Oximetry questions

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I am having a difficult time understanding what these mean:

SpO2,

SvO2,

PaO2,

and SaO2

I am studying oximetry in school, and I can't find a clear definition in my books or medical encyclopedia.

Thanks!!

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Specializes in ICU, ED, Med-Surg, Progressive Care.

Ether,

SpO2: what you read off the pulse oximetry machine (pulse oximetry oxygen saturation). Normal is 95-100%.

SvO2: oxygen saturation in central venous blood (it's like the SaO2 of venous blood). Normal is 75%. If you subtract the SvO2 from the SaO2, you can identify how much oxygen is being used by the patient. For example: SaO2 = 100%, and SvO2 = 75%, oxygen consumption is 25%.

PaO2: amount of oxygen dissolved in the blood, measured as a partial-pressure of oxygen. This oxygen is not attached to hemoglobin, rather it is free and floating around in the blood. Tissues cannot use PaO2 effectively and only about 3% of tissue oxygenation comes from the PaO2. Normal is 80-100 torr.

SaO2: amount of hemoglobin that has oxygen bound to it. 100% means that all hemoglobin binding sites have oxygen bound to them. This is measured on a blood gas. 97% of tissue oxygenation comes from the SaO2. Normal is 95-100%.

I hope this helps,

David Woodruff. MSN, RN, CNS, CCRN

President, Ed4Nurses, Inc.

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Thanks :) a lot! That helped!

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