SPO2 used to be called which term?

• A. Saturation arterial of oxygen (SaO2)
• B. Saturation of oxygen (SO2)
• C. Oxygen saturation (SpO2)
• D. Partial pressure of oxygen (PaO2)

Answer: (A)

This question tests how oxygen saturation is named and measured in clinical practice. SpO2 is the oxygen saturation read from a pulse oximeter at a peripheral site and serves as an estimate of the true arterial saturation SaO2, which is the saturation measured directly from arterial blood (usually via blood gas analysis with co-oximetry). In older practice, the noninvasive SpO2 reading was sometimes described using the same term SaO2, so SpO2 used to be called arterial oxygen saturation. The other terms don’t fit the context: PaO2 is the actual dissolved oxygen pressure, not saturation; SO2 is a broader or less precise term not the standard label for the pulse oximeter reading.