Ringwood, John and Malpas, Simon C. (2001) Slow oscillations in blood pressure via a nonlinear feedback model. American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, 280 (4). R1105-R1115. ISSN 0363-6119

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Abstract

Blood pressure is well established to contain a potential oscillation between 0.1 and 0.4 Hz, which is proposed to reflect resonant feedback in the baroreflex loop. A linear feedback model, comprising delay and lag terms for the vasculature, and a linear proportional derivative controller have been proposed to account for the 0.4-Hz oscillation in blood pressure in rats. However, although this model can produce oscillations at the required frequency, some strict relationships between the controller and vasculature parameters must be true for the oscillations to be stable. We developed a nonlinear model, containing an amplitude- limiting nonlinearity that allows for similar oscillations under a very mild set of assumptions. Models constructed from arterial pressure and sympathetic nerve activity recordings obtained from conscious rabbits under resting conditions suggest that the nonlinearity in the feedback loop is not contained within the vasculature, but rather is confined to the central nervous system. The advantage of the model is that it provides for sustained stable oscillations under a wide variety of situations even where gain at various points along the feedback loop may be altered, a situation that is not possible with a linear feedback model. Our model shows how variations in some of the nonlinearity characteristics can account for growth or decay in the oscillations and situations where the oscillations can disappear altogether. Such variations are shown to accord well with observed experimental data. Additionally, using a nonlinear feedback model, it is straightforward to show that the variation in frequency of the oscillations in blood pressure in rats (0.4 Hz), rabbits (0.3 Hz), and humans (0.1 Hz) is primarily due to scaling effects of conduction times between species.

Item Type:	Article
Keywords:	sympathetic nervous system; baroreflex; stability; describing function; artificial neural network;
Academic Unit:	Faculty of Science and Engineering > Electronic Engineering
Item ID:	9507
Identification Number:	https://doi.org/10.1152/ajpregu.2001.280.4.R1105
Depositing User:	Professor John Ringwood
Date Deposited:	05 Jun 2018 15:43
Journal or Publication Title:	American Journal of Physiology: Regulatory, Integrative and Comparative Physiology
Publisher:	American Physiological Society
Refereed:	Yes
URI:	https://www.physiology.org/journal/ajpre...
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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