Management of Laryngotracheal Obstruction in Children

Congenital Subglottic and Tracheal Stenosis

The third most common (10–15%) congenital laryngeal anomaly after vocal cord paralysis (not described in this chapter) and laryngomalacia is a congenital narrowing of the subglottic space of <4 mm (in a full-term newborn). The anatomy of the pediatric airway has been compared with an inverted cone, with the trachea fitting telescopically into the cricoid above it, the cricoid into the thyroid cartilage, and then the thyroid cartilage into the hyoid space ( Fig. 21.2 ). Congenital subglottic stenosis is the most common morphologic abnormality and presents as a narrowing of the airway at the distal end of the larynx, just at the beginning of the trachea. The subglottic region lies at the level of the cricoid cartilage, which is normally the only complete cartilaginous ring in the airway. Congenital subglottic abnormalities result in elliptical narrowing of the cricoid cartilage, the etiology of which is not known.

When compared with that of an adult, the anatomy of the trachea and larynx of a child differs in several ways ( Fig. 21.3 ). The child’s epiglottis is short and small, and the valleculae are shallow. In addition, the larynx points posteriorly, and the arytenoid apparatus is large in relation to the lumen of the larynx. Finally, the narrowest point of the normal pediatric airway is the subglottis, but is the glottis in adults.

In the normal trachea, the cartilaginous rings are horseshoe shaped, with the posterior wall composed of connective tissue and the trachealis muscle. Thus, the lumen may change as the trachea expands or contracts with respiration. Long congenital stenotic segments in the trachea are usually the result of complete cartilaginous tracheal rings. When complete cartilaginous rings are present, the lumen is rigid and much smaller than the normal trachea. If it does not produce early respiratory distress, complete cartilaginous rings may be detected when an inflammatory process within the trachea produces mucosal edema, which further compromises the lumen and results in acute airway obstruction. On occasion, tracheal intubation for an elective operative procedure can be difficult and the narrowed segment is discovered unexpectedly.

The patient’s symptomatology is variable and is related to the degree of stenosis. It may manifest as mild stridor at birth or severe obstructive symptoms requiring an emergency tracheostomy ( Fig. 21.4 ). Congenital subglottic stenosis usually causes biphasic stridor with a more prominent inspiratory phase. The condition is characterized by recurrent episodes of croup.

Operative repair of this condition should be considered around 1 year of age. The type of reconstructive technique will depend on the morphology of the stenosis. It can consist of laryngotracheal reconstruction with either an anterior and posterior cartilage graft or a cricoid-tracheal resection procedure. The latter consists of resection of the anterior cricoid arch and anastomosis between trachea and cartilage thyroid.

Laryngeal Webs

Diaphragms or congenital laryngeal webs are the result of an incomplete recanalization of the primitive larynx. All patients present some degree of dysphonia, from mild hoarseness to aphonia. Airway symptoms increase with the extension of the web. There are two types of congenital webs: one type corresponds to a thin membrane in the glottis while the other is a thick web that extends into the subglottic region. They are uncommon and represent only 5% all congenital anomalies of the larynx. There is an association with velocardiofacial syndrome, characterized in some cases by a microdeletion of chromosome 22q11.

Acquired webs are usually post-intubation and are characterized by the presence of a scar or synechia between the vocal cords. Most of the laryngeal webs have an associated congenital subglottic stenosis and thickening of the cricoid cartilage, especially grades III and IV. According to Cohen’s classification, they can be grouped into four types, based on morphology and the degree of laryngeal obstruction ( Figs. 21.5 and 21.6 ). The initial diagnosis is made with an awake nasolaryngoscopy, which will rule out other diagnoses such as laryngomalacia or vocal cord paralysis. Further evaluation may require a rigid laryngoscopy in the operating room under general anesthesia with spontaneous ventilation.

Given the wide variety of laryngeal webs, many surgical options exist and should be carefully selected depending on the type. A newborn with a severe obstruction of the airway during the first hours of life characteristically corresponds to a web with severe obstruction of the glottic space. In such cases, an emergency surgical intervention (tracheostomy) is required to secure the airway. Endoscopic web division can be performed in patients with thin diaphragms.

In thick webs, with mild to moderate symptoms, we suggest delayed repair, after 1 year of age, because it is technically easier. The initial tracheostomy to bypass the obstruction also allows the child to grow with planning for repair at an older age.

Open repairs for most type III and IV webs should be done in two stages that include web division and enlargement of the subglottic space with cartilage grafts. We usually perform an open operation with laryngeal stent placement using an LT Mold (Bredam SA, Switzerland) and a temporary tracheostomy. In our experience, the LT Mold allows for better epithelialization and minimizes recurrences. At 6–8 weeks after placement, the LT Mold is removed endoscopically and later the tracheostomy is closed.

In type III and IV webs, an anterior and posterior cartilage graft is needed to enlarge the subglottic space. In severe type IV, a partial cricoid tracheal resection is another alternative. As previously mentioned, in mild forms (type I and II), endoscopic surgery is the technique of choice and entails division of the web. A silicone “stent” is typically left between the edges to avoid recurrence.

Acquired Subglottic and Tracheal Stenosis

Acquired airway malformations usually result from intrinsic injury with subsequent inflammation, ulceration, and scarring, leading to subglottic or tracheal scarring and narrowing. Occasionally, trauma is the initiating event, but an iatrogenic event can exacerbate an unstable situation. For example, a child with a congenitally small airway might be asymptomatic until an endotracheal tube is inserted. The tube may be appropriate in size, but because of the congenital stenosis, it will fit tightly and can lead to ulceration and stricture. Particularly difficult to treat are those injuries that occur well below the subglottic region, usually produced by an endotracheal balloon that caused compression and ulceration in the trachea. Frequently, these areas of injury are below the usual site for a tracheostomy. The cuff may even erode into overlying vessels ( Fig. 21.7 ).

Vascular Compression

Compression and partial obstruction of the trachea can be caused by abnormalities of the aortic arch that impinge on, or encircle, the trachea or esophagus (or both). When both the trachea and esophagus are compressed, swallowing frequently produces airway compression and respiratory symptoms. Vascular rings are often asymptomatic in neonates and infants, yet can lead to significant airway obstruction in a young child.

The physiologic impingement on the trachea by a vascular ring is similar to that seen in patients after repair of esophageal atresia. The persistently distended upper esophageal pouch can displace the trachea anteriorly, producing tracheomalacia ( Fig. 21.8 ). Particularly with swallowing, the distended esophageal pouch can compress the trachea against the innominate artery ( Figs. 21.9 and 21.10 ). Correction of this problem centers on anterior mobilization and suspension of the innominate artery ( Fig. 21.11 ). The treatment of a pulmonary vascular sling may require not only relocation and reimplantation of the pulmonary artery, but also repair of the stenotic distal trachea as well.

Stridor and dyspnea are symptoms that can be produced by vascular impingement on the trachea. Patients with severe compromise from a double aortic arch are usually symptomatic, but their manifestations are variable ( Fig. 21.12 ). Some patients are seen with frequent coughing episodes and stridor accompanied by dyspnea and cyanosis, whereas small infants may have apneic episodes. The symptoms of vascular impingement on the trachea are usually more dramatic than those from compression of the esophagus.

Classically, vascular ring anomalies are diagnosed on a barium esophagogram with indentations on the esophageal column of barium and a decrease in the tracheal air column. Offset of the axis of the barium column above and below the indentation is diagnostic of a double aortic arch ( Fig. 21.13A ). More recently, rapid computed tomographic (CT) scans allow a graphic reconstruction of the trachea and adjacent vessels ( Fig. 21.13B ). Magnetic resonance imaging (MRI) enhanced with intravenous administration of a contrast agent allows excellent visualization of the trachea and vessels as well.

Occasionally, a child will appear with acute airway obstruction or other medical problems requiring intensive care, during which endotracheal intubation and a concomitant nasogastric tube are inserted. The presence of tubes in both airway and the esophagus makes detection of a vascular ring difficult and can generate complications. In a child who is already intubated, performance of contrast radiographic procedures may not be possible. Ultrasonography (US), CT, or contrast-enhanced MRI may delineate the vascular abnormality. When both tracheal and esophageal intubations are necessary in a patient with a double aortic arch, the encircling vessels may sustain pressure necrosis. Erosion into the aortic arch can produce an aortoesophageal fistula that may not be evident until either the endotracheal or the esophageal tube is removed. A sentinel hemorrhage can occur before a massive, and often fatal, hemorrhage occurs into the esophagus. The passage of a Sengstaken–Blakemore tube with inflation of the esophageal balloon can be lifesaving by tamponading the fistula. Because no reliable diagnostic study is available to demonstrate an aortoesophageal fistula, the observation of a sentinel hemorrhage in such a patient with US confirmation of a double aortic arch is a clear indication for urgent cardiopulmonary bypass and repair.

Vascular rings cause airway constriction and not vascular problems. Thus, simple division of the vascular ring is often not enough to relieve tracheal compression. Following division of a vascular ring, if part of the ring continues to compress the airway, it should not be dissected away from the trachea but suspended anteriorly, often to the posterior table of the sternum. The vascular-tracheal attachments will lift the anterior tracheal wall and enlarge the lumen (see Fig. 21.11 ). Traditionally, an open operation has been used for vascular ring repair. Significant numbers of patients are now being treated by the thoracoscopic approach. Regardless of the approach, whether from the right or from the left, or other technical variations, the recurrent laryngeal and phrenic nerves need to be identified and protected. Flexible endoscopic observation of the trachea during these maneuvers can corroborate relief of the compression.