Devices and methods for monitoring non-invasive vagus nerve stimulation
View Patent ↗Devices and methods are disclosed that treat a medical condition, such as migraine headache, by electrically stimulating a nerve noninvasively, which may be a vagus nerve situated within a patient's neck. Preferred embodiments allow a patient to self-treat his or her condition. Disclosed methods assure that the device is being positioned correctly on the neck and that the amplitude and other parameters of the stimulation actually stimulate the vagus nerve with a therapeutic waveform. Those methods comprise measuring properties of the patient's larynx, pupil diameters, blood flow within an eye, electrodermal activity and/or heart rate variability.
1. A system for treating a medical condition of a patient, comprising:
a stimulator comprising a housing having an electrically permeable contact surface for contacting an outer skin surface of the patient;
an energy source within the housing configured to generate an electric field sufficient to transmit an electric current non-invasively through the outer skin surface of the patient to a nerve at a target region within the patient; and
a device configured to detect whether said electric current is being transmitted to said nerve by measuring a physiological response directly associated with stimulation of said nerve.
2. The system of claim 1 wherein the nerve is a vagus nerve.
3. The system of claim 2 wherein the device measures a property of the patient's voice and/or a laryngeal electromyographic signal and/or an electroglottographic signal.
4. The system of claim 1 wherein the device measures a pupil diameter and/or a blood flow within an eye.
5. The system of claim 1 wherein the device measures electrodermal activity and/or heart rate variability.
6. The system of claim 1 wherein the device measures a property of the patient's autonomic nervous system.
7. The system of claim 1 wherein the device measures a vagal artery blood flow.
8. The system of claim 1 wherein the device measures a cerebral blood flow.
9. The system of claim 1 wherein the device measures an evoked potential and/or an electroencephalogram.
10. The system of claim 1 wherein the device measures a pain threshold and/or a sway and/or a chemical within the patient's blood.
11. The system of claim 1 wherein the device comprises a support vector machine.
12. The system of claim 1 further comprising an optical device configured to detect fluorescent material that has been applied onto or under a skin of the patient.
13. The system of claim 1 further comprising an accelerometer or a gyroscope.
14. The system of claim 1 wherein the electric field comprises bursts of pulses with a frequency of about 1 to about 100 bursts per second.
15. The system of claim 14 wherein the electric field comprises bursts of between 1 and 50 pulses per burst, with each pulse being about 50 to 1000 microseconds in duration.
16. The system of claim 14 wherein the pulses are full sinusoidal waves.
17. The system of claim 1 wherein the electric field at the nerve fiber at the target region is configured to be between about 10 to 600 V/m.
18. The system of claim 17 wherein the electric field is configured to be less than 100 V/m.
19. The system of claim 1 wherein the electrical field is sufficient to modulate a nerve fiber at the target region; and wherein the electric field is not sufficient to substantially modulate a nerve or muscle between the outer skin surface and the target region.
20. The system of claim 2 wherein the electric current is configured to generate an electric field at a vagus nerve above a threshold for generating action potentials within A and B fibers of the vagus nerve and below a threshold for generating action potentials within C fibers of the vagus nerve.
21. The system of claim 1 , further comprising: a docking station configured to convey or transmit to the energy source of said stimulator a specified amount of energy.