TISSUE PERFUSION SENSOR CONTROL

• US 20090326350A1
• Filed: 06/30/2008
• Published: 12/31/2009
• Est. Priority Date: 06/30/2008
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Kracker, Stefan G.
• Granted Patent: US 10,058,274 B2
• Time in Patent Office: Days
• US Class Current: 600/324
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• 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 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61N 1/36557 controlled by chemical substances in blood

Abstract

An optical perfusion sensor may monitor blood oxygen saturation of blood-perfused tissue, which may be referred to as tissue perfusion, until a tissue perfusion value is within a threshold range of a reference value, and, in some examples, for at least a minimum period of time. The tissue perfusion value may indicate an absolute blood oxygen saturation level or a relative change in blood oxygen saturation level. The reference value may be, for example, determined by an oxygen (O2) variation index that indicates a change in blood oxygen saturation of tissue. In some examples, the optical perfusion sensor may be activated upon detecting a cardiac event, such as a cardiac arrhythmia. In addition, in some examples, cardiac signal monitoring may be activated upon detecting a threshold change in tissue perfusion.

Claims

1. A method comprising:

receiving an electrical signal from an optical perfusion sensing module, wherein the electrical signal is indicative of a blood oxygen saturation level of a patient;

determining whether a perfusion value based on the electrical signal is within a threshold range of values; and

modifying an operation of the optical perfusion sensing module if the perfusion value is within the threshold range of values.

2. The method of claim 1, the method further comprising storing the electrical signal in a memory, wherein modifying the operation of the optical perfusion sensing module comprises stopping the storing of the electrical signal in the memory.

3. The method of claim 1, wherein modifying the operation of the optical perfusion sensing module comprises deactivating a light source of the optical perfusion sensor, wherein the light source stops emitting light upon deactivation.

4. The method of claim 1, wherein the perfusion value comprises at least one of an oxygen variation index or an amplitude of the electrical signal.

5. The method of claim 1, wherein the threshold range of values comprises a threshold range of values relative to a reference value.

6. The method of claim 5, wherein the perfusion value comprises an oxygen variation index and the reference value is based on a trend of the oxygen variation index over time.

7. The method of claim 5, further comprising determining the reference value, wherein determining the reference value comprises:

determining a plurality of perfusion values during a predetermined period of time; and

determining the reference value based on the plurality of perfusion values.

8. The method of claim 7, wherein determining the reference value based on the plurality of perfusion values comprises determining a mean perfusion value of the plurality of perfusion values, wherein the reference value comprises the mean perfusion value.

9. The method of claim 7, wherein determining the reference value based on the plurality of perfusion values comprises:

determining a mean perfusion value of the plurality of perfusion values;

determining a deviation of each perfusion value of the plurality of perfusion values from the mean perfusion value;

determining a mean deviation value based on the deviation of each perfusion value of the plurality of perfusion values from the mean perfusion value; and

wherein the reference value comprises the mean perfusion value and the threshold range comprises the mean deviation value.

10. The method of claim 1, further comprising receiving a cardiac signal of a heart of the patient and controlling the optical perfusion sensing module based on the cardiac signal.

11. The method of claim 10, wherein controlling the optical perfusion sensing module based on the cardiac signal comprises detecting a cardiac arrhythmia of the heart based on the cardiac signal of the heart and activating sensing by the optical perfusion sensing module in response to detecting the cardiac arrhythmia.

12. The method of claim 11, further comprising determining whether the characteristic of the electrical signal was within the threshold range of values prior to the detection of the cardiac arrhythmia and generating an indication if the characteristic of the electrical signal was not within the threshold range of values prior to the detection of the cardiac arrhythmia.

13. The method of claim 1, further comprising controlling an operation of a cardiac signal sensing module based on the electrical signal.

14. The method of claim 13, wherein controlling the operation of the cardiac signal sensing module based on the electrical signal comprises receiving and storing a cardiac signal generated by the cardiac signal sensing module if the perfusion value is outside the threshold range of values.

15. A system comprising:

an optical perfusion sensing module that generates an electrical signal indicative of a blood oxygen saturation level of a patient; and

a processor that receives the electrical signal from the optical perfusion sensing module, determines whether a perfusion value based on the electrical signal is within a threshold range of values, and modifies an operation of the optical perfusion sensing module if the perfusion value is within the threshold range of values.

16. The system of claim 15, the further comprising a memory, wherein the processor stores at least one of the electrical signal or the perfusion value in the memory, and if the perfusion value is within the threshold range of values, the processor modifies the operation of the optical perfusion sensing module by at least stopping the storage of the at least one of the electrical signal or the perfusion value in the memory.

17. The system of claim 15, wherein the perfusion value comprises at least one of an oxygen variation index or an amplitude of the electrical signal.

18. The system of claim 15, wherein the threshold range of values comprises a threshold range relative to a reference value.

19. The system of claim 18, wherein the processor determines the reference value by at least:

determining a plurality of perfusion values during a predetermined period of time; and

determining the reference value based on the plurality of perfusion values.

20. The system of claim 18, wherein each perfusion value of the plurality of perfusion values comprises an oxygen variation index, and the reference value is based on a trend of the oxygen variation index over time.

21. The system of claim 15, further comprising a cardiac signal sensing module that generates a cardiac signal indicative of electrical activity of a heart of the patient, wherein the processor controls the optical perfusion sensing module based on the cardiac signal.

22. The system of claim 21, wherein the processor detects a cardiac arrhythmia of the heart based on the cardiac signal and activates sensing by the optical perfusion sensing module in response to detecting the cardiac arrhythmia.

23. The system of claim 22, wherein the processor determines whether the characteristic of the electrical signal was within the threshold range of values prior to the detection of the cardiac arrhythmia and generates an indication if the characteristic of the electrical signal was not within the threshold range of values prior to the detection of the cardiac arrhythmia.

24. The system of claim 21, wherein the cardiac signal sensing module and optical perfusion sensing module are disposed within a common housing.

25. The system of claim 21, wherein the cardiac signal sensing module and optical perfusion sensing module are implanted at different sites within the patient.

26. The system of claim 15, further comprising a cardiac signal sensing module, wherein the processor controls an operation of the cardiac signal sensing module based on the electrical signal generated by the optical perfusion sensing module.

27. A system comprising:

means for receiving an electrical signal from an optical perfusion sensing module, wherein the electrical signal is indicative of a blood oxygen saturation level of a patient;

means for determining whether a perfusion value based on the electrical signal is within a threshold range of values; and

means for modifying an operation of the optical perfusion sensing module if the perfusion value is within the threshold range of values.

28. The system of claim 27, further comprising means for receiving a cardiac signal of a heart of the patient and controlling the optical perfusion sensing module based on the cardiac signal.

29. The system of claim 27, further comprising means for controlling an operation of a cardiac signal sensing module based on the electrical signal.

30. A computer-readable medium comprising instructions that cause a programmable processor to:

receive an electrical signal from an optical perfusion sensing module, wherein the electrical signal is indicative of a blood oxygen saturation level of a patient;

determine whether a perfusion value based on the electrical signal is within a threshold range of values; and

modify an operation of the optical perfusion sensing module if the perfusion value is within the threshold range of values.