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Bronchiolitis is the most common lower respiratory tract infection that affects children in the first two years of life and the most common reason for hospitalization in this age group.1

More than one-third of children develop bronchiolitis between birth and age 2 years, and the cost of hospitalization is more than $500 million annually.2-4

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In most cases, the disease responds well to home care. Risk factors include exposure to cigarette smoke, age younger than 6 months, crowded living conditions, not being breastfead, and premature birth (before 37 weeks’ gestation).

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Bronchiolitis, a disease of the lung’s smallest airways (bronchioles) usually caused by a viral infection, generally occurs in a seasonal pattern over the winter months. More than 50% of cases result from respiratory syncytial virus (RSV.) Other causes include parainfluenza, adenovirus, human metapneumovirus, and influenza.

The pathophysiology of bronchiolitis results from the infection of epithelial cells in the respiratory tract. This infection leads to inflammation, edema, mucus production, bronchospasm, and necrosis of the respiratory tract’s epithelial lining. Because the bronchioles are so small in infants, they may easily become blocked, causing respiratory distress.

Clinical assessment

Bronchiolitis is diagnosed clinically based on history and physical examination.5 The disease can be recognized from clinical signs and symptoms, starting with several days of upper respiratory symptoms of mild rhinorrhea, cough, and fever followed by tachypnea, wheezing and increased respiratory effort. Physical examination should include respiratory rate and such evidence of increased work of breathing as retractions, nasal flaring, and grunting. Auscultation will typically reveal wheezes or inspiratory crackles as a result of inflammation and epithelial debris in the airway.

Assessment of disease severity in an otherwise previously healthy infant aged 60 days or older should be based on the history and physical examination (Table 1).

There are several features of the history and physical that must be considered when determining severity. One key is evaluation of the respiratory rate; for an accurate measurement, count the respiratory rate for one full minute rather than estimating by counting for a partial minute.6 In addition, nasal suctioning may be required prior to counting, as the respiratory rate may be increased due to obstruction. Tachypnea (i.e., respiratory rate >70 breaths per minute) may be associated with risk for severe disease and may warrant additional evaluation for pneumonia or other lower respiratory tract infection.6

Radiologic and laboratory testing

It is not necessary to use radiologic or laboratory testing in the diagnosis of bronchiolitis.2,7 Ask yourself, “Will the result of the test change my clinical management?” When a child has the classic presentation of disease, chest x-ray, viral testing and blood work is not required. Generally, children with bronchiolitis will have hyperinflation, atelectasis, and infiltrates on chest radiograph. However, the findings typically do not correlate with disease severity and are not useful in determining treatment of predicting the clinical course.8

Because risk of serious bacterial infection in children aged 60 days or older is low, additional laboratory testing in these patients is not indicated.9 In those younger than age 60 days, the question of serious bacterial illness in febrile infants becomes more complicated. In such cases, urinary tract infection is the most commonly reported serious bacterial infection. Many clinicians may screen children in this age group in accordance with suggested guidelines for febrile infants.10


Children with uncomplicated bronchiolitis may be appropriately managed with supportive care (Table 2). No pharmacologic therapies for acute bronchiolitis have been shown to change the natural progression of the disease. Many pharmacologic treatments have been studied, including bronchodilators, corticosteroids, antibiotics, and antivirals, but no significant evidence of efficacy has been found.