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ABG's.................????

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by dreamrider_212 dreamrider_212 (Member)

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I am struggling with the difference/significance of PaO2 and SaO2 for my final next week. Does anyone know of a website that has REALLY basic information that might be helpful, or can anyone explain it for me - any info would be soooooo helpful right now. Thanks!!

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scrubsnhugsRN specializes in ER/AMS/OPD/UC.

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This is how I remember it, correct me anyone if I am wrong, PaO2 is related to oxegen in the tissues (perfusion) and SaO2 is the actual oxegen being carried in the red blood cells. These numbers are compared with Carbon dioxide levels and acid base levels, which will tell you accuratley how much Co2 they are releasing (or storing). There is a 30 60 30 ratio rule that applies....this question might be better answered on a CCU forum where ABG's are frequently drawn.

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]Look up the 'Oxygen Dissociation Curve'.

]Pa02 measures partial pressure of oxygen in the blood (plasma & hemoglobin).

]Sa02 measures the percentage of available hemoglobin actually carrying oxygen.

]So, at normal levels, they are usually about the same numbers but one is a pressure and one is a percentage.

]The Oxygen Dissociation Curve shows the relationship between pressure and percentage. You'll see that at normal ranges they are close because the curve flattens. ]At lower Pa02 levels the gradient changes in relationship to saturation.

]Acidosis and high body temp will also lower Sa02 at the same Pa02 level.

]I hope that helps!

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Daytonite is a BSN, RN and specializes in med/surg, telemetry, IV therapy, mgmt.

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Actually, the article that Siri posted has the answer for the OP. It's one of the best ABG resources on the Internet for nurses these days. Under the section on "What is saturation?" is the explanation for what SaO2 is. Under the section "What does the PaO2 mean?" is the explanation of what this measurement is.

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]I read the link, and I was done with my 2 cents, but then I thought maybe I should say something, just to avoid confusion for someone.

]The definition of Sa02 in the article is true but #4 is a common error... Sa02 is measured blood analysis (ABG) and Sp02 is pulse oximetry. They both use the same principle of light spectrums through hemoglobin, but Sa02 % is not the same as a pulse ox sat %.

]Both are a measurement of hemoglobin 02 saturation affected by arterial 02 content, but t]he definitions, methods and accuracies are different.

]Sp02 can use the 40-50-60/70-80-90 Rule. Assuming normal pH, PC02 and Hb values, saturations of 70%, 80% and 90% are roughly equivalent to Pa02 values of 40, 50, and 60. Or the Minus 30 Rule... depending on what you remember best. Pulse oximetry is only an estimate and a tool.

]Sa02 isn't linear like that... it changes, and the difference is more as hypoxia increases because of the dis-affinity of hemoglobin for 02. Sa02 accurately indicates the changes in hemoglobin saturation and considers the effects of PC02, temp and pH. That's where the Oxygen Dissociation Curve comes in.

]However, it's not a huge difference between Sa02 and Sp02 until Pa02 levels are

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I am struggling with the difference/significance of PaO2 and SaO2 for my final next week. Does anyone know of a website that has REALLY basic information that might be helpful, or can anyone explain it for me - any info would be soooooo helpful right now. Thanks!!

go to http://www.manuelsweb.com/abg.htm it puts it all together in one table to understand it.

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