ECAC

aka expiratory central airway collapse.

Reference: https://www.mayoclinicproceedings.org/article/S0025-6196(20)30258-5/fulltext

Often comorbid COPD, GERD/LPR, autoimmune/RP. ICS postulated to be causal in some cases.

Presentation: nonspecific - 'seal-bark like cough', impaired secretion clearance.

PFT may be obstructive (45%), restrictive (20%) or normal (20%)

Excessive (or expiratory) dynamic airway collapse of the posterior membrane (EDAC)

normal = 50 +/- 20% luminal collapse on forced expiration. 70+% is excessive

Tracheobronchomalacia (TBM)

abnormal movement of cartilagenous wall (anterior). Can be cartilagenous (splaying at the end of the tracheal cartilage) or circumfrential (e.g. in relapsing polychondritis)