Bronchiolitis is an acute viral infection of the lower respiratory tract that occurs primarily in the very young. It is a clinical diagnosis based upon typical symptoms and signs. Bronchiolitis is generally a self-limiting illness, and management is mostly supportive.
There is some discrepancy between the use of 'bronchiolitis' in the UK and in the USA and other parts of Europe, and no universally accepted definition for such a common condition. In the UK, the term describes an illness in infants, beginning as an upper respiratory tract infection (URTI) that evolves with signs of respiratory distress, cough, wheeze, and often bilateral crepitations. In North America, bronchiolitis is used to describe a wheezing illness associated with an URTI in children up to the age of 2 years (whilst this would be described as a 'viral-induced wheeze' in the UK). This causes difficulties in interpreting results of clinical trials, as the populations may display considerable heterogeneity. This article is based on UK guidelines.
Bronchiolitis is caused by a viral infection, most often respiratory syncytial virus (RSV). This is responsible for up to 80% of cases. Other possible viral causative agents include human metapneumovirus (hMPV), adenovirus, rhinovirus, and parainfluenza and influenza viruses. In some cases there may be infection with more than one virus.
- Bronchiolitis occurs in infants under the age of 2 years, peaking between the ages of 3 months and 6 months.
- It is the most common lower respiratory infection in the first year of life in the UK. Around a third of babies develop bronchiolitis before the age of 1 year, and 2-3% of infants with bronchiolitis require hospitalisation.
- In 2011/12 in England, there were 30,451 admissions for bronchiolitis.
- Peak incidence is in the winter months (October to March). There tends to be an annual 6- to 8-week epidemic where incidence peaks.
Environmental and social risk factors:
- Older siblings.
- Nursery attendance.
- Passive smoke, particularly maternal.
Breastfeeding is considered protective and should be encouraged for this and other reasons.
Most admissions (85%) for bronchiolitis are in infants born at term with no risk factors. Risk factors for severe disease and/or complications include:
- Prematurity (<37 weeks).
- Low birth weight.
- Mechanical ventilation when a neonate.
- Age less than 12 weeks.
- Chronic lung disease (eg, cystic fibrosis, bronchopulmonary dysplasia).
- Congenital heart disease.
- Neurological disease with hypotonia and pharyngeal discoordination.
- Insulin-dependent diabetes.
- Congenital defects of the airways.
- Down's syndrome.
National Institute for Health and Care Excellence (NICE) guidelines advise that bronchiolitis should be considered in children under the age of 2 years who present with a 1- to 3-day history of coryzal symptoms, followed by:
- Persistent cough; and
- Either tachypnoea or chest recession (or both); and
- Either wheeze or crackles on chest auscultation (or both).
Other typical features include fever (usually of less than 39°C) and poor feeding. Consider an alternative diagnosis such as pneumonia if temperature is higher and crackles are focal. Consider viral-induced wheeze if there is wheeze without crackles, episodic symptoms and/or a family history of atopy.
Very young babies may present with apnoea alone, with no other signs.
Take a history, and examine the child, making note of capillary refill time, respiratory rate, heart rate, chest signs, etc. Following examination, measure oxygen saturation in any child with suspected bronchiolitis.
Consider referral to secondary care if the respiratory rate is >60 breaths/minute, or if there is inadequate fluid intake or there are signs of dehydration; also, if the child is less than 3 months of age or was born prematurely, or there is comorbidity (particularly respiratory or heart disease, or immunodeficiency). Take into account social circumstances and the ability of the carer to assess deterioration.
Refer immediately if any of the following are present:
- Apnoea (observed or reported).
- Marked chest recession or grunting.
- Respiratory rate >70 breaths/minute.
- Central cyanosis.
- Oxygen saturation of less than 92%.
- The child looks seriously unwell to a healthcare professional.
- Viral-induced wheeze. Consider if there is wheeze but no crackles, a history of episodic wheeze, and/or a family or personal history of atopy.
- Pneumonia. Consider if temperature is above 39°C and there are persistent focal crackles.
- Pulmonary oedema.
- Foreign body inhalation.
- Oesophageal reflux.
- Cystic fibrosis.
- Kartagener's syndrome.
- Pulse oximetry.
- Viral throat swabs for respiratory viruses (in secondary care)
Chest X-ray, blood tests and blood gases are not advised for the routine management of bronchiolitis, unless there is evidence of deterioration and worsening respiratory distress. As above, fever >39°C or focal chest signs would prompt investigations such as a chest X-ray to rule out alternative diagnoses such as pneumonia, or complications.
- Most infants with acute bronchiolitis will have mild, self-limiting illness and can be managed at home. Supportive measures are the mainstay of treatment, with attention to fluid input, nutrition and temperature control.
- Advise the parents that the illness is self-limiting and symptoms tend to peak between 3-5 days of onset.
- Anti-pyretic agents are needed only if a raised temperature is causing distress to the child.
- Within general practice, a doctor's role is to assess current severity of illness and, for those with mild-to-moderate disease, to support and monitor. Consider whether the presentation is in the early stages of disease, when a child is more likely to become worse before improving. Careful safety netting is important, teaching parents to spot deterioration and to seek medical review should this occur.
- If referring to hospital, give supplementary oxygen whilst awaiting admission in children whose oxygen saturations are persistently below 92%.
Even amongst hospitalised children, supportive care is the mainstay of treatment, including oxygen and nasogastric feeding where necessary. Upper airway suction may be useful if there is difficulty feeding or a history of apnoea. Continuous positive airway pressure (CPAP) may be considered in those who have impending respiratory failure. High-flow nasal cannula oxygen (HFNC) is commonly used for bronchiolitis in secondary care as it is thought to reduce the need for CPAP and ventilation. Research is underway to establish the evidence for this[9, 10].
Other treatments have shown inconsistent or little evidence of benefit and NICE guidelines advise against using them:
- Bronchodilators: no benefit has been found in improving oxygen saturations, reducing time to resolution or need for/duration of hospital admission.
- Corticosteroids: trials have consistently failed to provide evidence of benefit.
- Nebulised racemic adrenaline (epinephrine) - racemic = 1:1 mixture of the dextrorotatory and levorotatory isomers: one study reported that inhaled racemic adrenaline was no better than inhaled saline.
- Hypertonic saline: thought to act by unblocking mucous plugs and reducing airways obstruction. A Cochrane Review concluded that there was low- to medium-quality evidence that its use did slightly reduce length of hospital stay and clinical severity scores.
- Antibiotics: there is minimal evidence to support their use, except in a small subset of patients with complications or respiratory failure.
- Ribavirin: may reduce the need for mechanical ventilatory support and the number of days in hospital but there is no clear evidence of clinically relevant benefits (eg, preventing respiratory deterioration or mortality).
- Chest physiotherapy techniques analysed so far have not been shown to improve the severity of the disease.
- Most children with bronchiolitis make a full recovery.
- The illness is typically self-limiting, lasting 3-7 days. The cough settles within three weeks in most.
- Bronchiolitis is more likely to be severe in children with chronic lung disease, who are under 3 months of age or who were born <32 weeks of gestation.
- There is an association with long-term respiratory conditions such as asthma but it is not known if there is causality.
- Death from bronchiolitis is uncommon. In England there are around 70 deaths per year due to bronchiolitis. Most deaths occur in infants younger than 6 months or in those with underlying cardiac or pulmonary disease.
Recent years have seen the development of agents which provide passive immunity to RSV: RSV immunoglobulin (RSV-Ig) which has been superseded by palivizumab, a monoclonal antibody. It has been shown to reduce RSV-related hospitalisation and intensive care admissions significantly. The Joint Committee on Vaccination and Immunisation recommends that it should be used by those at high risk of severe RSV disease:
- Those with bronchopulmonary dysplasia (BPD, also known as chronic lung disease) due to prematurity or chronic lung disease.
- Those at high risk due to congenital heart disease.
- Those at high risk due to severe combined immunodeficiency syndrome.
The first dose should be administered before the start of the RSV season.
Disease transmission may be limited by :
- Hand washing.
- Use of gloves and aprons or gowns when in direct contact with the patient.
- Isolation of infected patients in cubicles.
Further reading and references
; NICE Quality Standard, June 2016
; Maybe there is no such thing as bronchiolitis. CMAJ. 2016 Mar 15188(5):351-4. doi: 10.1503/cmaj.150683. Epub 2016 Feb 1.
; NICE Guideline (May 2015)
; Risk factors for hospital admission with RSV bronchiolitis in England: a population-based birth cohort study. PLoS One. 2014 Feb 269(2):e89186. doi: 10.1371/journal.pone.0089186. eCollection 2014.
; The treatment of bronchiolitis. Arch Dis Child. 2008 Sep93(9):793-8. Epub 2008 Jun 6.
; Respiratory syncytial virus prophylaxis in children with cardiac disease: a retrospective single-centre study. Cardiol Young. 2013 Apr 29:1-7.
; A comparison of healthcare resource use for rotavirus and RSV between vulnerable children with co-morbidities and healthy children: a case control study. J Med Econ. 201316(4):560-5. doi: 10.3111/13696998.2013.774278. Epub 2013 Feb 22.
; Down syndrome: a novel risk factor for respiratory syncytial virus Pediatrics. 2007 Oct120(4):e1076-81.
; NICE CKS February 2017 (UK access only)
; High flow nasal cannulae for acute viral bronchiolitis in young infants: evidence-based medicine is underway to define target populations and optimal flows. J Thorac Dis. 2017 Jul9(7):1763-1766. doi: 10.21037/jtd.2017.06.42.
; High-flow nasal cannula therapy for infants with bronchiolitis. Cochrane Database Syst Rev. 2014 Jan 20(1):CD009609. doi: 10.1002/14651858.CD009609.pub2.
; Bronchodilators for bronchiolitis. Cochrane Database Syst Rev. 2014 Jun 17(6):CD001266. doi: 10.1002/14651858.CD001266.pub4.
; Glucocorticoids for acute viral bronchiolitis in infants and young children. Cochrane Database Syst Rev. 2013 Jun 4(6):CD004878. doi: 10.1002/14651858.CD004878.pub4.
; Racemic adrenaline and inhalation strategies in acute bronchiolitis. N Engl J Med. 2013 Jun 13368(24):2286-93. doi: 10.1056/NEJMoa1301839.
; Nebulised hypertonic saline solution for acute bronchiolitis in infants. Cochrane Database Syst Rev. 2017 Dec 2112:CD006458. doi: 10.1002/14651858.CD006458.pub4.
; Antibiotics for bronchiolitis in children under two years of age. Cochrane Database Syst Rev. 2014 Oct 9(10):CD005189. doi: 10.1002/14651858.CD005189.pub4.
; Leukotriene inhibitors for bronchiolitis in infants and young children. Cochrane Database Syst Rev. 2015 Mar 16(3):CD010636. doi: 10.1002/14651858.CD010636.pub2.
; Ribavirin for respiratory syncytial virus infection of the lower respiratory tract in infants and young children. Cochrane Database Syst Rev. 2007 Jan 24(1):CD000181.
; Chest physiotherapy for acute bronchiolitis in paediatric patients between 0 and 24 months old. Cochrane Database Syst Rev. 2016 Feb 12:CD004873. doi: 10.1002/14651858.CD004873.pub5.
; Public Health England (March 2013)