Determinants of exercise capacity in obese and non-obese COPD patients.

BACKGROUND: The effects of obesity in combination with chronic obstructive pulmonary disease (COPD) on exercise capacity are receiving increased attention. But, a comprehensive analysis of factors associated with aerobic capacity in obese COPD patients has not been performed.

METHODS: Six-min walking test (6MWT) was performed in 251 COPD patients, and 159 of those also carried out an incremental cardiopulmonary exercise test (CPET) to evaluate exercise capacity. In all patients, anthropometrics, dyspnea and anxiety-depression scores, lung function, daily physical activity, co-morbidities and circulating inflammatory biomarkers were also assessed. Six-min walking distance (6MWD) and peak oxygen uptake (VO2 peak) during CPET were two primary outcome variables.

RESULTS: 57% of the patients showed body mass index (BMI) < 30 kg/m2 (COPDN) and the remaining 43% were obese with a BMI ≥ 30 kg/m2 (COPDO). In patients with COPDN, 6MWD showed independent negative associations with age, dyspnea score, sedentarism, depression scores and a positive relationship with arterial oxygenation; whereas in COPDO, 6MWD showed an inverse relationship with BMI. In COPDN, VO2 peak showed a negative association with age and positive relationships with both FEV1 and DLCO. However, in COPDO the dyspnea score was the strongest determinant of VO2 peak.

CONCLUSIONS: Obese and non-obese COPD patients show different determinants of aerobic capacity, including pulmonary and non-pulmonary factors that are also dependent on the type of exercise protocol. These results could be considered in the evaluation of obese patients with COPD.