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.