Method and apparatus for impedance signal localizations from implanted devices

• US 20040215097A1
• Filed: 04/25/2003
• Published: 10/28/2004
• Est. Priority Date: 04/25/2003
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Wang, Li
• Granted Patent: US 7,149,573 B2
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• 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 1/36521 the parameter being derived from measurement of an electrical impedance

Abstract

Method and apparatus for monitoring a plurality of physiological factors contributing to physiological conditions of a heart, that determines a first impedance, corresponding to the plurality of physiological factors, across a plurality of vectors, and a second impedance, corresponding to the plurality of physiological factors, across the plurality of vectors subsequent to determining the first impedance. A relative change in impedance corresponding to the plurality of vectors is determined in response to the first impedance and the second impedance, first minimally contributing physiological factors of the plurality of physiological factors associated with a first physiological factor of the plurality of physiological factors are determined, and relative change in tissue resistivity corresponding to the first physiological factor in response to physiological factors of the plurality of physiological factors other than the first minimal contributing physiological factors and the relative change in impedance are determined.

Claims

1. A method for monitoring a plurality of physiological factors contributing to physiological conditions of a patient in an implantable medical device, comprising:

determining a first impedance, corresponding to the plurality of physiological factors, across a plurality of vectors;

determining a second impedance, corresponding to the plurality of physiological factors, across the plurality of vectors subsequent to determining the first impedance;

determining a relative change in impedance corresponding to the plurality of vectors in response to the first impedance and the second impedance;

determining first minimally contributing physiological factors of the plurality of physiological factors associated with a first physiological factor of the plurality of physiological factors; and

determining relative change in tissue resistivity corresponding to the first physiological factor in response to physiological factors of the plurality of physiological factors other than the first minimal contributing physiological factors and the relative change in impedance.

2. The method of claim 1, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity.

3. The method of claim 1, wherein the plurality of vectors include a first vector and a second vector, the first vector including a first stimulation path and a first sense path extending between a first electrode, positioned within a ventricle of the heart, and an uninsulated portion of a housing of the device, and the second vector including a second stimulation path, extending between a second electrode, positioned within a ventricle of the heart, and the uninsulated portion of the housing, and a second sense path extending between the first electrode and the uninsulated portion of the housing.

4. The method of claim 3, further comprising:

determining second minimally contributing physiological factors of the plurality of physiological factors associated with a second physiological factor of the plurality of physiological factors; and

determining relative change in tissue resistivity for the second physiological factor in response to physiological factors of the plurality of physiological factors other than the second minimal contributing physiological factors, the relative change in impedance, and the determined relative change in tissue resistivity for first physiological factor.

5. The method of claim 4, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity and the second physiological factor is lung volume.

6. The method of claim 3, further comprising:

determining second minimally contributing physiological factors of the plurality of physiological factors associated with a second physiological factor of the plurality of physiological factors; and

determining relative change in tissue resistivity corresponding to the second physiological factor in response to physiological factors of the plurality of physiological factors other than the second minimally contributing physiological factors, the relative change in impedance, and the determined relative change in tissue resistivity for the first physiological factor, wherein the plurality of vectors further includes a third vector including a third stimulation path and a third sensing path extending between the second electrode and the uninsulated portion.

7. The method of claim 6, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity and the second physiological factor is heart muscle.

8. The method of claim 1, wherein the plurality of vectors include a first vector and a second vector, the first vector including a first stimulation path and a first sense path extending between a first electrode, positioned within a ventricle of the heart, and an uninsulated portion of a housing of the device, and the second vector including a second stimulation path extending between the first electrode and the uninsulated portion of the housing and a second sense path extending between the first electrode and a second electrode, positioned along the housing.

9. The method of claim 8, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is skeletal muscle resistivity.

10. The method of claim 4, wherein the plurality of vectors further include a third vector including a third stimulation path extending between the first electrode and the uninsulated portion of the housing and a third sensing path extending between the first electrode and a third electrode positioned along the housing.

11. The method of claim 10, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity and the second physiological factor is skeletal muscle resistivity.

12. The method of claim 6, further comprising:

determining third minimally contributing physiological factors of the plurality of physiological factors associated with a third physiological factor of the plurality of physiological factors; and

determining relative change in tissue resistivity corresponding to the third physiological factor in response to physiological factors of the plurality of physiological factors other than the third minimally contributing physiological factors, the relative change in impedance, and the determined relative change in tissue resistivity for the first physiological factor, wherein the plurality of vectors further includes a fourth vector including a fourth stimulation path extending between the first electrode and the uninsulated portion of the housing and a fourth sensing path extending between the first electrode and a third electrode positioned along the housing.

13. The method of claim 12, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity, the second physiological factor is heart muscle resistivity and the third physiological factor is skeletal muscle resistivity.

14. The method of claim 6, further comprising:

determining third minimally contributing physiological factors of the plurality of physiological factors associated with a third physiological factor of the plurality of physiological factors; and

determining relative change in tissue resistivity corresponding to the third physiological factor in response to physiological factors of the plurality of physiological factors other than the third minimally contributing physiological factors, the relative change in impedance, and the determined change in resistivity for the first physiological factor and the second physiological factor, wherein the plurality of vectors further includes a fourth vector and a fifth vector, the fourth vector including a fourth stimulation path extending between the second electrode and the uninsulated portion of the housing and a fourth sense path extending between a third electrode positioned within the ventricle and the uninsulated portion of the housing, and the fifth vector including a fifth stimulation path extending between the first electrode and the uninsulated portion of the housing and a fifth sensing path extending between the first electrode and a fourth electrode positioned along the housing.

15. The method of claim 14, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity, the second physiological factor is heart muscle resistivity and the third physiological factor is skeletal muscle resistivity.

16. The method of claim 6, further comprising:

determining third minimally contributing physiological factors of the plurality of physiological factors associated with a third physiological factor of the plurality of physiological factors; and

determining relative change in tissue resistivity corresponding to the third physiological factor in response to physiological factors of the plurality of physiological factors other than the third minimally contributing physiological factors, the relative change in impedance, and the determined relative change in tissue resistivity for the first physiological factor and the second physiological factor.

17. The method of claim 16, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity, the second physiological factor is heart muscle resistivity and the third physiological factor is lung volume.

18. The method of claim 12, further comprising:

determining fourth minimally contributing physiological factors of the plurality of physiological factors associated with a fourth physiological factor of the plurality of physiological factors; and

determining relative change in tissue resistivity corresponding to the fourth physiological factor in response to physiological factors of the plurality of physiological factors other than the fourth minimally contributing physiological factors, the relative change in impedance, and the determined relative change in tissue resistivity for the first physiological factor and the second physiological factor;

determining fifth minimally contributing physiological factors of the plurality of physiological factors associated with a fifth physiological factor of the plurality of physiological factors; and

determining relative change in tissue resistivity corresponding to the fifth physiological factor in response to physiological factors of the plurality of physiological factors other than the fifth minimally contributing physiological factors, the relative change in impedance, and the determined relative change in tissue resistivity for the first physiological factor, the second physiological factor, the third physiological factor, and the fourth physiological factor, wherein the plurality of vectors include a fifth vector including a fifth stimulation path extending between one of the second electrode and a fourth electrode positioned within an atrium of the heart, and the fourth electrode and the uninsulated portion of the housing, and a fifth sense path extending between one of a fifth electrode positioned within the ventricle and a sixth electrode positioned within the atrium, and the sixth electrode and the uninsulated portion of the housing.

19. The method of claim 18, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity, the second physiological factor is heart muscle resistivity, the third physiological factor is skeletal muscle resistivity, the fourth physiological factor is lung volume and the fifth physiological factor is heart volume and lung resistivity.

20. An implantable medical device adapted to be implanted within a patient, comprising:

a housing portion housing electrical circuitry for operating the implantable medical device;

a plurality of electrodes positioned within the patient; and

a microprocessor determining a relative change in impedance corresponding to a plurality of vectors formed between the plurality of electrodes, determining first minimally contributing physiological factors of a plurality of physiological factors associated with a first physiological factor of a plurality of physiological factors, and determining relative change in tissue resistivity corresponding to the first physiological factor in response to physiological factors of the plurality of physiological factors other than the first minimal contributing physiological factors and the relative change in impedance.

21. The device of claim 20, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity.

22. The device of claim 20, wherein the plurality of vectors include a first vector and a second vector, the first vector including a first stimulation path and a first sense path extending between a first electrode of the plurality of electrodes, positioned within a ventricle of the heart, and an uninsulated portion of a housing of the device, and the second vector including a second stimulation path, extending between a second electrode of the plurality of electrodes, positioned within a ventricle of the heart, and the uninsulated portion of the housing, and a second sense path extending between the first electrode and the uninsulated portion of the housing.

23. The device of claim 22, wherein the microprocessor determines second minimally contributing physiological factors of the plurality of physiological factors associated with a second physiological factor of the plurality of physiological factors, and determines relative change in tissue resistivity for the second physiological factor in response to physiological factors of the plurality of physiological factors other than the second minimal contributing physiological factors, the relative change in impedance, and the determined relative change in tissue resistivity for first physiological factor.

24. The device of claim 23, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity and the second physiological factor is lung volume.

25. The device of claim 22, wherein the microprocessor determines second minimally contributing physiological factors of the plurality of physiological factors associated with a second physiological factor of the plurality of physiological factors, and determines relative change in tissue resistivity corresponding to the second physiological factor in response to physiological factors of the plurality of physiological factors other than the second minimally contributing physiological factors, the relative change in impedance, and the determined relative change in tissue resistivity for the first physiological factor, wherein the plurality of vectors further includes a third vector including a third stimulation path and a third sensing path extending between the second electrode and the uninsulated portion.

26. The device of claim 25, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity and the second physiological factor is heart muscle.

27. The device of claim 20, wherein the plurality of vectors include a first vector and a second vector, the first vector including a first stimulation path and a first sense path extending between a first electrode of the plurality of electrodes, positioned within a ventricle of the heart, and an uninsulated portion of a housing of the device, and the second vector including a second stimulation path extending between the first electrode and the uninsulated portion of the housing and a second sense path extending between the first electrode and a second electrode of the plurality of electrodes, positioned along the housing.

28. The device of claim 27, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is skeletal muscle resistivity.

29. The device of claim 23, wherein the plurality of vectors further include a third vector including a third stimulation path extending between the first electrode and the uninsulated portion of the housing and a third sensing path extending between the first electrode and a third electrode of the plurality of electrodes positioned along the housing.

30. The device of claim 29, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity and the second physiological factor is skeletal muscle resistivity.

31. The device of claim 25, wherein the microprocessor determines third minimally contributing physiological factors of the plurality of physiological factors associated with a third physiological factor of the plurality of physiological factors, and determines relative change in tissue resistivity corresponding to the third physiological factor in response to physiological factors of the plurality of physiological factors other than the third minimally contributing physiological factors, the relative change in impedance, and the determined relative change in tissue resistivity for the first physiological factor, wherein the plurality of vectors further includes a fourth vector including a fourth stimulation path extending between the first electrode and the uninsulated portion of the housing and a fourth sensing path extending between the first electrode and a third electrode of the plurality of electrodes positioned along the housing.

32. The device of claim 31, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity, the second physiological factor is heart muscle resistivity and the third physiological factor is skeletal muscle resistivity.

33. The device of claim 25, wherein the microprocessor determines third minimally contributing physiological factors of the plurality of physiological factors associated with a third physiological factor of the plurality of physiological factors, and determines relative change in tissue resistivity corresponding to the third physiological factor in response to physiological factors of the plurality of physiological factors other than the third minimally contributing physiological factors, the relative change in impedance, and the determined relative change in tissue resistivity for the first physiological factor and the second physiological factor, wherein the plurality of vectors further includes a fourth vector and a fifth vector, the fourth vector including a fourth stimulation path extending between the second electrode and the uninsulated portion of the housing and a fourth sense path extending between a third electrode of the plurality of electrodes positioned within the ventricle and the uninsulated portion of the housing, and the fifth vector including a fifth stimulation path extending between the first electrode and the uninsulated portion of the housing and a fifth sensing path extending between the first electrode and a fourth electrode of the plurality of electrodes positioned along the housing.

34. The device of claim 33, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity, the second physiological factor is heart muscle resistivity and the third physiological factor is skeletal muscle resistivity.

35. The device of claim 25, wherein the microprocessor determines third minimally contributing physiological factors of the plurality of physiological factors associated with a third physiological factor of the plurality of physiological factors, and determines relative change in tissue resistivity corresponding to the third physiological factor in response to physiological factors of the plurality of physiological factors other than the third minimally contributing physiological factors, the relative change in impedance, and the determined relative change in tissue resistivity for the first physiological factor and the second physiological factor.

36. The device of claim 35, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity, the second physiological factor is heart muscle resistivity and the third physiological factor is lung volume.

37. The device of claim 31, wherein the microprocessor:

determines fourth minimally contributing physiological factors of the plurality of physiological factors associated with a fourth physiological factor of the plurality of physiological factors,

determines relative change in tissue resistivity corresponding to the fourth physiological factor in response to physiological factors of the plurality of physiological factors other than the fourth minimally contributing physiological factors, the relative change in impedance, and the determined relative change in tissue resistivity for the first physiological factor and the second physiological factor,

determines fifth minimally contributing physiological factors of the plurality of physiological factors associated with a fifth physiological factor of the plurality of physiological factors, and

determines relative change in tissue resistivity corresponding to the fifth physiological factor in response to physiological factors of the plurality of physiological factors other than the fifth minimally contributing physiological factors, the relative change in impedance, and the determined relative change in tissue resistivity for the first physiological factor, the second physiological factor, the third physiological factor, and the fourth physiological factor, wherein the plurality of vectors include a fifth vector including a fifth stimulation path extending between one of the second electrode and a fourth electrode of the plurality of electrodes positioned within an atrium of the heart, and the fourth electrode and the uninsulated portion of the housing, and a fifth sense path extending between one of a fifth electrode of the plurality of electrodes positioned within the ventricle and a sixth electrode of the plurality of electrodes positioned within the atrium, and the sixth electrode and the uninsulated portion of the housing.

38. The device of claim 37, wherein the plurality of physiological factors include lung resistivity, blood resistivity, heart muscle resistivity, skeletal muscle resistivity, heart volume and lung volume, and wherein the first physiological factor is blood resistivity, the second physiological factor is heart muscle resistivity, the third physiological factor is skeletal muscle resistivity, the fourth physiological factor is lung volume and the fifth physiological factor is heart volume and lung resistivity.

39. A computer-readable medium having computer executable instructions for performing a method for monitoring a plurality of physiological factors contributing to physiological conditions of a heart, comprising:

determining a first impedance, corresponding to the plurality of physiological factors, across a plurality of vectors;

determining a second impedance, corresponding to the plurality of physiological factors, across the plurality of vectors subsequent to determining the first impedance;

determining a relative change in impedance corresponding to the plurality of vectors in response to the first impedance and the second impedance;

determining first minimally contributing physiological factors of the plurality of physiological factors associated with a first physiological factor of the plurality of physiological factors; and

determining relative change in tissue resistivity corresponding to the first physiological factor in response to physiological factors of the plurality of physiological factors other than the first minimal contributing physiological factors and the relative change in impedance.