Improvement in pulmonary function with diuretic therapy in the hypervolemic and polycythemic patient with chronic...

Central hemodynamics and gas exchange were studied in six patients with chronic obstructive pulmonary disease (mean age, 60 years). Patients were selected for the study if the volume of blood was 1 L larger than the predicted normal value, if there was no history of infection, and if no drug assumed to influence pulmonary circulation had been given during the last four weeks. Measurements were first performed in the hypervolemic state. This was followed by a venesection of 0.5 L, and the measurements were repeated 15 minutes later (immediate effects of dehydration). After two weeks to two months of intensive diuretic therapy, new measurements were performed (long-term effects of dehydration). With hypervolemia, there was pulmonary hypertension, increased pulmonary vascular resistance, and normal cardiac output. The arterial oxygen tension (PaO2) was markedly reduced. The arterial carbon dioxide tension (PaCO2) was increased in two patients, and dead-space ventilation (VD/VT) increased in all. The sole immediate effect of venesection was a small increase in heart rate and a reduction in PaCO2. The long-term effects were a maintained low blood volume (on the average, 0.7 L less than before bloodletting) and lowered hematocrit reading (8 percent less than before bloodletting), a reduced and in some patients normalized pulmonary arterial pressure, a reduced pulmonary vascular resistance, and an unchanged cardiac output. The PaO2 improved, while PaCO2 did not change; neither did VD/VT. The changes correlated partly with the diminution in blood volume and partly with the reduction in hematocrit reading.