The trachea: pathologic conditions and trauma.

A variety of common and uncommon conditions affect the trachea. Respiratory symptoms rarely occur until there is a 50% narrowing of the trachea. Chondromalacia, sometimes seen in conjunction with congenital tracheoesophageal fistula, can be identified with fluoroscopy. Patients with tracheal narrowing who undergo general anesthesia are at great risk for life-threatening acute airway obstruction after removal of the tube. Tracheal narrowing is associated with calcified mediastinal and hilar masses in fibrosing mediastinitis. Tracheal widening has been reported in 30% of patients with pulmonary fibrosis. Primary tracheal neoplasms are rare. In adults 90% of such lesions are malignant, but in children 90% are benign; these benign lesions include squamous cell papilloma and hemangioma. Malignant involvement of the trachea is usually secondary to invasion from adjacent lung, larynx, esophagus or thyroid tissue. Because misplaced tubes are associated with several complications, the radiologist must confirm the location of all tubes. Displacement of the endotracheal tube from full extension to flexion averages 2 cm. Therefore, the tube's tip should be at least this far above the carina to avoid insertion of the tube into the mainstem bronchus. Malpositioning of feeding tubes may cause pneumothorax. Tracheal trauma may be missed unless the radiologist is highly suspicious, as would occur for patients with unresponsive pneumothorax. Observation of the hyoid bone above the third cervical vertebra suggests transection of the cervical trachea.