PaO2 vs SaO2

  1. 0
    What's the difference....which one is from a pulse ox? thanks!

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  2. 14 Comments...

  3. 1
    pulse oximetry -- SaO2 with normal value >95%
    crazylilkelly likes this.
  4. 0
    Quote from bubbly30
    pulse oximetry -- SaO2 with normal value >95%
    that's what i thought.....def an example of not using real world situations......above 90 is always good!
  5. 0
    PaO2 stands for the partial pressure of O2 in arterial blood, measured in mmHg.
    SaO2 is the arterial O2 saturation.
  6. 8
    PaO2 = measures oxygen in the blood (80-100)
    SaO2 = measures tissue perfusion (pulse ox >95%)
    CEPJ, ashlieewrightt, MatureNS, and 5 others like this.
  7. 2
    Quote from Nagmamahal, RN
    PaO2 = measures oxygen in the blood (80-100)
    SaO2 = measures tissue perfusion (pulse ox >95%)
    Both definitions provided here are simplistic.

    The PaO2, like I said, is the partial pressure of O2 in arterial blood-- typically measured via ABG.

    SaO2 doesn't measure tissue perfusion. It measures as a percentage the amount of hemoglobin molecules which are oxygenated (oxyhemoglobin) in arterial blood.
    ozoian and CrystalClear75 like this.
  8. 6
    I'm not sure why these concepts are not stated more clearly in nursing education.
    Although a late response, I'm sure others want to know a few details that make the difference between Pa02 and Sa02 more clear and relevant:

    Oxygen travels in blood via to mechanisms:
    1) Bound to hemoglobin
    2) Dissolved in plasma

    SaO2 (and its indirect measurement SpO2) describe the amount of oxygen bound to hemoglobin in arterial blood. The term "saturation" likens hemoglobin to a sponge that becomes saturated with oxygen. The measurement is given as a percentage.

    PaO2 describes the amount of oxygen dissolved in arterial blood plasma. The measurement is given as a pressure value (mmHg).

    There is a relationship between the two numbers, which is described in the oxyhemoglobin dissociation curve. (yes, THAT oxyhemoglobin dissociation curve.) Without getting too far into it, roughly speaking all other things being equal PaO2 and SaO2 relate as follows:

    SaO2 50% = Pa02 26.6 mmHg (aka P50); 70=40; 90=60; 95=80; 99=100

    These numbers change depending on which way the curve shifts.
    lfrank7, holinurse, TaikoRN, and 3 others like this.
  9. 1
    I'm studying this thing right now cause tomorrow morning i got an oral exam on it... i'm at the first year of nurse university here in Italy.

    I thought it would be helpful to post the oxyhemoglobin dissociation curve pic from my slides


    minirn likes this.
  10. 2
    While good to know the difference, not necessary to have this much detail for the NCLEX.
    turnforthenurseRN and erican3232 like this.
  11. 1
    Same here, just wondering if someone was interested in seeing the values right from the diagram
    tacomaster likes this.


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