An O2 saturation of 90% corresponds to which PO2 value?

To determine the PO2 value that corresponds to an oxygen saturation (O2 saturation) of 90%, understanding the relationship between these two parameters is essential. Oxygen saturation is a measure of the percentage of hemoglobin binding sites in the bloodstream occupied by oxygen. PO2 refers to the partial pressure of oxygen dissolved in plasma.

The oxygen-hemoglobin dissociation curve illustrates this relationship, showing how hemoglobin saturation with oxygen changes with varying PO2 levels. At a PO2 of approximately 60 mmHg, the oxygen saturation is about 90%, indicating that at this specific PO2, the hemoglobin is still capable of saturating sufficiently with oxygen while being at a critical level of partial pressure.

Higher PO2 values, such as 70 mmHg or above, would result in a saturation higher than 90%, while lower values significantly below this range would lead to lower saturations well below 90%. Thus, the understanding of the climbing and then steepening phase of the saturation curve further clarifies that at a PO2 level of 60 mmHg, oxygen saturation is likely to be around 90%. Therefore, the correct correlation matches an O2 saturation of 90% to a PO2 value of 60 mmHg.