The normal range of SaO2 is around 97 percent, although anything in the region of 95 to 100 percent is considered to be within the norm. When combined with PaO2 and CaO2 readings, this range gives a good indication of a patient's blood oxygen levels, and whether they are adequate. As a result, while SaO2 levels are important, they are only one part of the wider picture.
SaO2 levels are dependent on PaO2 levels, as SaO2 measures levels of oxygen saturation in the heme groups of the hemoglobin molecule. PaO2 measures the oxygen pressure in the blood, which allows practitioners to gain insight into how much free oxygen is dissolved in the plasma itself. The higher the PaO2 levels, the higher the SaO2 levels.
It is important to note that neither SaO2 or PaO2 can offer a definitive result when it comes to assessing how much oxygen is present in the blood. Determining this requires knowledge of the amount of oxygen bound to hemoglobin, as well as hemoglobin levels. Some of this information is available from both SaO2 and PaO2 levels, but a third reading of CaO2 is the only one that incorporates the actual amount of hemoglobin content. Therefore, accurate assessment of blood oxygen levels need to incorporate all three forms of analysis.