Vol. 2, Issue 2, Part A (2025)

Background: Pulmonary rehabilitation (PR) is a core component of chronic obstructive pulmonary disease (COPD) management, yet many patients with moderate-to-severe disease remain limited by dyspnea and reduced exercise capacity, especially when inspiratory muscle weakness is present. Inspiratory muscle training (IMT) may enhance the benefits of PR, but its incremental value in multi-center, real-world programs remains uncertain.

Methods: In this multi-center, parallel-group randomized controlled trial, 120 adults with moderate-to-severe COPD and documented inspiratory muscle weakness were allocated to guideline-based PR plus high-intensity, threshold-loaded IMT (PR+IMT; n=60) or PR alone with sham IMT load (n=60). All participants completed an 8-week outpatient PR program comprising supervised endurance and resistance training, breathing retraining and education, with follow-up to 6 months. The primary outcome was change in 6-minute walk distance (6MWD) at 8 weeks. Secondary outcomes included maximal inspiratory pressure (MIP), dyspnea (Borg scale), health-related quality of life (St George’s Respiratory Questionnaire, SGRQ), incremental shuttle walk test (ISWT), lung function and exacerbation frequency. Analyses followed the intention-to-treat principle using mixed-effects models with random intercepts for center.

Results: Baseline characteristics were similar between groups. At 8 weeks, both groups improved significantly in 6MWD, but gains were greater with PR+IMT (mean change 58 m vs 32 m). The adjusted between-group difference in 6MWD was 26 m (95% CI 9-43; p=0.003), exceeding accepted minimal clinically important differences. MIP increased more in PR+IMT than PR alone (between-group difference 12.9 cmH₂O; p<0.001), accompanied by larger reductions in exertional dyspnea (Borg −0.5 units; p=0.01) and SGRQ total score (−3.9 points; p=0.04). A higher proportion of PR+IMT participants met dual responder criteria for 6MWD and SGRQ (56.7% vs 38.3%; p=0.03). Over 6 months, mean exacerbations per patient were lower in the PR+IMT group (0.70 vs 1.03; p=0.04), although hospitalization differences did not reach statistical significance. Lung function changes were small and similar between groups.

Conclusions: In patients with moderate-to-severe COPD and inspiratory muscle weakness, integrating high-intensity IMT into standardized PR produces additional, clinically important improvements in exercise capacity, inspiratory muscle strength, dyspnea and health-related quality of life, and may reduce subsequent exacerbation burden. These findings support routine assessment of inspiratory muscle strength and incorporation of structured IMT as a targeted adjunct within contemporary PR programs.