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Background: Pulmonary hypertension (PH) is a well-known complication of chronic obstructive pulmonary disease (COPD). It remains unclear whether exercise parameters can be used to discriminate between COPD patients with associated PH (COPD-PH) and COPD patients without associated PH (COPD-nonPH). Objective: To study whether the existence of pulmonary hypertension in COPD is related to characteristic findings in gas exchange and circulatory parameters during cardiopulmonary exercise testing (CPET). Methods: We retrospectively analyzed CPET data in 25 COPD patients in whom right heart catheterization had been performed. Differences were assessed between COPD-PH and COPD-nonPH patients in peak oxygen uptake (VO2 peak), ventilatory efficiency (VE/VCO2), oxygen pulse, maximal ventilation and pulse oximetry (SpO2). Results: PH was found in 10 of 25 patients (mPpa = 33 ± 7 mm Hg), in 15 patients mean pulmonary artery pressure (mPpa) was below 25 mm Hg (18 ± 3 mm Hg). CPET in COPD-PH was characterized by a higher VE/VCO2 at nadir, a higher VE/VCO2 slope, and a lower SpO2 at rest and during exercise, but values in both groups were overlapping considerably. In the whole group mPpa was associated with resting PaO2 (r = –0.70, p < 0.001), VE/VCO2 nadir (r = 0.43, p < 0.05), and inversely related to SpO2 at rest and during exercise (r = –0.58 and r = –0.64, p < 0.01, respectively). Conclusion: Although CPET characteristics showed a large overlap in both groups, the existence of PH in COPD is associated with a significantly reduced ventilatory efficiency during CPET. However, a low SpO2 at rest and a further decrease during exercise similarly suggest the presence of PH in COPD. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]