Evaluation and Management of the Pediatric Airway

Assessment of a Child with Noisy Breathing

Physical Examination

The examination of the child begins with an overall assessment of size relative to age, level of distress, retractions, posturing, irritability, level of fatigue, and skin color. Evidence of syndromic features should be noted. Severe obstruction may be inferred by the type and anatomic level of retractions, including nasal flaring, suprasternal retractions, subcostal retractions, and intercostal retractions; the latter reflect the recruitment of additional chest muscles for respiration. It is important to note that the presence of retractions may be more indicative of the degree of airway obstruction than the volume or severity of stridor. Deep retractions should stimulate a prompt evaluation, as this may be suggestive of severe airway obstruction even in the absence of stridor. Altered voice quality may lead to a higher suspicion for a laryngeal process, especially if the child is aphonic, has a muffled voice, or does not generate a cough. Dysphonia that later progresses to stridor is often an ominous sign and may reflect an expanding or enlarging supraglottic or glottic mass. The phase of stridor should be determined by timing with chest motion. A complete head and neck examination and auscultation of the chest should be performed. Nasal and nasopharyngeal patency can be inferred when fog is seen on a mirror held under each nostril.

Endoscopy

Dynamic evaluation of the larynx by flexible laryngoscopy is best performed in the patient who is awake to allow for the assessment of vocal fold mobility, as well as for the identification of static or dynamic lesions above the level of the subglottic larynx. Although visualization of the subglottis is often possible, pathology distal to the vocal folds is difficult to assess completely. Developmental advances in high-resolution flexible laryngoscopes now allow for superb imaging capability using endoscopes with an outer diameter smaller than 2.5 mm. Occasionally, for the purposes of neonatal intubation or in the setting of narrow nasal airways, the use of smaller fiberoptic endoscopes is required. Viewing the laryngeal examination from a monitor allows for a magnified view of the pediatric larynx and is useful for documentation purposes. The ability to record and review the examination in a frame-by-frame fashion and to perform stroboscopy greatly aids in the evaluation of the dynamic pediatric larynx. Such examination has become the standard of care at large centers, and additional three-dimensional (3D) viewing technology and virtual reality consoles now allow for patient interaction or distraction, as well as parent education during the examination.

Direct laryngoscopy with a telescope or microscope continues to provide the best optics when visualizing the larynx and trachea ( Fig. 27.1 ) and is a major component of the complete assessment of the pediatric airway. Although awake flexible laryngoscopy is a necessary and appropriate means to evaluate for dynamic lesions of the glottis and supraglottis, distal lesions are more difficult to characterize and the larynx cannot be manipulated or sized using this technique. Likewise, if stridor is appreciated on examination but a source of stridor is not visible on flexible laryngoscopy, distal pathology should be suspected and assessed by bronchoscopy. Direct laryngoscopy and bronchoscopy require general anesthesia, often performed by a pediatric anesthesia team familiar with techniques to provide spontaneous respirations that allow for a full evaluation of the airway before intubation or airway manipulation is performed. The endoscopist should completely evaluate the oropharynx, hypopharynx, and larynx and document all findings in a systematic fashion. Bronchoscopy can be completed with a Hopkins rod alone or with a ventilating bronchoscope, evaluating the trachea and bronchi and capturing high-resolution images.

Laryngomalacia

The most common cause of stridor during infancy is laryngomalacia (LM). Premature Hispanic and black infants of all gestational ages are at higher risk for this laryngeal anomaly. The newborn with LM typically develops intermittent inspiratory stridor within the first 2 weeks of life, which resolves slowly over several months. For infants who are not managed operatively, the median time to spontaneous resolution of stridor is 7 to 9 months of age, and the vast majority will have no stridor by 18 months of age. ^,

Many authors describe the stridor of LM as high-pitched, but compared with the stridor of vocal cord paralysis, it is often relatively low in pitch and does not have a musical quality. The stridor frequently worsens with feeding, and the infant may have to take breaks while feeding to breathe. The stridor of mild-to-moderate LM often improves with crying, because tone in the pharynx is increased; conversely, in severe LM, the stridor will typically worsen with crying because of the increased airflow through the severely collapsed larynx. Infants with severe LM have been found to have shorter aryepiglottic folds compared with infants without LM. LM may be an isolated finding in the otherwise healthy infant, or it may be associated with other neurologic disorders such as cerebral palsy.

The inspiratory stridor of LM results from collapse of the supraglottic larynx, which creates a narrow airway and turbulent airflow ( Fig. 27.2 ). The etiology of this collapse has been elusive, but it appears to be related to neuromuscular hypotonia. Sensorimotor integration of peripheral sensory afferent reflexes, brainstem function, and the motor efferent response are responsible for laryngeal function and tone. The laryngeal adductor reflex (LAR) is a vagal nerve–mediated reflex activated by sensory stimulation of the mechanoreceptors and chemoreceptors of the superior laryngeal nerve located in the region of the aryepiglottic fold. Dysfunction anywhere along the afferent, brainstem, or efferent pathway of the LAR can result in altered laryngeal tone and function. Infants with LM have been found to have elevated laryngopharyngeal sensory thresholds, consistent with altered sensorimotor integrative function of the larynx, likely leading to the weak laryngeal tone seen in infants with LM. In addition, pathologic specimens of surgically resected supraarytenoid tissue have demonstrated nerve hypertrophy compared with controls, which supports the theory of neurologic dysfunction as the etiology of LM.

The diagnosis of LM requires an endoscopic examination; however, the optimal type of endoscopic examination is somewhat controversial. If the patient is sedated during flexible laryngoscopy, there may be increased collapse of the arytenoids and folding of the epiglottis during inspiration, which could lead to overestimation of the severity of LM. These findings suggest that the optimal way to diagnose LM is with flexible laryngoscopy in the awake patient. Conversely, the awake technique has been found to miss mild LM or lead to overdiagnosis in the patient with a normal airway. The advantages of awake flexible laryngoscopy compared with flexible laryngoscopy under general anesthesia include the ability to perform the examination expediently in the clinic setting with the parents present and avoidance of sedation, which reduces medical expense and allows for a dynamic view of the airway in the child with stridor. The primary disadvantage of awake flexible laryngoscopy is that under many circumstances the infant will be crying during the examination, which can alter the appearance of the supraglottic structures. Nevertheless, flexible laryngoscopy has been found to be a consistently accurate method of diagnosis and is the most commonly performed technique. It is also an important means by which secondary or alternative laryngeal lesions, such as bilateral vocal fold immobility, can be diagnosed. Of note, an omega-shaped epiglottis is often associated with LM but can also be found in otherwise normal infants with no airway obstruction. Airway fluoroscopy has been proposed as a screening tool for the infant with stridor; however, although it has been found to have a relatively high specificity, it has a low sensitivity and is thus not recommended if flexible laryngoscopy is available. ^,

It is possible for infants with LM to have a second synchronous lesion that may contribute to airway difficulties. The reported incidence of secondary lesions varies from 8% to 58%, with a higher incidence in children with more severe LM. Definitions of secondary airway lesions vary between studies. The decision to perform a bronchoscopy in patients who present with typical LM is controversial. Some contend that bronchoscopy should be done only in select infants with LM who present with “apnea, failure to thrive, or features inconsistent with isolated LM.” ^, Others have recommended a complete evaluation of the tracheobronchial tree in all symptomatic infants.

In several series, a high prevalence of gastroesophageal reflux disease (GERD) has been reported in patients with LM. ^{, ,} Theoretically, when GERD is present, it can cause airway edema and thus contribute to airway compromise. A systematic review of 27 studies representing 1295 neonates with LM showed that the prevalence of reflux was 59% in this group; however, reflux was not demonstrated to be more prevalent in infants with LM compared with matched children with other respiratory diagnoses. In this systematic review, an increased prevalence of reflux was seen in infants with severe LM compared with those with mild LM. The review points out that there currently are no controlled studies to correlate pH data to pathologic reflux findings in infants, and further trials of antireflux medication versus placebo are justified. Because no definitive evidence is currently available to suggest that mild LM will be improved with antireflux therapy, some have recommended that the routine use of acid-suppressing medications be avoided. However, in children with moderate to severe LM, it is common practice among pediatric otolaryngologists to consider antireflux therapy, often empirically, particularly when surgical intervention is being contemplated. ^, Treatment of GERD may improve LM by preventing acid-induced irritation of the larynx and improving laryngeal sensation and airway protection mechanisms. However, some evidence suggests that infants treated with acid-suppression therapy may have an increased incidence of lower respiratory tract infections. In the child with GERD related to airway obstruction, the GERD will often improve significantly after aryepiglottoplasty.

Laryngeal penetration and aspiration are also common in the child with severe LM. Functional endoscopic evaluation of swallowing (FEES) in children with severe LM has shown laryngeal penetration in 88% of infants and aspiration beyond the vocal folds in 72%. Videofluoroscopic swallow studies are helpful preoperatively to assess the extent of aspiration but are not routinely required for patients without other comorbidities. If a swallow study is obtained, attention should be paid to the degree of global swallow dysfunction and dyscoordination in contrast to focal patterns of penetration and aspiration. These results will provide insight into the potential sources of the patient’s aspiration risk and may help set expectations when counseling parents preoperatively. PSG is not routinely ordered but may be indicated in the child with LM to assess the degree of sleep disturbance. In particular, PSG may be helpful when the patient has multiple comorbidities, if there is increased risk of anesthesia, or when either the parent or the surgeon is undecided regarding the need for operative intervention.

Various anatomic abnormalities that lead to supraglottic obstruction may cause LM in infants. The most common findings are anterior prolapse of the mucosa overlying the arytenoid cartilages (57%), short aryepiglottic folds that tether the epiglottis posteriorly (15%), posterior collapse of the epiglottis (12%), or some combination of these findings (15%). Several classification systems have been proposed, with none being predominant at this time. ^, Regardless of the classification scheme, each provider should have a consistent way to assess and track the laryngeal abnormality and to consider the endoscopic findings in the context of the patient’s presentation and medical history.

Infrequently, the LM is severe and results in feeding difficulties, microaspiration, failure to thrive, apnea, pectus excavatum, and/or cyanosis. In these cases, surgical intervention is recommended to prevent worsening failure to thrive, cor pulmonale, and cardiac failure. ^{, ,} Approximately 10% to 31% of infants seen by a pediatric otolaryngologist require surgical intervention for their LM. The current standard treatment is supraglottoplasty (aryepiglottoplasty; Fig. 27.3 ). The surgical resection can be performed using the carbon dioxide (CO ₂ ) laser, laryngeal microscissors, sinus instruments, or microdebrider. ^{, ,} Supraglottoplasty is commonly performed with the patient ventilating spontaneously. Postoperative intubation can be avoided under most circumstances.

The simplest type of supraglottoplasty involves division of short aryepiglottic folds, often using a laser or laryngeal scissors. Alternatively, various portions of the prolapsing supraglottis are removed: the tissue overlying the arytenoids, the aryepiglottic folds, or the posterior portion of the epiglottis. It is important to preserve the interarytenoid mucosa to avoid postoperative stenosis. For the child with a severely omega-shaped epiglottis, a unilateral incision is occasionally placed in the epiglottis to relax tension and unfurl epiglottic margins. Bilateral epiglottic incision is contraindicated because of the risk of supraglottic stenosis. Likewise, an epiglottopexy can be performed to both unfurl the epiglottis and advance the epiglottic petiole to the tongue base. ^, In this procedure, the mucosa of the lingual surface of the epiglottis and the corresponding mucosa of the base of the tongue are removed with the CO ₂ laser or cautery, followed by suturing of the epiglottis to the tongue base. Unilateral supraglottoplasty has been advocated by some to reduce the risk of postoperative supraglottic stenosis or aspiration; however, most surgeons perform a bilateral procedure to obtain the maximum benefit. ^,

The supraglottoplasty procedures are well tolerated by infants and typically require only a short hospital stay of 1 to 3 days. ^, The success rates of the various forms of supraglottoplasty-epiglottopexy are high, and the vast majority of children obtain relief from their obstruction. ^{, , ,} Children with severe LM often have a lower-percentile weight on a standardized growth curve, and improvement in growth curve percentile is substantial after supraglottoplasty. After supraglottoplasty, the incidence of aspiration also improves significantly, particularly when other comorbidities are not present. Some children have ongoing aspiration for months after surgery and require thickening of feedings or gastrostomy tube placement. Avoidance of nasogastric tube placement after supraglottoplasty is optimal so as to reduce subsequent inflammation and recurrent stridor or obstruction. Sleep mechanics also improve, as evidenced in studies that have compared preoperative and postoperative polysomnogram (PSG). ^,

Those children who do not improve with supraglottoplasty often have underlying neurologic or syndromal abnormalities. Under rare circumstances, some may require a tracheotomy. It is therefore important to counsel parents of patients with multiple comorbidities or atypical presentations of LM that a supraglottoplasty alone may not solve the patient’s airway problems. Complications are rare, the most concerning of which is supraglottic stenosis, which may occur in as many as 4% of cases. Children who do not improve significantly with the initial surgery may require revision supraglottoplasty, which is more commonly needed in children with comorbidities. ^,

Although LM is typically thought of as occurring only in infants, it is occasionally observed in older children and adults and can be a cause of obstructive sleep apnea. ^, Similar to neonates with LM, older children with sleep apnea and LM improve after supraglottoplasty. Neurologically impaired children (i.e., those with cerebral palsy) with poor pharyngeal tone are particularly prone to developing LM. Exercise-induced LM results when enough inspiratory force occurs during exercise to draw the aryepiglottic folds into the larynx and partially obstruct the glottis. ^, In severe cases with redundant aryepiglottic folds, supraglottoplasty can be beneficial. Similarly, if the epiglottis is elongated and flaccid, a partial epiglottidectomy may be effective. It is important to appreciate all airway lesions prior to treatment of LM. Likewise, management of distal airway stenosis may paradoxically cause a greater degree of inspiratory stridor because of increased airflow. If the symptoms are seen only with exercise or are elusive on awake endoscopy in the older patient, exercise laryngoscopy may prove beneficial. ^,

Vocal Fold Dysfunction