Comparison of cardiopulmonary exercise testing variables in COPD patients with and without coronary artery disease

Background: Coronary artery disease (CAD) is a common concomitant condition and an important cause of morbidity and mortality in patients with chronic obstructive pulmonary disease (COPD). Since COPD and CAD can both independently cause reduced exercise capacity, it is reasonable to hypothesize that the combination of these diseases may compound the abnormalities observed during cardiopulmonary exercise testing (CPET). However, little is known about the impact of CAD on the CPET response in COPD patients. The aim of this study is to compare exercise capacity and gas exchange variables in COPD patients with and without CAD. Methods: Fifty-four COPD subjects without CAD (COPDnoCAD) were matched to 54 COPD subjects diagnosed with CAD (COPD/CAD) according to age, gender, body mass index and severity of COPD. All subjects underwent resting pulmonary function and symptom-limited CPET. Results: Comparing COPDnoCAD patients with COPD/CAD patients revealed that exercise capacity, as measured by % peak oxygen consumption (42±16% vs 53±19%, p=0.002) and % peak wattage (23±13% vs 32±16%, p=0.001), was significantly lower in COPD/CAD. Ventilatory response, as measured by VE/VCO₂ nadir (36±9 vs 32±5, p=0.001), was significantly higher in COPD/CAD, with % peak VO₂ and VE/VCO₂ nadir correlating to % FEV₁ and inversely correlating with %DLCO. Conclusion: COPD patients with CAD have significantly impaired CPET responses with lower exercise capacity and impaired gas exchange compared to COPD patients without CAD. These findings may affect the clinical interpretation of CPET data in COPD patients who have concomitant CAD.