Nerve movement and status detection system and method

• US 6,500,128 B2
• Filed: 06/08/2001
• Issued: 12/31/2002
• Est. Priority Date: 06/08/2000
• Status: Expired due to Term

• Current Assignee: Nuvasive Incorporated
• Original Assignee: Nuvasive Incorporated
• Inventors: Marino, James F.
• Primary Examiner(s): Schaetzle, Kennedy
• Assistant Examiner(s): Droesch, Kristen
• Application Number:
  US09/877,713
• Publication Number:
  US 20020007129A1
• Time in Patent Office: 571 Days
• Field of Search: 128/897-898, 128/920, 600/372, 600/373, 600/546, 600/548, 600/554, 607/43, 607/46, 607/48, 607/49
• US Class Current: 600/554
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/1106 to assess neuromuscular blockade, e.g. to estimate depth of anaesthesia
• CPC Class Codes: A61B 5/389 Electromyography [EMG]
• CPC Class Codes: A61B 5/395 Details of stimulation, e.g. nerve stimulation to elicit EMG response
• CPC Class Codes: A61B 5/4041 Evaluating nerves condition
• CPC Class Codes: A61B 5/4893 Nerves
• CPC Class Codes: A61N 1/3603 Control systems

Abstract

A method and system for detecting nerve status and relative movement between a nerve and a proximity electrode. The method determines relative movement between a nerve and a proximity electrode by applying multiple signals to a calibration electrode where the energy level of each signal induces a predetermined nerve response. The method also applies multiple signals to the proximity electrode where the energy level of each signal also induces a predetermined nerve response. Based on the variation of the energy level of signals required to induce predetermined nerve responses, the method may detect relative movement between a nerve and a proximity electrode and nerve status.

Claims

1. An apparatus for determining nerve status, the apparatus including:

(a) means for applying a first electrical signal to a first conductive element where the first conductive element is located at a position where the distance between the first conductive element and the nerve is relatively constant and the first electrical signal has an energy level that induces a predetermined nerve response;

(b) means for applying a second electrical signal to a second conductive element where the second electrical signal has an energy level that induces the predetermined nerve response;

(c) means for applying a third electrical signal to the second conductive element where the third electrical signal has an energy level that induces the predetermined nerve response;

(d) means for applying a fourth electrical signal to the first conductive element where the fourth electrical signal has an energy level that induces the predetermined nerve response when the energy level of the third electrical signal is not substantially equal to the energy level of the second electrical signal; and

(e) means for determining the nerve status has changed when the energy level of the first electrical signal is not substantially equal to the energy level of the fourth electrical signal.

2. The apparatus of claim 1, wherein the first electrical signal has a current level that induces the predetermined nerve response.

3. The apparatus of claim 1, wherein the nerve response is determined from at least one EMG measured at a muscle physiologically coupled to the nerve.

4. An apparatus for determining relative movement between a nerve and a second conductive element, the apparatus including:

(a) means for applying a first electrical signal to a first conductive element where the first conductive element is located at a position where the distance between the first conductive element and the nerve is relatively constant and the first electrical signal has an energy level that induces a predetermined nerve response;

(b) means for applying a second electrical signal to the second conductive element where the second electrical signal has an energy level that induces the predetermined nerve response;

(c) means for applying a third electrical signal to the second conductive element where the third electrical signal has an energy level that induces the predetermined nerve response;

(d) means for applying a fourth electrical signal to the first conductive element where the fourth electrical signal has an energy level that induces the predetermined nerve response when the energy level of the third electrical signal is not substantially equal to the energy level of the second electrical signal; and

(e) means for determining that relative movement between the nerve and the second conductive element has occurred when the energy level of the first electrical signal is substantially equal to the energy level of the fourth electrical signal.

5. The apparatus of claim 4, wherein the first electrical signal has a current level that induces the predetermined nerve response.

6. The apparatus of claim 4, wherein the nerve response is determined from at least one EMG measured at a muscle physiologically coupled to the nerve.

7. The apparatus of claim 4, further comprising means for determining the nerve status has changed when the energy level of the first electrical signal is not substantially equal to the energy level of the fourth electrical signal.

8. An article of manufacture for use in determining nerve status, the article of manufacture comprising computer readable storage media including program logic embedded therein that causes control circuitry to perform the steps of:

(a) applying a first electrical signal to a first conductive element where the first conductive element is located at a position where the distance between the first conductive element and the nerve is relatively constant and the first electrical signal has an energy level that induces a predetermined nerve response;

(b) applying a second electrical signal to a second conductive element where the second electrical signal has an energy level that induces the predetermined nerve response;

(c) applying a third electrical signal to the second conductive element where the third electrical signal has an energy level that induces the predetermined nerve response;

(d) when the energy level of the third electrical signal is not substantially equal to the energy level of the second electrical signal applying a fourth electrical signal to the first conductive element where the fourth electrical signal has an energy level that induces the predetermined nerve response; and

(e) determining the nerve status has changed when the energy level of the first electrical signal is not substantially equal to the energy level of the fourth electrical signal.

9. The article of manufacture of claim 8, wherein the first electrical signal has a current level that induces the predetermined nerve response.

10. The article of manufacture of claim 8, wherein the nerve response is determined from at least one EMG measured at a muscle physiologically coupled to the nerve.

11. An article of manufacture for use in determining relative movement between a nerve and a second conductive element, the article of manufacture comprising computer readable storage media including program logic embedded therein that causes control circuitry to perform the steps of:

(a) applying a first electrical signal to a first conductive element where the first conductive element is located at a position where the distance between the first conductive element and the nerve is relatively constant and the first electrical signal has an energy level that induces a predetermined nerve response;

(b) applying a second electrical signal to the second conductive element where the second electrical signal has an energy level that induces the predetermined nerve response;

(c) applying a third electrical signal to the second conductive element where the third electrical signal has an energy level that induces the predetermined nerve response;

(d) when the energy level of the third electrical signal is not substantially equal to the energy level of the second electrical signal applying a fourth electrical signal to the first conductive element where the fourth electrical signal has an energy level that induces the predetermined nerve response; and

(e) determining that relative movement between the nerve and the second conductive element has occurred when the energy level of the first electrical signal is substantially equal to the energy level of the fourth electrical signal.

12. The article of manufacture of claim 11, wherein the first electrical signal has a current level that induces the predetermined nerve response.

13. The article of manufacture of claim 11, wherein the nerve response is determined from at least one EMG measured at a muscle physiologically coupled to the nerve.

14. The article of manufacture of claim 11, further comprising the step of determining the nerve status has changed when the energy level of the first electrical signal is not substantially equal to the energy level of the fourth electrical signal.

15. A method of determining nerve status comprising the steps of:

(a) applying a first electrical signal to a first conductive element where the first conductive element is located at a position where the distance between the first conductive element and the nerve is relatively constant and the first electrical signal has an energy level that induces a predetermined nerve response;

(b) applying a second electrical signal to a second conductive element where the second electrical signal has an energy level that induces the predetermined nerve response;

(c) applying a third electrical signal to the second conductive element where the third electrical signal has an energy level that induces the predetermined nerve response;

(d) when the energy level of the third electrical signal is not substantially equal to the current level of the second electrical signal applying a fourth electrical signal the first conductive element where the fourth electrical signal has an energy level that induces the predetermined nerve response; and

(e) determining the nerve status has changed when the energy level of the first electrical signal is not substantially equal to the energy level of the fourth electrical signal.

16. The method of claim 15, wherein step a) includes:

(i) placing a first conductive element at a position where the distance between the first conductive element and the nerve is relatively constant; and

(ii) applying a first electrical signal to the first conductive element where the first electrical signal has an energy level that induces a predetermined nerve response.

17. The method of claim 15, wherein the first electrical signal has a current level that induces the predetermined nerve response.

18. The method of claim 15, wherein the nerve response is determined from at least one EMG measured at a muscle physiologically coupled to the nerve.

19. A method of determining relative movement between a nerve and a second conductive element comprising the steps of:

(a) applying a first electrical signal to a first conductive element where the first conductive element is located at a position where the distance between the first conductive element and the nerve is relatively constant and the first electrical signal has an energy level that induces a predetermined nerve response;

(b) applying a second electrical signal to the second conductive element where the second electrical signal has an energy level that induces the predetermined nerve response;

(c) applying a third electrical signal to the second conductive element where the third electrical signal has an energy level that induces the predetermined nerve response;

(d) when the energy level of the third electrical signal is not substantially equal to the energy level of the second electrical signal applying a fourth electrical signal to the first conductive element where the fourth electrical signal has an energy level that induces the predetermined nerve response; and

(e) determining that relative movement between the nerve and the second conductive element has occurred when the energy level of the first electrical signal is substantially equal to the energy level of the fourth electrical signal.

20. The method of claim 19, wherein step a) includes:

(i) placing a first conductive element at a position where the distance between the first conductive element and the nerve is relatively constant; and

(ii) applying a first electrical signal to the first conductive element where the first electrical signal has an energy level that induces a predetermined nerve response.

21. The method of claim 19, wherein the first electrical signal has a current level that induces the predetermined nerve response.

22. The method of claim 19, wherein the nerve response is determined from at least one EMG measured at a muscle physiologically coupled to the nerve.

23. The method of claim 22, further comprising the step of determining the nerve status has changed when the energy level of the first electrical signal is not substantially equal to the energy level of the fourth electrical signal.