Paediatric Respiratory Disease: Developmental Physiology and Age-Specific Management
Paediatric respiratory medicine tests whether you can apply developmental physiology rather than adult rules. Common themes are bronchiolitis, croup, preschool wheeze, asthma, cystic fibrosis, primary ciliary dyskinesia, and congenital lung lesions.
Core rules
- Infants have higher respiratory rates, compliant chest walls, and small airways; normal values and drug doses are age- and weight-specific.
- Bronchiolitis is a clinical diagnosis in children under 2: coryza, wheeze or crackles, and increased work of breathing. Management is supportive - hydration, suction, and oxygen for hypoxaemia; bronchodilators, corticosteroids, and antibiotics are not routine.
- Croup causes barking cough, stridor, and hoarseness; dexamethasone is given for all severities, with nebulised adrenaline for moderate-to-severe stridor.
- Preschool wheeze is heterogeneous; do not label it asthma automatically. CF diagnosis uses sweat chloride and/or CFTR genotyping; PCD needs specialist testing.
Worked example
A 4-month-old with 2 days of coryza, feeding difficulty, wheeze, crackles, and SpO2 93% in room air has bronchiolitis. Assess hydration and respiratory effort; give oxygen if below the local threshold (commonly 90–92%); suction secretions; support feeding. A trial of salbutamol or steroids is not indicated. Escalate for apnoea, exhaustion, or rising CO2.
Traps
Treating infant wheeze as asthma; applying adult oxygen targets; missing apnoea in young infants; and overusing antibiotics for viral bronchiolitis.