Bronchiolitis

An acute, infectious disease of the lower respiratory tract that occurs, predominantly, in infants between 2 and 6 months old.

Background/cause

• Most commonly viral infection
  • Usually respiratory syncytial virus (RSV- 75%) but also human metapneumovirus (hMPV), adenovirus and parainfluenza virus
  • Around 70% of all babies will be infected with RSV in the first year of life
    • Around 22% develop symptomatic disease
  • Around a third of all infants will develop a bronchiolitis at some point
• One of the biggest causes of infants under one year requiring admission to hospital (around 3% of all infants)- however the majority stay for 1 day
• Peak incidence in the winter months
• Risk factors include: older siblings, nursery attendance, passive smoking, overcrowding
  • Risk factors for worse disease include prematurity & low birth weight, <12 weeks old, cardiac problems, respiratory problems (CF), Down’s syndrome
  • Breast feeding is protective

Presentation

• Coryzal symptoms may be present prior to the onset of severe symptoms
  • e.g. rhinorrhea, cough, mild fever
    • NB high fever >39°C is uncommon and should prompt investigation into other causes.  Similarly, the absence of fever does not exclude bronchiolitisl
    • Cough is usually dry and wheezy
• Other symptoms include problems with feeding, trouble breathing, vomiting irritability
  • Apnoea may also occur, particularly in young infants
• Signs include tachypnoea, tachycardia, respiratory distress (increased work of breathing- using accessory muscles)
  • Upon auscultation of the lungs, widespread fine inspiratory crackles
    • (In the US, more emphasis is put on the presence of an expiratory wheeze)
  • It is unusual for the patient to appear ‘toxic’- i.e. lethargic/irritable – if so, this requires more urgent management for an underlying cause as these patients may dramatically decline
  • Cyanosis is not common but can be a feature

Investigations

• Most investigations are not warranted if a clinical diagnosis is clear
• Viral swabs from nasopharynx are perhaps the only investigation (other than O2 sats) that will be necessary
• Other tests e.g. blood investigations, CXR- are only required if a patient should deteriorate to more severe illness

Management

• Most cases are mild and self-limiting and can be managed at home.
• Patients requiring referral:
  • Poor feeding (<50% of usual intake in 24 hours, or inadequate to maintain hydration)
  • Lethargy
  • History of apnoea
  • Respiratory rate >70bpm
  • Nasal flaring/grunting
  • Severe chest wall recession
  • Cyanosis
  • Saturations <94%
    • NB Threshold for referring should be low in patients with significant comorbidity/premature/young children (<12 weeks)