Abstract Body (Do not enter title and authors here): Background: Endothelial function is closely associated with cardiovascular health among individuals being treated for heart disease. Inspiratory muscle training (IMT) consists of repeated inspirations against a resistance on a handheld device. The effects of high-intensity IMT on endothelial function and arterial stiffness is not well known in this population.
Aim: The aim of this study was to investigate whether high-intensity IMT, beyond usual clinical care, improves endothelial function, arterial stiffness, inspiratory muscle strength, functional capacity, and dyspnea perception in patients with heart disease.
Methods: In this randomized controlled trial participants qualifying for phase two, outpatient cardiac rehabilitation were included. After baseline assessments, participants were randomized to 4 weeks of either high-intensity inspiratory muscle training (IMT) with a resistance set to 60% of baseline maximum inspiratory pressure (MIP) or sham-IMT without resistance (control group). Endothelial function was assessed using flow-mediated dilatation (FMD%), arterial stiffness by pulse wave velocity (PWV), 6-min walk distance (6MWD) was used to quantify functional capacity, dyspnea perception by modified medical research council dyspnea (mMRC) scale, and inspiratory muscle strength by maximal inspiratory pressure (MIP) were assessed. An ANOVA was applied using the intention-to-treat analysis. Data are expressed in mean±SD. Effect sizes presented based on between groups ANOVA.
Results: There were no differences between groups for baseline age, BMI, sex, FMD%, PWV, mMRC, 6MWD and inspiratory muscle strength. No significant changes in the respective measures of interest were observed in the control group (n=6). The intervention group (n=5) experienced significant improvements in FMD% (pre = 5.41 ± 1.93, post = 7.53 ± 1.62, p< 0.05, η² effect size= 0.72), 6MWD (pre = 301.0 ± 39.8, post = 340.4 ± 36.6 meters, p< 0.05, η² effect size= 0.94), mMRC score (pre = 2.8 ± 0.5, post = 1.6 ± 0.6 points, p< 0.05, η² effect size= 0.76), and MIP (pre = 46.4 ± 13.4, post = 68.8 ± 13.6 cmH₂O, p< 0.05, η² effect size= 0.82).There were no significant difference between group in PWV (p> 0.05).
Conclusion: The findings of this study suggest that high-intensity IMT, as a pre-cardiac rehabilitation intervention, produced improvements in endothelial function, MIP, functional capacity, and dyspnea in patients with heart disease.