INTERACTION OF CO2 AND HYPOXIC STIMULI ON VENTILATION AT HIGH ALTITUDE

Abstract

The interaction of O2 and CO2 on the control of ventilation has been studied by a rebreathing technique in three healthy young male subjects, first under sea level conditions, then following 2 weeks' acclimatization to an altitude of 14,250 ft. The following results were observed: (a) at high altitude the family of response curves were shifted to lower values of alveolar CO2, and all response curves had a steeper gradient δVE/δPAACOACO2 than at sea level; (b) hypoxia potentiated the response to hypercapneic stimulus to about the same extent at sea level and at high altitude; (c) the ventilatory response to hypoxia was identical at sea level and at high altitude when PAACOACO2 was held at the normal air breathing value for the two conditions; but (d) potentiation of ventilatory response to hypoxia at high altitude occurred with smaller increments of CO2 than at sea level. This was interpreted to mean that H+ is an important factor in the mechanism of hypercapneic potentiation of hypoxic stimulus. © 1963 The Physiological Society