Pulmonary Gas Exchange Abnormalities in Mild COPD: Implications for Dyspnea and Exercise Intolerance (original) (raw)

Several studies in mild COPD have shown higher than normal ventilatory equivalent for carbon dioxide (VE/VCO2) during exercise. Our objective was to examine pulmonary gas exchange abnormalities and the mechanisms of high VE/VCO2 in mild COPD and its impact on dyspnea and exercise intolerance. Twenty-two subjects (11 GOLD grade-1B COPD patients, 11 age-matched healthy controls) undertook physiological testing and a symptom-limited incremental cycle exercise test with arterial blood gas collection. Patients (post-bronchodilator FEV1: 94±10 %predicted; mean±SD) had evidence of peripheral airway dysfunction and reduced peak oxygen uptake compared to controls (80±18 versus 113±24 %predicted; p<0.05). Arterial blood gases were within the normal range and effective alveolar ventilation was not significantly different from controls throughout exercise. The alveolar-arterial O2 gradient was elevated at rest and throughout exercise in COPD (p<0.05). VE/VCO2, dead space-to-tidal volume r...