Bronchiolitis

Bronchiolitis is a lower respiratory tract infection (LRTI) characterized by inflammation of the bronchioles in children < 2 years of age. Respiratory syncytial virus (RSV) is the primary pathogen, although many viruses have been implicated in bronchiolitis. Patients first present with upper respiratory tract infection (URTI) symptoms (e.g., low-grade fever, nasal congestion) followed by a cough, wheezing, and, in severe cases, signs of acute respiratory distress. Bronchiolitis is a clinical diagnosis; diagnostic studies are usually not needed unless the child presents with severe illness that requires an evaluation for associated complications (e.g., superinfection, respiratory acidosis) or if the diagnosis is uncertain. Management consists of supportive treatment (e.g., nasal suction) and close monitoring. Severe illness requires hospitalization for additional management (e.g., IV fluids, respiratory support, nutritional support) and close monitoring of respiratory status. Bronchiolitis prevention includes RSV vaccination of pregnant individuals in the third trimester and routine passive immunization of all infants < 8 months of age with RSV monoclonal antibodies.

• Primarily affects children < 2 years of age
• Peak incidence: 2–6 months of age
• Common during winter months

Epidemiological data refers to the US, unless otherwise specified.

• Most common: respiratory syncytial virus (RSV), a paramyxovirus
• Less common
  • Parainfluenza virus
  • Influenza virus
  • Adenovirus
  • Rhinovirus
  • Coronavirus
  • Metapneumovirus
• Risk factors for severe bronchiolitis ^[1][2]
  • Age < 12 weeks
  • Preterm birth (< 34 weeks' gestational age)
  • Congenital heart or lung disease
  • Neurological disease
  • Immunodeficiency
  • Exposure to tobacco smoke ^[3]

• Initially, URTI symptoms (e.g., copious rhinorrhea, low-grade fever, cough) ^[1][4]
• Followed by LRTI symptoms ^[1][4]
  • Crackles, wheezes; , and/or rhonchi on auscultation ^[4]
  • Findings vary minute-to-minute as mucus is cleared and/or respiratory efforts change.
  • Severe illness: respiratory distress (usually occurs in children < 1 year of age)
    • Tachypnea or apnea
    • Prolonged expiration
    • Nasal flaring
    • Intercostal retractions
    • Cyanosis
• Often associated with poor feeding ^[5]

If significant nasal congestion is present, provide nasal suction and reassess respiratory status to differentiate upper airway involvement (clear breath sounds after nasal suction) from lower airway involvement (abnormal breath sounds after nasal suction). ^[4]

Symptoms typically peak 3–5 days after onset and then gradually improve over 2–3 weeks. The onset of new symptoms or worsening of existing symptoms (e.g., fever) after 3–5 days should raise concern for complications of bronchiolitis. ^[1][4]

General principles ^[1][6]

• Bronchiolitis is a clinical diagnosis based on the patient's age (< 2 years) and the presence of classic clinical features of bronchiolitis.
• Further testing is not usually required but may be considered in patients with:
  • Severe disease, e.g., if there is concern for respiratory failure
  • Suspected complications of bronchiolitis
  • Diagnostic uncertainty to rule out differential diagnoses of bronchiolitis

Laboratory studies ^[1][4]

• Blood gas ^[7]
  • Indicated for worsening severe disease and/or impending respiratory failure
  • May show hypoxemia and/or CO₂ retention
• Respiratory viral panel
  • Indications
    • Hospitalized infants receiving palivizumab prophylaxis
    • Consider if patient cohorting is planned.
  • Findings ^[1]
    • 60–75% are positive for RSV
    • Coinfections are present in up to one-third of those tested
• Studies to exclude differential diagnoses (not routinely recommended)
  • Blood culture
  • Urinalysis and urine culture ^[8]
  • CBC and BMP

Chest x-ray

• Indications: severe disease if there is diagnostic uncertainty or suspected complications (e.g., pneumothorax, pneumonia)
• Potential findings
  • Normal
  • Nonspecific findings, e.g., peribronchial thickening, hyperinflation of the lungs, interstitial infiltrates, atelectasis
  • Superimposed complications, e.g., pneumonia

Approach ^[1][9]

• Determine the need for immediate respiratory support.
  • Hypoxemia (i.e., O₂ ≤ 90% on room air): oxygen therapy via nasal cannula
  • Refractory hypoxemia, signs of respiratory distress, respiratory failure: intubation, CPAP, or high-flow nasal cannula
• Start supportive measures including adequate hydration, relief of nasal congestion and/or obstruction, and monitoring.
• Screen for admission criteria for bronchiolitis and initiate inpatient management of bronchiolitis if present.
• Provide outpatient management of bronchiolitis with close medical follow-up for patients who do not meet the admission criteria.

Children with bronchiolitis and oxygen saturation ≥ 90% do not require supplemental oxygen. ^[1][6]

Avoid bronchodilators, epinephrine, corticosteroids, antibiotics, and chest physiotherapy unless there are comorbidities (e.g., asthma, croup, cystic fibrosis, acute otitis media). ^[1]

Admission criteria for bronchiolitis ^[1][9][10]

• Unwell appearance, lethargy
• Moderate to severe signs of respiratory distress (including significantly elevated respiratory rate for age)
• Ongoing respiratory support required
• Need for supplemental hydration
• History of apnea
• Consider if:
  • Risk factors for severe bronchiolitis are present
  • Supportive care at home is not feasible ^[10]

Inpatient management of bronchiolitis ^[1][9]

Respiratory support

• Frequently monitor routine vital signs including O₂ saturation; consider using:
  • Continuous pulse oximetry ^[1]
  • An objective respiratory score ^[11]
• Adjust short-term oxygen therapy as needed.
• Provide regular external nasal suction. ^[1]
• Consider scheduled nebulizations with 3% hypertonic saline ^[1][12]

Hypertonic saline nebulizations may trigger bronchospasm. Discontinue treatment if nebulizations cause severe coughing fits and/or worsen the patient's respiratory status. ^[12]

Caloric and fluid support

• Ensure patients receive the recommended daily intake for their age.
• Encourage normal oral feeds (e.g., with breastmilk, formula, regular diet for age) as tolerated.
• Consider NG/IV fluids for any of the following: ^[1]
  • Poor oral intake
  • Respiratory rate consistently > 60–70 bpm
  • Worsening respiratory status during feeds
  • Symptoms of aspiration

Respiratory distress increases caloric and fluid requirements but also increases the risk for aspiration during oral feeds. Nutritional and fluid support via a feeding tube (orogastric or nasogastric) and/or intravenously is often necessary. ^[1]

Other recommendations

• Start isolation precautions in accordance with local protocols (e.g., contact precautions for RSV). ^[13]
• If used, discontinue palivizumab prophylaxis. ^[1]

Outpatient management of bronchiolitis ^[1][9]

• Arrange follow-up within 24 hours. ^[14]
• Educate caregivers on:
  • Signs of deterioration and the need to seek immediate medical attention if present ^[14]
  • How and when to provide nasal suction
  • The expected course of disease
• Encourage adequate oral caloric and fluid intake.
• Advise caregivers to avoid exposing the patient to second-hand smoke; offer counseling on smoking cessation for household members.

Advise caregivers to seek immediate medical attention if the child shows signs of deterioration such as dehydration, poor feeding, lethargy or irritation, new fever, and/or signs of respiratory distress. ^[14]

• No URTI symptoms
  • Congenital heart disease
  • Foreign body aspiration
  • Congenital airway abnormalities (e.g., vascular ring)
• Wheeze
  • Polyphonic
    • Asthma
    • Congestive heart failure secondary to congenital heart disease ^[9]
  • Monophonic: foreign body aspiration
  • See also “Wheezing in children”.
• Asymmetric crackles: bacterial or viral pneumonia
• Cough
  • Pneumonia
  • Pertussis
  • See also “Differential diagnosis of acute cough” and “Bronchitis.”
• Neonatal fever: neonatal sepsis

The differential diagnoses listed here are not exhaustive.

• Apnea
• Respiratory failure
• Pneumonia
• Dehydration
• Otitis media

We list the most important complications. The selection is not exhaustive.

• With timely diagnosis and adequate treatment, the prognosis is good.
• Bronchiolitis in infancy is associated with an increased risk of developing asthma.

General measures ^[1][2][6]

• Vaccinate pregnant individuals against RSV at 32–36 weeks' gestation. ^[15]
• Encourage exclusive breastfeeding for the first 6 months of life.
• Educate caregivers on respiratory hygiene and hand hygiene.
• Advise avoiding large crowds.
• Inform caregivers about the increased risk of infection at daycare.
• Offer advice on smoking cessation to any individuals who smoke in the household to reduce tobacco smoke exposure.

Administration of respiratory syncytial virus vaccine to pregnant individuals minimizes the risk of bronchiolitis in infants. ^[15]

RSV prophylaxis ^[2][16][17]

• Monoclonal antibodies that target the RSV fusion (F) protein are used to provide passive immunization.
• RSV prophylaxis reduces RSV-related hospitalizations (e.g., due to bronchiolitis, pneumonia) in infants.
• Two RSV monoclonal antibodies are now available.
  • Nirsevimab (preferred)
    • A long-acting RSV monoclonal antibody that provides protection for 5 months
    • Administered as a single intramuscular injection during or, preferably, just before RSV season
  • Palivizumab (alternative) ^[1][2]
    • A short-acting RSV monoclonal antibody
    • Administered as monthly intramuscular injections
    • Initiate administration just before and continue throughout the RSV season. ^[2]
    • In children with RSV-related hospitalization, discontinue for the remainder of the current RSV season. ^[2]

If available, nirsevimab is preferred over palivizumab because it can be administered as a single dose rather than monthly dosing. ^[16]

Palivizumab and nirsevimab provide RSV (Paramyxovirus) Prophylaxis for Preexisting conditions (e.g., Preterm).

RSV prophylaxis can be administered at the same visit as other age-appropriate vaccines. ^[16]

• One-Minute Telegram 70-2023-1/3: The efficacy of the RSV vaccine is nothing to sneeze at

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