Bio-impedance sensor and sensing method

• US 20070142733A1
• Filed: 12/20/2005
• Published: 06/21/2007
• Est. Priority Date: 12/20/2005
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Dalal, Yousufali, Hatlestad, John, Brockway, Marina, Moon, Loell
• Granted Patent: US 8,204,585 B2
• Time in Patent Office: Days
• US Class Current: 600/508
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/3684 for stimulating the heart at multiple sites of the ventricle or the atrium
• CPC Class Codes: A61N 1/36843 Bi-ventricular stimulation
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

Implantable medical devices and techniques are implemented that use bio-impedance to measure aspects of patient physiology. A signal separation method is performed at least in part in an implantable device. The method involves detecting a plurality of impedance signals using a plurality of implantable electrodes coupled to the implantable device. The method further involves separating one or more signals from the plurality of impedance signals using a signal separation technique, such as an algorithm-based separation technique.

Claims

1. A signal separation method performed at least in part in an implantable device, the method comprising:

detecting a plurality of impedance signals using a plurality of implantable electrodes coupled to the implantable device; and

separating one or more signals from the plurality of impedance signals using a signal separation technique.

2. The method of claim 1, further comprising storing the separated one or more signals within the implantable device.

3. The method of claim 1, further comprising using the separated one or more signals within the implantable device.

4. The method of claim 1, further comprising transferring the separated one or more signals from the implantable device to a patient-external location.

5. The method of claim 1, wherein the signal separation technique comprises forming a linear combination of impedance signals that increases a signal-to-noise ratio for the separated one or more signals.

6. The method of claim 5, wherein forming the linear combination comprises forming the linear combination of impedance signals using blind source separation.

7. The method of claim 1, wherein the signal separation technique comprises adaptive noise cancellation.

8. The method of claim 1, further comprising identifying the one or more separated signals with one or more signals of interest.

9. The method of claim 8, wherein identifying the one or more separated signals comprises identifying the one or more separated signals by a maximum of a correlation between the one or more separated signals and a signal of interest.

10. The method of claim 8, wherein the one or more signals of interest comprise a physiological signal.

11. The method of claim 10, wherein the physiological signal comprises a signal associated with respiration.

12. The method of claim 10, wherein the physiological signal comprises a signal associated with cardiac activity.

13. The method of claim 10, wherein the physiological signal comprises a signal useful for detecting presence of thoracic fluid.

14. The method of claim 8, wherein identifying the one or more separated signals comprises matching a morphology of a separated signal with a morphology of a signal of interest.

15. The method of claim 8, wherein identifying the one or more separated signals comprises matching frequency content of a separated signal with frequency content of a signal of interest.

16. The method of claim 8, wherein identifying the one or more separated signals comprises matching timing of events within a separated signal with timing of events within a signal of interest.

17. An implantable medical device, comprising:

a plurality of implantable electrodes each configured for sensing an impedance signal, thereby providing a plurality of impedance signals; and

a processor coupled to the plurality of electrodes and configured to receive the plurality of impedance signals, the processor further configured to separate one or more signals from the plurality of impedance signals using a signal separation technique.

18. The device of claim 17, wherein the processor is coupled to memory, and the separated one or more signals are stored in the memory.

19. The device of claim 17, further comprising communication circuitry coupled to the processor, the communication circuitry configured to transfer the separated one or more signals to a patient-external receiver.

20. The device of claim 17, wherein the processor is configured to form a linear combination of impedance signals that increases a signal-to-noise ratio for the separated one or more signals.

21. The device of claim 20, wherein the processor is configured to perform blind source separation when forming the linear combination of impedance signals.

22. The device of claim 17 wherein the processor is configured to perform adaptive noise cancellation to separate the one or more signals.

23. The device of claim 17, wherein the processor is configured to identify the one or more separated signals with one or more signals of interest.

24. The device of claim 23, wherein the one or more signals of interest comprise a physiological signal.

25. The device of claim 24, wherein the physiological signal comprises a signal associated with one or more of respiration, cardiac activity, and a signal useful for detecting presence of thoracic fluid.

26. The device of claim 23, wherein the processor is configured to perform matching of a morphology of a separated signal with a morphology of a signal of interest.

27. The device of claim 23, wherein the processor is configured to perform matching of frequency content of a separated signal with frequency content of a signal of interest.

28. The device of claim 23, wherein the processor is configured to perform matching of timing of events within a separated signal with timing of events within a signal of interest.

29. An implantable medical device, comprising:

means for detecting a plurality of impedance signals using a plurality of implantable electrodes coupled to the implantable device; and

means for separating one or more signals from the plurality of impedance signals using a signal separation technique.