Research On Mock Circulation System Loop With Baro-Reflex Regulation Mechanism

In recent years,the left ventricular assist device(LVAD)have been increasingly used in the treatment of heart failure.The performance of such devices will be strictly evaluated before entering clinical trials.The Mock Circulation System Loop(MCL)can simulate pulsating flow environment under different physiological conditions.It has been widely used in vitro performance evaluation artificial organs.There are many physiological feedback regulation mechanisms in the human circulatory system,among which Baro-Reflex(BR)regulation mechanism is the key mechanism to maintain the stability of human arterial blood pressure.Through the carotid sinus baroreceptor sense the change of blood pressure in human body,after the signal is passed to the central nervous arteries,veins and the heart,change the output of five effectors,venous pressure volume,systemic peripheral resistance,left and right ventricular end systolic elasticity,and the cardiac cycle,to adjust and maintain the stabilization of blood pressure.Therefore,this project has established a MCL with partial BR mechanism,providing a more similar environment to the human blood circulation system for LVAD,and through the experiment research,analysis system response characteristics of hemodynamic parameters,verify the validity of MCL with BR mechanism and the physiological rationality of BR regulation.The research is mainly carried out from the following aspects:Firstly,established biventricular MCL system platform is improved under the guidance of the CAMSIM model with BR algorithm carried out by the research group earlier,realize the design of MCL with partial BR mechanism.The BR control algorithm is integrated into MCL control software based on Lab VIEW development environment,so that the system can complete the dynamics of the effector peripheral resistance(Rscp)and cardiac cycle(T_hb)in the algorithm according to the mean aortic pressure(mAoP)feedback value.The combination of single chip microcomputer and electric actuator is used to simulate the peripheral resistance,and the model relationship between Rscp and actuator opening in the BR algorithm is established to realize automatic adjustment of the peripheral resistance.At the same time,the model relationship between T_hb and linear motor speed is established to realize the automatic adjustment of the cardiac cycle.Then,hemodynamic simulation experiments were performed in MCL,to simulate baseline and LVAD assist heart failure physiological state.The left atrial pressure(LAP)and blood volume(BV)were selected as the experimental variables to simulate the disturbance of human physiological state.The hemodynamic parameter response under single effector parameter Rscp,T_hb regulation and double effector parameters Rscp and T_hb co-regulation was studied.When the aortic pressure of the system is mutated under physiological disturbance,the MCL can restore the blood pressure within 15s by adjusting the Rscp and T_hb under the action of partial BR mechanism.In addition,the LVAD was integrated into the MCL,the hemodynamic response under different experimental variables was studied by setting the flow assistant states of 3L/min and 5L/min.Experiments show that under the assisted flow of LVAD,the effectors still had a moderating effect on aortic pressure,but the effect was reduced due to the strong auxiliary effect of LVAD.At the same times,the pulsatility of aortic pressure changes significantly.When LAP and BV increase,the ventricular pressure increases and the pulsatility of aortic pressure increases.When LAP and BV decrease,the ventricular pressure decreases,the pressure of the aortic end systole and the pulsatility is reduced.Finally,comparing the experimental data results with previous simulation experiments and clinical data documents,the effectiveness and physiological rationality of MCL system with partial BR mechanism in regulating hemodynamic parameters have been verified.Experimental data show that the system can accurately simulate the results of hemodynamic parameters under baseline physiological conditions by the control of a single effector or dual effectors.The variation results of hemodynamic parameters of MCL system after being disturbed are consistent with the simulation results.And it's conformed to the real physiological parameter variation characteristics of human body.According to the trend analysis of mAoP changes,it is concluded that the regulation time of effector parameters to the system is between 6.78?11.32 s,in which the regulation efficiency of cardiac cycle is higher than peripheral resistance,and the regulation time of parameters is consistent with the clinical experimental results.Partial BR mechanisms realized achieve the target requirements for blood pressure regulation of the system,and this result has important guiding significance for LVAD before clinical trials.