Optical sensor and method for detecting a patient condition

• US 8,165,676 B2
• Filed: 12/21/2007
• Issued: 04/24/2012
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Donofrio, William T.
• Primary Examiner(s): Patel, Niketa
• Assistant Examiner(s): Holmes, Rex R
• Application Number:
  US11/962,745
• Publication Number:
  US 20090163968A1
• Time in Patent Office: 1,586 Days
• Field of Search: 607/6, 607/3, 607 17- 22, 600310-333, 600/542, 600/544, 600500-502, 600/301
• US Class Current: 607/19
• CPC Class Codes: A61B 2562/0233 Special features of optical sensors or probes classified in A61B5/00
• CPC Class Codes: A61B 2562/043 in a linear array
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/14556 by fluorescence A61B5/14555 takes precedence
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: A61B 5/6846 specially adapted to be brought in contact with an internal body part, i.e. invasive
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/36557 controlled by chemical substances in blood
• CPC Class Codes: A61N 1/36571 controlled by blood flow rate, e.g. blood velocity or cardiac output
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

An implantable medical device for monitoring tissue perfusion that includes a light source emitting light having a light wavelength corresponding to a blue to ultraviolet light spectrum and a light detector receiving light emitted by the light source and scattered by a volume of body tissue. The light detector emits a signal correlated to the received light wavelength, and a processor receives the signal from the light detector and determines a patient condition in response to the signal.

Claims

1. An implantable medical device, comprising:

a light source emitting light comprising a first light wavelength corresponding to a blue to ultraviolet light spectrum and a second wavelength corresponding to a red to infrared light spectrum;

a light detector receiving light emitted by the light source and scattered by a volume of body tissue, the light detector emitting a first signal correlated to the received light having the first light wavelength and a second signal correlated to the received light having the second wavelength;

a processor configured to;

receive the first signal and the second signal from the light detector;

determine a divergence between the first signal and the second signal; and

determine patient condition in response to the divergence; and

further comprising an electrode for sensing cardiac electrical signals, wherein the processor receives the cardiac electrical signals and detects a heart rhythm in response to the cardiac electrical signals, and wherein the processor determines the patient condition further based at least in part, on the heart rhythm.

2. The device of claim 1, further comprising:

a therapy delivery module; and

a control module coupled to the processor and the therapy delivery module, the control module causing the therapy delivery module to deliver a therapy in response to the determined patient condition, wherein the patient condition is ventricular fibrillation and the therapy is a defibrillation therapy.

3. The device of claim 1 wherein the light source comprises a white light source.

4. The device of claim 3 further comprising a filter passing the first light wavelength to the light detector.

5. The device of claim 4 wherein the filter filters the emitted light.

6. The device of claim 4 wherein the filter filters the light received by the light detector after being scattered by the body tissue volume.

7. The device of claim 3 wherein the filter comprises a lens through which one of the emitted light and the received light passes.

8. The device of claim 1 wherein the light detector detects fluorescence of the body tissue in response to the first light wavelength corresponding to ultraviolet light.

9. The device of claim 2 wherein the processor determines the patient condition at predetermined time intervals subsequent to detecting the heart rhythm.

10. The device of claim 9 wherein determining the patient condition further comprises comparing the determined patient condition to a time-dependent threshold and wherein the patient control module causes the therapy delivery module to deliver a therapy in response to the determined patient condition reaching a time-dependent threshold.

11. An implantable medical device, comprising:

an electrode sensing a cardiac electrical signal;

a light source emitting light comprising a first light wavelength corresponding to a blue to ultraviolet light spectrum and a second light wavelength corresponding to a red to infrared light spectrum;

a light detector receiving light emitted by the light source, the light detector comprising a first filtered photodetector selectively detecting light corresponding to the first light wavelength and a second filtered photodetector selectively detecting light corresponding to the second light wavelength, the light detector emitting a first signal correlated to the received light having the first light wavelength and a second signal correlated to the received light having the second light wavelength;

a processor receiving the cardiac electrical signal, detecting an arrhythmia in response to the cardiac electrical signal, receiving the first signal and the second signal from the light detector, determining a divergence between the first light signal and the second light signal at predetermined time intervals following detecting the arrhythmia, comparing the divergence to a predetermined time-dependent threshold, and confirming the arrhythmia in response to the comparison; and

a therapy control module coupled to the processor and delivering an anti-arrhythmia therapy in response to the arrhythmia confirmation.

12. A method for monitoring a physiological condition for use in an implantable medical device, comprising:

emitting light comprising a first light wavelength corresponding to a blue to ultraviolet light spectrum from a light source;

detecting light having the first light wavelength and scattered by a volume of body tissue, and emitting a first signal correlated to the detected light having the first light wavelength;

emitting a second light wavelength corresponding to a red to infrared light spectrum;

detecting light comprising the second light wavelength and scattered by the body tissue volume, and emitting a second signal correlated to the detected light comprising the second light wavelength;

determining a patient condition in response to the first signal and the second signal by determining a divergence between the first signal and the second signal sensing cardiac electrical signals; and

detecting a heart rhythm in response to the sensed cardiac electrical signals;

wherein the determining the patient condition step is further based, at least in part, on the heart rhythm.

13. The method of claim 12 further comprising filtering one of the emitted light and the detected light.

14. The method of claim 12 wherein the first light wavelength corresponds to ultraviolet light and detecting the first light wavelength comprises detecting fluorescence of the body tissue volume.

15. The method of claim 12 wherein the processor determines the patient condition at predetermined time intervals subsequent to detecting the heart rhythm.

16. The method of claim 15 wherein determining the patient condition further comprises comparing the determined patient condition to a time-dependent threshold.