Fig. 3

Expiratory central airway collapse at aortic arch level. Cross-sectional area measurement of trachea at aortic arch level using cine CT during end-inspiratory (a) and end-expiratory phases (d) revealed significant expiratory airway collapse that was calculated to be 60% cross-sectional area reduction. Corresponding flexible bronchoscopy images are shown (b, e) confirming the presence of significant expiratory airway collapse with almost the same degree perceived by CT. Sagittal MinIP images (c, g) shows the significant expiratory airway collapse at the same level (arrow)