Development project of ultra-mini centrifugal pumps as implantable heart assist device for infantsor neonate

自1998年以来，我们开发了超小型离心泵作为婴儿或新生儿的植入式心脏辅助装置。1998年设计了带有三脚架轴承的原型模型，并于1999年建立。2000年进行了模拟循环回路水力性能试验和山羊血溶血试验，对其性能进行了评价。这些试验指出了需要改进的三点：1)驱动磁铁与耦合磁铁之间的长度，2)叶轮下枢轴轴承的形状，3)叶轮上部叶片的形状。为了解决上述问题，我们研制了一种新型单轴轴承。进行了水力性能试验，比较了三脚架和单轴模型的性能。新模型显示，在相同的血流量下，最大血流量更高，但头压相同。两种模型的压力-流量关系无差异。采用单轴轴承的新型轴承比采用三脚架轴承的新型轴承效率更高。单枢轴模型被认为是更可行的长期使用，但其种植试验需要进一步发展。我们对仔猪进行了急性动物实验，以评估该装置的可移植性。采用左开胸，左心尖流出，降主动脉流入的方式植入超小型离心泵。泵在低转速下表现良好，但在高转速下出现左心室囊缩现象。我们觉得有必要对它的装置安装计算机控制系统。我们开发了一种超小型婴儿离心泵的工作模型，并从1998年到2001年对其水力性能进行了估计。通过动物的慢性经验来评估长期表现是本研究的下一个目标。

We have developed ultra-mini centrifugal pumps as implantable heart assist device for infants or neonate since 1998. A prototype model with tripod bearing was designed in 1998 and build up in 1999. Hydrolic performance test with mock circulation loop and hemolytic test with goat blood have been performed to estimate its performance in 2000. These tests pointed out three points to be improved as the followings ; 1 ) length between driving magnet and coupling magnet, 2) shape of a pivot bearing under the impeller, 3) shape of vanes upper impeller. We made a new model with a monopivot bearing to resolve above problems. The hydrolic performance test was performed to compare the performance between a tripod and a monopivot model. A new model showed higher maximum blood flow but the same head pressure under the same blood flow. There were no differences between both models in pressure-flow relationship. A new model with monopivot bearing showed higher efficiency than did a previous model with tripod one. The monovpivot model is considered to be more feasible for long term use, however, there needs further developing for its implant trial.We performed acute animal experiences with piglets to estimate implantability of this device. An ultra-mini centrifugal pump was implanted via the left thoracotomy with the left ventricular apex outflow and descending aorta inflow. The pump revealed reasonable performance under low revolution level, however, sacking to the left ventricte was happened under high revolution level. We feel the necessity ofa computerized control system tor its device.We have developed a working model of an ultra-mini centrifugal pump for infants and have estimated its hydrolic performance since 1 998 to 2001. Chronic animal experience to estimate long term performance is the next target of this study.