System and Method for Return Electrode Monitoring

• US 20090198230A1
• Filed: 02/03/2009
• Published: 08/06/2009
• Est. Priority Date: 02/04/2008
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Behnke, Robert J., Wham, Robert H.
• Granted Patent: US 8,187,263 B2
• Time in Patent Office: Days
• US Class Current: 606/35
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: A61B 18/16 Indifferent or passive electrodes for grounding
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00779 Power or energy
• CPC Class Codes: A61B 2018/00869 Phase
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2090/065 for measuring contact or contact pressure

Abstract

A return electrode monitoring (“REM”) system is disclosed. The REM system includes a return electrode pad having a pair of split electrode pads and a detection circuit coupled to the pair of split electrode pads. The detection circuit and the pair of split electrode pads are adapted to resonate across a predetermined resonance range. The REM system also includes a controller coupled to the detection circuit and configured to provide a sweeping drive signal to the detection circuit across the resonance range. The detection circuit generates a drive signal in response to the sweeping drive signal and the controller determines a complex impedance across the at least one pair of split electrode pads as a function of the drive signal.

Claims

1. A return electrode monitoring system comprising:

at least one return electrode pad including at least one pair of split electrode pads;

a detection circuit operatively coupled to the at least one pair of split electrode pads, wherein the detection circuit and the at least one pair of split electrode pads are adapted to resonate across a predetermined resonance; and

a controller coupled to the detection circuit and configured to provide a sweeping drive signal to the detection circuit across a resonance range of the predetermined resonance, wherein the controller determines a complex impedance across the at least one pair of split electrode pads as a function of the drive signal.

2. A return electrode monitoring system according to claim 1, wherein the detection circuit is configured to measure a voltage, a current and the phase difference therebetween of the drive signal.

3. A return electrode monitoring system according to claim 2, wherein the controller is configured to determine a phase of the drive signal with respect to a frequency of the sweeping drive signal.

4. A return electrode monitoring system according to claim 3, wherein the controller is configured to determine a frequency shift as a function of the phase of the drive signal.

5. A return electrode monitoring system according to claim 4, wherein the controller is configured to determine a reactance across the at least one pair of split electrode pads.

6. A return electrode monitoring system according to claim 5, wherein the controller is configured to determine a resistance across the at least one pair of split electrode pads as a function of a change in amplitude of the voltage of the drive signal.

7. A return electrode monitoring system according to claim 6, wherein the controller is configured to determine a complex impedance across the at least one pair of split electrode pads as a function of the resistance and the reactance.

8. A method for monitoring a return electrode comprising the steps of:

providing a drive signal to a return electrode monitoring system including at least one return electrode pad having at least one pair of split electrode pads, the return electrode monitoring system being adapted to resonate across a predetermined resonance;

sweeping the drive signal across a resonance range of the predetermined resonance;

generating a drive signal in response to the sweeping drive signal;

measuring a phase of the drive signal; and

determining complex impedance across the return electrode monitoring system as a function of the phase of the drive signal.

9. A method for monitoring a return electrode according to claim 8, further comprising the step of:

measuring a voltage and a current of the drive signal.

10. A method for monitoring a return electrode according to claim 9, further comprising the step of:

determining a phase of the drive signal with respect to a frequency of the sweeping drive signal.

11. A method for monitoring a return electrode according to claim 10,

determining a frequency shift as a function of the phase of the drive signal.

12. A method for monitoring a return electrode according to claim 11, further comprising the step of:

determining a reactance across the at least one pair of split electrode pads.

13. A method for monitoring a return electrode according to claim 12, further comprising the step of:

determining a resistance across the at least one pair of split electrode pads as a function of a change in amplitude of the drive signal.

14. A method for monitoring a return electrode according to claim 13, further comprising the step of:

determining a complex impedance across the at least one pair of split electrode pads as a function of the resistance and the reactance.

15. A method for monitoring a return electrode according to claim 12, further comprising the step of:

mapping the reactance across the at least one pair of split electrode pads with adherence of the at least one return electrode pad.

16. An electrosurgical system comprising:

a return electrode monitoring system adapted to resonate across a predetermined resonance, the return electrode monitoring system comprising;

at least one return electrode pad including at least one pair of split electrode pads; and

a detection circuit coupled to the at least one pair of split electrode pads; and

a controller coupled to the return electrode monitoring system and configured to provide a sweeping drive signal to the return electrode monitoring system across a resonance range of the predetermined resonance, wherein the detection circuit generates a drive signal in response to the sweeping drive signal and measures a voltage, a current and a phase with respect to frequency of a corresponding drive signal of the drive signal, further wherein the controller determines a complex impedance across the at least one pair of split electrode pads as a function of the voltage, current and phase of the drive signal.

17. An electrosurgical system according to claim 16, wherein the controller is configured to determine a frequency shift as a function of the phase of the drive signal.

18. An electrosurgical system according to claim 17, wherein the controller is configured to determine a reactance across the at least one pair of split electrode pads.

19. An electrosurgical system according to claim 18, wherein the controller is configured to determine a resistance across the at least one pair of split electrode pads as a function of the change in amplitude of the drive signal.

20. An electrosurgical system according to claim 19, wherein the controller is configured to determine a complex impedance across the at least one pair of split electrode pads as a function of the resistance and the reactance.

21. A return electrode monitoring system comprising:

at least one return electrode pad including at least one pair of split electrode pads;

a detection circuit operatively coupled to the at least one pair of split electrode pads; and

a controller coupled to the detection circuit and configured to provide at least one of a step and an impulse signal to the detection circuit, wherein the detection circuit is adapted to measure a signal response to at least one of the step and the impulse signal and convert the signal response to a frequency response, the controller being further configured to determine a complex impedance across the at least one pair of split electrode pads as a function of the frequency response.