title: Assessment of central airway obstruction using impulse oscillometry before and after interventional bronchoscopy.
abstract: BACKGROUND
  Spirometry is used to physiologically assess patients with central airway obstruction (CAO) before and after interventional bronchoscopy, but is not always feasible in these patients, does not localize the anatomic site of obstruction, and may not correlate with the patient's functional impairment. Impulse oscillometry may overcome these limitations. We assessed the correlations between impulse oscillometry measurements, symptoms, and type of airway narrowing, before and after interventional bronchoscopy, and whether impulse oscillometry parameters can discriminate between fixed and dynamic CAO.
  
  
  METHODS
  Twenty consecutive patients with CAO underwent spirometry, impulse oscillometry, computed tomography, dyspnea assessment, and bronchoscopy, before and after interventional bronchoscopy. The collapsibility index (the percent difference in airway lumen diameter during expiration versus during inspiration) was calculated using morphometric bronchoscopic images during quiet breathing. Variable CAO was defined as a collapsibility index of > 50%. Fixed CAO was defined as a collapsibility index of < 50%. The degree of obstruction was analyzed with computed tomography measurements.
  
  
  RESULTS
  After interventional bronchoscopy, all impulse oscillometry measurements significantly improved, especially resistance at 5 Hz, which decreased from 0.67 ± 0.29kPa/L/s to 0.38 ± 0.17kPa/L/s (P < .001), and reactance at 20 Hz, which increased from -0.09 ± 0.11 to 0.03 ± 0.08 (P < .001). Changes in dyspnea score correlated with resistance at 5 Hz, the difference between the resistance at 5 Hz and the resistance at 20 Hz, and the reactance at 5 Hz, but not with spirometry measurements. The type of obstruction also correlated with dyspnea score, and showed distinct impulse oscillometry measurements.
  
  
  CONCLUSIONS
  Impulse oscillometry measurements correlate with symptom improvements after interventional bronchoscopy. Impulse oscillometry might be useful to discriminate variable from fixed central airway obstruction. (University Hospital Medical Information Network, http://www.umin.ac.jp/english, ID000005322).
authors.affiliation: Division of Respiratory and Infectious Diseases, Department of Internal Medicine.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Handa
authors.forename: Jyongsu
authors.initials: J
authors.lastname: Huang
authors.forename: Septimiu D
authors.initials: SD
authors.lastname: Murgu
authors.forename: Masamichi
authors.initials: M
authors.lastname: Mineshita
authors.forename: Noriaki
authors.initials: N
authors.lastname: Kurimoto
authors.forename: Henri G
authors.initials: HG
authors.lastname: Colt
authors.forename: Teruomi
authors.initials: T
authors.lastname: Miyazawa
mesh_terms: D000368:Aged; D000402:Airway Obstruction / Q000175:diagnosis* / Q000628:therapy; D001999:Bronchoscopy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009991:Oscillometry / Q000379:methods*; D012129:Respiratory Function Tests; D013147:Spirometry; D014057:Tomography, X-Ray Computed
keywords: airway stent; central airway obstruction; impulse oscillometry; interventional bronchoscopy; morphometric bronchoscopy; respiratory reactance; respiratory resistance