Office of Technology Transfer – University of Michigan

A New Method for Determining Hemodialysis Access Blood Flow Using Intradialytic Access Doppler Ultrasound and Variable Dialysis Blood Pump Flow Rates

Technology #1506

UM File # 1506

Background
Hemodialysis patients often have an arteriovenous shunt, or access, surgically created between an artery and vein in a location in the body. While this access provides a convenient connection, its malfunction is a frequent occurrence; in particular, unpredictable thrombosis and stenosis in causes a reduction in blood flow, which, if untreated, can cause undesired recirculation. Current techniques to evaluate flow in access uses duplex ultrasonography, whereby blood flow is calculated using the time-velocity integral of a spectrum obtained from a representative area of the access. However, Doppler ultrasound techniques depend on the cross-sectional area measured by imaging, which may often be inaccurate. In addition, the procedure is labor intensive and expensive, such that measurements are not usually made with high enough frequency to effectively monitor the onset of reduced access flow.
Technology Description
Researchers at the University of Michigan have developed a system and method for accurately measuring blood flow rate in a vessel without relying on a measurement of vessel cross-sectional area. In this system, a conduit is in communication with the vessel, and has an inlet for diverting blood from the vessel into the conduit. Disposed within the conduit is a pump for diverging blood out of the vessel a certain pump flow rate. An ultrasonic sensor in communication with the vessel generates at least one Doppler frequency signal correlated with a blood flow rate in the vessel downstream from the inlet, wherein the flow rate depends on the known pump flow rate and an unknown blood flow rate in the vessel upstream from the inlet. A processor is provided in communication with the ultrasonic sensor and the pump for determining the upstream flow rate from the signal and the pump flow rate.
Applications • Blood flow measurements in hemodialysis access
Advantages • Simple, safe, and efficient • Does not require magnitude of the cross-sectional area of access to determine the flow.