Rebreathing and steady state pulmonary D o2, in the dog and in inhomogeneous lung models

Abstract

To validate the rebreathing method for determination of pulmonary diffusing capacity for O 2, D o 2 , measurements were performed in the same dogs using both the rebreathing method and the conventional steady state method. In 10 anesthetized dogs (mean weight 22.5 kg) the following mean values were found: D o 2 by the rebreathing method, 0.84 mmol · min − · torr −; D o 2 by the steady state method (using ideal alveolar P o 2 ), 1.15 mniol · min − · torr −. Calculations on simple theoretical models of parallel and stratified inhomogeneity revealed that with most types of inhomogeneity both methods tended to underestimate true D o 2 . The effects of many patterns of inhomogeneity were shown to be such as to decrease the apparent rebreathing D o 2 value more than the apparent steady state Do, value.