Cardiopulmonary exercise test characteristics in patients with chronic obstructive pulmonary disease and associated pulmonary hypertension

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 (VO(2) peak), ventilatory efficiency (VE/VCO(2)), oxygen pulse, maximal ventilation and pulse oximetry (S(p)O(2)).

Results: PH was found in 10 of 25 patients (mP(pa) = 33 +/- 7 mm Hg), in 15 patients mean pulmonary artery pressure (mP(pa)) was below 25 mm Hg (18 +/- 3 mm Hg). CPET in COPD-PH was characterized by a higher VE/VCO(2) at nadir, a higher VE/VCO(2) slope, and a lower S(p)O(2) at rest and during exercise, but values in both groups were overlapping considerably. In the whole group mP(pa) was associated with resting P(a)O(2) (r = -0.70, p < 0.001), VE/VCO(2) nadir (r = 0.43, p < 0.05), and inversely related to S(p)O(2) 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 S(p)O(2) at rest and a further decrease during exercise similarly suggest the presence of PH in COPD.