Numerical Analysis And In Vitro Experimental Investigation Of The Physiological Control System For A Heart Pump

With the increase of patients with heart failure yearly,heart pumps have become an effective treatment for severe heart failure and a transition therapy for heart transplantation.In clinical application,heart pumps often work in the constant-speed control mode for achieving reliability,which decrease the pulsatility and may lead to complications and suction,and so on.In order to solve these problems and to make the heart pump vary with the change of human physiological state,a physiological control system of the heart pump was investigated by numerical simulation and in vitro experiments.Firstly,the coupled cardiovascular-heart pump model was established.Then,both physiological control systems using adaptive fuzzy PI algorithm and PI algorithm were developed respectively,and the influence of physiological control system on the hemodynamic parameters of the coupled system was explored.The main contents of this article were as follows:The coupled cardiovascular-heart pump model was developed to investigate the influence of rotating speed on the hemodynamics in the system.Firstly,cardiovascular model was put forward and its state equation was established.Both health and heart failure in different physiological states were simulated to validate the cardiovascular model.Then,in vitro hydraulic experiments were conducted to establish the model of the rotary heart pump and including determining the model parameters.Finally,after coupling the two models,cardiovascular-heart pump model were put forward and the influence of rotating speed on hemodynamic parameters was studied under open-loop control and the critical suction speeds were determined.Assuming flow deviation as control variable,both adaptive fuzzy PI and PI physiological control systems were put forward and their performance were evaluated by simulation.The simulation results in resting state showed that the error of cardiac output of adaptive fuzzy PI physiological control was 1.52% compared with that of healthy state,better than PI physiological control(3.03%)and could meet the perfusion requirements.The pulsatility coefficients of aortic pressure using adaptive fuzzy PI and PI physiological control system were 0.387 and 0.358 respectively,both higher than the constant speed control system(0.048);(2)The changes of patients’ physiological state(sleep,rest and exercise)were mimicked by adjusting the peripheral resistance.Error of cardiac output of system using adaptive fuzzy physiological control system was 1.98%,lower than that of PI physiological control system(4.91%).The pulsatility coefficients of aortic pressure under adaptive fuzzy PI physiological control were 0.394,0.223 and 0.647 in rest,sleep and exercise,higher than that of PI physiological control and met the physiological requirements.Compared with PI control,the heart pump under adaptive fuzzy PI physiological control could unloading left ventricle,enhance system pulsatility and meet the requirements of assisting when physiological states changes.An in vitro experimental platform was set up to carry out experimental research on the coupled model and the physiological control system.The results demonstrated that the platform could mimic different health states and heart failure states and the hemodynamic parameters were consistent with clinical data.With the left ventricular assisted by the heart pump,hemodynamics parameter of the system in heart failure state improved.Suction experiments presented that the critical suction speed in rest state was 3800r/min,and suction could be eliminated by open-loop control.Changes of physiological states could be achieved by changing heart rate and ventricular contractility.The errors of cardiac output of system using adaptive fuzzy PI physiological control system were 4%,1.6%,2.5%,lower than that of PI physiological control system(10%,6.45%,5%).The pulsatility coefficient of adaptive fuzzy PI physiological control system was 0.442,0.391 and 0.654 in rest,sleep and exercise,higher than that of PI physiological control system(0.401,0.353,0.591).Moreover,the control system had fast response speed when physiological states changed.In vitro experiments confirmed that the adaptive fuzzy PI physiological control system established in this paper had merits in increasing pulsatility,elimination suction and good dynamic performance to meet the requirements of changing states with fast response speed compared with constant-speed control system.