title: Esophageal acid exposure decreases intraluminal baseline impedance levels.
abstract: OBJECTIVE
  Intraluminal baseline impedance levels are determined by the conductivity of the esophageal wall and can be decreased in gastroesophageal reflux disease (GERD) patients. The aim of this study was to investigate the baseline impedance in GERD patients, on and off proton pump inhibitor (PPI), and in healthy controls.
  
  
  METHODS
  Ambulatory 24-h pH-impedance monitoring was performed in (i) 24 GERD patients with and 24 without pathological esophageal acid exposure as well as in 10 healthy controls and in (ii) 20 patients with refractory GERD symptoms despite PPI, once on PPI and once off PPI. Baseline impedance levels in the most distal and the most proximal impedance channels were assessed.
  
  
  RESULTS
  Median (interquartile range) distal baseline impedance in patients with physiological (2,090 (1,537-2,547) Ω) and pathological (781 (612-1,137) Ω) acid exposure was lower than in controls (2,827 (2,127-3,270) Ω, P<0.05 and P<0.001). A negative correlation between 24-h acid exposure time and baseline impedance was observed (r=-0.7, P<0.001). In patients measured off and on PPI, median distal baseline impedance off PPI was significantly lower than on PPI (886 (716-1,354) vs. 1,372 (961-1,955) Ω, P<0.05) and distal baseline impedance in these groups was significantly lower than in healthy controls (P<0.05 and P<0.001). Proximal baseline impedance did not differ significantly between the patients off PPI and on PPI (1,793 (1,384-2,489) vs. 1,893 (1,610-2,561) Ω); however, baseline impedance values in both measurements were significantly lower than in healthy controls (3,648 (2,815-3,932) Ω, both P<0.001).
  
  
  CONCLUSIONS
  These findings suggest that baseline impedance is related to esophageal acid exposure and could be a marker of reflux-induced changes to the esophageal mucosa.
authors.affiliation: Department of Gastroenterology and Hepatology, Academic Medical Center Amsterdam, The Netherlands. b.f.kessing@amc.uva.nl
authors.forename: Boudewijn F
authors.initials: BF
authors.lastname: Kessing
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Bredenoord
authors.forename: Pim W
authors.initials: PW
authors.lastname: Weijenborg
authors.forename: Gerrit J M
authors.initials: GJ
authors.lastname: Hemmink
authors.forename: Clara M
authors.initials: CM
authors.lastname: Loots
authors.forename: A J P M
authors.initials: AJ
authors.lastname: Smout
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D004351:Drug Resistance; D004553:Electric Conductivity; D017097:Electric Impedance; D050782:Esophageal pH Monitoring; D004947:Esophagus / Q000378:metabolism*; D005260:Female; D005744:Gastric Acid / Q000378:metabolism*; D005764:Gastroesophageal Reflux / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D054328:Proton Pump Inhibitors / Q000627:therapeutic use*; D055815:Young Adult
chemical_list: D054328:Proton Pump Inhibitors