Anatomic considerations are discussed in Box 234.1.

Stridor is a high-pitched, musical sound that is produced by airflow turbulence resulting from partial obstruction of the airway. It must be differentiated from other airway sounds, such as stertor, wheezes, rhonchi, and rales. Although the etiology of stridor is multifactorial, often the location of the airway obstruction can be determined by careful listening. For example, inspiratory high-pitched stridor with a relatively normal voice usually denotes supraglottic obstruction; biphasic (inspiratory and expiratory) stridor of intermediate pitch is heard with glottic or subglottic obstruction; and expiratory stridor associated with a “barking” cough indicates intrathoracic tracheal obstruction.

Congenital laryngeal stridor or laryngomalacia is the most common form of stridor in infants and accounts for approximately 80% of all cases of pediatric stridor. It is characterized by an inspiratory, harsh, high-pitched stridor that arises from medial prolapse of the epiglottis, aryepiglottic folds, or arytenoid cartilages (Fig. 234.6). Usually, the tissues obstructing the laryngeal inlet are the aryepiglottic folds and the arytenoids (67% of cases), although combined posterior and anterior obstruction caused by the arytenoids and epiglottis, respectively, is not an infrequent finding (30% of cases). However isolated, anterior (epiglottic) obstruction is rare (fewer than 3%). The pathophysiology of laryngomalacia includes poor neurologic control or hypotonia, redundant laryngeal soft tissue, and inadequate cartilaginous support (hence the name laryngomalacia or soft larynx). The differential diagnosis includes subglottic stenosis, vocal cord paralysis, and tracheomalacia, a relatively rare disorder presenting either as idiopathic tracheomalacia or as secondary to extrinsic compression, often from a vascular malformation.

Nearly always, laryngomalacia is noticed within the first few weeks or months of life, and an initial diagnosis of laryngomalacia made after the age of 2 years should be questioned. The stridor is intermittent and mild and occasionally becomes exacerbated by crying, supine positioning, and upper respiratory infections. Cyanosis, hoarseness, feeding difficulties, atypical stridor, failure to thrive, and apneic spells indicate the need for a complete diagnostic evaluation and possible operative intervention. However, most cases resolve spontaneously by the time this child reaches age 12 to 18 months.

The diagnosis of laryngomalacia can be made with a high degree of certainty on the basis of an office examination complemented by flexible fiberoptic laryngoscopy. Although some investigators recommend that all children with laryngomalacia undergo direct laryngoscopy and bronchoscopy, or flexible fiberoptic bronchoscopy, to rule out concomitant airway disease, a review by Mancuso and colleagues reported a significant second airway lesion in only 4% of 233 children with laryngomalacia. More importantly, the nine children with other airway lesions had atypical histories and unusual stridor. Although prudence would prompt evaluation of the entire airway in infants with laryngomalacia, unless the pattern of


obstruction of the airway suggests that the laryngomalacia is unusually severe or otherwise atypical, routine direct laryngoscopy and bronchoscopy or flexible fiberoptic bronchoscopy are not cost effective.

Gastroesophageal reflux disease (GERD) also may play a role in stridor and laryngomalacia. Little and associates reported on the high incidence of GERD in children with laryngeal anomalies, in particular laryngomalacia, as compared with children without laryngeal disorders. Possible explanations for this association include GERD-induced triggering of neurologic laryngeal reflex pathways, GERD-induced mucosal edema, or secondary aspiration. These data suggest that in children with severe laryngomalacia, evaluation of GERD with video swallow studies or a 24-hour pH probe should be considered.

Treatment of laryngomalacia usually is unnecessary, and reassurance to parents is all that is required. Approximately 90% of children will experience a slow resolution of their stridor over the course of time without intervention. Indications for intervention in the remaining 10% of the population with laryngomalacia include significant respiratory compromise and failure to thrive. Respiratory compromise is considered when children demonstrate severe stridor as well as retractions with evidence of desaturations by oximetry. Failure to thrive sometimes can result from the significant increase in the overall work of breathing these children require. All children with laryngomalacia should be monitored closely for appropriate weight gain, and those failing to obtain target gains should be returned to their consulting otolaryngologist for treatment.

Surgical therapy for laryngomalacia can be directed at removing the redundant supraglottic tissue (endoscopic, often laser-assisted, ablation of excess supraglottic tissue, a so-called supraglottoplasty) or bypassing the larynx (tracheotomy). The former intervention has come to the forefront and is 70% to 90% effective in resolving airway obstruction and obviating a tracheotomy. Postoperative complications are minimal, and no long-term morbidity has been reported. Tracheotomy is the treatment of choice for supraglottoplasty failures as well as for those children with concomitant disorders such as cardiovascular anomalies, pulmonary disease, or other airway lesions that require airway stabilization.

Laryngeal stenosis is a term used to describe the presence of airway compromise involving the glottic or subglottic larynx. Although it is rare, supraglottic laryngeal stenosis also can occur. In most instances, glottic and subglottic stenoses result from prolonged intubation; however, some children who never have been intubated have subglottic stenosis secondary to a congenitally small airway. Congenital subglottic stenosis can be diagnosed with certainty only before any attempt at intubation. Although no one knows the proportion of intubated neonates who have laryngeal stenosis because of a preexisting subglottic stenosis, the size of the subglottis does vary. In approximately 1% of children, the larynx is one endotracheal tube size (1 mm) smaller than predicted; in 0.06%, the larynx is three tube sizes (1.5 mm) too small. Doubtless, some intubated infants have a smaller-than-normal larynx and therefore a greater risk for sustaining damage from an endotracheal tube. Although endoscopy is required to assess the larynx properly and to determine its size, preintubation laryngoscopy is not practiced; instead, the intubating physician must use gentle pressure to size the larynx with the selected endotracheal tube. If the fit seems tight, a smaller tube should be used. Ideally, the endotracheal tube should allow an audible leak at or below a pressure of 20 cm H₂O. Cuffed endotracheal tubes can obscure measurements of leak pressure and rarely are required in small children. Congenital stenosis at the subglottic level usually is secondary to a cartilaginous abnormality. Typically, the cricoid circumference is smaller than normal and somewhat flattened (Box 234.2). Another common finding is telescoping of the first
tracheal ring within the cricoid cartilage and, as a consequence, narrowing of the airway. In addition, compromise of the soft tissue airway occurs if increased amounts of connective tissue or numerous hyperplastic-dilated mucous glands encroach on the subglottic lumen.