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