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 stimulator 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 contact with the electrodes. The conducting medium is also in contact with an interface element that may conform to the contour of a target body surface of the patient when the interface element is applied to that surface. When the interface element is made of insulating (dielectric) material, and disclosed stimulation waveforms are used, the power source need not supply high voltage, in order to capacitively stimulate the target nerve. The stimulator is configured to produce a peak pulse 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 in the vicinity of the target nerve and patient's skin.
1. An apparatus for modulating one or more nerves within a body of a patient comprising:
a source of energy for generating one or more electric impulses comprising bursts of pulses with each burst having a frequency of 1 to 100 Hz and each pulse have a duration of 20 to 1000 microseconds;
one or more electrodes coupled to the source of energy;
an interface coupled to the electrodes and positionable against an outer skin surface of the patient; and
wherein the source of energy is configured to deliver the electrical impulses from the electrodes through the interface and the outer skin surface to a nerve at a target region within the patient.
2. The apparatus of claim 1 wherein each burst has a frequency of between about 10 Hz to 35 Hz.
3. The apparatus of claim 1 wherein the bursts of pulses are generated from a single signal that is not modulated by another signal.
4. The apparatus of claim 1 further comprising a conduction medium in electrical contact with the electrodes and the interface such that the electrical impulses pass from the electrodes through the conduction medium to the interface.
5. The apparatus of claim 4 wherein the conduction medium comprises a volume of conductive gel.
6. The apparatus of claim 4 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 the interface and wherein the source of energy is positioned within the housing.
7. The apparatus of claim 6 wherein the interface comprises a material that is permeable to charged particles and wherein the electrodes each have a distal end surrounded by the conduction medium and spaced from the interface such that the electrical impulses pass from the distal end of the electrodes through the conduction medium to the interface.
8. The apparatus of claim 1 wherein the interface comprises a dielectric material.
9. The apparatus of claim 1 wherein the interface comprises a porous material.
10. The apparatus of claim 1 wherein the interface comprises stainless steel.
11. The apparatus of claim 1 wherein the pulses have a duration of about 200 microseconds.
12. The apparatus of claim 1 wherein the pulses are sinusoidal and have a frequency of about 1 to 50 KHz.
13. The apparatus of claim 12 wherein the pulses have a frequency of about 5 KHz.
14. The apparatus of claim 1 wherein the interface comprises two membranes and the apparatus further comprising two corresponding electrodes, and wherein the electrodes are spaced from each membrane by about 0.25 to 4 times the diameter of the corresponding membrane.
15. The apparatus of claim 1 wherein the interface is positionable on an outer surface of the patient's neck and source of energy is configured to deliver the electrical impulses to the vagus nerve of the patient, wherein the electrical impulses are sufficient to stimulate activity of afferent nerve fibers within the vagus nerve.
16. The apparatus of claim 15 wherein the electrical impulses are insufficient to block or inhibit activity of efferent nerve fibers within the vagus nerve.
17. A device for modulating one or more nerves within a body of a patient comprising:
a handheld device comprising a enclosure with an interior and an interface configured for contact with an outer skin surface of a patient;
one or more electrodes housed within the enclosure;
a source of energy coupled to the electrodes;
a conduction medium within the enclosure and electrically coupling the electrodes with the interface; and
wherein the source of energy is configured to apply an electrical impulse through the electrodes, the conduction medium and the interface of the enclosure transcutaneously through an outer skin surface of the patient to a nerve at a target region below the outer skin surface.
18. The device of claim 17 wherein the conduction medium comprises a volume of conductive gel filling a space between the electrodes and the interface within the enclosure.
19. The device of claim 17 wherein the interface comprises two membranes and the device further comprising two corresponding electrodes, and wherein the electrodes are spaced from each membrane by about 0.25 to 4 times the diameter of the corresponding membrane, wherein the conductive medium electrically couples the membranes with the electrodes.
20. The device of claim 17 wherein the electrical impulse is sufficient to modulate a nerve within the target region and insufficient to substantially modulate nerve(s) in the vicinity of the outer skin surface.
21. The device of claim 17 wherein the source of energy is housed within the enclosure.
22. The device of claim 17 wherein the electrical impulse comprises bursts of pulses with a frequency of about 5 to about 100 bursts per second, wherein each pulse has a duration of about 20 to 1000 microseconds.
23. The device of claim 17 wherein the electrical impulse comprises bursts of sinusoidal pulses followed by a silent inter-burst period that repeats itself over a time period of about 1 to 100 Hz and wherein the sinusoidal pulses have a frequency of about 1 to 50 KHz.
24. The device of claim 23 wherein the time period is 10 to 35 Hz.
25. The device of claim 23 wherein the frequency of the sinusoidal pulses is about 5 KHz.
26. The device of claim 23 wherein the electrical impulses is generated from a single signal that is not modulated by another signal.
27. The device of claim 17 wherein the interface is positionable on an outer surface of the patient's neck and the source of energy is configured to deliver the electrical impulse to the vagus nerve of the patient, wherein the electrical impulse is sufficient to stimulate activity of afferent nerve fibers within the vagus nerve.