A 50-year-old man with sepsis develops acute hypoxemic respiratory failure. Chest X-ray shows bilateral diffuse alveolar opacities. Arterial blood gas on FiO2 0.8 and PEEP 8 cm H2O shows PaO2 65 mmHg. There is no clinical evidence of cardiac failure. According to the Berlin definition, what is the severity of ARDS?

• A Mild (PaO2/FiO2 201 to 300)
• B Moderate (PaO2/FiO2 101 to 200)
• C Does not meet ARDS criteria
• D Severe (PaO2/FiO2 less than or equal to 100) ✓

Explanation

PaO2/FiO2 equals 65 divided by 0.8, which is 81.25 mmHg. This is less than or equal to 100, indicating severe ARDS. The Berlin definition requires PEEP of at least 5 cm H2O for classification, which is met here. Bilateral opacities not explained by effusion or cardiac failure are also present.

Reference: Ranieri et al., JAMA, 2012 (Berlin Definition) ed.

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