Acute Stridor & Croup
Stridor is a clinical sign of partial upper‑airway obstruction: a harsh, vibratory noise produced by turbulent airflow through a narrowed airway. Croup (laryngotracheobronchitis) is a common paediatric syndrome of upper‑airway inflammation that typically presents with a barking cough, hoarseness and inspiratory stridor.
Recognise stridor early, prioritise airway assessment, and avoid actions that increase agitation-children can decompensate rapidly because small reductions in airway diameter cause large rises in resistance (Poiseuille’s law). Follow local paediatric airway and escalation pathways (Resuscitation Council UK; RCEM).
Key pathophysiology and paediatric considerations
- In croup, inflammatory oedema and secretions in the larynx and subglottic area reduce airway radius, producing an exponential rise in airway resistance and work of breathing.
- Young children are particularly vulnerable because of a narrow subglottic region, compliant chest wall, immature accessory muscles, low functional residual capacity and high metabolic demand. They therefore compensate for a short time and then may deteriorate precipitously.
- Clinical implication: maintain calm, allow the child to stay with caregivers in a comfortable position, minimise distress, and escalate early for severe disease.
Epidemiology and aetiology
- Peak incidence: toddlers (12-24 months); affects approximately 2% of children aged 6-36 months.
- Male predominance ~3:2.
- Seasonal peaks in spring and autumn, though cases occur year‑round.
- Most cases are viral (~80%): parainfluenza (classically type 1), RSV, adenovirus, influenza, rhinovirus and enteroviruses.