The transient respiratory effects in man of sudden changes in alveolar CO 2, in hypoxia and in high oxygen

Abstract

In three moderately hypercapnic men ( e~35 L/min) repeated exposure to sudden transient hypocapnia induced depression of e after 2–3 breaths (?arterial chemoreceptor response) in mild lypoxia (Pa O 2 ~63 torr) but only after 5 breaths ( ?intracranial chemoreceptor response) in hyperoxia Pa o 2 ~ 650 torr). Sudden relief of hypoxia (hypercapnia maintained) depressed e after 3–4 breaths ( ∼ 100 tests of each kind). Usually V t changed more and f changed less than with corresponding steady-state changes of e. Thus (1) human arterial chemoreceptors respond more quickly to change of CO 2 than of hypoxia, and (2) hypoxia is a prerequisite for the response of human arterial chemoreceptors to CO 2: hypoxic-hypercapnic interaction is largely peripheral.