Pediatric emergency medicine trisk 347

obstruction, upper airway anomalies (particularly laryngotracheomalacia), and
congenital or postintubation subglottic stenosis. Common causes for upper airway
obstruction in infants and children include adenotonsillar hypertrophy, croup,
foreign body, retropharyngeal abscess, and tracheitis. Airway edema can be
secondary to trauma, thermal or chemical burn, or anaphylaxis. Epiglottitis or
supraglotittis, although less common, can be one of the most life-threatening
causes of respiratory distress and is a true emergency. The incidence of
epiglottitis has declined significantly since routine immunization against
Haemophilus influenzae type b , the pathogen that once caused at least 75% of
cases. Streptococcus pneumoniae , group A streptococcus, Staphylococcus aureus
, and nontypeable and other strains of Haemophilus influenza now account for
most cases of bacterial epiglottitis. Epiglottitis should be suspected in children
who have abrupt onset of fever, sore throat, dysphagia, drooling, muffled voice,
labored respirations, and/or stridor. Young children appear toxic and anxious and
assume a sniffing position with protruding jaw and extended neck. These children
are at risk of abrupt onset of respiratory arrest from obstruction. Older children
and adolescents may present with just severe sore throat, often with a less rapid
progression, without oropharyngeal abnormalities. Peritonsillar and
retropharyngeal abscess may present with symptoms similar to epiglottitis but are
less likely to have stridor and the onset is more gradual. Croup or
laryngotracheobronchitis is the most common cause of upper airway obstruction
in children 6 months to 3 years of age. Croup causes subglottic narrowing and is
characterized by a barky cough, inspiratory stridor, and hoarseness that are worse
at night. Viral croup is most often caused by parainfluenza virus, frequently with
preceding upper respiratory infection symptoms, which may or may not be
accompanied by fever. Respiratory distress often occurs with wakening during the
night in a child who was relatively well before going to sleep. Children with
croup-like symptoms that are recurrent or prolonged may have an underlying
fixed or functional airway abnormality, most commonly subglottic stenosis or
hemangioma. Children with chronic stridor, particularly those younger than 2
years, may also have an underlying congenital anomaly. Tracheitis, an infection

of the trachea, may occur as a primary infection with abrupt onset, high fever
similar to epiglottitis. More commonly, it presents as a secondary infection in a
child with an initial croup-like illness but with a worsening clinical course.
Although tracheitis is usually due to bacteria, most commonly streptococcus or
staphylococcus, cases in which only viruses or no pathogen is identified are not
uncommon. Foreign-body aspiration, which has a peak age of occurrence of 1 to
5 years, may cause obstruction of the upper or lower airway and is a leading


cause of accidental death in toddlers. A history of abrupt onset of choking or
gagging is suggestive. Drooling, dysphagia, and stridor suggest an upper airway
foreign body, whereas unilateral wheeze, particularly first-time wheeze with acute
onset, suggests lower airway position. Presentation, particularly with lower
airway foreign body, may be delayed by days to weeks from time of aspiration.
TABLE 71.1
Criteria for Respiratory Failure a
Clinical

Laboratory

Tachypnea, bradypnea, PaO2 <60 mm Hg in 60% O2 b
apnea, irregular
respirations
Pulsus paradoxus >30 Paco2 >60 mm Hg and rising
mm Hg
Decreased or absent
pH <7.3
breath sounds
Stridor, wheeze,
grunting

Severe retractions and
use of accessory
muscles
Cyanosis in 40% O2 b
Depressed or
heightened level of
consciousness,
decreased response
to pain
Weak to absent cough
or gag reflex
Poor muscle tone
a Respiratory
b Excluding

failure is likely if two clinical findings and one laboratory finding exist.
cyanotic heart disease.


TABLE 71.2
ANATOMIC/PHYSIOLOGIC DIFFERENCES IN INFANT/CHILD AND
ADULT AIRWAYS


Difference

Consequence

Nose: infants <4 mo
preferential nose breathers

Larynx: higher (C2–C3 vs.
C6), softer, more elastic

Nasal congestion may result in significant
respiratory distress
More difficult to intubate

Collapses more easily, particularly with fixed
obstruction (i.e., Bernoulli principle—as the
velocity of flow through a collapsible tube
increases, the pressure that holds the tube
open decreases)
Trachea: one-third diameter of Poiseuille law—resistance varies inversely
adult at birth, shorter
with fourth power of the radius; 1-mm
thickening decreases cross-sectional
diameter by 20% in adult and by 80% in
child
More difficult to intubate/maintain proper
depth
Alveoli: elastic fibers less well Alveoli collapse more easily, results in
developed
ventilation–perfusion mismatch
Lungs: lower functional
Reserve small, therefore limited protection
residual capacity
when ventilation is interrupted, PaO2
decreases more rapidly
Respiratory control apparatus: Apnea or inability to respond appropriately to
immature—reflexes that

mechanical respiratory obstruction or
inhibit respiration are very
increased metabolic demand
strong; central nervous
system processing of
information markedly
affected by sleep state, cold,
drugs, other metabolic
derangements
Chest wall: more compliant;
Accessory muscle retractions
intercostal muscles
Diaphragm does more work but is less
immature; ribs more
effective
horizontal; diaphragm