Baroreflex sensitivity assessment and heart rate variability: relation to maneuver and technique

Abstract

In the present study, we examined two baroreflex sensitivity (BRS) issues that remain uncertain: the differences among diverse BRS assessment techniques and the association between BRS and vagal outflow. Accordingly, the electrocardiogram and non-invasive arterial pressure were recorded in 27 healthy subjects, during supine with and without controlled breathing, standing, exercise, and recovery conditions. Vagal outflow was estimated by heart rate variability indexes, whereas BRS was computed by alpha-coefficient, transfer function, complex demodulation in low- and high-frequency bands, and by sequence technique. Our results indicated that only supine maneuvers showed significantly greater BRS values over the high frequency than in the low-frequency band. For maneuvers at the same frequency region, supine conditions presented a larger number of significant differences among techniques. The plots between BRS and vagal measures depicted a funnel-shaped relationship with significant log-log correlations (r=0.880-0.958). Very short latencies between systolic pressure and RR interval series in high-frequency band and strong log-log correlations between frequency bands were found. Higher variability among different baroreflex measurements was associated with higher level of vagal outflow. Methodological assumptions for each technique seem affected by non-baroreflex variation sources, and a modified responsiveness of vagal motoneurons due to distinct stimulation levels for each maneuver was suggested. Thus, highest vagal outflows corresponded to greatest BRS values, with maximum respiratory effect for the high-frequency band values. In conclusion, BRS values and differences across the tested techniques were strongly related to the vagal outflow induced by the maneuvers.

Increased sympathetic modulation and decreased response of the heart rate variability in controlled asthma

“…An increase in HR occurs in the inspiratory phase whereas in the expiratory phase there is a reduction of HR. This phenomenon is explained by the decrease and increase of the vagal activity, respectively [9]; which is known as respiratory sinus arrhythmia (RSA) [10,11]. Furthermore, in experimental conditions, the RSA can be exacerbated by controlled respiratory maneuvers (M-RSA) [12].…”

Deep breathing heart rate variability is associated with respiratory muscle weakness in patients with chronic obstructive pulmonary disease

“…In this context, heart-rate (HR) autonomic control can be assessed using HR and R-R interval indexes obtained during the respiratory sinus arrhythmia (RSA) as parasympathetic integrity markers over the sinus node. The RSA is characterized by the physiologic oscillations of HR occurring in synchronicity with the respiratory cycle 8,9. During respiration, there is an identifiable relationship between inspiration and increased in HR, caused by the withdrawal of vagal tone, and between expiration and reduced in HR, caused by increased vagal activity on the sinus node.…”

Instantaneous Response Patterns of Baroreflex Sensitivity, Respiratory Sinus Arrhythmia Sensitivity and Vagal Activity to Cold Face Test and Active Orthostatic Test

“…Steady-state spectral analysis of cardiovascular variability has been performed after the first minute of the maneuver onset. In these conditions, it has been reported that the LFRR/HFRR ratio increases and that both HFRR and BRS are reduced [2].…”

“…While AOT provokes baroreflex sensitivity (BRS) reduction and shifts the autonomic balance towards sympathetic predominance [2], CFT elicits increases of vagal activity, BRS and respiratory sinus arrhythmia sensitivity (RSAS) [3]. It has been reported that great fluctuations of arterial pressure (AP) and heart rate (HR) occur in the first minute of AOT [4,5] and CFT [6].…”