1. Description of the problem

Basic concepts and physiology

1. Poiseuille’s Law

2. Pediatric airway: Given that a decrease in radius size increases resistance significantly, children who have small airways to begin with are at risk of having a significant increase in airway resistance from even a small amount of swelling.

3. Upper airway narrowing produces changes in either inspiratory or expiratory flow depending on the location of the obstruction in the respiratory system. Extrathoracic lesions (those above the glottis) lead to inspiratory stridor; Intrathoracic lesions (below the level of the glottis) lead to expiratory stridor.

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Stridor is the key distinctive respiratory finding. Additional findings consistent with respiratory distress may be evident as well—cyanosis, tachypnea, use of accessory muscles. The more agitated the patient the worse the symptoms, signs, and gas exchange.

Key management points
  • Keep the child calm.

  • Depending on the suspected etiology, give oral steroids as early as possible.

  • Clinically evaluate airway function:

  • Plain film of neck: Help identify static tracheal or bronchial lesions

  • Fluoroscopy: Identify dynamic longitudinal airway events. Best appreciated in this axis.

  • Computerized tomography: Best to identify dynamic cross-sectional airway events

  • Virtual bronchoscopy: Best to identify gross observation of trachea and bronchus

Specific conditions and hallmark management points


Epiglottitis:This is an airway emergency given rapid progression of disease and risk for total airway occlusion. Keep child calm. Generally the condition appears toxic. Consult otolaryngology and anesthesiology departments. Patient should be intubated in operating room as soon as possible to secure airway. Initiate steroids and antibiotics.

Croup: Keep child calm. Use oral steroids and racemic epinephrine nebulized. Children with persistent stridor at rest should be admitted to the hospital. If patient distressed, start heliox with high-flow nasal cannula and consider intubation

Bacterial tracheitis: generally toxic appearance at presentation

– Intubate early

– Likely have pneumonia along with tracheitis (50%)

– Anticipate need to suction copious amounts of thick tracheal secretions

– Racemic epinephrine and steroids have no well-established role



– Keep patient calm.

– No Albuterol or racemic epinephrine (relaxing of smooth muscle worsens malacia)

– Consider pronging, particularly if patient has bronchomalacia as well.

– Refer to otolarygology and pulmonary departments for close follow-up.

– High risk for aspiration and gastroesophageal reflux

– Resolves with time (months)

Vascular Ring:

– Keep patient calm.

– Consider heliox.

– Diagnosis by barium swallow, bronchoscopy, or contrast computerized tomography of chest

– Treatment is surgery.

Subglottic stenosis:

– Keep child calm

– Oral Steroids

– Racemic epinephrine nebulized

– Heliox

– Consider intubating.

2. Emergency Management

  • Calm patient, either though help of family or with sedation.

  • Consider steroids and racemic epinephrine.

  • If considering intubation, obtain tube size 1 and two sizes smaller than normal. Consider using lubrication on sides of endotracheal tube to facilitate passing through subglottic area. If available, consult otolaryngology department for support.

3. Diagnosis

Establishing the diagnosis

Classification of stridor will help identify location of lesion along with detailed history.

Classic patient with croup (primary acquired cause of stridor) wakes up in the middle of the night with severe distress, may or may not improve en route to the hospital, and has viral prodrome.

Children with subglottic stenosis likely have a history of prolonged intubation, prematurity, tracheostomy in the past, or traumatic intubation.

Lateral airway films can show a classic “steeple” sign for croup.

Please see Table I for a summary of infectious causes of upper airway obstruction.

Table I.
Croup Bacterial Tracheitis Epiglottitis
Age 4mo–3y 6mo–12y 2–8 y (75% 1–5y)
Onset Gradual Intermediate Rapid, <24 h
Fever Low grade High grade None
Cough “Barking” “Barking” None
Drooling No No Severe
Appearance Normal Toxic Toxic
Airway Positioning Non-specific Non-specific “Tripod”
Season Winter Non-specific Non-specific
Differential diagnosis

Do not forget about the possibility of a foreign body. Consult otolaryngology in this case.

Infants with raised intracranial pressure can present with stridor as well, particularly in the setting of non-accidental trauma.

Hypocalcemia and the associated tetany may present as vocal cord spasm/paralysis and stridor.

Oncology patients on vincristine may develop vocal cord paralysis and stridor as an adverse effect of the drug.

Very rarely atypical Wegener’s syndrome can present with subglottic stenosis and stridor.

4. Specific Treatment

Please see Management Points above for treatment.

Drugs and dosages

Decadron 0.6 mg/kg PO or IM (preferably PO to minimize agitation and worsening stridor)

Racemic epinephrine 0.25 to 0.5 mg nebulized when indicated.

Refractory cases

For particularly refractory cases, intubate and secure airway.

5. Disease monitoring, follow-up and disposition

Depending on underlying etiology, upper airway obstruction may need follow-up with otolaryngology or pulmonology.


As the radius of the airway narrows in one location, the flow of air through that narrowed section becomes more turbulent and loses its laminar characteristics. Normally a column of air has lateral and vertical forces. As air flow increases through a narrowed column, you lose the lateral forces and turbulence results (Venturi effect).

The greater the velocity of air the more turbulent flow becomes; hence calming these patients down helps restore some laminar flow.


Parainfluenza virus accounts for more than two thirds of cases of viral croup, with type 1 and 2 responsible for the majority of cases. Other etiologic agents include influenza virus, respiratory syncytial virus, metapneumovirus, adenovirus, rhinovirus, enterovirus and, rarely, measles virus and herpes simplex virus. When croup is caused by an influenza virus, the clinical picture is usually more severe than that caused by a parainfluenza virus.

Croup accounts for approximately 15% of respiratory tract disease seen in the pediatric age group. The condition is most common between the ages of 6 months and 3 years but can occur in children as young as 3 months and as old as 15 years of age; the peak incidence occurs during the second year of life. The male to female ratio is approximately 3 to 2. Transmission is by droplets and/or direct contact.


Prognosis is dependent on the underlying condition.

What's the evidence?

Malhotra, A, Krilov, LR. “Viral croup”. Pediatr Rev. vol. 22. 2001. pp. 5-12. (Excellent review of this common cause of acquired stridor and decision making surrounding hospitalization and management.)

Peltola, V, Heikkinen, T, Ruuskanen, O. “Clinical courses of croup caused by influenza and parainfluenza virus”. Pediatr Infect Dis J. vol. 21. 2002. pp. 76-78. (Important description of the common causes of croup.)

Ewig, JM. “Croup”. Pediatr Ann. vol. 31. 2002. pp. 125-130. (Nice detailed review of croup.)

McIntosh, KS, McAdams, AJ. “Human metapneumovirus: An important new respiratory virus”. N Engl J Mede. vol. 350. 2004. pp. 431-3. (Introduction to this virus as a cause of stridor and many other upper and lower respiratory tract infections.)

Cherry, JD, Feigin, RD, Cherry, JD, Demmler, GJ, Kaplan, SL. “Croup (laryngitis, laryngotracheitis, spasmodic croup, laryngotracheobronchitis, bacterial tracheitis, and laryngotracheobronchopneumonitis)”. Textbook of pediatric infectious diseases. 2004. pp. 252-65. (Excellent review of all acquired causes of croup and the various signs and symptoms associated with each infectious condition.)