Detecting cutaneous electrode peeling using electrode-skin impedance
View Patent ↗Apparatus for transcutaneous electrical nerve stimulation in a user, the apparatus comprising: stimulation means for electrically stimulating at least one nerve; an electrode array connectable to said stimulation means, said electrode array comprising a plurality of electrodes for electrical stimulation of the at least one nerve, said electrodes having a pre-formed geometry and known electrode-skin contact area size when in complete contact with the user's skin; monitoring means electrically connected to said stimulation means for monitoring the impedance of the electrical stimulation through said electrode array; and analysis means for analyzing said impedance to estimate a change in the electrode-skin contact area.
1. Apparatus for transcutaneous electrical nerve stimulation in a user, the apparatus comprising:
stimulation means for electrically stimulating at least one nerve;
an electrode array connectable to said stimulation means, said electrode array comprising a plurality of electrodes for electrical stimulation of the at least one nerve, said electrodes having a pre-formed geometry and known electrode-skin contact area size when in complete contact with the user's skin;
monitoring means electrically connected to said stimulation means for monitoring the impedance of the electrical stimulation through said electrode array; and
analysis means for analyzing said impedance to estimate a change in the electrode-skin contact area;
wherein said stimulation means alters the electrical stimulation of said stimulation means when said analysis means determines that the monitored electrode-skin impedance value has changed significantly; and
further wherein the change in the impedance value at a given time is quantified by an impedance ratio between the impedance value at that time and a baseline impedance value.
2. Apparatus according to claim 1 where said monitoring of the impedance is accomplished with the same electrical stimulation as that used to stimulate said at least one nerve.
3. Apparatus according to claim 1 where said monitoring of the impedance is accomplished with different electrical stimulation than that used to stimulate said at least one nerve.
4. Apparatus according to claim 3 wherein the electrical stimulation used for monitoring of the impedance has an intensity that is below the electrotactile sensation threshold of the user.
5. Apparatus according to claim 1 wherein said impedance is defined as the anode-cathode voltage difference divided by the stimulation current of the electrical stimulation of said monitoring means at a particular time in the electrical stimulation.
6. Apparatus according to claim 1 wherein a history of the electrode-skin impedance values is stored by said monitoring means.
7. Apparatus according to claim 1 wherein the baseline impedance value is the first available impedance value from the impedance history.
8. Apparatus according to claim 1 wherein the baseline impedance value is the minimum among all available impedance values.
9. Apparatus according to claim 1 wherein said significant change is defined as that where the impedance ratio exceeds an impedance ratio threshold.
10. Apparatus according to claim 9 wherein the impedance ratio threshold depends upon the identified electrode geometry and size.
11. Apparatus according to claim 1 wherein the alteration to the electrical stimulation is to terminate stimulation.
12. Apparatus according to claim 1 wherein the alteration to the electrical stimulation is to inversely scale the electrical stimulation intensity by the impedance ratio.
13. Apparatus according to claim 1 wherein the geometry and size of said electrodes can be identified by said monitoring means.
14. Apparatus according to claim 1 wherein the monitoring means monitors the impedance during stimulation.
15. Apparatus according to claim 1 wherein the monitoring means monitors the impedance after the stimulation means electrically stimulates at least one nerve.