Quantifying laser-doppler perfusion signal for arrhythmia detection and disease monitoring

• US 9,031,641 B2
• Filed: 07/28/2011
• Issued: 05/12/2015
• Est. Priority Date: 07/28/2011
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Rajan, Vinayakrishnan, Schneider, Raphael Alexander
• Primary Examiner(s): Le, Long V
• Assistant Examiner(s): IMPINK, BRADLEY GERALD
• Application Number:
  US13/193,059
• Publication Number:
  US 20130030307A1
• Time in Patent Office: 1,384 Days
• Field of Search: None
• US Class Current: 600/479
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2560/0252 using ambient temperature
• CPC Class Codes: A61B 5/0024 for multiple sensor units attached to the patient, e.g. using a body or personal area network
• CPC Class Codes: A61B 5/0075 by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy A61B5/0071 takes precedence
• CPC Class Codes: A61B 5/02055 Simultaneously evaluating both cardiovascular condition and temperature
• CPC Class Codes: A61B 5/02233 Occluders specially adapted therefor tourniquets A61B17/132
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61B 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61N 1/36571 controlled by blood flow rate, e.g. blood velocity or cardiac output
• CPC Class Codes: A61N 1/37211 Means for communicating with stimulators
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

A medical device system and associated method to control a laser Doppler unit to emit light from a coherent laser light source and collect a photodetector signal produced by the laser Doppler unit by a signal processor comprising a bandpass filter. The bandpass filter is applied to the photodetector signal to determine a tissue perfusion measurement from the filtered signal. A monitoring unit is enabled to receive the tissue perfusion measurement to detect a physiological condition of the patient in response to the tissue perfusion measurement.

Claims

1. A medical device system for monitoring tissue perfusion in a patient, comprising:

a laser Doppler unit comprising a coherent laser light source and a photodetector;

a signal processor comprising a plurality of bandpass filters each having a distinct center frequency and bandwidth, wherein the signal processor is configured to receive a signal from the photodetector, apply the bandpass filters to the photodetector signal, and select a first passband signal output from a first one of the plurality of filters to determine a tissue perfusion measurement from the filtered signal;

and a monitoring unit configured to receive the tissue perfusion measurement and to detect a physiological condition of the patient in response to the tissue perfusion measurement.

2. The system of claim 1, wherein the monitoring unit is further configured to transmit a request signal, and wherein the laser Doppler unit and the signal processor are configured to cooperatively perform tissue perfusion monitoring and determine the tissue perfusion measurement responsive to the request signal and transmit the tissue perfusion measurement to the monitoring unit.

3. The system of claim 2, wherein the tissue perfusion measurement comprises a sampled magnitude of to the first passband signal output.

4. The system of claim 1, wherein the monitoring unit is further configured to transmit a request signal, wherein the request signal establishes a passband selection and the signal processor selects the first passband signal in response to the request signal.

5. The system of claim 4, wherein the monitoring unit comprises a first unit for detecting a first condition and a second unit for detecting a second condition different than the first condition, and wherein the first monitoring unit is configured to transmit a request signal establishing a first passband selection corresponding to a tissue perfusion measurement for detecting the first condition, and the second monitoring unit is configured to transmit a request signal establishing a second passband selection different than the first passband selection and corresponding to a tissue perfusion measurement for detecting the second condition.

6. The system of claim 1, wherein the signal processor is further configured to select a second passband signal and determine the tissue perfusion measurement using both the first and the second passband signal.

7. The system of claim 1, wherein the processor is further configured to select a passband selection established by a user, and further comprising a programmable memory for storing the selected established passband.

8. The system of claim 1, wherein the processor is further configured to determine unacceptable signal quality of the first passband signal and select a second passband signal for determining the tissue perfusion measurement in response to determining the unacceptable signal quality.

9. The system of claim 1, wherein the monitoring unit is configured to detect a first state of the physiological condition using a first threshold established for the perfusion measurement and detect a second state of the physiological condition using a second threshold established for the perfusion measurement, the second threshold different than the first threshold.

10. A method for monitoring a patient using a medical device system comprising a laser Doppler unit, the method comprising:

controlling the laser Doppler unit to emit light from a coherent laser light source;

collecting a photodetector signal produced by the laser Doppler unit using a signal processor comprising a plurality of bandpass filters each having a distinct center frequency and bandwidth;

applying the bandpass filters to the photodetector signal and selecting a first passband signal output from a first one of the plurality of filters to determine a tissue perfusion measurement from the filtered signal;

and enabling a monitoring unit to receive the tissue perfusion measurement and detect a physiological condition of the patient in response to the tissue perfusion measurement.

11. The method of claim 10, further comprising:

transmitting a request signal; and

responsive to the transmitted request signal, controlling the laser Doppler unit and the signal processor to cooperatively perform tissue perfusion monitoring and determine the tissue perfusion measurement and transmit the tissue perfusion measurement to the monitoring unit.

12. The method of claim 11, wherein determining the tissue perfusion measurement comprises sampling a magnitude of the first passband signal output.

13. The method of claim 10, further comprising:

transmitting a request signal, wherein the request signal establishes a passband selection; and

selecting the first passband signal in response to the request signal.

14. The method of claim 13, further comprising:

detecting a first condition and a second condition different than the first condition;

transmitting a request signal establishing a first passband selection corresponding to a tissue perfusion measurement for detecting the first condition; and

transmitting a request signal establishing a second passband selection different than the first passband selection and corresponding to a tissue perfusion measurement for detecting the second condition.

15. The method of claim 10, further comprising:

selecting a second passband signal; and

determining the tissue perfusion measurement using both the first and the second passband signal.

16. The method of claim 10, further comprising:

storing a passband selection established by a user; and

selecting the established passband.

17. The method of claim 10, further comprising:

determining an unacceptable signal quality of the first passband signal;

selecting a second passband signal in response to determining the unacceptable signal quality; and

determining the tissue perfusion measurement in response to the second passband signal.

18. The method of claim 10, further comprising:

detecting a first state of the physiological condition using a first threshold established for the perfusion measurement; and

detecting a second state of the physiological condition using a second threshold established for the perfusion measurement, the second threshold different than the first threshold.

19. A non-transitory computer-readable medium storing a set of instructions which cause a medical device system comprising a laser Doppler unit to perform a method comprising:

controlling the laser Doppler unit to emit light from a coherent laser light source;

collecting a photodetector signal produced by the laser Doppler unit using a signal processor comprising a plurality of bandpass filters each having a distinct center frequency and bandwidth;

applying the bandpass filters to the photodetector signal;

selecting a first passband signal output from a first one of the plurality of filters to determine a tissue perfusion measurement from the filtered signal;

and enabling a monitoring unit to receive the tissue perfusion measurement and detect a physiological condition of the patient in response to the tissue perfusion measurement.