Carbon dioxide and pulmonary ventilation in muscular exercise

¹ Department of Physiology, State University of New York Downstate Medical Center, Brooklyn, New York

The effect of endogenous CO₂ from exercising muscles and exogenous CO₂ from CO₂ inhalation was investigated in six pairs of cross-circulated dogs. The exercising hindlimbs of one dog (neural) were perfused exclusively from a second dog (humoral). The ventilatory response of the neural dog during exercise followed the predicted isometabolic hyperbola toward hyperventilation, whereas the ventilation of the humoral dog followed closely the relationship which existed between V and Pa_COCO2 during CO₂ inhalation. When the neural dog was given CO₂ mixtures during steady state of induced exercise, its ventilation increased in a rectilinear function of the Pa_COCO2. The V, Pa_COCO2 line intersects the isometabolic curve for the exercise level at a Pa_COCO2 close to the resting Pa_COCO2. A metabolic acidosis developed in the humoral dog, although the blood flow to the perfused hindlimbs appeared to be adequate during muscular exercise.

Submitted on February 19, 1964