APPARATUS AND METHOD FOR THE AUTOMATED MEASUREMENT OF SURAL NERVE CONDUCTION VELOCITY AND AMPLITUDE

• US 20120101358A1
• Filed: 09/16/2011
• Published: 04/26/2012
• Est. Priority Date: 09/16/2010
• Status: Active Grant

• Current Assignee: Neurometrix, Inc.
• Original Assignee: Neurometrix, Inc.
• Inventors: Gozani, Shai N., Kong, Xuan, Williams, Michael, Fendrock, Charles, Boettcher, Bonniejean, Cryan, Marc, Herb, Glenn
• Granted Patent: US 9,173,581 B2
• Time in Patent Office: Days
• US Class Current: 600/384
• CPC Class Codes: A61B 2560/0266 for monitoring or limiting apparatus function
• CPC Class Codes: A61B 2560/028 Arrangements to prevent overuse, e.g. by counting the number of uses
• CPC Class Codes: A61B 2560/0425 Ergonomically shaped housings A61B2560/0418 takes precedence
• CPC Class Codes: A61B 2560/0468 Built-in electrodes
• CPC Class Codes: A61B 2562/0215 Silver or silver chloride containing
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• 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 5/24 Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
• CPC Class Codes: A61B 5/4041 Evaluating nerves condition

Abstract

Apparatus comprising a housing; stimulation means mounted to the housing; a biosensor releasably mounted to the housing, the biosensor comprising a plurality of electrodes for detecting a sural nerve response evoked by the stimulation means; acquisition means mounted to the housing and electrically connected to the biosensor for acquiring the sural nerve response; processing means mounted to the housing and electrically connected to the acquisition means for digitizing, processing and storing the acquired sural nerve response; calculation means mounted to the housing and electrically connected to the processing means for calculating the conduction velocity and amplitude of the processed sural nerve response; and display means mounted to the housing for displaying the sural nerve conduction velocity and amplitude; wherein the stimulation means and the biosensor are designed to be placed on a patient'"'"'s anatomy, in the vicinity of a sural nerve, by manipulating the housing.

Claims

1. Apparatus for measuring sural nerve conduction velocity and amplitude, the apparatus comprising:

a housing;

stimulation means mounted to the housing for electrically stimulating a human sural nerve;

a biosensor releasably mounted to the housing, the biosensor comprising a plurality of electrodes for detecting a sural nerve response evoked by the stimulation means;

acquisition means mounted to the housing and electrically connected to the biosensor for electrically acquiring the sural nerve response detected by the biosensor;

processing means mounted to the housing and electrically connected to the acquisition means for digitizing, processing and storing the acquired sural nerve response;

calculation means mounted to the housing and electrically connected to the processing means for calculating the conduction velocity and amplitude of the processed sural nerve response; and

display means mounted to the housing for displaying the sural nerve conduction velocity and amplitude;

wherein the stimulation means and the biosensor are designed to be placed on a patient'"'"'s anatomy, in the vicinity of a sural nerve, by manipulating the housing.

2. Apparatus according to claim 1 wherein the sural conduction velocity is the velocity to the onset of the sensory nerve action potential.

3. Apparatus according to claim 1 wherein the sural conduction velocity is the velocity to the negative peak of the sensory nerve action potential.

4. Apparatus according to claim 1 wherein the sural amplitude is the negative peak-to-positive peak amplitude of the sensory nerve action potential.

5. Apparatus according to claim 1 wherein the sural amplitude is the onset-to-negative peak amplitude of the sensory nerve action potential.

6. Apparatus according to claim 1 wherein the stimulation means comprises two conductive probes mounted to the housing.

7. Apparatus according to claim 6 wherein at least one of the said two conductive probes has a variable length which automatically adjusts to the distance between the housing and the patient'"'"'s anatomy.

8. Apparatus according to claim 1 wherein said biosensor includes at least two independent sural nerve response detection channels.

9. Apparatus according to claim 1 wherein said biosensor is releasably mounted to said housing by a foam pad that automatically adjusts to the distance between the housing and the patient'"'"'s anatomy.

10. Apparatus according to claim 9 wherein the foam pad comprises an adhesive for releasably mounting the biosensor to the foam pad.

11. Apparatus according to claim 9 wherein the foam pad comprises an adhesive for releasably mounting the foam pad to the housing.

12. Apparatus according to claim 1 wherein said apparatus comprises determination means for determining the maximal stimulus intensity.

13. Apparatus according to claim 12 wherein said determination means compares sural nerve responses at two stimulus intensities, wherein the second stimulus intensity is greater than the first stimulus intensity.

14. Apparatus according to claim 13 wherein the difference between the two stimulus intensities is 10 milliamps.

15. Apparatus according to claim 8 wherein said apparatus comprises channel determination means for determining which of the at least two independent sural nerve response recording channels is optimal.

16. Apparatus according to claim 15 wherein the optimal sural nerve response channel is that channel which has a larger amplitude and is therefore physically closest to the sural nerve.

17. Apparatus according to claim 1 wherein the processing means is configured to provide identification of the onset, negative peak, and positive peak of the sensory nerve action potential.

18. Apparatus according to claim 1 wherein said apparatus further comprises a non-contact temperature sensor mounted to the housing for measuring the patient'"'"'s skin surface temperature in the vicinity of the sural nerve.

19. Apparatus according to claim 18 wherein said calculation means use the skin surface temperature measured by the non-contact temperature sensor to compensate for temperature effects on the conduction velocity prior to the conduction velocity being displayed by the display means.

20. Apparatus according to claim 18 wherein said calculation means use the skin surface temperature measured by the non-contact temperature sensor to compensate for temperature effects on the amplitude prior to the amplitude being displayed by the display means.

21. Apparatus according to claim 18 wherein the calculation means compare said skin surface temperature measured by the non-contact temperature sensor against a predetermined minimum temperature and, if said measured temperature is below the predetermined minimum temperature, then an error message is displayed by the display means.

22. Apparatus according to claim 18 wherein the calculation means compare said skin surface temperature measured by the non-contact temperature sensor against a predetermined maximum temperature and, if said measured temperature is above the predetermined maximum temperature, then an error message is displayed by the display means.

23. Apparatus according to claim 18 wherein the calculation means computes variations of said skin surface temperature during a test and compares the computed variation against a predetermined maximum and, if the computed variation exceeds the predetermined maximum, then an error message is displayed by the display means.

24. Apparatus according to claim 1 wherein the biosensor comprises a male member and the housing comprises a female member, such that when the male member is inserted into the female member, the biosensor is electrically connected to the acquisition means.

25. Apparatus according to claim 24 wherein insertion of said male member of said biosensor into said female member of said housing is electrically detected.

26. Apparatus according to claim 1 wherein said biosensor is coded with a bit pattern.

27. Apparatus according to claim 26 wherein said biosensor is coded with a bit pattern by selectively connecting or not connecting at least two conductive members carried by the biosensor.

28. Apparatus according to claim 26 wherein said bit pattern is a single bit.

29. Apparatus according to claim 26 wherein said bit pattern varies randomly with sequential biosensors.

30. Apparatus according to claim 1 wherein a recent history of biosensor bit patterns is detected and stored by the apparatus.

31. Apparatus according to claim 30 wherein said recent history is the 24 most recent bit patterns detected by the apparatus.

32. Apparatus according to claim 30 wherein a test of randomness is applied to said recent history of biosensor bit patterns.

33. Apparatus according to claim 32 wherein, if said test of randomness indicates that the recent history of bit patterns is unlikely to be random, then the apparatus causes a warning to be displayed by the display means.

34. Apparatus according to claim 33 wherein, if said warning has been issued and a second test of randomness on a subsequent recent history of bit patterns indicates a lack of randomness, then the apparatus is rendered unusable.

35. Apparatus according to claim 34 wherein the apparatus must be reset by the manufacturer prior to further use.

36. Apparatus according to claim 32 wherein said test of randomness is the Runs-Test.

37. Apparatus according to claim 1 wherein the display means includes means for displaying an error message if said conduction velocity or amplitude cannot be determined by the calculation means.

38. Apparatus for measuring sural nerve conduction velocity and amplitude, the apparatus comprising:

a housing;

stimulation means mounted to the housing for electrically stimulating a human sural nerve;

a seat on the housing for releasably mounting a biosensor to the housing, wherein the biosensor is of the type comprising a plurality of electrodes for detecting a sural nerve response evoked by the stimulation means;

acquisition means mounted to the housing for electrical connection to a biosensor mounted on the seat and for electrically acquiring the sural nerve response detected by the biosensor;

processing means mounted to the housing and electrically connected to the acquisition means for digitizing, processing and storing the acquired sural nerve response;

calculation means mounted to the housing and electrically connected to the processing means for calculating the conduction velocity and amplitude of the processed sural nerve response; and

display means mounted to the housing for displaying the sural nerve conduction velocity and amplitude;

wherein the stimulation means and a biosensor releasably mounted on the seat are designed to be placed on a patient'"'"'s anatomy, in the vicinity of a sural nerve, by manipulating the housing.

39. Apparatus for measuring sural nerve conduction velocity and amplitude, the apparatus comprising:

a biosensor adapted to be releasably mounted to the housing of a nerve conduction testing device so that the biosensor moves in conjunction with the housing, the biosensor comprising a plurality of electrodes for detecting a sural nerve response evoked by the nerve conduction testing device and an electrical connector for electrically connecting the plurality of electrodes to the nerve conduction testing device.

40. A method for measuring sural nerve conduction velocity and amplitude, the method comprising:

releasably mounting a biosensor to the housing of a nerve conduction testing device so that the biosensor moves in conjunction with the housing;

positioning the housing of the nerve conduction testing device so that the nerve conduction testing device is positioned to electrically stimulate a human sural nerve and the biosensor is positioned to detect a sural nerve response evoked by the stimulation means;

using the nerve conduction testing device to electrically stimulate a sural nerve and to acquire the sural nerve response detected by the biosensor; and

processing the acquired sural nerve response to determine the conduction velocity and amplitude of the processed sural nerve response.

41. A fully-integrated, hand-held nerve conduction testing apparatus comprising a hand-held component and a single-patient use biosensor, wherein the biosensor is both physically and electrically connected to the hand-held component to acquire a nerve response.

42. Apparatus according to claim 41 wherein the hand-held component comprises:

a pair of stimulating electrodes, at least one of the stimulating electrodes having an adjustable height, to deliver electrical current to a test subject so as to stimulate a peripheral nerve under a varying surface anatomy.

43. Apparatus according to claim 41 wherein the hand-held component comprises a biosensor port to provide electrical connection to the biosensor which is physically attached to the hand-held component through an adhesive-coated foam pad.

44. Apparatus according to claim 41 further comprising a pair of stimulation probes that are mounted to the hand-held component, wherein at least one of the probes is spring-mounted so as to allow full and complete contact between the tip of the probe and a skin surface of uneven height.

45. Apparatus according to claim 41 further comprising a temperature sensing probe which is incorporated into the hand-held component so as to allow skin temperature measurements while performing a nerve conduction study.

46. Apparatus according to claim 41 further comprising a pad made of a flexible material so as to provide a physical interface between a rigid and flat surface of the hand-held component and the flexible and uneven surface of human body locations.

47. Apparatus according to claim 46 further comprising an adhesive coating on either side of the flexible pad to provide a secure but not permanent bond between (i) the pad and the hand-held component, and (ii) the pad and the biosensor.

48. Apparatus according to claim 41 wherein the hand-held component comprises a female connector and the biosensor comprises a male connector, and further wherein the biosensor is electrically connected to the hand-held component when the male connector is inserted into the female connector.

49. Apparatus according to claim 41 wherein the biosensor comprises multiple pairs of active electrodes.

50. Apparatus according to claim 49 wherein at least one pair of active electrodes will overlay the nerve pathway to allow effective recording of the nerve response.

51. Apparatus according to claim 50 wherein the relative positions of the electrode pairs are constructed so as to take advantage of the symmetry of nerve locations on the left and right limbs of a patient so that one consistent position of the fully-integrated, hand-held nerve conduction testing apparatus on either limb will allow one pair of electrodes to overlay the nerve on that limb.

52. Apparatus according to claim 41 wherein the biosensor comprises additional traces not connected to individual electrodes.

53. Apparatus according to claim 52 wherein the additional traces form various combinational patterns among them and are decoded by the electronics embedded in the hand-held component.

54. Apparatus according to claim 53 wherein the various combinational patterns provide a means for automatically recognizing at least one of:

proper connection of a biosensor to the hand-held component;

the type of biosensor being connected to the hand-held component; and

identification of the biosensor supplier.

55. Apparatus according to claim 41 further comprising a software control module that automatically detects the connection of a compatible biosensor with the hand-held component and initiates proper test setups based on biosensor type.

56. Apparatus according to claim 55 wherein said software control module recognizes a predetermined property of the biosensor.

57. Apparatus according to claim 56 wherein said software control module uses the predetermined property of the biosensor to determine the likelihood that the biosensor has been re-used across multiple patients through the analysis of retained biosensor property history from each biosensor connection.

58. Apparatus according to claim 41 further comprising a software control module that automatically determines the stimulus intensity level needed to evoke maximum nerve response by analyzing response waveform features and by controlling subsequent stimulus intensity levels.

59. Apparatus according to claim 41 further comprising a software control module that selects a preferred recording electrode pair based on a collection of nerve response features derived from waveforms acquired from multiple electrode pairs.

60. Apparatus according to claim 41 further comprising a software control module that predicts the number of nerve responses needed to form an averaged nerve response by estimating the noise level based on a waveform segment prior to the onset of stimulation and by estimating the amplitude of the nerve response evoked by maximal stimulation.

61. Apparatus according to claim 41 further comprising a software control module that rejects outlier waveforms when multiple waveforms are being acquired for the purpose of forming an averaged nerve response waveform.

62. Apparatus according to claim 61 wherein an individual waveform is classified as an outlier if its correlation to a running average of waveforms is below a threshold or if the waveform possesses a large percentage of extreme values based on a time-locked comparison of multiple waveforms.

63. Apparatus according to claim 41 further comprising a software control module that analyzes averaged nerve response waveform to identify key nerve response features.

64. Apparatus according to claim 63 wherein the key nerve response features comprise:

signal onset, negative peak, and positive peak.

65. Apparatus according to claim 64 wherein the key nerve response features are used to determine the nerve conduction parameters of onset conduction velocity and peak-to-peak amplitude.

66. Apparatus according to claim 41 further comprising a software control module that continuously samples temperature measurements of the skin near the nerve being stimulated.

67. Apparatus according to claim 66 wherein the software control module analyzes the temperature statistics to determine the reliability of the temperature measurement and the appropriateness of test condition.

68. Apparatus according to claim 41 further comprising a software control module that automatically compensates for measured conduction velocity as a result of low skin temperature.

69. Apparatus according to claim 68 wherein the software control module compensates for changes in conduction velocity due to skin temperature using a look-up table.

70. Apparatus according to claim 58 wherein the waveform features include amplitude, negative peak time, similarity of the waveform to a known template, and similarity of the waveform to the waveform acquired at lower stimulus intensity.

71. Apparatus according to claim 59 wherein the nerve response features include amplitude, signal-to-noise ratio, negative peak time, and waveform conformity to a known template.

72. Apparatus according to claim 59 further comprising a software control module that analyzes the frequency distribution of each electrode pair being selected as preferred pair in prior tests so as to determine which pair of electrodes were more likely to overlay the nerve.

73. Apparatus according to claim 72 wherein said software control module changes the default electrode pair to start a new test if necessary to gain the benefit of shortening the total test time and reducing the number of stimulations required.

74. Apparatus according to claim 68 wherein said software control module calculates statistics including standard deviation and median value of the temperature measurements.

75. Apparatus according to claim 74 wherein, when the standard deviation is too high, said software control module will discard test results due to poor reliability of the temperature measurements.

76. Apparatus according to claim 74 wherein, when the median temperature is below a threshold, the test results are deemed not fit for compensation and the said software control module will also discard the test results.

77. A biosensor for detecting a nerve response, the biosensor comprising:

a substrate;

a plurality of electrodes mounted to the substrate for detecting the nerve response; and

a biosensor reuse code carried by the substrate for determining reuse of the biosensor, wherein the biosensor reuse code is randomly assigned to that biosensor.

78. A biosensor according to claim 77 wherein the biosensor reuse code is encoded on the biosensor by means of electrically passive elements.

79. A biosensor according to claim 78 wherein the passive elements comprise at least two conductive members carried by the substrate, and further wherein the biosensor reuse code is encoded by selectively connecting or not connecting the at least two conductive members.

80. A kit comprising:

a plurality of biosensors for detecting nerve responses, wherein each of the biosensors comprises a substrate, a plurality of electrodes mounted to the substrate for detecting a nerve response, and a biosensor reuse code carried by the substrate for determining reuse of the biosensor;

wherein the biosensor reuse code varies randomly among the biosensors in the kit.

81. A method for determining the reuse of a biosensor in connection with a test machine, the method comprising the steps of:

connecting a biosensor to the test machine, wherein the biosensor comprises a biosensor reuse code randomly assigned to that biosensor;

identifying the biosensor reuse code associated with the connected biosensor;

comparing the identified biosensor reuse code with the biosensor reuse codes associated with the biosensors previously connected to the test machine; and

determining that the biosensor has been reused if the comparison indicates that the identified biosensor reuse code and the codes from the previously connected biosensors form a pattern that is unlikely from a random distribution of biosensor reuse codes, or determining that the biosensor has not been reused if the aforementioned pattern is likely from a random distribution of biosensor reuse codes.

82. A method for preventing the reuse of a biosensor in connection with a test machine, the method comprising the steps of:

connecting a biosensor to the test machine, wherein the biosensor comprises a biosensor reuse code randomly assigned to that biosensor;

identifying the biosensor reuse code associated with the connected biosensor;

comparing the identified biosensor reuse code with the biosensor reuse codes associated with the biosensors previously connected to the test machine; and

allowing the test to proceed if the comparison indicates that the identified biosensor reuse code is part of a random distribution of biosensor reuse codes, or preventing the test from proceeding if the comparison indicates that the identified biosensor reuse code is not part of a random distribution of biosensor reuse codes.

83. An adapter for connecting a biosensor to a testing device, the adapter comprising a biosensor reuse code carried by the adapter for determining reuse of the biosensor, wherein the biosensor reuse code is presented by the adapter to the testing device.