What is the normal difference between alveolar and arterial PO2?

The normal difference between alveolar PO2 and arterial PO2, commonly referred to as the A-a gradient, is typically around 10 mm Hg in healthy individuals. This gradient reflects the efficiency of gas exchange in the lungs and is influenced by various factors such as ventilation, perfusion, and the diffusion characteristics of oxygen.

A difference of approximately 10 mm Hg indicates effective oxygen transfer from the alveoli into the arterial blood. Values significantly higher than this may suggest issues such as ventilation-perfusion mismatch, diffusion impairment, or shunting, which could indicate underlying respiratory or cardiac conditions. Understanding this normal range is crucial for evaluating pulmonary function and diagnosing potential disorders.