Tracheal Injury – Causes, Symptoms, Diagnosis, Treatment

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Tracheal Injury may follow from either cervical or thoracic injury; cervical injuries tend to be more visible and obvious; thoracic injury may go unnoticed. When there is an injury to the tracheobronchial tree, a bronchial injury is more common, especially in blunt trauma where shearing forces may act on the relatively fixed bronchial structures and disrupt them.

The trachea is a cartilaginous tube that courses through the neck and upper chest to connect the pharynx and larynx to the lungs. The trachea bifurcates at the carina into the right and left primary bronchi, via which inspired air is delivered to lung tissue, and expired out. The study of tracheal injury is often combined with adjacent airway structures (tracheobronchial trauma, laryngotracheal trauma).

Trauma to the trachea may be penetrating or blunt and acute or subacute. A blow or stab wound to the neck, or crush injuries to the upper chest, may cause acute traumatic disruption of the trachea, but subacute insults also occur (e.g., from an overinflated endotracheal tube [ETT] cuff pressing against the internal tissues of the trachea over time). Blunt trauma to the neck may result in shearing of the trachea, usually within 3 cm of the carina. Depending on the mechanism, tracheal trauma may be associated with trauma to nearby structures including bony disruptions of the cervical spine, vascular injury to the great vessels, carotids, or jugulars, or digestive tract involvement. Regardless of the mechanism, early diagnosis and surgical repair are crucial to reducing complications and loss of respiratory function.

Causes of Tracheal Injury

Tracheal trauma may follow from either cervical or thoracic injury; cervical injuries tend to be more visible and obvious; thoracic injury may go unnoticed. When there is an injury to the tracheobronchial tree, a bronchial injury is more common, especially in blunt trauma where shearing forces may act on the relatively fixed bronchial structures and disrupt them.

Iatrogenic causes include percutaneous dilatational tracheostomy, endotracheal intubation, and rigid bronchoscopy. With endotracheal intubation, certain situations predispose the patient to complications including emergency, the skill of the operator, improper use of a stylet, use of a high-pressure cuff, and manipulation of the tube with a blocked cuff.  Patient-specific risk factors for iatrogenic tracheal injury include age between 50 and 70, elevated BMI, female gender, and long term use of corticosteroids.  Most iatrogenic tracheal injuries tend to occur in the posterior membranous portion of the trachea.

Trauma to the trachea may be classified as either penetrating or blunt. Penetrating injuries to the neck and chest should always raise suspicion of, and prompt investigation of, potential tracheal trauma.

Blunt trauma primarily affects the thoracic trachea. In the cervical trachea, blunt trauma will typically cause damage to the cartilaginous portions. For blunt thoracic trauma, three theories exist to explain the cause of tracheal injury. The first primarily occurs in crush injuries where increased force causes shortening of the anteroposterior axis and widening the transverse axis with lungs remaining in contact with the chest wall and causing increased tension on the carina and resultant separation. The second theory suggests that with the glottis closed increased pressure within the trachea causes rupture of the intercartilaginous membrane. The third suggests that rapid deceleration like that seen in motor vehicle accidents causes shearing forces between the more affixed carina and the looser lung tissue.

Blunt trauma to the trachea may result from direct blow (including compression/strangulation), severe neck flexion or extension injuries, or crush injuries to the chest (MVC most common). An endotracheal injury may result from inhalation or exposure to noxious or hot gas, vapor or fumes, or from foreign body aspiration. Iatrogenic causes of injury include intubation and tracheostomy (especially with positive pressure ventilation or an overinflated ETT cuff) as well as cricothyrotomy attempts. It should be noted that blunt trauma resulting in tracheal injury often causes other thoracic and cervical injuries.

Symptoms of Tracheal Injury

  • Symptoms and signs range from mild (blood-tinged sputum) to severe with frank hemoptysis, shortness of breath, dysphagia, and cyanosis. Hoarseness is the presenting symptom in 85% of cases.
  • Coughing up blood
  • Bubbles of air that can be felt underneath the skin of the chest, neck, arms, and trunk (subcutaneous emphysema)
  • Difficulty breathing
  • Acute pain
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Diagnosis of Tracheal Injury

History and Physical

On physical exam, pertinent findings include stridor, cyanosis, dyspnea, voice changes/hoarseness, subcutaneous emphysema, mediastinal crunch on auscultation. The absence of these findings does not exclude tracheal injury, as many of these patients may not have symptoms in the first 24 to 48 hours.

Physical examination may include one or more of the following “hard signs”

Head, Eyes, Ears, Nose, and Throat
  • Visual disturbances
  • Conjunctival or facial petechial hemorrhages
  • Swollen tongue or oropharynx
  • Foreign body (blood, vomit, tissue) in oropharynx
  • Facial edema, lacerations, abrasions, ecchymosis
  • Neck abrasions, edema, lacerations or ligature marks
  • Tenderness to palpation over larynx
  • Hoarseness or stridor
  • Subcutaneous edema or crepitus
Cardiovascular
  • Cyanosis or hypoxia
  • Arrhythmias
  • Respiratory distress
  • Crackles or wheezes
  • Cough
Neurologic
  • Altered mental status
  • Seizures
  • Stroke-like symptoms
  • Incontinence

Evaluation

The initial approach in the emergency department, as always, is directed to the ABCs (Airway, Breathing, and Circulation). If signs of airway injury are present, ensuring and protecting airway patency are of paramount importance. There should be a low threshold for definitive airway management when a tracheal injury is suspected, as there is a significant risk of rapid progression of edema, and the patient may be required to lay supine which may further compromise their airway. Endotracheal intubation may be attempted, but a double set-up (with cricothyrotomy supplies at the bedside) is advisable. Because often there is a concern about induction and paralysis collapsing airway structures, awake intubation should be considered.

Ultrasound

Sonographic evaluation of the abdomen and thorax using the focused assessment with sonography in trauma (FAST) exam is important in the initial phase of the trauma assessment. Per ATLS guidelines, it is ideally performed during the circulation portion of the primary survey to allow for the rapid detection of pathologic pericardial, intraperitoneal, or intrathoracic free fluid. Hemothorax can be identified using the standard flank views where the most dependent portions of the pleural spaces can be imaged. The extended FAST (E-FAST) exam employs additional chest views to evaluate for pneumothorax. The linear ultrasound transducer probe (5 to 10 MHz) is utilized as opposed to the standard curvilinear probe (2.5 to 5 MHz) as the higher frequency enhances visualization of the pleural space. The exam typically begins in the third or fourth intercostal space in the midclavicular line and evaluation is based on the presence or absence of the parietal and visceral pleura sliding past each other, termed lung sliding. Absent lung sliding suggests the presence of a pneumothorax. Several signs have also been described to aid in the diagnosis, most importantly the lung point sign, where both lung sliding and the absence of lung sliding are visualized in the same sonographic window. The lung point sign has a sensitivity of over 66% and is 100% specific for pneumothorax.

Chest X-ray

Most thoracic injuries can be evaluated by physical exam and chest radiograph. A chest x-ray is fast, easy to obtain, inexpensive, and often readily accessible. Any patient who undergoes an intervention in the trauma bay should have a repeat chest x-ray performed to ensure the adequacy of the procedure. An initial chest x-ray is recommended in any patient who presents after blunt thoracic trauma but it is not mandatory if the trauma is minor and the patient is not manifesting any physical signs to suggest underlying injury. Based on the NEXUS chest decision rules, patients younger than 60 years old who have no chest pain or tenderness, no distracting injuries or intoxication, and whose mechanism did not involve rapid deceleration, do not need a routine chest x-ray. All criteria being met, there is a low likelihood of clinically significant intrathoracic injury, with a negative predictive value of 99%. However, if the patient meets any individual criterion, chest radiography should be performed. Conversely, physical exam alone has not been shown to have adequate diagnostic sensitivity, particularly for pneumothorax, in penetrating trauma patients. Therefore, all patients who suffer penetrating injuries need evaluation with chest x-ray since many, up to 20%, with negative physical findings will have hemothorax or pneumothorax.

Cross-Sectional Imaging

The use of CT scans in the evaluation of trauma patients has significantly increased. Compared to chest x-ray, chest CT has greater sensitivity for detecting a pneumothorax or hemothorax and also allows for evaluation of the rib cage, the mediastinum, the lung parenchyma, and the aorta. In blunt trauma, the decision to obtain chest CT should be based on physical findings, injury mechanism, and clinical judgment. Patients who are hemodynamically stable with a normal chest x-ray and no sternal, thoracic spinal, or scapular tenderness are unlikely to have a significant intrathoracic injury to warrant CT as shown by NEXUS. Scanning based on mechanism remains controversial. However, recent studies have also reported a substantial number of patients, up to 19%, with significant underlying injury despite having no clinical symptoms or abnormal findings on chest x-ray. High-risk mechanisms include high-energy deceleration MVC over 30 mph with frontal or lateral impact, MVC with ejection, falls over 7.62 meters (25 feet), and direct chest impact. Therefore, current recommendations are to obtain CT imaging in symptomatic patients and those presenting after high-risk mechanism regardless of symptomatology or chest x-ray findings. In penetrating trauma, there are several indications for CT scanning other than the clinician’s judgment. All cases in which the penetrating object crosses the midline need CT scans as there is an increased risk for mediastinal injury in these patients. Patients with symptoms concerning for underlying tracheobronchial, esophageal, or vascular injury, or those with symptoms that cannot be adequately explained by chest x-ray require further investigation.

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Esophagography, Esophagoscopy, and Bronchoscopy

An esophageal injury is often difficult to diagnose because it lacks specific symptoms. It is rare in blunt trauma and typically occurs in the setting of severe polytrauma which further complicates the diagnosis. When present, patients may have cervical subcutaneous emphysema, neck hematoma, or bloody aspirate from a gastric tube, none of which are specific. A chest x-ray may demonstrate pneumomediastinum or pleural effusion prompting CT, but definitive diagnosis requires esophagram or endoscopy. Water-soluble esophagram is typically performed first, followed by barium esophagram if suspicion remains. Endoscopy is generally less favored in the acute setting due to fear of exacerbating an existing injury. A tracheobronchial injury is rare in blunt trauma, present in less than 1% of patients, and is seen in the setting of severe high-risk mechanisms. Injuries usually occur within 1cm of the carina and are more common in the right mainstem bronchus as it is less flexible. In penetrating trauma, an esophageal injury is often associated with concomitant tracheal injury due to proximity, and these patients require workup for both. Patients with persistent pneumothorax after tube thoracostomy, a large air leak after, difficulty ventilating, and those with transmediastinal penetrating trauma should all undergo expeditious flexible bronchoscopy.

CT Scan and MRI

Other adjunctive measures include suction of secretions to prevent aspiration and enhance ventilation, and oxygen supplementation as needed. Intravenous (IV) access should be secured, and fluid resuscitation started if indicated.

The diagnosis of tracheal trauma may be made by cervical or chest radiography, cervical or chest computed tomography (CT), or bronchoscopy. If a tracheal injury is suspected, CT of the neck and chest with IV contrast should be performed. Up to 70% of patients with acute tracheobronchial injury will have a pneumothorax; 60% will have pneumomediastinum and cervical emphysema. While chest CT is superior to radiographs in diagnosis, it may still yield false negatives due to adjacent edema, hemorrhage or secretions. CT has the added advantage of diagnosing injuries to adjacent structures including sternal fractures and mediastinal hematomas, as well as vascular disruptions when IV contrast is used. Concomitant injuries to the great vessels and esophagus (25% of penetrating upper airway injury), as well as cervical spine injuries (10% to 50% of patients with blunt airway injury), may be diagnosed via CT.

A patient with a potentially unstable unsecured airway should not be placed in a CT scanner as a supine position will increase the risk of airway collapse.

Treatment of Tracheal Injury

Conservative management is appropriate for mild injuries (less than 2 to 3 cm mucosal lacerations, involving less than one-third diameter, no other injury, stable patent airway and breathing, mild symptoms/signs). Humidified oxygen is given and the patient observed in a critical care setting for deterioration. Antibiotic prophylaxis is indicated.

If the airway is compromised, intubate early. The ETT may have the added benefit of stenting a partially collapsed trachea, and possibly tamponading or bridging acute tracheal disruptions with severe air leaks.  Most patients can be managed with orotracheal intubation, but double set-up with preparation for surgical airway is advisable as unsuspected cricoid cartilage injury may convert a partially occluded airway into a completely occluded airway, particularly when an unsuspecting assistant gives the patient cricoid pressure. While rapid sequence intubation (RSI) may be performed, awake intubation should be considered in this patient population. Induction or paralysis may cause a partially stented airway to collapse potentially precluding both intubation and ventilation. Ideally, preoxygenation would be followed by awake intubation; positive pressure ventilation should only be started once the tube is past the injury (sometimes necessitating bronchial intubation) and neuromuscular blockade should follow the airway being secured. Patients with severe open cervical disruptions, especially in penetrating injury, may be intubated by guiding an ETT through the open wound. This may be preferable in fact as it spares otherwise intact tissue from being disrupted for a surgical airway, and facilitates subsequent repair.

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Inhalation injuries should also be managed with early and aggressive intubation (with escalation to cricothyroidotomy or tracheostomy as needed) due to risk of rapid deterioration from laryngeal edema.

In cases of thoracic injury and pneumothorax, a chest tube should be inserted, ensuring that there is lung reexpansion without persistent air leak. When there is coexisting severe pulmonary parenchymal injury, and severe persistent air leak, pneumonectomy may be considered.

Surgical repair of tracheal trauma may include repair of lacerations, reduction and closure of fractured cartilages, and potentially end to end anastomosis if complete transection has occurred.

When the injury is in the proximal two-thirds of the trachea, repair involves a cervical incision and endolaryngeal approach. The anterior neck muscles are dissected, revealing tracheal cartilages; a midline thyrotomy is then performed to reveal the endolarynx allowing for repair of mucosal lacerations, closed with chromic sutures. If indicated, a laryngeal stent may be inserted and secured in place. When the laryngeal cartilages are fractured, stabilization and fixation may be aided by plating, which reduces movement of the fractured fragments and inflammation. Four-point fixation is utilized to hold the plate in place. For complete transection of the trachea, following immediate airway rescue through a tracheostomy, the cricoid cartilage (if fractured) is repaired first. Primary re-anastomosis is then performed using absorbable sutures to repair the mucous membrane, while non-absorbable sutures are placed from the superior cricoid ring to the inferior portion of the first or second tracheal ring to distribute tension away from the anastomosis. Stenting may also be considered.

Surgery

Surgical management even in patients with delayed identification of tracheal injury has proven beneficial in restoring lung function and reducing complications. Location and concomitant injury guide the decision on approach. In general, cervical injuries can be approached through a collar incision. Extension of the incision to the level of the second intercostal through the manubrium can provide access down to the level of the innominate artery and vein. If exposure of the hemithorax or mediastinum is required a median partial sternotomy or clamshell incision could be utilized but does not provide better access to the trachea. For tracheal injuries at the level of the carina or involvement of the bronchi including the middle portion of the left main bronchus, a right anterolateral or posterolateral thoracotomy may be used. The distal portion of the left main bronchus could be approached through a left posterolateral thoracotomy if needed.

Once access has been obtained to the injured area, carefully debride the wound margins in preparation for primary closure using a 3-0 or 4-0 absorbable suture. Transverse wounds should be closed using a simple interrupted suture. Longitudinal repairs are most amenable to a continuous suture. In circumstances where extensive damage has occurred, circumferential resection with end to end anastomosis may be necessary and except for injuries to the carina is preferred to partial debridement with attempted primary repair. When the blood supply is impaired and there is a concern for dehiscence covering with pericardial or mediastinal fat flaps could be of benefit. In all closures, an absorbable suture should be used with the knots on the outside to avoid granuloma and stricture formation and potential lifelong irritation.

After repair, closed thoracic drainage and negative intrathoracic pressure may aid in the expansion of the lungs and occlusion of the repaired defect. Consideration should also be given to head immobilization to reduce tension on repair for 1 to 2 weeks, continued antibiotic coverage, bronchoscopic assisted secretion removal, and incentive spirometry. Steroids, proton pump inhibitors, and cough suppressants can also aid in relieving strain on healing tracheal injuries.

Surgical exploration should occur within 24 hours of the injury to minimize subsequent scarring and airway stenosis. For similar reasons, if endolaryngeal stenting is used in the repair, it should be removed within 10 to 14 days.

References

© 2020, Rx Harun. All rights reserved.

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