Chronic Pediatric Airway Diseases

1

List the three most common congenital disorders of the larynx.

In order of most to least common: laryngomalacia, vocal cord paralysis, and subglottic stenosis.

2

What is stridor?

Stridor is an audible breath sound due to turbulent airflow from airway narrowing.

3

What is the most common cause of stridor in the neonate and infant?

Laryngomalacia.

4

Describe the characteristics of laryngomalacia.

There are several theories regarding the etiology of laryngomalacia, including short aryepiglottic folds (folds of tissue between epiglottis and arytenoid cartilages), poor neuromuscular control of the supraglottis, and inflammatory insults to the larynx. Inspiratory stridor occurs with collapse of supraglottic tissue on inspiration. Affected infants typically present with intermittent inspiratory stridor within the first 2 weeks of life. Stridor is usually worse with feeding, while supine, or while agitated. The child may need to take breaks while feeding to breathe. Most cases are self-limited, with resolution of symptoms by age 18 months. However, approximately 10% of patients experience significant upper airway obstruction resulting in feeding difficulties, failure to thrive, pectus excavatum, apneic episodes, cyanosis, and hypoxia. These patients warrant consideration for surgical intervention.

Patients may have associated gastroesophageal reflux disease. This condition may contribute to airway edema, further compromising the airway. Acid suppression may improve mild cases of laryngomalacia and is often instituted empirically, though there are growing concerns about the long-term use of these medications.

Diagnosis is made with awake flexible fiber-optic laryngoscopy.

5

What is the typical size of the pediatric airway?

Airway size is determined based on the narrowest portion of the airway. In the pediatric population, this is the subglottis at the level of the cricoid cartilage. In a term infant, the subglottic lumen measures 4.5 to 5.5 millimeters.

6

How is an endotracheal tube size chosen?

Endotracheal and tracheostomy tube sizes are based on the inner diameter of the tube. For example, a 4.0 endotracheal or tracheostomy tube correlates to an inner diameter of 4 millimeters. The smallest tube that provides adequate ventilation should be chosen. Several size-predictive formulas exist and are based on parameters such as age, height, weight, and/or finger width. One commonly used formula is based on the age of the patient: inner diameter = 4 + age/4. This formula is more accurate for older children.

7

Describe the characteristics of subglottic stenosis.

Subglottic stenosis (SGS) is narrowing of the subglottis and can be either congenital or acquired. Congenital SGS occurs in the absence of a history of endotracheal intubation or other causes of acquired stenosis. Causes of congenital SGS include an elliptical cricoid, congenital narrowing (as in Down syndrome), and trapped first tracheal ring.

Acquired stenosis is more common than congenital SGS and endotracheal intubation is the most common cause. Duration of intubation and endotracheal tube size are the two most important factors in the development of stenosis. Stenosis occurs as a result of pressure necrosis and subsequent scar formation. Prevention of subglottic stenosis via selection of the proper endotracheal tube, a short duration of intubation, and appropriate cuff pressure is ideal. Other causes include neck trauma, laryngeal procedures, caustic ingestions, radiotherapy, and tracheal infection. Diagnosis is made at the time of direct laryngoscopy and bronchoscopy.

8

Describe the most commonly used grading system for subglottic stenosis.

The Myer-Cotton classification system is the most widely used system for grading the degree and severity of subglottic stenosis ( Fig. 50.1 ).

9

How is subglottic stenosis treated?

Surgical methods of managing subglottic stenosis include endoscopic and open transcervical techniques. Choice of method depends on many patient factors, including degree of stenosis, comorbid conditions, and age of the lesion. Thin web-like lesions that are identified early, when the scar is immature, may be amenable to endoscopic procedures including scar lysis by balloon dilation. More mature, thicker lesions with greater superior-inferior dimension may require augmentation or resection procedures. Augmentation procedures involve placing cartilage grafts into the airway to make the lumen bigger. Resection procedures involve removing the affected segment and anastomosing the airway.

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