PHYSIOLOGICAL PARAMETER MONITORING WITH MINIMIZATION OF MOTION ARTIFACTS

• US 20100030088A1
• Filed: 07/30/2008
• Published: 02/04/2010
• Est. Priority Date: 07/30/2008
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Carney, James Kevin, Cinbis, Can
• Granted Patent: US 8,273,032 B2
• Time in Patent Office: Days
• US Class Current: 600/500
• 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 5/02427 Details of sensor
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• 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 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7214 using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths

Abstract

An implanted system includes at least two optical sensors implanted proximate to an artery of a patient such that one optical sensor is upstream of another optical sensor. Arterial pulses of the patient may be detected based on electrical signals from at least one of the optical sensors. In addition, electrical signals from the optical sensors may be used to minimize the effects of motion artifacts on the detection of arterial pulses. For example, a detected pulse may be determined to be a spurious pulse if the optical sensors indicate the occurrence of the pulse within a predetermined range of time. As another example, a first optical sensor signal may be shifted in time relative to a second optical sensor signal, and the signals may be correlated. An arterial pulse may be detected at a time at which a peak or trough amplitude value of the correlated signal is observed.

Claims

1. A method comprising:

receiving a first electrical signal from a first optical sensor implanted within a patient;

receiving a second electrical signal from a second optical sensor implanted within the patient;

detecting an arterial pulse of the patient based on at least one of the first or second electrical signals; and

determining whether the arterial pulse is a spurious pulse based on the first and second electrical signals.

2. The method of claim 1, wherein the first and second optical sensors are implanted along an artery of the patient.

3. The method of claim 2, wherein the second optical sensor is located downstream of the first optical sensor relative to a direction of blood flow in the artery.

4. The method of claim 1, wherein the first and second optical sensors are implanted along different arteries of the patient.

5. The method of claim 1, wherein the first and second optical sensors are coupled to a common housing.

6. The method of claim 5, wherein the housing defines a surface and the first and second optical sensors are coupled to the surface of the common housing.

7. The method of claim 1, wherein the first and second optical sensors comprise separate housings that are movable relative to each other.

8. The method of claim 1, wherein detecting the arterial pulse comprises detecting the arterial pulse based on a first signal characteristics of the first electrical signal and a second signal characteristic of the second electrical signal, and wherein determining whether the arterial pulse is a spurious pulse comprises determining whether the first and second signal characteristics occurred within a predetermined range of time of one another, and if the first and second characteristics occurred within the predetermined range of time, determining that the detected arterial pulse is the spurious pulse.

9. The method of claim 8, wherein the predetermined range of time comprises less than about 0.5 milliseconds.

10. The method of claim 8, wherein the first and second signal characteristics comprise at least one of a peak amplitude, a trough amplitude or a threshold crossing.

11. The method of claim 1, wherein detecting the arterial pulse comprises:

normalizing the first electrical signal;

normalizing the second electrical signal;

detecting a first threshold crossing of the first electrical signal; and

detecting a second threshold crossing of the second electrical signal, wherein the first and second threshold crossings indicate the arterial pulse.

12. The method of claim 11, wherein determining whether the arterial pulse is a spurious pulse comprises determining whether the first and second threshold crossings occurred within a predetermined range of time of one another and if the first and second threshold crossings occurred within the predetermined range of time, determining that the detected arterial pulse is the spurious pulse.

13. The method of claim 12, wherein the predetermined range of time comprises less than about 0.5 milliseconds.

14. The method of claim 11, wherein the first and second thresholds comprise approximately zero volts.

15. An implantable medical system comprising:

a first optical sensor that generates a first electrical signal;

a second optical sensor that generates a second electrical signal; and

a processor that receives the first electrical signal and the second electrical signal, detects an arterial pulse of the patient based on at least one of the first or second electrical signals, and determines whether the arterial pulse is a spurious pulse based on the first and second electrical signals.

16. The implantable medical system of claim 15, wherein the first and second optical sensors each comprise at least one light source and at least one detector.

17. The implantable medical system of claim 15, wherein the first and second optical sensors are implanted along one or more arteries of the patient.

18. The implantable medical system of claim 15, wherein the first and second optical sensors are separated by a distance of about 0.5 millimeters to about 60 millimeters.

19. The implantable medical system of claim 15, wherein the second optical sensor is implanted downstream of the first optical sensor relative to a direction of blood flow in an artery of the patient.

20. The implantable medical system of claim 15, further comprising a housing, wherein the first and second optical sensors are coupled to the housing.

21. The implantable medical system of claim 15, wherein the first and second optical sensors comprise separate housings that are movable relative to each other.

22. The implantable medical system of claim 21, wherein the first and second optical sensors further comprise respective telemetry modules, and wherein the first and second optical sensors wirelessly communicate via the respective telemetry modules.

23. The implantable medical system of claim 15, wherein the processor detects the arterial pulses based on a first signal characteristics of the first electrical signal and a second signal characteristic of the second electrical signal, and determines whether the arterial pulse is a spurious pulse by at least determining whether the first and second signal characteristics occurred within a predetermined range of time, and if the first and second characteristics occurred within the predetermined range of time, the processor determines that the detected arterial pulse is the spurious pulse.

24. The implantable medical system of claim 23, wherein the first and second signal characteristics comprise at least one of a peak amplitude, a trough amplitude or a threshold crossing.

25. The implantable medical system claim 15, wherein the processor detects the arterial pulses by at least normalizing the first electrical signal, normalizing the second electrical signal, detecting a first threshold crossing of the first electrical signal, and detecting a second threshold crossing of the second electrical signal, where the first and second threshold crossings indicate the arterial pulse.

26. The implantable medical system claim 25, wherein the processor determines whether the arterial pulse is a spurious pulse by at least determining whether the first and second threshold crossings occurred within a predetermined range of time of one another and if the first and second threshold crossings occurred within the predetermined range of time, determining that the detected arterial pulse is the spurious pulse.

27. The implantable medical system claim 26, wherein the first and second thresholds comprise approximately zero volts.

28. A medical system comprising:

means for receiving a first electrical signal from a first optical sensor implanted within a patient;

means for receiving a second electrical signal from a second optical sensor implanted within the patient;

means for detecting an arterial pulse of the patient based on at least one of the first or second electrical signals; and

means for determining whether the arterial pulse is a spurious pulse based on the first and second electrical signals.

29. The medical system of claim 28, wherein the means for detecting the arterial pulse comprises means for detecting the arterial pulse based on a first signal characteristics of the first electrical signal and a second signal characteristic of the second electrical signal, and wherein the means for determining whether the arterial pulse is a spurious pulse comprises means for determining whether the first and second signal characteristics occurred within a predetermined range of time of one another, and if the first and second characteristics occurred within the predetermined range of time, the means for determining whether the arterial pulse is a spurious pulse determines that the detected arterial pulse is the spurious pulse.

30. The medical system of claim 28, wherein the means for detecting the arterial pulse comprises:

means for normalizing the first electrical signal;

means for normalizing the second electrical signal;

means for detecting a first threshold crossing of the first electrical signal; and

means for detecting a second threshold crossing of the second electrical signal, wherein the first and second threshold crossings indicate the arterial pulse.

31. A method comprising:

receiving a first electrical signal from a first optical sensor implanted within a patient;

receiving a second electrical signal from a second optical sensor implanted within the patient, wherein the first and second optical sensors are positioned relative to each other such that the first optical sensor detects an arterial pulse of the patient before the second optical sensor;

detecting a first signal characteristic of the first signal;

detecting a second signal characteristic of the second signal;

determining whether the first and second signal characteristics occurred within a predetermined range of time; and

if the first and signal characteristics occurred within the predetermined range of time, determining that the first and second signal characteristics are artifacts.

32. The method of claim 31, wherein the first and second signal characteristics each comprise one of a peak amplitude, a trough amplitude or a threshold crossing.

33. A method comprising:

receiving a first electrical signal from a first optical sensor implanted within a patient;

receiving a second electrical signal from a second optical sensor implanted within the patient;

shifting the first electrical signal in time relative to the second electrical signal to generate a time-shifted electrical signal;

correlating the second electrical signal and the time-shifted electrical signal to generate a correlated signal; and

detecting an arterial pulse of the patient based on the correlated signal.

34. The method of claim 33, wherein detecting the arterial pulse comprises identifying a peak amplitude or a trough amplitude of the correlated signal, wherein the peak or the trough amplitude is associated with the arterial pulse of the patient.

35. The method of claim 33, wherein the first and second optical sensors are implanted along an artery of the patient and the second optical sensor is located downstream of the first optical sensor relative to a direction of blood flow in an artery of the patient.

36. The method of claim 33, wherein shifting the first electrical signal in time relative to the second electrical signal to generate the time-shifted electrical signal comprises shifting the first electrical signal by 0.5 milliseconds to about 80 milliseconds.

37. An implantable medical system comprising:

a first optical sensor that generates a first electrical signal;

a second optical sensor that generates a second electrical signal; and

a processor that receives the first electrical signal and the second electrical signal, shifts the first electrical signal in time relative to the second electrical signal to generate a time-shifted electrical signal, correlates the second electrical signal and the time-shifted electrical signal to generate a correlated signal, and detects an arterial pulse of a patient based on the correlated signal.

38. The implantable medical system of claim 37, wherein the processor detects the arterial pulse by at least identifying a peak amplitude or a trough amplitude of the correlated signal, wherein the peak amplitude or the trough amplitude is associated with the arterial pulse of the patient.

39. The implantable medical system of claim 37, wherein the second optical sensor is implanted downstream of the first optical sensor relative to a direction of blood flow in an artery of the patient.

40. The implantable medical system of claim 37, wherein the processor shifts the first electrical signal in time relative to the second electrical signal to generate the time-shifted electrical signal by at least shifting the first electrical signal by about 0.5 milliseconds to about 80 milliseconds.