Chest and Respiratory Medicine
This domain tests pattern recognition across obstructive and restrictive lung disease, infection, thromboembolism, pleural disease, and respiratory failure. The examiner wants to see that you can interpret spirometry and arterial blood gases yourself rather than order more imaging.
Airflow obstruction
- Asthma shows reversible obstruction (FEV1 improves by 12 percent and 200 mL after bronchodilator), diurnal variability, and atopy; COPD shows persistent obstruction with a FEV1/FVC ratio below 0.70 after bronchodilator.
- Acute severe asthma: inability to complete sentences, respiratory rate above 25, pulse above 110. Life-threatening features are silence, exhaustion, cyanosis, bradycardia, and a normal or rising PaCO2, which signals impending arrest.
- Treatment: oxygen to 94-98 percent, repeated inhaled salbutamol with ipratropium, systemic corticosteroid within the first hour, magnesium sulphate in severe cases; antibiotics only for clear bacterial infection.
Infection and effusion
- Community-acquired pneumonia severity is scored with CURB-65: confusion, urea above 7 mmol/L, respiratory rate 30 or more, systolic below 90 or diastolic 60 or less, age 65 or more. Three or more points means inpatient or intensive care assessment.
- Light criteria classify exudate: pleural protein/serum protein above 0.5, pleural LDH/serum LDH above 0.6, or pleural LDH above two-thirds the upper normal serum limit.
- Empyema and complicated parapneumonic effusion need chest drainage, not antibiotics alone.
Pulmonary embolism and gases
- Use Wells score or the PERC rule first; D-dimer excludes PE only in low or intermediate probability, and CT pulmonary angiography is the test in stable patients.
- Type 1 respiratory failure is hypoxaemia with normal or low PaCO2; type 2 adds a PaCO2 above 6 kPa and usually needs controlled oxygen with target saturations of 88-92 percent in COPD.
Worked example
A 30-year-old woman has sudden pleuritic pain and dyspnoea six days after knee surgery. Pulse is 118, saturation 91 percent, chest is clear. Wells score gives high probability from surgery plus tachycardia. A normal D-dimer would not exclude embolism here, so CT pulmonary angiography is requested with interim therapeutic anticoagulation while renal function and bleeding risk are checked. If she were hypotensive, thrombolysis would precede imaging.
Traps
Reporting a normal PaCO2 in a tachypnoeic asthmatic as reassuring; using D-dimer in high-probability patients; labelling all effusions exudates without applying Light criteria; and giving high-flow oxygen to a CO2-retaining COPD patient.