Effects of inhalation of 100 per cent oxygen on the pulmonary blood volume in patients with organic heart disease

The effect of breathing 100 per cent oxygen on the pulmonary blood volume, pulmonary arterial pressure, left atrial pressure, and pulmonary vascular distending pressure was studied during cardiac catheterization in eight patients with organic heart disease. In half of the patients, a significant decrease in pulmonary blood volume was observed. This decline in pulmonary blood volume in the face of a decrease or no change in the pulmonary distending pressure is interpreted as evidence for a passive mechanism of action for 100 per cent oxygen. The effects of hyperoxia are compared to those of acetylcholine, which works by actively dilating the pulmonary vascular bed.