Subglottic narrowing

A pathologic reduction in caliber of the subglottic airway segment, just below the true vocal folds to the inferior border of the cricoid cartilage, resulting in partial upper airway obstruction and increased airflow resistance. Possible causes are prolonged intubation, idiopathic scar tissue, acid reflux, autoimmune inflammatory disease (granulomatosis with polyangiitis/Wegener's, sarcoidosis, relapsing polychondritis), trauma (neck injury, strangulation, inhalation of burns/toxic chemicals), congenital defects, and infections (bacterial, fungal, viral).