Cognitive performance deficits in a simulated climb of Mount Everest: Operation Everest II.

Cognitive function at simulated altitude was investigated in a repeated-measures, within-subject study of performance by seven volunteers in a hypobaric chamber, in which atmospheric pressure was systematically lowered over a period of 40 d to finally reach a pressure equivalent to 8,845 m, the approximate height of Mount Everest. The portable cognitive test battery used, Automated Performance Test System (APTS), was specifically designed for field research under adverse environmental conditions as evidenced by compact computer design; automated test administrations, data storage, and retrieval; psychometric properties of stability and reliability; and factorial richness. Significant impairments of cognitive function were seen for three of the five tests in the battery; on two tests, grammatical reasoning and pattern comparison, every subject showed a substantial decrement. The results are discussed in terms of the impact of altitude on specific aspects of cognitive function and the importance of having sensitive and reliable instruments to monitor such effects.