Bronchiolitis (RSV) in Infants: Pathophysiology, Assessment, and Nursing Care

Bronchiolitis is the most common lower respiratory tract infection in infants and a leading cause of hospitalization in children under 12 months. This note reviews the pathophysiology, clinical presentation, and nursing management of RSV bronchiolitis, along with high-yield distinctions from asthma and common exam traps.

Definition

• Bronchiolitis is an acute viral infection of the lower respiratory tract characterized by inflammation and obstruction of the small airways (bronchioles).
• Most commonly caused by respiratory syncytial virus (RSV).
• It is the most common lower respiratory tract infection in infants and young children and a leading cause of hospitalization in children under 12 months of age.

Pathophysiology

• RSV causes necrosis of the respiratory epithelial cells lining the bronchioles, leading to inflammation and edema of the airway walls.
• Inflammation and edema narrow the small airways, increasing airway resistance and work of breathing.
• Increased mucus production creates thick mucus plugs that obstruct the narrowed airways.
• Air trapping occurs with partial obstruction during expiration — the infant cannot fully exhale, leading to hyperinflation.
• Atelectasis develops when airways become completely obstructed, causing ventilation-perfusion (V/Q) mismatch and hypoxemia.

Risk Factors for Severe Bronchiolitis

• Infant factors: prematurity, age <6 months, low birth weight, male sex
• Environmental factors: daycare attendance, crowded living conditions, secondhand smoke exposure
• Medical factors: congenital heart disease, chronic lung disease (BPD), immunodeficiency, neuromuscular disease

Prematurity and age under 6 months are major risk factors because these infants have smaller airways and immature immune systems. Congenital heart disease and chronic lung disease increase the risk of severe RSV infection requiring hospitalization.

Clinical Manifestations

• Upper respiratory symptoms first: rhinorrhea, nasal congestion, mild cough
• Lower respiratory symptoms in 1–3 days: tachypnea, wheezing, crackles, cough
• Retractions: substernal, intercostal, suprasternal
• Nasal flaring: infant dilates nostrils to reduce airway resistance
• Grunting: expiratory sound from exhaling against a partially closed glottis
• Apnea: especially in preterm infants and those under 2 months — a medical emergency
• Feeding difficulty and dehydration from respiratory distress and increased insensible losses
• Cyanosis: late sign of severe hypoxemia requiring immediate intervention

Diagnosis

• History: age, symptoms, sick contacts, risk factors
• Physical exam: respiratory rate, retractions, wheezing, crackles, oxygen saturation
• Pulse oximetry: SpO2 <90% indicates significant hypoxemia
• Nasopharyngeal swab: RSV testing by PCR or antigen
• Chest X-ray: may show hyperinflation, atelectasis, or peribronchial thickening — not always required

Bronchiolitis vs. Asthma

• Age: bronchiolitis in infants <12 months; asthma typically in children >2 years
• Cause: bronchiolitis is viral (RSV); asthma is allergic/inflammatory and trigger-based
• Course: bronchiolitis is self-limited; asthma is chronic and reversible with treatment
• Episodes: bronchiolitis is usually a single episode; asthma is recurrent
• Bronchodilator response: variable in bronchiolitis; usually positive in asthma

Management

• Supportive care is the mainstay. Most infants can be managed at home.
• Oxygen therapy for hypoxemia — maintain SpO2 above 90%.
• Nasal suctioning with bulb suction or suction catheter to clear secretions.
• Hydration: small, frequent feeds; IV fluids if unable to feed.
• Positioning: upright with head of bed elevated to facilitate breathing.
• Bronchodilators (albuterol, nebulized epinephrine): response is variable.
• Corticosteroids: not recommended for routine use — do not improve outcomes.
• Antivirals (ribavirin): rarely used; reserved for severe cases in immunocompromised patients.
• Antibiotics: not indicated unless bacterial superinfection is present.
• Advanced respiratory support: CPAP or mechanical ventilation for severe respiratory failure.

Prevention of RSV

• Palivizumab (Synagis): monoclonal antibody for RSV prophylaxis, given monthly during RSV season.
• Indications: prematurity (<35 weeks), chronic lung disease (BPD), congenital heart disease, neuromuscular disease.
• Hand hygiene is the single most important measure to prevent RSV transmission.
• Contact precautions (gloves and gowns) for hospitalized infants with RSV.
• Avoid sick contacts and secondhand smoke exposure.
• Breastfeeding reduces risk of RSV infection through passive immunity.

Nursing Interventions

• Assess respiratory status frequently: respiratory rate, SpO2, retractions, work of breathing.
• Monitor for signs of worsening: increased retractions, apnea, cyanosis.
• Suction nasal passages before feeding and as needed to improve breathing and intake.
• Provide small, frequent feeds to prevent fatigue and dehydration.
• Position infant upright to facilitate breathing.
• Monitor intake and output to ensure adequate hydration.
• Provide parent education on disease course, home care, and signs of worsening.

Exam Traps

• Do not use corticosteroids routinely for bronchiolitis — they are not effective.
• Do not use antibiotics unless bacterial superinfection is present.
• Do not ignore apnea — it is a medical emergency, especially in preterm infants.
• Do not confuse bronchiolitis (infants) with asthma (older children).
• Do not give palivizumab to all infants — it is reserved for high-risk infants.
• Do not discharge an infant with significant respiratory distress or poor feeding.

Key takeaways

• RSV is the leading cause of bronchiolitis and hospitalization in infants <12 months; pathology involves airway inflammation, mucus plugging, air trapping, and atelectasis.
• Management is supportive: oxygen to keep SpO2 >90%, nasal suctioning, hydration, and upright positioning — not routine steroids, antibiotics, or bronchodilators.
• Apnea in young or preterm infants with RSV is a medical emergency.
• Palivizumab prophylaxis is reserved for high-risk infants (prematurity, BPD, CHD, neuromuscular disease) monthly during RSV season.
• Hand hygiene and breastfeeding are the most important preventive measures against RSV.
• Distinguish bronchiolitis (infants, viral, usually single episode) from asthma (older children, recurrent, bronchodilator-responsive).