Using the alveolar gas equation with FiO2 = 0.40, PaCO2 = 44, Pb = 760, PH2O = 47, and RQ = 0.8, PAO2 is approximately:

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Multiple Choice

Using the alveolar gas equation with FiO2 = 0.40, PaCO2 = 44, Pb = 760, PH2O = 47, and RQ = 0.8, PAO2 is approximately:

The alveolar gas equation links PAO2 to the inspired oxygen fraction and CO2 elimination. It’s PAO2 = FiO2 × (Pb − PH2O) − (PaCO2 / R). Compute step by step: - Pb − PH2O = 760 − 47 = 713 mmHg. - FiO2 × (Pb − PH2O) = 0.40 × 713 = 285.2 mmHg. - PaCO2 / R = 44 / 0.8 = 55 mmHg. - PAO2 = 285.2 − 55 = 230.2 mmHg. So, PAO2 is about 230 mmHg. Minor rounding differences or using a slightly different R value can yield values near 235 mmHg in some references, but with the given numbers the result is ~230 mmHg.

The alveolar gas equation links PAO2 to the inspired oxygen fraction and CO2 elimination. It’s PAO2 = FiO2 × (Pb − PH2O) − (PaCO2 / R).

Compute step by step:

  • Pb − PH2O = 760 − 47 = 713 mmHg.

  • FiO2 × (Pb − PH2O) = 0.40 × 713 = 285.2 mmHg.

  • PaCO2 / R = 44 / 0.8 = 55 mmHg.

  • PAO2 = 285.2 − 55 = 230.2 mmHg.

So, PAO2 is about 230 mmHg. Minor rounding differences or using a slightly different R value can yield values near 235 mmHg in some references, but with the given numbers the result is ~230 mmHg.

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