Linear and Nonlinear Analysis of the Carotid Sinus Baroreflex Dynamic Characteristics

Abstract

The arterial barore ex system is an important negative feedback system that controls arterial pressure (AP) within a normal range during daily activities. We have analyzed this system in anesthetized animals. Several issues need to be considered: the presence of physiological and measurement noises that interfere with the system identi cation, the closed-loop nature of the arterial barore ex system, the existence of parallel feedback systems that may modify the system responses, and the presence of nonlinear responses. We opened the negative feedback loop by surgically isolating the carotid sinus baroreceptor regions from the systemic circulation. We eliminated the effects from parallel feedback systems by sectioning the aortic depressor and vagal nerves. We used a white noise approach to estimate the system characteristics under contamination of physiological and measurement noises. The arterial barore ex system may be divided into the neural and peripheral arc subsystems. The neural arc represents the relationship between pressure inputs and efferent sympathetic nerve activity (SNA), which may be regarded as a controller subsystem. The peripheral arc represents the relationship between SNA and AP, which may be regarded as a plant subsystem. The neural arc reveals derivative characteristics whereas the peripheral arc reveals low-pass characteristics. Numerical simulations based on the analytical results indicate that the neural arc compensates for the slow peripheral arc to optimize the arterial barore ex system in achieving both stability and quickness. Impairment of arterial barore ex function is associated with cardiovascular diseases, and arti cial activation of the arterial barore ex system could be a device-based treatment for cardiovascular diseases associated with sympathetic hyperactivity. To improve the efcacy of such device-based therapy, we may need to understand the interactions between stimulated and non-stimulated barore ex systems. Although static sigmoidal nonlinearity of the arterial barore ex with threshold and saturation phenomena is well documented, dynamic nonlinearities are less understood. Further efforts are warranted to fully understand arterial barore ex function and to apply the knowledge to the medical eld.

Determinants of orthostatic cerebral oxygenation assessed using near-infrared spectroscopy

“…S1). BRS was assessed separately during both types of postural changes as supine to stand typically induces a larger BP drop compared to sit to stand, and previous studies reported BRS to behave non-linearly to different degrees of BP drop (Moslehpour et al, 2016;Kawada et al, 2019;Verma et al, 2017).…”

Linear and nonlinear identification of the carotid sinus baroreflex in the very low‐frequency range

“…In each segment, the linear trend was subtracted, and a Hanning window was applied. The transfer function and magnitude‐squared coherence function were computed via standard nonparametric analysis per segment and then ensemble averaged (Bendat & Piersol, 2010; Kawada et al, 2019).…”

Ivabradine increases the high frequency gain ratio in the vagal heart rate transfer function via an interaction with muscarinic potassium channels

“…The input power spectra [ S VNS·VNS ( f )], output power spectra [ S HR·HR ( f )], and cross spectra [ S HR·VNS ( f )] were calculated over the eight segments via Fourier transform. The transfer function from VNS to HR was estimated from the following equation (Equation ) (Bendat & Piersol, 2010; Kawada, Mukkamala, et al, 2019):…”

“…The magnitude‐squared coherence function was also calculated from the following equation (Equation ) (Bendat & Piersol, 2010; Kawada, Mukkamala, et al, 2019):…”