Abstract: During the simulated heliox saturation dive at the depth of 302 m.,some neurophysiological and psychological functions of the 3 subjectswere observed through the senses of the subjects and psychological tests.The results showed that simple visual reaction-time was prolonged by7.3%, 4.5% and 6.5% during the compression from surface to 200m, 250mand 302m respectively. The error ratio of mental test in book-answerway increased by 156.4% at the interim stop of 200m. During compressionto 250m, the ballbearing rate decreased by 12.2% and the error ratioincreased by 27.6%. After staying at 302m. for 1 day, the simple visualreaction-time was prolonged by 6.1%, the ballbearing rate decreased by11.3% and the error ratio increased by 56.2%, the sorting card timewas prolonged by 8.7% and the error ratio of mental test in book-answerway increased by 113.8%. All the changes mentioned above returned tothe control levels after the beginning of decompression or reaching thesurface. The symptoms of HPNS of the subjects were light, which mightbe related to the slow compression rate and interim stops.

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