RESUMO
Background. Objective assessment of severity in patients with chronic obstructive pulmonary disease (COPD) is mainly limited to pulmonary function testing performed at rest. But, accurate assessment of exercise capacity in patients with COPD may be possible with cardiopulmonary exercise testing (CPET). Methods. Forty-three patients with stable COPD were included and were divided into three groups based upon the spirometry data as per the Global Initiative for Obstructive Lung Disease (GOLD) guidelines as follows: Group A: mild COPD, Group B: moderately severe COPD and Group C: severe COPD. Symptom-limited CPET was performed using treadmill on incremental continuous ramp protocol in all of them. Results. Five patients (11.6%) had mild COPD; 16 (37.2%) had moderately severe COPD and the remaining 22 (51.6%) patients had severe COPD. Anaerobic threshold was attained in all the 43 patients. The dominant symptom at peak exercise were dyspnoea (n=19) and both dyspnoea and leg fatigue (n=7). The other causes of exercise limitation included dyspnoea with significant oxygen desaturation (n=6); and dyspnoea with severe oxygen desaturation (n=2). Six patients complained only of leg fatigue at peak exercise. A significant correlation between forced expiratory volume in the first second (FEV1) percent predicted and the predicted maximum oxygen uptake (VO2 max % predicted) was observed in all the three groups (r=0.39, p=0.011) but with marked variability of peak VO2 for a given degree of airflow obstruction. Twenty-three (53.5%) patients with low anaerobic threshold (<30%) were identified as potential group likely to benefit from exercise training for pulmonary rehabilitation. Conclusions. Cardiopulmonary exercise testing is useful to determine the causes of exercise limitation and to assess the maximal exercise capacity of patients with COPD.