Effects of combined inspiratory muscle training and positive expiratory pressure therapy on pulmonary function, respiratory muscle strength, exercise capacity and dyspnea in stable group E COPD patients

Abstract Background Inspiratory muscle training combined with positive expiratory pressure (IMT/PEP) may improve outcomes in chronic obstructive pulmonary disease (COPD), but evidence in exacerbation‑prone (Group E) disease is limited. We evaluated the effects of IMT/PEP on pulmonary function, respiratory muscle strength, exercise capacity, and dyspnea in stable Group E COPD. Methods In this prospective randomized controlled trial, 62 stable Group E COPD patients were enrolled from June 2023 to September 2024 and randomized to IMT/PEP plus standard care or standard care alone. Pulmonary function tests, maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), six‑minute walk test (6MWT), oxygen saturation (SpO₂), and dyspnea scales (mMRC, CAT, MBS, VAS) were assessed at baseline, 1 month, and 3 months. Results At 1 month, compared with controls, the IMT/PEP group showed greater improvements in FEV₁/FVC, FEV₁, and FVC (all p < 0.001), a smaller increase in RV/TLC (p < 0.001), and higher SpO₂ and 6MWT distance (both p < 0.001); MIP also increased (p = 0.01). By 3 months, FEV₁/FVC (p = 0.02), FEV₁ (L and % predicted; p = 0.01 and p = 0.04), FVC (L and % predicted; p = 0.04), and MEF25–75% (p = 0.01) were higher and RV/TLC was lower (p = 0.01) in the IMT/PEP group; MIP increased in absolute and % predicted terms (p = 0.001 and p = 0.002), whereas MEP did not change significantly. SpO₂ and 6MWT increased (both p < 0.001), and MBS, mMRC, VAS, and CAT scores decreased (p < 0.001 for each). In multivariable analyses, greater ΔMIP was associated with lower baseline MIP (p < 0.001), lower baseline 6MWT (p = 0.033), lower baseline VAS (p = 0.016), and higher baseline MEP (p = 0.001). Conclusions In stable Group E COPD, adjunct IMT/PEP improved pulmonary function (FEV₁, FVC, FEV₁/FVC, MEF25–75%, RV/TLC), inspiratory muscle strength, oxygenation, and exercise capacity and reduced dyspnea over 3 months; benefits were most pronounced in patients with lower baseline inspiratory strength and limited functional capacity. Trial registration Registered at ClinicalTrials.gov (NCT07001462) on 3 June 2025. Retrospectively registered.