Pulmonology
Core concepts
Build a framework around obstructive vs restrictive physiology: asthma and COPD show reduced FEV1/FVC with reversibility distinguishing them; restriction shows reduced FVC with preserved ratio. Know ABG interpretation in respiratory failure (type 1 vs type 2), the CURB-65 severity score for pneumonia, and the Wells/Geneva approach to suspected pulmonary embolism culminating in CT pulmonary angiography. Understand pleural fluid analysis (Light's criteria), the management of tension pneumothorax (immediate needle decompression before imaging), and the staging and initial treatment of COPD exacerbations (bronchodilators, steroids, antibiotics when indicated, controlled oxygen targeting 88–92%).
Traps
Examiners test the "do not wait for the X-ray" rule in tension pneumothorax and the danger of high-flow oxygen in CO2 retainers. Confusion between asthma (reversible, eosinophilic, diurnal) and COPD (fixed, neutrophilic, smoking-related) is common. Remember that PE can present with a normal chest radiograph and that D-dimer is only useful in low/intermediate pretest probability. Sarcoidosis shows bilateral hilar lymphadenopathy and elevated ACE; TB shows upper-lobe cavitation.
Worked rule of thumb
For any patient with sudden dyspnea plus unilateral leg swelling and tachycardia, calculate pretest probability first: low probability → D-dimer; high probability → go straight to CTPA. A negative D-dimer in a high-probability patient does not exclude PE.
Key points
- Tension pneumothorax is a clinical diagnosis; decompress immediately.
- Target SpO2 88–92% in patients at risk of CO2 retention.
- Light's criteria separate exudate from transudate.
- D-dimer is a rule-out tool only in low/intermediate probability.
- CURB-65 guides site of care in pneumonia.