USE OF MOTOR CURRENT IN FLOW-RATE MEASUREMENT FOR THE MAGNETICALLY SUSPENDED CENTRIFUGAL BLOOD PUMP

Indirect measurement of the flow rate of a centrifugal blood pump usin g the driving motor current was studied. The pump flow rate can be exp ressed as a function of the motor current under a given motor speed in the absence of energy loss resulting from uncertain mechanical contac t friction. The magnetically suspended centrifugal blood pump (MSCP), developed by the collaboration of Kyoto University and NTN Inc., was s uitable for the application of this measuring method because the impel ler is suspended magnetically inside the pump housing without any mech anical contact. The effect of fluid viscosity on the pump performance was investigated in detail, and it was possible to estimate the pump f low rate and the pressure difference through the pump (from inlet port to outlet port) accurately by monitoring the motor current and speed when the kinematic viscosity of working fluids was known. The kinemati c viscosity of working fluids can also be measured with the MSCP. The motor current and motor speed were monitored in a chronic animal exper iment, and the estimated flow rate and pressure difference showed good correlation with directly measured data.