Pulmonary gas exchange in dogs ventilated with mixtures of oxygen with various inert gases.

To study the influence of physical properties of the respired gas on alveolar gas exchange, alveolar-arterial partial pressure differences for O2 and CO2 were measured in anesthetized dogs that were artificially ventilated with gas mixtures of O2 in N2, He, Ar or SF6. In both hyposia and normoxia alveolar-arterial PO2 differences had the tendency to increase slightly in the sequence of the respired inert gases SF6 less than Ar less than N2 less than He, while arterial-alveolar PCO2 differences remained practically unchanged. Pulmonary diffusing capacity for CO(DCO), determined by the single breath technique, revealed no significant differences between the four gas mixtures used. The possible mechanisms underlying these results are discussed in connection with the physical properties of the respired gas mixtures.