Postprandial stomach contents have multiple acid layers.
OBJECTIVE
The purpose of this study was to evaluate patterns in gastric pH both fasting and postprandially in different body positions.


METHODS
Ten healthy volunteers were studied. A pH probe was positioned with an electrode 15 cm below the lower esophageal sphincter proximal border then withdrawn 1 cm every 30 seconds to 5 cm above the lower esophageal sphincter. Volunteers were tested on 2 occasions. Initially, they were studied in a semirecumbent position (45 degrees), with the first pull-through after 6 hour fasting. After a meal, a pull-through was repeated 4 consecutive times (approximately 15, 30, 45, and 60 min). On a subsequent day, the positions were changed with each pull-through: upright, supine, right decubitus, and left decubitus. The order of these positions was randomly selected.


RESULTS
The pH step-up is defined as a change in pH from a gastric to an esophageal pH (<4-->>4). No significant difference was found between location of the pH step-up in the fasting and postprandial pull-throughs. An area of lower pH was consistently found within 2 cm distal to the step-up area. Distal to the area of higher gastric pH (median pH at 5), a second acid layer was found. This pattern persisted through the 4 postprandial pull-throughs, irrespective of body position.


CONCLUSIONS
The pH step-up was persistent in the fasting period and for 1 hour postprandially, but did not migrate proximally. Gastric buffering from a meal creates a nonuniform environment with at least 2 acid layers. This pattern is present irrespective of body position. The lack of homogeneity of stomach content postprandially helps to explain the observation of occasional persistent acid gastroesophageal reflux after a meal.
Hila
Amine
A
Medical University of South Carolina, 96 Jonathan Lucas st, suite 210, Charleston, SC 29425, USA. hila@musc.edu
Bouali
Henda
H
Xue
Shuwen
S
Knuff
David
D
Castell
Donald O
DO
D000328:Adult; D004943:Esophagogastric Junction / Q000502:physiology; D005215:Fasting / Q000502:physiology*; D005260:Female; D005750:Gastric Juice / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D019518:Postprandial Period / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D013270:Stomach / Q000502:physiology*