ASSESSING THE IMPACT OF PULMONARY REHABILITATION ON FUNCTIONAL STATUS IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE
Laviolette L, Bourbeau J, Bernard S, Lacasse Y, Pepin V, Breton M-J, Baltzan M, Rouleau M, Maltais F
Thorax. Published Online First September 27, 2007; doi: 10.1136/thx.2006.076844.
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 work rate cycling exercise also needs to be investigated to facilitate its interpretation.
Objective
To evaluate the changes in the 6-minute walk test and in the constant work rate cycle endurance test immediately following and 1 year after pulmonary rehabilitation, along with the importance of these changes in terms 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 examined at baseline, immediately after (n = 157), and at 1 year after (n = 106) a pulmonary rehabilitation program. The 6-minute walk test and the cycle endurance test were performed at each evaluation. Health status was evaluated with the St George's Respiratory Questionnaire.
Measurements and Main Results
Following pulmonary rehabilitation, cycle endurance time increased (198 +/- 352 seconds, P < .0001) and stayed over baseline values at 1 year (P < .0001). The 6-minute-walk distance also showed improvements following rehabilitation (25 +/- 52 m, P < .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-minute-walk-test. A 100- to 200-second improvement in the cycle endurance time was associated with clinically meaningful changes in the St George's Respiratory Questionnaire scores.
Conclusions
The cycle endurance test was more responsive than the 6-minute walk 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 to 200 seconds appeared to be clinically meaningful.
Editor's Comment. Clinically meaningful changes in standard assessment tests are often somewhat arbitrarily defined. Objectively validated levels of significance help define the value of interventions and also provide indices that can be used to robustly define longitudinal trends. This study compares the de facto standard, the 6-minute-walking distance, with the perhaps more rigorous, cycle endurance time. Although both improve significantly with rehabilitation exercise training, the improvement in cycle endurance time is more durable and more clearly associated with improvements in disease-related quality of life, especially when remeasured 1 year after exercise training. The 6-minute-walking test needs to be viewed in this context as its simplicity is offset by its lack of sensitivity in identifying clinically relevant changes in patients with COPD undergoing rehabilitation.