Pulmonary clearance of inert gases with particular reference to ethyl ether

¹ Department of Internal Medicine, University of Buffalo School of Medicine, Buffalo, New York

Theoretical approaches to inert gas exchange in the lungs have indicated that ventilation, perfusion, and the solubility of the gas (blood-air distribution at equilibrium) are the determining factors in gas elimination by expired air. A mathematical expression is derived to predict clearance of inert gases based on these three factors: Qcl.x = V a.o₂Q/(Va.o₂ + SxQ). The derivation of this equation is supported by empirical data using ethyl ether in dogs to indicate that the dead space for ether and oxygen are substantially the same under the conditions of this study, and that there is complete equilibration between the ether concentration in arterial blood and end-tidal, "alveolar," air. The solubility of diethyl ether in blood is high enough that, according to this equation, its pulmonary clearance should be governed by ventilation and substantially independent of cardiac output within ordinary ranges of these two factors. As such, its use as a measure of effective alveolar ventilation in a variety of laboratory and clinical situations is suggested.