Effects of smoking history on the benefits of pulmonary rehabilitation in patients with COPD

Abstract

Introduction: Despite the recognized benefits of pulmonary rehabilitation (PR) for patients with COPD, the effects of smoking history on the results of a PR program are not well known. Aim: To investigate if smoking history is related to the improvement achieved with a 12-week PR program in patients with COPD. Methods: 45 patients with COPD (26 men; 66±7 years), all ex-smokers or smokers, were classified in three groups according to their smoking history: light smokers (LS: 0.1-20 pack/years; n=8); moderate smokers (MS: 20.1-40 pack/years; n=14) and heavy smokers (HS: >40 pack/years; n=23). Patients were questioned about their smoking history and had their lung function assessed by spirometry, exercise capacity by the 6-minute walk test (6MWT), dyspnoea by the modified Medical Research Council scale (mMRC) and peripheral muscle strength by the 1RM test. The PR program comprised 12 weeks of high-intensity endurance and strength training. Results: HS had worse baseline 6MWT than LS, as well as worse 6MWT and mMRC than MS, however with no baseline differences in lung function between the groups. LS, MS and HS significantly improved the 6MWT, strength of the quadriceps femoris, biceps and triceps brachii. There were no significant differences in the magnitude of improvement between the groups, and no correlation was found between smoking history and magnitude of improvement. Conclusion: Patients with COPD with a smoking history of >40 pack/years have worse exercise capacity and more dyspnea symptoms compared to patients with a less heavy smoking history; however, all groups demonstrated similar benefits after PR in terms of improving exercise capacity and peripheral muscle strength.