Ambulatory gastric pH monitoring: proper probe placement and normal values

Aliment Pharmacol Ther. 2001 Aug;15(8):1155-62. doi: 10.1046/j.1365-2036.2001.01011.x.


Background: Gastric acid production may persist while patients are treated with proton pump inhibitors. Twenty-four-hour intragastric pH monitoring is being used to identify gastric acid in the stomach while on medical therapy.

Aim: To identify the optimal region of the stomach to demonstrate the presence of gastric acid.

Method: Probe locations confirmed with fluoroscopy after placement and prior to removal. In experiment 1, five volunteers underwent simultaneous, 24-h gastro-oesophageal pH monitoring with the pH sensors located in the gastric antrum, body, fundus and distal oesophagus. In experiment 2, five volunteers underwent simultaneous 24-h pH monitoring with sensors located side by side in the gastric fundus assessing the reproducibility of gastric pH in this region. In experiment 3, 35 volunteers underwent 24-h pH monitoring with pH sensors located in the distal oesophagus and gastric fundus. The mean percentage time for which pH < 4 was calculated for total, upright, and supine time periods.

Results: pH profiles for the gastric fundus and body are similar-the mean percentage total time for which pH < 4 was 92.2% and 90.1%, respectively (P=N.S.). These values are significantly different from the antrum; pH < 4=54.6% (P < 0.01). pH values from the gastric fundus are highly reproducible (linear regression P= 0.004, r(2)=0.96). The normal values (mean +/- 95th percentile) for percentage time gastric pH < 4 in the fundus were: total 95.6 +/- 1.5%, upright 94.8 +/- 1.8%, and supine 96.5 +/- 2.3%.

Conclusion: The fundus is the optimal location to evaluate the presence of gastric acid; pH values are highly reproducible in this area. Normal values for percentage time gastric pH < 4 for a healthy population are now defined.

Publication types

  • Clinical Trial

MeSH terms

  • Esophagus / metabolism
  • Female
  • Fluoroscopy
  • Gastric Acidity Determination*
  • Gastric Fundus / metabolism
  • Humans
  • Hydrogen-Ion Concentration
  • Male
  • Monitoring, Ambulatory / methods*
  • Posture
  • Prospective Studies
  • Pyloric Antrum / metabolism
  • Reference Values
  • Reproducibility of Results
  • Time Factors