Transcutaneous electrical nerve stimulator with automatic detection of user sleep-wake state
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.
1. 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;
acquiring data from an electromechanical sensor mounted to said device that measures the user's body orientation and movement;
monitoring said sensor data to determine the user's body orientation and movement;
analyzing said body orientation and movement to determine a state of the user when the body orientation of the user is recumbent; and
modifying the stimulation based on the state of the user.
2. A method according to claim 1 wherein the body orientation and movement are used to determine whether the user is in a sleep state or a wake state.
3. A method according to claim 2 wherein the sleep-wake state is used to modify the stimulation intensity.
4. A method according to claim 1 wherein a mechanical coupling is created between said device and the body of said user with a strap holding the device in place at a specific anatomical location.
5. A method according to claim 4 wherein the mechanical coupling is confirmed through electrode on-skin detection.
6. A method according to claim 1 wherein monitoring said sensor data includes mapping the sensor's spatial axes to the body orientation of the user.
7. A method according to claim 1 wherein monitoring said sensor data includes determining the fraction of the earth gravitational force projected to one or more axes of the electromechanical sensor.
8. A method according to claim 7 wherein projection is measured by the angle between said axes and the horizontal plane.
9. A method according to claim 1 wherein analyzing said body orientation includes the comparison of (i) the estimated angle of said axes and the horizontal plane, and (ii) a pre-determined angle threshold.
10. A method according to claim 1 wherein the user's body orientation is considered to be recumbent if the absolute value of the estimated angle is below the angle threshold.
11. A method according to claim 1 wherein monitoring said sensor data includes a weighted summation of sensor data from more than one axis over a time period to form a movement activity count.
12. A method according to claim 1 wherein monitoring said sensor data include mapping multiple body movement activity counts to a body movement measure.
13. A method according to claim 12 wherein the mapping is a weighted average function.
14. A method according to claim 13 wherein the weighted average gives a larger weight to the more recent activity counts.
15. A method according to claim 1 wherein analyzing said body movement includes comparison of the estimated body movement measure and a movement threshold.
16. A method according to claim 15 wherein the user body movement is considered to be “low activity” if the body movement measurement is below the movement threshold.
17. A method according to claim 1 wherein the stimulation modification is to reduce stimulation intensity level by a fixed amount if the user's state is in a “sleep” state.
18. A method according to claim 1 wherein the stimulation modification is to reduce stimulation intensity level by a fixed percentage if the user's state is in a “sleep” state.
19. A method according to claim 1 wherein the stimulation modification is to restart stimulation after a fixed time period without any intervention from the user if the user's state is in a “sleep” state.
20. A method for applying transcutaneous electrical nerve stimulation to a user, said method comprising:
applying stimulation means and an electromechanical sensor to the user's body;
delivering stimulation current to the user to stimulate one or more nerves;
analyzing the sensor data to determine a state of the user's body when the body orientation of the user is recumbent; and
modifying the stimulation based on the state of the user's body.
21. A method according to claim 1 wherein the user is determined to be in a “sleep” state if the body orientation of the user is recumbent and if the body movement of the user is in a “low activity” state.
22. A method according to claim 1 wherein the electromechanical sensor is an accelerometer.