Effects on sleep patterns during simulated oxygen-helium saturation diving at 180 and 230 m

The standard polysomnography of four divers was recorded respectively through 188 nights in two simulated experiments under a hyperbaric saturation environment of He-O2 mixture at the depths of 180 and 230 m. In the two diving conditions on the bottom nights and decompression nights, the following was shown: A reduction of total sleep time, a decrease of sleep efficiency; an increase of sleep latency, frequency of wake after sleep, number of sleep stage shifts, and a lengthening of stage 1 sleep; and a reduction of stage 4 sleep. In the 230 m-diving condition on the bottom nights and the decompression nights, only stage 4 sleep showed a significant decrease when compared with the 180 m-diving condition. It is assumed that both were conditions in which awakening was likely to happen and there would be no disorders of fundamental sleep patterns.