title: Intraesophageal acid perfusion sensitizes the esophagus to mechanical distension: a Barostat study.
abstract: OBJECTIVE
  The pathogenesis of noncardiac chest pain is unclear. Increased gastroesophageal reflux and decreased pain thresholds to intraesophageal balloon distension have been demonstrated in a proportion of such patients. We aimed to investigate whether acid exposure sensitizes esophageal mechanoreceptors in healthy volunteers.
  
  
  METHODS
  After an overnight fast, an infinitely compliant balloon, 4.5 cm in length and mounted on a multilumen transnasal manometry catheter, was placed 8.5 cm above the lower esophageal sphincter in 12 healthy male volunteers aged 18-39 yr. After determination of the minimal distending pressure, the balloon was inflated up to 48 mm Hg by means of a computer-controlled barostat (G & J Electronics, Canada). Graded stepwise distensions were interspersed with random decreases in pressure to two-thirds of the previous value. At each pressure level, the subjects were asked to report on sensation and the presence of pain. Baseline distension was repeated to determine reproducibility of the pressure/volume relationship and also the perception and pain thresholds. After the baseline distension sequence, the esophagus was perfused for 20 min (at 7 ml/min) with either normal saline (control) or 0.1 N hydrochloric acid at 37 degrees C on a random basis.
  
  
  RESULTS
  Basal sensory thresholds varied widely (first perception 5-36 mm Hg, pain 8 > or = 43 mm Hg). Two subjects did not experience pain up to the maximum distending pressure (42 and 43 mm Hg, respectively, after correction for the minimal distending pressure). Esophageal body compliance was similar on repeat distension. Sensory thresholds were reproducible with different distensions (perception r = 0.99, pain r = 0.95). Saline resulted in no significant changes in perception or pain thresholds. Acid perfusion reduced first perception (median before and after acid, 15 mm Hg and 8 mm Hg, respectively, p = 0.05) and pain threshold (median before and after acid, 32.5 mm Hg and 26.5 mm Hg, respectively, p = 0.05). When compared to changes after saline perfusion, acid perfusion reduced the perception threshold (median change, -3.8 mm Hg vs 0 mm Hg, p = 0.04) and tended to reduce the pain threshold (median change, -3.75 mm Hg vs +0.75 mm Hg, p = 0.09).
  
  
  CONCLUSIONS
  Intraesophageal balloon distension using a barostat is a reproducible method of measuring esophageal body compliance and sensory thresholds. Acute exposure to acid seems to sensitize the esophagus to perception from intraluminal balloon distension.
authors.affiliation: Department of Medicine, University of Sydney, Australia.
authors.forename: W H
authors.initials: WH
authors.lastname: Hu
authors.forename: C J
authors.initials: CJ
authors.lastname: Martin
authors.forename: N J
authors.initials: NJ
authors.lastname: Talley
mesh_terms: D000293:Adolescent; D000328:Adult; D002404:Catheterization; D002637:Chest Pain / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D004548:Elasticity; D004947:Esophagus / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D006801:Humans; D006851:Hydrochloric Acid / Q000008:administration & dosage*; D008297:Male; D008365:Manometry; D008465:Mechanoreceptors / Q000187:drug effects* / Q000502:physiology; D017288:Pain Threshold / Q000502:physiology; D010477:Perfusion / Q000379:methods*; D011312:Pressure; D012016:Reference Values; D015203:Reproducibility of Results
chemical_list: D006851:Hydrochloric Acid