Blood flow meter apparatus and method of use

• US 6,544,180 B1
• Filed: 11/30/1999
• Issued: 04/08/2003
• Est. Priority Date: 11/07/1996
• Status: Expired due to Fees

• Current Assignee: Data Sciences U K Limited (International Business Machines Corporation)
• Original Assignee: Data Sciences U K Limited (International Business Machines Corporation)
• Inventors: Brockway, Brian P., Doten, Gregory P.
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): PATEL, MAULIN M
• Application Number:
  US09/452,332
• Time in Patent Office: 1,225 Days
• Field of Search: 600/443, 600/447, 600/448, 600/437, 600/453, 600/457
• US Class Current: 600/448
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/12 in body cavities or body tracts, e.g. by using catheters catheters per se A61M25/00

Abstract

A strobed blood flow meter provides periodic measurements of blood flow velocity or volumetric blood flow over a cardiac cycle at reduced average power consumption, which is advantageous for reducing battery size, and extending device battery life, such as in an implantable application. Continuous wave Doppler, pulsed Doppler, laser Doppler, transit time, electromagnetic flow, and thermal dilution techniques are included. Strobing provides higher level excitation during active periods, which improves signal-to-noise ratio, and provides a low power standby mode during an idle time between active periods. The invention may be used for chronic or acute applications. Doppler or other signals may be telemetered from an implanted portion of the flow meter for further signal processing to extract velocity or volumetric flow. Alternatively, such signal processing is also implanted, such that the velocity signal can be telemetered to an remote monitor.

Claims

1. An apparatus for repeatedly estimating fluid flow in a conduit, the apparatus comprising:

one or more monitoring devices; and

a source of electrical excitation signal that is applied to at least one of the one or more monitoring devices for at least a portion of an active period of a strobing control signal sufficient to obtain a fluid flow estimate and is removed from the at least one of the one or more monitoring devices for at least a portion of an idle period of the strobing control signal until a subsequent fluid flow estimate is to be obtained.

2. The apparatus of claim 1, further comprising a source of one or more power control signals applied to the source of the excitation signal such that the source of the excitation signal is reduced for at least a portion of the idle period.

3. The apparatus of claim 1, further comprising an implantable housing containing the source of the electrical excitation signal.

4. The apparatus of claim 3, further comprising a telemetry device, contained within the housing, for transmitting from the apparatus one or more signals containing information indicative of the fluid flow estimate.

5. The apparatus of claim 4, further comprising a source of one or more power control signals applied to the telemetry device such that the telemetry device is powered down or off when not transmitting signals from the implantable apparatus.

6. The apparatus of claim 1, wherein the monitoring devices comprise monitoring devices for transit time flow measurement.

7. The apparatus of claim 1, wherein the monitoring devices comprise monitoring devices for laser Doppler time flow measurement.

8. The apparatus of claim 1, wherein the monitoring devices comprise monitoring devices for electromagnetic flow measurement.

9. The apparatus of claim 1, wherein the monitoring devices comprise monitoring devices for thermal dilution flow measurement.

10. An apparatus for obtaining a time-shifted ultrasonic energy signal for repeatedly estimating fluid flow, the apparatus comprising:

a control circuit that provides a first and second electrical ultrasonic-frequency signals containing ultrasonic-frequency components during an active period of a control signal that is of sufficient duration to obtain a fluid flow estimate, and contain substantially no ultrasonic-frequency components during at least a portion of an idle period of the control signal between the active period and a subsequent active period;

a first amplifier having an amplifier input, which is electrically coupled to the control circuit for receiving the first ultrasonic-frequency signal, and an amplifier output providing a first electrical amplified ultrasonic-frequency signal in response thereto;

a second amplifier having an amplifier input, which is electrically coupled to the control circuit for receiving the second ultrasonic-frequency signal, and an amplifier output providing a second electrical amplified ultrasonic-frequency signal in response thereto;

a first transducer having a transducer electrical input, which is electrically coupled to the amplifier output of the first amplifier for receiving the first amplified ultrasonic-frequency signal, and having a transducer ultrasound output, for providing a first ultrasonic-frequency signal to the conduit in response to the first amplified ultrasonic-frequency signal, and having a transducer ultrasound input, for receiving a second time-shifted ultrasonic-frequency signal from the conduit, and having a transducer electrical output, for providing a second electrical received time-shifted signal in response thereto;

a second transducer having a transducer electrical input, which is electrically coupled to the amplifier output of the second amplifier for receiving the second amplified ultrasonic-frequency signal, and having a transducer ultrasound output, for providing a second ultrasonic-frequency signal to the conduit in response to the second amplified ultrasonic-frequency signal, and having a transducer ultrasound input, for receiving a first time-shifted ultrasonic-frequency signal from the conduit, and having a transducer electrical output, for providing a first electrical received time-shifted signal in response thereto;

a first receiver having a receiver input electrically coupled to the first transducer electrical output for receiving the second electrical received time-shifted signal and having a receiver output for providing a first buffered time-shifted signal in response thereto; and

a second receiver having a receiver input electrically coupled to the second transducer electrical output for receiving the first electrical received time-shifted signal and having a receiver output for providing a second buffered time-shifted signal in response thereto.

11. The apparatus of claim 10, wherein the first ultrasound transducer comprises:

a first transmit transducer, which is electrically coupled to the amplifier output of the first amplifier for receiving the first amplified ultrasonic-frequency signal and providing the first ultrasonic-frequency signal to the conduit in response thereto; and

a first receive transducer, for receiving the second time-shifted ultrasonic-frequency signal from the conduit and providing the second electrical received time-shifted signal in response thereto, and wherein the second ultrasound transducer comprises;

a second transmit transducer, which is electrically coupled to the amplifier output of the second, amplifier for receiving the second amplified ultrasonic-frequency signal and providing the second, ultrasonic-frequency signal to the conduit in response thereto; and

a second receive transducer, for receiving the first time-shifted ultrasonic-frequency signal from the conduit and providing the first electrical received time-shifted signal in response thereto.

12. The apparatus of claim 10, further comprising a processing circuit for receiving the first and second buffered time-shifted signals and providing a flow signal in response thereto.

13. The apparatus of claim 12, further comprising a telemetry circuit coupled to the processing circuit for receiving, and transmitting therefrom, the flow signal.

14. The apparatus of claim 13, further comprising a remote telemetry device that is wirelessly coupled to the telemetry circuit for receiving the flow signal that is transmitted therefrom.

15. The apparatus of claim 10, further comprising a reflector, wherein the reflector receives the first ultrasonic-frequency signal from the first transducer, through the conduit, and sends the first ultrasonic-frequency signal to the second transducer, through the conduit, and further wherein the reflector receives the second ultrasonic-frequency signal from the second transducer, through the conduit, and sends the second ultrasonic-frequency signal to the first transducer.

16. The apparatus of claim 15, wherein the reflector is an acoustic reflector.

17. The apparatus of claim 15, further comprising a processing circuit for receiving the first and second buffered time-shifted signals and providing a flow signal in response thereto.

18. The apparatus of claim 17, further comprising a telemetry circuit coupled to the processing circuit for receiving, and transmitting therefrom, the flow signal.

19. The apparatus of claim 18, further comprising a remote telemetry device that is wirelessly coupled to the telemetry circuit for receiving the flow signal that is transmitted therefrom.

20. The apparatus of claim 10, further comprising an impedance matching network series-connected between the amplifier and the transducer for improving power transfer therebetween.

21. The apparatus of claim 10, wherein the first ultrasonic-frequency signal has a directional component in the same direction as the fluid flow in the conduit and wherein the second ultrasonic-frequency signal has a directional component in the opposite direction as the fluid flow in the conduit.

22. An apparatus for repeatedly estimating fluid flow in a conduit, the apparatus comprising:

one or more monitoring devices;

a source of electrical excitation signal that is applied to at least one of the one or more monitoring devices for at least a portion of an active period of a control signal sufficient to obtain a fluid flow estimate and is removed from the at least one of the one or more monitoring devices for at least a portion of an idle period of the control signal until a subsequent fluid flow estimate is to be obtained; and

an implantable housing containing the source of the electrical excitation signal.

23. The apparatus of claim 22, further comprising a telemetry device, contained within the housing, for transmitting from the apparatus one or more signals containing information indicative of the fluid flow estimate.

24. The apparatus of claim 23, further comprising a source of one or more power control signals applied to the telemetry device such that the telemetry device is powered down or off when not transmitting signals from the implantable apparatus.

25. An apparatus for repeatedly estimating fluid flow in a conduit, the apparatus comprising:

one or more monitoring devices, wherein the monitoring devices comprise monitoring devices for electromagnetic flow measurement; and

a source of electrical excitation signal that is applied to at least one of the one or more monitoring devices for at least a portion of an active period of a control signal sufficient to obtain a fluid flow estimate and is removed from the at least one of the one or more monitoring devices for at least a portion of an idle period of the control signal until a subsequent fluid flow estimate is to be obtained.

26. An apparatus for repeatedly estimating fluid flow in a conduit, the apparatus comprising:

one or more monitoring devices, wherein the monitoring devices comprise monitoring devices for thermal dilution flow measurement; and

a source of electrical excitation signal that is applied to at least one of the one or more monitoring devices for at least a portion of an active period of a control signal sufficient to obtain a fluid flow estimate and is removed from the at least one of the one or more monitoring devices for at least a portion of an idle period of the control signal until a subsequent fluid flow estimate is to be obtained.