Abstract
Although many factors contributing to inert gas narcosis onset and severity have been
put forward, the available evidence is not particularly strong. Using objective criteria,
we have assessed brain impairment associated with narcosis under various environmental
diving conditions. 40 volunteers performed a no-decompression dive (33 m for 20 min)
either in a dry chamber, a pool or open sea. They were assessed by critical flicker
fusion frequency before the dive, upon arriving at depth, 5 min before ascent, on
surfacing and 30 min post-dive. Compared to the pre-dive value, the mean value of
each measurement was significantly different. An increase of flicker fusion to 105.00±0.69%
when arriving at depth is followed by a decrease to 94.05±0.65%. This impairment persists
when surfacing and 30 min post-dive, decreasing further to 96.36±0.73% and 96.24±0.73%,
respectively. Intragroup comparison failed to demonstrate any statistical difference.
When objectively measured narcosis may not be influenced by external factors other
than pressure and gas. This might be of importance for training to avoid any over-
or underestimation of the severity of narcosis based only on subjective symptoms.
Key words
diving - inert gas narcosis - flicker fusion - controlled environment
