Exclusion criteria included severe liver, lung, renal, or hematological disorders; a history of peptic ulcer disease or gastrointestinal surgery; a history of connective tissue disorder; Metabolism inhibitor and chest pain originating in a musculoskeletal disorder. The interview was conducted by one investigator, who provided patients with a standardized set of questions. To clarify the characteristics of these patients, we analyzed the extent of overweight (body mass index >25 kg/m2), smoking history, and history of chronic alcoholism (> 20 g ethanol/day). Typical reflux symptoms were defined

as heartburn and acid regurgitation. Heartburn was described as a burning sensation rising from lower chest up toward the

neck, and acid regurgitation was described as the regurgitation of acidic fluid from the stomach or lower chest to the throat. All patients underwent UGI endoscopy, esophageal manometry, and combined ambulatory 24-h esophageal impedance–pH monitoring (MII–pH). One experienced observer, who was blinded to the clinical details of these patients, interpreted the results. The study protocol was approved by the local ethics committee, and all participating patients gave informed consent. UGI endoscopy was carried out after an overnight fast. It was performed with standard endoscopes (XQ-230, XQ-240; Olympus Optical, Tokyo, Japan) by two experienced endoscopists who were blinded to patients’ Pritelivir order symptoms. The stomach and the second portion of the duodenum were inspected to exclude possible lesions. The distal portion of the esophagus was carefully examined to determine the presence of mucosal injury. The extent of esophageal mucosal damage was assessed using the Los Angeles Classification.7 Esophageal manometry was performed in the supine position using an eight-lumen polyvinyl manometric tube with four distal side holes and four proximal openings situated 5 cm apart (ESM38R; Arndorfer Medical

Specialties, Greendale, WI, USA). Each channel was connected to external physiological pressure transducers, and was continuously perfused with bubble-free, distilled Methane monooxygenase water at 0.6 mL/min via a low-compliance pneumohydraulic system (Mui Scientific, Ontario, Canada). The manometric tube was introduced transnasally and then slowly withdrawn in 1-cm increments by station pull-through in order to measure the lower esophageal sphincter (LES) resting pressure. LES relaxation was assessed with three wet swallows of 5 mL water. The completeness of relaxation was determined by residual LES pressure compared with resting LES pressure. Peristalsis was evaluated by positioning at least three pressure sensors in the body of the esophagus, situated at 5-cm intervals. The distal sensor was positioned 3 cm above the LES, and a series of 15 wet swallows was performed.