title: Development and validation of a probe allowing accurate and continuous monitoring of location of squamo-columnar junction.
abstract: BACKGROUND
  Most pathology of the upper gastrointestinal tract now occurs close to the gastro-oesophageal squamo-columnar junction (SCJ). Studying the pathophysiology of this region even using high resolution pH, impedance and manometry is unreliable due to constant movement with respiration, swallowing and transient lower oesophageal sphincter relaxations.
  
  
  OBJECTIVE
  A technique is reported allowing continuous real-time monitoring of the position of the SCJ. It involves endoscopically clipping a magnet (2 mm × 1 mm) to the SCJ and monitoring its position relative to a probe in the oesophago-gastric lumen. The latter has 26 Hall-Effect sensors mounted at 5mm spacing on a circuit board within a silicone tube.
  
  
  RESULTS
  Bench studies: The recorded position of the magnet along the length of the probe was compared with its actual position. Accuracy was related to the distance between magnet and probe, orientation of the magnet relative to the probe and whether the magnet was anterior, posterior or lateral to the probe. Including all possible orientations of the magnet at or nearer than 10mm from the probe, the median accuracy along the length of probe was 2.4 mm (IQR 2.1 mm). The proportion of all possible orientations within 10mm of the probe giving an accuracy of ±10 mm was 88.9%. In vivo studies: With simultaneous fluoroscopy, eight healthy subjects were asked to perform normal breathing, deep breathing, water swallows and finally advancement and retraction of probe over a 12 cm segment. The position recorded by fluoroscopy and probe at each second interval were compared. The correlation co-efficient for all 224 position readings was 0.96 (95% CI: 0.89-0.96). No significant interference was observed when the probe was tested alongside high resolution pH and manometry.
  
  
  CONCLUSIONS
  Used in conjunction with high resolution pH, impedance and manometry, this technique will allow for the first time detailed studies at the squamo-columnar junction.
authors.affiliation: Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom.
authors.forename: Yeong Yeh
authors.initials: YY
authors.lastname: Lee
authors.forename: John P
authors.initials: JP
authors.lastname: Seenan
authors.forename: James G H
authors.initials: JG
authors.lastname: Whiting
authors.forename: Elaine V
authors.initials: EV
authors.lastname: Robertson
authors.forename: Mohammad H
authors.initials: MH
authors.lastname: Derakhshan
authors.forename: Angela A
authors.initials: AA
authors.lastname: Wirz
authors.forename: Donald
authors.initials: D
authors.lastname: Smith
authors.forename: Chris
authors.initials: C
authors.lastname: Hardy
authors.forename: Andrew
authors.initials: A
authors.lastname: Kelman
authors.forename: Patricia
authors.initials: P
authors.lastname: Connolly
authors.forename: Kenneth E L
authors.initials: KE
authors.lastname: McColl
mesh_terms: D000328:Adult; D001698:Biomedical Engineering; D017097:Electric Impedance; D004867:Equipment Design; D004943:Esophagogastric Junction / Q000033:anatomy & histology / Q000502:physiology* / Q000503:physiopathology; D005260:Female; D005471:Fluoroscopy; D005764:Gastroesophageal Reflux / Q000503:physiopathology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D059346:Magnets; D008297:Male; D008365:Manometry; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation*