A Mathematical Model to Assess Changes in the Baroreceptor Reflex

TLDR

The model’s four physiologic parameters are meaningful and can be extended to calculate additional metrics such as threshold, saturation, and set point for carotid sinus pressures. It defines the baroreceptor reflex by quantifying the total SAP control range (A(1)), reflex sensitivity (A(2)), the carotid sinus pressure for equal pressor/depressor responses (A(3)), and the minimal SAP achievable by maximal carotid stimulation (A(4)). The model predicts the carotid sinus–systemic arterial pressure relationship with 96 % accuracy, and experimental changes in parameters—e.g., increased A(2) after vagotomy—show that aortic baroreceptors dampen the carotid sinus reflex.

Abstract

A mathematical model relating carotid sinus pressure (CSP) to systemic arterial pressure (SAP) explains the relationship between CSP and SAP with an accuracy of 96 %. The 4 parameters of the model are all physiologically meaningful. They include: the total range of control of SAP (identified as A(l), in mm Hg); the sensitivity of the reflex response (identified as A(2), in mm Hg-1); the carotid sinus pressure from which equal pressor and depressor responses may be elicited (identified as A(3), in mm Hg), and the lower limit to which SAP may be driven by maximal carotid sinus stimulation (identified as A(4), in mm Hg). Several other physiologically meaningful parameters can be calculated from the model, e.g. threshold, saturation, and set point for carotid sinus pressures. Experimental interventions are shown to effect changes in parameters, and these changes can be used to analyze alterations in the reflex response. For example, from the elevated gain, A(2), of the reflex response after vagotomy it can be deduced that the aortic baroreceptors have a damping effect on the carotid sinus reflex response.