Nerve stimulator and method

• US 20050267545A1
• Filed: 05/25/2004
• Published: 12/01/2005
• Est. Priority Date: 05/25/2004
• Status: Active Grant

• Current Assignee: Nervonix, Inc.
• Original Assignee: Nervonix, Inc.
• Inventors: Cory, Philip C.
• Granted Patent: US 7,212,865 B2
• Time in Patent Office: Days
• US Class Current: 607/48
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/4041 Evaluating nerves condition
• CPC Class Codes: A61N 1/36017 with leads or electrodes penetrating the skin
• CPC Class Codes: A61N 1/36021 for treatment of pain

Abstract

This invention presents a device, and the method it implements, which is an improvement in the design of nerve stimulators. Like conventional stimulators, it uses a percutaneous, insulated needle for the performance of therapeutic interventions targeting nerves. The improvement comprises offering an option for either constant current or constant voltage, offering a choice of waveform parameters, controlling a pulse generator, supplying a second background waveform, measuring the current and voltage applied to the tissue, computing further electrical characteristics, dynamically adjusting circuit components to ensure a desirable waveform applied to the tissue, and displaying measured and computed electrical characteristics of the tissue. The object is improved positioning of a needle tip near a nerve or nerve plexus for regional anesthesia, pain management, and other medical purposes.

Claims

1. A device for improved nerve stimulation via a percutaneous insulated needle for the performance of therapeutic interventions targeting nerves within living tissue, comprising

a needle electrode, which is percutaneous and is insulated from the tissue except at the tip of the electrode;

a return electrode;

a pulse generator;

a background waveform generator;

a pulse conditioning circuit in series with the electrical path between the two electrodes through the tissue;

sensors to detect electrical characteristics of the waveforms generated by the two generators; and

a controller for acquiring user parameter choices, for acquiring real-time measurements of the pulse and waveform, for calculating other waveform characteristics from the measurements, for calculating tissue characteristics from the waveform characteristics, and for adjusting parametric characteristics of generators and the conditioning circuit, to produce a desired waveform across the electrodes and to generate various measured and calculated values for the benefit of the practitioner who is advancing the needle electrode into the tissue;

wherein the controller is programmed to adjust the parametric characteristics of the generators and the conditioning circuit in order to produce a desirable waveform across the electrodes by sampling the electrical characteristics of the waveforms using the sensors.

2. The device of claim 1, wherein the return electrode is a superficial, gel electrode.

3. The device of claim 1, wherein the pulse generator maintains an adjustable, specified current amplitude level across a varying impedance.

4. The device of claim 3, wherein the current amplitude level of the pulse generator may be in the range of 0 to 5 milliamperes.

5. The device of claim 1, wherein the pulse generator maintains an adjustable, specified voltage amplitude level across a varying impedance.

6. The device of claim 5, wherein the wherein the voltage amplitude level of the pulse generator may in the range of 0 to 24 volts.

7. The device of claim 1, wherein the pulse generator operates at a pulse frequency between 1 and 5 Hertz.

8. The device of claim 1, wherein the pulse generator generates square wave pulses.

9. The device of claim 8, wherein the pulse generator generates pulses with a duration of 0.1 to 3 milliseconds.

10. The device of claim 1, wherein the frequency of the background generator may be selected from within a range of 500 to 10000 Hertz.

11. The device of claim 1, wherein the background waveform generator generates a waveform with a specified current amplitude across a varying impedance.

12. The device of claim 1, the output of the background waveform generator has a maximum current of 100 microamperes.

13. The device of claim 1, wherein the output of the background generator is directed across the electrodes.

14. The device of claim 1, wherein the output of the background generator is a sinusoidal waveform with a constant offset.

15. The device of claim 1, wherein the pulse conditioning circuit comprises a capacitor in parallel with a resistor.

16. The device of claim 1, wherein the pulse conditioning circuit includes a variable capacitor.

17. The device of claim 1, wherein the pulse conditioning circuit includes a variable resistor.

18. The device of claim 1, wherein a sensor utilizes an analog-to-digital converter.

19. The device of claim 1, wherein a sensor measures the real-time voltage at least 10 times faster than the highest frequency of the generators and with at least 8 bits of digital resolution.

20. The device of claim 1, wherein a sensor measures the real-time current at least 10 times faster than the highest frequency of the generators and with at least 8 bits of digital resolution.

21. The device of claim 1, wherein the waveform of the background generator is maintained at a specified voltage amplitude.

22. The device of claim 1, wherein the waveform of the background generator is maintained at a specified current amplitude.

23. The device of claim 1, wherein the tissues is animal tissue.

24. The device of claim 1, wherein the tissue is the tissue of a human being.

25. The device of claim 1, wherein the controller is a programmed electronic computer with digital inputs and outputs.

26. The device of claim 1, wherein the display graphs the shape of the waveform applied across the electrodes.

27. The device of claim 1, which further comprises an indicator, which indicates the proximity of the tip of the needle electrode to a nerve.

28. The device of claim 27, wherein the indicator generates an audible tone.

29. The device of claim 27, wherein the indicator is a visual display.

30. The device of claim 29, wherein the visual display displays the waveform voltage.

31. The device of claim 29, wherein the visual display displays the waveform current.

32. The device of claim 29, wherein the visual display displays the calculated impedance of the tissue between the electrodes.

33. The device of claim 29, wherein the visual display displays the pulse duration.

34. The device of claim 29, wherein the visual display displays the frequency of the pulses

35. The device of claim 27, wherein the indicator indicates error status.

36. An improved nerve stimulator for the performance of therapeutic interventions and targeting nerves within living tissue, which stimulator comprises a needle electrode, a return electrode, a pulse generator, at least one sensor of an electrical characteristic, and an indicator of the value measured by the sensor, where the improvement comprises

a pulse conditioning circuit in series with the electrical path between the two electrodes through the tissue;

an improved pulse generator;

a second waveform generator;

a controller for acquiring user parameter choices, for acquiring real-time measurements of the waveform, for calculating at least one waveform characteristic from the measurements, for calculating tissue characteristics from the characteristic, and for adjusting parametric input values for the generators and the conditioning circuit in order to produce a desired waveform across the electrodes, and to generate various measured and calculated values for the benefit of the practitioner who is advancing the needle electrode into the tissue.

37. The improvement of claim 36, wherein the pulse conditioning circuit comprises a capacitor in series with a resistor.

38. The improvement of claim 36, wherein the pulse conditioning circuit includes a variable capacitor.

39. The improvement of claim 36, wherein the pulse conditioning circuit includes a variable resistor.

40. The improvement of claim 36, wherein the improved pulse generator maintains a specified current amplitude level across the electrodes.

41. The improvement of claim 40, wherein the current amplitude level of the improved pulse generator may be in the range of 0 to 5 milliamperes.

42. The improvement of claim 36, wherein the improved pulse generator maintains a specified voltage amplitude level across the electrodes.

43. The improvement of claim 42, wherein the voltage amplitude level of the improved pulse generator may in the range of 0 to 24 volts.

44. The improvement of claim 36, wherein the improved pulse generator operates at a pulse frequency between 1 and 5 Hertz.

45. The improvement of claim 36, wherein the improved pulse generator generates square pulses.

46. The improvement of claim 36, wherein the improved pulse generator generates pulses with a duration of 0.1 to 3 milliseconds.

47. The improvement of claim 36, wherein the frequency of the second generator may be selected from within a range of 500 to 10000 Hertz.

48. The improvement of claim 36, wherein the second generator generates a waveform with a fixed current amplitude across a varying impedance.

49. The improvement of claim 36, wherein the second generator generates a waveform with a maximum current of 100 microamperes.

50. The improvement of claim 36, wherein the output of the second generator is directed directly across the electrodes.

51. The improvement of claim 36, wherein the output of the second generator is a sinusoidal waveform with a constant offset.

52. The improvement of claim 36, wherein the waveform of the pulse generator is a square wave.

53. The improvement of claim 36, wherein the waveform of the second generator is maintained at a specified voltage amplitude across a varying impedance.

54. The improvement of claim 36, wherein the waveform of the second generator is maintained at a specified current amplitude across a varying impedance.

55. The improvement of claim 36, wherein the tissue is animal tissue.

56. The improvement of claim 36, wherein the tissue is the tissue of a human being.

57. The improvement of claim 36, wherein the controller is an electronic computer with digital inputs and outputs.

58. The improvement of claim 36, wherein the display graphically displays the shape of the waveform across the electrodes.

59. The improvement of claim 36, wherein the indicator may produce an audible sound.

60. The improvement of claim 36, wherein the indicator may be a visual display.

61. The improvement of claim 60, wherein the display displays the waveform voltage.

62. The improvement of claim 60, wherein the display displays the waveform current.

63. The improvement of claim 60, wherein the display displays the calculated impedance of the tissue between the electrodes.

64. The improvement of claim 60, wherein the display displays the pulse duration.

65. The improvement of claim 60, wherein the display displays the frequency of the pulses.

66. The improvement of claim 59, wherein the indicator indicates error status.

67. A method of improved nerve stimulation via a percutaneous insulated needle for the performance of therapeutic interventions targeting nerves within living tissue, comprising steps of

attaching a return electrode;

inserting a needle electrode percutaneously into tissue, where the needle electrode is insulated from the tissue except at the tip of the electrode;

adjusting the characteristics of a pulse conditioning circuit in series with the electrical path between the two electrodes through the tissue;

applying a pulse waveform of a specified shape and specified amplitude to the electrodes;

measuring an electrical characteristic of the waveform applied to the electrodes;

calculating a tissue characteristic based on the measured electrical characteristic of the waveform; and

displaying a selected subset of the following;

the user-selected parameters for the generators and other user options, the electrical characteristic, the tissue characteristic, and the location of the nerve.

68. The method of claim 67, wherein the return electrode is a superficial gel electrode.

69. The method of claim 67, wherein the pulse conditioning circuit comprises a capacitor in series with a resistor.

70. The method of claim 67, wherein the pulse conditioning circuit includes a variable capacitor.

71. The method of claim 67, wherein the pulse conditioning circuit includes a variable resistor.

72. The method of claim 67, wherein the specified shape is a square wave.

73. The method of claim 67, wherein the specified amplitude is a current amplitude across a varying impedance.

74. The method of claim 67, wherein the specified amplitude is a voltage amplitude across a varying impedance.

75. The method of claim 67, wherein a pulse generator applies a waveform across a series circuit comprising the pulse conditioning circuit and the tissue between the electrodes.

76. The method of claim 67, wherein the calculating step computes the total impedance of the tissue.

77. The method of claim 67, wherein the calculating step computes the resistance and reactance of the impedance of the tissue.

78. The method of claim 67, wherein the displayed characteristic is impedance.

79. The method of claim 67, wherein the displaying step displays the values of the measured electrical characteristic.

80. The method of claim 67, wherein the displaying step displays the estimated distance to the nerve.

81. The method of claim 67, wherein the displaying step displays the shape of the waveform applied across the electrodes.