Venous admixture in the pulmonary circulation of anesthetized dogs

Abstract

The venous admixture to the pulmonary circulation in the anesthetized dog was calculated from the O 2 . tension of the alveolar gas and arterial blood and the O 2 content of the arterial and mixed venous blood when breathing 43 or 99% oxygen-nitrogen mixtures. The average shunt flow varies from 1–10% and averages about 5% of the total flow. When positive pressure breathing is applied the shunt flow is reduced in every animal and averages 1.0%. Indirect evidence suggests that the major part of this shunt reduction with pressure breathing is due to the opening of lung areas which had spontaneously collapsed during the barbital anesthesia. Submitted on November 30, 1959