Skip to content



A 6-month-old child presents with cough and runny nose for 2 days with increased work of breathing.  She is working hard with moderate subcostal recession. Once you hear the cough, it can only mean one thing….the start of bronchiolitis season.

Bottom Line

  • Bronchiolitis is a common lower respiratory tract illness in children under 2 years.
  • The natural course of bronchiolitis lasts 7-10 days, with day 2-3 being the most severe.
  • Be aware of the risk factors for severe bronchiolitis.
  • If the clinical picture and course doesn’t ‘fit the script’, reconsider the diagnosis.
  • Consider a broad range of differential diagnoses in a child presenting with increased work of breathing and fever.
  • Be aware of the ‘overlap’ between bronchiolitis/viral-induced wheeze and asthma.

What is it?

Bronchiolitis is, as the name suggests, inflammation of the small bronchi and bronchioles. The clinical entity we know as bronchiolitis is the most common admission diagnosis in patients under 2, accounting for high morbidity in this population. More succinctly;

“A seasonal viral illness characterized by fever, nasal discharge, and dry, wheezy cough. On examination, there are fine inspiratory crackles and/or high-pitched expiratory wheeze.” – The University of Nottingham, in their 2009 Acute Breathing Difficulty Guideline.

It is most often caused by respiratory syncytial virus (50-80%), as well as parainfluenza (especially PIV3), human metapneumovirus, influenza, rhinoviruses, and adenovirus. In the words of my first general paediatric consultant:

“Bronchiolitis is a typical winter illness, which almost every child gets in their first two years of life. What matters is first, how old you are when you get it, and secondly, what kind of condition you’re in.”

What are the clinical features?

Several days of upper respiratory tract symptoms, including fever, rhinorrhoea, and coryza. These develop into a wheeze, tachypnea, increased work of breathing, moist cough, and fevers. The increased work of breathing often leads to decreased oral intake, with or without dehydration. In infants, poor feeding and apneas with or without cyanosis may be present.

Auscultation of the lungs may reveal a wheeze and transmitted upper airway sounds. A focal zone with decreased air entry or coarse crackles is more consistent with pneumonia.

It is well described that a typical course of bronchiolitis lasts 7-10 days, with night 2-3 being the most severe. In this respect, it is important to reconsider the diagnosis in any patient not ‘sticking to the script’, or deteriorating after initial improvement. A cough may last for up to four weeks.


The diagnosis is primarily clinical. Clinical features of an area of the lung with decreased air entry or consistent focal crackles warrant a chest radiograph to exclude pneumonia. A chest radiograph infrequently adds to the clinical picture and is not routine.

Some clinicians will obtain a nasopharyngeal aspirate or flocculated swab for respiratory virus PCR. There is also a rapid antigen test, which is good for ruling in, rather than ruling out, a particular virus.

Although typing of the respiratory virus causing bronchiolitis may be helpful for bed management and nursing, it is unlikely to alter management.

This point remains controversial as knowledge of the causative organism may allow some prognostication regarding illness course and prevent unnecessary antibiotic usage. It does not rule out dual respiratory tract pathology, such as secondary bacterial infection.

In particular, there is merit to obtaining swabs in patients with risk factors for severe infection, thus:

Risk Factors for Severe Infection

  • Age <1 yo, especially less than 6 weeks
  • Congenital heart disease
  • Neurological conditions
  • Chronic respiratory illness
  • Pulmonary hypertension
  • Ex-premature infants
  • Inborn errors of metabolism
  • Trisomy 21
  • Cystic fibrosis
  • Immunodeficiency
  • A previous severe bronchiolitis illness requiring CPAP or PICU admission.

Around 50% of children with severe infections have none of the above risk factors.

Children at risk of severe infection and mild symptoms should be admitted and observed.

As noted earlier, the course of the illness is that night 2-3 is usually the most severe, thus any child presenting earlier will potentially worsen, sometimes quite rapidly.

How do we manage it?

Management is supportive, with rehydration and fluid maintenance whilst unable to feed and respiratory support as required. If the child is unlikely to deteriorate and does not require inpatient observation or additional support, they can often be managed in the outpatient setting. It’s essential to provide clear safety-net advice for when to return to ED as well as strongly encouraging an early GP review.

Admit for observation

Infants <6/52 and patients with the risks for severe infection above are at risk of apnoeas, so cardiorespiratory monitoring is indicated. Oxygen saturation monitoring is indicated in all children. Keep a close eye on work of breathing and hydration as these can change as the illness progresses.

What level of oxygen saturation is acceptable?

There are differing opinions regarding target oxygen saturation in patients with bronchiolitis. Most would agree on a target somewhere between ≥94% and ≥92%. But which?

Consider the oxygen-haemoglobin dissociation curve:

Conditions that push the curve to the right (higher PO2 to maintain SaO2 and curve has a steeper gradient), are decreasing pH, increasing temperature.

Thus, in a febrile, acidotic child the curve is pushed to the right, requiring a higher PO2 to maintain the same level of saturation and thus increasing the likelihood of desaturations. In these children, aiming for an SaO2 of 94% would be reasonable. Local guidelines may have differing suggestions.

Respiratory support

Oxygen delivery can be via nasal cannulae, or if bronchiolitis severe by high-flow humidified oxygen via nasal prongs.  High-flow provides continuous positive airway pressure (CPAP) and aims to avoid intubation.

Flow rates of 2l/kg/min provide a PEEP of 4-8cm, improving the functional residual capacity.

In life-threatening cases, sedation, intubation and ventilation may be necessary and should be done with PICU and senior support. In regional and rural settings, it’s important to be aware of local limitations and consider early transfer to a tertiary centre for deteriorating, high-risk patients. For the care of such patients, make early contact with your regional Paediatric Emergency Transfer Services.


Children with acute illness are susceptible to SIADH and hyponatremia. Thus, it’s important that whilst supporting the increased insensible losses and decreased intake as a result of respiratory distress we don’t over hydrate the patient. Around 2/3 maintenance for an infant not tolerating oral intake is sufficient to both hydrate and reduce the likelihood of SIADH. Most paediatric departments would use 0.9% saline and 5% dextrose.

In mild cases of bronchiolitis, small, frequent feeds may provide sufficient hydration. As respiratory distress increases, nasogastric feeds (continuous vs bolus) may be required. For a child with severe bronchiolitis, on high-flow nasal prongs or moderately dehydrated, intravenous therapy is indicated.

Other Therapies

Antibiotics are not indicated for bronchiolitis, nor is there a benefit in the use of steroids, nebulized adrenaline, or bronchodilators. Additionally, there is no benefit in physiotherapy or macrolide antibiotics.

Although salbutamol does not alter the clinical course of bronchiolitis, in the case of a strong family history of atopic disease or asthma it would not be unreasonable to trial a course of salbutamol, particularly in the child >6 yo who is presenting with a wheeze.

It’s important to assess the child pre- and post-salbutamol for both subjective and objective clinical response. This may also have some utility in differentiating between viral bronchitis and a viral-induced wheeze. Again, this is a controversial sub-topic with evolving evidence.

Bronchiolitis has a broad range of differential diagnoses; it is important to consider these, particularly if the patient is not responding as expected to your initial management, or if there are features of the history or examination of an alternative diagnosis.

What’s the differential?

Pneumonia or other pulmonary infections, including mycoplasma and pertussis – listen for focal crackles or signs, productive cough or radiological features of pneumonia. These patients will usually have a fever, in addition to cough and tachypnoea. Consider viral, bacterial, chlamydial or mycoplasma pneumonia. This is a common alternative diagnosis for bronchiolitis.

Recurrent viral-triggered wheezing – another common alternative diagnosis, viral-triggered wheeze may present quite similarly. Features in the history that might point you towards a viral-induced wheeze, is that of an antecedent URTI which had resolved, followed by wheeze and work of breathing a few days later, with or without fever. Differentiating between RSV bronchiolitis and a viral-induced wheeze can be particularly challenging.

Meningitis – most consultants can describe a patient who presents during a “bronchiolitis epidemic” who has meningitis. Always consider this differential diagnosis. Although it’s had to find case reports in the medical literature, unfortunately, the lay press has many examples of this.

Foreign body aspiration – characterized by rapid onset and failure of initial management. May have a low-grade fever. Have a high index of suspicion.

Croup – usually stridor rather than a wheeze, and with a similar gamut of causative organisms. Laryngotracheobronchitis can present with a wheeze in a child with bronchitic disease.

Aspiration pneumonia – consider more strongly in children with poor airway protection, including spastic cerebral palsy, or in any child having seizures or convulsions.

Gastro-oesophageal reflux – up to 40-50% of infants with GORD present with wheeze or respiratory symptoms. There is also an association with chronic cough.

Asthma – an acute exacerbation is less likely to have fevers, and will often have a personal history of atopy or allergy, or a family history of asthma. It would be rare to diagnose a child under two with asthma at a first presentation to the hospital with a wheeze.

Chronic pulmonary disease – chronic neonatal lung disease or prematurity predisposes the child to respiratory infections.

A mediastinal mass – there are multiple case reports of mediastinal masses presenting with a wheeze and respiratory distress.

Tracheoesophageal fistula – late-presentation of H-type tracheoesophageal fistula may present as coughing, abdominal distension, and recurrent chest infections. Sundar’s well described 1975 case series can be found here.

Congenital heart disease and heart failure – to be considered in any neonate presenting with increased work of breathing, with or without apneas. These patients will look unwell, with a constellation of symptoms including disproportionate tachycardia, poor perfusion with or without cyanosis, weak femoral pulses & murmurs.

Vascular ring, congenital lobar emphysema or a bronchogenic cyst  – may also present in neonates with a “bronchiolitis-sounding” history.

Selected references

Coffin. S,E., Bronchiolitis: In-Patient Focus, Pediatric Clinics of North America – Volume 52, Issue 4 (August 2005).

Grimes, A. All That Wheezes… HOSPITAL PEDIATRICS Vol. 2 No. 1 January 1, 2012 pp. 47 -50

Zorc, JJ & Breese Hall, C. Bronchiolitis: Recent Evidence on Diagnosis and Management. Pediatrics. Vol. 125 No. 2 February 1, 2010  pp. 342 -349 (doi: 10.1542/peds.2009-2092).

Marlais M, Evans J, Abrahamson E. Arch Dis Child 2011;96:648-652 doi:10.1136/adc.2010.201079 Clinical predictors of admission in infants with acute bronchiolitis.

Royal Children’s Hospital, Melbourne. Clinical practice guidelines : Bronchiolitis.

Paediatric Grand Rounds – Acute Viral Bronchiolitis in Children by Dr Nitin Kapur, Respiratory Paediatrican. Lecture on 5th June 2013 @ Royal Children’s Hospital, Herston QLD. Slides.

Fitzgerald, D.A. & Kilham, H.A., Bronchiolitis: assessment and evidence based management. MJA 2004; 180(8): 399-404.

Lakhanpaul M, Armon K, Eccleston P, et al. An Evidence Based Guideline for the Management of Children Presenting With Acute Breathing Difficulty. Nottingham, United Kingdom: University of Nottingham; 2002. 

Louie, M C & Bradin, S. Foreign Body Ingestion and Aspiration Pediatrics in Review August 2009; 30:295-301.

Sheikh S, Allen E, Shell R, Hruschak J, Iram D, Castile R, McCoy K. Chronic aspiration without gastroesophageal reflux as a cause of chronicrespiratory symptoms in neurologically normal infants. Chest. 2001 Oct;120(4):1190-5. PMID: 11591559.

Saglani, S., et al. Investigation of young children with severe recurrent wheeze: any clinical benefit? Eur Respir J 2006 27:29-35; doi:10.1183/09031936.06.00030605. 

Sheikh S, Stephen T, Howell L, Eid N. Gastroesophageal reflux in infants with wheezing. Pediatr Pulmonol. 1999 Sep;28(3):181-6. PMID: 10495334.

National Asthma Council Australia. Asthma Management Handbook 2006. Melbourne, 2006.

Heinz, P. & Dunne, J. Wheeze and mediastinal mass: A challenging patient. Emergency Medicine Vol 16(3)241-243, June 2004. DOI: 10.1111/j.1742-6723.2004.00573.

Sundar, B., Guiney, E.J. & O’Donnell, E. Congenital H-type tracheo-oesophageal fistula. Arch. Dis. Ch. 1975 (50)862. 

Hsu, D. & Pearson G., Heart Failure in Children. Part I: History, Etiology, and Pathophysiology. Circ Heart Fail 2009;2;63-70; DOI: 10.1161/CIRCHEARTFAILURE.108.820217.

Phelan, E., Ryan, S. & Rowley, H. Vascular rings and slings: interesting vascular anomalies. The Journal of Laryngology & Otology (2011), 125, 1158–1163.



No data was found

Leave a Reply

Your email address will not be published. Required fields are marked *

2 thoughts on “Bronchiolitis”

  1. Hi,

    Great summary and review -thank you!

    A couple of comments, based on the most recent Australian (predict) guidelines published since this article was written;
    – CXR is rarely indicated unless sick enough to warrant intensive care review. If consistent focal changes with fever, then treatment for pneumonia can be started based on clinical suspicion. Otherwise, CXR changes may falsely suggest pneumonia raising the chances of inappropriate treatment with antibiotics – something we all need to worry about in this current era! One study has shown that CXR increases the use of antibiotics 5 fold!
    – Continuous oxygen monitoring will almost certainly lead to prolonged admission. We know that children can tolerate lower saturations than we generally choose to treat. Children flying experience sats down to the 80s with no evidence of harm. Latest guidelines suggest we use intermittent oxygen monitoring, unless high risk of deterioration.
    – Bronchodilators in the under 1 age group, have not shown to provide benefit in any clinically meaningful measure and can have significant side effects (not to mention the trauma of holding a spacer to a non-compliant infant). Although it is tempting to trial something, current guidelines suggest our best treatment in this scenario is to do nothing.

  2. Hi! Thanks for the detailed explanations. I was wondering if there’re any clinical features I can look out for to distinguish between a recurrent viral-induced wheeze vs bronchiolitis? thanks!