Key Facts

Bronchiolitis is the most common cause of hospitalisation in infants in the UK. It is a self-limiting condition, and evidence consistently shows that pharmacological interventions do not alter the disease course. Supportive care is the cornerstone of management.

Epidemiology

Bronchiolitis affects approximately 33% of infants in their first year. About 2-3% require hospitalisation (~30,000 admissions/year in England). Peak incidence: November to March. Mortality is very low (<0.5%) but higher in those with comorbidities (prematurity, CHD, immunodeficiency).

Aetiology

• RSV: 70-80% of cases
• Other: Rhinovirus, human metapneumovirus, parainfluenza, adenovirus, influenza
• Risk factors for severe disease: Prematurity (<32 weeks), congenital heart disease, chronic lung disease, immunodeficiency, neuromuscular disease, age <6 weeks

Pathophysiology

RSV infects bronchiolar epithelial cells, causing necrosis, peribronchiolar inflammation, oedema, and mucus plugging. This leads to small airway obstruction with air trapping and atelectasis. The small calibre of infant bronchioles means even minor inflammation causes significant obstruction. Viral shedding continues for 1-3 weeks. Immune response (RSV-specific IgE, neutrophilic inflammation) contributes to airway obstruction.

Typical Course

• Day 1-3: Coryzal prodrome — rhinorrhoea, sneezing, mild cough, low-grade fever
• Day 3-5: Wheeze, crackles, tachypnoea, increased work of breathing, feeding difficulty
• Peak severity: Day 3-5 of respiratory symptoms
• Recovery: 7-10 days (cough may persist 2-3 weeks)

Examination Findings

• Bilateral wheeze AND crackles (characteristic)
• Tachypnoea, subcostal/intercostal recession
• Nasal flaring, head bobbing (infants)
• Hyperinflated chest

Red Flags

• SpO2 <92% — requires supplemental oxygen
• Apnoeas — especially in <6 weeks or ex-preterm; may need monitoring
• Inability to maintain adequate oral intake (<50-75%) — NG or IV fluids
• Exhaustion, reduced consciousness — escalate to HDU/PICU
• Cyanosis — severe disease

NICE NG9 — Investigations NOT Routinely Recommended

• CXR, blood tests, blood gas — not routine
• NPA for RSV — only for infection control (cohorting in hospital)

Bedside

• SpO2: Key monitoring parameter
• Respiratory assessment: Work of breathing, feeding ability
• Weight: Monitor hydration

Bloods

• Only if diagnostic uncertainty or suspected secondary bacterial infection
• Blood gas: If severe respiratory distress or impending respiratory failure

Imaging

• CXR: Only if diagnostic uncertainty or atypical features (do NOT do routinely — overdiagnoses pneumonia and leads to unnecessary antibiotics)

Non-pharmacological (NICE NG9)

• Oxygen: If SpO2 persistently <92% — nasal prongs or high-flow nasal cannula (HFNC)
• Feeding support: NG feeding if oral intake <50-75% of usual; IV fluids (maintenance rate with 0.9% NaCl + 5% glucose) if NG not tolerated
• Minimal handling: Reduce stimulation; cluster cares
• Nasal suctioning: Only if nasal secretions are causing respiratory distress or feeding difficulty — not routine
• Positioning: Head elevated 30°

Pharmacological

• NONE routinely recommended (NICE NG9):
  • Bronchodilators (salbutamol, ipratropium) — NOT effective
  • Corticosteroids — NOT effective
  • Antibiotics — NOT indicated unless secondary bacterial infection confirmed
  • Nebulised hypertonic saline — NOT recommended routinely
  • Adrenaline — NOT recommended

Escalation

• HFNC (High-Flow Nasal Cannula): Increasingly used for moderate-severe bronchiolitis; provides heated humidified oxygen with low-level CPAP effect
• CPAP/BIPAP: If HFNC insufficient
• Intubation and ventilation: Rare; for respiratory failure or frequent apnoeas

Prevention

• Palivizumab: Monthly IM injection during RSV season for high-risk infants (ex-preterm with CLD, haemodynamically significant CHD)
• Hand hygiene: Key infection control measure
• Nirsevimab: Newer long-acting anti-RSV monoclonal antibody — single dose; increasingly available for broader neonatal population

Referral Criteria

• Admission: SpO2 <92%, inadequate feeding, apnoeas, severe distress, high-risk infant
• PICU: Respiratory failure, recurrent apnoeas, exhaustion

• Self-limiting: Most recover within 7-10 days; cough may persist 2-3 weeks
• Hospital stay: Median 2-3 days for admitted infants
• Mortality: <0.5% overall; <0.1% in previously healthy term infants
• Post-bronchiolitis wheeze: ~40-50% have recurrent wheeze in first 2-3 years; most resolve by school age
• Association with asthma: RSV bronchiolitis associated with increased risk of wheezing in later childhood (not definitively causative)

NICE NG9 — When to Admit

NICE NG9 — When to Seek Urgent Care (Parent Advice)