PaO2/FiO2 ratio: PaO2 = 85 mmHg, FiO2 = 0.40. What is PaO2/FiO2?

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Multiple Choice

PaO2/FiO2 ratio: PaO2 = 85 mmHg, FiO2 = 0.40. What is PaO2/FiO2?

The PaO2/FiO2 ratio shows how well oxygen moves from the lungs into the blood, calculated by dividing the arterial oxygen tension (PaO2) by the fraction of inspired oxygen (FiO2) expressed as a decimal. Here, PaO2 is 85 mmHg and FiO2 is 0.40 (40%), so 85 ÷ 0.40 = 212.5. The ratio is therefore about 212.5 mmHg, which matches the option around 212.5. In context, normal values on room air are roughly 400–500, so a lower ratio indicates reduced oxygenation requiring more support.

The PaO2/FiO2 ratio shows how well oxygen moves from the lungs into the blood, calculated by dividing the arterial oxygen tension (PaO2) by the fraction of inspired oxygen (FiO2) expressed as a decimal. Here, PaO2 is 85 mmHg and FiO2 is 0.40 (40%), so 85 ÷ 0.40 = 212.5. The ratio is therefore about 212.5 mmHg, which matches the option around 212.5. In context, normal values on room air are roughly 400–500, so a lower ratio indicates reduced oxygenation requiring more support.

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