The Effects of 12 Hours of Low-Grade Hypoxia at 10,000 ft at Night in Special Operations Forces Aircraft Operations on Cognition, Night Vision, Goggle Vision and Subjective Symptoms

This study evaluated the effects of extended exposure to low-grade hypoxia on cognitive function and visual performance (unaided and night vision goggle [NVG] visual acuity). Thirty subjects were exposed to two, 12 hour exposures, one at ground level and another at 10,000 ft altitude in a hypobaric chamber. Half of the subjects performed moderate exercise. Results: Twelve hour exposure at 10,000 feet produced no significant negative impact on cognitive function, but minor negative effects on night vision goggle performance under operational lighting (starlight) conditions. The altitude exposure did not negatively affect unaided night vision performance under twilight lighting. There was a slight increase in self-reported symptoms of headache, fatigue and lack of concentration, but there was no increase in reported symptoms with the moderate exercise. The increased reports of headache at altitude may possibly indicate imminent mild acute mountain sickness. The original document contains color images. Prepared in cooperation with General Dynamics, Dayton, OH.