TRACHEOBRONCHIAL RUPTURE
Rupture of the trachea or major bronchi is usually secondary to a nonpenetrating injury of the thorax resulting from a high-energy frontal impact motor vehicle crash. More than 80% of the ruptures are within 2.5 cm of the carina. The proposed mechanisms for this injury include (1) anteroposterior compression with subsequent widening of the transverse diameter that pulls the lungs apart, producing traction on the trachea at the carina; (2) compression of the trachea and major bronchi between the sternum and vertebral column in a patient with a closed glottis exceeds the elasticity of the membranous portion of the airway; and (3) rapid deceleration injury at a point of relative fixation of the carina produces shear forces. Tracheal lacerations usually occur at the junction of the membranous and cartilaginous trachea. Major bronchial rupture is typically unilateral and is more common on the right side. The severity of blunt trauma required for these tracheobronchial ruptures is usually associated with multi-system injuries of the head, abdomen, and extremities. The clinical presentation appears in two distinct patterns, depending on whether there is free communication between the airway rupture and the pleural cavity. If there is free communication, a large pneumothorax is present, and despite tube thoracostomy, there is a persistent vigorous air leak and the lung cannot be reexpanded. Dyspnea is prominent because of the loss of functioning lung. If there is no communication with the pleural cavity, the air escaping via the tracheobronchial injuries forms impressive mediastinal and subcutaneous emphysema. On auscultation, Hamman sign may be evident (i.e., a crunching sound synchronized with the heart beat caused by mediastinal emphysema). In both cases, there may be significant hemoptysis as well. Air embolism is also a life-threatening consequence that must be promptly treated by emergency thoracotomy with cross-clamping of the pulmonary hilum on the affected side.
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Prompt diagnosis of a tracheobronchial injury is
critical, and bronchoscopy is the most accurate means of establishing the
diagnosis and determining the need for urgent thoracotomy. If the tear is
smaller than one-third the circumference, particularly when confined to the
membranous portion, nonoperative management is appropriate if tube thoracostomy results in full
expansion of the lung and there is no persistent air leak. Immediate repair of
tracheobronchial injury is indicated. If more extensive injuries are not
treated surgically, the bronchus heals by granulation, resulting in airway
obstruction, atelectasis, and ultimately pulmonary infection. The details of
thoracotomy and tracheobronchial repair are addressed elsewhere.
