US 2002/0002335 A1 · Blood flow meter apparatus and method of use

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.

Claims46

Dependent claims

A method of estimating blood flow in a vessel over a period of time by using measurement circuits, the method comprising the steps of:

(a) using the measurement circuits to obtain a sequence of blood flow estimates providing samples used to reconstruct a blood flow waveform indicative of blood flow, wherein more than one sample is required to reconstruct the blood flow waveform;
and
(b) automatically deactivating at least part of the measurement circuits during at least part of the time an estimate is not being obtained.

An apparatus for obtaining a Doppler-shifted ultrasonic energy signal for repeatedly estimating blood flow, the apparatus comprising:

a control circuit that repeatedly provides an electrical strobed ultrasonic-frequency signal containing ultrasonic-frequency components during an active period that is of sufficient duration to obtain a blood flow estimate, and contains substantially no ultrasonic-frequency components during an idle period between the active period and a subsequent active period;
an amplifier having an amplifier input, which is electrically coupled to the control circuit for receiving the strobed ultrasonic-frequency signal, and an amplifier output providing an electrical strobed amplified ultrasonic-frequency signal in response thereto;
an ultrasound transducer having a transducer electrical input, which is electrically coupled to the amplifier output for receiving the amplified ultrasonic-frequency signal, and having a transducer ultrasound output, for providing strobed ultrasonic energy to the blood vessel in response to the amplified ultrasonic-frequency signal, and having a transducer ultrasound input, for receiving a reflected Doppler-shifted ultrasonic energy signal from the blood vessel, and having a transducer electrical output, for providing an electrical received Doppler-shifted signal in response thereto;
and
a receiver having a receiver input electrically coupled to the transducer electrical output for receiving the received Doppler-shifted signal and having a receiver output for providing a buffered Doppler-shifted signal in response thereto.

2 more elements

Dependencies are inferred from the claim text.

Blood flow meter apparatus and method of use

Life of this patent

Blood flow meter apparatus and method of use

Life of this patent

Abstract

Claims46