An assessment of central-peripheral ventilatory chemoreflex interaction in humans

Abstract

The independence of the central and peripheral chemoreflexes has been tested in humans. Acute metabolic acidosis generated by a prior bout of brief, hard exercise was used to stimulate primarily the peripheral chemoreceptors, and respiratory acidosis generated by inhaled CO 2 was used to stimulate both central and peripheral chemoreceptors. Seven healthy young men were studied. Ventilation and arterial pH, P CO2 and P O2 were recorded. Peripheral chemoreflex sensitivity to hypoxia during acute metabolic acidosis was repeatedly determined by measuring ventilation in euoxia (PET O2 = 100 Torr) and hypoxia (PET O2 = 50 Torr) as the subject recovered from exercise-induced acidosis. Peripheral chemoreflex sensitivity to hypoxia during CO 2 inhalation was repeatedly determined by measuring ventilation in euoxia and hypoxia at two levels of hypercapnia (PET CO2 = 45 Torr and PET CO2 = 50 Torr). The ventilatory sensitivity to hypoxia at matched arterial pH values was not significantly different between conditions of high (CO 2 inhalation) and low (metabolic acidosis) central chemoreceptor activity. We therefore conclude that interaction between central and peripheral chemoreflexes was non-significant in all subjects.