EEG polygraphic sleep study in divers under a 31 ATA He-O2 environment with special reference to the automated analysis of sleep stages

Abstract

This study was performed on four simulated professional divers (31 ATA, PO2=0.4 bar, PN2=0.79 bar) to investigate the function of their sleep polygraphically. All-night electrographical recording to the subjects' sleep was taken from 23:00 until 07:00 the next morming, predive, saturation, decompression, and postdive from Nov. 20 to Dec. 13, 1985. Polygraphic analysis of nocturnal sleep was done by a microcomputer technique developed by us for comparison with visual scoring. This system is a real-time processing system. Therefore, a sleep chart is completed when the experiment is finished. This system was very useful for the analysis of the tremendous volume of sleep records during a nearly one-month experiment. The following results were obtained: In the predive control, total amount of stages of NREM and REM sleep decreased. In the hyperbaric environment at 31 ATA, all the divers had to interrupt their sleep once or twice for nocturnal sleep urination, and also total waking time increased during nocturnal sleep. At 31 ATA, the length and the cycle of the sleep profile vacillated. A high degree of correlation was observed between the sleep profile recorded by the polygraph and the subjective appreciation of sleep.