Lack of improvement of lung diffusing capacity following fluid withdrawal by ultrafiltration in chronic heart failure

OBJECTIVES We sought to investigate the possibility that lung diffusing capacity reduction observed in chronic heart failure is reversible in the short term. BACKGROUND Mechanical properties of the lung usually ameliorate with antifailure treatment including drugs, ultrafiltration and heart transplantation, whereas lung diffusion rarely improves. METHODS We studied the mechanical properties of the lung (pulmonary function tests with determination of alveolar volume, extravascular lung fluids and lung tissue), lung diffusion for carbon monoxide (DLco), including membrane diffusing capacity (Dm), pulmonary capillary blood volume (Vc) and pulmonary hemodynamics, in 28 patients with stable chronic heart failure, before a single session of extracorporeal ultrafiltration (3973 ± 2200 ml) and four days thereafter. Lung mechanics and diffusion were also evaluated in 18 normal subjects. RESULTS Vital capacity, forced expiratory volume (1 s) and maximal voluntary ventilation were lower in patients when compared with normal subjects, and increased after ultrafiltration from 2.1 ± 0.7 to 2.5 ± 0.7(l)*, 1.7 ± 0.5 to 2.0 ± 0.6(l)* and 67 ± 25 to 79 ± 26 (l/min)*, respectively (* p < 0.02 vs. pre-ultrafiltration). Post-ultrafiltration alveolar volume was augmented, while lung tissue, body weight ( 6 kg), chest X-ray extravascular lung water score and pulmonary vascular pressure were reduced. Heart dimensions (echocardiography) remained unchanged. DLco, Dm and Vc were 29.0 ± 5.0 ml/min/mm Hg, 47.0 ± 11.0 ml/min/mm Hg, 102 ± 20 ml in normal subjects and 17.1 ± 4.0#, 24.1 ± 6.5#, 113 ± 38 and 17.0 ± 5.0#, 24.8 ± 7.9#, 100 ± 39 in patients before and after ultrafiltration, respectively (# = p < 0.01 vs. controls). CONCLUSIONS In chronic heart failure, ultrafiltration improves volumes and mechanical properties of the lung by reducing lung fluids. Diffusion is unaffected by ultrafiltration, suggesting that, in chronic heart failure, the alveolar-capillary membrane abnormalities are fluid-independent.