Transient effect of sudden mild hypoxia on respiration

Abstract

Recent studies of carotid body chemoreceptor activity in cats show that the activity of these organs increases markedly over a range of alveolar pO₂ considerably higher than the alveolar pO₂ of 50–60 mm Hg known to produce an increase in ventilation in the steady state. In an attempt to explain this discrepancy between chemoreceptor activity and ventilation, the transient ventilatory response to two breaths of a low O₂ mixture was observed and correlated with the alveolar pO₂ during this brief hypoxic stimulus. A transient increase in ventilation could be detected at an alveolar pO₂ of 93 mm Hg, that is, considerably higher than the highest pO₂ known to increase ventilation during the steady state. These findings are interpreted as evidence of an increased chemoreceptor drive when alveolar O₂ tension is lowered only slightly below that existing at sea level. Possible reasons for the difference between the steady state and transient responses are discussed. Submitted on June 6, 1960