Effects of high-intensity inspiratory muscle training on inspiratory muscle strength and exercise capacity in pulmonary arterial hypertension

Background Pulmonary arterial hypertension (PAH) is a severe condition characterized by significant exercise intolerance and high mortality rates. Inspiratory muscle weakness is common in PAH and may contribute to ventilatory inefficiency and limited cardiac output during exercise. Although center-based cardiopulmonary rehabilitation programs are recommended to improve exercise performance and alleviate symptoms, their high costs and low adherence rates limit their feasibility for many patients. In response, high-intensity inspiratory muscle training (HI-IMT) has been proposed as a time-efficient, home-based rehabilitation strategy; however, its physiological effects, particularly on exercise hemodynamics, remain incompletely characterized. Methods In a randomized, controlled study, patients with stable PAH(WHO functional class I–III, stable therapy ≥3 months) were randomized into two intervention groups: HI-IMT(60% PImax) and sham (10% PImax)training. Each period included pre- and post-intervention assessments of inspiratory muscle strength and cardiopulmonary exercise testing (CPET). Within-condition changes were evaluated using paired analyses. Results HI-IMT resulted in a significant increase in PImax (mean change +25.18 ± 19.26 cmH₂O; p=0.0005; Cohen’s dz=1.31), whereas no significant change was observed during the sham period. CPET analysis demonstrated no statistically significant changes in peak oxygen uptake (VO₂peak), ventilatory efficiency (VE/VCO₂), or oxygen uptake efficiency slope (OUES)in either condition. Adherence to HI-IMT was high, with a mean completion rate of 95.4 ± 7.2%, intensity adherence of 91.4 ± 8.6%, and technical proficiency of 94.6 ± 5.7%, supporting the feasibility of this home-based intervention. No training-related adverse events were reported. No adverse events related to the intervention were reported. Conclusions In patients with PAH, high-intensity inspiratory muscle training significantly improves inspiratory muscle strength and demonstrates excellent adherence in a home-based setting. Although short-term changes in CPET parameters were not statistically significant, the high feasibility and safety profile support HI-IMT as a practical adjunct to rehabilitation. Larger, adequately powered studies are warranted to determine its impact on exercise performance and clinical outcomes.