Role of the Baroreflex in Cardiovascular Instability: A Modeling Study

Authors: Magosso E.¹; Biavati V.¹; Ursino M.²

Source: Cardiovascular Engineering: An International Journal, Volume 1, Number 2, June 2001 , pp. 101-115(15)

Publisher: Springer

Abstract:

A mathematical model of the short-term arterial pressure control is used to investigate the possible origin of blood pressure waves (Mayer waves) and of heart rate variability signals. The model includes an elastance-variable pulsating heart, the pulmonary and systemic circulation, the mechanical effect of respiration on venous return, and the regulatory actions of two groups of baroreceptors: the high-pressure (i.e., arterial) baroreceptors and the low-pressure (i.e., cardiopulmonary) baroreceptors. The feedback mechanisms work by modulating the peripheral resistances, the venous unstressed volumes, the ventricle end-systolic elastance and the heart period. The last mechanism involves a balance between sympathetic and vagal control actions. The basal value of all parameters in the heart and vascular model has been given to mimic a normal human hemodynamic. Parameters in the feedback regulation mechanisms have been assigned on the basis of open loop experiments in vagotomized dogs (as to the sympathetic arterial baroreflex) and neck chamber or lower body negative pressure experiments in human volunteers (as to vagal response and cardiopulmonary baroreflex). A sensitivity analysis on the gains and time delays of the feedback mechanisms revealed that (i) a significant increase in the gains and time delays (above 9 s) of all the arterial baroreflex sympathetic mechanisms is required to induce instability. In this condition, systemic arterial pressure exhibits spontaneous oscillations with a period of about 20 s, similar to Mayer waves. The control of peripheral resistance seems more important than the venous volume control in the genesis of these oscillations. (ii) An increase in the gain and time delay (above 3 s) of the arterial baroreflex vagal mechanism causes the appearance of unpredictable fluctuations in heart period, with spectral components in the range 0.08–0.12 Hz. These fluctuations originate after a double period bifurcation. (iii) The cardiopulmonary baroreflex plays a less important role in the genesis of the aforementioned instability phenomena.

Keywords: cardiovascular variability; Mayer waves; heart rate fluctuations; arterial baroreceptors; cardiopulmonary baroreceptors

Language: English

Document Type: Regular paper

Affiliations: 1: Department of Electronics, Computer Science and Systems, University of Bologna, Bologna, Italy 2: Department of Electronics, Computer Science and Systems, University of Bologna, Bologna, Italy. mursino@deis.unibo.it

Publication date: 2001-06-01

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• In this Subject: Cardiovascular Medicine ,  Pathology ,  Pharmacology
• By this author: Magosso E. ;  Biavati V. ;  Ursino M.

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