Oxygen-related intrapulmonary shunting in obstructive pulmonary disease.

A simple and previously validated double-indicator technique was used to quantitate shunt in patients with obstructive pulmonary disease at rest, during exercise, and during breathing of 100 percent oxygen. The method avoids several inherent difficulties encountered in previous double-indicator techniques and is independent of the fraction of oxygen in the inspired gas. Sixteen resting patients with mild obstructive pulmonary disease were found to have intrapulmonary shunting less than or equal to 0.7 percent of the cardiac output (mean, 0-3 +/- 0.2 percent [SD]). During submaximal exercise, shunting was also low (mean, 0.3 +/- 0.1 percent of cardiac output). After breathing pure oxygen for 30 minutes, 11 patients had similar results; however, in four patients, breathing 100 percent oxygen caused an increase intrapulmonary shunting to 1 to 6 percent of the cardiac output. It is concluded that some patients with obstructive pulmonary disease develop intrapulmonary shunting in response to breathing oxygen.