Tracheobronchial Injury Etiology: blunt trauma causes tear in trachea or mainstem bronchusImaging: massive pneumomediastinum with minimal pneumothorax, fallen lung sign on CTClinical: little improvement after chest tube Cases of Tracheobronchial Injury CXR AP shows air in the superior mediastinum and neck, airspace disease in the left upper lobe, and a small amount of air in the left pleural space.