INTRAVENOUSLY ADMINISTERED ATRIAL-NATRIURETIC-FACTOR IN PATIENTS WITHCOPD - EFFECTS ON VENTILATION-PERFUSION RELATIONSHIPS AND PULMONARY HEMODYNAMICS

The potent pulmonary vasodilating property of atrial natriuretic facto r (ANF) may alter gas exchange in patients with COPD. We examined the hemodynamic and gas exchange responses to intravenous infusion of ANF (0.01 and 0.03 ng/min/kg body weight) in eight stable patients with CO PD studied during spontaneous breathing, using the inert gas eliminati on technique. When compared with baseline, ANF infusion was associated with a dose-dependent decrease in pulmonary artery pressure (from 27. 3 +/- 2.5 to 23.9 +/- 1.8 and 20.2 +/- 1.7 mm Hg, respectively) and a dose-dependent increase in blood flow perfusing poorly ventilated and unventilated units (VA/Q <0.1: from 5.80 +/- 2.05 to 7.25 +/- 2.5 and 12.0 +/- 5.4 percent of total blood flow, respectively; p = 0.02). How ever, PaO2 remained unchanged (70.2 +/- 3.6, 68.1 +/- 3.8 65.4 +/- 3.5 mm Hg, respectively) because of a significant increase in minute vent ilation (VE) from 8.6 +/- 0.8 to 9.6 +/- 0.8 and 10.3 +/- 0.7 L/min (p < 0.002). Six additional COPD patients receiving intravenously admini stered ANF at the same dosages were studied during controlled mechanic al ventilation using right heart catheterization. In these patients, p ulmonary vasodilation was associated with a significant increase in ve nous admixture (from 12.7 +/- 2.4 to 14.41 +/- 2.9 and 17.5 +/- 3.5 pe rcent of total blood flow, respectively; p < 0.02), and a dose-depende nt reduction in arterial Pot (from 117 +/- 17 to 110 +/- 15 and 96.4 /- 8.8 mm Hg, respectively; p < 0.05). The present results show that A NF infusion is associated with alterations in the VA/Q relationship in patients with COPD. However, a decrease in arterial oxygenation may b e prevented by an increase in VE.