title: Forced oscillometry track sites of airway obstruction in bronchial asthma.
abstract: BACKGROUND
  Spirometry is the most commonly used method for assessment of airway function in bronchial asthma but has several limitations. Forced oscillometry was developed as a patient-friendly test that requires passive cooperation of the patient breathing normally through the mouth.
  
  
  OBJECTIVE
  To compare spirometry with forced oscillometry to assess the role of forced oscillometry in the detection of the site of airway obstruction.
  
  
  METHODS
  This case-and-control study included 50 patients with known stable asthma and 50 age- and sex-matched healthy subjects. All participants underwent spirometry (ratio of force expiration volume in 1 second to forced vital capacity, percentage predicted for forced expiration volume in 1 second, percentage predicted for forced vital capacity, percentage predicted for vital capacity, and forced expiratory flow at 25-75%) and forced oscillometry (resistance at 5, 20, and 5-20 Hz).
  
  
  RESULTS
  By spirometry, all patients with asthma had airway obstruction, 8% had isolated small airway obstruction, 10% had isolated large airway obstruction, and 82% had large and small airway obstruction. By forced oscillometry, 12% had normal airway resistance, 50% had isolated small airway obstruction with frequency-dependent resistance, and 38% had large and small airway obstruction with frequency-independent resistance. There was significant difference between techniques for the detection of the site of airway obstruction (P = .012). Forced oscillometry indices were negatively correlated with spirometric indices (P < .01).
  
  
  CONCLUSIONS
  Forced oscillometry as an effortless test, conducted during quiet tidal breathing, and does not alter airway caliber; thus, it can detect normal airway function better than spirometry in patients with asthma. Forced oscillometry detects isolated small airway obstruction better than spirometry in bronchial asthma.
authors.affiliation: Chest Department, Al-Azhar University, Cairo, Egypt. Electronic address: nsm101196@yahoo.com.
authors.forename: Manal Refaat
authors.initials: MR
authors.lastname: Hafez
authors.affiliation: Chest Department, Al-Azhar University, Cairo, Egypt.
authors.forename: Samiha Mohamed
authors.initials: SM
authors.lastname: Abu-Bakr
authors.affiliation: Chest Department, Al-Azhar University, Cairo, Egypt.
authors.forename: Alyaa Abdelnaser
authors.initials: AA
authors.lastname: Mohamed
mesh_terms: D000328:Adult; D000402:Airway Obstruction / Q000209:etiology / Q000503:physiopathology*; D000403:Airway Resistance; D001249:Asthma / Q000503:physiopathology*; D005260:Female; D005540:Forced Expiratory Flow Rates; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D009991:Oscillometry / Q000379:methods*; D015203:Reproducibility of Results; D012119:Respiration; D012680:Sensitivity and Specificity; D013147:Spirometry; D014797:Vital Capacity; D055815:Young Adult