What is the alveolar oxygen tension at sea level given a PaCO2 of 27mmHg?

To determine the alveolar oxygen tension at sea level, we can use the alveolar gas equation:

PAO2 = (Patm - PH2O) x FiO2 - (PaCO2/R)

At sea level, atmospheric pressure (Patm) is approximately 760 mmHg, and the partial pressure of water vapor (PH2O) at body temperature is roughly 47 mmHg. FiO2, the fraction of inspired oxygen, is typically about 0.21 for room air. The respiratory quotient (R) is usually taken as 0.8.

Using these values, we can calculate PAO2:

1. First, we find the effective pressure after subtracting water vapor pressure from atmospheric pressure:

• Effective atmospheric pressure = 760 mmHg - 47 mmHg = 713 mmHg

2. Next, we calculate the contribution of oxygen from the inspired air:

• PAO2 (without considering PaCO2) = 713 mmHg x 0.21 ≈ 149.73 mmHg

3. Then, we account for the PaCO2 of 27 mmHg using the R value (0.8):

• The adjustment for CO2 =