We studied the effects of the inhaled anticholinergic agent oxitropium bromide (Ox) on pulmonary hemodynamics in eleven patients with chronic obstructive pulmonary disease. All the patients underwent right heart catheterization and seven of them underwent an incremental ergometer exercise test while in the supine position. Pulmonary hemodynamics and arterial blood gases were measured at rest and during maximal exercise, before and 30 minutes after inhalation of 2 puffs (200 micrograms) of Ox. Inhalation of Ox did not significantly change pulmonary hemodynamics at rest. The mean pulmonary arterial pressure and the mean pulmonary capillary wedge pressure during exercise decreased significantly (from 40.3 +/- 4.6 to 37.7 +/- 3.9 mmHg, and from 20.4 +/- 3.5 to 17.1 +/- 2.7 mmHg, respectively, mean +/- SE). However, neither cardiac output nor pulmonary vascular resistance changed with inhalation of the drug, at rest or during exercise. We therefore conclude that this commonly used dose of Ox does not directly affect the pulmonary vascular system. The small but significant decreases in pulmonary arterial pressure and pulmonary capillary wedge pressure with Ox may have been indirect effects, caused by bronchodilation.