Injuries (trauma) of the larynx and trachea - Causes and pathogenesis

Causes of damage (injuries) of the larynx and trachea

Trauma to the larynx and trachea may occur with a general neck injury. Causes of closed laryngotracheal injuries include a punch or object blow, car accidents, strangulation attempts, and blunt force trauma to the chest. Penetrating wounds are usually knife or bullet wounds. These are usually combined injuries.

Isolated injuries of the larynx and trachea occur with internal trauma. Internal trauma of the larynx and trachea is often iatrogenic (intubation, prolonged artificial ventilation of the lungs). Injury to the larynx and trachea is possible with any manipulation of the larynx, including during endoscopic examinations and surgical interventions. Another cause of internal trauma to the larynx and trachea is the ingress of a foreign body (fish bone, parts of dentures, pieces of meat, etc.). Internal trauma to the larynx and trachea also includes burns (thermal, chemical). Most common are burns of the respiratory tract with sodium hydroxide, battery contents, ammonium used in the household, and car care products. In case of burn injury, there is a direct effect on the mucous membranes of high temperatures and chemicals - combustion products.

Classification of injuries (traumas) of the larynx and trachea

According to the mechanism of action of the damaging factor, injuries and wounds of the larynx and trachea are divided into:

• external;
• internal;
• stupid;
• sharp:
• punctured;
• cut.

By degree of damage:

• isolated;
• combined.

Depending on the involvement of the skin:

• closed;
• open.

On the fact of penetration into the hollow organs of the neck:

• penetrating:
• non-penetrating.

By etiology:

• mechanical (including iatrogenic):
  • firearms:
  • through;
  • blind;
• tangents:
  • knife;
  • chemical;
  • thermal.

Pathogenesis of damage (injuries) of the larynx and trachea

The larynx is protected by the lower jaw from above and the collarbones from below: its lateral mobility plays a certain role. In case of a direct blow, for example, a car or sports injury, a fracture of the laryngeal cartilages is caused by the displacement of the larynx and its compression against the spine. Not only the force of the blow is important, but also the previous state of the neck structures. Ossification of the laryngeal cartilages, previous surgical interventions on the neck. Previous radiation therapy and other local factors also determine the outcome of the traumatic impact. In case of blunt trauma to the larynx, the risk of skeletal damage is greater than in case of penetrating injury. Blunt trauma to the larynx and cervical trachea may be accompanied by a fracture of the hyoid bone, laryngeal and tracheal cartilages, separation of the larynx from the trachea or hyoid bone. The vocal folds may be torn, their displacement or the arytenoid cartilages, paresis of the larynx are possible. Hemorrhages develop in the subcutaneous tissue and muscles, hematomas are formed that can compress the structures of the neck and lead to respiratory failure. Traumatic injuries inside the larynx and trachea, submucous hemorrhages, linear ruptures of the mucous membrane, internal bleeding are of great importance. Particularly severe injuries occur with the sequential impact of several traumatic agents.

External trauma, as a rule, leads to damage to the tissues surrounding the larynx and trachea and to the organs of the esophagus, throat, cervical spine, thyroid gland, and vascular-nerve bundles of the neck.

When analyzing the possible mechanism of injury, three zones of the neck are conventionally distinguished. The first extends from the sternum to the cricoid cartilage (high risk of injury to the trachea, lungs, bleeding due to vascular injury); the second - from the cricoid cartilage to the edge of the lower jaw (zone of injury to the larynx, esophagus, possible injury to the carotid arteries and veins of the neck, more accessible for examination); the third - from the lower jaw to the base of the brain (zone of injury to large vessels, salivary gland, pharynx).

In penetrating gunshot wounds, both walls of the larynx are often damaged. In approximately 80% of cases of laryngeal wounds, the entry and exit wounds are located on the neck. In other cases, the entry wound may be located on the face. The difficulty in determining the passage of the wound channel is due to the mobility of the larynx and trachea, their displacement after injury. The skin edges of the wound often do not coincide with the wound channel, and its course is usually tortuous. In blind wounds of the neck, accompanied by damage to the larynx and trachea, the exit wound may be in the lumen of the larynx and trachea.

Tangential wounds have a more favorable outcome due to the fact that the skeleton of the larynx and trachea is not damaged. However, it should be remembered that it is possible to injure adjacent organs and develop chondroperichondritis of the larynx and trachea or phlegmon of the neck in the early stages after the injury.

Puncture and cut wounds are often severe, as they are penetrating and are accompanied by vascular injury. If a foreign body enters the larynx or trachea, asphyxia may develop immediately. If a foreign body penetrates soft tissue, inflammation and edema develop, often bleeding. Subsequently, the inflammation process may spread to surrounding tissues, leading to the development of mediastinitis, phlegmon of the neck. As with other injuries, penetrating wounds of the esophagus and the development of subcutaneous emphysema are possible.

In burn injuries, external damage to the oral and laryngeal mucosa may not reflect the true severity of damage to the esophagus and stomach. In the first 24 hours, swelling of the mucous membranes increases, then ulceration occurs during the next 2-5 days. In the next 2-5 days, the inflammatory process continues, accompanied by vascular stasis (thrombosis). Rejection of necrotic masses occurs on the 5th-7th day. Fibrosis of the deep layers of the mucous membrane and the formation of scars and strictures begins from the 2nd-4th week. Against the background of inflammation, perforation of hollow organs, the appearance of tracheoesophageal fistulas, the development of pneumonia and mediastinitis are possible. The risk of esophageal carcinoma increases sharply. As a result of such inflammation, cicatricial stenosis of the hollow organs of the neck is often formed.

The pathogenetic process in intubation trauma includes:

• hemorrhages in soft tissues, laryngeal hematomas;
• ruptures of the mucous membrane of the larynx and trachea;
• vocal fold rupture;
• dislocation and subluxation of the cricoarytenoid joint;
• granulomas and ulcers of the larynx.

The outcomes of such injuries are cicatricial deformation of the larynx and trachea, vocal fold cysts, postintubation granulomas and laryngeal paralysis. Severe injuries can also be caused by bougienage of the narrowed lumen of the larynx and trachea in order to expand their lumens in case of cicatricial deformation. In this case, penetration of the bougies into the paratracheal space is possible, with subsequent development of mediastinitis and damage to adjacent organs and large vessels.

In some cases, traumatic damage to the larynx (hemorrhage into the vocal folds, granuloma, subluxation of the cricoarytenoid joint) occurs with a sharp increase in subglottic pressure during screaming, strong coughing, against the background of constant overstrain of the vocal apparatus with the use of a hard attack of sound. Predisposing factors are considered to be the presence of gastroesophageal reflux in the patient, changes in the microcirculation of the vocal folds, taking drugs containing acetylsalicylic acid.

In case of traumatic injury of any etiology, emphysema, hematoma and edema of the mucous membrane of the larynx can increase over two days and immediately lead to respiratory failure, stenosis of the larynx and trachea.

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