Detection of suction and regurgitation of the implantable centrifugal pumpbased on the motor current waveform analysis and its application to optimization of pump flow

In this study, a detection algorithm for suction and regurgitation of the c entrifugal pump during left heart bypass without relying on external flow o r pressure sensors was developed and evaluated in acute studies using adult goats. The detection scheme relies on power spectral density (PSD) analysi s of the motor current waveform through which the waveform deformation inde x (WDI) is obtained. This index is defined as the ratio of the fundamental component of the PSD to the higher PSD components, and its value increases with the deformation of the basic waveform. By assuming that the undistorte d motor current waveform can be represented by a pure sine waveform, we the oretically synthesized various waveforms which have different second harmon ic components. We were able to synthesize the waveform whose shape was clos e to the distorted motor current waveform under varying suction levels obta ined in a mock loop study. From this study, we came to the conclusion that the WDI value of 0.2 can serve as a threshold level in deciding the suction and regurgitation speeds (rpm) during left heart bypass. In the study usin g adult goats, we were successful in minimizing both regurgitation and suct ion when the centrifugal pump speed was adjusted based on the WDI algorithm . The resultant bypass flow ranged from 1.5 to 2.0 L/min which was around 6 0% of the total flow. Further study is underway to evaluate the applicabili ty of the WDI method in optimizing bypass pump flow.