DEVICES AND METHODS FOR NON-INVASIVE ELECTRICAL STIMULATION AND THEIR USE FOR VAGAL NERVE STIMULATION
A non-invasive electrical stimulation device shapes an elongated electric field of effect that can be oriented parallel to a long nerve, such as a vagus nerve in a patient's neck, producing a desired physiological response in the patient. The stimulator comprises a source of electrical power, at least one electrode and a continuous electrically conducting medium in which the electrode(s) are in contact. The stimulation device is configured to produce a peak pulse voltage that is sufficient to produce a physiologically effective electric field in the vicinity of a target nerve, but not to substantially stimulate other nerves and muscles that lie between the vicinity of the target nerve and patient's skin. Current is passed through the electrodes in bursts of preferably five sinusoidal pulses, wherein each pulse within a burst has a duration of preferably 200 microseconds, and bursts repeat at preferably at 15-50 bursts per second.
1 . A method comprising:
positioning a contact surface of a housing in contact with an outer skin surface of a body of a patient;
generating an electrical impulse within the housing, wherein the electrical impulse comprises bursts of pulses with each of the bursts having a frequency from about 1 Hz to about 100 Hz and with each of the pulses generated from a signal that is not modulated by another signal; and
conducting the electrical impulse from the contact surface through the outer skin surface to a target region in the patient such that an electrical field is generated in the target region and the electrical field modulates a nerve in the target region.
2 . The method of claim 1 , wherein the conducting comprises spacing an electrode within the housing from the outer skin surface.
3 . The method of claim 1 , wherein the conducting comprises conducting the electrical impulse from inside the housing and through the contact surface to the outer skin surface.
4 . The method of claim 1 , wherein each of the pulses has a duration of about 100 microseconds to about 400 microseconds.
5 . The method of claim 1 , wherein each of the pulses has a duration of about 200 microseconds.
6 . The method of claim 1 , wherein the target region is a first target region and further comprising:
constraining the electrical impulse from modulating a nerve at a second target region between the outer skin surface and the first target region.
7 . The method of claim 6 , wherein the constraining comprises positioning an electrically conductive medium around a portion of an electrode within the housing such that a direction of a generated electric field is constrained within the electrically conductive medium.
8 . The method of claim 6 , wherein the constraining comprises positioning an electrical insulator around a portion of an electrode within the housing such that a component of a generated electric field substantially normal to a surface of the electrical insulator is about zero.
9 . The method of claim 1 , wherein the generating comprises generating the electric field within the housing with a power supply contained within the housing.
10 . The method of claim 1 , wherein the generating comprises generating a magnetic field within the housing, wherein the magnetic field is sufficient to induce the electric field at the target region.
11 . The method of claim 1 , wherein the target region includes a vagus nerve.
12 . The method of claim 1 , wherein the positioning comprises positioning the contact surface in contact with a neck of the patient.
13 . The method of claim 7 , wherein the electrically conductive medium comprises an electrically conductive gel.
14 . The method of claim 1 , wherein the electric field has a gradient of greater than about 2 V/m/mm.
15 . The method of claim 1 , wherein the electrical field has an amplitude equal to or greater than about 10 V/m and equal to or less than about 600 V/m.
16 . The method of claim 1 , wherein the nerve is modulated to treat at least one of a disorder of the patient or a condition of the patient, wherein at least one of the disorder or the condition includes at least one of primary headache, allergic rhinitis, Alzheimer's disease, postoperative cognitive dysfunction, rheumatoid arthritis, bronchoconstriction, Parkinson's disease, dementia, multiple sclerosis, neurodegenerative disease, depression, epilepsy, gastroparesis, or an auto-immune disease or disorder.