Stridor

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