EFFECT OF METHEMOGLOBINEMIA ON THE VISUAL THRESHOLD AT SEA LEVEL, AT HIGH ALTITUDES, AND AFTER EXERCISE

Abstract

Concns. of met-Hb up to 30% were induced without showing any definitely significant effect upon the rod threshold in dark adaptation either at sea level or at simulated high altitudes of 12,000 ft. and 18,000 ft. Short bouts of severe exercise lowered the rod threshold immediately after exercise in methemoglobinemic individuals, but not in normals. However, 5 to 10 mins. after exercise, the threshold rose above the normal threshold to the same extent in both methemoglobinemic and non-methemoglobinemic individuals. The above findings are discussed with reference to O2 unloading in tissues, and to the effect of exercise on the acid-base balance.