Nobuo Naraki

Sleep patterns during 30-m nitrox saturation dives and in a confined atmospheric environment.

Abstract Sleep patterns during saturation dives equivalent to a 30‐m depth (pressurized condition) and habitation in a confined environment at 1 atm absolute pressure (non‐pressurized condition) were studied to determine the effects of environmental pressure. Eight inexperienced divers experienced the pressurized condition of the saturation dives, and nine healthy subjects experienced the non‐pressurized condition. Standard polysomnographs were recorded for 262 nights. For both conditions, reductions in total sleep time accompanied by lengthening in sleep latency and reduction in sleep efficiency were observed from the latter part of the experiments through to the recovery periods. These findings suggest that changes were related to psychological and physiological stresses caused by long stays in a confined environment and not by the environmental pressure.

Changes in sleep patterns during simulated nitrox saturation diving to 20 and 30 meters.

This study assessed the effect of a nitrogen-oxygen (N2-O2) saturation diving environment on nocturnal sleep and the differences in sleep on diving depth. We measured and recorded the standard polysomnograph and heart rate for a total of 459 nights on 27 divers who performed the N2-O2 saturation simulation dive at 20- and 30-m equivalent depths as well as their subjective feelings of fatigue. From the last half of the period on the bottom to the postdive period of both saturation diving depths, our main findings included a prolongation of sleep latency, shortened total sleep time, a decreased sleep efficiency index, and increased feelings of fatigue. During the bottom period and decompression period, the total number of awakenings and the awakenings from rapid eyes movement (REM) sleep increased. This was slightly greater at the 30-m equivalent depth. From these facts, we assumed that the deterioration of sleep at the 20- and 30-m nitrox saturation dives was predominantly relative to being restricted in a closed environment for a long time and the lack of physical activity of the divers. No recovery of sleep was observed in the postdive period. A difference in the effects on sleep by the dive depth was not found.

Sleep patterns during 30‐m nitrox simulated saturation dives

The sleep patterns were examined during the simulated 30‐m nitrox saturation dives. The standard polysomnography of 15 divers was recorded for a total of 255 nights, as were patterns of change or consistency in sleep variables. A reduction of total sleep time in accordance with the lengthening of sleep latency and the wake after sleep onset was observed through the latter part of the bottom period to the post‐dive period, but the other sleep variables did not show any changes. These findings suggest that decompression and the psychological stress due to being in the closed environment of a hyperbaric chamber for a long time have effects on divers’ sleep.