A Summary of Bronchiolitis

A Summary of Bronchiolitis: A review of bronchiolitis, evidence behind various treatment regimens, and suggested admission criteria – A Resident Clinical Pearl

 Melanie Johnston, R3

Integrated FMEM, Dalhousie

Reviewed by Dr. Patricia Dutton

Copyedited by Dr. Mandy Peach

Respiratory illnesses are the second most common ED presentation for paediatric patients, particularly during the winter months, in Canada. 1,2 These paediatric patients with respiratory pathologies are at risk of rapid clinical deterioration; a thorough history and exam with careful attention to respiratory evaluation is critical. Three of the most common paediatric respiratory complaints presenting to the ED include croup, asthma, and bronchiolitis. This pearl will focus on a review of bronchiolitis, its presentation, evaluation, and the evidence behind various treatments.

What is bronchiolitis:

Bronchiolitis is a viral lower respiratory tract infection. It is characterized by obstruction of small airways cause by acute inflammation, swelling/edema, and necrosis of the cells lining the small airways.2 Airways are further narrowed by increased mucous production. The most common causes are respiratory syncytial virus (RSV), influenza, rhinovirus, adenovirus, and parainfluenza.2 These viruses are transmitted by secretions from the nose/mouth and via respiratory droplets in the air. Co-infection with multiple viruses occurs in 10-30% of hospitalized children.2

Figure 1: Pathophysiology of Bronchiolitis.3


RSV season generally begins in November and persists until April. Bronchiolitis generally presents with a first episode of wheezing before the age of 24 months during the winter months.2 It is the most common reason for admission to hospital in the first year of life in Canada, and more than one-third of children will be affected by bronchiolitis in their first two years of life.2


Bronchiolitis may present with a wide range of symptoms from mild upper respiratory tract infection symptoms (cough, rhinorrhea, fever) to respiratory distress (tachypnea, wheeze, grunting, indrawing, abdominal breathing, and retractions).4 The peak severity of illness usually occurs on day 2-3 of the illness with resolution over 7-10 days.2,6 Cough can persist in infants for up to three weeks after onset.

Pediatric populations at risk for more serious illness include:
– Age <3 months
– Infants born prematurely (<35 weeks gestation)
– Chronic lung disease
– Congenital heart disease
– Chronic neurological conditions
– Immunodeficiency
– Trisomy 21

Patients with the above risk factors are at risk of rapid clinical deterioration even if presenting early in illness with mild symptoms.2,5


The diagnosis of bronchiolitis is considered to be clinical based on history and physical exam. The illness generally begins with a 2-3 day prodrome of mild URTI symptoms including cough, fever, rhinorrhea. This may progress to tachypnea, wheeze, and signs of respiratory distress.2 If respiratory distress is interfering with feeding, there may be signs of dehydration (delayed cap refill, dry mucous membranes, no tears produced with crying). Initial assessment should focus on overall appearance, breathing, and circulation. A tool to assist in establishing a general first impression of the paediatric patients stability is the paediatric assessment triangle. Abnormalities in any domain of the triangle (appearance, work of breathing, circulation) should be noted and factored into initial workup with potential to decompensate, with abnormalities in two domains indicative of potentially serious illness.

Figure 3: Pediatric Assessment Triangle.1

Signs of respiratory distress to note on exam include:

– Tachypnea
– Intercostal/subcostal retractions
– Accessory muscle use
– Nasal flaring
– Grunting
– Colour change or apnea
– Wheezing
– Low O2 saturation (<90%)

In stratifying the severity of illness in bronchiolitis, the Royal Children’s Hospital of Melbourne has proposed the following chart to assist with assessment:

Figure 4: Stratifying severity of illness in bronchiolitis, adapted from RCHM.5


Bronchiolitis is considered to be a clinical diagnosis. As such, the majority of patients won’t require any additional investigations. If there is diagnostic uncertainty, then the following investigations may be considered:


Bronchiolitis is a self-limiting disease with peak severity generally at day 3-4 of illness.2,5,6 Most children have mild disease and can be managed with supportive care at home. For those ultimately admitted, focus in hospital is on supportive care with assisted feeding, nasal suctioning, and oxygen therapy as needed.


Most children do well and the symptoms will peak by day 3-5 of illness.

Criteria for safe discharge home include:
– O2 > 90-92%
– Adequate oral hydration
– Mild respiratory symptoms
– Access to reliable follow-up care if needed.2

Criteria for hospital admission include:

– Persistent oxygen saturation <92% and requiring supplemental oxygen AND/OR
– Unable to maintain oral hydration (fluid intake 50% of normal), requiring IV or NG fluids AND/OR
– Persistent moderate-severe respiratory distress
– Apnea (observed or reported)
– Children with risk factors for severe disease (see above).2

Admission or a period of observation in the ED can be used to document feeds and monitor vital signs/oxygen status. Other considerations for admission to hospital include social circumstances, comfort of caretaker in managing child at home, distance to healthcare facility in case of deterioration, and the phase of illness.


1. Pediatric Respiratory Illnesses, Dr Allan Shefrin. Jan 30, 2020. Accessed at https://criticallevels.ca/2020/01/30/episode-3-paediatric-respiratory-illnesses-dr-allan-shefrin/

  1. Bronchiolitis: Recommendations for diagnosis, monitoring and management of children one to 24 months of age. Canadian Pediatric Society. Friendman, J., Rieder, M., Walton, J. et al. Nov 3, 2014. Accessed at https://emergencymedicinecases.com/wp-content/uploads/filebase/pdf/CPS-guidelines-bronchiolitis.pdf.

    3. Bronchiolitis. Cleveland Clinic. Accessed online at: https://my.clevelandclinic.org/health/diseases/8272-bronchiolitis

  2. Bronchiolitis, Bottom Line Recommendations. Trekk: Translating Emergency Knowledge for Kids. October 2020. Accessed online at: https://trekk.ca/system/assets/assets/attachments/502/original/2021-01-08-Bronchiolitis_v_3.0.pdf?1610662513

    5. Bronchiolitis, Clinical Practice Guidelines. The Royal Children’s Hospital Melbourne. Accessed online at: https://www.rch.org.au/clinicalguide/guideline_index/Bronchiolitis/

    6. Bronchiolitis, Episode 59. Emergency Medicine Cases. Accessed online at https://emergencymedicinecases.com/episode-59-bronchiolitis/

    7. Bronchiolitis in children: diagnosis and management. NICE guideline. June 1, 2015. Accessed online at: https://www.nice.org.uk/guidance/ng9/resources/bronchiolitis-in-children-diagnosis-and-management-pdf-51048523717

    8. https://www.connectedcare.sickkids.ca/quick-hits/2019/8/29/volume6-efnk4-nyn48-max8h-rczlx (Pediatric assessment triangle)

    9. Bronchioitis, accessed online at: https://en.wikipedia.org/wiki/Bronchiolitis.


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