The effect of the impeller-driver magnetic coupling distance on hemolysis in a compact centrifugal pump.

Blood trauma is one of the important performance parameters of centrifugal pumps. To investigate the blood trauma induced by these pumps, in vitro hemolysis tests have become an important procedure and are increasingly used for pump development and comparisons. The Baylor compact eccentric inlet port (CIE) centrifugal blood pump was developed as a long-term centrifugal ventricular assist device (VAD) as well as a cardiopulmonary bypass pump (CPB). The Baylor CIE pump incorporates a seal-less design with a blood stagnation-free structure. This pump can provide flows of 5 L/min against 350 mm Hg of total pressure head at 2,600 revolutions per minute. The pump impeller is magnetically coupled to the driver magnet in a seal-less manner. The latest hemolysis study revealed that hemolysis may be affected by the gap distance between the driver and the impeller magnet. The purpose of this study was to verify the effect of the magnetic coupling distance on the normalized index of hemolysis (NIH) with the CIE model and to obtain an optimal gap distance. The NIH value was clearly decreased by alteration of the magnetic coupling distance from 7.7 to 9.7 mm in CPB and left ventricular assist device (LVAD) conditions. The NIH, when using the pump as an LVAD condition, was reduced to a level of 0.0056 from 0.095 when the magnetic coupling distance was extended. The same results were also obtained when the pumps were used in a CPB condition. The magnetic coupling distance is an important factor for the CIE model in terms of hemolysis. Different coupling forces effect the bearings and impeller stability. These results suggest that an optimal driving condition with a proper magnetic coupling and an optimal force between the impeller and driver is necessary to develop an atraumatic centrifugal pump.

[1]  H. Harasaki,et al.  Hemolysis. A comparative study of four nonpulsatile pumps. , 1988, ASAIO transactions.

[2]  J. Stuckey,et al.  Studies of Plasma Hemoglobin Formation in three Pumping Systems Used in Extracorporeal Circulation , 1962, Annals of surgery.

[3]  Y Nosé,et al.  The need for standardizing the index of hemolysis. , 1994, Artificial organs.

[4]  D B Olsen,et al.  In vitro hematological testing of rotary blood pumps: remarks on standardization and data interpretation. , 2008, Artificial organs.

[5]  J. Schuder,et al.  The use of a totally occlusive pump as a flowmeter with observations on hemolysis caused by occlusive and nonocclusive pumps and other pump-oxygenator components. , 1958, Surgery.

[6]  Y Nosé,et al.  The next generation Baylor C-Gyro Pump: antithrombogenic "free impeller" design for long-term centrifugal VAD. , 1994, Artificial organs.

[7]  G Damm,et al.  An ultimate, compact, seal-less centrifugal ventricular assist device: Baylor C-Gyro pump. , 1994, Artificial organs.

[8]  Y Nosé,et al.  Development and evaluation of antithrombogenic centrifugal pump: the Baylor C-Gyro Pump Eccentric Inlet Port Model. , 1994, Artificial organs.

[9]  L. Caprino,et al.  A Native whole Blood Test for the Evaluation of Blood-surface Interaction: Determination of Thromboxane Production , 1984, The International journal of artificial organs.

[10]  T Koller,et al.  Contribution to the in vitro testing of pumps for extracorporeal circulation. , 1967, The Journal of thoracic and cardiovascular surgery.

[11]  G Damm,et al.  Initial clinical experience with the Baylor-Nikkiso centrifugal pump. , 1995, Artificial organs.

[12]  Y Ohara,et al.  Does hematocrit affect in vitro hemolysis test results? Preliminary study with Baylor/NASA prototype axial flow pump. , 1994, Artificial organs.

[13]  R Yozu,et al.  A miniaturized centrifugal pump for assist circulation. , 1994, Artificial organs.