Effect of Unilateral Nitrogen Breathing Upon Pulmonary Blood Flow

Abstract

In 11 dogs under chloralose-morphine anesthesia the chest was opened and each lung ventilated by a separate Starling pump. Blood flow through each lung was detd. by the Fick principle both during bilateral O2 breathing and during unilateral N2 breathing, the other lung receiving O2- Vascular resistance of each lung was calculated from mean pulmonary artery pressure and blood flow. In all but 3 animals there occurred a reduction of 16-68% of the original fraction of total flow to the nitrogen lung. The max. effect was present after 25 min., and was promptly reversible on return to bilateral O2. Resistance in the nitrogen lung increased by factors of 1.3-4.5; in the oxygen lung it remained essentially unchanged. 02 saturation of the blood draining the nitrogen lung ranged from 10-50% (equivalent to 02 tensions of 8-25 mm. Hg) of the mixed arterial blood from 62-96%.