What barometric pressure at sea level is used in the alveolar gas equation (PAO2)?

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Multiple Choice

What barometric pressure at sea level is used in the alveolar gas equation (PAO2)?

At sea level, the barometric pressure is 760 mmHg. In the alveolar gas equation, you use this Pb value as the baseline atmospheric pressure, and then account for humidity and gas tensions: PAO2 = FiO2 × (Pb − PH2O) − PaCO2/R, with PH2O about 47 mmHg. Using 760 mmHg as Pb reflects standard sea-level atmospheric pressure, whereas the other numbers don’t represent that baseline and would misstate the oxygen portion of the equation.

At sea level, the barometric pressure is 760 mmHg. In the alveolar gas equation, you use this Pb value as the baseline atmospheric pressure, and then account for humidity and gas tensions: PAO2 = FiO2 × (Pb − PH2O) − PaCO2/R, with PH2O about 47 mmHg. Using 760 mmHg as Pb reflects standard sea-level atmospheric pressure, whereas the other numbers don’t represent that baseline and would misstate the oxygen portion of the equation.

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