Respiratory muscle and cardiopulmonary function during exercise in very severe COPD

Chronic obstructive pulmonary disease (COPD) is thought to limit exercise capacity through a decreased ventilatory reserve, with cardiovascular factors playing a minimal role. We assessed respiratory muscle (RM) and cardiopulmonary function during exercise in very severe COPD (FEV1 0.79 +/- 0.17 L). We determined minute ventilation (VE), oxygen consumption (VO2), carbon dioxide production (VCO2), heart rate (HR), respiratory rate (RR), and O2 pulse with a metabolic cart. RM function was assessed from esophageal and gastric pressures. Dyspnea was assessed with a visual analog scale (VAS). Exercise capacity (peak VO2 = 36 +/- 31%), ventilatory reserve (VE/maximum voluntary ventilation [MW] = 89 +/- 31%), HR = 76 +/- 15%, and O2 pulse (O2Pmax = 45 +/- 15%) were abnormal. Peak VO2 correlated with O2Pmax(r = 0.82), the change in end-inspiratory pleural pressure (deltaPpli) (r = -0.74), maximal transdiaphragmatic pressure (Pdimax) (r = 0.68), and VEmax (r = 0.58). There were similar correlations with exercise e...