Methods and apparatus for localization, diagnosis, contact or activity detection of bio-electric tissue

• US 20080027350A1
• Filed: 07/13/2006
• Published: 01/31/2008
• Est. Priority Date: 07/13/2006
• Status: Abandoned Application

• Current Assignee: Abbott Cardiovascular Systems Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Advanced Cardiovascular Systems Incorporated
• Inventors: Webler, William E.
• Application Number:
  US11/486,828
• Publication Number:
  US 20080027350A1
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/6885 Monitoring or controlling sensor contact pressure

Abstract

Methods and apparatus for localization, diagnosis, contact or activity detection of bio-electric tissue providing improved sensitivity to the distance between a sensing electrode and bio-electric tissue and providing the means to measure the impedance of the tissue between a sensing electrode and bio-electric tissue. In accordance with the method, a controlled effective input impedance is provided to the monitor, which input impedance can be set to cause a significant portion of the bio-electric tissue signal to be dropped across the tissue between a sensing electrode and the bio-electric tissue when the two are separated by a predetermined or arbitrary distance. Various illustrative embodiments and forms of construction are disclosed.

Claims

1. A method of sensing bioactivity of bio-electric tissue comprising:

inserting a sensing electrode into the vicinity of the bio-electric tissue; and

,

monitoring the electrode voltage between the sensing electrode and a reference electrode using a monitor having a predetermined effective input impedance, the input impedance being selected to cause a significant portion of the bio-electric voltage to be dropped across the tissue between a tip of the electrode and the bio-electric tissue.

2. The method of claim 1 wherein monitoring the electrode voltage is done using a high input impedance monitor, and further comprising placing a resistance or impedance in parallel with the monitor input terminals to achieve the predetermined effective input impedance.

3. The method of claim 2 further comprising controllably disconnecting the resistance or impedance from the monitor input terminals, whereby the monitor may be used with the electrode as a high input impedance monitor.

4. The method of claim 1 wherein monitoring the electrode voltage is done using a high input impedance monitor, and further comprising placing any or a combination of resistances or impedances in parallel with the monitor input terminals to provide a selection of predetermined effective input impedances.

7. The method of claim 1 wherein the monitor is an ECG monitor.

5. The method of claim 5 further comprising controllably disconnecting the resistances or impedances from the monitor input terminals, whereby the monitor may be used with the electrode as a high input impedance monitor.

6. The method of claim 5 wherein monitoring the electrode voltage further comprises monitoring the change in electrode voltage with change in position of the electrode relative to the bio-electric tissue.

8. A method of sensing a parameter responsive to the impedance of tissue between a sensing electrode and bio-electric tissue comprising:

inserting the sensing electrode into the vicinity of the bio-electric tissue; and

,

using a monitor with a predetermined input impedance R_I, measuring the electrode voltage V_M′

between the sensing electrode and a reference electrode with a second predetermined impedance R_N coupled between the sensing electrode and the reference electrode, and measuring the electrode voltage V_M between the sensing electrode and the reference electrode with the second predetermined impedance not coupled between the sensing electrode and the reference electrode; and

,

calculating the parameter responsive to the impedance R_D of the tissue between the sensing electrode and bio-electric tissue based on the measured values of V_M and V_M′

.

9. The method of claim 8 wherein the input impedance R_I is much larger than the second impedance R_N, and the parameter responsive to the impedance R_D of the tissue between the sensing electrode and bio-electric tissue is determined based on the equation:

10. The method of claim 8 wherein the electrode voltages V_M and V_M′

are repeatedly measured, and the calculation of the parameter responsive to the impedance R_D is repeatedly updated based on updated measurements of V_M and V_M′

.

11. The method of claim 10 wherein the calculated values of the parameter responsive to the impedance R_D are displayed on a display.

12. The method of claim 11 wherein the method is carried out under processor control.

13. A method of determining a characteristic of normally bio-electric tissue comprising:

causing a sensing electrode to touch the normally bio-electric tissue; and

,

using a monitor with a predetermined input impedance R_I, measuring the electrode voltage V_M′

between the sensing electrode and a reference electrode with a second predetermined impedance R_N coupled between the sensing electrode and the reference electrode, and measuring the electrode voltage V_M between the sensing electrode and the reference electrode with the second predetermined impedance not coupled between the sensing electrode and the reference electrode; and

,

determining the characteristic of the normally bio-electric tissue from at least one of the measured values of V_M and V_M′

.

14. The method of claim 13 wherein the characteristic of the normally bio-electric tissue is the condition of the normally bio-electric tissue determined by comparing the value of V_M′

with a predetermined expected value of V_M′

.

15. The method of claim 14 wherein the method is carried out under processor control.

16. The method of claim 13 wherein the characteristic of the normally bio-electric tissue is the condition of the normally bio-electric tissue determined by comparing the difference in the values of V_M and V_M′

with a predetermined value of the difference.

17. The method of claim 16 wherein the method is carried out under processor control.

18. For use with an ECG monitor, apparatus comprising:

a sensing electrode configured for insertion in the proximity of bio-electric tissue;

an interface unit connectable to the sensing electrode and a reference electrode;

the interface unit also being connectable to at least a pair of ECG monitor inputs, the interface unit being configured to couple the sensing electrode and the reference electrode to an ECG monitor inputs and to also impose a predetermined impedance across the ECG monitor inputs.

19. The apparatus of claim 18 wherein the interface unit includes at least one switch to controllably connect and disconnect the predetermined impedance from across the ECG monitor inputs.

20. The apparatus of claim 19 wherein the switch comprises a pushbutton switch.

21. The apparatus of claim 19 wherein the at least one switch comprises a plurality of switches to controllably independently connect and disconnect any of more than one predetermined impedances from across the ECG monitor inputs.

22. The apparatus of claim 18 wherein the interface unit is permanently connected to the sensing electrode.

23. The apparatus of claim 18 wherein the interface unit is configured to alternately impose the predetermined impedance across the ECG monitor inputs and not impose the predetermined impedance across the ECG monitor inputs.

24. The apparatus of claim 23 wherein the interface unit is further configured to repeatedly calculate a parameter responsive to the impedance R_D of the tissue between the sensing electrode and bio-electric tissue as determined based on equation:

25. The apparatus of claim 24 wherein the interface unit contains a processor.

26. The apparatus of claim 24 further comprised of a display coupled to display the parameter responsive to the impedance R_D of the tissue between the sensing electrode and bio-electric tissue.

27. For use with an ECG monitor, a sensing electrode configured for insertion in the proximity of bio-electric tissue and a reference electrode, the apparatus comprising:

an interface unit connectable to the sensing electrode and the reference electrode, the interface unit also being connectable to at least a pair ECG monitor inputs, the interface unit being configured to couple the sensing electrode and the reference electrode to an ECG monitor inputs and to also impose a predetermined impedance across the ECG monitor inputs.

28. The apparatus of claim 27 wherein the interface unit includes at least one switch to controllably connect and disconnect the predetermined impedance from across the ECG monitor input.

29. The apparatus of claim 28 wherein the switch comprises a pushbutton switch.

30. The apparatus of claim 28 wherein the at least one switch comprises a plurality of switches to controllably independently connect and disconnect any of more than one predetermined impedances from across the ECG monitor input.

31. The apparatus of claim 27 wherein the interface unit is configured to alternately impose the predetermined impedance across the ECG monitor inputs and not impose the predetermined impedance across the ECG monitor inputs.

32. The apparatus of claim 31 wherein the interface unit is further configured to repeatedly calculate a parameter responsive to the impedance R_D of the tissue between the sensing electrode and bio-electric tissue as determined using the equation:

33. The apparatus of claim 32 wherein the interface unit contains a processor.

34. The apparatus of claim 32 further comprised of a display coupled to display the parameter responsive to the impedance R_D of the tissue between the sensing electrode and bio-electric tissue.