The influence of simulated saturation diving on electroencephalogram of human at different depths.

Abstract

This paper report on the changes of the EEG of human during simulated saturation diving at different depths with different mixture gases. The results of this experiment show that there appears diffusion slow waves (θ and δ waves). The changes of EEG at 50 m depth were more obvious than those at 36.5 m. With the prolonging of time under high pressure, the EEG had some improvements, for instance, the slow waves decreased and α waves increased. There was a certain relationship between these changes and the physiological symptoms. The chief factor of the changes of EEG is nitrogen narcosis for the oxgen-nitrogen diving. In addition, carbon dioxide retention under high pressure is also a factor because Co2 rebreathing and hyperventilation (i.e. high and low Co2 in body) aggravated the changes of EEG. The main changes of the EEG during helium-oxygen exposure at 302 m depth were the increase of θ waves and δ waves, the decrease in α rhythm and the decline of amplitude of α waves. Increased θ index and decreased α index could be seen at the depth of 302 m. Under any of the above-mentioned high pressure condition, when slow waves were taken as characters in the background in abnormal changes of the EEG, the EEG could be temporarily improved by photic stimulation, that is slow waves disappeared and α waves reappeared. When photic stimulation was over, α waves disappeared and slow waves reappeared. It was indicated that abnormal changes of the EEG under high pressure were a kind of temporary and reversible changes of the brain function.