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Bronchiolitis

Specialties > Child health

Background knowledge 🧠

Definition

  • Bronchiolitis is a common viral lower respiratory tract infection affecting the small airways (bronchioles) in infants and young children.
  • Primarily affects children under 2 years of age, with peak incidence at 3-6 months.
  • Characterised by inflammation, oedema, and necrosis of the epithelial cells lining the bronchioles.

Epidemiology

  • Most common cause of hospitalisation in infants during winter months in the UK.
  • Approximately 1 in 3 infants will develop bronchiolitis in the first year of life.
  • Higher incidence in premature infants, those with underlying cardiopulmonary conditions, and immunocompromised patients.
  • Seasonal peaks in winter, usually between November and March.

Aetiology and Pathophysiology

  • Respiratory Syncytial Virus (RSV) is the most common cause, responsible for 70-80% of cases.
  • Other viral causes include Human Metapneumovirus, Parainfluenza, Influenza, and Rhinovirus.
  • Infection leads to necrosis of the bronchiolar epithelium, mucus production, and submucosal oedema.
  • This results in airway obstruction, air trapping, and hyperinflation of the lungs.
  • Impaired gas exchange leads to hypoxia.

Types

  • Typical Bronchiolitis: Caused by RSV, common in infants, presents with classic symptoms.
  • Atypical Bronchiolitis: May be caused by non-RSV viruses, can present with less common symptoms.
  • Severe Bronchiolitis: Associated with risk factors like prematurity, can lead to respiratory failure.
  • Recurrent Bronchiolitis: Repeated episodes, often linked to underlying conditions like asthma.

Clinical Features 🌡️

Symptoms

  • Initial symptoms resemble an upper respiratory tract infection: cough, rhinorrhoea, and mild fever.
  • Progresses to include tachypnoea, wheezing, and increased work of breathing.
  • Poor feeding and irritability due to respiratory distress.
  • Apnoea episodes, especially in young infants.
  • Symptoms usually peak around day 3-5 of illness.

Signs

  • Tachypnoea and chest recession.
  • Nasal flaring and grunting in severe cases.
  • Fine inspiratory crackles and expiratory wheeze on auscultation.
  • Cyanosis may occur in severe cases.
  • Prolonged expiration and hyperinflation (e.g., prominent ribs).

Investigations 🧪

Tests

  • Diagnosis is primarily clinical, based on history and examination.
  • Pulse oximetry to assess oxygen saturation levels.
  • Nasopharyngeal aspirate or swab for viral PCR if diagnosis is uncertain or for cohorting in hospital.
  • Chest X-ray not routinely required but may be used to rule out complications or differential diagnoses.
  • Blood gas analysis if severe respiratory distress or hypoxia is present.
  • Blood tests (FBC, CRP) usually not indicated unless sepsis is suspected.

Management 🥼

Management

  • Supportive care is the mainstay of treatment (e.g., hydration, oxygen therapy).
  • Oxygen therapy if SpO2 < 92%; high-flow nasal cannula oxygen may be required.
  • NG or IV fluids if oral intake is inadequate.
  • Consider ICU admission for severe cases with impending respiratory failure.
  • No routine use of bronchodilators, corticosteroids, or antibiotics unless there is a coexistent bacterial infection.
  • Palivizumab prophylaxis for high-risk infants to prevent RSV.

Complications

  • Apnoea, particularly in young infants.
  • Respiratory failure requiring mechanical ventilation.
  • Secondary bacterial infections, such as pneumonia.
  • Long-term respiratory sequelae, including recurrent wheeze or asthma.
  • Rarely, death (higher risk in ex-premature or immunocompromised infants).

Prognosis

  • Most infants recover fully with supportive care.
  • Mortality is low in developed countries, but higher in developing countries or among high-risk infants.
  • Follow-up may be required for infants with recurrent episodes or those developing chronic respiratory issues.
  • Recurrent wheezing is common, but most children outgrow this by school age.

Key Points

  • Bronchiolitis is a viral infection primarily affecting infants and young children, with RSV being the most common cause.
  • Diagnosis is clinical, with management focusing on supportive care.
  • Severe cases may require hospitalisation, oxygen therapy, and, rarely, intensive care.
  • Preventative measures include good hygiene practices and Palivizumab for high-risk infants.
  • Prognosis is generally good, but close monitoring is needed for high-risk groups.

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Child health