Alveolar-capillary membrane dysfunction in chronic heart failure: pathophysiology and therapeutic implications

Chronic heart failure (CHF) disturbs the alveolar-capillary interface and i ncreases the resistance to gas transfer. Alveolar-capillary membrane conduc tance (D-M) and capillary blood volume (V-c) are subcomponents of the lung diffusion capacity. Elevation of the capillary pressure causes alveolar-cap illary membrane stress failure (i.e. increase in capillary permeability to water and ions, and disruption of local regulatory mechanisms for gas excha nge), leading to a decrease in D-M, an increase in V-c and subsequent impai rment of diffusion capacity. Renewed recent interest in abnormalities in lu ng diffusion in patients with CHF has brought about new pathophysiological insights. A significant contribution of the altered gas transfer to the pat hogenesis of exercise limitation and ventilatory abnormalities has been rep orted, and D-M has been identified as the best lung function predictor of o xygen uptake at peak exercise. This review examines the pathophysiological and clinical significance of assessing lung diffusion capacity in patients with CHF.