What is hypoxemia?

• A. Low oxygen content present in blood.
• B. Low oxygen in a tissue.
• C. High oxygen in tissues.
• D. Normal oxygen in blood.

Answer: (B)

This question tests understanding of the difference between oxygen levels in blood and tissues. Hypoxemia means there is less oxygen in the blood than normal, typically in the arterial blood, and is usually identified by a reduced PaO2 or lower oxygen saturation on blood gas testing. It describes the oxygen content of the blood itself, not directly the oxygen status of tissues. Hypoxia, on the other hand, refers to insufficient oxygen delivery to or use by the tissues. So the term described is about blood oxygen levels, while low oxygen in tissues would be hypoxia.