Pulmonary Disease and Critical Care
Core concepts
Focus on asthma and COPD exacerbations, community-acquired pneumonia, pulmonary embolism, pleural effusion, ARDS, and sepsis physiology. Asthma management centers on inhaled beta-agonists, ipratropium, systemic steroids, and magnesium for severe cases; avoid routine antibiotics. COPD exacerbations add controlled oxygen (target 88-92%), bronchodilators, steroids, and antibiotics when sputum purulence or ventilatory support is present. PE diagnosis depends on pretest probability: PERC only in low-risk patients, D-dimer in low-to-intermediate risk, and CT pulmonary angiography in high risk or positive D-dimer. ARDS uses the Berlin definition with lung-protective ventilation at 6 mL/kg predicted body weight.
Traps
- Ordering D-dimer in a high-probability patient instead of imaging.
- Using PERC in anyone with moderate or high pretest probability.
- Missing Light criteria when a pleural fluid looks borderline.
- Forgetting permissive hypercapnia and plateau-pressure limits in ARDS.
- Treating CURB-65 score 0-1 pneumonia with admission when outpatient therapy is appropriate.
- Overlooking obstructive shock from tension pneumothorax or massive PE.
Worked example
Pleural fluid: protein 3.2 g/dL with serum 6.0 (ratio 0.53), LDH 210 with serum 180 (ratio 1.17), and pleural LDH above two-thirds of the serum upper limit. Any single criterion makes it an exudate; this fluid meets two. Next step is not diuresis but diagnostic evaluation for infection, malignancy, or pulmonary embolism. Rule of thumb: transudates reflect systemic forces; exudates reflect local inflammation.