title: "pH-Only" acid reflux events in infants during later phases of the feeding cycle are less acidic and cleared more efficiently than classic 2-phase acid reflux events.
abstract: BACKGROUND
  Gastroesophageal acid exposure in infants is a function of 4 acid gastroesophageal reflux (AGER) types: classic 2-phase, single-phase, and pH-only events (POEs), as well as rereflux episodes. In symptomatic infants, classic 2-phase events and POEs make up the majority of total AGER events and AGER events lasting 5 minutes or longer, and are responsible for the majority of total gastroesophageal acid exposure. Also, in symptomatic infants, chemical clearance efficiency of classic 2-phase events has been shown to be influenced by feeding. Pathogenicity of AGER involves variables that include frequency, duration, and pH of AGER events. The purpose of this investigation was to compare classic 2-phase episodes and POEs on the basis of these variables during discrete periods related to feeding.
  
  
  METHODS
  Impedance/pH tracings from 12 symptomatic infants (median age 20 weeks) were examined. Mean frequencies, durations, and nadir pH values were calculated during feeding, the first hour postprandial (1stPP), the second hour postprandial (2ndPP), and fasting.
  
  
  RESULTS
  Compared with classic 2-phase events, POEs were cleared significantly more efficiently during 1stPP (3-fold, P = 0.02), 2ndPP (3-fold, P = 0.0001), and fasting (4.5-fold, P < 0.0001), and were less acidic during 2ndPP (1.9 +/- 0.15 vs 2.6 +/- 0.07, P = 0.0005) and fasting (1.5 +/- 0.12 vs 2.9 +/- 0.07, P < 0.0001). Whereas clearance of classic 2-phase events became increasingly less efficient, clearance of POEs did not fluctuate significantly during the course of the feeding cycle.
  
  
  CONCLUSIONS
  The lower acidity and more rapid clearance during 2ndPP and fasting suggest that POEs are likely to have a different clinical impact (compared with classic 2-phase AGER events) during later phases of the feeding cycle.
authors.affiliation: Nationwide Children's Hospital, Ohio State University School of Medicine and Public Health, Columbus, OH, USA. frederick.woodley@nationwidechildrens.org
authors.forename: Frederick W
authors.initials: FW
authors.lastname: Woodley
authors.forename: Hayat
authors.initials: H
authors.lastname: Mousa
mesh_terms: D004435:Eating; D017097:Electric Impedance; D005215:Fasting; D005260:Female; D005502:Food; D005744:Gastric Acid; D005764:Gastroesophageal Reflux / Q000145:classification* / Q000503:physiopathology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007223:Infant; D041943:Infant Formula; D007231:Infant, Newborn; D007700:Kinetics; D008297:Male; D008895:Milk, Human; D012189:Retrospective Studies