Bronchiolitis

Bronchiolitis Basics - Wheezy Wee Ones

• Acute viral Lower Respiratory Tract Infection (LRTI) of small airways (bronchioles).
• Primarily affects infants < 2 years; peak incidence 2-6 months.
• Clinical features: Coryza, cough, tachypnea, expiratory wheeze, crackles, respiratory distress.
• Most common cause: Respiratory Syncytial Virus (RSV) - accounts for ~70-80% of cases.
• Other viral culprits: Rhinovirus, Parainfluenza, Adenovirus, Human Metapneumovirus (hMPV).
• Seasonal pattern: Predominantly occurs during winter and early spring.

⭐ RSV is the leading cause of bronchiolitis and pneumonia in infants worldwide.

Pathophysiology & Risk Factors - Tiny Tube Trouble

• Pathophysiology: Viral infection (RSV predominant) inflames bronchioles. Leads to epithelial necrosis, edema, ↑mucus & debris. Causes airway narrowing/obstruction, air trapping, atelectasis, V/Q mismatch.

• Risk Factors:
  • Age <6 months (peak 2-6 months)
  • Prematurity (<37 weeks), Low Birth Weight (LBW)
  • Chronic Lung Disease (e.g., BPD)
  • Congenital Heart Disease (hemodynamically significant)
  • Immunodeficiency
  • Environmental: Passive smoking, Daycare, Crowding
  • 📌 Prematurity, Age <6m, Chronic conditions (lung/heart), Environmental (smoke/daycare) = PACE

⭐ RSV is the most common cause (>50% of cases), particularly during winter outbreaks.

Clinical Features & Severity - Coughs & Cries

• Initial Phase (1-3 days): Coryza, mild cough, low-grade fever.

• Progressive Phase (LRTI):

  • Worsening paroxysmal cough, often with post-tussive emesis.
  • Tachypnea (typically >50-60/min).
  • Auscultation: Diffuse bilateral wheezes (often polyphonic, expiratory > inspiratory), fine inspiratory crackles.
  • Increased Work of Breathing (WOB): Nasal flaring, expiratory grunting, intercostal/subcostal/suprasternal retractions.
  • Feeding difficulties, dehydration risk, irritability.
  • Apneic episodes: Significant risk in young infants (<2 months, esp. <6 weeks) and premature babies.

• Severity Classification:

> ⭐ Apnea may be the *sole* presenting feature in very young infants (<**2** months), especially those born prematurely.

Diagnosis & Differentials - Clinical Clues

• Age < 2 yrs (peak 3-6 mo).
• Viral prodrome (coryza, cough) → resp. distress (tachypnea, retractions, nasal flaring).
• Auscultation: Diffuse wheeze & fine inspiratory crackles.
• Low-grade fever; apnea risk in young/premature infants.
• Differentials:
  • Asthma: Recurrent, older age, good bronchodilator response.
  • Pneumonia: High fever, focal chest signs.
  • Foreign Body Aspiration (FBA): Sudden onset, unilateral findings.
  • Pertussis: Paroxysmal cough, inspiratory whoop.

⭐ First episode of wheezing in a child < 2 years, especially < 12 months, is highly suggestive, particularly during RSV season.

Management & Prevention - Supportive Steps

• Goals: Oxygenation (SpO2 >90-92%), hydration.
• Oxygen: Humidified if SpO2 < 90-92%.
• Fluids: Oral preferred. IV if poor intake, dehydration, or ↑WOB (work of breathing).
• Nasal Suction: Gentle, pre-feeds; saline drops PRN.
• Fever: Paracetamol if >38.5°C or distress.
• Monitor: Respiratory status (RR, effort, SpO2), hydration, feeding.

⭐ Routine bronchodilators, corticosteroids, or antibiotics are NOT recommended in typical bronchiolitis; they lack proven clinical benefit.

• Prevention:
  • Hand hygiene, avoid smoke exposure.
  • Breastfeeding.
  • Palivizumab for high-risk infants (prematurity <29wks, CLD, significant CHD).

High-Yield Points - ⚡ Biggest Takeaways

• RSV is the most common cause, primarily affecting infants < 2 years old.
• Characterized by viral prodrome followed by wheezing, cough, and respiratory distress.
• Diagnosis is mainly clinical; CXR may show hyperinflation and atelectasis.
• Treatment is supportive: oxygen, hydration, and nasal suctioning.
• Bronchodilators and steroids are not routinely recommended.
• Palivizumab for prophylaxis in high-risk infants (e.g., prematurity, CLD).
• Watch for apnea, especially in young infants or those born prematurely.