Devices, systems and methods are disclosed that are used to treat a medical condition, by electrical stimulation of a nerve or nerve ganglion, used in conjunction with biofeedback. The system comprises a stimulator that applies electrical impulses sufficient to modulate a nerve at a target site within the patient. A sensor measures a physiological output from the patient, such as heart rate variability, and a property of the stimulation signal is varied based on the physiological output.
