Non-invasive Vagal Nerve Stimulation (nVNS) for Symptomatic Exacerbation of Nausea in Patients With Gastroparesis and Related Disorders

Inclusion Criteria: * Age 18 years or older at registration. * Diagnosis of gastroparesis as documented by gastric emptying scintigraphy (4-hour emptying after a low-fat meal with any combination of 2- and 4-hour retention of \>60% and 10%, respectively), or Chronic Unexplained Nausea and Vomiting (CUNV). * Ongoing symptoms (i.e. Nausea and vomiting, bloating, and abdominal pain) with a nausea score of 3 or more on the patient assessment of upper gastrointestinal disorders-symptom severity index (PAGI-SYM) scale at baseline (moderate to severe nausea). * Exclusion of other causes of symptoms such as mechanical gastrointestinal obstruction, uncontrolled esophagitis, peptic ulcer disease, etc. By standard radiographic or endoscopic tests. * Use of the following medications on an as-needed basis: ondansetron, promethazine or prochlorperazine but no more than four times a day. Exclusion Criteria: * Another active disorder, which could explain symptoms in the opinion of the investigator. * Age \< than 18 years. * Pregnancy or nursing. * A previous surgery of the upper gastrointestinal tract, including vagotomy. * Use of narcotics more than 3 days per week. * History of prolonged QT interval or a history of clinically significant arrhythmia. * Abnormal baseline ECG (e.g. Second- and third-degree heart block, atrial fibrillation, atrial flutter, recent history of ventricular tachycardia or ventricular fibrillation, or clinically significant premature ventricular contraction). * Previous bilateral or right cervical vagotomy. * Uncontrolled high blood pressure. * Currently implanted with an electrical and/or neurostimulator device, including but not limited to cardiac pacemaker or defibrillator, vagal neurostimulator, deep brain stimulator, spinal stimulator, bone growth stimulator, or cochlear implant. * History of carotid endarterectomy or vascular neck surgery on the right side. * Implanted with metal cervical spine hardware or has a metallic implant near the gammaCore stimulation site. * Any other condition, which in the opinion of the investigator would impede compliance or hinder the completion of the study. * Failure to give informed consent.