Research On Hemodynamics And Physiological Control Of The Pulsatile Flow Left Ventricular Assist Device

The left ventricular assist device(LVAD)assists the failing heart to maintain normal physiological perfusion.Currently,most of the LVADs used in clinical practice operate in a constant speed mode set by the physician,which can lead to reduced aortic flow pulsatility and consequent complications over time,and the constant speed cannot regulate the pump output when the patient’s exercise intensity changes.Therefore,there is a need to modulate the impeller speed waveform to improve blood pulsatility by outputting pulsatile flow and to automatically adjust the pump speed according to the patient’s physiological feedback.This paper will address the hemodynamic and physiological control of pulsatile flow LVAD as follows.Model the equivalent circuit of the cardiovascular system based on the physiological structure and function of the cardiovascular system.Establish the corresponding model based on the function of human pressure reflex mechanism.Simulate the hemodynamic characteristics of the cardiovascular system in healthy human and heart failure patients,compare and analyze the hemodynamic characteristics of healthy human and heart failure patients,and verify the regulation effect of the pressure reflex mechanism model.Model the equivalent circuit based on the hydraulic characteristics of the LVAD and establish the LVAD-cardiovascular system coupling model.Compare and analyze the hemodynamic characteristics of LVAD with constant speed assist and sinusoidal pulsation mode assist by means of numerical simulation.Studying the effects of constant speed components,amplitude and phase shift of sinusoidal speed waveform parameters on LVAD work per beat,aortic blood pulsatility and LVAD hydraulic power.A multi-objective optimization algorithm is used to derive the Pareto front solution set of the waveform parameters and to evaluate the optimization results.Design pulsating flow LVAD physiological control system.Build a nonlinear model predictive controller and a coupled model state observer.Design the control strategy of speed regulation and synchronization based on ECG signal to realize speed regulation with heart rate and synchronization with ECG signal.A pumping regurgitation suppression method in pulsation mode was established.The LVAD physiological control system was simulated by changing the cardiovascular system parameters to evaluate the effectiveness and robustness of the physiological control system.Build a mock circulation system,introduce its key components composition,control system,digital extraction system and the implementation method of pressure reflection mechanism.Experimentally simulated the hemodynamic characteristics during healthy,heart failure and LVAD assisted,and analyzed the effect of pressure reflection mechanism on aortic pressure in the three states;experimentally verified the effect law of sinusoidal speed parameters on work per beat,pulsatility and hydraulic power;used the ECG acquisition device to initially verify the effectiveness of the synchronization control strategy based on ECG signals.