What is the normal oxygen extraction ratio in a healthy person?

What is the normal oxygen extraction ratio in a healthy person?

• A. 15%
• B. 50%
• C. 60%
• D. 25%

Answer: (D)

Oxygen extraction ratio tells us what fraction of the oxygen delivered to the tissues is actually taken up and used. It’s calculated from arterial and venous oxygen content, and in a healthy person at rest it’s about one quarter of the delivered oxygen. Why this is the best answer: about 25% of delivered O2 is extracted by tissues under resting conditions, leaving roughly 75% of the oxygen content still in the venous blood. This corresponds to a normal mixed venous oxygen saturation around 65–75% and an OER roughly 0.2–0.3. That resting value reflects the balance between oxygen delivery and consumption in a typical standing or seated adult. Context helps: the OER is related to oxygen delivery and consumption through VO2 ≈ DO2 × OER. If delivery drops, extraction can rise to maintain VO2, but at rest the typical extraction is around 25%. Values like 50–60% would indicate unusually high extraction (as seen in high-demand states or low DO2), while a value around 15% would be unusually low for resting, well-oxygenated tissue. So the normal oxygen extraction ratio in a healthy person is about 25%.

Oxygen extraction ratio tells us what fraction of the oxygen delivered to the tissues is actually taken up and used. It’s calculated from arterial and venous oxygen content, and in a healthy person at rest it’s about one quarter of the delivered oxygen.

Why this is the best answer: about 25% of delivered O2 is extracted by tissues under resting conditions, leaving roughly 75% of the oxygen content still in the venous blood. This corresponds to a normal mixed venous oxygen saturation around 65–75% and an OER roughly 0.2–0.3. That resting value reflects the balance between oxygen delivery and consumption in a typical standing or seated adult.

Context helps: the OER is related to oxygen delivery and consumption through VO2 ≈ DO2 × OER. If delivery drops, extraction can rise to maintain VO2, but at rest the typical extraction is around 25%. Values like 50–60% would indicate unusually high extraction (as seen in high-demand states or low DO2), while a value around 15% would be unusually low for resting, well-oxygenated tissue.

So the normal oxygen extraction ratio in a healthy person is about 25%.