CHAPTER 32 TRACHEAL, LARYNGEAL, AND OROPHARYNGEAL INJURIES

Luis G. Fernandez, Scott H. Norwood, John D. Berne

Structural mobility and elasticity are characteristics of the upper airway that make injury to these structures infrequent. Skeletal protection is also provided anteriorly by the mandible and sternum and posteriorly by the bony spinal column ¹ (Figure 1). Upper airway injuries are identified in only 0.03% of patients admitted to major trauma centers. These injuries are frequently lethal, which explains their higher reported occurrence in autopsy series.^2,³ Penetrating mechanisms of injury are more common than blunt mechanisms of injury,^1,^2,⁴ the true incidence of which is unknown.^1,⁵ Twenty-one percent of patients with upper airway injuries die within the first 2 hours after hospitalization.⁶ The diagnosis is often delayed in patients without immediate life-threatening upper airway trauma.^6,⁷ Such delays often result in serious late complications.^8,⁹ Limited experience in nonoperative and operative management of airway injuries has led to a wide variety of recommendations that may be considered under various clinical scenarios. For unstable, immediate life-threatening upper airway injuries, rapid airway control by any available means is essential for patient survival. Most authors agree that tracheal intubation through an open wound that communicates with the tracheobronchial tree is appropriate.¹ Stable patients may benefit from bronchoscopic-guided tracheal intubation distal to the injury site, and blind endotracheal tube placement is almost always a poor choice for airway control.¹⁰ Airway injuries are always challenging to even the most experienced surgeon since traditional approaches to airway control are often contraindicated.

Figure 1 (A) Median sagittal section through the head and neck. (B) Median sagittal section of the head, showing a dissection of the interior of the pharynx, after the removal of the mucous membrane.

(From Gray’s Anatomy, 39th ed. St. Louis, Churchill Livingstone/Mosby, 2004, figures 35.1 and 35.3, with permission.)

ANATOMY OF UPPER AIRWAY

Pharynx

Surgical Anatomy

The pharynx consists of the following elements:

Nasopharynx: Extends from posterior choanae of the nose to the soft palate. It is related posteriorly to the base of the skull. The nasopharynx contains adenoid tissue and the orifices of the Eustachian tubes. This area is not accessible to direct inspection and must be examined by mirrors or optical instruments.

Oropharynx: Portion that is visible via the mouth. The oropharynx extends from the soft palate superiorly to the vallecula inferiorly. The posterior and lateral walls of the oropharynx are formed by the superior and middle pharyngeal constrictors.

Palatine tonsils: Lymphoid aggregates between the mucosal folds created by the palatoglossus and palatopharyngeus muscles. The palatine tonsils are covered by stratified squamous epithelium, which continues down into deep crypts. Tonsils vary widely in size and may be sessile or pedunculated.

Hypopharynx: Portion of the pharynx that lies inferior to the tip of the epiglottis. The posterior and lateral walls are formed by middle and inferior pharyngeal constrictors. The hypopharynx extends inferiorly to the cricopharyngeus muscle, where the pharynx empties into the cervical esophagus. Anteriorly, it extends from the vallecula and contains the epiglottis and the larynx. Lateral to the larynx are the pyriform sinuses, two mucosal pouches whose medial borders are the lateral walls of the larynx. The posterior aspect of the hypopharynx contains the posterior pharyngeal wall and postcricoid mucosa (Figures 2, 3, and 4).

Figure 2 Contents of the oropharynx.

(From Gray’s Anatomy, 39th ed. St. Louis, Churchill Livingstone/Mosby, 2004, figure 33.4, with permission.)

Figure 3 Muscles and blood supply of the pharynx. Muscles of the pharynx, viewed from behind, together with the associated vessels and nerves.

(Adapted from Gray H: Anatomy of the Human Body. Philadelphia, Lea & Febiger, 1918. Available at www.bartleby.com/107/.)

Figure 4 Posterior view of the laryngeal cartilages and ligaments.

(From Gray’s Anatomy, 39th ed. St. Louis, Churchill Livingstone/Mosby, 2004, figure 36.3, with permission.)

PHARYNGEAL INJURY

Incidence

Isolated blunt pharyngeal injury is exceedingly rare. It is more often associated with concomitant cervical facial trauma. Penetrating pharyngeal injury occurs more commonly in the pediatric population from lacerations caused by intraoral foreign bodies.¹¹

Mechanism of Injury

Pharyngeal trauma may occur from foreign body ingestion, blunt or penetrating trauma, or following laryngoscopy or other endoscopic procedures.¹²^–¹⁵

Diagnosis

The initial clinical scenario varies. Patients with nonlethal injuries commonly present with dysphagia and odynophagia. Patients with more severe injuries may present with aphonia, dyspnea, hemoptysis, and severe acute respiratory failure that may rapidly lead to asphyxia if not treated.¹⁶ Injuries to the esophagus and pharynx are difficult to diagnose and may be missed during the management of other immediate life-threatening injuries. Oral bleeding, drooling, and subcutaneous emphysema all suggest upper digestive tract or airway injury.¹⁶ When possible, careful examination of the oropharynx and hypopharynx should be performed at the bedside.

Lateral views of the neck and cervical CT scan may identify soft tissue air (Figures 5 and 6). A nonionic contrast-enhanced esophagram and/or esophagoscopy are indicated if injury is clinically suspected.¹⁷ Contrast leak may be revealed on esophagram (see Figure 5).

Figure 5 Retropharyngeal air (black arrow) as seen on a lateral cervical spine radiograph/esophagogram.

Figure 6 Retropharyngeal air as seen on a noncontrast computed tomography scan of the neck.

LARYNX

Surgical Anatomy

The larynx is a functional “valve” separating the trachea from the upper aero-digestive tract. It is primarily an organ of communication (the voice box), but also serves as an important regulator of respiration. The larynx is necessary for effective coughing and for creating Valsalva maneuvers. The larynx also prevents aspiration during swallowing.

The larynx is composed of the following elements:

Skeleton (Figure 7)

Hyoid bone: Attaches to epiglottis and strap muscles.

Thyroid cartilage: Anterior attachment of vocal folds. Posterior articulation with cricoid cartilage.

Cricoid cartilage: Complete ring. Articulates with thyroid and arytenoid cartilages.

Arytenoids: Two cartilages that glide along the posterior cricoid and attach to posterior ends of vocal folds.

Divisions

Supraglottis: Usually covered with respiratory epithelium containing mucous glands.

Epiglottis: Leaf-shaped mucosal-covered cartilage, which projects over larynx.

Aryepiglottic folds: Extend from the lateral epiglottis to the arytenoids.

False vocal cords: Mucosal folds superior to the true glottis. Separated from true vocal folds by the ventricle.

Ventricle: Mucosal-lined sac, variable in size which separates the supraglottis from the glottis.

Glottis: The true vocal folds attach to the thyroid cartilage at the anterior commissure. The posterior commissure is mobile, as the vocal folds attach to the arytenoids. Motion of the arytenoids effects abduction or adduction of the larynx. The bulk of the vocal fold is made up of muscle covered by mucosa. The free edge is characterized by stratified squamous epithelium. The vocal folds abduct for inspiration and adduct for phonation, cough, and Valsalva.

Subglottis: Below the vocal folds, extending to the inferior border of the cricoid cartilage.

Innervation—branches of the vagus nerve

Superior laryngeal nerve: Sensation of the glottis and supaglottis. Motor fibers to the cricothyroid muscle, which tenses the vocal folds. This nerve leaves the vagus high in the neck.

Recurrent laryngeal nerve: Sensation of the subglottis and motor fibers to intrinsic muscles of the larynx. This nerve branches from the vagus in the mediastinum, then turns back up into the neck. On the right, it travels inferior to the subclavian artery and on the left, the aorta.

Figure 7 Superior view of laryngeal cartilages together with cricothyroid, quadrangular, and related ligaments and membranes.

(From Gray’s Anatomy, 39th ed. St. Louis, Churchill Livingstone/Mosby, 2004, figure 36.7, with permission.)

Laryngeal Injury

Incidence

Laryngeal and cervical tracheal injuries account for less than 1% of trauma cases seen in most major trauma centers.^2,¹⁷ These injuries are rare compared to the total number of injuries that occur to the head and neck area. Experience in managing laryngeal trauma is limited because of these small numbers. External laryngeal trauma occurs in 1/30,000 emergency room visits.^18,¹⁹ The rare nature of laryngeal injuries is a consequence of multiple factors, including protection by the mandible and sternum, delayed or missed diagnoses of minor laryngeal injuries in major multitrauma victims, and patient mortality at the scene from airway loss and asphyxiation.²⁰

Although rare, initial management of laryngeal injuries affects the immediate probability of patient survival and long-term quality of life. The larynx is a well-protected structure that is both anatomically and functionally complex. Blunt and penetrating laryngeal injuries may cause chronic problems with aspiration, phonation, and respiration.²⁰

Mechanism of Injury

The mechanisms of laryngeal injury can be divided into blunt trauma (including crushing, clothesline, and strangulation injuries) and penetrating trauma. The degree and location of blunt laryngotracheal trauma are multifactorial. Sheely et al.²¹ found that 88% of injuries occurred above the fourth tracheal ring. Penetrating injury can occur at any level of the cervical trachea.

Diagnosis

Adherence to the essential principles of initial assessment delineated in the Advanced Trauma Life Support (ATLS)® Manual is recommended. The ABCs (airway, breathing, circulation), concomitant resuscitation of the trauma victim, and a thorough secondary survey are essential for optimal management of airway injuries.²² Early recognition of these injuries requires a high index of suspicion based on mechanism of injury and findings identified during cervical and chest examination. Clinical signs and symptoms may include stridor, acute respiratory distress, cervical tenderness, subcutaneous emphysema, and cervical hematoma when associated with major vascular injury.²³ Hemoptysis suggests that an intralaryngeal laceration may be present.²³ This is more common with penetrating injury, but also occurs from blunt laryngeal trauma with an associated laryngeal cartilage fracture.²³ Diagnostic procedures such as direct laryngoscopy, fiber-optic bronchoscopy, and cervical helical, contrast-enhanced multidetector (16 slices minimum) computed tomography (CT) with angiography are all beneficial if the patient’s clinical condition permits performing these tests.^17,²⁴ A sample algorithm for the evaluation of patients with laryngeal injuries is described (Figure 8).

Figure 8 Algorithm for evaluating patient with suspected laryngeal injury. CT, Computed tomography; ORIF, open reduction with internal fixation.

(Adapted from Pancholi SS: Fractures, laryngeal. Department of Otolaryngology, Three Rivers Medical Center, Louisa, KY, November 3, 2005, http://www.emedicine.com/ent/images/ and http://www.emedicine.com/ent/topic488.htm.)

TRACHEA

Surgical Anatomy

The trachea is a cartilaginous and membranous tube. It extends from the lower part of the larynx, at the level of the sixth cervical vertebra, to the upper border of the fifth thoracic vertebra. There it divides into the two main stem bronchi. The trachea is an ellipsoid cylinder that is flattened posteriorly. The average adult trachea measures about 11 cm in length with a diameter that varies from 2 to 2.5 cm. The pediatric trachea is smaller, more deeply placed, and more mobile. Half of the trachea lies within the neck and half is intrathoracic. The anterior two thirds of the trachea are composed of 18 to 22 “U”-shaped cartilages. The membranous posterior wall of the trachea is in apposition with the anterior wall of the esophagus. The bifurcation of the mainstem bronchi forms the carina at approximately the fourth to fifth thoracic vertebrae. The trachea is supplied with blood by the inferior thyroid arteries. Similarly named veins form the thyroid venous plexus. Tracheal innervation is derived from the vagus nerves, the recurrent laryngeal nerves, and from the sympathetic chain. The recurrent laryngeal nerve lies within the tracheoesophageal groove formed by the close proximity of the lateral aspects of the trachea and the esophagus (Figures 9, 10, and 11).

Figure 9 Anatomy of the larynx, cervical, and upper thoracic trachea.

Figure 10 The cartilages of the larynx, trachea, and bronchi: anterior aspect.

(From Gray’s Anatomy, 39th ed. St. Louis, Churchill Livingstone/Mosby, 2004, figure 63.12, with permission.)

Figure 11 The respiratory tract. Those parts of the tract in the head and upper neck are shown in sagittal section, in the lower neck turned anteriorly and, in the remainder of the tract, from the anterior aspect. The right lung shows the bronchial tree in detail whereas the left lung shows the pulmonary vasculature.

(From Gray’s Anatomy, 39th ed. St. Louis, Churchill Livingstone/Mosby, 2004, figure 63.1, with permission.)

Tracheal Injury

Incidence

Disruption of the tracheobronchial tree is a rare occurrence and most surgeons’ experience is limited. On average, one such case is seen per year in large trauma centers.²⁵ Bertelsen and Howitz⁴ reviewed 1178 postmortem reports of trauma deaths and found 33 (2.8%) with tracheal and/or bronchial disruptions. Of these 33 cases, 27 were dead at the scene.⁴

Complete cervical transection is rarer still. The true incidence (and tracheobronchial injuries in general) is unknown.^26,²⁷ There have been a number of case reports and small series described in the literature; however, the extant surgical experience remains limited.²⁶

Knowledge of emergency airway management is essential. Loss of the airway in this clinical circumstance can rapidly lead to serious complications and/or the patient’s demise.^17,²⁸

Mortality in those patients who do not have complete airway loss at the time of injury is due to the severity of associated injuries. Those patients who arrive alive to a trauma center with isolated tracheobronchial injuries, including complete transection, have a reasonable chance for survival if the trauma surgeon has mastered the skills required for managing a difficult airway.²⁹

Beskin ³⁰ reported the first successful repair of a complete cervical transection after blunt trauma in 1957. Hood and Sloan³¹ in 1959 collected 18 cases of tracheobronchial injury in the world literature. Complete tracheal transection was “rarely found.” In a more recent series, Eckert et al.³ reported a total of 105 tracheobronchial injuries, of which 75 were from penetrating trauma and 30 from blunt trauma. Of these, only 24 patients survived the transfer from the scene of the accident to the trauma center. Of the 30 blunt trauma victims reported in this series, 18 were dead on arrival at the emergency department. The majority of those who arrived alive, regardless of the mechanism of injury, had no other associated injuries (15 of 24 [63%]), and the remainder had only one other associated injury, including esophageal injuries (9 of 24 [37%]).³ In the same series, the most commonly injured segment of the tracheobronchial tree in survivors was the cervical trachea (37%). The total number of complete tracheal transections in Ecker and associates’ series is unknown.

Kelly et al.⁶ reviewed 106 patients with tracheobronchial injuries of which only 6 had a blunt mechanism of injury.⁶ They concluded that a surgeon must adopt a rapid, aggressive surgical approach to these patients in order to prevent lethal outcomes.⁶

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