Print Friendly, PDF & Email

almostadoctor app banner for android and iOS almostadoctor iPhone, iPad and android apps almostadoctor iOS app almostadoctor android app


Bronchiolitis 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%)
Bronchiolitis is the number one reason for paediatric hospital admission. The diagnosis is clinical, but often PCR is performed for RSV to confirm the diagnosis.
It causes more severe illness in younger children, particularly those under 6 months. After 2 years of age, cases are rarely serious.

Symptoms peak on days 2-3 and last about 7-10 days, although a cough may persist for weeks. This is important hone assessing the need for admission – as an unwell child presenting on day 1-2 is much more likely to ned admission as symptoms are likely to worsen – than those presenting later – where symptoms have likely peaked.

Usually the illness is mild and self limiting and no treatment is required. The mainstay of treatment for those that require it is oxygen therapy – increasingly commonly this is via high flow nasal cannulae. There is no proven benefit of corticosteroids or beta-2 agonists.

Indications for hospital admission include:

  • O2 sats <92%
  • Not feeding – breathing hard can mean some infants aren’t able to properly feed and breathe effectively
  • Significant increased WOB, even if the above two factors are normal – especially in the first few days of illness
  • Other signs of unwell child – dehydration, tachycardia, tachypnoea, lethargy / fatigue


  • 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


Typically infection spreads 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.
Particularly pathologically important is airway inflammation. This results in hypoxia, hypercapnia and increased work of breathing.



Typically aged <18 months
  • Annual incidence is about 11% of those <12months
  • Usually occurs between Nov and April in the Northern hemisphere, 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 dyspnoea – is 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

  • Signs of increased work of breathing
    • Subcostal recession
    • Intercostal Recession
    • Prolonged expiration
    • Tracheal tug
  • Poor oral intake
  • Poor urine output
    • Less than half usual output or <3 wet nappies in 24 hours
  • Cyanosis
  • Pallor
  • Tachycardia
  • Tachpnoea
  • Chest hyperinflation
    • Liver displaced downwards
    • Prominent sternum
  • End-respiratory crackles on auscultation
Intercostal recession in a neonate
An example of intercostal recession – in this example seen in a neonate. This file is taken from wikimedia commons and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.


Bronchiolitis is a clinical diagnosis, although PCR may be performed to confirm the presence of RSV.

Usually no investigations are required for diagnosis.

  • RSV – can be easily tested for with PCR of nasopharyngeal mucous secretions.
  • X-ray – usually shows hyperinflation. Not usually performed – as can lea to an over diagnosis of pneumonia and over-use of antibiotics
  • Blood gases – low O2, raised CO2. Not usually performed unless not responding to oxygen therapy, or another indication


There is no specific treatment. The management is supportive, and in many cases, will not require hospitalisation.

The Royal Children’s Hospital guidelines divide cases into mild, moderate and severe categories. The vast majority of cases are mild and can be managed at home. Moderate cases typically have signs of increased WOB, but are still feeding, and many may be suitable to go home, although some are admitted. Severe cases should be admitted for oxygen therapy.

  • 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.
    • Start with regular nasal prongs or other methods and aims or sats >92%
    • If this is not sufficient to maintain sats >92% infants be started on high flow nasal cannulae at 1.5 – 2 L / min / Kg of body weight.
    • High flow nasal cannulae provide positive end-expiratory airway pressure (PEEP). This helps to keep the alveoli and bronchi open at the end of expiration, instead of them collapsing closed – which allows for greater period of gas transfer during the respiratory cycle.
    • With high flow nasal cannulae the air is humidified and heated before being inhaled.
    • Some more recent studies (since 2018) have recommended starting all infants with an oxygen requirement on high flow oxygen, as this decreases hospital stays (by up to 30h) as well as decreasing the risk of further escalation of therapy
    • Oxygen should be tapered down gradually as children improve
  • Fluids and feeding – can be given IV or by NG tube. As much as possible, infants should continue feeding orally as this is associated with better outcomes. NG tube is preferred over IV
  • Steroids and antibiotics should not be given! (no evidence) – although they often are used
  • Bronchodilators via nebuliser were classically often used, but there is no evidence of efficacy and most guidelines now recommend they are not used
  • Mist is not of proven benefit and should not be administered
  • Mechanical ventilation – is needed in about 2% of cases. Indications might include:
    • Apnoeic episodes
    • Oxygen requirement of >50% O2
    • Sats not maintain on high flow nasal cannulae
  • Nasal suction – is not recommended. Nasal saline drops to clear secretions may be useful around the time of feeding
  • Antibiotics and antivirals – are nor indicated


Most cases recover within 2 weeks, the vast majority in a shorter period than this. It appears that some children are more prone to developing severe symptoms and some infants may have several presentations and hospital admissions for bronchiolitis during the first few years of life.
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.


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


  • Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
  • Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
  • Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy
  • RCH – Bronchiolitis clinical practice guidelines

Read more about our sources

Related Articles

Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

Leave a Reply