Tissue oxygenation monitoring in heart failure

• US 8,515,537 B2
• Filed: 06/10/2010
• Issued: 08/20/2013
• Est. Priority Date: 06/10/2009
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Cinbis, Can, Carney, James K., Kuhn, Jonathan L., Anderson, David A.
• Primary Examiner(s): Chen, Tse
• Assistant Examiner(s): NGUYEN, HIEN NGOC
• Application Number:
  US12/797,823
• Publication Number:
  US 20100317947A1
• Time in Patent Office: 1,167 Days
• Field of Search: 600/324, 600/473, 607 17- 23
• US Class Current: 607/17
• CPC Class Codes: A61N 1/36557 controlled by chemical substances in blood

Abstract

A medical device system and associated method control the delivery of a therapy to a patient. The system includes an activity sensor and detects a change in activity level of the patient. The system further include an optical sensor to sense signal corresponding to tissue light attenuation. The system computes a tissue oxygenation measurement in response to detecting a change in activity level. A parameter controlling delivery of the therapy is adjusted in response to detecting the decreased tissue oxygenation.

Claims

1. A method for controlling a therapy in a patient, comprising;

sensing an activity sensor signal;

detecting a change in activity level of the patient from the activity sensor signal;

sensing an optical sensor signal corresponding to tissue light attenuation in a tissue volume;

computing a tissue oxygenation measurement from the optical sensor signal in response to detecting the change in activity level, the tissue oxygenation measurement comprising contributions from arterial and venous blood in a measurement volume, wherein computing the tissue oxygenation measurement comprises computing a trend;

detecting a decrease in tissue oxygenation in response to the tissue oxygenation measurement, wherein detecting a decrease in the tissue oxygenation measurement comprises;

defining a plurality of thresholds for each one of a respective plurality of activity levels,

selecting one of the plurality of thresholds in response to detecting the change in activity; and

comparing the tissue oxygenation measurement and the selected one of the plurality of thresholds; and

adjusting a parameter controlling delivery of the therapy in response to detecting the decreased tissue oxygenation.

2. The method of claim 1, wherein adjusting the parameter comprises adjusting the parameter to cause a change in the trend.

3. The method of claim 1, wherein detecting the change in activity comprises detecting a change that causes an adjustment to a sensor-indicated pacing rate.

4. The method of claim 1, wherein detecting a decrease in the tissue oxygenation measurement comprises:

defining a plurality of thresholds for each one of a respective plurality of heart rates;

sensing a cardiac signal;

measuring a heart rate of the patient in response to the cardiac signal;

selecting one of the plurality of thresholds based on the measured heart rate; and

comparing the tissue oxygenation measurement and the selected one of the plurality of thresholds.

5. The method of claim 1, wherein the plurality of thresholds comprises a first threshold corresponding to a first activity level and a second threshold corresponding to a second activity level, the first activity level being a higher level of activity than the second activity level, and the first threshold being greater than the second threshold.

6. The method of claim 1, wherein detecting a decrease in the tissue oxygenation measurement comprises storing a previous tissue oxygenation measurement and comparing the tissue oxygenation measurement and the previous tissue oxygenation measurement.

7. The method of claim 1, further comprising:

storing a plurality of parameter settings for each of a plurality of activity levels;

adjusting the parameter by selecting one of the plurality of settings based on the detected change in activity.

8. The method of claim 1, further comprising:

sensing a cardiac signal;

measuring a heart rate of the patient in response to the cardiac signal;

storing a plurality of parameter settings for each of a plurality of heart rates;

adjusting the parameter by selecting one of the plurality of settings corresponding to the measured heart rate.

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

measuring one of a current activity level and a heart rate of the patient; and

normalizing the tissue oxygenation measurement in response to one of the measured activity level and a measured heart rate.

10. The method of claim 1, further comprising:

comparing the tissue oxygenation measurement and an upper threshold;

adjusting the parameter to reduce a duty cycle of the therapy in response to the tissue oxygenation measurement being greater than the upper threshold.

11. The method of claim 1, further comprising:

sensing a cardiac signal; and

measuring a heart rate of the patient in response to the cardiac signal, wherein adjusting the parameter comprises adjusting the parameter to cause an increase in the tissue oxygenation measurement without increasing the heart rate.

12. A medical device system for delivering a therapy to a patient, comprising:

a controller to set a therapy delivery control parameter;

an optical sensor to produce a signal corresponding to tissue light attenuation;

an activity sensor to produce a signal correlated to an activity level of a patient;

a memory to store a plurality of thresholds for each one of a respective plurality of activity levels;

a processor configured to compute an activity measurement from the activity sensor signal, detect a change in activity in response to the activity measurement, compute a tissue oxygenation measurement from the optical sensor signal in response to detecting the change in activity, and detect a decrease in tissue oxygenation in response to the computed tissue oxygenation measurement, the tissue oxygenation measurement comprising contributions from arterial and venous blood in a measurement volume,

wherein computing the tissue oxygenation measurement comprises computing a trend,

wherein detecting the decrease in tissue oxygenation comprises;

selecting one of the plurality of thresholds in response to detecting the change in activity; and

comparing the tissue oxygenation measurement and the selected one of the plurality of thresholds, and

wherein the controller adjusts the control parameter in response to the processor detecting the decreased tissue oxygenation.

13. The system of claim 12, wherein adjusting the parameter comprises adjusting the parameter to cause a change in the trend.

14. The system of claim 12, wherein detecting the change in activity comprises detecting a change that causes an adjustment to a sensor-indicated pacing rate.

15. The system of claim 12, further comprising:

a memory to store a plurality of thresholds for each one of a respective plurality of heart rates; and

a sensor to sense a cardiac signal, wherein the processor is further configured to measure a heart rate of the patient from the cardiac signal, and wherein detecting the decrease in tissue oxygenation comprises;

measuring a heart rate of the patient from the cardiac signal;

selecting one of the plurality of thresholds in response to the measured heart rate; and

comparing the tissue oxygenation measurement and the selected one of the plurality of thresholds.

16. The system of claim 12, wherein the plurality of thresholds comprises a first threshold corresponding to a first activity level and a second threshold corresponding to a second activity level, the first activity level being a higher level of activity than the second activity level, and the first threshold being greater than the second threshold.

17. The system of claim 12, further comprising a memory to store a previous tissue oxygenation measurement, wherein detecting a decrease in the tissue oxygenation measurement comprises comparing the tissue oxygenation measurement and the previous tissue oxygenation measurement.

18. The system of claim 12, further comprising a memory storing a plurality of control parameter settings for each of a plurality of activity levels,

the controller adjusting the parameter by selecting one of the plurality of settings based on the detected change in activity.

19. The system of claim 12 further comprising:

a memory storing a plurality of control parameter settings for each of a plurality of heart rates; and

a sensor to sense a cardiac signal, wherein the processor is configured to measure a heart rate in response to the cardiac signal, and the controller adjusts the parameter by selecting one of the plurality of settings corresponding to the measured heart rate.

20. The system of claim 12, further comprising a sensor sensing a cardiac signal, wherein computing the tissue oxygenation measurement comprises:

measuring one of a current activity level from the activity sensor signal and a heart rate from the cardiac signal; and

normalizing the tissue oxygenation measurement using one of the measured activity level and the measured heart rate.

21. The system of claim 12, wherein the processor is further configure to compare the tissue oxygenation measurement to an upper threshold, and wherein the controller is configured to adjust the parameter to reduce a duty cycle of the therapy in response to the tissue oxygenation measurement exceeding the upper threshold.

22. The system of claim 12 further comprising a sensor to sense a cardiac signal, wherein the processor is further configured to measure a heart rate of the patient, and the controller and the processor are configured to operate cooperatively to adjust the parameter to cause an increase in the tissue oxygenation measurement without increasing the heart rate.

23. A non-transitory computer readable medium having computer executable instructions for performing a method comprising:

sensing an activity sensor signal;

detecting a change in activity level of the patient from the activity sensor signal;

sensing an optical sensor signal corresponding to tissue light attenuation;

computing a tissue oxygenation measurement from the optical sensor signal in response to detecting the change in activity level, the tissue oxygenation measurement comprising contributions from arterial and venous blood in a measurement volume, wherein computing the tissue oxygenation measurement comprises computing a trend;

detecting a decrease in tissue oxygenation in response to the tissue oxygenation measurement, wherein detecting a decrease in the tissue oxygenation measurement comprises;

defining a plurality of thresholds for each one of a respective plurality of activity levels,

selecting one of the plurality of thresholds in response to detecting the change in activity; and

comparing the tissue oxygenation measurement and the selected one of the plurality of thresholds; and

adjusting a parameter controlling delivery of a therapy in response to detecting the decreased tissue oxygenation.