Patent Number: 6,167,765

Title: System and method for determining the flow rate of blood in a vessel using doppler frequency signals

Abstract: A system and method are provided for determining the flow rate of blood in a vessel, such as a hemodialysis access. The system includes a conduit, such as an external dialysis circuit or an intravascular catheter, in communication with the blood in the vessel and having a diversion point for diverting the blood from the vessel into the conduit. As such, the vessel has a flow rate (Q.sub.A) upstream from the diversion point and a flow rate (Q.sub.D) downstream from the diversion point. A pump is connected to the conduit for diverting the blood into the conduit using a pump flow rate. An ultrasonic sensor is provided in communication with the blood in the vessel downstream from the diversion point. The ultrasonic sensor senses the downstream flow rate (Q.sub.D) and generates at least two downstream Doppler frequency signals including a first downstream Doppler frequency signal when the pump has a first pump flow rate and a second downstream Doppler frequency signal when the pump has a second pump flow rate. A processor connected to the ultrasonic sensor and the pump then determines the upstream flow rate (Q.sub.A) when the pump has a selected pump flow rate from the first and second downstream Doppler frequency signals and the selected pump flow rate.

Inventors: Weitzel; William F. (Ypsilanti, MI)

Assignee: The Regents of the University of Michigan

International Classification: A61M 1/36 (20060101); G01F 001/20 ()

Expiration Date: 01/02/2018