Stridor

Stridor
1. Audible, high pitched sound during respiration
2. Results from partial obstruction of the upper airway (Larynx, trachea) with luminal narrowing

Most common in younger children
1. Airway diameter reduction of 25% results in a cross-sectional airway reduction of 50% (see above)

Turbulent air flow in a partially obstructed upper airway results in a high pitched sound
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)
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
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

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)
1. Avoid unnecessary procedures (e.g. delay Intravenous Access until stable)
2. Position child as they are most comfortable

Past Medical History
1. Prenatal and birth history (e.g. prematurity)
2. Immunization history (e.g. DTaP, HIB, Prevnar)
3. Genetic disorders
  1. Down Syndrome (supraglottic stenosis)
  2. VATER Syndrome or VACERTL Syndrome (Tracheomalacia, tracheoesophageal fistula)
  3. Pallister-Hall Syndrome (laryngeal cleft)
  4. CHARGE Syndrome (Cranial Nerve palsy)
4. Medical history
5. Surgical history
6. Prior intubations
History of Present Illness
1. Stridor and associated respiratory symptom history (e.g. onset, frequency, progression, recurrence)
2. Recent illness (e.g. Upper Respiratory Infection, fever, cough or congestion)
3. Contagious contacts
4. Possible foreign body exposures

Precautions
1. Avoid agitating patient (best respiratory effort is when patient is calm)
2. Involve parent with calming measures (e.g. exam in parent's lap)
Monitoring
1. Full Vital Signs including Respiratory Rate, Temperature
2. Pulse Oximetry
3. End-Tidal CO2 (if hypercapnea suspected)
Stridor
1. Timing during inspiration, expiration or both (Biphasic Stridor)
Respiratory Distress
1. Nasal flaring
2. Intercostal retractions
3. Accessory Muscle use
4. Tachypnea
5. Grunting
6. Tripod positioning
Cardiopulmonary decompensation
Head and Neck
1. Micrognathia
2. Cutaneous Hemangiomas
3. Neck Masses including lymphatic malformations

Soft Tissue Neck XRay (including lateral neck) Findings
1. Steeple sign (croup)
2. Thumbprint (Epiglottitis)
3. Wide retropharyngeal space (retropharyngeal space)
Chest XRay Findings
1. Radiopaque Foreign Body
2. Subglottic cyst
3. Tracheal stenosis
CT Neck or Chest
1. Avoid in Unstable Patients (ensure stable airway)
2. Avoid in young patients (see CT-associated Radiation Exposure)
3. Evaluate for masses, abscess, foreign bodies
MRI (stable patients)
1. Vascular abnormalities

Do not distress a patient with Stridor (risk of worsening obstruction, see precautions above)
1. Avoid painful procedures, until immediate Advanced Airway management is available if needed
Emergent management
1. See Rapid Cardiopulmonary Asessment in Children
2. See ABC Management
3. See Emergency Airway Management
4. See Advanced Airway
5. See Respiratory Distress in the Newborn
6. See Newborn Resuscitation
7. Consult otolaryngology or Anesthesia emergently as needed
Advanced Airway
1. Indications
  1. Severe Stridor (esp. quiet Stridor, rapid onset)
  2. Persistent refractory respiratory distress or Hypoxia
2. Precautions
  1. Use an Endotracheal Tube that is 1-2 sizes smaller than estimated for size
  2. Most experienced in Advanced Airway should perform procedure
    1. Ideally perform in controlled environment (e.g. OR) by otolaryngology or anesthesiology
Evaluate and treat specific conditions
1. See Croup
2. See Laryngeal Foreign Body
3. See Angioedema
Awake Fiberoptic Nasolaryngoscopy
1. May identify Stridor source