Moderate Intermittent Hypoxia: Effect on Two-Choice Reaction Time Followed by a Significant Delay in Recovery

Hypoxia continues to be a significant source of peril in military aviation. Over three dozen hypoxia-related incidents were reported in the past decade with three resulting in fatalities (Clark & Megown, 2005; Ostrander, 2008). Previous work has addressed loss of consciousness resulting from extreme levels of hypoxia (Carlyle, 1963); however, most mishaps are related to moderate hypoxia exposure. More work is required to establish the cognitive effects of moderate hypoxia and the time required, post-exposure, to fully recover. The present study examined the effect of a ten minute exposure to an air mixture equivalent to 20,000 ft on two-choice reaction time. Carryover effects were assessed over a ten minute recovery period. Hypoxia exposure resulted in significant delays in two-choice reaction time. Significant carry-over effects continued to be detected throughout the recovery period. This information is essential to military aviation, where high levels of cognitive performance are required after moderate hypoxia exposure.