THE DEMONSTRATION OF PULMONARY ARTERIOVENOUS SHUNTS IN NORMAL HUMAN SUBJECTS, AND THEIR INCREASE IN CERTAIN DISEASE STATES *

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Abstract
Continuous records of arterial oxygen saturation changes during performance of Valsalva''s maneuver show a consistent pattern of change in normal subjects and in patients with various forms of heart and lung disease (but without intracardiac shunts). These changes are thought to result from a redistribution of pulmonary blood flow between ventilated alveolar capillaries and unventilated shunt vessels. Their magnitude is related to the volume of shunt flow present at rest. Abnormally large shunt flows were demonstrated by this method in 6 patients, in all of whom there was an abnormal elevation of pulmonary artery pressure.