CONTROL OF CENTRIFUGAL BLOOD PUMP BASED ON THE MOTOR CURRENT

In this study, centrifugal pump performance was examined in a mock cir culatory loop to derive an automatic pump rotational speed (rpm) contr ol method. The pivot bearing supported sealless centrifugal pump was p laced in the left ventricular apex to aorta bypass mode. The pneumatic pulsatile ventricle was used to simulate the natural ventricle. To si mulate the suction effect in the ventricle, a collapsible rubber tube was placed in the inflow port of the centrifugal pump in series with t he apex of the simulated ventricle. Experimentally, the centrifugal pu mp speed (rpm) was gradually increased to simulate the suction effect. The pump flow through the centrifugal pump measured by an electromagn etic flowmeter, the aortic pressure, and the motor current were contin uously digitized at 100 Hz and stored in a personal computer. The anal ysis of the cross-spectral density between the pump flow and motor cur rent waveforms revealed that 2 waveforms were highly correlated at the frequency range between 0 and 4 Hz, with the coherence and phase angl es being close to 1.0 and 0 degrees, respectively. The fast Fourier tr ansform analysis of the motor current indicated that the second harmon ic component of the motor current power density increased with the occ urrence of the suction effect in the circuit. The ratio of the fundame ntal to the second harmonic component decreased less than 1.3 as the s uction effect developed in the circuit. It is possible to detect and p revent the suction effect of the centrifugal blood pump in the natural ventricle through analysis of the motor current waveform.