PHYSCHOPHYSIOLOGICAL FINDINGS 243 



While there was marked variability about the mean on both predive and postdive records, 

 all basal mean values were within normal limits. The predive range for heart rate was from 

 48 to 107 beats per minute, while the postdive range was from 45 to 110. The same two men 

 provided the minimum -maximum pre-postdive scores. This stability in pre-post heart meas- 

 ures is reflected in the 0.69 (p < .01) correlation between pre-post heart rate values. For 

 respiration rate the predive range was from 8 to 21 breaths per minute, and the postdive range 

 was from 9 to 20. The correlation between pre-postdive respiratory rates was 0.65 (p < .01). 



Similar wide ranges were found for skin conductance and the measures of spontaneous 

 fluctuation in basal values. In contrast to the significant pre-postdive correlations for heart 

 rate and respiratory rate, the pre-postdive correlations for skin conductance and spontaneous 

 activity were not significant, indicating marked and inconsistent individual fluctuations in these 

 measures of basal variability. 



The only significant difference between the predive and postdive basal means was for skin 

 conductance. The predive conductance mean was significantly higher, reflecting the higher de- 

 gree of arousal before the dive. These data are consistent with the EEG findings of more 

 drowsy records and quicker onset of sleep during the postdive examinations. 



Though there was a larger response in all variables to the flicker on the predive than on 

 the postdive record, only the number of spontaneous GSRs during flicker was significantly 

 higher. These findings, especially the GSR data, are in keeping with the difference in arousal 

 level between the two examinations. 



CONCLUSIONS 



Prolonged exposure to the hyperbaric atmosphere present during Sealab 11 appears to have 

 had no prolonged deleterious effect on man's central or autonomic nervous systems. Any 

 changes precipitated by exposure to this atmosphere of helium, oxygen, and nitorgen under 6.8 

 atmospheres were transient and no longer evident by our recording techniques 12 to 36 hours 

 after decompression. 



The postdive interview data, however, suggested that some transient effects were present, 

 especially during the initial period of the dive. Headaches were evidently not uncommon, some 

 slowing of mental processes were reported, sleep patterns appear to have been disrupted, and 

 changes in affect, i.e. euphoria, were reported. Dr. Sem-Jacobsen, while experiencing many 

 technical problems in this first attempt to record EEG changes from men during the dive, did 

 obtain data suggesting that EEG changes may be present and correlated with variations in gas 

 pressures. 



These clinical reports and the suggestive EEG findings indicate that some detailed and re- 

 liable EEG and psychophysiological recordings during the dive would be of value, especially 

 during the initial periods. When compared with predive baseline data, these data could deter- 

 mine the initial effects of the environment on each man. Changes in the EEG or psychophysio- 

 logical variables during the dive could also be used to indicate the effect of prolonged exposure 

 and possible changes in performance level. 



The wide range of predive basal values and the negative postdive findings indicate that the 

 ability to adjust to atmospheres and gas mixtures such as those in Sealab n is not restricted to 

 a narrow band of physiological values. It would be of interest to determine whether the predive 

 data could be used as predictors of initial or prolonged response to hyperbaric environments. 

 As the dives proceed to greater depths and for longer periods, the predive data may be of 

 greater significance. 



The negative postdive data can be viewed as a confirmation of the results from the Genesis 

 experiments and Sealab I. Sealab II further demonstrated man's ability to expand his sphere of 

 aquatic activities. The lower level of arousal on the postdive examination was probably due to 

 the fatigue and sleep loss resulting from the decompression schedule and demands upon the men 

 for reports and interviews post decompression. The sleep difficulty experienced during the 

 dive also added to the sleep debt of some of the divers. 



