What is the alveolar oxygen tension at sea level when breathing room air with a PaCO2 of 27 mmHg?

To determine the alveolar oxygen tension at sea level while breathing room air, one must understand the relationship between alveolar oxygen tension (PAO2) and arterial carbon dioxide tension (PaCO2). The formula commonly used to estimate alveolar oxygen tension is:

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

Where FiO2 is the fraction of inspired oxygen (which is approximately 0.21 in room air), Patm is the atmospheric pressure (usually around 760 mmHg at sea level), PH2O is the water vapor pressure (typically about 47 mmHg at body temperature), and R is the respiratory quotient (approximately 0.8 for mixed diet).

Given that PaCO2 is 27 mmHg, which is on the lower side indicating hyperventilation, one can expect an increase in PAO2 due to reduced carbon dioxide levels at a given respiratory condition.

Applying these values:

1. Use FiO2 of 0.21 (for room air).

2. Use Patm of 760 mmHg and PH2O of approximately 47 mmHg.

3. Insert the PaCO2 of 27 mmHg and R of