Bronchiolitis in Pediatrics: A Clinical Algorithm
PATHOPHYSIOLOGY: Current Understanding
The pathophysiologic cascade begins with viral infection—most commonly respiratory syncytial virus (RSV)—causing acute inflammation, edema, and necrosis of epithelial cells lining the small airways, combined with increased mucus production and bronchospasm. 1
Cellular and Molecular Mechanisms
Viral invasion targets the bronchiolar epithelium, leading to direct cytopathic effects that destroy ciliated epithelial cells and disrupt the mucociliary clearance mechanism 1, 2
The inflammatory response triggers release of inflammatory mediators including cytokines and chemokines, which recruit neutrophils and lymphocytes to the small airways, perpetuating the inflammatory cascade 2
Airway obstruction results from three simultaneous processes: (1) epithelial cell necrosis and sloughing creating cellular debris, (2) submucosal edema narrowing the airway lumen, and (3) excessive mucus production that plugs the already compromised airways 1, 2
Bronchospasm contributes variably to airway obstruction, though this is less prominent than the inflammatory and obstructive components, explaining why bronchodilators are largely ineffective 1
Air trapping occurs distally to obstructed bronchioles, creating the characteristic hyperinflation seen on physical examination and chest radiographs 2
Ventilation-perfusion mismatch develops as poorly ventilated alveolar units continue to be perfused, leading to hypoxemia that may be disproportionate to the degree of respiratory distress 1
DIAGNOSTIC ALGORITHM
Step 1: Clinical Diagnosis (History and Physical Examination ONLY)
Bronchiolitis is a clinical diagnosis based on history and physical examination alone—routine testing such as chest radiographs, viral testing, or laboratory studies should NOT be ordered. 1, 2
Essential Diagnostic Criteria (All Must Be Present):
Age: 1-24 months (AAP guidelines specifically define this age range) 2
Prodrome of upper respiratory symptoms lasting 2-4 days: rhinorrhea, congestion, low-grade fever 1, 3
Progression to lower respiratory tract symptoms: tachypnea, wheezing, crackles, increased work of breathing 1, 2
First episode of wheezing in this age group (distinguishes from asthma) 4
Physical Examination Findings:
Respiratory rate: Count over a full minute; tachypnea ≥70 breaths/minute indicates increased severity 5
Work of breathing: Nasal flaring, grunting, intercostal/subcostal retractions, use of accessory muscles 5
Auscultation: Bilateral wheezing and/or crackles, prolonged expiratory phase 1, 2
Signs of air trapping: Hyperinflation with increased anteroposterior chest diameter 2
Step 2: Risk Stratification (Identify High-Risk Patients)
Infants <12 weeks require particularly close monitoring due to higher risk of apnea and severe disease. 1, 2
High-Risk Categories Requiring Enhanced Monitoring:
Age <12 weeks (especially <6 weeks): Higher risk of apnea and severe disease 1, 2, 6
Hemodynamically significant congenital heart disease 2, 5, 3
Neuromuscular disease affecting respiratory function 2
Step 3: Determine Disposition (Outpatient vs. Admission)
Admission Criteria:
Respiratory rate >70 breaths/minute with significant work of breathing 5
Inability to maintain adequate oral intake due to respiratory compromise 1, 5
Any high-risk category listed above with moderate symptoms 5
Apnea episodes (particularly in infants <12 weeks) 2
Dehydration or poor feeding 5
MANAGEMENT ALGORITHM
WHAT TO DO: Evidence-Based Supportive Care
The cornerstone of bronchiolitis management is supportive care alone—routine pharmacologic interventions should be avoided. 1
1. Oxygen Therapy (ONLY When Indicated)
Administer supplemental oxygen ONLY if SpO2 persistently falls below 90% 1, 5
Discontinue oxygen when: SpO2 ≥90% on room air, infant feeding well, minimal respiratory distress 5
Avoid continuous pulse oximetry in stable infants—it leads to less careful clinical assessment and unnecessary interventions for transient desaturations that occur in healthy infants 5
2. Hydration Management
Continue oral feeding if infant feeds well without respiratory compromise 1, 5
When respiratory rate exceeds 60-70 breaths/minute: Feeding becomes compromised and aspiration risk increases—consider IV or nasogastric fluids 5
Use isotonic fluids if IV hydration needed: Infants with bronchiolitis may develop SIADH and are at risk for hyponatremia with hypotonic fluids 5
Monitor for SIADH: Adjust fluid management carefully as inappropriate ADH secretion is common 5
3. Airway Clearance
Gentle nasal suctioning may provide temporary relief before feeding or when nasal obstruction is significant 1, 5
Avoid deep suctioning: Associated with longer hospital stays in infants 2-12 months 5
Do NOT perform chest physiotherapy: No evidence of benefit 1, 5
WHAT NOT TO DO: Common Errors in Practice
1. Bronchodilators (Albuterol, Epinephrine)
Bronchodilators should NOT be used routinely for infants with bronchiolitis—they lack evidence of benefit. 1, 5
Why they don't work: The pathophysiology is primarily inflammatory edema and mucus plugging, not bronchospasm 1
If a trial is attempted (not recommended): Must document objective clinical improvement (decreased respiratory rate, improved work of breathing) to continue; discontinue if no response 5
Common pitfall: Continuing bronchodilators despite lack of response because "it might help" 5
2. Corticosteroids
Corticosteroids should NOT be used routinely—meta-analyses show no significant benefit in length of stay or clinical scores. 5, 7
Why they don't work: The inflammatory process in bronchiolitis is not steroid-responsive like asthma 5
Common pitfall: Prescribing steroids because of wheezing, mistaking bronchiolitis for asthma 2
3. Antibiotics
Antibacterial medications should ONLY be used with specific indications of bacterial coinfection. 5
Risk of serious bacterial infection in febrile infants with bronchiolitis is <1% 5
Fever alone does NOT justify antibiotics 5
Specific indications for antibiotics: Documented acute otitis media, confirmed bacterial pneumonia with consolidation, positive blood/urine cultures 5
Common pitfall: Prescribing antibiotics for infiltrates on chest X-ray—approximately 25% of hospitalized infants have radiographic atelectasis or infiltrates that are viral, not bacterial 5
4. Diagnostic Testing
Do NOT routinely order chest radiographs, viral testing, or laboratory studies. 1, 2, 5
Chest X-rays should be reserved for: Consideration of intubation, unexpected clinical deterioration, or suspected underlying cardiac/pulmonary disorder 2
Viral testing does NOT change management and should only be used for cohorting/infection control purposes 2
Common pitfall: Ordering chest X-rays "to rule out pneumonia"—this leads to overdiagnosis of bacterial infection and unnecessary antibiotics 5
5. Hypertonic Saline
Nebulized hypertonic saline is NOT recommended despite some older studies suggesting benefit—more recent evidence shows no significant improvement 7
6. Ribavirin
Ribavirin should NOT be used routinely—may be considered only in highly selected situations such as documented RSV with severe disease in immunocompromised patients 5
CLINICAL MONITORING ALGORITHM
For Admitted Patients:
Serial Clinical Assessments (More Important Than Continuous Monitoring):
Respiratory rate every 4 hours (count for full minute) 5
Work of breathing assessment: Retractions, nasal flaring, grunting 5
Feeding tolerance: Ability to take oral fluids without respiratory compromise 5
Intermittent SpO2 checks rather than continuous monitoring in stable patients 5
Red Flags Requiring Escalation:
Apnea episodes (especially in infants <12 weeks) 2
Persistent SpO2 <90% despite supplemental oxygen 1
Worsening work of breathing despite supportive care 5
Inability to maintain hydration 5
Mental status changes: Lethargy, irritability beyond baseline 4
DISCHARGE CRITERIA
Discharge readiness requires ALL of the following: 1
SpO2 ≥90% on room air for at least 12-24 hours 1
Feeding well without respiratory compromise (taking adequate oral fluids) 1
Minimal respiratory distress: Respiratory rate normalizing for age, minimal retractions 1
Reliable follow-up arranged within 24-48 hours 1
Parents educated on warning signs: Increased work of breathing, poor feeding, lethargy, apnea 1
PREVENTION STRATEGIES
For All Families:
Exclusive breastfeeding reduces hospitalization risk by 72% 1, 4
Avoid tobacco smoke exposure: Significantly increases severity and hospitalization risk 1, 5
Hand hygiene: Most important infection control measure 1
Limit visitor exposure during respiratory virus season (typically November-March) 1
RSV Prophylaxis (Palivizumab):
Palivizumab is recommended for high-risk infants in monthly doses during RSV season: 1, 3
Infants with chronic lung disease of prematurity requiring medical support 1, 3
Infants with hemodynamically significant congenital heart disease 1, 3
PROGNOSIS AND LONG-TERM CONSIDERATIONS
Most children recover within 2-3 weeks with mean time to cough resolution of 8-15 days 2
90% of children are cough-free by day 21 2
Persistent symptoms beyond 4 weeks may represent "post-bronchiolitis syndrome" and warrant further evaluation 2
Long-term sequelae: Increased risk of recurrent wheezing and asthma development later in childhood 1, 7
COMMON PITFALLS SUMMARY
Critical errors to avoid in bronchiolitis management:
Treating based solely on pulse oximetry without clinical correlation—transient desaturations are normal 5
Using continuous pulse oximetry in stable infants—leads to overtreatment of clinically insignificant desaturations 5
Prescribing bronchodilators "to try" without objective assessment of response 5
Giving antibiotics for fever alone or radiographic infiltrates without bacterial confirmation 5
Ordering routine chest X-rays—leads to overdiagnosis and unnecessary interventions 2, 5
Overlooking feeding difficulties when respiratory rate exceeds 60-70 breaths/minute—aspiration risk increases significantly 5
Using hypotonic IV fluids—risk of hyponatremia due to SIADH 5
Mistaking bronchiolitis for asthma in infants <12 months—asthma is extremely rare as first presentation at this age 2