Abstract 2403: Inspiratory Muscle Training Decreases Central and Peripheral Sympathetic Activity Improves Reflex Vasodilatory Blood Flow in Patients with Chronic Heart Failure
Background: Inspiratory muscle training (IMT) improves functional capacity of patients with CHF but the mechanisms of this effect are unknown.
Objective: We tested the hypothesis that IMT could decrease sympathetic activity and improve the reflex muscle vasodilatory response during exercise in patients (CHF) and inspiratory muscle weakness.
Methods: Six patients with CHF and inspiratory muscle weakness (maximal inspiratory pressure <70% of predicted) NYHA Class II–III, EF <35%, peak VO(2) < 20 ml/kg/min, were submitted to a IMT during 12 weeks (30 minute breathing with an inspiratory resistance of 30% of maximal inspiratory pressure). Muscle sympathetic nerve activity (MSNA) was recorded by microneurography, LF (sympathetic) and HF (parasympathetic) components of the heart rate variability and LF/HF ratio were assessed by the use of power spectral analysis of RR interval. Forearm blood flow (FBF) was measured by venous occlusion plethysmography at baseline and during hand grip (HG) manouver. Paired student t-test was used to analyze the impact of IMT in this population.
Results: Compared to baseline, IMT significantly (p < 0,05) caused: an increase in inspiratory muscle force by 130%; a 15% reduction in MSNA (40 ± 1 vs 33 ± 1 bursts/min); an increase in forearm blood flow (0.8+/−0.1 mL/min/100 g) during HG manouver; a decrease in LF% (59 ± 5 vs 39 ± 3 U); an increase in HF% (40 ± 5 vs 61 ± 3 U); a decrease in LF/HF ratio (1,74 vs 0,66).
Conclusions: Twelve weeks of Inspiratory muscle training in patients with CHF and inspiratory muscle weakness promoted a significant improvement in cardiovascular parameters, such as increase in limb blood flow, cardiac autonomic balance and baroreflex sensitivity, associated with a decrease in peripheral sympathetic activity.