title: pH probe positioning for 24-hour pH-metry by manometry or pH step-up.
abstract: OBJECTIVE
  Before pH measurement, manometry is recommended for precise pH probe positioning. We investigated whether the pH probe could be positioned accurately by the pH difference between the oesophagus and the stomach (pH step-up).
  
  
  METHODS
  Dual-channel 24-h pH-metry with probes positioned 5 cm above either the manometrically determined upper lower oesophageal sphincter margin or the pH step-up was performed in healthy volunteers and reflux patients. To determine the pH step-up, the pH probe was pulled back from the stomach until a sudden rise to pH greater than four occurred. Probe position, reflux episodes and the fraction of the time pH was less than four were compared using the Wilcoxon test for difference and the Hodges-Lehman estimate inclusive confidence interval for equivalence. The pH step-up method was evaluated further during proton pump inhibitor therapy and after drug discontinuation.
  
  
  RESULTS
  The pH probe was positioned 2 cm and 1 cm closer to the stomach by the pH step-up method in the volunteers and reflux patients, respectively. A small increase in upright reflux episodes but not in supine reflux episodes was registered by the probe positioned by pH step-up. No significant differences in the fraction of the time pH was less than four were obtained between the two probes. The Hodges-Lehman calculation proved equivalence for both methods of probe positioning for 24-h pH-metry. During proton pump inhibitor therapy, no pH step-up was detectable in three volunteers and in one patient. On the first day after discontinuing therapy, the pH step-up method yielded clear-cut results again.
  
  
  CONCLUSIONS
  The pH probe for diagnostic 24-h pH-metry and, with some limitations, also for 24-h pH-metry for therapy control, can be positioned accurately by the pH step-up method.
authors.affiliation: Department of Gastroenterology, Hepatology and Gastrointestinal Oncology, Academic Teaching Hospital Bogenhausen, Munich, Germany. christian.pehl@extern.lrz-muenchen.de
authors.forename: Christian
authors.initials: C
authors.lastname: Pehl
authors.forename: Ilona
authors.initials: I
authors.lastname: Boccali
authors.forename: Michael
authors.initials: M
authors.lastname: Hennig
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schepp
mesh_terms: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D000328:Adult; D000368:Aged; D001562:Benzimidazoles / Q000627:therapeutic use; D004791:Enzyme Inhibitors / Q000627:therapeutic use; D005260:Female; D005745:Gastric Acidity Determination / Q000295:instrumentation; D005764:Gastroesophageal Reflux / Q000150:complications / Q000188:drug therapy / Q000378:metabolism*; D006551:Hernia, Hiatal / Q000150:complications; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008365:Manometry / Q000379:methods*; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation* / Q000379:methods; D009853:Omeprazole / Q000031:analogs & derivatives; D000077402:Pantoprazole; D054328:Proton Pump Inhibitors; D013454:Sulfoxides / Q000627:therapeutic use
chemical_list: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D001562:Benzimidazoles; D004791:Enzyme Inhibitors; D054328:Proton Pump Inhibitors; D013454:Sulfoxides; D000077402:Pantoprazole; D009853:Omeprazole