Bipolar cutter/coagulator - Patent Review 4590934

Claims

We claim:

1. Electrosurgical apparatus, comprising:

a bipolar electrode,

means for electronically synthesizing an aperiodic sequence of uniform-width bursts of a high frequency signal,

means for impressing substantially identical decaying amplitude envelopes on said bursts, each of said envelopes having a predetermined rate of change from a preselected initial amplitude, and

means for applying said impressed bursts to said electrode.

2. Electrosurgical apparatus according to claim 1 including means for varying the frequency of said high frequency signal within said bursts.

3. Electrosurgical apparatus according to claim 2 including means for varying the frequency of said high frequency signal between preset frequency limits.

4. Electrosurgical apparatus according to claim 3 including circuitry to cause said preset frequency limits to be 0.96 MHz and 1.04 MHz.

5. Electrosurgical apparatus according to claim 1 including means for varying the power of said sequence of bursts by varying the amplitudes of said envelopes.

6. Electrosurgical apparatus according to claim 5 including means for displaying a number representative of the power of said sequence of bursts.

7. Electrosurgical apparatus according to claim 5 including means for generating a voice signal representative of the power of said sequence of bursts.

8. Electrosurgical apparatus according to claim 1 including means for monitoring the aperiodicity of said sequence of bursts, and means for determining whether the aperiodicity is outside an acceptable limit.

9. Electrosurgical apparatus according to claim 8 including means for displaying an error message if said aperiodicity is outside said limit.

10. Electrosurgical apparatus according to claim 8 including means for sounding an error message if said aperiodicity is outside said limit.

11. Electrosurgical apparatus according to claim 1 including means for detecting whether the power of said sequence of bursts is outside an acceptable power limit, and means for automatically terminating said sequence of bursts if said power is outside the power limit.

12. Electrosurgical apparatus according to claim 11 including means for displaying an error message if said power is outside said power limit.

13. Electrosurgical apparatus according to claim 11 including means for sounding an error message if said power is outside said power limit.

14. Electrosurgical apparatus according to claim 1 including means for varying the inter-burst spacing between 11-51 microseconds.

15. Electrosurgical apparatus according to claim 1 including means for modulating said aperiodic sequence of bursts so that said bursts recur aperiodically over regularly occuring repetitive intervals of time of preselected duration separated by dead zones of preselected duration in which the bursts are absent.

16. Electrosurgical apparatus according to claim 15 including circuitry for causing said preselected intervals of time to be 6 milliseconds long and said dead zones to be 3 milliseconds long.

17. Electrosurgical apparatus according to claim 15 including means for preventing modulation of said bursts due to regular occurrence of said dead zones.

18. Electrosurgical apparatus according to claim 15 including means for preventing an abrupt rise of said burst envelope prior to decay.

19. Electrosurgical apparatus according to claim 1 including circuitry for causing the frequency of said high frequency signal to be approximately 1 MHz.

20. Electrosurgical apparatus according to claim 1 including forceps adatped for electrical connection to said means for generating said aperiodic sequence of bursts.

21. Electrosurgical apparatus according to claim 1 including means for delivering said aperiodic sequence of bursts having said decay amplitude envelopes to a load impedance, said load impedance being variable over a substantially wide range of impedances, and means for maintaining the power of said aperiodic sequence of bursts delivered to said load impedance substantially uniform over said range of impedances.

22. Electrosurgical apparatus according to claim 21 wherein said means for delivering said a periodic sequence of bursts includes a step down cup core transformer.

23. Electrosurgical apparatus comprising:

a bipolar electrode,

means for electronically synthesizing an aperiodic sequence of uniform-width bursts of a high frequency signal, means for impressing substantially identical predetermined decaying amplitude envelopes on said bursts, each of said envelopes having a predetermined rate of change from a preselected initial amplitude,

means for varying the frequency of said high frequency signal within said bursts, and

means for applying said impressed bursts to said electrode.

24. Electrosurgical apparatus according to claim 23 including means for varying the power of said sequence of bursts by varying the amplitudes of said envelopes.

25. Electrosurgical apparatus according to claim 24 including means for displaying a number representative of the power of said sequence of bursts.

26. Electrosurgical apparatus according to claim 24 including means for generating a voice signal representative of the power of said sequence of bursts.

27. Electrosurgical apparatus according to claim 23 including means for monitoring the aperiodicity of said sequence of bursts, and means for determining whether the aperiodicity is outside an acceptable limit.

28. Electrosurgical apparatus according to claim 27 including means for displaying an error message if said aperiodicity is outside said limit.

29. Electrosurgical apparatus according to claim 27 including means for sounding an error message if said aperiodicity is outside said limit.

30. Electrosurgical apparatus according to claim 23 including means for detecting whether the power of said sequence of bursts is outside an acceptable power limit and means for automatically terminating said sequence of bursts if said power is outside the power limit.

31. Electrosurgical apparatus according to claim 30 including means for displaying an error message if said power is outside said power limit.

32. Electrosurgical apparatus according to claim 30 including means for sounding an error message if said power is outside said power limit.

33. Electrosurgical apparatus according to claim 23 including means for varying the inter-burst spacing between 11-51 microseconds.

34. Electrosurgical apparatus according to claim 23 including means for modulating said aperiodic sequence of bursts so that said bursts recur aperiodically over regularly occurring repetitive intervals of time of preselected duration separated by dead zones of preselected duration in which the bursts are absent.

35. Electrosurgical apparatus according to claim 34 including circuitry for causing said preselected intervals of time to be 6 milliseconds long and said dead zones to be 3 milliseconds long.

36. Electrosurgical apparatus according to claim 34 including means for preventing modulation of said bursts due to regular occurrence of said dead zones.

37. Electrosurgical apparatus according to claim 34 including means for preventing an abrupt rise of said burst envelope prior to decay.

38. Electrosurgical apparatus according to claim 23 including circuitry for causing the frequency of said high frequency signal to be approximately 1 MHz.

39. Electrosurgical apparatus according to claim 23 including circuitry for causing the frequency of said high frequency signal to vary between the preset frequency limits.

40. Electrosurgical apparatus according to claim 39 including circuitry for causing said preset frequency limits to be 0.96 MHz and 1.04 MHz.

41. Electrosurgical apparatus according to claim 23 including forceps adapted for electrical connection to said means for generating said aperiodic sequence of bursts.

42. Electrosurgical apparatus according to claim 23 including means for delivering said aperiodic sequence of bursts having said decay amplitude envelopes to a load impedance, said load impedance being variable over a substantially wide range of impedance, and means for maintaining the power of said aperiodic sequence of bursts delivered to said load impedance substantially uniform over said range of impedances.

43. Electrosurgical apparatus according to claim 42 wherein said means for delivering said aperiodic sequence of bursts includes a step down cup core transformer.

44. Electrosurgical apparatus, comprising:

a bipolar electrode,

manually actuable means for generating a mode signal indicative of whether the appartus is to operate in a coagulate mode or in a cut mode,

means for electronically synthesizing an aperiodic sequence of uniform-width bursts of a high frequency signal when said mode signal indicates operation in the coagulate mode, said bursts having substantially identical decaying amplitude envelopes, each of said envelopes having a predetermined rate of change from a preselected initial amplitude,

means for varying the frequency of said high frequency signal within said bursts,

means for generating a continuous, substantially uniform amplitude high frequency signal when said mode signal indicates operation in the cut mode, and

means for selectably applying said bursts and said uniform aplitude high frequency signal to said electrode.

45. Electrosurgical apparatus according to claim 44 wherein said manually actuable means includes footpedal means comprising a manually actuable coag pedal for generating a mode signal indicative of operation in the coagulate mode, and a manually actuable cut pedal for generating a mode signal indicative of the cut mode, and means for generating a mode signal indicative of operation in the coagulate mode if said coag and cut pedals are simultaneously actuated.

46. Electrosurgical apparatus according to claim 44 including means for automatically setting the amplitude of said continuous high frequency signal at a first level if said mode signal indicates operation in the cut mode and for automatically setting the initial amplitude of each of said burst envelopes at a second, higher level if said mode signal indicates operation in the coagulate mode.

47. Electrosurgical apparatus according to claim 44 including manually actuable means for varying the power of said sequence of bursts or the power of said continuous high frequency signal by varying the amplitudes thereof.

48. Electrosurgical apparatus according to claim 44 including means for displaying a number representative of the power of said sequence of bursts or the power of said continuous high frequency signal.

49. Electrosurgical apparatus according to claim 48 including means for sounding said number.

50. Electrosurgical apparatus according to claim 44 including means for monitoring the aperiodicity of said sequence of bursts, and means for determining whether the aperiodicity is outside an acceptable limit.

51. Electrosurgical apparatus according to claim 50 including means for displaying an error message if said aperiodicity is outside said limit.

52. Electrosurgical apparatus according to claim 50 including means for sounding an error message if said aperiodicity is outside said limit.

53. Electrosurgical apparatus according to claim 44 including means for detecting whether the power of said sequence of bursts or the power of said continuous, high frequency signal is outside an acceptable power limit, and means for automatically terminating said sequence of bursts or said continuous, high frequency signal if said power is outside the power limit.

54. Electrosurgical apparatus according to claim 53 including means for displaying an error message if said power is outside said power limit.

55. Electrosurgical apparatus according to claim 53 including means for sounding an error message if said power is outside said power limit.

56. Electrosurgical apparatus according to claim 44 including means for varying the inter-burst spacing between 11-51 microseconds.

57. Electrosurgical apparatus according to claim 44 including means for modulating said aperiodic sequence of bursts so that said bursts recur aperiodically over regularly occurring repetitive intervals of time of preselected duration separated by dead zones of preselected duration in which the bursts are absent.

58. Electrosurgical apparatus according to claim 57 including circuitry for causing said preselected intervals of time to be 6 milliseconds long and said dead zones to be 3 milliseconds long.

59. Electrosurgical apparatus according to claim 57 including means for preventing modulation of said bursts due to regular occurrence of said dead zones.

60. Electrosurgical apparatus according to claim 57 including means for preventing an abrupt rise of said burst envelope prior to decay.

61. Electrosurgical apparatus according to claim 44 including circuitry for causing the frequency of said high frequency signal within said bursts to be approximately 1 MHz.

62. Electrosurgical apparatus according to claim 44 including circuitry for causing the frequency of said high frequency signal within said bursts to vary between preset frequency limits.

63. Electrosurgical apparatus according to claim 62 including circuitry for causing said preset frequency limits to be 0.96 MHz and 1.04 MHz.

64. Electrosurgical apparatus according to claim 44 including forcep means adapted for electrical connection to said means for generating aperiodic sequence of bursts or said continuous, high frequency signal.

65. Electrosurgical apparatus according to claim 44 including means for delivering said aperiodic sequence of bursts having said decay amplitude envelopes to a load impedance, said load impedance being variable over a substantially wide range of impedances, and means for maintaining the power of said aperiodic sequence of bursts delivered to said load impedance substantially uniform over said range of impedances.

66. Electrosurgical apparatus according to claim 65 wherein said means for delivering said aperiodic sequence of bursts includes a step down cup core transformer.

67. Electrosurgical apparatus comprising:

a bipolar electrode,

means for electronically synthesizing a sequence of aperiodic trigger pulses,

means for electronically synthesizing a burst of ramped high frequency pulses in response to each of said trigger pulses, said high frequency pulses having successive amplitudes which decrease at a predetermined rate,

means for electronically synthesizing a damped high frequency sinusoidal signal in response to each of said bursts of ramped high frequency pulses, and

means for applying said damped high frequency sinusoidal signal to said electrode.

68. Electrosurgical apparatus according to claim 67 wherein said means for generating said burst of ramped pulses includes means for generating a sequence of multiple bit digital signals of decreasing value in response to each of said trigger pulses, and means for converting each multiple bit digital signal into an analog pulse.

69. Electrosurgical apparatus according to claim 67 including means for varying the frequency of said pulses within said burst.

70. Electrosurgical apparatus according to claim 69 wherein said means for varying the frequency of said pulses includes a phase locked loop in phase coherence with said means for generating said burst of ramped pulses.

71. Electrosurgical apparatus according to claim 69 including means for varying the frequency of said ramped pulses between preset frequency limits.

72. Electrosurgical apparatus according to claim 71 including circuitry for causing said preset frequency limits to be 0.96 MHz and 1.04 MHz.

73. Electrosurgical apparatus according to claim 67 including circuitry for causing the spacing between consecutive bursts of ramped analog pulses to be based on the spacing between consecutive trigger pulses, and for causing said spacing between consecutive trigger pulses to vary between 11-51 microseconds.

74. Electrosurgical apparatus according to claim 67 wherein said means for generating said aperiodic sequence of trigger pulses includes means for generating said sequence over repetitive regularly occurring intervals of time of preselected duration separated by dead zones of preselected duration during which said trigger pulses are not generated.

75. Electrosurgical apparatus according to claim 75 including circuitry for causing said intervals of time of preselected duration to be 6 milliseconds long and said dead zones to be 3 milliseconds long,

76. Electrosurgical apparatus, comprising:

a bipolar electrode,

means for electronically synthesizing an aperiodic sequence of uniform-width bursts of a damped high frequency sinusoidal voltage signal,

means for varying the frequency of said high frequency sinusoidal voltage signal within the bursts, and

means for applying said bursts to said electrode.

77. Electrosurgical apparatus according to claim 76 wherein said means for varying said frequency includes means for varying the frequency between preset frequency limits.

78. Electrosurgical apparatus according to claim 76 wherein said means for varying said frequency includes a phase locked loop in phase coherence with said means for generating said aperiodic sequence of bursts.

79. Electrosurgical apparatus according to claim 77 including circuitry for causing said preset frequency limits to be 0.96 MHz and 1.04 MHz.

80. Electrosurgical method of coagulating vessels, tissue, or the like, comprising:

generating a power signal at bipolar forceps, said power signal comprising an aperiodic sequence of uniform-width bursts of a high frequency signal,

impressing substantially identical decaying amplitude envelope on said bursts, each of said envelopes having a predetermined rate of change from a preselected initial amplitude, and

applying said forceps to said vessels, tissue or the like.

81. Electrosurgical method according to claim 80 including varying the frequency of said high frequency signal within said bursts.

82. Electrosurgical method according to claim 81 including varying the frequency of said high frequency signal between preset frequency limits.

83. Electrosurgical method according to claim 82 wherein said preset frequency limits are 0.96 Mhz and 1.04 Mhz.

84. Electrosurgical method according to claim 80 wherein the inter-burst spacing varies between 11-51 microseconds.

85. Electrosurgical method according to claim 80 including modulating said aperiodic sequence of bursts so that said bursts recur aperiodically over regularly occurring repetitive intervals of time of preselected duration separated by dead zones of preselected duration in which the bursts are absent.

86. Electrosurgical method according to claim 85 wherein said preselected intervals of time are 6 milliseconds long and said dead zones are 3 milliseconds long.

87. Electrosurgical method of coagulating vessels, tissue and the like, comprising:

generating a power signal at bipolar forceps, said power signal comprising an aperiodic sequence of uniform-width bursts of a high frequency signal,

impressing substantially identical decaying amplitude envelope on said bursts, each of said envelopes having a predetermined rate of change from a preselected initial amplitude,

varying the frequency of said high frequency signal within said bursts, and

applying said forceps to said vessels, tissue or the like.

88. Electrosurgical method according to claim 87 including varying the frequency of said high frequency signal between preset frequency limits.

89. Electrosurgical method according to claim 88 wherein said preset frequency limits are 0.96 Mhz and 1.04 Mhz.

90. Electrosurgical method according to claim 87 wherein the inter-burst spacing varies between 11-51 microseconds.

91. Electrosurgical method according to claim 87 including modulating said aperiodic sequence of bursts so that said bursts recur aperiodically over regularly occurring repetitive intervals of time of preselected duration separated by dead zones of preselected duration in which the bursts are absent.

92. Electrosurgical method according to claim 91 wherein said preselected intervals of time are 6 milliseconds long and said dead zones are 3 milliseconds long.

BACKGROUND OF THE INVENTION

The present invention is directed to a bipolar cutter/coagulator for use in surgery. The cutter/coagulator may be employed to cut and repair tissues and is particularly required for use in microsurgery.

Prior art monopolar and bipolar coagulators used spark-gap generators to produce an aperiodic sequence of radio frequency (RF) bursts having random spike components. Such waveforms produce the best coagulation. However, the initial spike of each damped burst is much higher in voltage than the rest of the burst, as a requirement for striking the arc in the spark-gap. This high initial voltage spike is responsible for undesirable sparking at the forceps tips and produces television and monitoring equipment interference.

Electronic tube or solid state coagulators generally provide regularly occurring bursts of damped sine waves, square waves, or undamped pulses as the coagulating waveform. The regular occurrence of these waveforms increases undesirable cutting or perforation of vessels during coagulation, as a result of induced molecular resonance.

The present invention simulates the aperiodic RF bursts of the spark gap systems, but the leading voltage spike in each burst is controlled, the burst envelopes are uniform from burst to burst, and the intra-burst RF frequency is randomized. The new waveform results in the elimination of molecular resonance, hence undesirable cutting or perforation during coagulation. Control of the first spike of each burst also results in marked reduction of sparking of the forceps as well as reduction of interference with other equipment in the operating room. The waveform parameters namely, inter-burst spacing, intraburst RF frequency, and the spacing between consecutive sequence of bursts, produce the smoothest coagulation, least neuromuscular stimulation, the least pitting of the forceps as well as the least charring and sticking at the forceps, and the least vascular perforation.

Monopolar coagulators have long been used in surgery. Monopolar coagulators provide a current path from a single active electrode through the patient to a return or ground plate. The highest power per tissue volume is produced at the active electrode. The most conductive path to ground receives the highest current density, so that appreciable current can be distributed in adjacent tissues. The most conductive path can be through the blood. In a small vessel being coagulated, current can flow through the blood and coagulate the parent vessel inadvertently. Moreover, use of the monopolar coagulator under saline irrigation is not feasible, since the saline rather than the desired tissue can furnish the most conductive path to ground.

Bipolar coagulator, as compared with monopolar, utilize a pair of forcep electrodes coupled by cable to isolated power outputs. The forcep blades are insulated from each other. The power output of the bipolar coagulator is isolated from ground, so that current flow is restricted to a zone between the forcep tips. Current does not flow from either forcep tip to ground. The current path geometry depends primarily on the tip size, the angle at which the tips meet, and the conductivity of the medium in which the tips are immersed. If the forceps blades are virtually parallel and are deeply immersed in saline, there can be major shunting of current through the saline despite isolation of the power output. But if the forceps blades are bowed or angled so that the tips almost meet while the parallel portion of the blades remain well-separated, current flow is restricted to the zone between the tips with little shunting through the saline.

The power output section of a bipolar cutter/coagulator should have a low output impedance to maintain uniform power at the forcep tips over a wide range of load conditions, from dry tissue to heavily irrigated tissue. The present invention provides a stiffly regulated, isolated power output with an output impedance of approximately 5-10 ohms. By contrast, the output impedances of previously available solid state systems are approximately 50-500 ohms, and even the best spark gap coagulator has an output impedance of 40-50 ohms. The lower output impedance of the present invention facilitates its use under the constant irrigation desirable for cooling and protecting adjacent delicate vessel, tissue and nerve structures.

BRIEF SUMMARY OF THE INVENTION

A bipolar cutter/coagulator comprises a waveform generator section which generates a power output waveform comprising groups of aperiodic sequences of damped bursts of high frequency (RF) signals. Each burst decays gradually from a controlled, initial amplitude. The burst decay envelopes are uniform, that is substantially identical, from burst to burst. The inter-burst spacings are pseudo-random. The frequency of the RF signal within a burst is randomized by sweeping the frequency between preset limits.

The power output terminals of the cutter/coagulator, to which the forceps are coupled, are isolated from ground and are coupled to the secondary of a step-down transformer so as to better match the output impedance to the load impedance. An AGC loop is interposed between the power output section and the waveform generator section. The power output section and the AGC loop produce substantially uniform power output over the entire range of impedances typically encountered at the forceps during surgery.

Each damped RF burst produced by the power output section is generated based on a burst of ramped analog pulses produced by the waveform generator section. The bursts of ramped analog pulses are generated in an aperiodic sequence, the spacing between bursts being pseudo-random. The frequency of the pulses within a burst is swept about a center RF frequency between preset limits. The pulses are swept in frequency in phase coherence with the rate at which the pulse amplitudes change within a burst.

The power output level is operator selectable and may be slewed up (increased power output) or down (decreased power output) under control of a programmed microprocessor and the AGC loop. Each power setting in a slewed sequence of power settings is indicated visually on an LED display and is announced by a voice synthesizer.

Operation in the Cut or Coagulation mode is operator selectable by manipulating a foot pedal switch. Operation in either mode is announced by a unique mixture of tones. Disconnection of the foot pedal switch is automatically detected and an error message is automatically displayed on the LED display to indicate the condition. The condition is also announced by the voice synthesizer.

Loss of aperiodicity of the damped RF bursts is detected internally and the condition is displayed on the LED display while being announced by the voice synthesizer.

Other malfunctions are detected internally and are also visually displayed and announced.

An object of the invention is to produce a new power output waveform for application to forceps used in electrosurgery such that the waveform power is sufficient to produce controlled coagulation without causing inadvertent cutting, perforation or other damage to tissue.

An object of the invention is to produce a new power output waveform for a