THE VITAL CAPACITY OF THE LUNGS AT LOW BAROMETIC PRESSURE

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Abstract
A decrease in the vital capacity of the lungs was obtained by subjecting [24] men to a reduced barometric pressure in a low pressure chamber. Individual differences occurred; no one experienced the change at less than a simulated altitude of 10,000 ft., while in the majority this occurred at simulated altitudes of 12,000-15,000 ft. The use of an extra supply of 0 prevented the effect in part in some men and wholly in others. Measurement of the circumference of the abdomen showed that the decrease in vital capacity is not the result of the expansion of intestinal gases. On Pike''s Peak, altitude 14,110 ft., the vital capacity was decreased during the 1st day or 2 by 6.7-15.3% in 9 men. Later all men showed at least a partial return to normal. With acclimatization the recovery was complete. During the period of reduced vital capacity the administration of O caused a partial recovery. A low atmospheric temp. was shown not to be the cause of the decrease. It is suggested that the reduction in vital capacity is due to an engorgement of pulmonary blood vessels, that reserve capillary paths are brought into requisition, and that possibly there is a relaxation of pulmonary capillaries as a result of anoxemia. The beneficial effect obtained by the administration of 0 may be due to restored capillary tonus.

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