PULSE OX vs. PaO2

[LoveMedicine100]

Can someone explain what the difference between PULSE OX vs. PaO2 is?

I thought I knew but then I did a question and got it wrong.

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[Szent]

"Pulse Ox" is otherwise known as SpO2 or percent (%) saturation of oxygen on hemoglobin.

PaO2 is the partial pressure of O2 in arterial blood, which is what determines the SpO2.

The relationship is seen in the image below:

The thing to note here is that a SpO2 of 90% seems pretty high, but it corresponds to a PaO2 of 60 which is the tipping point for rapidly decreasing O2 saturation.

 

[Myxedema]

Pulse oximetry measures oxygen saturation (SaO2), which represents how much hemoglobin is saturated with oxygen. PaO2 is partial pressure of oxygen in arterial blood. One addition concept here is the oxygen content of blood (CaO2), which ties SaO2 and PaO2 together. CaO2 = How much oxygen is carried by Hb + dissolved oxygen in blood. In other words, CaO2 = (Hb x SaO2 x 1.34) + (PaO2 x 0.003). [Constants you see have to do with the chemical and physical properties of Hb and blood.]

 

[LoveMedicine100]

Thanks guys! I get it now