Ambient air, oxygen and nitrox effects on cognitive performance at altitude.

The effects on cognitive performance of breathing air, oxygen and nitrox gas mixtures at surface ambient pressures were investigated during an expedition to the Everest region of Nepal. A slight improvement in grammatical reasoning at altitude was found under nitrox (p < 0.05) and mathematical reasoning showed improvement at altitude on air (p < 0.05), oxygen (p < 0.01) and nitrox (p < 0.01). There were non-significant trends towards decreasing mathematical ability, coupled with an increase in variance on both grammatical and mathematical test performance, with increasing pO2 (all p > 0.05). The results suggest that there is a subtle interaction on cognition as indicated by a significant three-way interaction between subject x altitude x gas (p < 0.05).