Effects of respiratory muscle training on clinical outcomes in patients with chronic obstructive pulmonary disease: A systematic review and meta-analysis

The effectiveness and clinical significance of respiratory muscle training for chronic obstructive pulmonary disease (COPD) patients remain controversial. Our aim is to systematically review and conduct a meta analysis on the impact of respiratory muscle training on the clinical outcomes of patients with COPD. We systematically searched electronic databases (PubMed, Web of Science, Cochrane Library, and Embase) for randomized controlled trials evaluating the effects of respiratory muscle training on clinical outcomes in COPD patients. We utilized fixed or random effects models to assess the impact of respiratory muscle training on the 6 min walk test (6MWT), dyspnea, pulmonary function, respiratory muscle strength, and quality of life (QOL). Thirteen studies met the inclusion criteria for this review, involving 1178 COPD patients, of whom 588 completed respiratory muscle training. Meta analysis results indicated that respiratory muscle training significantly improved 6MWT (mean difference [MD]: 17.99; 95% confidence interval [CI]: 3.73, 32.26), dyspnea (standardized MD [SMD]: -0.81; 95% CI: -1.28, -0.34), forced expiratory volume in 1 s (FEV1; MD: 0.09; 95% CI: 0.02, 0.17), forced vital capacity (FVC; MD: 0.13; 95% CI: 0.03, 0.23), maximum inspiratory pressure (MD: 14.43; 95% CI: 8.71, 20.14), maximal expiratory pressure (MD: 15.06; 95% CI: 5.69, 24.43), and QOL (SMD: -0.77; 95% CI: -1.43, -0.11). However, no significant effect of respiratory muscle training on FEV1 /FVC was found (MD: 1.22; 95% CI: -1.61, 4.06). Respiratory muscle training is a positive intervention for improving exercise tolerance, pulmonary function, respiratory muscle strength, and QOL in COPD patients. Further high quality studies are needed to validate the findings of this review.