DEVELOPMENT OF A TOTALL IMPLANTABLE, MOTOR DRIVEN ARTIFICIAL HEART SYSTEM

在这个项目中，与德国亚琛技术大学赫尔姆霍兹生物医学工程研究所的H Reul教授小组合作，主要目标是开发一种完全可植入的、超紧凑的机电全人工心脏（TAH）和心室辅助装置（VAD）。TAH和VAD系统都是基于通过皮肤传输电能，使用经皮能量传输（TET）系统为植入的血泵供电。所述植入组件包括所述泵送单元、依从室、内部电池和控制器。TAH抽油机采用一体式设计，在左右泵之间夹有一个机电致动器。VAD使用与TAH相同的致动器，并使用背板覆盖TAH的右侧。TAH直径90mm，厚度70mm，体积400cc，重量450g。VAD的尺寸分别为90mm和56mm，体积为275cc，重量为460g。虽然缩小了尺寸，但在泵送速率为160BPM时获得了8L/min的最大流量。TAH所需的功率范围为10至15瓦，而VAD所需的功率范围为5至8瓦。TAH的最大电液转换效率为13.5%，VAD的最大电液转换效率为23%。作为体积补偿器，TAH设计了55cc的充气腔，VAD设计了75cc的充气腔。柔性膜材料为聚氨酯，厚度约为0.2mm。用TAH和VAD测试了镍氢和锂离子二次可充电电池的性能。在终端电压为16V的情况下，两个电池都能够为人工心脏供电超过2小时。VAD和TAH的体内研究刚刚开始评估它们的耐久性和生物相容性。当长期耐久性和生物相容性得到证明时，我们将进入临床试验。除了脉动系统，我们也开始设计和评估离心血泵。离心血泵是一种支撑叶轮的三脚架机构。得到了水头压力-流量的基本性能。结果表明，样机泵满足左心室辅助装置的要求。然而，由于三脚架和聚乙烯槽界面的高摩擦磨损，我们将泵设计为单枢轴轴承机构。随着叶轮稳定性的提高，该泵可以满足临床心室辅助装置的要求。今后将进行进一步的研究。作为人工心脏植入患者的监测系统，研制了一种测量血红蛋白水平和血氧饱和度的光学反射传感器。它在血红蛋白水平和氧饱和度方面的准确性用牛血进行了评估。结果表明，如果该传感器的长期性能已在动物身上得到证实，则该传感器可用于连续监测患者。通过与Helmohotz研究所的合作，我们很幸运地不仅交换了工作人员，而且交换了学生。我们接收了三位从事光学传感器项目的硕士生。我们的一名学生花了六个月的时间在亚琛学习计算流体动力学方法来分析连续血流装置内的血流模式。此外，我们还组织了两次日德人工心脏研讨会，一次是在1998年，一次是在2000年。通过这些交流项目，我们有幸学习到有价值的信息，以帮助更好地设计和分析血泵数据。我认为交流项目为学生和工作人员提供了宝贵的经验。少

In this project, in collaboration with Prof. H Reul's group of Helmholtz Institute of Biomedical Engineering, TechnicalUniversity Aachen, Aachen, Germany, the main objective was to develop a totally implantable, ultracompact electromechanical total artificial heart (TAH) and ventricular assist device (VAD). Both TAH and VAD Systems are based on transmitting the electrical energy through skin using a transcutaneous energy transmission (TET) system to power the implanted blood pump. The implanted components include thes pumping unit, compliance chamber, internal battery, and the controller. The TAH pumping unit is an one-piece design sandwiching an electromechanical actuator between the left and right pumps. The VAD was made using the same actuator as TAH's and covering the right side of the TAH with a backplate. The diameter and thickness of the TAH are 90mm and 70mm, respectively, and its volume is 400cc with the weight being 450g. Those of the VAD are 90mm and 56mm, respectively, yiel … More ding the volume of 275cc and weight of 460g. Although downsized, the maximum floy of 8L/min was obtained at the pumping rate of 160BPM. The power required for TAH ranged from 10 to 15 watts, while that of VAD from 5 to 8 watts. The maximum electrical to hydraulic efficiency of the TAH was 13.5% and that for VAD was 23%.As a volume compensator, 55cc air-filled chamber was designed for TAH, while for VAD 75cc chamber. The flexing membrane was made of polyurethane with its thickness being around 0.2mm. The secondary rechargeable batteries such as NiMH and Li-ion were tested for their performance with the TAH and VAD. With the terminal voltage of 16V, both batteries were able to power the artificial heart for over a duration of 2 hours.In vivo studies with VAD and TAH have just started to evaluate their durability and biocompatibility. When long term durability and biocompatibility were demonstrated, we will move into clinical trials.In addition to pulsatile systems, we also started to design and evaluate the centrifugal blood pump. The centrifugal blood pump is a tri-pod mechanism supporting the impeller. The basic performance in terms of head pressure-flow was obtained. The results indicated that the prototype pump meet the requirements as the left ventricular assist device. However, because of high friction wear at the tri-pod and polyethylene groove interface, we changed the pump design to a single pivot bearing mechanism. With improvement in impeller stability, this pump may meet requirements for clinical ventricular assist device. Further study will follow in future.As a monitoring system of the artificial heart implanted patient, an optical reflectance sensor to measure blood hemoglobin level and oxygen saturation was developed. Its accuracy in terms of hemoglobin level and oxygen saturation was evaluated using bovine blood. The results indicated feasibility of the sensor for continuous patient monitoring, provided its long term performance has been proven in animals.Through collaboration with Helmohotz Institute, we were fortunate to exchange not only the staff members, but also students. We received three master's students who worked on the optical sensor project. One of our students spent six months in Aachen learning computation fluid dynamic approach to analyze blood flow pattern inside the continuous flow devices. Also, we organized two Japan-Germany artificial heart symposiums, one in 1998 and the other in 2000. Through these exchange programs, we were fortunate to learn valuable information to help better design and analyze blood pump data. I think exchange program provided valuable experience to the students as well as staff members. Less