Electroencephalographic Changes During Saturation Excursion Dives To A Simulated Seawater Depth Of 1000 Feet.

Abstract : EEG records were obtained in two Ss during saturation excursion dives to 1000 ft. depth. Computer analysis produced the following findings. During the compression to saturation depth of 800 ft. at a rate of 3.5 ft./min similar EEG changes were observed in both Ss consisted of : (1) lowering of the mean frequency, (2) decrease in the percentage of fast waves (18 - 50 Hz), (3) increase in the percentage of 6 - 8 Hz waves (theta activity). During the subsequent saturation period at 800 ft. the EEG changes observed during the compression to 800 ft. were reversed within 14 hours in S C.D. and 18 hours in S D.F. which indicated that the EEG changes found during the compression phase represent a compression syndrome. During the latter part of the 36 hours saturation period at 800 ft. and the subsequent decompression period S C.D. exhibited a consistent decrease in mean frequency and an increase in percent of 6-8 Hz frequency (theta activity) which appeared to be correlated with an increase in CO2 excretion in the urine and a decrease in alvelor CO2 tension suggesting a hyperventilation effect. Inhalation of nitrogen-oxygen mixtures (3. 5 Atm N2, 1.4 Atm O2) at different depth levels during compression produced in both subjects symptoms of narcosis, performance detoriation and EEG changes at the lower depth level. At greater depth levels no symptoms of narcosis or performance changes were observed but slight changes in the EEG occurred.