Distribution of Ventilation and Perfusion in the Lobes of the Dog's Lung in the Supine and Erect Position

Abstract

The 1st part of this study consists of simultaneously sampling expired air from two or more lobes. From the gas analyses the exchange ratio and the approximate ventilation/ perfusion ratio of each lobe can be computed. The ratio of the upper lobes is nearly always greater than that of the lower lobes in the supine as well as the erect position. The 2d study is an attempt to estimate the relative ventilation of the lobes by counting the radioactivity of individual lobes after they had been exposed for 2 hours to an aerosol consisting of daughter products of radon gas deposited on dust particles of approximately 0.l[mu] size. In the supine position less activity per unit lung is found in the lower lobes than in the upper lobe. In the erect position this situation is reversed. On the assumption that the radio-active count is proportional to the ventilation one can substitute such ventilation figures into the ventilation/perfusion ratios determined in the 1st study and thus arrive at approximate values of the relative blood flow to each lobe. This analysis shows that the perfusion per unit lung is nearly the same for both lobes in the supine position. In the erect position the perfusion per unit lung of the lower lobe is greater than that for the upper lobe and suggests that gravity produces an uneven distribution of blood flow favoring the pendant portions of the lung.