Another Possible Mechanism of Hypoxemia

P ulmonary arteriovenous vascular channels larger than typical pulmonary capillaries have been shown to exist in patients with hepatic cirrhosis.’ These enlarged vessels have been demonstrated by quantitative radionuclide techniques.2 It has been difficult or impossible to otherwise demonstrate them during life or in post-mortem studies.3 These apparently dilated vessels are believed to function as shunts and thereby contribute to the heretofore enigmatic hypoxemia of cirrhosis. The finding of such a mechanism of hypoxemia in cirrhosis patients raises the question of whether such shunts develop in other disease states.4 The hypoxemia ofcirrhosis is often characterized by exercise-aggravation. Exercise-aggravation ofhypoxemia is also typical ofpatients with chronic obstructive pulmonary disease (COPD).6 We studied patients with COPD for the presence of such dilated gas-exchanging vessels.