II. Definitions
- Stridor
- Audible, high pitched sound during respiration
- Results from partial obstruction of the upper airway (Larynx, trachea) with luminal narrowing
III. Epidemiology
- Most common in younger children
- Airway diameter reduction of 25% results in a cross-sectional airway reduction of 50% (see above)
IV. 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
V. Precautions
- See Awake Nasotracheal Intubation
- Maintain airway and consider differential diagnosis
- Stridor becomes more quiet as airway narrowing becomes severe
- Ready all airway management equipment (RSI, intubation, failed airway)
- 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
VI. History: Pediatric
- Past Medical History
- Prenatal and birth history (e.g. prematurity)
- Immunization history (e.g. DTaP, HIB, Prevnar)
- Genetic disorders
- Down Syndrome (supraglottic stenosis)
- VATER Syndrome or VACERTL Syndrome (Tracheomalacia, tracheoesophageal fistula)
- Pallister-Hall Syndrome (laryngeal cleft)
- CHARGE Syndrome (Cranial Nerve palsy)
- Medical history
- Surgical history
- Prior intubations
- History of Present Illness
- Stridor and associated respiratory symptom history (e.g. onset, frequency, progression, recurrence)
- Recent illness (e.g. Upper Respiratory Infection, fever, cough or congestion)
- Contagious contacts
- Possible foreign body exposures
VII. Exam
- Precautions
- Avoid agitating patient (best respiratory effort is when patient is calm)
- Involve parent with calming measures (e.g. exam in parent's lap)
- Monitoring
- Full Vital Signs including Respiratory Rate, Temperature
- Pulse Oximetry
- End-Tidal CO2 (if hypercapnea suspected)
- Stridor
- Timing during inspiration, expiration or both (Biphasic Stridor)
- Respiratory Distress
- Cardiopulmonary decompensation
- Head and Neck
- Micrognathia
- Cutaneous Hemangiomas
- Neck Masses including lymphatic malformations
VIII. Imaging
- Soft Tissue Neck XRay (including lateral neck) Findings
- Steeple sign (croup)
- Thumbprint (Epiglottitis)
- Wide retropharyngeal space (retropharyngeal space)
-
Chest XRay Findings
- Radiopaque Foreign Body
- Subglottic cyst
- Tracheal stenosis
- CT Neck or Chest
- Avoid in Unstable Patients (ensure stable airway)
- Avoid in young patients (see CT-associated Radiation Exposure)
- Evaluate for masses, abscess, foreign bodies
- MRI (stable patients)
- Vascular abnormalities
IX. 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
X. Causes: Congenital
- Choanal Atresia
- Maxillofacial dysplasia
- Vascular anomalies (e.g. Vascular Ring)
- Laryngeal or tracheal abnormalities
- Laryngomalacia
- Tracheomalacia
- Bronchomalacia
- Subglottic Stenosis (esp. post-intubation)
XI. Causes: Inflammatory or Infectious
- See Pediatric Airway Obstruction Causes
- Laryngotracheal Bronchitis (Croup)
- Epiglottitis
- Bacterial Tracheitis
- Tonsillitis
- Diphtheria
- Oropharyngeal deep space infection
XII. Causes: Neoplasm
- Airway Papilloma
- Airway Hemangioma (subglottic Hemangioma)
XIII. Causes: Neurogenic
- Vocal Cord Paralysis
- Vocal Cord Dysfunction
- Aspiration
XIV. Causes: Trauma
XV. Causes: Allergy
- Spasmodic Croup
- Angioneurotic edema
XVI. Management
- Do not distress a patient with Stridor (risk of worsening obstruction, see precautions above)
- Avoid painful procedures, until immediate Advanced Airway management is available if needed
- Emergent management
- See Rapid Cardiopulmonary Asessment in Children
- See ABC Management
- See Emergency Airway Management
- See Advanced Airway
- See Respiratory Distress in the Newborn
- See Newborn Resuscitation
- Consult otolaryngology or Anesthesia emergently as needed
-
Advanced Airway
- Indications
- Severe Stridor (esp. quiet Stridor, rapid onset)
- Persistent refractory respiratory distress or Hypoxia
- Precautions
- Use an Endotracheal Tube that is 1-2 sizes smaller than estimated for size
- Most experienced in Advanced Airway should perform procedure
- Ideally perform in controlled environment (e.g. OR) by otolaryngology or anesthesiology
- Indications
- Evaluate and treat specific conditions
- See Croup
- See Laryngeal Foreign Body
- See Angioedema
- Awake Fiberoptic Nasolaryngoscopy
- May identify Stridor source
XVII. References
- Dahan, Campbell and Melville (2020) Crit Dec Emerg Med 34(11): 3-10
- Mehta and Eliason (2024) Crit Dec Emerg Med 38(6): 27-35