A 50-year-old man with severe pancreatitis develops acute respiratory distress. On FiO2 0.8 and PEEP 10 cm H2O, PaO2 is 120 mmHg. Chest X-ray shows bilateral infiltrates. There is no evidence of cardiac failure. According to the Berlin definition, this is classified as:
- A Mild ARDS
- B Moderate ARDS ✓
- C Severe ARDS
- D Acute lung injury
Correct answer: B. Moderate ARDS
Explanation
The Berlin definition classifies ARDS severity by the PaO2/FiO2 ratio on PEEP greater than or equal to 5 cm H2O: mild (201 to 300), moderate (101 to 200), and severe (less than or equal to 100). This patient's P/F ratio is 120 divided by 0.8 equals 150, placing him in the moderate ARDS category. The term acute lung injury was eliminated in the Berlin definition, making option D incorrect despite its use in the older AECC criteria.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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