Bronchiolitis

Bronchiolitis is an inflammation of the small airways in the lungs, primarily caused by viral infections such as the respiratory syncytial virus (RSV) and human rhinovirus.

It predominantly affects children under two years of age and can present with a range of respiratory symptoms including fever, cough, runny nose, wheezing, and breathing difficulties.

Severe cases may feature nasal flaring, grunting, and intercostal retractions. Dehydration and shortness of breath are common complications, especially if the child is unable to feed properly.

Signs and Symptoms

Bronchiolitis typically presents with fever, rhinorrhea, cough, wheezing, and tachypnea, often progressing over one to three days. Auscultation may reveal crackles or wheezes. Severe cases can lead to increased work of breathing, hypoxia, cyanosis, lethargy, decreased activity, and poor feeding. Apnoea may also occur, particularly in very young infants.

Some signs of severe disease include:

• Use of accessory muscles of respiration
• Severe chest wall recession (Hoover's sign)
• Nasal flaring and/or grunting
• Hypoxia (low oxygen levels)
• Cyanosis (bluish skin)
• Poor feeding and lethargy

Causes and Risk Factors

Bronchiolitis is most commonly caused by RSV, but other pathogens like human metapneumovirus, influenza, parainfluenza, coronavirus, adenovirus, and rhinovirus can also be responsible. Risk factors for severe disease include prematurity, congenital heart disease, chronic lung disease, immunodeficiency, neurological disorders, and tobacco smoke exposure.

Diagnosis

Diagnosis is typically clinical, based on history and physical examination. Chest X-rays and viral testing are not routinely required but may be useful in certain scenarios, such as excluding bacterial pneumonia or in cases of severe respiratory distress.

Differential diagnoses include asthma, pneumonia, congenital heart disease, heart failure, allergic reactions, cystic fibrosis, chronic pulmonary disease, foreign body aspiration, and vascular ring.

Prevention

Preventative measures focus on reducing viral transmission through handwashing and avoiding exposure to symptomatic individuals. Breastfeeding is recommended to boost the infant's immune system. RSV vaccines and monoclonal antibodies like Nirsevimab and Palivizumab are used in high-risk groups.

Management

Management is supportive, focusing on hydration and symptom relief. Most cases resolve within 13 days, with 90% clearing up in three weeks. Hospitalisation may be required for severe symptoms, poor feeding, or dehydration. Oxygen therapy is indicated for hypoxia, but evidence does not support routine use of bronchodilators, steroids, or antibiotics. Nebulized hypertonic saline may be beneficial in hospitalised children, although its use in emergency settings remains debated.

Fluid Therapy

Fluid therapy is essential for dehydrated children or those unable to feed orally. Both intravenous and enteral tube feeding are used, with no clear evidence favouring one over the other.

Oxygen Therapy

Oxygen is administered to maintain adequate tissue oxygenation, although the exact levels dictating its use can vary. High-flow nasal cannula therapy may reduce the need for intubation in severe cases.

Hypertonic Saline and Bronchodilators

Nebulized hypertonic saline is somewhat beneficial for hospitalised children but not recommended for emergency department use. Bronchodilators and nebulized epinephrine are generally not recommended due to lack of efficacy and potential side effects.

Other Treatments

Chest physiotherapy, suctioning, heliox, and surfactant therapy have limited roles and are not routinely recommended. Antibiotics, antivirals, corticosteroids, leukotriene inhibitors, and immunoglobulins are generally ineffective and not advised.

Epidemiology

Bronchiolitis peaks during autumn and winter, affecting a significant proportion of infants and young children. It is the leading cause of hospitalisation for respiratory disease in infants in the United States and accounts for a substantial number of primary care and emergency department visits worldwide.

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Self-assessment MCQs (single best answer)

What is the primary cause of bronchiolitis in children under two years of age?

Which of the following is NOT a typical symptom of bronchiolitis?

What is a common sign of severe bronchiolitis?

Which pathogen is NOT commonly associated with bronchiolitis?

What is the primary method of diagnosing bronchiolitis?

Which of the following is NOT recommended as a routine treatment for bronchiolitis?

What is a key preventative measure for bronchiolitis?

Which treatment is essential for dehydrated children with bronchiolitis?

During which seasons does bronchiolitis most commonly peak?

What is the typical duration for most cases of bronchiolitis to resolve?