Calculate the PaO2/FiO2 ratio for PaO2 90 mmHg and FiO2 0.40.

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Multiple Choice

Calculate the PaO2/FiO2 ratio for PaO2 90 mmHg and FiO2 0.40.

The PaO2/FiO2 ratio measures how well oxygen is moving from the lungs into the blood by dividing the arterial oxygen tension by the inspired oxygen fraction, and you must use FiO2 as a decimal, not as a percentage. So with PaO2 of 90 mmHg and FiO2 of 0.40, you divide 90 by 0.40: 90 ÷ 0.40 = 225. The ratio is 225, which fits the interpretation range for mild oxygenation impairment. A common pitfall is treating FiO2 as 40 instead of 0.40, which would lead to an incorrect result.

The PaO2/FiO2 ratio measures how well oxygen is moving from the lungs into the blood by dividing the arterial oxygen tension by the inspired oxygen fraction, and you must use FiO2 as a decimal, not as a percentage. So with PaO2 of 90 mmHg and FiO2 of 0.40, you divide 90 by 0.40: 90 ÷ 0.40 = 225. The ratio is 225, which fits the interpretation range for mild oxygenation impairment. A common pitfall is treating FiO2 as 40 instead of 0.40, which would lead to an incorrect result.

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