EFFECTS OF NORMAL AIR AND DEXTRO-AMPHETAMINE UPON WORK DECREMENT INDUCED BY OXYGEN IMPOVERISHMENT AND FATIGUE

Following medical examination and familiarization with mask breathing and leak-check procedures, 64 young, basic airmen volunteers were given 50 min. of practice at a compensatory pursuit task involving simulated aircraft indicators and controls. Upon completion of practice, subjects were randomly assigned to two drug treatments, placebo and d-amphetamine, 5 mgm., and then required to perform the work task for 4 consecutive hours at ground level. For the first 2 hours of work, all subjects breathed a nitrogen-oxygen mixture containing 12 per cent oxygen. During the third hour, they breathed a nitrogen-oxygen mixture containing 21 per cent oxygen and for the fourth hour of work, all subjects were returned to the nitrogen-oxygen mixture containing 12 per cent oxygen. In the placebo group, normal air completely arrested proficiency degradation induced by the combined effects of hypoxia and fatigue and sustained proficiency at a constant level throughout the period that normal air was breathed. In the d-amphetamine group, normal air did not produce further proficiency increment. Instead, the efficacy of d-amphetamine was augmented to the extent that decline in proficiency which otherwise would have occurred was postponed throughout the period concerned. Returning the placebo group to an insufficiency of oxygen resulted in a reestablishment of the rate of proficiency decline that existed prior to the interpolated period of normal air. Returning the d-amphetamine group to oxygen insufficiency also resulted in proficiency decline which progressed, moreover, at a rate no different from that of the placebo group.