II. Pathophysiology
- Turbulent air flow in a partially obstructed upper airway results in a high pitched sound
- Location of obstruction determines inspiratory or biphasic timing
- Obstruction above the glottis results in Inspiratory Stridor
- Obstruction at or immediately below the glottis results in both inspiratory and expiratory Stridor (Biphasic Stridor)
- A child's small airways are impacted most significantly by even relatively small partial obstructions (Poiseuille's Law)
- Infant: Airway edema of 1 mm reduces a 2 mm radius airway to 1 mm
- Resistance to flow increases by 16 fold (Resistance = 1/r^4)
- Adult: Airway edema of 1 mm reduces a 5 mm radius airway to 4 mm
- Resistance to flow increases by 2-4 fold
- Infant: Airway edema of 1 mm reduces a 2 mm radius airway to 1 mm
- Airway Radius By Age at Cricoid Cartilage
- Age 0 to 1 year: 3 mm
- Age 1 to 2 years: 3.75 mm
- Age 2 to 4 years: 4 mm
- Age 4 to 5 years: 4.5 mm
III. Epidemiology
- Most common in younger children
- Airway diameter reduction of 25% results in a cross-sectional airway reduction of 50% (see above)
IV. Precautions
- See Awake Nasotracheal Intubation
- Maintain airway and consider differential diagnosis
- Ready all airway management equipment (RSI, intubation, failed airway)
V. Causes: By Age
- Age <1 year (infants)
- Laryngomalacia (60%)
- Croup
- Vocal Cord Paralysis
- Subglottic Stenosis
- Airway Hemangioma
- Vascular Rings or slings
- Age 1-3 years (toddlers)
- Age 4-18 years
VI. Causes: Congenital
- Choanal Atresia
- Maxillofacial dysplasia
- Vascular anomalies (e.g. Vascular Ring)
- Laryngeal or tracheal abnormalities
- Laryngomalacia
- Tracheomalacia
- Bronchomalacia
- Subglottic Stenosis
VII. Causes: Inflammatory or Infectious
- Laryngotracheal Bronchitis (Croup)
- Epiglottitis
- Bacterial Tracheitis
- Tonsillitis
- Diphtheria
- Oropharyngeal deep space infection
VIII. Causes: Neoplasm
- Airway Papilloma
- Airway Hemangioma
IX. Causes: Neurogenic
- Vocal Cord Paralysis
- Vocal Cord Dysfunction
- Aspiration
X. Causes: Trauma
XI. Causes: Allergy
- Spasmodic Croup
- Angioneurotic edema
XII. Precautions
- Do not distress a child with suspected partial airway obstruction (e.g. croup)
- Avoid unnecessary procedures (e.g. delay Intravenous Access until stable)
- Position child as they are most comfortable
XIII. Management
- Evaluate and treat specific conditions
- Emergent management
XIV. References
- Dahan, Campbell and Melville (2020) Crit Dec Emerg Med 34(11): 3-10