Bronchiolitis

Original article by Tom Leach | Last updated on 28/6/2014
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Introduction

This is the most common serious respiratory infection during infancy. It comes in winter epidemics, during which time, 2-3% of all infants are admitted to hospital each year. The primary cause is RSV – respiratory syncytial virus – which accounts for 80% of cases.
  • In more temperate climates, the epidemics come in the ‘wet’ season
  • Prognosis is good, but it does carry a mortality (~1%)
 

RSV

  • Highly Infectious
  • A single-stranded RNA virus
  • In adults, and older children, RSV only causes coryzal, and sometimes, flu-like symptoms.
  • Almost all children will have been infected at some stage by the age of 2
  • Often, infants catch the virus from older siblings, who bring it home from school, or they catch it directly themselves in environments with lots of children present.
  • Spread trough viral shedding, via coughing and sneezing. It can also live on surfaces and clothes outside the body for up to 5 hours.
  • Other causes include parainfluenza, virus, influenza virus and adenoviruses
 

Pathology

Typically infection spread from the upper respiratory tract, into the medium and small bronchi, resulting in epithelial necrosis. This results in oedema and epithelial shedding, which can cause obstruction, particularly on expiration.

 

Presentation

Typically aged <18 months
  • Annual incidence is about 11% of those <12months
  • Usually occurs between Nov and April, with peak in Jan and Feb
Coryzal symptoms come first 2-3 days, followed by:
  • Dry cough
  • Increasing breathlessness (often RR >50), may include Rib recession
  • Cough may continue for 1-2 weeks
  • Wheezing may/may not be present
  • Fever
  • Difficulty feeding – due to dyspnoeais the main reason for admission
  • Symptoms often worse at night
  • Apnoea
  • Symptoms tend to be worse the younger the child. Children >” are rarely seriously ill, whilst those <^ months are at the greatest risk.
 

Signs and Symptoms of severe disease

  • Sharp, dry cough
  • Cyanosis
  • Pallor
  • Tachycardia
  • tachpnoea
  • Chest hyperinflation
    • Liver displaced downwards
    • Prominent sternum
  • Subcostal recession
  • Intercostal Recession
  • Prolonged expiration
  • End-respiratory crackles on auscultation
 

Investigations

  • RSV - can be easily tested for with nasopharyngeal mucous secretions.
  • X-ray – usually shows hyperinflation
  • Blood gases – low O2, raised CO2.

 

Management

There is no specific treatment. The management is essentially supportive, and in many cases, will not require hospitalisation.
  • Signs that suggest severe disease: lethargy, cyanosis, co-existing illness (e.g. immunodefiency, congenital heart defects)
  • Oxygen - Delivered by nasal specs, head box, or in the smallest infants, tent. The amount of O2 is determined by pulse oximetry and blood gas results.
  • Steroids and antibiotics should not be given! (no evidence) – although they often are used
  • Bronchodilators via nebuliser are often used, but are not of proven benefit.
  • Mist is not of proven benefit and should not be administered
  • Fluids – can be given IV or by NG tube.
  • Mechanical ventilation – is needed in about 2% of cases.
 

Prognosis

Most cases recover within 2 weeks
Bronchiolitis obliterans is a rare complication. This is a form of non-reversible lung damage, in which the bronchioles become plugged by granulation tissue. There will be:
  • Very low FEV1 (<21% of normal)
  • Dry cough
  • SOB
  • Wheeze
  • There is very little treatment. Some cases may improve with a lung transplant.
  • There are many causes, not just RSV infection in childhood, often including occupational lung disease.
 

Prevention

There is an injection, containing monoclonal antibody; palivizumab. This is sometimes given to high risk (usually pre-term) babies. It reduces the severity of the infection and the risk of serious consequences. Its use is limited due to the cost, and the need for several injections