If I have an SpO2, why might I need an arterial blood gas measurement?

While SpO2 can be useful in many cases, there are certain situations where an arterial blood gas (ABG) should be drawn and analyzed. If the pulse oximeter shows a tracing that is dampened or erratic, or low PI or signal quality indicator, this may indicate that the SpO2 readings are unreliable and an ABG is warranted. Also, if there are any other factors present that might reduce the pulse oximeter’s accuracy (such as poor perfusion, low body temperature, etc.), an ABG should be obtained. 

Other reasons to get an arterial blood gas include if there is a clinical suspicion of Met-Hb, CO-Hb, S-Hb, or other hemoglobin types. Additionally, pulse oximetry does not provide information about ventilation or acid-base status, so an ABG is needed in situations where this information is also needed.

Keywords: ABG, arterial, blood gas