Effects of hemodialysis and anemia on pulmonary diffusing capacity, membrane diffusing capacity and capillary blood volume in uremic patients.

The study aimed at investigating pulmonary function in uremic patients, emphasizing the lung diffusing capacity for CO (DLCO) and its membrane and pulmonary capillary blood volume (Vc) components. The study sample comprised 25 uremic patients without clinical/radiological evidence of lung disease. They were enrolled in a chronic hemodialysis (HD) program and had anemia requiring transfusions. The subjects were tested for their lung function before and after both a first HD and a HD with blood transfusion (BT) that followed a few days later. After HD-induced removal of body fluid, and increase in pre-HD reduced forced vital capacity, alveolar volume and mid-expiratory flow rate (FEF25-75%) was observed. HD-induced DLCO decrease (p less than 0.005) was observed and was related to decreased Vc. The second HD with BT increased DLCO, due to partially normalized Hb. On average, a 7.2% DLCO increase corresponded to each 10-g/l Hb rise. In conclusion, (1) the beneficial effect of HD in uremic patients reverts the small-airway obstruction; (2) the lower values of DLCO in these patients are due to reduced Hb and HD causes further DLCO reduction via decrease of Vc, and (3) HD with BT still increases DLCO because improvement of Hb predominates.