The Valsalva maneuver used as a clinical autonomic test features a complex cardiovascular response with a concomitant action of several regulatory mechanisms whose nonlinear interactions are difficult to analyse without the aid of a mathematical model. The aim of this work was to develop a relatively simple model of this maneuver (simpler than the existing models) yet providing a good representation of the corresponding hemodynamic response and thus enabling the assessment of different regulatory mechanisms. A new non-pulsatile com- partmental model of the cardiovascular system was developed with a variable intrathoracic pressure and nonlinear functions to describe pressure-volume relationships of veins, cardiac output dependence on preload and afterload as well as three baroreflex mechanisms acting on heart rate, systemic resistance and venous unstressed volume. The model was validated on data from past Valsalva tests from Padua Hospital in Italy. The proposed model fits well clinical data from patients with both typical and abnormal hemodynamic response to the Valsalva maneuver. The impact of individual baroreflex mechanisms in different phases of the maneuver is clearly visible. The model is most sensitive to the parameters describing the pressure-volume relationship of systemic veins. The model provides a useful tool for analysing the interactions between the cardiovascular system and autonomic regulatory mechanisms and for the interpretation of the Valsalva maneuver results. With certain improvements, the model could be used for the analysis of other reflex tests or different cardio- vascular perturbations.
Modelling cardiovascular hemodynamics during the Valsalva maneuver
Thomaseth Karl;
2015
Abstract
The Valsalva maneuver used as a clinical autonomic test features a complex cardiovascular response with a concomitant action of several regulatory mechanisms whose nonlinear interactions are difficult to analyse without the aid of a mathematical model. The aim of this work was to develop a relatively simple model of this maneuver (simpler than the existing models) yet providing a good representation of the corresponding hemodynamic response and thus enabling the assessment of different regulatory mechanisms. A new non-pulsatile com- partmental model of the cardiovascular system was developed with a variable intrathoracic pressure and nonlinear functions to describe pressure-volume relationships of veins, cardiac output dependence on preload and afterload as well as three baroreflex mechanisms acting on heart rate, systemic resistance and venous unstressed volume. The model was validated on data from past Valsalva tests from Padua Hospital in Italy. The proposed model fits well clinical data from patients with both typical and abnormal hemodynamic response to the Valsalva maneuver. The impact of individual baroreflex mechanisms in different phases of the maneuver is clearly visible. The model is most sensitive to the parameters describing the pressure-volume relationship of systemic veins. The model provides a useful tool for analysing the interactions between the cardiovascular system and autonomic regulatory mechanisms and for the interpretation of the Valsalva maneuver results. With certain improvements, the model could be used for the analysis of other reflex tests or different cardio- vascular perturbations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
