Particle Image Velocimetry Experimental Study on the Flow Field in the Outflow Cannula of an Axial Left Ventricular Assist Pump
1 Chinese Academy of Medical Sciences and Peking Union Medical College, Fuwai Hospital, National Center for Cardiovascular Diseases, State Key Laboratory of Cardiovascular Disease, Beijing 100037, China
2 Department of Cardiovascular Surgery, Chinese Academy of Medical Sciences and Peking Union Medical College, Fuwai Hospital, Beijing 100037, China
Abstract The aim of this work is to study the blood flow distribution in outflow cannula of an axial left ventricular pump and analyze the risk of thrombosis in the axial blood pump outflow cannula according to the relationship between blood flow property and thrombogenesis. We obtained the flow distribution in the central section of the axial blood pump outflow cannula with the two dimensional particle image velocimetry (PIV) system. Then the blood flow distribution in the whole outflow cannula with the three dimensional PIV system was obtained. The rotate speed of the blood pump was set to (10000±20) r/min with flux of 8.05 L/min in the testing. The possibility of thrombogenesis in the axial blood pump outflow cannula was estimated through analyzing the flow property in the outflow cannula. There were spiral flow and flow normal to the wall of cannula nearby the outlet of the blood pump. The two kinds of flow weaken off when the blood flowed through the outflow cannula, so the blood flow far away from the pump outlet was steady. There was not backflow, vortex flow or lowspeed flow region in the whole cannula. The blood flow velocity along the cannula wall increased to the maximum 1.0 m/s from 0 m/s rapidly outside the boundary layer. The blood speed range reduced from 0.7 m/s～2.2 m/s to 1.0 m/s～1.5 m/s along the cannula. The turbulence level near the pump outlet is 0.31. The turbulence level far away from the pump outlet is 0.15. The flow in the cannula become smooth and steady gradually. It is difficult to form thrombus in the cannula caused by blood flow property because there was no backflow, vortex flow or stagnant flow region in the cannula. The outflow cannula can decrease the spiral flow, which is helpful to improve the flow characteristics of the blood flowing from the axial blood pump. The improved flow characteristics can decrease the injury of aorta caused by disorder blood flow.
