title: Measurement of human esophageal tone in vivo.
abstract: BACKGROUND
  Conventional perfused manometry has led to extensive study of phasic contractile activity in the human esophagus, but little is known about esophageal tonic activity. The aims of this study were to assess esophageal smooth and striated muscle tone and the effect of a smooth muscle relaxant (amyl nitrite, 0.3 mL inhalation) on this tone.
  
  
  METHODS
  Using a computerized isobaric recording system (barostat), esophageal tonic activity in 13 healthy subjects was recorded. Two parameters were analyzed: compliance and resistance to initial stretch (resting tone).
  
  
  RESULTS
  The smooth muscle esophagus was significantly more compliant but presented a greater resistance to initial stretch than the striated muscle section. Amyl nitrite affected only the smooth muscle section, significantly increasing compliance and decreasing the resistance to initial stretch. Significant chest pain and/or discomfort occurred only during striated muscle esophagus distension (10 of the 13 subjects at 25 mm Hg distending pressure).
  
  
  CONCLUSIONS
  Active tone is present in the smooth muscle esophagus and can be modulated by a smooth muscle relaxant. Compliance and resting tone differ between the smooth and striated muscle segments of the esophagus. Assessment of tone in patients with esophageal motor disorders and noncardiac chest pain should provide further insights into these disorders.
authors.affiliation: Department of Medicine, University of Toronto, Ontario, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Mayrand
authors.forename: N E
authors.initials: NE
authors.lastname: Diamant
mesh_terms: D000328:Adult; D000680:Amyl Nitrite / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D003187:Compliance; D015154:Esophageal Motility Disorders / Q000503:physiopathology; D004947:Esophagus / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009130:Muscle, Smooth / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology; D010146:Pain / Q000209:etiology; D011312:Pressure
chemical_list: D009569:Nitric Oxide; D000680:Amyl Nitrite; D002118:Calcium