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Mechanically non-contact axial flow blood pump

Mitamura Y., Kido K., Yano T., Sakota D., Yozu R., Okamoto E., Murabayashi S., Nishimura I.

Biocybernetics and Biomedical Engineering

2007

Vol. 27, no. 1-2

139-146

To overcome the drive shaft seal and bearing problem of the rotary blood pump, a hydro-dynamic bearing, a magnetic fluid seal and a brushless DC motor were employed in an axial flow pump. This enabled contact free rotation of the impeller without material wear. The axial flow pump consists of a brushless DC motor, an impeller and a guide vane. The motor rotor is directly connected to the impeller by a motor shaft. A hydrodynamic 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. Impeller shaft displacement was measured using laser sensor. The axial and radial displacements of the shaft were less than a few micrometers for up to 8500 rpm. The shaft did not touch the housing. A flow of 5 L/min was obtained at 8000 rpm at a pressure difference of 100 mmHg. The left ventricular bypass experiment was performed in vitro. With an increase of the motor speed, the bypass flow increased, and at 7000 rpm a total bypass was obtained. The hydrodynamic bearing worked normally under variable load conditions. In conclusion, the axial flow blood pump consisting of a hydrodynamic bearing, a magnetic fluid seal and a brushless DC motor provides contact free rotation of the impeller without material wear.

Current status of the intra-cardiac axial flow pump

Mitamura Y., Yano T., Kido K., Sakota D., Takahashi N., Mori Y., Murabayashi S., Nishimura I., Sekine K.

Biocybernetics and Biomedical Engineering

2006

Vol. 26, no. 1

39-44

Pulsatile artificial hearts having a relatively large volume are difficult to implant in a small patient, but rotary blood pumps can be easily implanted. The objective of this study was to show the feasibility of using the Valvo-pump, an axial flow pump implanted at the heart valve position, in such cases. The Valvo-pump consists of an impeller and a motor. The motor is waterproofed with a magnetic fluid seal. A blood flow of 5 L/min was obtained at a pressure difference of 13.3 kPa at 7,500 rpm. The normalized index of hemolysis (NIH) was 2.6 times the Bio-Pump. The pump was implanted in three goats between the left ventricle and the aorta. The pump bypassed about 85% of cardiac output. The results showed that the Valvo-pump could maintain systemic circulation with an acceptable level of hemolysis.