Devices and methods for non-invasive capacitive electrical stimulation and their use for vagus nerve stimulation on the neck of a patient
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. An apparatus for modulating one or more nerves within a body of a patient comprising:
an enclosure;
a source of energy for generating an electric field housed within the enclosure;
one or more electrodes coupled to the source of energy and housed within the enclosure;
an electrically conductive interface coupled to the electrodes and positionable against an outer skin surface of the patient;
a volume of electrically conductive fluid residing within the enclosure and at least partially surrounding a portion of the electrodes, the volume of electrically conductive fluid electrically coupling the electrodes with the interface; and
wherein the source of energy is configured to deliver one or more electrical impulses from the electrodes through the volume of electrically conductive fluid, the interface and the outer skin surface to a nerve at a target region within the patient.
2. The apparatus of claim 1 wherein the target region is a nerve located at least 1-2 cm beyond the outer skin surface.
3. The apparatus of claim 1 where the target region is a nerve is located at least 2-5 cm beyond the outer skin surface.
4. The apparatus of claim 1 wherein the volume of electrically conductive fluid comprises a solution of electrolytes.
5. The apparatus of claim 1 wherein the volume of electrically conductive fluid comprises a conductive gel.
6. The apparatus of claim 1 further comprising a housing having an outer enclosure enclosing the electrodes and the conduction medium, wherein at least a portion of the outer enclosure comprises one or more openings for containing the electrically conductive interface.
7. The apparatus of claim 6 wherein the electrically conductive interface and the outer enclosure substantially contain the conduction medium therein.
8. The apparatus of claim 1 wherein the electrically conductive interface comprises stainless steel.
9. The apparatus of claim 1 wherein the source of energy is configured to generate an electrical field comprising bursts of pulses with a frequency of about 5 to about 100 bursts per second.
10. The apparatus of 1 wherein the source of energy is configured to generate an electrical field comprising bursts of between 1 and 20 pulses with each pulse about 50-1000 microseconds in duration.
11. The apparatus of claim 1 wherein the electrically conductive interface comprises two discs and the apparatus further comprising two corresponding electrodes, and wherein the electrodes are spaced from each disc by about 0.25 to 4 times the diameter of the corresponding disc.