title: Bronchial collapsibility at forced expiration in healthy volunteers: assessment with multidetector CT.
abstract: OBJECTIVE
  To assess forced-expiratory bronchial collapsibility in healthy volunteers by using multidetector computed tomography (CT) and to compare the results with the current diagnostic criterion for bronchomalacia.
  
  
  METHODS
  The institutional review board approved this HIPAA-compliant study. Following informed consent, 51 healthy volunteers with normal pulmonary function and no history of smoking were imaged by using a 64-detector row scanner with spirometric monitoring at total lung capacity and during forced exhalation. The total study population (in whom both main bronchi were imaged) included 25 men and 26 women (mean age, 50 years). Each scan was analyzed at a workstation by a fellowship-trained thoracic radiologist. Cross-sectional area measurements were obtained from end-inspiratory and forced-expiratory CT images for the right main bronchus (RMB), left main bronchus, (LMB), and bronchus intermedius (BI), and the mean percentage of expiratory collapse was calculated for each bronchus. The number of participants who exceeded the current diagnostic threshold level (>50% expiratory reduction in cross-sectional area) for bronchomalacia was calculated. Comparisons of airway dimensions and airway collapse according to bronchial segment and sex were made by using repeated-measures analysis of variance.
  
  
  RESULTS
  Mean percentage of expiratory collapse was 66.9% ± 19.0 (standard deviation) for the RMB and 61.4% ± 16.7 for the LMB. Thirty-seven (73%) of 51 participants exceeded the diagnostic threshold level for bronchomalacia. Significant differences were observed in mean percentage of expiratory collapse between the RMB (66.9% ± 19.0) and LMB (61.4% ± 16.7) (P = .0005). Among a subgroup of 37 participants in whom the BI was also imaged, the mean percentage of expiratory collapse was 61.8% ± 22.8, and 27 (73%) participants exceeded the diagnostic threshold level for bronchomalacia.
  
  
  CONCLUSIONS
  Healthy volunteers demonstrate a wide range of forced-expiratory bronchial collapse, frequently exceeding the current diagnostic threshold level for bronchomalacia.
authors.affiliation: Center for Airway Imaging and Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Ave, Boston, MA 02215, USA. dlitmano@bidmc.harvard.edu
authors.forename: Diana
authors.initials: D
authors.lastname: Litmanovich
authors.forename: Carl R
authors.initials: CR
authors.lastname: O'Donnell
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Bankier
authors.forename: Armin
authors.initials: A
authors.lastname: Ernst
authors.forename: Mary E
authors.initials: ME
authors.lastname: Millett
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Loring
authors.forename: Phillip M
authors.initials: PM
authors.lastname: Boiselle
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D055091:Bronchomalacia / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D045853:Exhalation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted; D013147:Spirometry; D036542:Tomography, Spiral Computed / Q000379:methods*