Pulmonary diffusing capacity for co in dogs by the single breath method

Abstract

In order to determine the diffusing properties of the lung an attempt was made to take into account the disturbing effects of functional inhomogeneities upon determinations of Dco. Dco was measured by the single breath method in 21 anaesthetised dogs weighing on the average 25 kg. The Dco values decreased considerably as the time of apnoea was increased from 3–30 sec, indicating presence of unequal distribution of Dco in the lungs. For an apnoea time of 10 sec a mean Dco value of 25 ml/min. mm Hg in hypoxia (Flo 2 = 0.12) was obtained, on the assumption of a homogeneous lung. When the effects of unequal distribution of inspired volume and of Dco were taken into account, the value increased to 52 ml/min. mm Hg. Using data from CO uptake of human red blood cells, the membrane component of Dco was estimated from measurement of Dco at varying inspired O 2 concentrations to be 80 ml/min. mm Hg and the pulmonary capillary volume, to 100 ml.