| Heart failure is a life threatening disease with increasing incidence. Mortality of endstage heart failure is high. In the light of lack of donor hearts, ventricular assist devices(VADs) have become an therapeutic solution to treat end-stage heart failure in Europe and the U.S.A.. VADs is a form of mechanical circulatory support, capable of bridge the patient to heart transplantation, myocardial recovery, or as a destination therapy. VADs can assist or even replace the pumping function of the heart to maintain the circulation, increase organ perfusion, and offload the heart.CAMSIM model is a lumped parameter model, which is an electric circuit equivalent based on the Windkessel model. The CAMSIM model comprised several functional modules, where the vascular resistance, compliance, and blood inertia are represented by electric resistance R, capacitance C, and inductance L, respectively. As each parameter has its physiological meaning, various physiological/hemodynamic conditions of the human body can be simulated by adjusting the values of the parameters. The functional modules of the base CAMSIM model include the heart, pulmonary circulation, systemic circulation, coronary circulation.Because carotid sinus baroreceptor reflex plays a vital role in the short-term regulation of blood pressure, a carotid baroreflex module has been developed and incorporated into the base CAMSIM model.. When the carotid sinus baroreceptor, locating at the carotid vessel, senses the change of blood pressure, the baroreflex regulatory mechanisms is induced the signal is delivered to the central nervous system by afferent pathway. The central nervous system then delivers the feedback signal through the efferent sympathetic and vagus nerve to the heart、arteries, and veins. Finally, the left and right ventricular systolic elastance, length of cardiac cycle, venous unstreched volume, and systemic peripheral resistance respond to the nerve signal to quickly adjust blood pressure. The carotid baroreflex module was developed based on previous physiology literature. The module was incorporated into the CAMSIM model and the baseline physiological conditions(healthy and heart failure) were verified according to clinical data and animal studies in the literature.The fuction of the carotid baroreflex module was demonstrated by manual alteration(open-loop test) of the left atrial pressure and venous unstreched volume. Finally, the LVAD assisted heart failure condtion was simulated with and without carotid sinus baroreflex module, the results were collected and compared.The results showed that the values of the simulated hemodynamic parameters for baseline physiological condtions satisfied the target values set by clinical data. In the openloop tests of manual increase of left atrial pressure(LAP), the cardiac output and mean aortic pressure increased with the left atrial pressure. Meanwhilethe left and right ventricular systolic elastance and peripheral resistance were reduced while length of cardiac cycle and venous unstreched volume increased. These results are in line with the physiological characteristics. In the open-loop tests of manual reduction of blood volume, the aortic pressure and cardiac output reduced with the blood volume. Meanwhile, the left and right ventricular end-systolic elastances and peripheral resistance increased while the length of cardiac cycle and venous unstreched volume reduced. The cardiac output and aortic pressure have been shown more stable with carotid baroreceptor regulation in the CAMSIM model.In the LVAD assisted heart failure simulation results confirmed the cardiac ourput and mean aortic pressure increased with the affect of rotate speed. Meanwhilethe left and right ventricular systolic elastance and peripheral resistance were reduced while length of cardiac cycle and venous unstreched volume increased. CAMSIM lumped parameter added carotid baroreceptor module to improve the model so that the model simulation results more in line with the hemodynamic characteristics. |
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