title: Airway distensibility in adults with asthma and healthy adults, measured by forced oscillation technique.
abstract: BACKGROUND
  Reduced airway distensibility in subjects with asthma compared with control subjects may be related to differences in lung elastic recoil and bronchomotor tone.
  
  
  OBJECTIVE
  To examine the contribution of lung elastic recoil and bronchomotor tone to airway distensibility.
  
  
  METHODS
  We compared airway distensibility in 18 subjects with asthma with 19 control subjects before and after bronchodilator administration and, in a subgroup of 7 subjects with asthma and 8 control subjects, correlated distensibility with pressure-volume parameters.
  
  
  RESULTS
  Distensibility was measured, using the forced oscillation technique, as the linear slope of conductance versus volume between total lung capacity (TLC) and 75% TLC and between 75% TLC and FRC. Transpulmonary pressure was recorded concurrently with distensibility, using an esophageal balloon. Pressure-conductance data were described using linear regressions and pressure-volume data were described using exponential equations. Subjects with asthma had lower baseline FEV1 (p=0.0003) and conductance (p=0.002) than did control subjects. Distensibility above 75% TLC was less in subjects with asthma than in control subjects (p<0.0001), but there was no difference below 75% TLC. Bronchodilator administration did not alter distensibility despite increases in FEV1 (p=0.0002) and conductance (p<0.0001) in subjects with asthma, and conductance (p=0.0004) in control subjects. After bronchodilator administration, subjects with asthma had reduced lung elastic recoil compared with control subjects (p=0.03) and a reduced pressure-conductance slope (p=0.01), but there were no correlations between pressure-volume characteristics and airway distensibility.
  
  
  CONCLUSIONS
  Airway distensibility measured by forced oscillation technique is reduced in subjects with asthma compared with subjects without asthma, is not related to lung elastic recoil, and is unchanged by bronchodilator administration. Airway wall remodeling remains the most likely cause of reduced airway distensibility in asthma.
authors.affiliation: Woolcock Institute of Medical Research, P.O. Box M77, Missenden Road, Camperdown, NSW, 2050 Australia. njb@woolcock.org.au
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: Brown
authors.forename: Cheryl M
authors.initials: CM
authors.lastname: Salome
authors.forename: Norbert
authors.initials: N
authors.lastname: Berend
authors.forename: C William
authors.initials: CW
authors.lastname: Thorpe
authors.forename: Gregory G
authors.initials: GG
authors.lastname: King
mesh_terms: D000328:Adult; D000403:Airway Resistance / Q000502:physiology; D001249:Asthma / Q000503:physiopathology*; D016022:Case-Control Studies; D004548:Elasticity; D006801:Humans; D008170:Lung Compliance / Q000502:physiology*; D008875:Middle Aged; D009129:Muscle Tonus / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology; D009991:Oscillometry; D015656:Respiratory Mechanics / Q000502:physiology