Upper airway obstruction can be defined as subglottic, glottic, or supraglottic. Subglottic obstruction Subglottic obstruction is frequently associated with previous manipulation or trauma to the airway, including intubation or tracheotomy. Prolonged intubation increases the risk of subsequent subglottic stenosis. Subglottic stenosis can also occur in certain autoimmune disorders such as Wegener's granulomatosis. Mediastinal and cervical tumors such as adenoid cystic carcinoma can directly compress the subglottic lumen.
Benign goiters can also enlarge to the point where they shift or compress the trachea.
Glottic obstruction Glottic obstruction can be due to failure of the vocal folds to open, or from an obstructive lesion at the level of the vocal folds. In turn, vocal fold immobility can be caused by paralysis, cricoarytenoid joint fixation, neurologic disorder, or soft tissue scarring. The most frequent cause for bilateral vocal fold paralysis is surgery. Thyroid surgery, especially total thyroidectomy, can result in injury to the recurrent laryngeal nerve. This nerve innervates the muscles that open the vocal folds during inspiration.