Cognitive performance, sleep quality and mood during deep oxyhelium diving

This study forms part of a series of simulated saturation oxyhelium dives, examining physiological and psychological changes in man in high pressure conditions. A series of five dives are reported, lasting between 18 and 26 days, and reaching maximum depths of between 300 and 540msw. Tests of cognitive functioning, including associative and short term memory, arithmetic ability, perceptual speed, spatial manipulation, grammatical reasoning and semantic processing, were administered to well-practiced subjects prior to each dive, at maximum depth and again during decompression. Self-report measures of sleep and mood questionnaires were administered for a period extending from 1 week before each dive commenced until at least 1 week after the dive was completed. The results indicate significant impairments in all performance tasks at maximum depth, except for the tests of associative memory and grammatical reasoning. A significant reduction in sleep and decrease in the subjective level of alertness was found at maximum depth for all dives. However, correlational analyses suggest that it is unlikely that these are responsible for the clear decrements observed in cognitive performance at depth.