Design and Implementation of a Novel Passive Magnetically Levitated Nutation Blood Pump for the Ventricular-Assist Device

Gang Chen,Jiaxin Ding,Long Zhang,Rongye Zheng,Ligang Yao

doi:10.1109/access.2019.2955027

Abstract

Considering the wear in mechanical bearings and the requirement for sensors or electrical power in active magnetic bearings, a novel nutation blood pump using a passive magnetic spherical bearing was developed in this paper. A mathematical model was derived to calculate the magnetic forces of the bearing between two pairs of magnetic sleeves in the nutation process. The calculation results demonstrate that the fluctuations of magnetic forces enlarge with the increase in the nutation angle; the magnetic forces obviously increase with the decrease in the air gap, especially along the z-axis. The dynamic magnetic finite element simulation was carried out to validate the mathematical model. The simulation and calculation results of the magnetic forces show consistent trends and provide a theoretical basis for the parameter design. To validate the performance of the pump, computational fluid dynamics (CFD) analyses and in vitro experiments were conducted. The predicted values of the flow velocity vector through the pump, and the wall shear stress, demonstrate that the pump has an antithrombotic property and would not cause serious blood damage. The hydraulic experiment shows that a pressure rise can be achieved in the range of 60–140 mmHg, at a rotational speed of 600–1600 rpm and a flow rate of 0.4–6.7 L/min. The normalized index of hemolysis (NIH) of the nutation pump was 0.0043 ± 0.0008 g/100L. The in vitro tests indicate the feasibility of a magnetically levitated ventricular-assist nutation blood pump for further suspension stability and animal trials.

Highlights

Because of some tricky problems in cardiac transplantation, such as implantation, the long-term management of transplant-related complications, and a serious lack of heart donors, one of the most effective measures for treating end-stage heart failure is the ventricular-assist device (VAD) [1], [2]
Most of the VADs in a clinical setting are designed as centrifugal blood pumps or axial flow blood pumps, such as HeartWare HVAD [3], HeartMate III [4], Terumo DuraHeart [5], and Berlin Heart [6]
NUMERICAL RESULTS In the working process of the nutation pump, the relative position between magnets SI and SII in the spherical bearing, and the magnetic field, is altered, and the interaction force changes with the magnetic field

Summary

Introduction

Because of some tricky problems in cardiac transplantation, such as implantation, the long-term management of transplant-related complications, and a serious lack of heart donors, one of the most effective measures for treating end-stage heart failure is the ventricular-assist device (VAD) [1], [2]. The advantages and disadvantages of centrifugal versus axial flow blood pumps are still in dispute. The new axial flow design is much smaller than the centrifugal pump, it needs rotational speeds of 6000–6500 rpm to maintain an output flow rate of 0–11 L/min. A higher rotational speed may generate a higher magnitude of shear stress, which would result in hemolysis. Both the size and rotational speed reduction of the VAD for the total artificial heart (TAH) are important subjects. Our research team proposed a novel miniscule ventricular assist nutation blood pump that realized a much smaller volume at the same flow

Methods

Results

Conclusion