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It is important to recognize the differences between the pediatric
and adult upper airway to fully understand why even a relatively
minor obstruction can cause significant airway compromise in children
(Fig. 510-1). The pediatric airway is shorter
and narrower and the larynx is placed more anterior than in adults.1 The
narrowest portion of the pediatric airway is the subglottis, which
is below the vocal cords. Therefore, mild edema in this region can
result in a large reduction in the cross-sectional area of the airway.
The resistance is inversely proportional to the fourth power of
the radius of the airway (see Chapter 503).
Therefore, even a small decrease in airway diameter leads to a much larger
increase in resistance. Young children, and infants especially,
have a large tongue in relation to the small oropharynx.1 They
also have a larger epiglottis.1 Signs of partial
inspiratory obstruction include stridor (a high-pitched sound heard
on inhalation), hoarseness, and increased work of breathing (suprasternal and
intercostal retractions).2 Stridor can be inspiratory
or expiratory, depending on whether the obstruction is supraglottic
or subglottic respectively. If the obstruction is severe or near-complete, worsening
agitation, cyanosis, and respiratory failure will likely occur.
Although acute stridor is usually infectious in etiology, other disorders
may be present, especially when symptoms are severe or persistent.
This chapter discusses inspiratory airway obstruction of infectious
or noninfectious origin.
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Noninfectious Causes
of Upper Airway Obstruction
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Disorders of the upper airway are also discussed in Chapter 371.
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Laryngomalacia is the most common cause of noninfectious,
persistent stridor in infants. It is characterized by a long, curved
epiglottis that folds into an omega shape, with varying degrees
of prolapse of the arytenoids during inspiration.3The
flaccid supraglottic structures prolapse into the airway, leading to
obstruction while breathing in. The inspiratory noise can begin
in the first 2 months after birth, and it commonly presents as stridor
that worsens with crying and activity; improvement occurs when the
infant is placed in the prone position. Diagnosis is usually based
on the history and physical examination; however, airway endoscopy
is also helpful. The condition usually resolves spontaneously by
12 to 24 months. In more severe cases, surgery (supraglottoplasty)
may be necessary.4 Gastroesophageal reflux disease (GERD),
has been linked to laryngomalacia, and the possibility of concurrent
reflux should be considered and treated.5 GERD
can worsen the symptoms of laryngomalacia by contributing to further
inflammation and edema of the larynx.
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Laryngeal cysts, webs, laryngoceles, and saccular
cysts are much less common conditions that can cause airway
obstruction.4 Depending on the degree of obstruction,
they can present soon after birth. Laryngeal ...