II. Pathophysiology
- Airway diameter is significantly smaller in children with reduced airflow
- Poiseuille's Law defines airflow resistance as inversely proportional to the fourth power of the radius
- An 8 mm airway diameter in a 2 year old may decrease to 4 mm (50%) with edema from croup
- Airflow resistance in this case will increase 16 fold (2^4)
- Even mild reductions in pediatric airway diameter results in significant airflow restriction
- Turbulent airflow
- Inspiratory Stridor
III. Findings
- Stridor
- Drooling
- Muffled voice
- Tripod position
- Accessory Muscle use
- Altered Mental Status
IV. Precautions
- Maintain close monitoring (progression to Respiratory Failure may be rapid)
- Oxygen Saturation may be reassuring until imminent complete airway obstruction
V. Differential Diagnosis: Child
- Foreign Body Aspiration
-
Anaphylaxis
- Angioedema, Stridor and Wheezing
- Shock onset within minutes to hours
-
Croup
- Barking cough, harsh voice and Stridor developing over days
-
Epiglottitis
- Rapid onset and progression within 24 hours to fever, Pharyngitis, Drooling, muffled voice and no cough
-
Bacterial Tracheitis
- URI symptoms abruptly progressing to high fever, toxic appearance, Stridor and cough
-
Retropharyngeal Abscess or Peritonsillar Abscess
- Fever and Pharyngitis progressing to Drooling and stiff, painful neck
-
Ludwig's Angina
- Dental Infection spread to submaxillary space with secondary fever, Cellulitis, Stridor and Trismus
-
Diphtheria
- Thick, gray, Exudative Pharyngitis with fever, Dysphagia and toxic appearance
VI. Imaging
-
Chest XRay (AP, Lateral)
- Croup
- Steeple sign (secondary to tracheal narrowing and subglottic edema)
- Foreign Body Aspiration
- Upper airway: Foreign body may be visible, pharynx over-inflated
- Lower airway: Air trapping with hyperinflation, Atelectasis
- Croup
- Soft Tissue Neck (Lateral)
- Retropharyngeal Abscess
- Pre-Vertebral soft tissue thickening or air-fluid level
- Epiglottitis
- Thumbprint sign (secondary to Epiglottis swelling)
- Retropharyngeal Abscess
- Advanced imaging
- CT Soft tissue neck with IV contrast (gold standard, but ionizing radiation)
- MRI Neck
- Requires sedation in young children
- Prolonged scan time (higher risk in a patient whose stability may change within 1-2 hours)
- Often unavailable
VII. Management
- See ABC Management
- See Advanced Airway
VIII. References
- Ayoub (2026) Crit Dec Emerg Med 40(10): 4-12
- Fuchs and Yamamoto (2011) APLS, Jones and Bartlett, Burlington, p. 48, 58