METHOD AND APPARATUS FOR POST-SHOCK EVALUATION USING TISSUE OXYGENATION MEASUREMENTS

• US 20110066206A1
• Filed: 07/29/2010
• Published: 03/17/2011
• Est. Priority Date: 09/11/2009
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Kuhn, Jonathan L., Havel, William J., Cinbis, Can, Anderson, David A.
• Granted Patent: US 8,918,171 B2
• Time in Patent Office: Days
• US Class Current: 607/22
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• 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: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence
• CPC Class Codes: A61N 1/36557 controlled by chemical substances in blood
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

A method and device for delivering therapy that includes an electrode to sense cardiac signals and to deliver a therapy, a monitoring module detecting a cardiac event in response to the sensed cardiac signals using first detection criteria, a sensor emitting light and detecting emitted light scattered by a tissue volume adjacent the sensor to generate a corresponding detected light intensity output signal, a control module coupled to the sensor to control light emission of the sensor in response to delivering the therapy, and a controller coupled to the monitoring module, the therapy delivery module and the sensor, the controller configured to determine tissue oxygenation measurements in response to the output signal, determine a tissue oxygenation trend in response to the tissue oxygenation measurements, determine a recovery index in response to the determined tissue oxygenation trend, and control one or both of detecting a cardiac event by the monitoring module and delivery of therapy by the therapy delivery module in response to the determined recovery index.

Claims

1. A method for delivering therapy in a medical device, comprising:

sensing cardiac signals;

detecting a cardiac event in response to the sensed cardiac signals using first detection criteria;

delivering a therapy in response to the detected cardiac event;

controlling light emission of a sensor in response to delivering the therapy;

detecting emitted light scattered by a tissue volume adjacent the sensor to generate a corresponding detected light intensity output signal;

determining tissue oxygenation measurements in response to the output signal;

determining a tissue oxygenation trend in response to the tissue oxygenation measurements;

determining a recovery index in response to the determined tissue oxygenation trend; and

controlling one or both of detecting a cardiac event and delivery of therapy in response to the determined recovery index.

2. The method of claim 1, wherein determining a recovery index comprises:

determining a slope of the tissue oxygenation trend; and

determining a capacity for recovery from the detected cardiac event in response to the determined slope.

3. The method of claim 1, wherein determining a recovery index comprises:

determining a slope of the tissue oxygenation trend;

determining whether the slope is less than a slope threshold; and

determining the detected cardiac event as being a recurring cardiac event in response to the slope being less than the slope threshold.

4. The method of claim 1, wherein controlling one or both of subsequent detecting a cardiac event and delivery of therapy comprises subsequently detecting the cardiac event using second detection criteria different from the first detection criteria.

5. The method of claim 4, wherein detection of the cardiac event occurs within a first time period using the first detection criteria, and within a second time period different from the first time period using the second detection criteria.

6. The method of claim 1, wherein controlling one or both of detecting a cardiac event and delivery of therapy comprises adjusting one or both of event detection parameters and therapy delivery parameters.

7. The method of claim 6, wherein controlling one or both of detecting a cardiac event and delivery of therapy comprises adjusting a monitoring window for determining a time period for subsequent therapy delivery.

8. The method of claim 1, wherein computing a tissue oxygenation measurement comprises:

computing a second derivative of a light attenuation spectrum measured by the sensor; and

computing a measurement of the total hemoglobin volume fraction in response to the second derivative, wherein the determined tissue oxygenation trend corresponds to a trend of the total hemoglobin volume fraction.

9. The method of claim 1, wherein computing a tissue oxygenation measurement comprises:

computing a second derivative of a light attenuation spectrum measured by the sensor; and

computing a measure of tissue oxygen saturation in response to the computed second derivative, wherein the determined tissue oxygenation trend corresponds to a trend of the tissue oxygenation saturation.

10. The method of claim 1, wherein computing a tissue oxygenation measurement further comprises:

computing a second derivative of a light attenuation spectrum measured by the sensor;

computing a measure of tissue oxygen saturation in response to the computed second derivative; and

computing a measurement of the total hemoglobin volume fraction from the second derivative and the computed tissue oxygen saturation, wherein the determined tissue oxygenation trend corresponds to a trend of both the tissue oxygenation saturation and the total hemoglobin volume fraction.

11. A medical device for delivering a therapy, comprising:

an electrode to sense cardiac signals and to deliver a therapy;

a monitoring module detecting a cardiac event in response to the sensed cardiac signals using first detection criteria;

a therapy delivery module coupled to the monitoring module and the electrode to deliver a therapy via the electrode in response to the monitoring module detecting the cardiac event;

a sensor emitting light and detecting emitted light scattered by a tissue volume adjacent the sensor to generate a corresponding detected light intensity output signal;

a control module coupled to the sensor to control light emission of the sensor in response to delivering the therapy; and

a controller coupled to the monitoring module, the therapy delivery module and the sensor, the controller configured to determine tissue oxygenation measurements in response to the output signal, determine a tissue oxygenation trend in response to the tissue oxygenation measurements, determine a recovery index in response to the determined tissue oxygenation trend, and control one or both of detecting a cardiac event by the monitoring module and delivery of therapy by the therapy delivery module in response to the determined recovery index.

12. The device of claim 11, wherein determining a recovery index comprises:

determining a slope of the tissue oxygenation trend; and

determining a capacity for recovery from the detected cardiac event in response to the determined slope.

13. The device of claim 11, wherein determining a recovery index comprises:

determining a slope of the tissue oxygenation trend;

determining whether the slope is less than a slope threshold; and

determining the detected cardiac event as being a recurring cardiac event in response to the slope being less than the slope threshold.

14. The device of claim 11, wherein controlling one or both of subsequent detecting a cardiac event and delivery of therapy comprises subsequently detecting the cardiac event using second detection criteria different from the first detection criteria.

15. The device of claim 14, wherein detection of the cardiac event occurs within a first time period using the first detection criteria, and within a second time period different from the first time period using the second detection criteria.

16. The device of claim 11, wherein controlling one or both of detecting a cardiac event and delivery of therapy comprises adjusting one or both of event detection parameters and therapy delivery parameters.

17. The device of claim 16, wherein controlling one or both of detecting a cardiac event and delivery of therapy comprises adjusting a monitoring window for determining a time period for subsequent therapy delivery.

18. The device of claim 11, wherein computing a tissue oxygenation measurement comprises:

computing a second derivative of a light attenuation spectrum measured by the sensor; and

computing a measurement of the total hemoglobin volume fraction in response to the second derivative, wherein the determined tissue oxygenation trend corresponds to a trend of the total hemoglobin volume fraction.

19. The device of claim 11, wherein computing a tissue oxygenation measurement comprises:

computing a second derivative of a light attenuation spectrum measured by the sensor; and

computing a measure of tissue oxygen saturation in response to the computed second derivative, wherein the determined tissue oxygenation trend corresponds to a trend of the tissue oxygenation saturation.

20. The device of claim 11, wherein computing a tissue oxygenation measurement further comprises:

computing a second derivative of a light attenuation spectrum measured by the sensor;

computing a measure of tissue oxygen saturation in response to the computed second derivative; and

computing a measurement of the total hemoglobin volume fraction from the second derivative and the computed tissue oxygen saturation, wherein the determined tissue oxygenation trend corresponds to a trend of both the tissue oxygenation saturation and the total hemoglobin volume fraction.

21. A computer readable medium having computer executable instructions for performing a method comprising:

sensing cardiac signals;

detecting a cardiac event in response to the sensed cardiac signals using first detection criteria;

delivering a therapy in response to the detected cardiac event;

controlling light emission of a sensor in response to delivering the therapy;

detecting emitted light scattered by a tissue volume adjacent the sensor to generate a corresponding detected light intensity output signal;

determining tissue oxygenation measurements in response to the output signal;

determining a tissue oxygenation trend in response to the tissue oxygenation measurements;

determining a recovery index in response to the determined tissue oxygenation trend; and

controlling one or both of detecting a cardiac event and delivery of therapy in response to the determined recovery index.