TRANSCUTANEOUS ELECTRICAL NERVE STIMULATOR WITH AUTOMATIC DETECTION OF USER SLEEP-WAKE STATE

• US 20140309709A1
• Filed: 04/15/2014
• Published: 10/16/2014
• Est. Priority Date: 04/15/2013
• Status: Active Grant

• Current Assignee: Neurometrix, Inc.
• Original Assignee: Neurometrix, Inc.
• Inventors: Gozani, Shai, Kong, Xuan, Ferree, Tom
• Granted Patent: US 10,279,179 B2
• Time in Patent Office: Days
• US Class Current: 607/46
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61B 5/4809 Sleep detection, i.e. determining whether a subject is asleep or not
• CPC Class Codes: A61N 1/0456 Specially adapted for transcutaneous electrical nerve stimulation [TENS]
• CPC Class Codes: A61N 1/36021 for treatment of pain
• CPC Class Codes: A61N 1/3603 Control systems

Abstract

Apparatus for transcutaneous electrical nerve stimulation in a user, the apparatus comprising:

• • a housing;
  • stimulation means for electrically stimulating at least one nerve;
  • an electrode releasably mounted to the housing and connectable to the stimulation means for electrical stimulation of the at least one nerve;
  • monitoring means for monitoring the user'"'"'s body orientation and movement;
  • analysis means for analyzing said orientation and movement; and
  • control means for controlling the output of the stimulation means in response to said analysis of said orientation and movement.

Claims

1. Apparatus for transcutaneous electrical nerve stimulation in a user, the apparatus comprising:

a housing;

stimulation means for electrically stimulating at least one nerve;

an electrode releasably mounted to the housing and connectable to the stimulation means for electrical stimulation of the at least one nerve;

monitoring means for monitoring the user'"'"'s body orientation and movement;

analysis means for analyzing said orientation and movement; and

control means for controlling the output of the stimulation means in response to said analysis of said orientation and movement.

2. Apparatus according to claim 1 wherein the body orientation and movement are used to determine the user'"'"'s sleep-wake state.

3. Apparatus according to claim 1 wherein the body orientation and movement are used to estimate the user'"'"'s activity level.

4. Apparatus according to claim 1 wherein the body orientation and movement are used to classify the user'"'"'s activity type.

5. Apparatus according to claim 1 wherein said monitoring of the user'"'"'s body orientation and movement is accomplished with at least one accelerometer.

6. Apparatus according to claim 5 wherein the axis directions of the accelerometer are known and fixed with respect to a specific anatomical location of the user when a tight mechanical coupling is established between the monitoring means and the anatomical location.

7. Apparatus according to claim 6 wherein the anatomical location is the upper calf area of the user.

8. Apparatus according to claim 6 wherein the required tight mechanical coupling between the monitoring means and the anatomical location is created when a strap holds the housing, monitoring means, and electrode at the anatomical location.

9. Apparatus according to claim 8 wherein the strap includes a tension gauge to measure tightness between the monitoring means and the anatomical location.

10. Apparatus according to claim 9 wherein the tight mechanical coupling between the monitoring means and the anatomical location is confirmed through a comparison of the tension measured by the tension gauge with a tension threshold.

11. Apparatus according to claim 8 wherein the tight mechanical coupling between the monitoring means and the anatomical location is confirmed by detecting contact of said electrode with the skin of the user.

12. Apparatus according to claim 5 wherein the analysis means maps acceleration measurements from the accelerometer to the user'"'"'s body orientation and body movement.

13. Apparatus according to claim 12 wherein the user'"'"'s body orientation is determined by analyzing the projection value of the earth gravity acceleration vector on at least one axis of the accelerometer.

14. Apparatus according to claim 13 wherein the estimated projection value of the earth gravity acceleration vector is a function of at least one projection measurement from the accelerometer over an epoch.

15. Apparatus according to claim 14 wherein the function is an average.

16. Apparatus according to claim 14 wherein the length of an epoch is one minute.

17. Apparatus according to claim 14 wherein the projection value is expressed as an angle between said accelerometer axis and the horizontal plane.

18. Apparatus according to claim 17 wherein the absolute value of the angle is compared with a threshold in order to determine the user'"'"'s body orientation as upright or recumbent.

19. Apparatus according to claim 18 wherein the user'"'"'s body orientation is considered to be recumbent if the absolute value of the angle is below the threshold.

20. Apparatus according to claim 18 wherein the angle threshold has a target value and an offset.

21. Apparatus according to claim 20 wherein the target value is 30°

.

22. Apparatus according to claim 20 wherein the target value is 45°

.

23. Apparatus according to claim 20 wherein the target value is a function of at least one real world condition.

24. Apparatus according to claim 23 wherein the at least one real world condition comprises at least one from the group consisting of an ambient light condition, the time of the day, and a recent sleep time period pattern of the user.

25. Apparatus according to claim 20 wherein the offset has a hysteresis component to eliminate rapid orientation changes to and from the recumbent position.

26. Apparatus according to claim 25 wherein the hysteresis component is 2.5 degrees.

27. Apparatus according to claim 20 wherein the offset comprises a confidence interval component which is proportional to the standard error of the estimated mean value of the projection.

28. Apparatus according to claim 20 wherein the offset is positive if the prior user position is recumbent.

29. Apparatus according to claim 20 wherein the offset is negative if the prior user position is upright.

30. Apparatus according to claim 12 wherein the body orientation is determined according to the majority of the body orientations of at least one most recent epochs.

31. Apparatus according to claim 12 wherein the body orientation is determined according to whether the user'"'"'s body orientation remains the same for at least one most recent epoch.

32. Apparatus according to claim 1 wherein the analyzing means classifies the user state as “

in-bed”

if the body orientation is recumbent.

33. Apparatus according to claim 12 wherein the body movement measure is a function of at least one body activity level count derived from the acceleration measurements.

34. Apparatus according to claim 33 wherein the function is the median function.

35. Apparatus according to claim 33 wherein the function is the weighted average function.

36. Apparatus according to claim 33 wherein the number of body activity level counts is 20.

37. Apparatus according to claim 33 wherein each body activity level count is an average of an accelerometer signal over an epoch.

38. Apparatus according to claim 37 wherein an epoch is one minute in duration.

39. Apparatus according to claim 37 wherein the accelerometer signal comprises an instantaneous acceleration signal.

40. Apparatus according to claim 39 wherein the instantaneous acceleration signal is the square root of summation of squared values of filtered accelerometer measurements along each of its three axes.

41. Apparatus according to claim 40 wherein the accelerometer measurements are filtered by a band-pass filter.

42. Apparatus according to claim 1 wherein the analyzing means classify the user state as “

low activity”

if the user'"'"'s body movement measure is below a threshold value.

43. Apparatus according to claim 42 wherein the threshold value is 0.1 g.

44. Apparatus according to claim 1 wherein the analyzing means classify the user state as sleep if the user is “

in-bed” and

has “

low activity”

.

45. Apparatus according to claim 1 wherein the control means modifies the stimulation means output when the user is determined to be “

in-bed”

or is in sleep state.

46. Apparatus according to claim 1 wherein the control means re-starts stimulation means after a timer is expired when the user is in sleep state.

47. Apparatus according to claim 46 wherein the timer defines the interval when the stimulation means is off.

48. Apparatus according to claim 47 wherein the timer duration is one hour.

49. Apparatus according to claim 47 wherein the timer duration is shortened if an increase in the user'"'"'s body movement measure is observed in multiple periods during which the stimulation means are off.

50. Apparatus according to claim 1 wherein the control means modifies the operation of the stimulation means when the “

low activity”

status changes from on to off and the “

in-bed”

status is on.

51. Apparatus according to claim 50 wherein the modification to the stimulation means adjusts stimulation intensity level.

52. Apparatus according to claim 50 wherein the modification to the stimulation means adjusts stimulation pulse frequency.

53. A method for controlling transcutaneous electrical nerve stimulation based on a user'"'"'s body orientation and movement status, the method comprising the steps of:

applying the transcutaneous electrical nerve stimulation device to the user'"'"'s body to create a tight mechanical coupling between the device and the user'"'"'s body;

acquiring data from an accelerometer mounted to the stimulation device that measures the user'"'"'s body orientation and movement;

analyzing the accelerometer data to determine the user'"'"'s body orientation and movement;

determining the user'"'"'s body orientation and body movement status; and

modifying the stimulation output pattern based on the user'"'"'s body orientation and body movement status.

54. A method according to claim 53 wherein user body orientation and movement status is used to determine the user'"'"'s sleep-wake state.

55. A method according to claim 54 wherein the sleep-wake state is used to modify the stimulation intensity.

56. A method according to claim 53 wherein the mechanical coupling is accomplished with a strap holding the device in place at a specific anatomical location.

57. A method according to claim 53 wherein the mechanical coupling is confirmed through electrode on-skin detection.

58. A method according to claim 53 wherein analyzing of the accelerometer data includes mapping the accelerometer'"'"'s three axes to the user body orientation.

59. A method according to claim 53 wherein analyzing of the accelerometer data includes determining the fraction of the earth gravitational acceleration projected to one or more axes of the accelerometer.

60. A method according to claim 59 wherein projection is measured by the angle between said axes and the horizontal plane.

61. A method according to claim 60 wherein the angle is estimated by averaging multiple samples of the earth gravitational acceleration projection.

62. A method according to claim 61 wherein the averaging is over samples acquired within a time epoch.

63. A method according to claim 62 wherein the duration of an epoch is one minute.

64. A method according to claim 53 wherein determining the user'"'"'s body orientation includes the comparison of (i) the estimated angle of the y-axis of the accelerometer with the horizontal plane, and (ii) a pre-determined angle threshold.

65. A method according to claim 53 wherein the user'"'"'s body orientation is considered to be recumbent if the absolute value of the estimated angle is below the angle threshold.

66. A method according to claim 65 wherein the user'"'"'s body orientation status is “

in-bed”

if a majority of determinations of body orientation are considered to be recumbent within a fixed number of immediate past epochs.

67. A method according to claim 65 wherein the user'"'"'s body orientation status is considered to be “

in bed”

if a fixed percentage of the determinations of body orientation are considered to be recumbent within a fixed number of immediate past epochs.

68. A method according to claim 53 wherein analyzing of the accelerometer data includes determining the instantaneous acceleration value from filtered accelerometer data.

69. A method according to claim 68 wherein a band-pass filter is used to filter accelerometer data between 0.5 Hz and 12 Hz.

70. A method according to claim 53 wherein analyzing of the accelerometer data includes a weighted summation of the instantaneous acceleration observation over an epoch to form a movement activity count.

71. A method according to claim 53 wherein analyzing of the accelerometer data include mapping multiple body movement activity counts to a body movement measure.

72. A method according to claim 71 wherein the mapping is a weighted average function.

73. A method according to claim 72 wherein the weighted average gives a larger weight to the more recent activity counts.

74. A method according to claim 53 wherein determining the user'"'"'s body movement status includes comparison of the estimated body movement measure and a movement threshold.

75. A method according to claim 74 wherein the user body movement is considered to be in “

low activity”

status if the body movement measure is below the movement threshold.

76. A method according to claim 53 wherein the stimulation modification is to reduce stimulation intensity level by a fixed amount if the user body orientation status is “

in-bed”

.

77. A method according to claim 53 wherein the stimulation modification is to reduce stimulation intensity level by a fixed percentage if the user body orientation status is “

in-bed”

.

78. A method according to claim 53 wherein the stimulation modification is to restart stimulation after a fixed time window without any intervention from the user if the user body orientation status is “

in-bed” and

body movement is in “

low activity”

status.

79. Apparatus for transcutaneous electrical nerve stimulation in a user, said apparatus comprising:

a housing;

stimulation means within the housing for electrically stimulating nerves;

monitoring means within the housing for measuring orientation and activity levels of the said user;

control means for controlling the electrical stimulation provided to the skin of the user when the monitoring means determines that the user body orientation and activity levels meet at least one predetermined condition.

80. A method for applying transcutaneous electrical nerve stimulation to a user, said method comprising:

applying stimulation means and an accelerometer sensor to the the user'"'"'s body;

delivering stimulation current to the user to stimulate one or more nerves;

analyzing accelerometer sensor data to assess the user'"'"'s body orientation and movement levels; and

modifying the stimulation output based on the user'"'"'s body orientation and movement levels.