A patient breathing room air has PaO2 55 mmHg and PaCO2 40 mmHg. Using PAO2 = 150 - PaCO2/0.8, what is the A-a gradient?
Answer and explanation
Correct answer: A. 45 mmHg
- Step 1: PAO2 = 150 - 40/0.8 = 100 mmHg.
- Step 2: A-a gradient = PAO2 - PaO2 = 100 - 55 = 45 mmHg.
Answer
45 mmHg.
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