Tracheobronchial Injury - Causes

Causes

Injuries to the tracheobronchial tree within the chest may occur due to penetrating forces such as gunshot wounds, but are more often the result of blunt trauma. TBI due blunt forces usually results from high-energy impacts such as falls from height and motor vehicle accidents; the injury is rare in low-impact mechanisms. Injuries of the trachea cause about 1% of traffic-related deaths. Other potential causes are falls from high places and injuries in which the chest is crushed. Explosions are another cause.

Gunshot wounds are the commonest form of penetrating trauma that cause TBI. Less commonly, knife wounds and shrapnel from motor vehicle accidents can also penetrate the airways. Most injuries to the trachea occur in the neck, because the airways within the chest are deep and therefore well protected; however, up to a quarter of TBI resulting from penetrating trauma occurs within the chest. Injury to the cervical trachea usually affects the anterior (front) part of the trachea.

Certain medical procedures can also injure the airways; these include tracheal intubation, bronchoscopy, and tracheotomy. The back of the trachea may be damaged during tracheotomy. TBI resulting from tracheal intubation (insertion of a tube into the trachea) is rare, and the mechanism by which it occurs is unclear. However, one likely mechanism involves an endotracheal tube catching in a fold of membrane and tearing it as it is advanced downward through the airway. When an endotracheal tube tears the trachea, it typically does so at the posterior (back) membranous wall. Unlike TBI that results from blunt trauma, most iatrogenic injuries to the airway involve longitudinal tears to the back of the trachea or tears on the side that pull the membranous part of the trachea away from the cartilage. Excessive pressure from the cuff of an endotracheal tube can reduce blood supply to the tissues of the trachea, leading to ischemia and potentially causing it to become ulcerated, infected, and, later, narrowed.

The mucosal lining of the trachea may also be injured by inhalation of hot gases or harmful fumes such as chlorine gas. This can lead to edema (swelling), necrosis (death of the tissue), scar formation, and ultimately stenosis. However, TBI due to inhalation, foreign body aspiration, and medical procedures is uncommon.