title: Performance and optimal technique for pharyngeal impedance recording: A simulated pharyngeal reflux study.
abstract: OBJECTIVE
  Detection rate, influence of recording site, and subject posture for impedance monitoring of pharyngeal reflux of gastric contents remain unknown. We evaluated the ability of the impedance sensor for detection of various volumes of intrapharyngeal infusate at two sites and in two subject positions.
  
  
  METHODS
  Nineteen healthy subjects were studied using concurrent videoendoscopic, manometric, impedance, and pH recording.
  
  
  RESULTS
  Detection rate of simulated pharyngeal reflux events ranged between 87% and 100% for 1-4 mL. Detection rate for 0.1-1 mL volumes in the upright position was significantly higher (78-85%) when the impedance sensor was located at the proximal margin of the upper esophageal sphincter (UES) compared to 2 cm proximally (38-68%) (P < 0.001). With the sensor at 2 cm above the UES, the average detection rate for all volumes in the upright position was significantly less (P < 0.001) compared to the supine position (48%vs 84%). There was substantial variability in the magnitude of impedance changes induced by different infusates.
  
  
  CONCLUSIONS
  Impedance sensors can detect as small a volume as 0.1 mL and combined with a pH sensor can detect acidic and nonacidic liquid and mist reflux events. Sensor placement at the proximal margin of the UES yields the highest detection rate irrespective of subject posture compared to placement 2 cm proximally. Depending on the volume of refluxate and location of the impedance sensor, a substantial minority of simulated reflux events can be missed.
authors.affiliation: MCW Dysphagia Institute, Division of Gastroenterology and Hepatology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Aslam
authors.forename: Shailesh
authors.initials: S
authors.lastname: Bajaj
authors.forename: Caryn
authors.initials: C
authors.lastname: Easterling
authors.forename: Osamu
authors.initials: O
authors.lastname: Kawamura
authors.forename: Tanya
authors.initials: T
authors.lastname: Rittmann
authors.forename: Candy
authors.initials: C
authors.lastname: Hofmann
authors.forename: Jianxiang
authors.initials: J
authors.lastname: Liu
authors.forename: Reza
authors.initials: R
authors.lastname: Shaker
mesh_terms: D000328:Adult; D016009:Chi-Square Distribution; D017097:Electric Impedance; D016099:Endoscopy, Gastrointestinal; D050782:Esophageal pH Monitoring; D005260:Female; D005764:Gastroesophageal Reflux / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008365:Manometry; D010614:Pharynx / Q000503:physiopathology*; D014741:Video Recording