Inspiratory Muscle Training in COPD

The benefits of inspiratory muscle training (IMT) for patients with COPD are documented in the literature, but its isolated effect or association with other interventions, the best training methods, and what type of patient benefits the most are not clear. We sought to assess the effects of IMT on respiratory muscle strength, pulmonary function, dyspnea, functional capacity, and quality of life for subjects with COPD, considering IMT isolated or association with other interventions, presence of inspiratory muscle weakness, training load, and intervention time.

We searched the MEDLINE, EMBASE, PEDro, Cochrane CENTRAL, and LILACS databases in June 2018. We also performed a manual search of references in the studies found in the database search and included in this analysis. We included randomized controlled trials that investigated the above-mentioned outcomes and assessed IMT, either isolated or associated with other interventions, in comparison with a control group, placebo, or other interventions, in subjects with COPD. We used the GRADE approach to evaluate the quality of the evidence.

Of 1,230 search results, 48 were included (N = 1,996 subjects). Isolated IMT increased P_Imax (10.64 cm H₂O, 95% CI 7.61-13.66), distance walked in 6-min-walk test (34.28 m; 95% CI 29.43-39.14), and FEV₁ (0.08, 95% CI 0.02-0.13). However, there was no improvement in dyspnea and quality of life. The presence of inspiratory muscle weakness did not change the results; higher loads (60-80% of P_Imax) promoted a greater improvement in these outcomes, and a shorter intervention time (4 weeks) improved P_Imax, but longer intervention times (6-8 weeks) are required to improve functional capacity. IMT associated with other interventions only showed an increase in P_Imax (8.44 cm H₂O; 95% CI 4.98-11.91), and the presence of inspiratory muscle weakness did not change this result.

Isolated IMT improved inspiratory muscle strength, functional capacity, and pulmonary function, without changing dyspnea and quality of life. Associated IMT only increased inspiratory muscle strength. These results indicate that isolated IMT can be considered as an adjuvant intervention in patients with COPD.