Effects of Inspiratory Muscle Training on Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative movement disorder that provoke motors and non-motors symptoms causing further dependence and disability. Among non-motor issues, orthostatic hypotension (OH) is a severe manifestation of autonomic dysfunctions, occurring in approximately 30% of those with PD. The fall in blood pressure (BP) during orthostatic position (ORT) is normally compensated to maintain adequate cerebral blood flow (CBF) through autoregulation of cerebral vessels (AC). However, if AC is compromised, CBF may decrease and cause pre-syncope symptoms such as dizziness and loss of balance. Inspiratory muscle training (IMT) is a non-pharmacological strategy to improve respiratory muscle strength, cerebrovascular, cardiovascular control in several populations. However, the effects of IMT on cardiovascular autonomic control (i.e. baroreflex sensitivity-BRS), hemodynamic and AC during ORT in PD patients with and without orthostatic hypotension have not yet been studied. Our hypothesis is that IMT will increase inspiratory muscle strength and influence spontaneous breathing pattern, improving BRS. In addition, IMT will cause a smaller drop in BP and CBF during ORT. Furthermore, maintaining CBF will reduce postural instability during ORT. PD patients without and with OH (PD-OH) will participate in the study and will be randomly divided into two groups recruited at the Antônio Pedro University Hospital. The experimental group will perform 6-8 weeks of training at 30-75% of maximum inspiratory pressure (MIP), and the placebo group will perform the same training protocol at 5% of MIP (sham). The home-based protocol will be of 30 repetitions twice a day, five days a week. In active ORT test, BP, R-R intervals, stroke volume, cardiac output, respiratory rate, ventilatory variables and mean cerebral blood flow velocity (MCAv) will be continuously monitored for 10 minutes in the supine position (SUP), 10 minutes in the sitting position and then 6 minutes in the ORT position. Oscillations of the body's center of pressure (COP), through a force platform, and neuromuscular responses of the gastrocnemius and tibialis anterior muscles, through surface electromyography, will be recorded while maintaining the ORT position. The orthostatic test will be performed before and after the interventions (placebo and experimental). We believe that IMT will promote an improvement in BRS, AC, and postural control, presenting itself as a potential non-pharmacological countermeasure in autonomic dysfunctions and in the prevention of falls in Parkinson's disease.