国产轴流血泵的血液相容性特征:验证性观察

背景:轴流式血泵是用于心室辅助的主要泵型。前期大量研究结果表明血泵内的不良血液流动特性是导致溶血和血栓的重要因素。目的:在前期轴流血泵的设计图基础上,利用计算机优化技术和计算流体力学的方法,通过改变血泵整体形态及叶轮形状设计一轴流血泵,并装配成型。设计:采用加工后实际测试验证理论设计的合理性。单位:首都医科大学附属北京安贞医院-北京心肺血管疾病研究所生物医学工程研究室与中国航天科技集团总公司北京十四所。材料:血泵泵体及叶轮为钛合金材料,轴承为陶瓷轴承。体外测试用首都医科大学附属北京安贞医院生物医学工程研究室的人工心室辅助装置试验测试台。实验用羊由首都医科大学附属北京安贞医院实验动物房提供。方法:于2005年初开始,首先在中国航天科技集团总公司北京十四所,利用计算机优化技术和计算流体力学技术,基于最大限度减小剪切力和减少流动死区的原则基础上设计血泵的整体形态、叶轮数目和形状、导叶轮的结构和位置以及叶轮的螺距。然后使用数控机床加工成型。最后将轴流血泵安装到首都医科大学附属北京安贞医院生物医学工程研究室的人工心室辅助装置试验测试台上,在输出条件为5L/min流量和13.3kPa压力,流体介质为甘油和水混合液以及新鲜抗凝羊血的条件下,血泵运转4h,每隔0.5h取血样标本。这样通过测试血泵的压力流量输出,以标准溶血指数反映血浆中游离血红蛋白含量,观察泵内血栓形成情况验证血泵的动力学输出性能及血液破坏程度。结果:加工成型后的轴流血泵为泵-机一体结构,包括泵体、叶轮、导叶轮、陶瓷轴承以及进出口等,容积63mL。体外实验结果证实,当血泵运转速度为10000r/min时,它的压力、流量输出为21.01kPa和6.0L/min,其动力学输出性能可以满足患者左心辅助需求,血泵连续运转时其表面温度变化不明显。计算流场显示血泵的内部大多呈层流状态,血泵的体外测试标准溶血指数为(0.047±0.017)g/100L,此数值远远低于以前的轴流血泵,且在血泵内部没有任何血栓形成。结论:经过CAD和CFD方法设计的轴流血泵,在满足左心辅助的压力、流量输出要求同时,血液破坏程度远远小于以前的轴流血泵,提高了轴流血泵的血液相容性。

Blood compatibility of an axial-flow blood pump made in China:Verifying observation

BACKGROUND: Axial-flow blood pump is a main pump for ventricle assistance. Previous researches demonstrate that poor hemocompatibility of blood pump is an important factor for hemolysis and thrombus.OBJ ECTTVE: To design an axial-flow blood pump based on previous kinds of blood pumps through changing whole appearance and impeller shape of the pump by using Computer-Aided Design CAD) and Computational Fluid Dynamics (CFD), and manufacture it successfully.DESIGN: Rationality of theoretical design was verified by practical tests.SETTTNG: Beijing Anzhen Hospital of Capital University of Medical Sciences Department of Biomedical Engineering,Beijing Institute of Heart, lung and Blood Vessel Diseases; the Faurteenth Institute of China-Aerospace Science and Industry Corporation.MATERIALS: Body of blood pump and impeller were titanium alligation, and shaft bearing was ceramic. Test in vitro was accorded to artificial ventricular assist device which was provided by Department of Biomedical Engineering, Beijing Anzhen Hospital of Capital University of Medical Sciences. Experimental goats were provided by Experimental Animal Center, Beijing Anzhen Hospital of Capital University of Medical Sciences.METHODS: Since the beginning of 2005, a model of axial flow blood pump was designed in the 14th Institute of China-Aerospace Science and Industry Corporation base on decreasing shearing force and circulating dead bands. In the process, CAD and CFD were used to generate the geometrical data document of pump's structure, which included the figures of pump's body, shape and number of impeller's vanes, the structure and position of the guide vanes, and the size of impeller's screw-pitch. And then, NC machine tool was used for shaping. Finally, axial-flow blood pump was fixed on artificial ventricular assist device which was provided by Department of Biomedical Engineering, Beijing Anzhen Hospital of Capital University of Medical Sciences. The pump's hemodynamic output was 5 L/min and the average pressure was 13.3 kPa under the mixture of glycerin and water and fresh anticoagulation goat blood. The samples were collected at every one half hour during pumps being pumping for 4 hours. According to testing pressure output of blood pump, normalized index of hemolysis (NIH) was used to reflect content of free hemoglobin in plasma, observe thrombogenesis in pump and verify pump's hemodynamic output and vascular damaging degree.RESULTS: Shaped axial-flow blood pump included body, impeller, guide vanes, ceramic shaft bearing, export and import. The volume was 63 mL. Experimental results in vitro indicated that when the rotation speed of blood pump was 10 000 r/min, its pressure and flow output were 21.01 kPa and 6.0 L/min. The hemodynamic output might satisfy for left ventricular assistance. Surface temperature did not change obviously during successive rotation. The calculation indicated that most parts in blood pump showed a streaming flow. The mean NIH was (0.047±0.017) g/100 L, which was less than that of previous pumps; while, thrombogenesis was not observed in blood pump.CONCLUSTON: Axial-flow blood pump designed by using CAD and CFD can not only satisfy for the hemodynamics of a left ventricular assistant devices, but also the blood damage is milder than previous pumps. Therefore, axial-flow blood pump improves blood compatibility.