title: Exclusion of pH artifacts is essential for hypopharyngeal pH monitoring.
abstract: BACKGROUND
  Published yields of pH monitoring for suspected laryngopharyngeal reflux (LPR) vary greatly. Hypopharyngeal pH artifacts may be responsible for these inconsistencies.
  
  
  OBJECTIVE
  To determine the impact of potential artifacts on pH monitoring of the hypopharynx and esophagus.
  
  
  METHODS
  Patients with suspected LPR were prospectively studied. Single-catheter, triple-sensor pH monitoring was performed off antireflux therapy. Subjects recorded meal times and marked liquid swallows outside of meals on the data recorder. Results were analyzed by excluding six potential pH artifacts individually and all together. Positive pH test was defined as three or more reflux episodes in hypopharynx, total percent of time pH less than 4 was 1.0% or greater in the proximal esophagus, and total percent of time pH less than 4 was 4.2% or greater in the distal esophagus. Wilcoxon rank sum and chi-square tests were used.
  
  
  RESULTS
  Thirty-eight subjects (24 females; median age, 47 yr) completed the study. A total of 2,225 hypopharyngeal pH drops less than 4 were identified; 48% were short pH drops at less than 5 seconds, 17% within meal periods, 16% liquid swallows outside of meals, 16% isolated proximal pH drops, 12% pH out of range, and 5% pH drift. Eighty percent of the hypopharyngeal pH drops were at least one of the potential pH artifacts. The yield of the hypopharyngeal sensor was reduced by 45% (from 92% to 47%) after all potential pH artifacts were excluded. Yields of proximal and distal esophageal pH sensors were reduced by 19% and 8%, respectively, significantly less than the hypopharyngeal sensor (P < .01).
  
  
  CONCLUSIONS
  Patients should record all liquid swallows outside of meals. It is essential to exclude all potential artifacts for hypopharyngeal pH monitoring in patients with suspected LPR.
authors.affiliation: Division of Gastroenterology/Hepatology, University of Louisville School of Medicine, Louisville, Kentucky 40202, USA.
authors.forename: Steven P
authors.initials: SP
authors.lastname: Harrell
authors.forename: Jennifer
authors.initials: J
authors.lastname: Koopman
authors.forename: Scheryl
authors.initials: S
authors.lastname: Woosley
authors.forename: John M
authors.initials: JM
authors.lastname: Wo
mesh_terms: D016477:Artifacts; D050782:Esophageal pH Monitoring / Q000592:standards*; D005260:Female; D005764:Gastroesophageal Reflux / Q000378:metabolism*; D006801:Humans; D007830:Larynx / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results