Flow measurement system
AssigneeMinnesota Mining and Manufacturing Company
InventorsLloyd C. Hubbard, Earl W. Clausen
Life of this patent
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Abstract
Blood flow rate in a motor driven centrifugal blood pump is measured indirectly and non-invasively by sensing a first parameter representative of pump RPM and a second parameter representative of motor torque. The blood flow rate is computed as a function of the first and second parameters. By measuring the second parameter in a zero flow condition while the motor is being driven at a known RPM, a viscosity calibration factor is determined which is used, together with the first and second parameters in the calculation of flow rate.
Claims7
A method of indirectly and noninvasively measuring blood flow in an outlet line connected to a motor driven centrifugal blood pump of a type having an inlet, and outlet connected to the outlet line, a housing, and an impeller which is rotated by the motor to pump blood from the inlet to the outlet, the method comprising:
- sensing a first parameter to provide a first signal representative of pump impeller RPM;
- sensing a second parameter to provide a second signal representative of motor torque;
- computing a blood flow rate in the outlet line as a function of the first and second signals;
- and
- displaying a representation of the blood flow in the outlet line.
A method of indirectly and noninvasively measuring blood flow from a motor driven centrifugal blood pump, the method comprising:
- sensing a first parameter to provide a first signal representative of pump RPM;
- sensing a second parameter to provide a second signal representative of motor torque;
- causing the pump to operate at a selected RPM;
- clamping an outlet line from the pump to reduce blood flow to zero;
- sensing the second parameter while the blood flow is zero and the pump is operating;
- computing a viscosity factor representative of viscosity of the blood based upon the second signal as produced while the blood flow is zero and the pump is operating;
- and
- computing a blood flow rate as a function of the first and second signals and the viscosity factor.
In a centrifugal blood pump system which includes a centrifugal blood pump having an inlet, an outlet, a housing and an impeller;
- a motor which causes the impeller to rotate;
- and means for controlling the motor to produce a selected RPM of the impeller;
- the improvement comprising:
- means for producing a first signal representative of RPM;
- means for producing second signal representative of motor torque;
- means for producing a third signal representative of blood flow rate from the outlet as a function of the first and second signals;
- and
- means for displaying a representation of the blood flow rate from the outlet as a function of the third signal.
Dependencies are inferred from the claim text.