VIBRATION ASSESSMENT FOR THROMBUS FORMATION IN THE CENTRIFUGAL PUMP

To clarify the correlation of vibration and thrombus formation inside a rotary blood pump, 40 preliminary vibration studies were performed o n pivot bearing centrifugal pumps. No such studies were found in the l iterature. The primary data acquisition equipment included an accelero meter (Isotron PE accelerometer, ENDEVCO, San Juan Capistrano, CA, U.S .A.), digitizing oscilloscope (TDS 420, Tektronix Inc., Pittsfield, MA , U.S.A.), and pivot bearing centrifugal pumps. The pump impeller was coupled magnetically to the driver magnet. The accelerometer was mount ed on the top of the pump casing to sense radial and axial acceleratio ns. To simulate the 3 common areas of thrombus formation, a piece of s ilicone rubber was attached to each of the following 3 locations as de scribed: a circular shape on the center bottom of the impeller (CI), a n eccentric shape on the bottom of the impeller (EI), and a circular s hape on the center bottom casing (CC). A fast Fourier transform (FFT) method at 5 L/min against 100 mm Hg, with a pump rotating speed of 1,6 00 rpm was used. The frequency response of the vibration sensors used spans of 40 Hz to 2 kHz. The frequency domain was already integrated i nto the oscilloscope, allowing for comparison of the vibration results . The area of frequency domain at a radial direction was 206 +/- 12.7 mVHz in CI, 239.5 +/- 12.1 mVHz in EI, 365 +/- 12.9 mVHz in CC, and 16 3 +/- 7.9 mVHz in the control (control vs. CI p = 0.07, control vs. EI p < 0.001, control vs. CC p < 0.001, EI vs. CC p < 0.001, CI vs. CC p < 0.001). Three types of imitation thrombus formations were roughly d istinguishable. These results suggested the possibility of detecting t hrombus formation using vibration signals, and these studies revealed the usefulness of vibration monitoring to detect thrombus formation in a centrifugal pump.