Bronchiolitis is the most common lower respiratory tract infection in infants and young children aged < 2 years. Each year in the United States, LRTIs cause > 100,000 hospitalizations of children aged < 1 year.


  • RSV accounts for 50-80% of cases, but rare in children >2 yo.3
    • Late fall epidemic peaking Nov-March, in the US.4
  • Human Metapneumovirus (HMPV) accounts for 3-19% 5,6
    • Similar seasonal variation to RSV.  
  • Parainfluenza, influenza, adenoviruses, coronaviruses, rhinoviruses, and enteroviruses are other causes.4-6
  • Rhinoviruses have been shown to play a larger role in Asthma.7


  • The American Academy of Pediatrics defines it as any of the following in infants: 1
    • Rhinitis
    • Tachypnea
    • Wheezing
    • Cough
    • Crackles
    • Use of accessory muscles
    • Nasal flaring 

Risk Factors for Severe Bronchiolitis

  • Age < 6-12 weeks11-13
  • Prematurity < 35-37 weeks’ gestation11-13
  • Underlying respiratory illness such as bronchopulmonary dysplasia1
  • Significant congenital heart disease; immune deficiency including HIV, organ or bone marrow transplants, or congenital immune deficiencies14,15
  • Altered mental status (impending respiratory failure) 
  • Dehydration due to inability to tolerate oral fluids 
  • Ill appearance12
  • Oxygen saturation level ≤ 90%1
  • Respiratory rate: > 70 breaths/min or higher than normal rate for patient age1,12
  • Increased work of breathing: moderate to severe retractions and/or accessory muscle use1 
  • Nasal flaring
  • Grunting 

Risk Factors for Apnea

  • Full-term birth and < 1 month of age16,17
  • Preterm birth (< 37 weeks’ gestation) and age < 2 months post birth11-13,17 
  • History of apnea of prematurity 
  • Emergency department presentation with apnea17
  • Apnea witnessed by a caregiver17

Diagnostic Testing

  • Xray
    • Radiographs increase the likely hood of a physician giving antibiotics, even if the X-ray is negative.18-20
    • Routine radiography is discouraged but may be helpful when severe disease requires further evaluation or exclusion of foreign body. 
  • Viral testing is not necessary for the diagnosis but may help when searching for the cause of fever in young infants.
    • 2016 ACEP fever guidelines note that positive viral testing can impact further workup of fever for a serious bacterial infection (SBI).21
  • In infants <28 days, serious bacterial infection is high, even in patients with bronchiolitis: 10% RSV positive and 14% RSV negative 22. Standard fever evaluation is recommended. 
  • In the 28-60 day old group, SBI rates were 5.5% RSV positive and 11.7% RSV negative. All were UTIs.22 Urinalysis is recommended. 

Emergency Department Treatment

  • Oxygen
    • Keep O2 saturation >90%
    • Clinicians may choose not to use continuous pulse oximetry (weak recommendation due to low-level evidence and reasoning)1
  • Fluids
    • IV or NG administration of fluids to combat dehydration, until respiratory distress and tachypnea resolve. 
  • Suctioning
    • Routine use of “deep” suctioning may not be beneficial and may be harmful.1
    • Nasal suction should be used to help infants with respiratory distress, poor feeding or sleeping.
  • Bronchodilators1,25,26
    • Generally, not recommended for routine use. 
    • May trial in infants with:
      • Severe bronchiolitis (these were excluded in the studies). 
      • History of prior wheezing. 
      • Family history of atopy/asthma in an older infant.
  • Anticholinergic Agents (ipratropium bromide)
    • No evidence for improvement in bronchiolitis.31-34
  • Corticosteroids
    • AAP1, Cochrane Review27, and PECARN28 study all recommend against, finding no evidence for improvement. 
    • One small study (70 patients) found a benefit utilizing 1 mg/kg oral dexamethasone followed by 0.6 mg/kg daily for 5 days. However, the study limited by size and increased prevalence of family history of atopy. 
    • Recommendations remain against use in first time wheezers with bronchiolitis. 
  • Racemic Epinephrine
    • Not recommended1. Further study needed. 
  • Racemic Epinephrine + Oral Dexamethasone
    • Pediatric Emergency Research Canada trial at 8 Canadian pediatric EDs involving 800 infants aged 6 weeks to 12 months with bronchiolitis found that the epinephrine-dexamethasone group had a lower admission rate over 7 days than the placebo group (17.1% vs 26.4%). This was not statistically significant. Further study needed. 30
  • Hypertonic Saline
    • AAP guidelines do not recommend use in the ED but clinicians may utilize it in the inpatient setting. 1
    • Cochrane reviews in 2013 and 2017 found some inpatient benefit, but a conflicting publication found it may worsen cough.35-37 
  • High Flow Nasal Cannula(HFNC)
    • Several small pediatric ICU studies show a benefit in severe cases. No large ED randomized trials exist, to date. 
    • Study protocols included weight based or age-based flow rates.
  • Nasal CPAP
    • Shows benefit in pediatric ICU settings. Evidence vs HFNC is limited. 


  • Consider admission if any of the following are present:
    • Risk for apnea 
    • Risk for severe bronchiolitis 
    • Respiratory distress, particularly if it interferes with feeding 
    • Hypoxia (oxygen saturation ≤ 90%) 
    • Decreased feeding and/or dehydration 
    • An unreliable caregiver (i.e., unable to ensure patient care and appropriate 24-hour follow-up) 
  • All patients with severe bronchiolitis should be admitted. 

Duration of Illness

  • Median duration of illness is 12 days in children <24 months 
  • 18% still ill at 3 weeks.2
  • 9% still ill at 4 weeks.2

Further Reading

Acute Bronchiolitis: Assessment and Management in the Emergency Department (Pharmacology CME) Date Release: Oct 2019 This issue reviews risk factors for apnea and severe bronchiolitis; discusses treatments and therapies such as oxygen supplementation, fluid administration, bronchodilators, corticosteroids, high-flow nasal cannula, and continuous positive airway pressure; and provides evidence-based recommendations for the management of pediatric patients with bronchiolitis.


  1. Ralston SL, Lieberthal AS, Meissner HC, et al. Clinical practice guideline: the diagnosis, management, and prevention of bronchiolitis. Pediatrics. 2014;134(5):e1474-e1502. Full Text
  2. Swingler GH, Hussy GD, Zwarenstein M. Duration of illness in ambulatory children diagnosed with bronchiolitis. Arch Pediatr Adolesc Med. 2000;154(10):997-1000. 
  3. Wright AL, Taussig LM, Ray CG, et al. The Tucson Children’s Respiratory Study, II: lower respiratory tract illness in the first year of life. Am J Epidemiol. 1989;129(6):1232–1246. 
  4. Rakes GP, Arruda E, Ingram JM, et al. Rhinovirus and respiratory syncytial virus in wheezing children requiring emergent care: IgE and eosinophil analyses. Am J Respir Crit Care Med. 1999;159(3):785-790. 
  5. Kahn JS. Epidemiology of Human metapneumovirusClin Microbiol Rev. 2006;19(3):546-557. 
  6. van den Hoogen BG, de Jong JC, Groen JC, et al. A newly discovered human pneumovirus isolated from young children with respiratory tract disease. Nat Med. 2001;7(6):719- 724. 
  7. Jartti T, Lehtinen P, Vuorinen T, et al. Respiratory picornaviruses and respiratory syncytial virus as causative agents of acute expiratory wheezing in children. Emerg Infect Dis. 2004;10(6):1095-1101. 
  8. Caracciolo S, Minini C, Colombrita D, et al. Human metapneumovirus infection in young children hospitalized with acute respiratory tract disease: virologic and clinical features. Pediatr Infect Dis J. 2008;27(5):406-412.
  9. Semple MG, Cowell A, Dove W, et al. Dual infection of infants by Human metapneumovirus and Human respiratory syncytial virus is strongly associated with severe bronchiolitis. J Infect Dis. 2005;191(3):382-386.
  10. Brand HK, Groot RD, Galama J, et al. Infection with multiple viruses is not associated with increased disease severity in children with bronchiolitis. Pediatr Pulmonol. 2012; 47:393–400.
  11. Wang EE, Law BJ, Stephens D. Pediatric Investigators Collaborative Network on Infections in Canada (PICNIC) prospective study of risk factors and outcomes in patients hospitalized with respiratory syncytial viral lower respiratory tract infection. J Pediatr. 1995;126(2):212-219.
  12. Shaw KN, Bell LM, Sherman NH. Outpatient assessment of infants with bronchiolitis. Am J Dis Child. 1991;145(2):151- 155.
  13. Chan PW, Lok FY, Khatijah SB. Risk factors for hypoxemia and respiratory failure in respiratory syncytial virus bronchiolitis. Southeast Asian J Trop Med Public Health. 2002;33(4):806- 810. 
  14. MacDonald NE, Hall CB, Suffin SC, et al. Respiratory syncytial viral infection in infants with congenital heart disease. N Engl J Med. 1982;307(7):397-400. 
  15. Hall CB, Powell KR, MacDonald NE, et al. Respiratory syncytial viral infection in children with compromised immune function. N Engl J Med. 1986;315(2):77-81. 
  16. Kneyber MC, Brandenburg AH, de Groot R, et al. Risk factors for respiratory syncytial virus associated apnoea. Eur J Pediatr. 1998;157(4):331-335. 
  17. Willwerth BM, Harper MB, Greenes DS. Identifying hospitalized infants who have bronchiolitis and are at high risk for apnea. Ann Emerg Med. 2006;48(4):441-447. 
  18. Roosevelt G, Sheehan K, Grupp-Phelan J, et al. Dexamethasone in bronchiolitis: a randomised controlled trial. Lancet. 1996;348(9023):292-295.
  19. Swingler GH, Hussey GD, Zwarenstein M. Randomised controlled trial of clinical outcome after chest radiograph in ambulatory acute lower-respiratory infection in children. Lancet. 1998;351(9100):404-408. 
  20. Schuh S, Lalani A, Allen U, et al. Evaluation of the utility of radiography in acute bronchiolitis. J Pediatr. 2007;150(4):429–433. 
  21. American College of Emergency Physicians Clinical Policies Subcommittee on Pediatric Fever, Mace SE, Gemme SR, et al. Clinical policy for well-appearing infants and children younger than 2 years of age presenting to the emergency department with fever. Ann Emerg Med. 2016;67(5):625-639. 
  22. Levine DA, Platt SL, Dayan PS, et al. Risk of serious bacterial infection in young febrile infants with respiratory syncytial virus infections. Pediatrics. 2004;113(6):1728-1734. 
  23. Purcell K, Fergie J. Concurrent serious bacterial infections in 2396 infants and children hospitalized with respiratory syncytial virus lower respiratory tract infections. Arch Pediatr Adolesc Med. 2002;156:322-324.
  24. McDaniel CE, Ralston S, Lucas B, Schroeder AR. Association of diagnostic criteria with urinary tract infection prevalence in bronchiolitis: a systematic review and meta-analysis. JAMA Pediatr. 2019;173(3):269-277. 
  25. Gadomski AM, Bhasale AL. Bronchodilators for bronchiolitis. Cochrane Database Syst Rev. 2006(3):CD001266.
  26. Chavasse R, Seddon P, Bara A, et al. Short acting beta agonists for recurrent wheeze in children under 2 years of age. Cochrane Database Syst Rev. 2009(2):CD002873.
  27. Patel H, Platt R, Lozano JM, et al. Glucocorticoids for acute viral bronchiolitis in infants and young children. Cochrane Database Syst Rev. 2004(3):CD004878. 
  28. Corneli HM, Zorc JJ, Mahajan P, et al. A multicenter, randomized, controlled trial of dexamethasone for bronchiolitis. N Engl J Med. 2007;357(4):331-339. 
  29. Schuh S, Coates AL, Binnie R, et al. Efficacy of oral dexamethasone in outpatients with acute bronchiolitis. J Pediatr. 2002;140(1):27-32. 
  30. Plint AC, Johnson DW, Patel H, et al. Epinephrine and dexamethasone in children with bronchiolitis. N Engl J Med. 2009;360(20):2079-2089. 
  31. Everard ML, Bara A, Kurian M, et al. Anticholinergic drugs for wheeze in children under age of two years. Cochrane Database Syst Rev. 2005(3):CD001279. 
  32. Goh A, Chay OM, Foo AL, et al. Efficacy of bronchodilators in the treatment of bronchiolitis. Singapore Med J. 1997;38:326-328. 
  33. Chowdhury D, al Howasi M, Khalil M, et al. The role of bronchodilators in the management of bronchiolitis: a clinical trial. Ann Trop Paediatr. 1995;15(1):77-84. 
  34. Wang EE, Milner R, Allen U, et al. Bronchodialtors for treatment of mild bronchiolitis: a factorial randomized trial. Arch Dis Child. 1992;67:289-293. 
  35. Zhang L, Mendoza-Sassi RA, Wainwright C, et al. Nebulised hypertonic saline solution for acute bronchiolitis in infants. Cochrane Database Syst Rev. 2013(7):CD006458. 
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  37. Angoulvant F, Bellettre X, Milcent K, et al. Effect of nebulized hypertonic saline treatment in emergency departments on the hospitalization rate for acute bronchiolitis: a randomized clinical trial. JAMA Pediatr. 2017;171(8):e171333.

Last Updated on January 24, 2023

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