The Influence of Body Composition on Pulmonary Rehabilitation Outcomes in Chronic Obstructive Pulmonary Disease Patients

Abstract

Alterations in body composition are commonly present in chronic obstructive pulmonary disease (COPD). The hypothesis of this study is that COPD patients would achieve clinical benefits after pulmonary rehabilitation (PR) independent of muscle mass depletion or body weight. We conducted a retrospective cohort study using single-frequency bioelectrical impedance analysis (BIA) for assessment of fat-free mass (FFM) depletion (muscle depletion). Patients were stratified into three categories based on (1) obesity BMI≥30kg/m2, (2) non-obesity BMI<30kg/m2, and (3) combined cachexia (BMI<21kg/m2 and FFM index<16kg/m2) and muscle atrophy (BMI≥21kg/m2 and FFMI<16kg/m2). PR outcomes were defined as the improvement in exercise capacity (maximal exercise capacity, 6-min walk, constant workload cycle exercise duration) and quality of life determined by Chronic Respiratory Questionnaire after PR. We studied 72 patients with available FFM measured by BIA. Patients were predominantly elderly man (N=71; 98%), with a mean age of 72years with COPD GOLD stage I-IV. The groups were balanced in terms of age, comorbidities, baseline FEV1, exercise capacity, and quality of life. The absolute changes in patients with muscle depletion or obesity compared to those without muscle depletion or obesity were not statistically different as was the percentage of patients reaching the minimal clinically important difference (MCID) after PR. A comprehensive PR program in COPD patients improved exercise tolerance and quality of life independent of muscle mass depletion or obesity. Similarly, muscle depletion or obesity had no effect on the percentage of patients achieving the MCID for measures of quality of life and exercise tolerance after PR.