A - Human Necessities – 61 – B
Patent
A - Human Necessities
61
B
349/39
A61B 8/06 (2006.01) G01F 1/66 (2006.01)
Patent
CA 2007164
43932CAN9A ABSTRACT OF THE DISCLOSURE A Doppler blood flow system and method in which an ultrasonic wave is reflected off of red blood cells in blood flowing in tubing. The reflected ultrasonic wave is digitally processed in the frequency domain. The flow rate of the blood is directly related to the average frequency of the Doppler signal. Because the Doppler blood flow system calculates flow rate solely on the basis of frequency, a special case exists at zero rate of flow where the received signal is not a valid Doppler flow signal, but rather purely noise. The noise at zero flow rate is random and will not have an average frequency which is unique to zero flow. The Doppler blood flow system and method must invoke a special case determination of when a zero flow condition in order to accurately provide a blood flow rate. The system utilizes a method of determining the rate of flow of a fluid containing particles flowing through a tube. An ultrasonic signal is transmitted through the tube at an oblique angle thereto. The ultrasonic signal which has been reflected off of the particles contained in the fluid is received as a received ultrasonic signal. The rate of flow of the fluid is calculated from the received ultrasonic signal using Doppler techniques. Whether the special case of the value of the rate of flow being equal to zero exists is determined and the value of the rate of flow is set equal to zero for the special case. 43932CAN9A DOPPLER BLOOD FLOW SYSTEM AND METHOD USING SPECIAL ZERO FLOW RATE ANALYSIS Technical Field The present invention relates generally to Doppler blood flow measurement systems and techniques, and more particularly to Doppler blood flow measurement systems and techniques using the frequency domain signal analysis. Background Art During cardiopulmonary bypass surgery, ventricular assist using blood pumps and other cardiac surgeries, blood flow external to the patient is necessary. Known blood pumps and so-called heart-lung machines operate to transport the blood of the patient through tubing or conduits in order to perform their function. During the transportation of blood in these external (to the body of the patient) tubes or conduits, it is extremely important for the surgeon to monitor the rate of flow of the blood so that abnormalities in the flow can be detected and corrective action can be taken. Various systems and techniques have been utilized to measure the flow of blood, or other fluids, through tubes or conduits in the past.
Smith Dirk R.
Weaver Billy L.
Minnesota Mining And Manufacturing Company
Smart & Biggar
Smith Dirk R.
Weaver Billy L.
LandOfFree
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