The Hemodynamic Study On The Performance Of Ecmo Centrifugal Blood Pump With Different Shroud Design

Extracorporeal membrane oxygenation(ECMO)is a derivative of extracorporeal circulation and has been a powerful tool for the treatment of patients with severe heart and lung failure.However,patients receiving ECMO support still suffer from high rates of complications,such as bleeding,thrombosis and hemolysis.These complications limit the clinical application of ECMO.The centrifugal blood pump is the power source of the ECMO system,and the high-speed rotation of the impeller causes great damage to various components of the blood.The shroud is a baffle which between the blade and blood,and its influence on the fluid of the pump is very critical.However,the hemodynamic performance of the shroud design on the blood pump has not been studied extensively.In this paper,the influence of different shroud designs on the hemodynamic parameters of the pump under design conditions(4000 rpm,5 L/min)was clarified by the method of computational fluid dynamics,and the influence of the shroud design on the hydraulic performance of the pump was explored by the fluid experiment.The research contents are as follows:1.Numerical simulation study on the influence of the change of the covering location of the shroud on the hemodynamics of the centrifugal pump: The designs of the shroud with two different coverage positions was established.The hemodynamic analysis of the flow field in the centrifugal pump was carried out by the numerical simulation.The hemodynamic parameters were analyzed to study the influence of the covering location of the shroud on the blood damage and hydraulic performance.2.Numerical simulation study on the influence of the change of the covering proportions of the shroud on the hemodynamic characteristics of the centrifugal pump:Six shroud designs with the covering proportions of 0,1/5,2/5,3/5,4/5,1 were made.The method of computational fluid dynamics was used for numerical calculation and the results of the velocity flow field,wall shear stress,modified index of hemolysis(MIH),head and efficiency were analyzed to evaluate the hemodynamics performance of the centrifugal blood pump.The influence of the change of the proportion of the shroud on the damage of blood and hydraulic performance of the pump was studied by the comparison of these hemodynamic parameters.3.Experimental study on the influence of the shroud design on hydraulic performance of centrifugal pump: The models of the pumps were established by the method of 3D printing,and the hydraulic experimental platform was built to test the hydraulic performance of the centrifugal pump under various working conditions.The influence of different designs of the shroud on the hydraulic performance of the centrifugal pump was further analyzed and the experimental data was compared with the simulation results to verify its accuracy on the simulation.The research results show that: 1.The design of the shroud increases the number of turbulent areas between the volute and the impeller and these turbulent areas are mainly concentrated at the inlet and outlet of the shroud.The shroud design covering the trailing edge of the blade raises the velocity near the outlet of the impeller,and the high velocity region further increases as the increase of the covering proportions.2.In the same covering proportion,the fraction of fluid volume with shear stress values above a threshold(9 Pa,50 Pa,150 Pa)and the MIH were higher in the pump whose shroud covers the trailing edge of the blade than the design whose shroud covers the leading edge of the blade.In the same coverage position,the fraction of fluid volume with scalar shear stress values above a threshold(9 Pa,50 Pa,150 Pa)and MIH have a tendency to increase as the rise of the shroud covering proportions.3.The design of the shroud in the blood pump can improve its hydraulic performance.In the same working condition,the head and efficiency of the pump increased with the rise of the covering proportion and they were higher in the pump whose shroud covers the blade trailing edge in the same covering proportion.Conclusion: The design of shroud has a great influence on the performance of the centrifugal pump.The shroud increased the hydraulic performance of pump and it would cause more blood damage in the pump with a shroud design.The shroud covering the trailing edge of the blade would cause more damage to various components of the blood than the design covering the leading edge of the blade,and its rate of hemolysis is higher,but its head and efficiency are larger.Furthermore,the increase of the proportion of shroud would cause more risk of the destruction of von Willebrand factor(v Wf),the activation of platelet and the damage of erythrocyte,and the rate of hemolysis increased,but its hydraulic performance gradually improved.This means that the risks of the hemolysis,thrombosis and bleeding increased as the rise of the covering proportion and they were higher in the pump whose shroud covers the blade trailing edge.