Does inspiratory muscle training improve the sympathovagal balance and endothelial function in groups I and IV of pulmonary hypertension

Introduction: Pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension are two subgroups of Pulmonary Hypertension (PH). The pharmacological treatment is usually with vasodilators, but it could be complemented by pulmonary rehabilitation. Thus, considering that PH patients usually have respiratory weakness, the inspiratory muscle training (IMT) could improve treatment to this disease. Our aim was to investigate the effect of IMT on peripheral endothelial function and sympathovagal balance in PH patients. Methods and Results: Twelve patients in functional class II performed IMT using an inspiratory (resistor linear) threshold-loading device (Power Breathe® Plus Medium) in two sets of thirty large respiratory movements-diaphragmatic breathing, twice a day for 8 weeks. The patients performed respiratory muscle strength evaluation, six-minute walking test, electrocardiogram and a brachial doppler ultrasonography before and after the treatment. The spectral analysis showed significant decrease in the LF component, or sympathetic modulation in normalized units (LFnu baseline=59±21 and after IMT=49±17; p=0.048) and increase in the HF component, or parasympathetic modulation (HFnu baseline=41±21 and after IMT=51±17; p=0.048). Also, the sympathovagal balance, seen by the LF/HF ratio, decreased significantly after IMT (LF/HF ratio baseline=2.0±1.4 and after IMT=1.2±0.8; p=0.030). Conclusion: Although the peripheral endothelial function did not show significant difference, the IMT improved the sympathovagal balance in these PH patients, probably reducing the cardiovascular risk.