Introduction
Bronchiolitis is a common lower respiratory tract illness, primarily affecting infants and young children under two. Inflammation and congestion of the bronchioles lead to breathing difficulties. Respiratory Syncytial Virus (RSV) is the most frequent cause, though other viruses like adenovirus and influenza may also contribute. While many cases resolve on their own, severe symptoms can occur in high-risk groups, such as premature infants or those with underlying health conditions.
Etiology and Risk Factors
The primary cause of bronchiolitis is viral infection, particularly:
- RSV: Responsible for 50–80% of bronchiolitis cases, peaking during winter and early spring.
- Other viruses: Parainfluenza, rhinovirus, adenovirus, influenza, and human metapneumovirus.
Risk Factors for Severe Bronchiolitis:
- Premature birth (before 37 weeks).
- Age: Infants under six months are at greater risk.
- Lung or heart conditions: Congenital heart disease or bronchopulmonary dysplasia increases risk.
- Immunodeficiency: Compromised immune systems.
- Environmental exposure: Tobacco smoke and crowded living spaces.
Physiopathology
Bronchiolitis causes inflammation, oedema, and mucus production in the bronchioles, leading to:
- Airway narrowing: Causes hyperinflation of the lungs.
- Impaired gas exchange: May result in hypoxaemia and hypercapnia in severe cases.
- Atelectasis: Mucus blockage can cause small lung collapses.
Clinical Presentation
Symptoms often begin with upper respiratory signs, such as:
- Nasal discharge (rhinorrhea).
- Cough.
- Low-grade fever.
Progression to lower respiratory tract symptoms occurs over 3-5 days, including:
- Tachypnea (rapid breathing).
- Crackles or wheezing.
- Signs of respiratory distress: Retractions, nasal flaring, and accessory muscle use.
- Apnea: Particularly in premature infants.
- Feeding difficulties and dehydration due to exhaustion.
Diagnosis
Bronchiolitis is typically diagnosed based on history and physical exam findings, such as:
- URTI progressing to cough and respiratory distress.
- Tachypnea, wheezing, and crackles upon examination.
Tests are usually unnecessary, but severe cases may require:
- Viral testing: RSV detection via PCR or antigen tests.
- Chest X-ray: To rule out other conditions in severe cases.
- Pulse oximetry: To assess oxygen levels.
Complications
- Dehydration: Due to feeding difficulties.
- Respiratory failure: In severe cases, requiring mechanical ventilation.
- Hypoxaemia: Particularly in those with pre-existing lung conditions.
- Recurrent wheezing or asthma: Severe bronchiolitis may increase the risk of future respiratory problems.
Management and Treatment
Treatment is primarily supportive, focusing on maintaining hydration and oxygenation:
- Hydration: Oral fluids or intravenous fluids if necessary.
- Oxygen therapy: For oxygen saturation below 90–92%.
- Nasal suctioning: To clear mucus.
Medications:
- Bronchodilators: Not routinely recommended but may be tried in cases of severe wheezing.
- Corticosteroids: Generally not effective in altering bronchiolitis outcomes.
- Antibiotics: Only used if secondary bacterial infection is suspected.
In severe cases:
- CPAP or High-Flow Nasal Cannula (HFNC): For respiratory support.
- Mechanical ventilation: In cases of respiratory failure.
Prevention
Preventative measures focus on reducing the spread of viruses:
- Hand hygiene: Frequent washing or use of hand sanitiser.
- Avoiding exposure: Limiting contact with sick individuals during RSV season.
- Breastfeeding: Provides passive immunity and may reduce illness severity.
- Palivizumab: Monthly injections for high-risk infants during RSV season.
Prognosis
- Most children recover in 7–10 days, though a cough may persist.
- Healthy children usually recover well, with few needing hospitalisation.
- High-risk infants may experience complications or long-term respiratory issues.
Conclusion
Bronchiolitis is a common viral illness in young children, typically resolving with supportive care. However, in high-risk groups, it can lead to serious complications like respiratory failure. Early recognition and appropriate management are crucial for reducing morbidity and preventing long-term respiratory issues.
