Chapter 35 



NEUROLOGICAL, EEG, AND PSYCHOPHYSIOLOGICAL 

 FINDINGS BEFORE AND AFTER SEALAB II 



Laverne C. Johnson and Michael T. Long 

 U. S. Navy Medical Neuropsychiatric Research Unit 

 San Diego, California 



INTRODUCTION 



Neurological, EEG, and psychophysiological examinations were obtained before and after 

 Sealab 11 to determine possible changes resulting from prolonged exposure to a hyperbaric en- 

 vironment. The psychophysiological variables included heart rate, respiration rate, skin re- 

 sistance, and finger plethysmogram. The postdive examinations were completed 12 to 36 hours 

 after decompression. No significant predive or postdive neurological or EEG changes were 

 found. While marked individual differences were found in the psychophysiological variables, 

 the only significant difference was a drop in arousal level from predive to postdrive. 



While the laboratory findings of Genesis E (Workman, Bond & Mazzone [1], Lord, Bond, 

 & Schaefer [2], Bond 1964 [3] and the data from Sealab I indicated that man could exist and 

 perform useful tasks in a hyperbaric environment, Sealab n was the most stringent test to 

 date of man's ability to live in the sea. The potential hazards of this unusual environment are 

 many, but of primary concern for this report are the neurological hazards of diving and the 

 neurological and psychophysiological effects of prolonged exposure to unusual concentrations 

 and pressures of gases. 



The neurological problems posed by decompression, air embolisms, inert-gas narcosis, 

 and oxygen toxicity have been summarized by Gillen [4, 5]. The effect of high partial pressures 

 of inert gases on EEG and measures of performance have been reported by Bennett & Glass [6] 

 and Bennett [7]. Under hyperbaric conditions they found subjects were less efficient on 

 problem -solving tasks and that alpha blocking to stimuli was absent. 



The effect of varying ambient pressures and varying gas mixtures on psychophysiological 

 variables has not been extensively studied. The only known report is that of Weybrew, Green- 

 wood and Parker [8] who studied three subjects during a 12-day exposure to an atmosphere of 

 helium, oxygen, and nitrogen. Outside of a general indication of arousal in two of the subjects, 

 no definitive conclusions could be drawn from this small sample. 



As part of the pre and postdive examinations of the divers participating in Sealab II, neuro- 

 logical, EEG, and psychophysiological data were recorded. During Sealab 11, three teams of 

 ten men spent 15 days 205 ft below the ocean's surface. One of the participants spent 30 con- 

 tinuous days in the habitat, and a second participant spent 30 days in two 15-day periods, inter- 

 rupted by a period of 15 days. The Sealab environment consisted of the following atmosphere: 

 temperature 82 to 88° F, humidity 60 to 80 percent, pressure 6.8 atmospheres, and the average 

 composition of the major gases was oxygen 4 to 5 percent, nitrogen 21 to 22 percent, and 

 helium 73 to 75 percent. As the postdive examination could not be performed before 12 to 36 

 hours after the decompression, it was not expected that transitory changes, if present at all, 

 would still persist. Our examinations were oriented toward determining if there were any 

 changes that might be chronic. Recordings of EEG activity during the dive for Teams 1 and 2 

 were done by Dr. Carl W. Sem-Jacobsen (Chapter 34). 



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