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，作为婴幼儿或新生儿的植入式心脏辅助装置。带有三脚架轴承的原型模型于1998年设计，并于1999年建成。为评价其在2000年的性能，进行了模拟循环回路水力性能试验和山羊血溶血试验。试验提出了三点需要改进的地方：1)驱动磁铁与联轴器磁铁之间的长度；2)叶轮下方枢轴轴承的形状；3)叶片上叶轮的形状。为了解决上述问题，我们研制了一种新型的单轴轴承。进行了液压性能试验，比较了三脚架模型和单脚架模型的性能。一种新的模型在相同的血流量下显示了更高的最大血流量，但相同的头部压力。两种模型在压力-流量关系上无差异。一种新的单轴轴承模型比以前的三脚架模型显示了更高的效率。单轴心模型被认为更适合长期使用，然而，其植入试验还需要进一步开发。我们对仔猪进行了急性动物实验，以评估该装置的可植入性。经左胸开胸置入超小型离心泵，左室心尖部流出，降主动脉流入。该泵在低转速下表现出较好的性能，但在高转速下发生了左心室的囊袋现象。我们认为有必要对其装置进行计算机控制。我们开发了一台超小型婴幼儿离心泵的工作模型，并对其从1998年到2001年的水力性能进行了评估。评估长期表现的慢性动物体验是这项研究的下一个目标。

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.