Effects of anoxia on performance at several simulated altitudes.

Abstract

Twenty-nine individuals were given "flights" at one or more simulated altitudes of 10,000, 14,000, 15,500, and 18,000 ft., in a low pressure chamber. The subjects were given a cycle of 3 tests (critical flicker frequency, perimetry of the visual field with a red target, and body sway) once at sea level before "ascent", 5 times during an hr. under the anoxic conditions, and once more immediately upon return to sea level. Critical flicker frequency and perimetry can be used to detect changes in performance of small groups of subjects under anoxic conditions (10,000 ft. and above). Body sway measurements can be employed to demonstrate differences in performance at 14,000 feet and above. The magnitudes of most of the changes are such that individual scores are within the normal distribution of values at sea level and thus cannot be used as criteria, in a clinical sense, of the extent of anoxia in the individual. The lack of correlation between performance decrements in the tests suggests considerable variation in the underlying physiologic adjustments to anoxia.