Effect of body temperature and hypoxia on the ventilatory CO 2 response in man

Abstract

The ventilatory CO 2-response and the effect of hypoxia on this relationship were studied m four healthy subjects at normal and at elevated (+ 1.5 °C) body temperature. The experiments were carried out in a climatic chamber. Expired minute ventilation, rectal temperature and arterial tensions of oxygen and carbon dioxide were measured. Breathing air all subjects hyperventilated at elevated body temperature. The ventilatory CO 2-response line in high oxygen was displaced to the left in all subjects, and in three subjects a potentiated ventilatory response to hypoxia in addition to CO 2 was found during hyperthermia. In three subjects a significant increase in slope of the e t line in a Hey-plot was found in hyperthermia. The results seem to be evidence of a specific action of hyperthermia in the respiratory regulation apart from the drives related to discomfort of the experimental situation. Whether the effect of hyperthermia in our hyperoxic experiments is a direct temperature effect on central respiratory neurones or an indirect one is unknown. The potentiation of the hypoxic stimulus during hyperthermia, however, might be mediated through the arterial chemoreceptors.