The influence of obesity on pulmonary rehabilitation outcomes in patients with COPD

Abstract

Although obesity is increasing in prevalence, relatively little attention has been given to its impact on outcomes in patients with chronic obstructive pulmonary disease (COPD) completing pulmonary rehabilitation. We conducted a retrospective chart review of 114 patients with COPD who completed outpatient pulmonary rehabilitation at our center. Body habitus categories were determined based on body mass index (BMI). Underweight patients (BMI < 21 kg/m²) were excluded from the analysis. Normal weight and overweight patients were classified as non-obese. Obese patients (BMI >30 kg/m²) were compared with non-obese patients in the following areas: forced expiratory volume in 1 s (FEV₁) percent predicted, the 6-min walk distance (6MWD), health status, the number of unsupported arm lifts per minute, and functional performance. Health status was determined using the Self-Reported Chronic Respiratory Questionnaire (CRQ-SR), which has dimensions of dyspnea, fatigue, emotion, and mastery. Functional performance was determined using the Pulmonary Functional Status Scale Daily Activities subscore. Compared with non-obese patients, obese patients had a higher FEV₁ percent-predicted (44 ± 15% vs 52 ± 16%; P = 0.01), yet had lower 6MWD (269 ± 11 vs 203 ± 13; P = 0.0002), lower functional status, and greater fatigue at initial evaluation. However, the two groups had similar walk-work, which adjusts for differences in weight. Despite the baseline differences, both groups improved similarly following pulmonary rehabilitation (change in 6MWD was 52 ± 7 m in the non-obese patients versus 47 ± 9 in the obese patients; P = 0.65). Our study suggests that obese COPD patients are referred to pulmonary rehabilitation at an earlier spirometric stage of their disease, but have a poorer exercise performance, a greater degree of functional impairment and greater fatigue levels. This is probably, largely because of the effect of an increased weight burden. However, obesity did not seem to adversely affect the pulmonary rehabilitation outcomes.