Evaluating the Impact of Inspiratory Muscle Training on Respiratory Function and Exercise Capacity in Pulmonary Hypertension: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Highlights: What are the main findings? IMT significantly improves inspiratory and expiratory muscle strength and consistently reduces dyspnea and fatigue, with improvements in quality-of-life domains. IMT is safe and well tolerated, effects on spirometry are negligible, and improvements in exercise capacity (6-MWD) show positive trends but do not reach pooled statistical significance. What are the implications of the main findings? IMT is a low-burden, safe, and practical intervention that can be readily integrated into routine management to address key functional limitations associated with PH. IMT serves as an effective non-pharmacological adjunct to standard medical therapy, enhancing patient management without introducing additional systemic side effects or safety concerns. For physiotherapists and rehabilitation specialists, IMT provides an accessible and versatile modality suitable for both supervised clinical programs and home-based rehabilitation. IMT can be delivered using portable threshold devices, facilitating wide adoption across diverse care settings and improving patient adherence. (1) Background: Pulmonary hypertension (PH) is characterized by respiratory muscle weakness, limited exercise tolerance, and reduced quality of life, but inspiratory muscle training (IMT) has emerged as a potential non-pharmacological strategy to improve functional outcomes in this population. This systematic review and meta-analysis evaluated the effects of isolated IMT on respiratory function, exercise capacity, symptom burden, and safety in adults with PH. (2) Methods: A systematic search was conducted in accordance with PRISMA guidelines. Randomized controlled trials involving adults with PH who underwent isolated IMT were included, and respiratory muscle strength, spirometric parameters, exercise capacity, dyspnea, fatigue, quality of life, and adverse events were the outcomes that were assessed. Data were pooled using meta-analytic techniques where appropriate. (3) Results: A total of 130 participants, assigned to five randomized controlled trials, met the inclusion criteria. IMT significantly improved maximal inspiratory pressure (MD = +24.01 cmH₂O), maximal expiratory pressure (MD = +23.64 cmH₂O), and six-minute walk distance (MD = +60.61 m), but no significant changes were observed in spirometric indices (FEV₁%, FVC%, and FEV₁/FVC). While several individual studies demonstrated clinically relevant improvements in six-minute walk distance, the pooled analysis did not demonstrate a statistically significant effect. IMT consistently reduced dyspnea and fatigue and improved quality-of-life domains. No serious adverse events were reported, and adherence was high. (4) Conclusions: IMT is a safe and feasible adjunct intervention in PH, providing meaningful improvements in respiratory muscle strength and symptom burden. Further large-scale trials are warranted to confirm its long-term clinical benefits.