Relationship Between Cardiac Output and Ventilation and Gas Transport, With Particular Reference to Anesthesia

Abstract

A theoretical approach is outlined for study of the interrelationship of ventilation rate and cardiac output on the O2and CO2tension of the mixed venous blood. These considerations indicate that the O2 tensions are largely detd. by the cardiac output rate and are nearly independent of the alveolar ventilation. The CO2 tensions and pH are primarily detd. by the alveolar ventilation rate and nearly independent of the blood flow. The O2 and CO2 tensions were obtained directly or indirectly for the alveolar air, arterial blood and mixed venous blood in dogs after admn. of Na pentobarbital and the recovery period of up to 6 hrs. While the ventilation is greatly altered in the beginning, the cardiac output remains essentially stable. The effects of the ventilatory depression and subsequent recovery upon the alveolar and arterial gas tensions, arterial saturation and exchange ratio are discussed.