Pediatric Otorhinolaryngology: Diagnosis and Treatment, 1st Ed.

15

Evaluation and Management of Upper Airway Obstruction in Children

Nicholas Smith, Aliza P. Cohen, and Michael J. Rutter

Causes of airway obstruction in children encompass a wide spectrum of anomalies that may involve not only the larynx and trachea, but also other anatomic sites from the nasal vestibule to the subsegmental bronchi. This chapter presents an overview of the diagnosis and management of these anomalies, focusing on those that are commonly encountered and those that are significant, though infrequently encountered. Causes of airway obstruction will be discussed below from proximal to distal fashion anatomically.

Supralaryngeal

Congenital Nasal Pyriform Aperture Stenosis

Congenital nasal pyriform aperture stenosis (CNPAS) is a relatively uncommon developmental anomaly characterized by bony overgrowth of the medial aspect of the nasal process of the maxilla. Because the pyriform aperture is the narrowest section of the bony nasal skeleton, even minor anatomic abnormalities in the cross-sectional area of the aperture substantially affect airflow by increasing nasal airway resistance. CNPAS typically presents during the first few months of life, when infants are obligate nasal breathers. Although it sometimes occurs as an isolated anomaly, it is generally associated with a single central upper incisor.

Neonates present with a spectrum of symptoms resulting from nasal obstruction, including cyanosis, apnea, feeding difficulties, and labored breathing. These symptoms may mimic the symptoms observed in patients with bilateral choanal atresia (described further); as such, evaluation for suspected choanal atresia is sometimes performed, yielding negative results. Clinicians may thus be falsely reassured that there is no substantial nasal obstruction.

The diagnosis of CNPAS is established by anterior rhinoscopy, which reveals an anterior bony obstruction of the nasal vestibule. This is confirmed by computed tomography (CT), which may also confirm the presence of a single central upper incisor and other midline anomalies of the central nervous system.

Management depends on the severity of symptoms. In patients with mild symptoms, expectant management may be all that is required until growth results in increased nasal airway size. In more severely affected patients, surgical enlargement is indicated. This is best performed through a sublabial approach, exposing the pyriform aperture, and using a diamond burr to remove the excessive bone of the nasal process of the maxillary crest. Temporary nasal stents are generally placed for 2 to 4 weeks postoperatively.

Choanal Atresia

Although several theories of the embryogenesis of choanal atresia have been proposed, this anomaly is believed to result from the persistence of the nasal buccal membrane. The nasal obstruction may be membranous, bony, or a combination of both; however, the latter is most commonly seen. The atresia may be unilateral or bilateral, with a likely ratio of 1:1. Both unilateral and bilateral disease may be associated with other congenital anomalies; the most widely recognized association is with CHARGE syndrome (coloboma, heart defects, atresia, retardation of growth and development, genitourinary disorders, and ear abnormalities).1

Given that neonates are obligate nasal breathers during the first 6 weeks of life, apnea in children with bilateral disease may occur during quiet respiration irrespective of the underlying disease process causing the nasal obstruction. Apnea is not observed when neonates are agitated, as they breathe by mouth when crying. Once the crying subsides, they are again at risk for apnea. Complete obstruction of the posterior nasal passage by choanal atresia prevents normal drainage of nasal secretions into the nasopharynx. These secretions must therefore drain anteriorly and are characteristically copious and tenacious.

We recommend evaluating nasal passages with a thin (1.9 mm) flexible nasal endoscope. Airway management of a patient with bilateral disease is placement of an oral airway or intubation. This approach stabilizes the child until CT can be performed and, if appropriate, until genetic assessments can be performed. We advise radiologic evaluation with bone/window high-resolution, thin-section CT imaging. The quality of the image is greatly enhanced by removing all nasal sections with a soft suction catheter immediately before the scan. A thin atretic plate at the posterior choana is usually seen; this plate is often both bony and membranous. Frequently, an associated prominence of the bony margins of the choana is revealed, with bony overgrowth of the vomer in the midline or medialization of the lateral nasal walls.

Unless there are contraindications for surgery (e.g., extreme prematurity or multiple congenital anomalies), patients should undergo early surgical repair.2 Although surgical approaches may be either transpalatal or transnasal, the latter is preferable in most children. This approach involves endoscopically guided removal of the atretic plate using urethral dilators, backbiting forceps, drills, powered microdebrider cutters, or a combination of these instruments. For cases in which there is prominence of the bony margins of the choana, the posterior aspect of the vomer may be removed to form a common cavity at the level of the atretic plate. Whereas transnasal stents were formerly placed for several weeks postoperatively, the current trend is toward either shorter periods of stenting or no stenting at all. Because both options carry the risk of the patient developing secondary choanal stenosis, adjuvant therapy such as topical application of steroid nasal drops may be used.

Patients with unilateral choanal atresia are generally not diagnosed until later in childhood, when they present with unilateral rhinorrhea and nasal obstruction that necessitate a CT evaluation. Transnasal repair of the atresia is generally performed after 2 years of age. Nasal obstruction at birth in the subset of patients with choanal atresia associated with CHARGE syndrome is more severe than in other patients. Because the level of obstruction in these children is not restricted to the choana and may include pharyngomalacia, hypopharyngeal collapse, and laryngomalacia, repair of the choanal atresia may not preclude the need for tracheostomy placement. If other levels of obstruction are recognized initially, placement of a tracheostomy tube and late repair of the choanal atresia may be the most appropriate management strategy. Regardless of whether the atresia is unilateral or bilateral or whether surgical repair is undertaken early or late, outcomes are less successful in these patients.

Nasolacrimal Duct Cysts

Nasolacrimal duct cysts result from the failure of the nasolacrimal duct to recanalize during embryogenesis. This anomaly may arise either unilaterally or bilaterally. Patients typically present with nasal obstruction caused by a large cyst under the inferior turbinate, occluding the anterior nasal airway. Swelling of the nasolacrimal sac in the medial canthal area may also be observed. Epiphora is evident, as tears cannot drain. If the cyst is infected, as is frequently the case, there may be abscess formation in the nasolacrimal sac region, and the neonate may be septic. The diagnosis is established with anterior rhinoscopy and CT imaging of the nasal passages. Patients are managed by transnasal endoscopic removal or marsupialization of the cyst, with placement of nasolacrimal duct catheters if required.

Retrognathia/Glossoptosis

Retrognathia is a descriptive term for mandibular hypoplasia. A consequence of the hypoplasia is crowding of the tongue posteriorly and superiorly, which may cause airway obstruction and a cleft of the secondary palate, as the palate anlagen are unable to close around the cephalically displaced tongue. Retrognathia is associated with several abnormalities, including Pierre Robin sequence (short mandible, cleft palate), Treacher Collins syndrome (mandibulo-facial dysostosis), and Stickler syndrome. The severity of retrognathia is not always a reliable indicator of the severity of obstruction or of problems that may occur with intubation. Obstructing retrognathia generally becomes evident during the neonatal period; however, problems may develop later in life. Such problems are often triggered by incidental surgical procedures or with the insidious onset of severe sleep apnea caused by glossoptosis or adenotonsillar hypertrophy.

The management of neonates involves prone positioning and the use of high-flow nasal cannula; occasionally, a nasal trumpet is useful. Continuous positive airway pressure (CPAP) is often unsuccessful, as the mask tends to exacerbate the retrognathia. Because infants have difficulty feeding, placement of a nasogastric tube placement is often required. For children with persistent airway compromise, intubation is desirable though challenging.

In infants who suffer with significant obstructive symptoms or feeding difficulties, the standard of care is placement of a tracheotomy. In most nonsyndromic children, catch-up growth of the mandible will permit decannulation within 1 to 2 years. If catch-up is not apparent at 1 year of age, mandibular distraction should be considered.3 Although this procedure is controversial, in select cases it may be an effective alternative to tracheotomy placement. Distraction may be performed without placement of a tracheotomy tube; however, in some instances it is prudent to perform distraction while the airway is secured with a tracheotomy tube.

Because of the association between retrognathia and tracheobronchomalacia, some children continue to have symptoms of obstruction after tracheotomy placement. In this setting, performing flexible bronchoscopy through the tracheotomy tube is diagnostic, and management with CPAP, bi-level positive airway pressure, or ventilation is sometimes necessary. In infants with isolated tracheomalacia, replacing the tracheotomy tube with a longer tube that lies close to carina may be all that is required. A surgical alternative for the management of severe intrathoracic tracheomalacia is aortopexy.

Supraglottic

Laryngomalacia

Laryngomalacia is the most common cause of stridor in infants. Although stridor is generally mild, it is exacerbated by crying, excitement, feeding, or lying in a supine position. In about 10% of cases, symptoms worsen during sleep. Approximately 50% of children with laryngomalacia experience an exacerbation of symptoms during the first 6 months of life; however, virtually all children have spontaneous resolution of symptoms by 1 year of age. For children with severe laryngomalacia (5 to 10%), surgical intervention is required. Symptoms in these children may include apneic spells, cyanosis, severe retractions, and failure to thrive. In very severe cases, cor pulmonale is seen.

The diagnosis is generally confirmed by transnasal flexible laryngoscopy. Bronchoscopic evaluation is not indicated unless symptoms are severe enough to warrant intervention or the observed degree of laryngomalacia is disproportionate to the severity of the symptoms. Characteristic findings on flexible laryngoscopy include short aryepiglottic folds, with prolapse of the cuneiform cartilages (50%). In addition, a tightly curled omega-shaped (ω) epiglottis is sometimes (15 to 20%) observed. Flexible laryngoscopy may also show cricoid irritation and edema. Gastroesophageal reflux disease is frequently associated with laryngomalacia. This condition is usually managed with either an H2 antagonist or a proton-pump inhibitor.

For the subset of children who require surgical intervention, supraglottoplasty with division of the short aryepiglottic folds, and if indicated, removal of the cuneiform cartilages (if these are excessively mobile) is remarkably effective.4 If there is any risk of edema, overnight intubation is warranted. For children in whom supraglottoplasty is ineffective, consideration should be given to whether there is any underlying neurologic component. Although neurologic problems may be quite subtle initially, they may become more evident with age. This particular group of children is far more likely to require tracheotomy placement.

Cysts

Supralaryngeal cysts encompass several diverse pathologic entities, including lingual thyroglossal duct cysts, vallecular cysts, laryngoceles, and saccular cysts. These cysts typically become evident during the neonatal period and are associated with a muffled cry and apneic spells that may be life threatening.

Lingual thyroglossal duct cysts usually occur in tongue base near the epiglottis; they tend to be midline and deep to the mucosa. Although these cysts are frequently asymptomatic in older children, they may be life threatening in neonates. Affected infants require surgical intervention. A transoral cyst excision is a straightforward and effective technique for managing the disease. Special care should be taken on the induction of general anesthesia in neonates, as the airway is susceptible to complete obstruction during induction.

In contrast to thyroglossal duct cysts, vallecular cysts are thin-walled cysts near the glottic surface of the epiglottis. These cysts can easily be marsupialized.

Laryngoceles and saccular cysts occur when the laryngeal ventricle is obstructed. Although endoscopic marsupialization may be attempted, recurrence is frequent and placement of a tracheotomy is often required. An open surgical approach with dissection of the cyst through the thyrohyoid ligament enables complete cyst removal and is thus curative.

For all of these cysts, transnasal flexible laryngoscopy suggests the diagnosis and formal bronchoscopic evaluation of the airway confirms it. A CT scan with contrast enhancement is useful in ensuring that a lingual thyroid is not mistaken for a lingual thyroglossal duct cyst and delineates the extent of disease.

Supraglottic Infection

Effective pediatric immunization programs have virtually eliminated supraglottic infections such as diphtheria (a century ago) and epiglottitis (2 decades ago). The Haemophilus influenzae type B vaccination has virtually eliminated epiglottitis. Although it still occurs, it is more frequently a disease of older age groups with less acute airway obstruction or is due to less virulent organisms. While intubation of patients with these disorders may be challenging in the acute phase of disease, it is nevertheless the preferred method of securing the airway. In the event that the airway cannot be secured, the surgeon should be prepared to proceed directly to an emergent tracheotomy if required.

Glottic

Laryngeal Webs

Laryngeal webs may be either congenital or acquired. Congenital webs are a consequence of embryologic failure of laryngeal recanalization of the glottic airway in the early weeks of embryogenesis. Acquired webs are generally post-traumatic in origin, either iatrogenic in nature or the result of direct trauma or inhalational injuries. Although congenital laryngeal webs have been described in the supraglottic, glottic, and subglottic regions and may occur anteriorly or posteriorly, anterior glottic webs comprise more than 95% of cases. Associated congenital anomalies are seen in up to 60% of patients, and there is a strong association between anterior glottic webs and velocardiofacial syndrome.5 The web may be the only early manifestation of this disorder.

Congenital anterior glottic webs manifest with varying degrees of glottic airway compromise. The severity of symptoms correlates with the size and position of the web. Although some anterior glottic webs are gossamer thin, most are thick and are associated with a subglottic “sail” that compromises the subglottic lumen. Thin webs may elude detection, as neonatal intubation for airway distress may lyse the web, which is curative. In infants with moderate to severe webs, biphasic stridor and retractions become increasingly evident as the infant grows and are particularly evident when the infant is feeding or upset.

In children with minor webs, early intervention is un-warranted, though it is desirable to intervene before school age to improve voice. In children with thick webs, open reconstruction with either reconstruction of the anterior commissure or placement of a laryngeal keel is indicated.6 Intervention with the carbon dioxide (CO2) laser usually leads to recalcitrant web re-formation. The presence of thick membranous webs may require temporary placement of a tracheotomy to allow growth before elective laryngeal repair is performed. Repair is usually performed before the child reaches school age.

Vocal Cord Paralysis

Vocal cord paralysis may be congenital or acquired and unilateral or bilateral. In most cases, bilateral vocal cord paralysis is congenital. Unilateral paralysis is generally an acquired problem caused by damage to the recurrent laryngeal nerve. In view of the length and course of the left recurrent nerve, this nerve is far more likely to be damaged than the right recurrent laryngeal nerve. Risk factors for acquired paralysis are patent ductus arteriosus ligation (particularly in neonates weighing less than 1500 g), cardiac surgery, and esophageal surgery (especially tracheoesophageal fistula repair). In older children, thyroid surgery is an additional risk factor. Children with unilateral vocal cord paralysis generally have an acceptable airway, but have a breathy voice and are at a slightly higher risk of aspiration. For the most part, these children ultimately become asymptomatic with compensation of the functional vocal cord and do not require surgical intervention.

Congenital cord paralysis is usually idiopathic, but may also be associated with central nervous system pathology such as hydrocephalus and Chiari malformation of the brainstem. When the underlying cause is corrected, the paralysis may be reversible. Most children with bilateral vocal cord paralysis present with significant airway compromise, but have an excellent voice and usually do not aspirate unless there are associated central nervous system abnormalities.

In an infant with stridor and retractions caused by bilateral vocal cord paralysis, placing a tracheotomy is indicated. Stabilization can be achieved with intubation, with CPAP, or high-flow nasal cannula as an alternative temporizing measure. Up to 50% of children with congenital idiopathic bilateral vocal cord paralysis have spontaneous resolution of their paralysis by 1 year of age.7 Surgical intervention to achieve decannulation is thus usually delayed until after 1 year. Similarly, children with acquired bilateral vocal cord paralysis may have spontaneous recovery several months after recurrent laryngeal nerve injury if the nerve is stretched or crushed but otherwise intact.

Because no particular surgical approach for managing bilateral paralysis yields a universally acceptable outcome, several surgical options have been used.8 The aim of surgery is twofold: (1) to achieve an adequate decannulated airway while maintaining voice and (2) to prevent aspiration. Surgical options include laser cordotomy, partial or complete arytenoidectomy (endoscopic or open), vocal process lateralization (open or endoscopically guided), and posterior cricoid cartilage grafting. In a child with a tracheotomy, it is often desirable to maintain the tracheotomy to ensure an adequate airway before decannulation. In a child without a tracheotomy, a single-stage procedure can be performed.

Acquired bilateral vocal cord paralysis is usually more recalcitrant to treatment than idiopathic cord paralysis, and more than one procedure may be required to achieve decannulation. In patients who have undergone any such procedures, postextubation stridor may respond to CPAP or high-flow nasal cannula. A child's postoperative risk of aspiration should be assessed by a video swallow study before resuming a normal diet. During the initial weeks following surgery, there is sometimes an increased aspiration risk with certain food textures, particularly thin fluids.

Posterior Glottic Stenosis

Although posterior glottic stenosis (PGS) is usually a consequence of prolonged intubation, other contributing synergistic factors include endotracheal tube size, patient agitation, laryngeal inflammation, and oral tube placement. Because these are also risk factors for the development of subglottic stenosis (SGS), both conditions frequently coexist. Cricoarytenoid fixation may also coexist and may mimic PGS. Furthermore, PGS may mimic bilateral vocal cord paralysis. The diagnosis is best made by performing rigid bronchoscopy, with an attempt to splay the vocal cords. Flexible bronchoscopy is not a reliable diagnostic tool in this condition.

Although several schemas for classifying the severity of PGS have been proposed, the system put forth by Bogdasarian and Olson9 is the most widely used. These authors divide PGS into four types and advocate a graded surgical approach based on the extent of the pathology. PGS is best treated through an open approach, with the division of the posterior plate of the cricoid and placement of a cartilage graft to distract the scar tissue while remucosalization and healing occur. If associated SGS is present, an anterior graft may also be placed if required. In selected cases of isolated PGS, the posterior cartilage graft may be placed endoscopically.10

Clinical outcomes in children with PGS are not as impressive as those achieved in children with SGS; patients with PGS have been found to have a restenosis rate of at least 15%.11 Success rates are markedly improved for children with interarytenoid adhesions (Bogdasarian and Olson type I), as the interarytenoid scar band responds well to endoscopic excision.

Papillomatosis

Recurrent respiratory papillomatosis (RRP), also referred to as juvenile laryngeal papillomatosis, is the most common infective lesion of the larynx in children. The etiology of RRP is infection of the upper airway with human papillomavirus (HPV) types 6 and 11, and less commonly, types 16 and 18. RRP is frequently associated with transplacental transmission of maternal HPV; however, contact with active cervical HPV during delivery is also considered a causal factor. Although genital papillomas are extremely common, RRP is extremely rare and the relative risk of acquiring RRP is low.

Nearly 75% of children with RRP are diagnosed by age 5. Although the condition typically presents with hoarseness, stridor caused by airway obstruction is also common and often precipitates otolaryngologic referral. Initial evaluation is performed with flexible transnasal laryngoscopy, which may reveal a laryngeal mass; however, microlaryngoscopy and bronchoscopy with biopsy of the papillomas are required for a definitive diagnosis and for serotyping lesions for prognostic purposes. Serotypes 16 and 18 are associated with more aggressive disease and a higher risk of malignant transformation.

Although the course of the disease is both variable and unpredictable, RRP tends to recur locally and, in severe cases, spreads throughout the respiratory tract. Surgical intervention should be based on debulking gross disease without attempting complete removal of the affected tissue, so as to avoid laryngeal scarring or stenosis. The most widely used surgical procedure is suspension laryngoscopy with tumor removal using the CO2 laser, microforceps, or the microdebrider. In patients with extensive disease, surgery should be aimed at reducing the tumor burden, decreasing the spread of disease, creating a patent airway, improving voice quality, and lengthening the intervals between surgical interventions. In children with severe RRP, tracheotomy placement may be required; however, this is often at the cost of disseminating disease beyond the glottis.

Cidofovir and bevacizumab are currently the most enthusiastically embraced adjunctive treatment modalities. However, innoculation with polyvalent HPV vaccine is the brightest hope for the future.

Subglottic

Subglottic Cysts

Subglottic cysts are most commonly a consequence of the prolonged intubation of a premature infant. These cysts are often multiple, and may be superficial and thin walled or may lie deep in the submucosal layer. Although the pathogenesis of subglottic cysts is unlike that of SGS, both problems may coexist. Management includes deroofing the cyst using microlaryngeal instrumentation, powered instrumentation, CO2 laser, or Bugbee electrocautery. As subglottic cysts tend to recur, follow-up bronchoscopy is essential. Removal may need to be performed on several occasions before complete resolution is attained.

Subglottic Hemangioma

Subglottic hemangiomas are the most common neoplasm affecting the airway in children. These lesions follow the same natural history as their cutaneous counterparts, having a phase of proliferation followed by a phase of spontaneous involution; however, subglottic lesions expand and involute more rapidly. They typically proliferate during the first 12 months of life and spontaneously regress over an additional 12 months or more. Most patients present in the first few weeks or months of life, and the earlier the presentation, the more severe the problem and the higher the likelihood that intervention will be required. Although 50% of children with a subglottic hemangioma also have a cutaneous hemangioma, the risk of having a subglottic hemangioma if a cutaneous hemangioma is present is generally very low. An exception to this is hemangiomas that arise in a beard distribution; 65% of patients with these lesions have associated airway involvement.12

The classic symptoms of subglottic hemangioma include progressive stridor and retractions, often exacerbated by upper respiratory tract infections. Worsening respiratory difficulty in an infant demands a transnasal flexible laryngoscopy with the patient awake. The most common laryngeal pathologies (laryngomalacia, vocal cord paralysis, laryngeal cysts) are clearly visible. If, however, there is not a clear cause for the stridor, airway films and a rigid bronchoscopy are indicated. Airway films show a subglottic narrowing, which is frequently asymmetric. On bronchoscopy, the hemangioma always looks more impressively obstructive than the child's clinical presentation suggests. The hemangioma is compressible, may have vascular markings, and more commonly arises to the left of the midline. It is important to perform the bronchoscopy with the patient under spontaneous ventilation, while avoiding intubation, as this may compress the lesion, making diagnosis more challenging. Biopsy is not indicated. A deeply seated subglottic hemangioma may be confused with a subglottic cyst.

Airway compromise frequently occurs before involution, thus necessitating intervention. Over the past decade, the management of subglottic hemangioma has evolved significantly, and a wide range of interventions and treatment approaches have been reported. Currently, first-line management involves a trial of propranolol, with surgery (tracheotomy or open excision) being reserved for patients who are unresponsive to treatment.13

SGS

SGS can be either congenital or acquired. Congenital SGS is comparatively rare and is thought to result from failure of the laryngeal lumen to recanalize; it is one of a continuum of embryologic failures that include laryngeal atresia, stenosis, and webs. In the neonate, SGS is defined as a lumen 4 mm in diameter or less at the level of the cricoid. Acquired SGS is more common and is generally a sequela of prolonged intubation of the neonate. A useful and practical guide is that the outer diameter of a 3.0 endotracheal tube is 4.3 mm, and if air leaks around the tube at less than 20 cm of subglottic pressure of water, the subglottis is not stenotic.

Levels of disease severity are graded according to the Myer-Cotton grading system (grades I to IV), with grade I ranging from no obstruction to 50% obstruction and grade IV being no detectable lumen.14Mild SGS may manifest in recurrent upper respiratory infections (often diagnosed as croup) in which minimal subglottic swelling precipitates airway obstruction. More severe cases may present with acute airway compromise at delivery. If endotracheal intubation is successful, the patient may require intervention before extubation. When intubation cannot be achieved, tracheotomy placement at the time of delivery may be life-saving. It is important to note that infants typically have few symptoms, and because growth of the child exceeds growth of the airway, even those with grade III stenosis may not be symptomatic for weeks or months.

Congenital SGS is often associated with other congenital head and neck lesions and syndromes (e.g., a small larynx in a patient with Down syndrome). After initial management of SGS, the larynx will grow with the patient and may not require further surgical intervention; however, if initial management requires intubation, there is considerable risk of developing an acquired SGS in addition to the underlying congenital SGS.

Radiologic evaluation of an airway that is not intubated may give the clinician clues about the site and length of the stenosis. The single most important investigation is a high-kilovoltage airway film. This is taken not only to identify the classic “steepling” observed in patients with SGS, but also to identify possible tracheal stenosis.

Evaluation of SGS, whether it is congenital, acquired, or a combination of both, requires endoscopic assessment; ideally, this is done with a Hopkins rod rigid telescope. Precise evaluation of the endolarynx should be performed, including grading of the SGS. Stenosis caused by scarring, granulation tissue, submucosal thickening, or a congenitally abnormal cricoid can be differentiated from SGS with a normal cricoid, but endoscopic measurement with endotracheal tubes or bronchoscopes is required for an accurate evaluation.

The greatest risk factor for developing acquired SGS is prolonged intubation with an inappropriately large endotracheal tube. The appropriate endotracheal tube size is not the largest that will fit, but rather the smallest that allows for adequate ventilation. Ideally, the tube should leak air around it, with subglottic pressures below 25 to 30 cm of water. Other cofactors for the development of acquired SGS include gastroesophageal reflux and eosinophilic esophagitis.

Children with mild acquired SGS may be asymptomatic or minimally symptomatic. Observation rather than intervention may thus be appropriate. This is often the case for children with grades I or II disease. Those with more severe disease are symptomatic, with either tracheal dependency or stridor and exercise intolerance. Unlike congenital SGS, acquired stenosis is unlikely to resolve spontaneously and thus requires intervention. In children with mild symptoms and a minor degree of SGS, endoscopic intervention may be effective, with scar division and balloon dilation being the most effective approach.

More severe forms of disease are better managed with open airway reconstruction. Laryngotracheal reconstruction using costal cartilage grafts placed through the split lamina of the cricoid cartilage is reliable and has withstood the test of time.15,16 Costal cartilage grafts may be placed through the anterior lamina of the cricoid cartilage, the posterior lamina of the cricoid cartilage, or both. This is usually performed as a two-stage procedure, maintaining the tracheal tube and temporarily placing a suprastomal laryngeal stent above the tracheal tube. Alternatively, in selective cases, a single-stage procedure may be performed, with removal of the tracheal tube on the day of surgery and with the child requiring intubation for a 1- to 14-day period. For the management of severe SGS, better results may be achieved with cricotracheal resection (CTR) than with laryngotracheal reconstruction; however, CTR is a technically demanding procedure that carries a significant risk of complications.17

Patients should be optimized before undergoing surgery. Preoperative evaluation includes assessment and management of gastroesophageal reflux, eosinophilic esophagitis, and low-grade tracheal infection, particularly methicillin-resistant Staphylococcus aureus and Pseudomonas.

Tracheal

Complete Tracheal Rings

Complete tracheal rings are a rare but life-threatening anomaly. They present with insidious worsening of respiratory function over the first few months of life and with stridor, retractions, and marked exacerbation of symptoms during intercurrent upper respiratory tract infections. Children with distal tracheal stenosis usually have a characteristic biphasic wet-sounding breathing pattern that transiently clears with coughing. The risk of respiratory failure increases with age. Over 80% of children with complete tracheal rings have other congenital anomalies that are usually cardiovascular in origin.

Although the diagnosis is established with rigid bronchoscopy, an initial high-kilovolt airway radiograph may reveal tracheal narrowing. Bronchoscopy should be performed with great caution, using the smallest possible telescopes, as any airway edema in the region of the stenosis may turn a narrow airway into an extremely critical airway. The location, extent, and degree of stenosis are all relevant; however, if the airway is exceptionally narrow, it may be more prudent just to establish the diagnosis rather than risk-causing posttraumatic edema by forcing a telescope through a stenosis. As 50% of children have a tracheal inner diameter of about 2 mm at the time of diagnosis, the standard interventions for managing a compromised airway are not applicable. More specifically, the smallest endotracheal tube has an outer diameter of 2.9 mm and the smallest tracheotomy tube has an outer diameter of 3.9 mm; as such, the stenotic segment cannot be intubated. Extracorporeal membrane oxygenation may thus be left as the only viable alternative for stabilizing the child. This situation is best avoided by performing bronchoscopy with the highest level of care. In view of frequent cardiovascular anomalies, investigation should include a high-resolution, contrast-enhanced CT scan of the chest and an echocardiogram.

Most children with complete tracheal rings require tracheal reconstruction.18 The recommended surgical technique is the slide tracheoplasty.19 This approach yields significantly better results than any other form of tracheal reconstruction and is applicable to all anatomic variants of complete tracheal rings.

Tracheomalacia

Tracheomalacia is the most common congenital tracheal anomaly. Most children are either asymptomatic or minimally symptomatic, and most cases involve posterior malacia of the trachea, with associated broad tracheal rings. Commonly associated abnormalities include laryngeal clefts, tracheoesophageal fistulae, and bronchomalacia. Presenting symptoms include a honking cough, wheezing, dying spells, and respiratory distress when agitated.

The diagnosis is established with rigid or flexible bronchoscopy, while maintaining spontaneous respiration. The key elements of diagnosis include: (1) ascertaining the severity of the malacia; (2) ascertaining the location of the malacia, particularly the possible presence of associated bronchomalacia; and (3) determining whether positive pressure support improves the malacia. Mild tracheomalacia improves with time and is therefore managed expectantly; however, more severe cases warrant intervention.20 Tracheotomy placement, with the tip of the tracheotomy tube bypassing the malacic segment, remains the most common intervention. Positive pressure support delivered down the tracheotomy tube assists with associated bronchomalacia. An alternative surgical procedure for isolated tracheomalacia is aortopexy, with thymectomy and anterior suspension of the ascending arch of the aorta to the posterior periosteum of the sternum. Although the placement of intratracheal stents is alluring, it is presently discouraged.

Conclusion

Obstruction of the pediatric airway is often best considered anatomically in a proximal to distal fashion. Obstruction at or above the vocal folds may be rapidly and safely evaluated with transnasal flexible laryngoscopy at the bedside in an awake child. If no pathology is found, then by implication the pathology is more distal and rigid bronchoscopy in an anesthetized child is indicated. Given that most causes of pediatric airway obstruction are proximal, operative evaluation is required only in a minority of cases.

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