Development of an axial flow blood pump using a hydrodynamic pressure bearing

研制了一种采用动液压力轴承、磁性流体密封和无刷直流电机的轴流式血泵。这使得叶轮的无接触旋转没有材料磨损。电机转子通过电机轴与叶轮直接连接。电机轴上安装有动水压力轴承。电机和流体动力轴承被安置在一个圆柱形的外壳和防水的磁性流体密封。研制了一种用于轴流式血泵的磁性流体密封。在电机转速高达10,000 rpm时，将密封浸入水中测量密封压力。密封压力超过400mmhg，在流量为4l /min、压力为150mmhg的情况下，密封装置在60天内保持良好状态。细胞生长活性测定结果表明，磁流体对细胞学无不良影响。在允许溶血水平（N.I.H.<0.02）下，所研制的血泵在压差为100 mmHg的情况下可喷射5l /min的血流量。在山羊左心室和降主动脉之间植入轴流血泵。山羊存活了两天，用泵进行了全左心室旁路手术。研制了一种轴流式血泵控制系统。提出了一种基于电机功耗和电机转速的泵流量预测方法。泵流量预测误差小于10%。根据电机电流的波形畸变率自动检测泵的回流和流入套管的阻塞。利用Walsh函数计算畸变率。

An axial flow blood pump was developed using a hydrodynamic pressure bearing, a magnetic fluid seal and a brushless direct current motor. This enabled contact-free rotation of the impeller without material wear. The motor rotor is directly connected to the impeller by a motor shaft. A hydrodynamic pressure bearing is installed on the motor shaft. The motor and the hydrodynamic bearing are housed in a cylindrical casing and are waterproofed by a magnetic fluid seal. The magnetic fluid seal was developed for use in an axial-flow blood pump. Sealing pressures at motor speeds of up to 10,000 rpm were measured with the seal immersed in water. The sealing pressure was above 400 mm Hg. The seal, installed in the pump, remained perfect for 60 days at a flow of 4 L/min against a pressure of 150 mmHg. Results of measurement of cell growth activity indicated that the magnetic fluid has no negative cytological effects. The developed blood pump could eject a flow of 5 L/min at a pressure difference of 100 mmHg with an allowable hemolysis level (N.I.H.<0.02).The axial flow blood pump was implanted in goats between the left ventricle and the descending aorta. The goat survived for two days and a total left ventricular bypass was obtained with the pump.A control system of the axial flow blood pump was developed. A prediction method of the pump flow based on power consumption of the motor and motor speed was proposed. Pump flow was predicted with an error of less than 10%. Backflow through the pump and obstruction of the inflow cannula were automatically detected based on the wave distortion rate of the motor current. The distortion rate was computed using the Walsh functions.