Method and system for dynamic recalibration of tens stimulation points to compensate for changing electrode conditions with fail-safe and auto-recovery functionality

1. A device for applying transcutaneous electrical nerve stimulation, the device comprising:

a plurality of electrodes configured to stimulate nerves in a stimulation mode of operation and to detect resistance, one or more of the plurality of electrodes are configured as stimulation electrodes to stimulate nerves and different one or more of the plurality of electrodes are configured as non-stimulation electrodes to detect resistance;

sensor configured to detect a change of a skin impedance; and

a controller configured to switch from the stimulation mode of operation into a recalibration mode of operation upon detection of the changed skin impedance.

2. The device as claimed in claim 1 , wherein the controller is configured to adjust an electrical current flowing through the skin via one or more of the plurality of electrodes.

3. The device as claimed in claim 2 , wherein the controller is configured to adjust the electrical current during the recalibration mode of operation via:

adapting a location of the electrode or of the plurality of electrodes for reducing the resistance of the electrode or of the plurality of electrodes or

reapplying of the electrode or of the plurality of electrodes for reducing a resistance of the electrode or of the electrodes, or

selecting a further electrode having reduced resistance from the plurality of electrodes for applying the transcutaneous electrical nerve stimulation, or

selecting a third sub-set of electrodes from the plurality of electrodes for applying the transcutaneous electrical nerve stimulation simultaneously via the electrodes of the third sub-set of electrodes for reducing the resistance of the electrode or of the plurality of electrodes, or

selecting a fourth sub-set of electrodes from the plurality of electrodes for applying the transcutaneous electrical nerve stimulation, the fourth sub-set of electrodes being chosen depending on local physiology, sensed resistance and user interaction.

4. The device as claimed in claim 3 , wherein when adapting a location and/or re-applying the mode or the plurality of electrodes, the controller is configured to provide instructions to a user for adapting the location and/or reapplying the electrode or the plurality of electrodes.

5. The device as claimed in claim 1 , wherein the changed skin impedance results in the switching of functioning of the device.

6. The device as claimed in claim 1 , wherein the controller is configured to vary voltage per one or more of the plurality of electrodes to apply the transcutaneous electrical nerve stimulation.

7. The device as claimed in claim 6 , further comprising a converter configured to generate a variation of the voltage in one or more of the plurality of electrodes.

8. The device as claimed in claim 6 , wherein the changed skin impedance is detected

via monitoring the voltage required for applying the transcutaneous electrical nerve stimulation at substantially constant current, and/or

via monitoring a current resulting from applying the transcutaneous electrical new stimulation at substantially constant voltage, and/or

via measuring a resistance of the electrode.

9. The device as claimed in claim 1 , wherein in the stimulation mode of operation stimulation-voltage is used and wherein in the recalibration mode of operation measuring-voltage is used, the measuring-voltage is lower than the stimulation-voltage.

10. The device as claimed in claim 1 , wherein

the sensor detects the change of the skin impedance during the stimulation mode of operation,

the resistance of at least one stimulation electrode of the plurality of electrodes is measured via monitoring the voltage for applying the transcutaneous electrical nerve stimulation, and

the resistance of at least one non-stimulation electrode of the plurality of electrodes is measured via the measuring-voltage indicating the resistance of the electrode,

the at least one stimulation electrode is configured for applying the transcutaneous electrical nerve stimulation, and

the at least one non-stimulation electrode is configured for not applying the transcutaneous electrical nerve stimulation.

11. The device as claimed in claim 10 , wherein the sensor is configured to measure the resistance of the non-stimulation electrodes during short breaks in the applying of the transcutaneous electrical nerve stimulation.

12. The device as claimed in claim 10 , wherein the sensor is configured to measure the resistance of the stimulation electrodes of the plurality of electrodes for a first sub-set of electrodes.

13. The device as claimed in claim 10 , wherein

the controller is configured to apply a stimulation signal for stimulating the nerve to a second sub-set of electrodes of the plurality of electrodes during a predefined time-window, and

the sensor is configured to monitor a resistance change of the electrodes of the second sub-set over time, and

the controller is configured to select a specific electrode or a specific group of electrodes from the second sub-set in which the resistance change over time is below a predefined limit as the stimulation electrode or stimulation electrodes.

14. A method of transcutaneous electrical nerve stimulation comprising acts of:

a device comprising a plurality of electrodes

providing a plurality of electrodes for stimulating nerves in a stimulation mode of operation and for detecting resistance;

dynamically adapting one or more of the plurality of electrodes as stimulation electrodes for stimulating nerves and different one or more of the plurality of electrodes as non-stimulation electrodes for detecting resistance;

detecting a change of a skin impedance using non-stimulation electrodes, and

switching from a stimulation mode of operation in which stimulation electrodes are used for stimulating the transcutaneous nerves into a recalibration mode of operation upon detection of the changed skin impedance.

15. The method as claimed in claim 14 , wherein the dynamically adapting comprises acts selected from at least one of:

adding neighboring of the plurality of electrodes having relatively low impedance to an existing stimulation electrode;

adding neighboring of the plurality of electrodes within shortest distance from a relatively low impedance location to an existing stimulation electrode; and

adding ones of the plurality of electrodes depending on known physiology of a body part to which the plurality of electrodes is applied.