Changes in sleep patterns during simulated heliox saturation dive at 16, 19, and 24 ATA

The purpose of this study is to examine sleep structure under the hyperbari c environment to obtain fundamental data so that a desirable sleep environm ent for divers may be organized using the polysomnography. Using standard p olysomnography, the total sleep time (TST). sleep efficiency index (SEI), n umber of awakenings (No A), lengthening of stage I sleep (LS IS), and lengt hening of stage 4 sleep (LS4S) for 12 divers were measured over a period of 268 nights in three simulated conditions under a hyperbaric saturation env ironment of a He-O-2 mixture at a depth equivalent to 16, 19. and 24 ATA. I n the three diving conditions during the bottom nights and during the decom pression nights (at 16 19, and 24 ATA), the statistically significant resul ts were shown: a reduction of TST, a decrease of SEI, an increase of No A a fter sleep or from rapid eve movements (REM) sleep. a LSIS deviation, and a reduction of LS4S deviation. The amount of LS4S was largest in the 16 ATA diving condition on the bottom nights and the decompression nights., and te nded to decrease in order of 19 and 24 ATA diving conditions. The No A from REM sleep and interruption of REM sleep were significantly higher on the b ottom nights and decompression nights than predive nights, and tended remar kably to increase in the order of 16-24 ATA on decompression nights. The sl eep patterns under the three saturation diving conditions showed disorders in the bottom nights and decompression nights. However. these disorders con tinually worsened with increasing depth from 16 to 24 ATA. The psychologica l stress in the divers that gives rise to sleep disorders is caused by comp ression and decompression and from long periods of stay under closed condit ions. (C) 2001 Elsevier Science B.V. All rights reserved.