Ninety-three patients with severe chronic obstructive pulmonary disease (COPD) of the bronchitic (n = 74) or emphysematous type (n = 19), who all had arterial hypoxemia, underwent 2 right cardiac catheterizations in a clinical steady state, with a delay of 5 yr or more between the first and the last catheterization. No patients received long-term O2 therapy or pulmonary vasodilator drugs. Patients were divided into 2 groups according to the initial level of mean pulmonary artery pressure (Pap). Group 1 included 61 patients without initial pulmonary arterial hypertension (PAH), Pap being less than 20 mmHg; the average delay between the 2 catheterizations was 93.4 +/- 26.8 months. Group 2 included 32 patients with initial PAH (Pap greater than or equal to 20 mmHg), and the average delay was 85.0 +/- 26.0 months. The changes in Pap were small. They ranged from 15.5 +/- 2.4 to 19.6 +/- 7.0 mmHg in Group 1 (p less than 0.001) and from 25.8 +/- 5.6 to 27.8 +/- 9.5 mmHg in Group 2 (NS). The average increase in Pap was 0.65 mmHg/yr in Group 1 and 0.39 mmHg/yr in Group 2 (no statistical difference between the 2 groups). The other hemodynamic parameters (pulmonary capillary wedge pressure, right ventricle filling pressure, cardiac output) did not change. Hemodynamic "worsening," which was defined by an increase in Pap by greater than or equal to 5 mm Hg, was observed in 29% of the patients (n = 27). In these patients, there was a marked worsening of hypoxemia, which was not observed in the remaining 66 patients.(ABSTRACT TRUNCATED AT 250 WORDS)