What is Stridor?
Stridor is a high-pitched respiratory sound caused by turbulent airflow through narrowed or obstructed airways, typically indicating upper airway obstruction. 1, 2
Acoustic Characteristics and Localization
- Inspiratory stridor typically results from supraglottic or glottic obstruction (above or at the vocal cord level). 1
- Expiratory stridor originates from obstruction at or below the glottic level and may indicate more severe upper airway obstruction. 1
- Biphasic stridor (present during both inspiration and expiration) often indicates fixed lesions of the glottis or subglottis, while dynamic lesions usually cause only inspiratory stridor. 3
Clinical Significance
Stridor is a clinical sign, not a diagnosis—the underlying cause must always be identified. 4, 5 It represents abnormal air passage during breathing and is often the most prominent sign of upper airway obstruction. 1
Age-Specific Considerations
In infants, stridor or noisy breathing that usually reflects upper airway obstruction is the most common indication for flexible bronchoscopy. 3
- Laryngomalacia is the most common congenital laryngeal anomaly and the most frequent cause of persistent stridor in children. 3, 6
- Vocal cord paralysis is the third most common congenital laryngeal anomaly producing stridor in infants and children, usually resulting from congenital central nervous system anomalies. 3, 6
- Up to 68% of infants with stridor have concomitant abnormalities below the epiglottis, making complete airway evaluation essential. 3, 7
In older children, stridor is rare but always warrants airway endoscopy if not due to recent endotracheal intubation. 3
Post-Intubation Context
In mechanically ventilated patients, postextubation stridor indicates upper airway obstruction, typically from laryngeal edema, and is a predictor of extubation failure. 3
- Postextubation stridor is a significant marker for moderate to severe subglottic stenosis or laryngeal injury. 3
- A failed cuff leak test is an insensitive but specific predictor of upper airway obstruction (postextubation stridor or laryngeal edema), with pooled sensitivity of 0.56 and specificity of 0.92. 3
When to Investigate Further
Airway endoscopy should be performed in any child with severe or persistent stridor, stridor associated with hoarseness, or stridor leading to oxygen desaturation or apnea. 3, 7