Objective: Pulmonary hypertension (PH) is common in patients with chronic obstructive pulmonary disease (COPD). Mean pulmonary artery pressure (mPAP) is often only slightly elevated at rest but is increased by exercise. The purpose of this study was to determine whether abnormal pulmonary artery pressure impairs exercise capacity in patients with COPD.
Patients and methods: 42 patients with moderate-to-very-severe COPD (28 men, 14 women) underwent symptom-limited incremental cardiopulmonary exercise testing and also right-heart catheterization at rest. Abnormal pulmonary artery pressure was defined as mPAP>20 mmHg at rest.
Results: Resting mPAP was elevated in 32 patients (PH, mPAP=26.8+/-5.9 mmHg) and normal in 10 non-hypertensive (NPH) patients (NPH, mPAP=16.8+/-2 mmHg). There were no significant differences in lung function between the PH and NPH groups. Maximum oxygen uptake during exercise (VO2max) was significantly lower in PH (785+/-244 ml/min) than in NPH (1052+/-207 ml/min, P=0.004). Dead-space ventilation (Vd/Vt) was greater in PH (P=0.05) with higher VE/VCO2 (ratio of minute ventilation to carbon dioxide output=47.3+/-10 vs 38.6+/-3.5, P=0.025) and significantly higher arterial-end-tidal pCO2 difference [p(a-ET)CO2]. Pulmonary vascular resistance measured at rest correlated significantly with VO2max, VE/VCO2 and p(a-ET)CO2.
Conclusions: In patients with COPD, abnormal pulmonary artery pressure impairs gas exchange, decreases maximum oxygen uptake during exercise and impairs exercise capacity.