THE RESPIRATORY METABOLISM OF HUMAN SUBJECTS DURING PROLONGED EXPOSURES TO SIMULATED ALTITUDES OF 8000 AND 10,000 FEET

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Abstract
The respiratory metabolism of 6 men was detd. during exposures (10 hrs.) in the low pressure chamber at simulated 8,000 and 10,000 ft. altitudes without supplementary O2 under standardized restricted food intake. The respiration increased at both altitudes studied. The augmented respiration involved increased depth rather than increased frequency of breathing, and the modifications in respiratory metabolism were collectively indicative of a respiratory alkalosis. The relative increase in pulmonary minute vol. and CO2 elimination became progressively greater with exposure time, an elevation of the R.Q., and a shifting of the urinary pH toward alkalinity in those subjects displaying appreciable hyperventilation. No significant changes in the O2 consumption, or in oral temps. were found. The physiologic changes were reflected in behavior differences (somnolence, irritability, inattention, lack of volition, and fatigue) which, while not quantitatively assayed, were suggestive of psychologic deterioration. Resistance to exposure was best correlated with elevation of the R.Q. A lower altitude limit on prolonged flights in which O2 is not taken is suggested. The advisability of using supplementary O2 at altitudes as low as 8,000 ft., or pressurization at a lower physiological altitude is also indicated.

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