Graduate School of Science and Engineering, Ibaraki University, Hitachi, Japan.
Int J Artif Organs. 2020 Dec;43(12):774-781. doi: 10.1177/0391398820917149. Epub 2020 May 11.
Implantable ventricular assist devices are a type of mechanical circulatory support for assisting the pumping of the heart. Accurate estimation of the flow rate through such devices is critical to ensure effective performance. A novel method for estimating the flow rate using the passively stabilized position of a magnetically levitated impeller was developed by our group. However, the performance of the method is affected by the gravity vector, which depends on the patient's posture. In this study, the effects of gravity on the flow estimation method are analyzed, and a compensation method is proposed. The magnetically levitated impeller is axially suspended and radially restricted by passive stability in a centrifugal blood pump developed by our group. The gravity effects were evaluated by analyzing the relationships between the radial position of the magnetically levitated impeller and the flow rate with respect to the gravity direction. Accurate estimation of the flow rate could not be achieved when the direction of gravity with respect to impeller was unknown. A mean absolute error of up to 4.89 L/min was obtained for flow rate measurement range of 0-5 L/min. However, analysis of the equilibrium of forces on the passively stabilized impeller indicated that the effects of gravity on the flow estimation could be compensated by performing additional measurements of the gravity direction with respect to impeller. The method for compensating the effects of gravity on the flow estimation should improve the performance of therapy with the implantable ventricular assist devices.
植入式心室辅助装置是一种用于辅助心脏泵血的机械循环支持装置。准确估计此类装置的流量对于确保有效性能至关重要。我们小组开发了一种使用磁悬浮叶轮被动稳定位置估计流量的新方法。然而，该方法的性能受到重力矢量的影响，而重力矢量取决于患者的姿势。在这项研究中，分析了重力对流量估计方法的影响，并提出了一种补偿方法。我们小组开发的离心式血液泵中，磁悬浮叶轮通过被动稳定性轴向悬浮并径向限制。通过分析磁悬浮叶轮的径向位置与相对于重力方向的流量之间的关系，评估了重力的影响。当不知道叶轮相对于重力的方向时，无法准确估计流量。在 0-5 L/min 的流量测量范围内，流量测量的平均绝对误差高达 4.89 L/min。然而，对被动稳定叶轮上的力平衡进行分析表明，通过对叶轮相对于重力的方向进行额外测量，可以补偿重力对流量估计的影响。补偿重力对流量估计影响的方法应能提高植入式心室辅助装置治疗的性能。
