers exhibiting more immediate stress during pre-testing were those with more general awareness of the entire investigation. Those less directly involved with habitat arrangements or scientific preparation registered lower MAACL-Gscores, even when they appeared to have higher trait anxiety, as measuredby the T-MA. High imme- diate stress may be a more appropriate response in certain situations .

On the General form of the MAACIsome depression and hostility were noted for several divers; there was little change in registered depression over the dive, but hostility showedsome increase -- even though the post- test MAACL-Gwas administered two weeks after the dive ended. Table 10 summarizes the mean values and t tests for the MAACL-G. As can be noted, there wasno significant difference betweenpre- and post-test results.

2. Post-test ~Debriefin

On the debriefing questionnaire, five divers noted that their principal reason for volunteering wasto gain experience; several also listed challenge andgeneral interest in diving. TwoMakai divers consideredthe most impor- tant aspectof the dive to be the saturationtraining received;the remaining four stressed data collection as the primary goal of the dive. The scientific

45 crewand the habitat cmaaanderalso noted the value of their participation

as subjects. Dree divers expressed initial moderate interest in the scien-

tific aspect of the dive; of these, one noted his interest as increasing, twostayed only moderatelyinterested. Three divers noted high initial

interest in the scientific aspect: of these, one decreased interest, one

increased interest, and one remained the same.

TA8LEIO. COMPARISOROF PRE-DI VE ANDPOST-DIVE GROUP"AVERAGE SCORES n ~ 6! ON THE THREESCALES OF THE HAACL-G

Pre-Dive Post -Dive t Scale SD df = 5!

Anxiety 8. 50 2.51 7. 17 1. 72 I . 51 n. s. !

Depress ion 13. 50 5.32 14.00 3. 16 0.52 n.s.!

Iiost i li ty 8. OO 3.22 9.67 1. 75 1.89 n.s.!

The mostcritical, or dangerous,point in the dive was consideredby a11divers to be the decompressionstage. Threemen expressed particular concernwith decompressionsickness; two mentionedthe case of bends experi- encedby the habitat commander.Two additional divers mentioneddecompressing into the flammablezone as the most critical maneuver. It was apparent that all divers weresomewhat apprehensive as the decompressionphase approached. All divers indicated a willingness to participate in another similar dive. 'Dree subjectsnoted the dive waseasier than expected;two of these

46 also noted the scientific aspect was easier than anticipated. The most ex- perienced memberreported the level of difficulty of the dive was as he had anticipated, while the two divers principally responsible for equipment maintenance noted the scientific portion was more difficult than had been expected.

Most divers reported no change in their own or others' social behavior.

Two men perceived their status in the habitat crew as increasing during the dive. In fact, based on outside observations and responses to the socio- metric questionnaire, the only evident shift in status appeared to be oppo- site to this perception, at least for one of the divers.

The sociometric questions did not reveal any obvious clique formation, although both Makai and University divers picked first-choice friends fram amongtheir own professional group, undoubtedly indicating previously existing friendships. Second- and third-choice friends were scattered amongall subjects' There was general agreement among the divers regarding most com- petent performances; generally the individuals with the most responsibility and clearly defined jobs were seen as performing most competently.

Listing of "most sociable" and "most adversely affected" individuals produced results negatively related to patterns of friendship and responsi- bility. There was no consensus individual considered to have been most. negatively affected by the dive. Several divers looked beyond the obvious physical difficulties experienced by the group and appeared to rate diver impairment on psychological adaptivity; at least, their ratings agreed closely with a subjective evaluation produced by the author from T.V. observations, discussions with control room operators, and personal communications with the divers. In general, the divers were well suited for the experience in enthusiasm, ability, and responsibility. The uniqueness of saturation diving for all subj ects excepting the habitat commander! probably assisted in

47 developinga camaraderieamong the men. Topside control crew remarkedon several occasionsthat the habitat crew exhibited the highest morale ever noted «ith Aegir dives.

There wasno predominantcomplaint concerning the dive; among the items crmrsideradto be bothersomewere: diet, blood letting, psychological tests, open-microphone surveillance, sleeping arrangements, helium-speech difficul- ties, crowded space, bilge flooding, cold. It is interesting to note that the subject bothered by the psychological tests was also the one who consis- tently failed to completethem. If given the opportunity, he avoided test participation irrespective of task complexity.! The University divers were unanimousin their suggestionsfor improving the scientific portion of the diver: morepreparation and testing time was necessary to check out equipment and instruct the divers. Makai divers offeredfew corrrrrents about the scientific portion just "fewertests" from oneperceptive individual! . Suggestionsfor improving comfortgenerally noteda needfor better clothingand thermostatically controlled. heating. alsomorc casual space, better bunkingarrangements, and showers.

3. NAACL- ~TodaForm

TheMAACL-T wascompleted each day by five divers. Thegroup-ave»ge responsesonthe three scales ~anxiet, ~he ression, H~ostilit ! werewithin normal ran ge Pi ' g ure lD 0!. A significant difference wasnoted across testing for the~sexist scale 9 = 2,90,df = 8,32,p <,025!. Rangetesting revealed that anxietyy p res onses on Days4, 7, 8, and 9 weresignificantly higher than on Day 1; scores on DaysDa s 22, 3, 5, and6 did not significantly differ f Day 1 scores. Anxietty was as reportedlowest at the end of Day1, and" ghe at the start andend of decompression. ESSION

l4 g 12 LAY

~ 8

2 3 4 5 6 7 8 g DAY 86 l6I l6.I 14 II.5 Q.5 6 3,5 15 PRESRHE ATA ! Figure IO, Daiiy average scores on 3 scales of the HAACL-T n - 5! .

Daily ratings of depression were found to differ significantly F = 2.38, df ~ 8,32, p < .05! . Multiple range tests disclosed that Day 1 ratings oE

depression were significantly lower than any other day. Depression was rated

highest on Days 4 and 6. Hostility scores also differed significantly across

testings F = 2.62, df B,32, p < .OS!, with scores on Day 9 being si~ifi-

cantly greater than those on Day l. No other differences were noted. Ex-

ceptiTLg Day 9, Day 4 and Day 6 hostility ratings were highest. In general,

Day 4 and Day 9 ratings were high on all scales, while Day 6 was high on

depression and hostility.

Daily responsesto the nonstandardizedself'-rating questionnaire pro- vided some insight into diver affect and self-perception of daily experiences.

Some of the more notable items were: ll!, with some elation noted at the start and end of decompression, Measures of Fatigue reflected the difficulty of required tasks on Days 1 through 5, dropping on Day 6, but rising on Days 7 and 8s when comparatively little testing was accomplished. Tension sel f- estimates were generally low, with a slight rise on Day 4 Figure 12!. Mo increase in tension was reported on Day 7 I'thought to be the most dangerous!. Closed In feelings remained slight throughout the dive, peaking on Day 4. Since this feeling dropped again after Day 4, it was taken as a measure of increased anxiety. Subjective impressions of Hot and Cold t'Figure 13! reflected the subjects' inability to establish stable temperature regulation. The comfort zone under He-O~ is narrow, with divers occasionally reflecting conflicting perceptions. throughout the dive, averaging slight-to-moderate, except for an usually perceived to be slightly higher than own sociability, until Day 3 when close agreement between own and group sociability became more consistent. Average semantic differential responses on the Stressful Stressless scale indicate that Day 4 was perceived as less stressful than days preceding and following it, although other indicators identified Day 4 as exceedingly stressful. This apparently reflects some affect repression by the divers, or a coping response to increased anxiety as they entered decompression Figure 14! . Figure 15 depicts semantic differential responses to New - Old and perceived as "Older". Days 5, 8, and 9 were considered as less meaningful than the remaining days.

Figure 16! depict similar temporal shifts. As the tasks became more commonplace, they began to lose meaning. The lack of appro- priate devices to stimulate the divers was evident in the increased boredom noted from Day 5 on. Increased interest was noted on Day 7, when the habitat, shifted to secondary power on entry into the flam- mable zone.

50 INTENSE

ch ~ emmaTE X

«K SLIGHT ELATION

D~~SSION

0 I 2 5 4 5 4 7 4 4 ae ie,i I4.i V II,5 4,5 4 3.5 I.S PRESSURE{ATA! Figurel I. Daily averageself-reports of Elationand Depression n 5! ~

U3 INCITE C9 cf

RIGHT FATIGUE

mVStON

0 I 2 5 4 5 I 7 8 9 I 4.4 Ie,l I4,l Ig Its 8g 6 3.5 N PRESSURE{ ATA ! Figurel2, Dailyaverage se}f-reports of Fatigueand Tensions n

51 LIJSLIQKT HOT

COLD

0 I 2 3 4 5 8 7 8 9 DAY ea iai le.i ~ il.s aS e 35 l.5 PRESSURf

Figure l3. Dal'ly average sel f-reports of Hot and i'-old n = 5! .

IMMODERATELY

VJ 4J SLIGHTLY

QL1$fTLY

a!QQtATKLY

6 7 8 9 DAY 84 I6.I I6.1 % IL5 8.5 6 S,S tS PRFSSURE ATA ! Figurel4. Daily averagesel f-reports on the semanticdifferentia1 saba]e stressful - stressless n = 5!.

52 %AQHTLY MEAMNGFUL-kKAHNCLESS

1KDERAT SLY

IONA

o 1 a a l 3 e T ~ o GAY N.O O,l ILI l4 Ilk lLS ~ 35 LS PRES$tNE ATA !

Figurc I5. Dai iy average self-reports on the semantic differential scales new - old end e~eanin ful - s~eanin less.

HIGHL

NKERlTEL

IIEUTII INTERES T1NG

SUSITTL

ITERATEL

0 1 Il 3 3 e I B.O S, I %.1 Il,e a5 e M I.5 PREMIURE ATA! Figure l6. r}ally averageself-repo rts M the semntlc differentlai sea es DISCUSSION

Notwithstanding the considerable subject variability evidenced, and such administrative difficulties as mistiming and equipment malfunctions, results of the present study provide a consistent indication that human performancecan be significantly impaired under He-0> saturation conditions. As hypothesized,performance on the morecomplex information-processing tasks was more severely affected than were less complex behaviors Table ll!.

TABLEI I. SUMMARYOF BEHAVIORAL CHANGES UNDER HYPERBARI C He-O~ WITHIN STAGES OF A HUMAN INFORMATION-PROCESS ING MODEL

St age Representative Task Results and Comments

Senso ry Peripheral Vision No change. Transduction Depth Perception No change. Incomplete data.! Audiometry Incomplete data. !

Attention React ion Time s imp le! Equipment f ai ! ure. ! Pe rcept i on Reaction Time choice! No change in response time.

.~Iot or Paper Maze Tracing Ss-1! I mpro vement . Train in g e f feet . ! Learnrng Hand Maze Improvement. Training ef feet. ! Gross motor - MRhfI' No significant change. Fine motor Screwplate Some change. Possible reduction in finger control.! Tremor Incomplete data.!

Short -Term Dic»tic Listening Tape No change. Memory

Long-Term Associative Memory Ma-1! Significant reduction in abilitY Memory

Decision Rea ct i on Time c hoi ce! Significant increase in errors. Processes Closure Flexibility Cf-2! Significant reduction in abilitY Inductive Reasoning I-3! Incomplete data. ! Perceptual Speed P-2! questionable format. ! P-3! Significant reduction in ability ~ Spat i al Orient at i on S-1! Significant reduction in ability ~ S-S! Questionable format. ! Math. Ability Dive Tables! Improvement. Training ef feet !

54 Measurementof primary sensory transduction was inade uate for re isel determiningsensory changes due to narcosis. Determinationof purely sensory

changes is difficult in hyperbaric investigations since the intrpductipn pf high pressures and less denseatmospheres may s'erve to alter the physi

characteristics of the system and induce changes unrelated tp narcosis.

There appeared to be considerable hearing loss noted on audiometric

testing in the present study, although there is some evidence for equipment

failure -- possibly loss of earphone sensitivity with increased pressure and

humidity. It is worth noting that the hearing losses occurred in the lower

frequencies, coincident with excessive noise in the same frequency range. Maskingeffects from life-support machinery and magnification of soundsdue to the resonant properties of the steel hull could contribute to a sensitivity loss in the lower ranges. Additionally, the ambient noise level was such that a shift in auditory adaptation level could be expected,further reducing

threshold sensitivity. One observation to be drawn is that the sound level of the habitat is appreciablyhigher than desirablefor extendedexposures, or for operations requiringfine auditorydiscrimination. Audio warning devices and communica- tions equipmentmust be designedto overcomethis backgroundnoise. Some noiseattenuation woul,d be expectedwhen the habitat is submerged,but re-

versible hearing loss could be a problem. giversreported subjective sensations of decreasedambrent »>se with loweredpressure during decompression. Onediver descrrbed th«ffect return of ].owersounds that hadbeen masked by a genera»isy ac"g loweringthe pressureincreased the audibility of lowfr q e" y " ther investigation of this phenomenonis required before efore any conclusions can initial interpretation of the obtainedaudiometrau data is that the noise level in Aegir is excessive,that there is somephenomenological

55 alteration in the hearing spectrum with increased pressure, and that audio- metry equipment may be subject to hyperbaric interference.

Vigilance functioning at depth was not impaired; speed of reactions remained consistently high throughout the dive. Thus, helium at 16 ATA does not appear to affect the arousal function of the RAS, a result contrary to effects of nitrogen narcosis Bennett, 1965; Dickson et al,, 1971, Kiessling

4 Maag, 1962; and others! . The significant increase in error responses with reaction time deserves further comment, however. Apparently the diver ex- posed to hyperbaric He-0~ can perceive stimulus onset adequately, but his ability to respond with the appropriate behavior is significantly impaired.

While choice reaction-time studies with compressed air have reported speed and error changes, performance under helium conditions disclosed no speed change but significant errors. Moreover, there was a tendency for errors to increase throughout the dive, rather than remain a direct function of pressure. This continued increase in error responding on Day 7, at the relatively less narcotic pressure of 6 ATA, suggests the existence of addi- tional factors influencing response behavior. Loss of subject motivation after a week of repeated testing would be an appropriate expectation, but the cons istency of response times, as well as sustained performance on other measures e.g.: Hand Maze, MRMTand Screwplate Test! indicates that the divers maintained their interest, or general behavior, at an acceptable leve~

An alternative explanation might postulate a cumulative effect of hell~ breathing wit»ncreasing inert-gas tensi.on over time, maintaining an appre- c i able 1 eve1 of narcosis . There is no corroborating empirical evidence for this hypothesis. Indeed, there is ample evidence to indicate adaptation to narcosis over continuous exposures Bennett, 1965, 1966; Burnett, 1955; Case p Haldane, 1941; Kies sling Q Maag, 1962! .

56 A more plausible explanation for the decreaserease in responseaccuracy is the degree of stress experienced by the divers at thee imetime o testing. Anxi ety by itself can facilitate or disrupt performance depend-epen ing on the degree of stress experienced, the complexity of the task, and the personality of the individual e.g., Appley 4 Trumbull, 1967; l,azarus, 1966; Martin, 1961; Shapiro g Crider, 1969; Winkel 5 Sarason, 1964!. Although modified by person- a],ity variables, it appears that increased arousal improves performance to a point; however, excessive anxiety can interfere with efficiency. Keybrew l967! noted that studies of long-duration performance space flights, etc.! have established a positive relationship betweenarousal level and performance efficiency. There is also someevidence that anxiety disrupts complexbeha- viors more than simple activities Martin, l96l!. Responsesto the anxiety scaleof the MAACL-Tindicate increased anxiety duringdecompression. All divers recognizedthe decompressionperiod com- mencingaround 5 ATAas the areaof high flammability,as well as the region of increasedsusceptibility to decompressionsickness. Suchhigh stress increasesarousal, whichcould improve performance on the reaction-timespeed measure,but possiblyinterfere with morecomplex decision-making ability. Bennett966! notesthat stressdirectly influencesthe severityof narcosis.Thus, an alternative explanation presents the possibility that high anxiet>during decompression increased subject narcosis and i~paired reaction- timeperformance. Bennett, poulton, Carpenter and Catton 967! alsospecu- late that increasedlevels of arousaldue to highapoise and temperatures encounteredduring compression might influence the narcotic effect of inert gases.Interestingly the authors hypothesize thatdue to arousal,individuals tendedto workfaster at sortingcards! at depth,but made increasing errors, a finding analogousto that of the presentstudy.

S7 Further evidenceof enhancedmotor performanceduring decompressionmay be notedfrom the HRK'time-to-completion scores for Placingand Turning subtasks. There wasa strong trend .l0 > p > .DS! for both of these measures, indicating improvedmotor coordination on Day 7 over that of Day 3. Perfor- manceon the ScrewplateTest also improveddramatically on Days 8 and 9. However,there was a concomitantsignificant increasein errors components dropped!. Although this result appears similar to that for Choice Reaction Time, the tasksare very different: onerequired decision-making based on past learning,while the other entailed finger manipulationsduring transfer of screwsand nuts. It is thoughtthat Screwplateerrors resulted from in- creasedspeed. The significant improvement in MRMI' and Screwplate scores duringthe Laterphases of thedive may reflect characteristics of a learning function plus increasedmotivation as competitiveaspects of the task in- creased. Increasedcomponent loss on Day9 maysimply be a result of this increasedspeed; however, losses on Day 2 maybe dueto pressureor stress

effects. HandMaze results alsodemonstrated significant improvement over tijne, as didMl&l' and the Screwplate Test. Withthese relatively simplemotor- coordinationtasks there is the possibility that skill acquisition,or motor learning,was impaired during the periodof maximumnarcosis and improved during the later trials underreduced pressure. Considerable research is necessarybefore the effectsof continuousexposure to hyperbaricenvironments, excessivenoise, andproLonged stress on humanlearning capabilities can be

adequately understood. Thetwo tasks thought to measuredifferent aspectsof humanmemory processingprovided some indication as to the level of taskcomplexity necessaryto demonstrate He-Oz narcotic interference. The Dichotic Listening Tape,recognized as a sensitivemeasure of short-termor immediatememory, did not register a performancedecrement under pressure owever,the Asso- ciativeMemory task, a paper-and-penciltest requiring rote lear ing of picture-numberPairs, appearedto be moresusceptible to narcosis ~d demon stratedan aPpreciable reduction in performancewith increasedpressure, Thatshort-term memory was unaffected by heliu~ narcosisis an important, but expected,result. Lossof short-terminformation storage would severely handicap a diver. Although associative memoryexhibited a 25't decrementunder pressure, the test results indicate that learning underhyperbaric He-0 is still possible,although it maybe slowerand involve more errors. Complex decisionfunctions could be impairedwith loss of long-termmemory, possibly exaggerating deficits in choice reaction time. However,performance impair- ment was not sufficient to incapacitate the divers; rather, it took reasonably sophisticated measurementsto detect reductions of memorycapability. Eye- handcoordination, gross and fine motor-skill acquisition,and reactionspeeds all appearedminimally disturbed at maximumpressure. As long as the beha- viors required of a saturation diver are learned ski lls, the effects of He-0~ narcosis can be minimized.

Of the several tests purporting to measure cognitive ability, those found effective in determining a behavioral decrement with increased pressure were: flexibility of closure, perceptual speed, and spatial orientation. Additional perceptual speed and spatial orientation measures failed to demonstrate this effect, but both were felt to be inappropriately constructed or otherwise unsatisfactory for inclusion in the test battery.

It appeared that substitution of dive-table calculations for the more standardized mathematics tests commonly employed was inappropriate, Although the tables possessed some face validity as a dive-oriented functional task, scoring and training artifacts appear to have adversely affected the results There was a significant improvement in time per operation on the dive tables upon reaching 16 ATA, although an attendent increase in errors was also found.

The dive-table computations successfully countered negative motiva- tional characteristics associated with repeated administrations of simple mathematics problems, but no attempt was madeto achieve a plateau in the subjects' proficiency through practice trials, to counter potential learning effects. The assumption that experienced divers would be familiar with the standard ~Vavyprocedure proved unfounded; several divers reported little experience with the tables, at least in the form presented. Although one function of this investigation was to reduce the considerable variation in testing instruments noted in the literature, the introduction of dive tables appeared justified as an effort to develop sensitive instruments appropriate to the diving environment. That they served only to proliferate nonstandard- ized tests and to obfuscate the effects of helium narcosis was an unfortunate judgmental error.

Further consideration should be given to development of tasks consistent with dive requirements, since task complexity has been found to be an impor- tant variable in assessing the effects of narcosis. Additionally, requisite diver operations should be practiced to produce a stable level of skill per- formance, diminishing the necessity for cognitive involvement. Two test batteries specifically designed for underwater testing have been suggested

Egstrom $ Neltman, 1968; Reilly g Cameron, 1968!; both purport to include motor-skill and mental-ability measures, but neither was available for inspection for this study. Further exploration of appropriate measurement techniques is essential for understanding the effects of inert -gas narcosis

The results of the present study appear applicable to a wide. body of divers; the divers chosen for the study exhibited a normal range of personalit>

60 and motivational differences. However, their saturatipn diving experience wasnegligible, unlike divers chosenfor recent record dives. There is spme evidence that adaptation 'to narcosis exists with repeated exposures Adolfspn 1965; Adolfson5 Muren, 1965; Thomas5 Bachrach,1971; Walshg Bachrach,1971!. It is possiblethat the significant effects noticedin the presentstudy wpulddiminish with continueddiver experience;however, observation of responsesby the single experiencedsubject failed to identifyany major

behavioral differences based pn experience. Selectionof subjectsfor participation in field investigationssuch as this encountersseveral difficulties. First, the training aspectof the dive wasover-emphasized andcould have had a detrimentaleffect on datacollection in less carefullymonitored circumstances. It is recommendedthat subjects bemade aware that responsibility to the scientific mission supersedes personal orprofessional aggrandizement. Thiscould be accomplished byproviding adequateunderstanding ofthe experimental designand the tasks required of them,and through structuring the investigation to involve every member in a responsibleposition. A furtherdifficulty exists where anindividual subject tonarcosis and stress is placedin chargeof data collection, increasing the opportunityformissed assignments andtechnological errors. Where feasible, externaltest administration should be introduced butstructured to minimize antagonismand "topside interference".

61 CONCL US I ON

The existence of helium narcosis at 16 ATAwas supported, where narcosis

was defined as a reduction in behavioral effectiveness. Moderate loss in

cognitive ability was noted at maximumpressure, while little decrement was

evidenced in behaviors requiring less cognitive involvement. This result is in agreementwith Sennett's hypothesisthat narcosis is a function of synaptic

blocking in the &S.

While moderateperformance loss was experienced -- up to 25% decrement in associative memoryability -- the divers' capacity to function effectively

was not seriously impaired. However, attention must be drawn to the careful design of diver tasks, the need for extensive training on emergencyproce- dures, and the need for reduction in complexdecision-making alternatives, to diminish susceptibility to error. Motor coordination, vigilance respond- ing, and sensorymechanisms appeared to be minimally affected by He-O~expo-

sure. The possibility of performance alteration due to increased arousal exists, particularly during stressful decompression;the direction oi change appears a function of task complexity. Divers maybe able to function adequatelyto depths of 2000 feet, but there is somequestion as to the degreeof task complexity they are capable of performingcorrectly at that depth. Until moreprecise measurementsof the narcotic effect of helium are secured, there is still somereservation possible concerningman's ability to function at peak effectiveness in a hyperbaric environment,

62 APPENDIX

NONSTANDARDIZEDTESTS

A. DAILY SELF-RATING SCALE

B. POST-DIVEQUESTIONNAIRE AND PERSONAL HISTORY SCHEDULE C. STANDARDFORN FOR DECOMPRESSION TABLE MATHEMATICS TESTS REPETITIVEDIVE l40RKSHEET!

63 AEGIR I/72

A. DAILY SELF-RATING SCA1.E

Part A. Following each item below, place a check mark under the word which best describes your feeling about the item,

A. Elated B. Depressed C. Fatigued D. Tensed Up E. Closed In F ~ Cold G. Hot H. Own Saciability I. Group Sociability J. Own Interest in P K. Group Wish to quit pro!

Part B. Selow are several pairs of words, each pair forms a scale. Place a check mark along the scale in the location that best describes your feelings about the dive ~toda

64 B. AEGIR SATURATION

Age: Occupation:

1. Prev ious d iving exper ience:

No. of years of SCUBA: No. dives per year: approximate average! No . of years skinning:

Hp. of years Hard Hat:

Other spec if y!:

2. Forrnal Education: check!

a. less than high school d. sose college

b. some high school e, college

c. high school f . gradua t e t ra in ing spec i f y degr ee 6 ma] or!

3. Special Tra ining: List any special training courses or certificates that might be relevant tp your occupation and/pr the AEGIRdive:

4. What is your marital status7 Ho. of children:

5. If married, what was your age at marriage?

6. How many older brothers do ypu have? Hpwmany younger brothers do you have? Howmany older sisters do you have? Howmany younger sisters do you have? 7- Whydid you volunteer for the AEGIRdive? 8. Describe briefly your role on the AEGIRdive. 9. Whatdid youconsider the mostimportant aspect of 'thedive? 10' What did youconsider the mostcritical or dangerous!point in thedive', ll. Doyou think yourparticipation in the divewas valuable? Why? FOR THE NEXT QUESTIONS CIRCLE THE APPROPRIATE ANSWERS:

12. On the whole the dive was: A. extremely unsuccessful E . s lightly successf ul B. moderately unsuccessful F. moderately successf ul C. s 1 ight 1y unsuccess f u1 G. extremely successful D. neither successful nor unsuccessful

13 . On the whole I. found the dive to be; A. extremely enjoyable E. slight ly not en joyab le B. moderately enjoyable F. moderately not enjoyable C. slightly enjoyable G. extremely not enjoyable D. neither enjoyable nor not enjoyable

14 . My interest in the scientific aspect of the dive was:

high B. moderate C. low

It A. decreased from the beginning to the end of the di vo. B. remained the same C. inc reased

15 . I A. wou ld participate on another dive similar to this. B. would not

16. On the whole the dive was A. easier than I had expected. B. the same as C. more difficult than

17 . The scientific tasks were A. easier than I had expected. 5. the same as C, more difficult than

18 . Generally, 1 feel the dive altered my social behavior A. positively extremely E. negatrvely slightly B. positively moderately F. negatively moderately C. positively slightly G. negatively extremely D. no change at all

20. Hy status in the group probably A. increased because of my perfo B. remained the same C. decreased

21. I was bothered most by: Circle all appropriate answers! A. changing pressure effects B. diet C. giving blood D. physiological exercises E. psychological tests F, T.V. and open mike surveillence G. sleeping arrangements and times H. social conditions I. inability to verbally communicate well J. noise level in the habitat K. crowded space in the habitat L. others:

66 22. List any suggestions for improving the scscient' enti fiic aspect of the dive:

23. List any suggest i,ons f or improving the comfortom ort an d ll-b well-being of the divers:

PLEASEANSgPR THE FOLLOWINGQUESTIONS BY FILLING IN THEAPPROPRIATE NARES BE SURETO INCLUDEYOURSELF WHERE APPROPRIATE. all information will be strictly confidential, of course.! 24. Based on your experiences during the dive if you were to permanentfriends from the membersof the experimentvho would be your first three choices7 l.

2 ~

25. Of all the membersof the habitat crewwhom do you considerperformed most competently in their respective roles". Taking into consideration that each memberhad a slightly different job on the dive.! l.

2.

26. Which membersof the diving crewdo you consider most able to get along with the other members? l.

27. Recognizingthat pressure, noise, exercise, helium-speech, etc. effeet individuals dif ferently, whichdivers were most seriously af fected by the dive while "on the bottom"' l.

Feelfree to usethe remainder>f the paper to registerany comments aboUt thedive, thepattie ipa its, or t~e,»ychologicaland physiological tests.

67 C. REPETITIVE DIVE WORKSHEET+

I. PREVIOUS DIVE:

minu.tes aee table 1-5 or 1-6 for Group feet repetitive group designation

II . SURFACE INTERVAL;

hours minutes on surface see table 1-7 Group Group from I.! for new group

III . RESIDUAL NITROGEN TINE:

aee table minutes Group from II.! 1-8

IV. EQUIVALENT SINGLE DIVE TINE:

minutes residual nitrogen time from III,! dd! minutes actual bottom time of repetitive dive!

sum! minutes

V. DECONPRESSION FOR REPETITIVE DIVE:

minutes equivalent single dive see table time from IV.! feet depth of repetitive dive! l-5 or 1-6

No decompression required or Decompression stops: feet minutes

feet minutes

feet minutes

feet minutes

'Reproduced from U.S. Na~ Diving Manual- NAVSHIPS!250-538. Washington, D. C. l963. Ackles, K- Ns3 6 Fowler, B. Cortical evokedresponses and inert gas narcosis in A~erosace Medicine, 1971, 43, 1181 1184

Adolfson,J. Deterioration of mental and motorfunctions in hyperbaricair. EcsndanavianJournal of P~scholo , 1965, 6, 26-31. Adolfson,J., 6 Pluur, K. Hearingdiscrimination in hyPerbaricair, A~erosacs Medicine, 1967, 38, 174-175.

Adolf son, J s9 6 Huren, A. Air breathing at 13 atmospheres. psychological and physiological observations. ~Sertck ur Fot'searsM~ed ~c 1965, 1, 31-37,

9~tinct les and observations on the E rfsio~io~ of the scubadiver. Arlington, Virginia. Of fice of Naval Research, 1970,

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