Shida Shuya, Masuzawa Toru, Osa Masahiro
1 Graduate School of Science and Engineering, Ibaraki University, Hitachi, Japan.
2 Department of Mechanical Engineering, Ibaraki University, Hitachi, Japan.
Int J Artif Organs. 2019 Jun;42(6):291-298. doi: 10.1177/0391398819833372. Epub 2019 Mar 11.
Flow rate estimation for ventricular assist devices without additional flow sensors can improve the quality of life of patients. In this article, a novel flow estimation method using the passively stabilized displacement of a magnetically levitated impeller is developed to achieve sufficient accuracy and precision of flow estimation for ventricular assist devices in a simple manner. The magnetically levitated impeller used is axially suspended by a magnetic bearing in a centrifugal blood pump that has been developed by our group. The radial displacement of the impeller, which is restricted by passive stability, can be correlated with the flow rate because the radial hydraulic force on the impeller varies according to the flow rate. To obtain the correlation with various blood viscosities, the relationships between the radial displacements of the magnetically levitated impeller and the pressure head-flow rate characteristics of the pump were determined simultaneously using aqueous solutions of glycerol with a potential blood viscosity range. The measurement results showed that accurate steady flow rates could be estimated with a coefficient of determination of approximately 0.97 and mean absolute error of approximately 0.22 L/min without fluid viscosity measurements by using the relationships between the impeller displacement and the flow rate. Moreover, a precision of approximately 0.01 (L/min)/µm was obtained owing to a strong estimation indicator signal provided by the large displacement of the passively stabilized impeller; thus, the proposed estimation method can help ensure sufficient accuracy and precision for ventricular assist devices in a simple manner, even if the blood viscosity is unknown.
对于没有额外流量传感器的心室辅助装置，流量估计可以提高患者的生活质量。在本文中，开发了一种利用磁悬浮叶轮的被动稳定位移的新型流量估计方法，以简单的方式实现心室辅助装置流量估计的足够准确性和精度。所使用的磁悬浮叶轮由我们团队开发的离心血泵中的磁轴承轴向悬浮。叶轮的径向位移受被动稳定性限制，由于叶轮上的径向液压力随流量变化，因此可以与流量相关联。为了获得与各种血液粘度的相关性，使用具有潜在血液粘度范围的甘油水溶液同时确定磁悬浮叶轮的径向位移与泵的压头-流量特性之间的关系。测量结果表明，通过使用叶轮位移与流量之间的关系，无需测量流体粘度，就可以估计出准确的稳定流量，测定系数约为0.97，平均绝对误差约为0.22升/分钟。此外，由于被动稳定叶轮的大位移提供了强大的估计指标信号，获得了约0.01（升/分钟）/微米的精度；因此，即使血液粘度未知，所提出的估计方法也可以以简单的方式帮助确保心室辅助装置具有足够的准确性和精度。
