What are the clinical features and diagnosis of bronchiolitis?

Clinical Features and Diagnosis of Bronchiolitis

Clinical Presentation

Bronchiolitis is diagnosed clinically based on history and physical examination alone, without routine laboratory or radiographic studies. 1, 2

Classic Clinical Features

The diagnosis requires identifying a constellation of findings in children younger than 2 years of age 1, 2:

Upper Respiratory Prodrome:

• Initial rhinorrhea and cough preceding lower respiratory symptoms 2, 3
• Viral upper respiratory tract symptoms typically precede respiratory distress 1

Lower Respiratory Signs:

• Tachypnea (respiratory rate ≥70 breaths/minute indicates increased severity risk) 1, 2
• Wheezing and rales on auscultation 1, 2
• Persistent cough 1

Increased Respiratory Effort:

• Grunting 1, 2
• Nasal flaring 1, 2
• Intercostal and/or subcostal retractions 1, 2

Critical History Elements to Assess

Effects on Basic Functions:

• Feeding ability and hydration status (aspiration risk increases when respiratory rate exceeds 60-70 breaths/minute) 1, 4, 2
• Mental status changes including lethargy or irritability 1, 2
• Family's ability to provide care and return for evaluation 1

Risk Factors for Severe Disease:

• Age <12 weeks (highest risk category) 1, 4, 2
• History of prematurity 1, 4, 2
• Hemodynamically significant congenital heart disease (receiving medications for heart failure, moderate-to-severe pulmonary hypertension, or cyanotic heart disease) 1, 4
• Chronic lung disease/bronchopulmonary dysplasia 1, 4, 2
• Immunodeficiency 1, 4, 2
• In utero smoke exposure 1, 2

Physical Examination Specifics

Serial observations over time are necessary because the disease state varies and a single assessment may be inadequate 1, 2. Key examination techniques include:

• Count respiratory rate for a full 60 seconds (shorter observations are less accurate) 1, 2
• Assess work of breathing by observing for accessory muscle use and retractions 1, 2
• Suction and position the infant before examination to decrease upper airway obstruction and improve assessment quality 1
• Evaluate oxygen saturation, but avoid continuous pulse oximetry in stable infants 4, 2

Diagnostic Approach

What TO Do

The diagnosis is clinical—history and physical examination are sufficient. 1, 2 The American Academy of Pediatrics provides a moderate recommendation (Evidence Quality B) that radiographic or laboratory studies should not be obtained routinely 1.

What NOT To Do

Do not routinely order:

• Chest radiographs (approximately 25% of hospitalized infants have atelectasis or infiltrates that are often misinterpreted as bacterial infection, leading to inappropriate antibiotic use) 4, 2, 3
• Viral testing/RSV testing (does not alter management) 2, 3
• Laboratory studies (generally unhelpful and increase costs without improving outcomes) 1, 2

When Diagnostic Testing May Be Considered

For adult or atypical bronchiolitis (non-pediatric cases with chronic symptoms), a comprehensive evaluation is required 1:

• Spirometry with and without bronchodilator 1
• Lung volumes and gas exchange testing 1
• High-resolution CT (HRCT) with expiratory cuts to identify direct signs (airway wall thickening, tree-in-bud pattern) and indirect signs (mosaic attenuation, air-trapping) 1
• Bronchoscopy to rule out infection when bacterial suppurative disease is suspected 1
• Surgical lung biopsy when clinical syndrome, physiology, and HRCT findings do not provide a confident diagnosis 1

Important caveat: Normal chest radiographs and even normal HRCT scans cannot rule out bronchiolar disease, as the resolution is limited to airways >2 mm in diameter 1.

Common Pitfalls to Avoid

• Do not treat based solely on pulse oximetry readings without clinical correlation, as transient desaturations occur in healthy infants 4, 2
• Do not overlook feeding difficulties, as this indicates severity and aspiration risk 4, 2
• Do not assume fever indicates bacterial infection—the risk of serious bacterial infection in febrile infants with bronchiolitis is <1%, though urinary tract infections are the most common serious bacterial infection when they do occur 4, 3
• Do not misinterpret radiographic findings—atelectasis and infiltrates are common in bronchiolitis and do not necessarily indicate bacterial pneumonia 4, 3