Paediatric Respiratory Medicine (HERMES Syllabus)
Paediatric respiratory medicine is examined as a single HERMES/ERS syllabus domain. Questions test whether you can apply respiratory physiology, diagnostics and therapy to lungs that are still growing, where airway calibre, chest-wall compliance and drug handling all differ from adults.
Core rules and concepts
- Airway resistance rises with the fourth power of radius, so infants with mucosal oedema obstruct quickly; a compliant chest wall and low functional residual capacity mean rapid desaturation and apnoea risk.
- Bronchiolitis (typically RSV, under 12 months) is managed supportively: oxygen to SpO2 at least 90-92%, enteral fluids and suction. Bronchodilators, corticosteroids, antibiotics and chest physiotherapy are not routinely indicated.
- Croup: single-dose dexamethasone 0.15-0.6 mg/kg; nebulised adrenaline 1:1000, 0.5 mL/kg (maximum 5 mL), for moderate to severe stridor.
- Community-acquired pneumonia: amoxicillin first line; add a macrolide when atypical pathogens such as Mycoplasma are suspected.
- Cystic fibrosis: sweat chloride at least 60 mmol/L confirms the diagnosis; 30-59 mmol/L is intermediate and requires repeat testing or CFTR analysis. Care combines airway clearance with CFTR modulators.
- Asthma: a bronchodilator response of at least 12% in FEV1 supports the diagnosis; exhaled nitric oxide is an adjunct, not a standalone test.
- Primary ciliary dyskinesia: low nasal nitric oxide, with situs inversus in about half of cases.
Worked example
A 14-month-old with three days of coryza, wheeze and SpO2 88% has no focal signs. This is bronchiolitis. Give oxygen targeting at least 90%, fluids and nasal suction; do not prescribe salbutamol, steroids or antibiotics. Monitor for apnoea and inadequate feeding, which are the main triggers for escalation.
Traps that cost marks
- Treating bronchiolitic wheeze with bronchodilators.
- Performing a sweat test on a dehydrated infant, or failing to repeat an intermediate result.
- Labelling a preschool wheezer as asthmatic without documented variability.
- Missing an inhaled foreign body: unilateral wheeze with reduced breath sounds on one side.