Medical Observations During 20 Days at 3,800 Meters

Twenty-five healthy young men were studied during 20 days of continuous residence at an elevation of 3,800 meters. Hematocrit levels increased for two weeks, then stabilized. Subjects who were moderately active during their first two days at altitude adapted more rapidly than those whose activity was limited. A number of serum enzyme levels were significantly affected by the exposure. Virtually all subjects reported symptoms of altitude sickness; four were incapacitated at some point. Level of physical fitness prior to going to altitude was not related to incidence or severity of acute mountain sickness. Alarming and sometimes serious symptoms were observed when subjects attempted to work at their sea level capacity; these symptoms responded immediately when oxygen was given.