Endobronchial ultrasound morphology of expiratory central airway collapse.

Differences in central airway wall structure in patients with various forms of expiratory central airway collapse can be identified by endobronchial ultrasound using a 20 MHz radial probe. In tracheobronchomalacia due to relapsing polychondritis, the cartilage is thick and irregular while the membranous portion is normal. In malacia due to chronic inflammation after tracheotomy, the cartilage is thick and irregular and the membranous portion is also thick. In excessive dynamic airway collapse associated with COPD, on the contrary, the cartilage is normal and the posterior membrane is thin when compared to the normal airway wall structures identified in a patient with physiological dynamic airway collapse. These findings may support the hypothesis that various clinical forms of expiratory central airway collapse are not only different morphologically, physiologically and aetiologically, but also structurally.