Bronchiolitis (paediatric & neonatal emergency medicine)
Overview
Bronchiolitis is an acute viral lower‑respiratory infection of infants (classically <2 years, peak 3-6 months) causing small‑airway inflammation, oedema and mucus with variable airway obstruction. Most cases are self‑limiting, but young infants and those with comorbidity may develop significant respiratory distress or failure.
Manage in the ED by rapid risk‑stratification, supportive care and early escalation of respiratory support when required (NICE NG9).
Epidemiology and aetiology
- Most common cause: respiratory syncytial virus (RSV) - ≈60-80% of cases.
- Other viruses: rhinovirus, influenza, parainfluenza and metapneumovirus.
- Seasonal peak: autumn-winter in temperate climates.
- High‑risk groups for severe disease: prematurity (<37 weeks), neonates (particularly <6 weeks), congenital heart disease, chronic lung disease (e.g., BPD), immunocompromise, neuromuscular disorders.
Pathophysiology (concise)
Viral injury to bronchiolar epithelium → epithelial necrosis, mucosal oedema, increased secretions and cellular debris → small‑airway obstruction, air trapping, V/Q mismatch and increased work of breathing. Progression can lead to hypoxaemia, hypercapnia and respiratory fatigue.
Clinical diagnosis
- Diagnosis is clinical. Use the NICE case definition: a coryzal prodrome (1-3 days) followed by persistent cough plus either tachypnoea or chest recession and either wheeze or crackles. Most useful in infants <2 years (NICE NG9).