THE RATE OF INTRAPULMONARY BLOOD GAS EXCHANGE IN LIVING ANIMALS*

Abstract

This article describes a new method which makes possible for the first time the measurement of the time required for the dissociation of CO2 from bicarbonate in the lung capillaries of living dogs. The dog is placed in an airtight body plethysmograph, which instantanteously detects the appearance of CO2 gas evolved in the lung capillaries after the injection of bicarbonate solution into the pulmonary artery through a cardiac catheter. The time required for evolution of CO2 to reach 50% of completion is about 0.4 seconds. The reference time for transit of blood from the tip of the catheter to the pulmonary vessels of gas exchange is measured by injecting a little ether dissolved in alcohol or in lipid emulsion, and detecting the appearance of ether in the alveoli by the rise in plethysmographic pressure. The dissociation of CO2 appears to reach completion during a single passage of blood through the lungs.