What is the normal range for arterial oxygen tension (PaO2) in a healthy adult?

What is the normal range for arterial oxygen tension (PaO2) in a healthy adult?

• A. 60-100 mmHg
• B. 80-100 mmHg
• C. 90-110 mmHg
• D. 75-95 mmHg

Answer: (B)

PaO2 is the amount of oxygen dissolved in arterial blood and reflects how well oxygen moves from the lungs into the blood. In a healthy adult breathing room air at sea level, the lungs oxygenate blood efficiently, so the arterial oxygen tension sits in a narrow, normal range around 80–100 mmHg. This range is typical because equilibrium with the alveolar oxygen tension (about 100 mmHg in healthy lungs) and the small A-a gradient keep PaO2 near that level. Values below about 80 mmHg indicate hypoxemia, while significantly higher values are uncommon without extra oxygen. So the best match is 80–100 mmHg. The other ranges either extend into lower, potentially abnormal territory or miss the upper limit near 100 mmHg.

PaO2 is the amount of oxygen dissolved in arterial blood and reflects how well oxygen moves from the lungs into the blood. In a healthy adult breathing room air at sea level, the lungs oxygenate blood efficiently, so the arterial oxygen tension sits in a narrow, normal range around 80–100 mmHg. This range is typical because equilibrium with the alveolar oxygen tension (about 100 mmHg in healthy lungs) and the small A-a gradient keep PaO2 near that level. Values below about 80 mmHg indicate hypoxemia, while significantly higher values are uncommon without extra oxygen. So the best match is 80–100 mmHg. The other ranges either extend into lower, potentially abnormal territory or miss the upper limit near 100 mmHg.