Role of hypocapnia in the circulatory responses to acute hypoxia in man.

Publisher Website
Google Scholar
Abstract
The role of hypocapnia in the circulatory response to acute hypoxia was investigated in 18 healthy men. Cardiac output increased by 76%, heart rate increased by 25%, and arterial pressure did not change significantly in 9 subjects who breathed 8% O2 in N for 7-8 min. Addition to this inspired gas mixture of sufficient carbon dioxide to raise arterial pCO2 to its control value reduced the circulatory changes, but raised arterial O2 tension from an average of 37 to 52 mm Hg as a result of increased ventilation. Abolition of hypocapnia without change in arterial O2 tension, by reducing O2 concentration from 9 to 7% when CO2 was added to inspired gas, produced no change in the circulatory responses to hypoxia in 12 subjects. Thus, hypocapnia does not appear to be responsible for the increase in cardiac output, heart rate, and forearm blood flow which accompany acute arterial hypoxia.