DESCRIPTION

• Stridor is characterized by noisy breathing with a harsh and high-pitched quality that can be appreciated without a stethoscope. It may be a sign of acute or chronic upper airway obstruction.
• Stridor is most often present during inspiration but may occur during expiration or during both phases of breathing depending on the level in the airways at which the obstruction is present.

EPIDEMIOLOGY

• General incidence in the pediatric population is unknown and is dependent on the underlying cause.
• Infants and young children are more commonly affected due to smaller caliber of upper airways.
• Viral croup is the most common cause of acute stridor in children between 6 months and 3 years of age.
• Laryngomalacia is the most common cause of chronic stridor in young infants.
• Paradoxical vocal cord movement and edema of the airways may be causes of stridor in older children.

ETIOLOGY

• Inspiratory stridor—most commonly seen with extra thoracic obstruction
  • Nose, pharynx, craniofacial
    • Choanal atresia or stenosis
    • Micrognathia
    • Macroglossia
    • Vallecular cyst
    • Retropharyngeal or peritonsillar abscess
    • Lingual thyroid
    • Thyroglossal cyst
  • Supraglottic
    • Epiglottitis
    • Angioedema
  • Glottic
    • Foreign body
    • Laryngomalacia
    • Laryngospasm
    • Vocal cord paresis or paralysis
    • Paradoxical vocal cord movement (also known as vocal cord dysfunction or inducible laryngeal obstruction)
    • Papilloma from human papillomavirus
    • Angioedema
    • Laryngeal edema from reflux
    • Cystic hygroma
    • Hypocalcemic tetany
  • Subglottic
    • Infectious croup
    • Spasmodic croup
    • Subglottic stenosis (acquired and congenital)
    • Subglottic angioedema from anaphylaxis
    • Subglottic edema from reflux
    • Trauma
  • Trachea
    • Bacterial tracheitis
    • Tracheoesophageal fistula (TEF)
• Expiratory stridor—commonly seen with intrathoracic obstruction
  • Trachea and bronchi
    • Tracheobronchial obstruction
      • Intraluminal such as tracheobronchomalacia
      • Extraluminal due to cardiac, vascular, or mass compression
• Biphasic stridor—commonly seen with fixed obstruction
  • Glottic
    • Laryngeal web or cyst
  • Subglottic
    • Subglottic cyst (may be secondary to intubation)
    • Subglottic hemangioma
  • Trachea
    • Complete tracheal rings
    • Vascular rings and slings

RISK FACTORS

• Congenital
  • Nasal and craniofacial deformities
  • Pharyngeal anomalies
  • Laryngeal anomalies
  • Subglottic narrowing
  • Tracheal narrowing
  • Vascular anomalies
  • Congenital pulmonary malformations
  • Neuropathic or musculoskeletal weakness
• Acquired
  • History of intubation
  • History of trauma or burn injury
  • Foreign body aspiration
  • Infectious etiology
  • Allergic or associated with anaphylaxis
  • Gastroesophageal reflux disease (GERD)
  • Stress- or exercise-induced

GENERAL PREVENTION

Vaccination with the Haemophilus influenzae type B (HiB) vaccine has reduced the incidence of epiglottitis that can present with stridor in young children.

PATHOPHYSIOLOGY

• Upper airway narrowing may be due to inflammation, edema, or extrinsic or intrinsic narrowing.
• Airflow through a narrowed upper airway causes a significant increase in airflow resistance, decreased airflow velocity, and subsequent decrease in airflow pressure distal to the point of airway obstruction.
• Decreased pressure along the walls of the airways causes turbulent airflow along with increased tendency of airway collapse, which results in the sound of stridor.

COMMONLY ASSOCIATED CONDITIONS

• Prematurity
• Reflux
• Atopy
• Craniofacial anomalies
• Down syndrome
• Hypothyroidism
• Anxiety