Tuned return electrode with matching inductor

• US 7,169,145 B2
• Filed: 11/21/2003
• Issued: 01/30/2007
• Est. Priority Date: 11/21/2003
• Status: Active Grant

• Current Assignee: Megadyne Medical Products Incorporated (Johnson & Johnson)
• Original Assignee: Megadyne Medical Products Incorporated (Johnson & Johnson)
• Inventors: Isaacson, James D., Borgmeier, Paul R.
• Primary Examiner(s): GIBSON, ROY DEAN
• Application Number:
  US10/719,333
• Publication Number:
  US 20050113817A1
• Time in Patent Office: 1,166 Days
• Field of Search: 606 26- 31, 606/34, 606/35, 606/41, 606/42, 607101-102
• 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 2090/065 for measuring contact or contact pressure

Abstract

An electrosurgical return electrode for use in electrosurgery. The return electrode is self-limiting and self-regulating as to maximum current and temperature rise to prevent patient trauma. An inductor is coupled in series with the return electrode. The inductor counteracts at least a portion of the impedance of the return electrode and the patient to optimize the flow of the current when the amount of contact area between the patient and the return electrode is sufficient to perform electrosurgery. The inductor may also be variable to allow the overall impedance of the electrosurgical circuit to be adjusted and tuned to work properly and safely with a particular patient and the other equipment used to perform electrosurgery. A conductor member operates with circuitry that indicates to a user when the contact area between the patient and the self-limiting member and/or return electrode is below a given threshold.

Claims

1. An electrosurgical apparatus comprising:

(a) an electrosurgical return electrode having a bulk impedance sufficient to limit the density of an electrosurgical current to safe levels; and

(b) an inductor coupled in series with the electrosurgical return electrode, wherein the inductor counteracts at least a portion of an effective impedance of the electrosurgical return electrode and a patient.

2. The electrosurgical apparatus of claim 1, wherein the inductor is selected from the group consisting of a solid state inductor, an electro-mechanical inductor, a fixed inductor, a variable inductor, solid state wave shaping circuitry or any combination thereof.

3. The electrosurgical apparatus of claim 1 wherein the inductor is selected such that the effective impedance of the electrosurgical return electrode, the patient, and the inductor falls within a range of impedances at which effective electrosurgery can be performed for a selected group of patients.

4. The electrosurgical apparatus of claim 1, wherein the effective impedance of the electrosurgical return electrode comprises a capacitive component.

5. The electrosurgical apparatus of claim 4, wherein the effective impedance of the electrosurgical return electrode further comprises a resistive component.

6. The electrosurgical apparatus of claim 4, wherein the effective impedance of the electrosurgical return electrode further comprises an inductive component.

7. The electrosurgical apparatus of claim 1, wherein the inductor optimizes the flow of the electrosurgical current by counteracting a capacitive component of the effective impedance of the electrosurgical return electrode.

8. The electrosurgical apparatus of claim 1, wherein the inductor controls the flow of electrical current by counteracting at least a portion of the effective impedance associated with the return electrode and the patient.

9. The electrosurgical apparatus of claim 8, wherein the return electrode is of a size that would normally be used on an adult sized patient and wherein the inductor counteracts the effective impedance associated with the return electrode and the patient such that electrosurgery on patients weighing less than 25 pounds can be performed effectively and safely.

10. The electrosurgical apparatus of claim 8, wherein the inductor counteracts at least a portion of the effective impedance associated with the return electrode and the patient such that the electrosurgical return electrode can be utilized for neonatal applications.

11. The electrosurgical apparatus of claim 8, wherein the inductor counteracts at least a portion of the effective impedance associated with the return electrode and the patients such that the electrosurgical return electrode can be utilized for pediatric applications.

12. The electrosurgical apparatus of claim 8, wherein the inductor counteracts at least a portion of the effective impedance associated with the return electrode and the patient such that the electrosurgical return electrode can be utilized for trans-urethral resection of the prostate applications.

13. The electrosurgical apparatus of claim 1, wherein an inductive reactance provided by the inductor counteract a portion of a capacitive reactance wherein the portion of the capacitive reactance is not needed to limit the density of the electrosurgical current to safe levels.

14. The electrosurgical apparatus of claim 13, wherein the portion of the capacitive reactance is not more than the capacitance of the effective impedance when the contact area between the patient and the return electrode is sufficient to limit the current density to safe levels without the bulk impedance.

15. An electrosurgical apparatus for use in electrosurgery wherein an electrosurgical current is utilized to cut and coagulate tissue, configured to limit the density of the electrosurgical current to safe levels so as to prevent unwanted patient burn, the electrosurgical apparatus comprising:

(a) an electrosurgical return electrode having a bulk impedance sufficient to limit the density of an electrosurgical current to safe levels, wherein the bulk impedance comprises a capacitive component; and

(b) an inductor coupled in series with the electrosurgical return electrode, the inductor being configured to increase the flow of the electrosurgical current by counteracting at least a portion of the capacitive component of the effective impedance of the electrosurgical return electrode and a patient.

16. The electrosurgical apparatus of claim 15, wherein the inductor comprises a plurality of inductors.

17. The electrosurgical apparatus of claim 16, wherein the plurality of inductors are adapted to provide variable amounts of inductance.

18. The electrosurgical apparatus of claim 15, wherein the inductor comprises a variable inductor.

19. The electrosurgical apparatus of claim 18, wherein the variable inductor is tunable.

20. The electrosurgical apparatus of claim 19, wherein the variable inductor is tunable such that that the overall effective impedance is optimized for electrosurgery when the contact area between the electrosurgical return electrode and the patient is greater than the minimum contact area needed to prevent unwanted burns.

21. The electrosurgical apparatus of claim 19, wherein the variable inductor is tunable such that the overall effective impedance is optimized for electrosurgery when the contact area is sufficient to limit the electrosurgical current density to safe levels.

22. The electrosurgical apparatus of claim 18, further comprising a logic module to tune the impedance level of the variable inductor.

23. The electrosurgical apparatus of claim 18, further comprising a sensor adapted to sense the properties of the electrosurgical current such that the capacitive component of the electrosurgical effective impedance can be determined.

24. The electrosurgical apparatus of claim 15, wherein the return electrode is of a size that would normally be used on an adult sized patient and wherein the inductor counteracts the effective impedance associated with the return electrode and the patient such that electrosurgery on pediatric patients can be performed effectively and safely.

25. The electrosurgical apparatus of claim 15, wherein the inductor counteracts at least a portion of the effective impedance associated with the return electrode and the patient such that the electrosurgical return electrode can be utilized for pediatric applications.

26. An electrosurgical apparatus for use in electrosurgery wherein an electrosurgical current is utilized to cut and coagulate tissue, and to limit the density of the electrosurgical current to safe levels so as to prevent unwanted patient burn, the electrosurgical apparatus comprising:

(a) an electrosurgical return electrode having an bulk impedance sufficient to limit the density of an electrosurgical current to safe levels, wherein the electrosurgical return electrode has an effective impedance resulting from the properties of the bulk impedance and the contact area between the patient and the return electrode, the effective impedance having a capacitive component;

(b) a variable inductor coupled in series with the electrosurgical return electrode, the variable inductor being configured to increase the flow of the electrosurgical current by counteracting the capacitive component of the effective impedance of the electrosurgical return electrode when the amount of contact area between the patient and the electrosurgical return electrode is sufficient to conduct electrosurgery; and

(c) circuitry adapted to identify the amount of capacitive reactance in an electrosurgical pathway including the electrosurgical generator and the variable inductor and tune the variable inductor to optimize the flow of the electrosurgical current by minimizing the capacitive reactance in the electrosurgical pathway.

27. The electrosurgical apparatus of claim 26, wherein the circuitry identifies the amount of capacitive reactance while electrosurgery is being performed.

28. The electrosurgical apparatus of claim 27, wherein the circuitry is adapted to tune the variable inductor while electrosurgery is being performed.

29. The electrosurgical apparatus of claim 26, wherein separate monitoring circuitry is utilized to identify the amount of capacitive reactance in the electrosurgical circuit.

30. The electrosurgical apparatus of claim 26, wherein the inductor is positioned in an electrosurgical tool.

31. The electrosurgical apparatus of claim 26, wherein the inductor is positioned in an electrosurgical generator.

32. The electrosurgical apparatus of claim 26, wherein the inductor is positioned in an electrosurgical generator.

33. The electrosurgical apparatus of claim 26, wherein the inductor is tunable such that the capacitive reactance is counteracted when the contact area between the patient and the electrosurgical electrode is sufficient to limit the electrosurgical current to safe levels.

34. The electrosurgical apparatus of claim 26, wherein the inductor is configured to maintain the impedance in the electrosurgical pathway above a level below which would result in unsafe electrosurgical current densities when the contact area between the patient and the electrosurgical electrode is insufficient to limit the electrosurgical current densities to safe levels without the bulk impedance.

35. The electrosurgical apparatus of claim 26, wherein the return electrode is of a size that would normally be used on an adult sized patient and wherein the inductor counteracts the effective impedance associated with the return electrode and the patient such that electrosurgery on pediatric patients can be performed effectively and safely.

36. The electrosurgical apparatus of claim 26, wherein the inductor counteracts at least a portion of the effective impedance associated with the return electrode and the patient such that the electrosurgical return electrode can be utilized for pediatric applications.

37. An electrosurgical apparatus for use in electrosurgery wherein an electrosurgical current is utilized to cut and coagulate tissue and to limit the density of the electrosurgical current to safe levels so as to prevent unwanted patient burn, the electrosurgical apparatus comprising:

(a) an electrosurgical return electrode adapted to contact a patient wherein the combination of the return electrode and the patient in contact with the return electrode comprises a capacitive reactance sufficient to limit the density of an electrosurgical current to safe levels, when the electrode is at least partially in contact with a patient;

(b) an inductor coupled in series with said electrode, the inductor being configured to increase the flow of the electrosurgical current by utilizing the phase angle and magnitude of the inductance to reduce the capacitive reactance of the electrode.

38. The electrosurgical apparatus of claim 37, wherein the properties of the inductor are selected based on the capacitive reactance of the electrode when a patient is in sufficient contact with the electrosurgical return electrode to limit the density of the electrosurgical current to safe levels.

39. The electrosurgical apparatus of claim 37, wherein said electrosurgical return electrode comprises electrically conducting material having an effective bulk impedance equal to or greater than about 4,000 Ω

•

cm.

40. The electrosurgical apparatus of claim 37, wherein said electrosurgical return electrode comprises an electrically conducting material having an effective bulk impedance equal to or greater than about 10,000 Ω

•

cm.

41. The electrosurgical apparatus of claim 37, wherein the capacitive reactance is sufficient to limit the electrosurgical current density to less than 100 millamperes per centimeter.

42. The electrosurgical apparatus of claim 37, wherein the return electrode is of a size that would normally be used on an adult sized patient and wherein the inductor counteracts the effective impedance associated with the return electrode and the patient such that electrosurgery on pediatric patients can be performed effectively and safely.

43. The electrosurgical apparatus of claim 37, wherein the inductor counteracts at least a portion of the effective impedance associated with the return electrode and the patient such that the electrosurgical return electrode can be utilized for pediatric applications.

44. An electrosurgical return electrode adapted to prevent unwanted patient burns comprising:

a semi-insulating element having a bulk impedance sufficient to prevent a patient burn when a contact area between a patient and the semi-insulating element is below a given threshold;

an electrically conductive member coupled to the semi-insulating element, the conductive member cooperating with circuitry that identifies the area of contact between the patient and the semi-insulating element and if the area of contact is below a given threshold; and

an inductor coupled in series with the bulk impedance wherein the inductor is configured to counteract at least a portion of an effective impedance caused when the patient is in limited contact with the electrosurgical return electrode.

45. The return electrode of claim 44, wherein the electrically conductive member comprises a split plate.

51. The electrosurgical return electrode of claim 44, wherein the return electrode is of a size that would normally be used on an adult sized patient and wherein the inductor counteracts the effective impedance associated with the return electrode and the patient such that electrosurgery on pediatric patients can be performed effectively and safely.

52. The electrosurgical return electrode of claim 44, wherein the inductor counteracts at least a portion of the effective impedance associated with the return electrode and the patient such that the electrosurgical return electrode can be utilized for pediatric applications.

46. An electrosurgical return electrode adapted to prevent unwanted patient burns comprising:

a semi-insulating element having a bulk impedance sufficient to prevent a patient burn when a contact area between a patient and the semi-insulating element is below a given threshold;

an electrically conductive member coupled to the semi-insulating element, the conductive member cooperating with circuitry that identifies the area of contact between the patient and the semi-insulating element and if the area of contact is below a given threshold; and

an inductor coupled in series with the bulk impedance wherein the inductor is configured to counteract at least a portion of an effective impedance caused when the patient is in limited contact with the electrosurgical return electrode.

47. The return electrode of claim 46, wherein the electrically conductive member comprises a split plate.

48. The return electrode of claim 47, wherein the split plate is configured such that the area of contact between the patient and the semi-insulating element can be measured notwithstanding the total surface area of the semi-insulating element and the portion of semi-insulating element the patient is contacting.

49. The return electrode of claim 48, wherein the split plate comprises a split plate member having a first conductor and a second conductor interwoven in a lattice structure.

50. The return electrode of claim 49, wherein the circuitry measures the impedance between the first conductor and the second conductor.

53. A return electrode having a surface adapted to be positioned directly on a patient, the return electrode comprising:

a first conductor;

a second conductor interwoven with the first conductor to create a lattice structure where the lattice structures promotes uniform flow of current over the surface of the return electrode, wherein the first and second conductors comprise a bulk impedance sufficient to prevent a patient burn when a contact area between a patient and the first and second conductors is below a given threshold; and

an inductor coupled in series with the bulk impedance wherein the inductor is configured to counteract at least a portion of an effective impedance caused when the patient is in contact with the first and second conductors.

54. The return electrode of claim 53, wherein the inductor is selected from the group consisting of a solid state inductor, an electro-mechanical inductor, a fixed inductor, a variable inductor, solid state wave shaping circuitry or any combination thereof.

55. The return electrode of claim 53, wherein the inductor is selected such that the effective impedance falls within a range of impedances at which effective electrosurgery can be performed for a selected group of patients.

56. The return electrode of claim 53, wherein the effective impedance comprises a capacitive component.

57. The return electrode of claim 56, wherein the effective impedance further comprises a resistive component.

58. The return electrode of claim 56, wherein the effective impedance further comprises an inductive component.

59. The return electrode of claim 53, wherein the inductor counteracts a capacitive component of the effective impedance of the electrosurgical return electrode.

60. The return electrode of claim 53, wherein the return electrode is of a size that would normally be used on an adult sized patient and wherein the inductor counteracts the effective impedance caused by the patient being in contact with the first and second conductors such that electrosurgery on pediatric patients can be performed effectively and safely.

61. The return electrode of claim 53, wherein the inductor counteracts at least a portion of the effective impedance caused by the patient being in contact with the first and second conductors such that the electrosurgical return electrode can be utilized for pediatric applications.

62. An electrosurgical apparatus comprising:

(a) an electrosurgical return electrode having a bulk impedance sufficient to limit the density of an electrosurgical current to safe levels; and

(b) a reactance coupled in series with the electrosurgical return electrode, the reactance being configured to increase the flow of the electrosurgical current by counteracting a portion of an effective impedance caused when a patient is in contact with the electrosurgical return electrode.

63. The electrosurgical apparatus of claim 62, wherein the effective impedance includes an inductive component.

64. The electrosurgical apparatus of claim 63, wherein the reactance is a capacitor coupled in series with the electrosurgical return electrode configured to counteract at least a portion of the inductive component.

65. The electrosurgical apparatus of claim 64, wherein the capacitor is configured to not reduce the combination of the effective impedance and the reactance to a level that would allow unsafe electrosurgical current densities when the contact area between the patient and the electrosurgical return electrode is insufficient to limit the electrosurgical current densities to safe levels without the bulk impedance.

66. The electrosurgical apparatus of claim 63, further comprising monitoring circuitry to identify the inductive component of the effective impedance.

67. The electrosurgical apparatus of claim 62, wherein the reactance is selected such that the combination of the effective impedance and the reactance falls within a range of impedance at which effective electrosurgery can be performed for a selected group of patients.

68. The electrosurgical apparatus of claim 62, wherein the return electrode is of a size that would normally be used on an adult sized patient and wherein the inductor counteracts the effective impedance associated with the return electrode and the patient such that electrosurgery on pediatric patients can be performed effectively and safely.

69. The electrosurgical apparatus of claim 62, wherein the inductor counteracts at least a portion of the effective impedance associated with the return electrode and the patient such that the electrosurgical return electrode can be utilized for pediatric applications.