Assessing the Impact of Pulmonary Rehabilitation on Functional Status in Chronic Obstructive Pulmonary Disease

Abstract

Rationale - The optimal way of assessing the impact of pulmonary rehabilitation on functional status in chronic obstructive pulmonary disease (COPD) is currently unknown. The minimal clinically important difference for the constant workrate cycling exercise also needs to be investigated to facilitate its interpretation. Objective – Evaluate the changes in the 6-minute walking test and in the constant workrate cycle endurance test immediately following and 1-year after pulmonary rehabilitation, along with the importance of these changes in term of health status in patients with COPD. Methods - Patients with COPD (age: 65  8 years, mean  SD; FEV1: 45  15 % predicted) were recruited from a multicenter prospective cohort study and were evaluated at baseline, immediately after a pulmonary rehabilitation program (n=157) and at 1 year (n=106). The 6-min walking test and the cycle endurance test were performed at each evaluation. Health status was evaluated with the St. Georges Respiratory Questionnaire. Measurements and Main Results - Following pulmonary rehabilitation, cycle endurance time increased (198  352s, p<0.0001) and stayed over baseline values at 1 year (p<0.0001). The 6-minute walking distance also showed improvements following rehabilitation (25  52m, p<0.0001) but returned to baseline values at the 1 year follow-up. Changes in cycle endurance time were more closely associated with changes in health status than those of the 6-min walking test. A 100-200s improvement in the cycle endurance time was associated with clinically meaningful changes in the St. Georges Respiratory Questionnaire scores. conclusions - The cycle endurance test was more responsive that the 6-min walking test to detect improvement in exercise tolerance following pulmonary rehabilitation and was also better correlated with improvements in health status. An improvement in the cycle endurance time ranging from 100-200s appeared to be clinically meaningful.