Experimental Support for Retrograde Diffusion from Alveoli to Pulmonary Arteries

¹ Departments of Medicine and Surgery, and the Glorney-Raisbeck Cardiopulmonary Laboratory, New York Medical College, Flower and Fifth Avenue Hospital

To investigate the mechanism of the immediate appearance of inhaled hydrogen at an electrode wedged into a small pulmonary artery, dog experiments were done whereby the appearance time was determind in various parts of the pulmonary arterial tree before and after the blood flow was stopped. With the electrode in a large artery the appearance time was longer after the circulation stopped. With the electrode in a wedged position the time was immediate with normal and interrupted blood flow. When the electrode was in a small artery, free not wedged, the time was often shorter with a normal circulation and became even less when the blood flow was stopped.

The results indicate the alveolar gas diffuses to the pulmonary arteries retrograde to the blood flow. The diffusion may be in whole or in part intra- or extravascular.