sO₂
Arterial oxygen saturation

Definition
sO₂ is called oxygen saturation and is defined as the ratio between the concentrations of O₂Hb and HHb + O₂Hb:

The systematic symbol for arterial blood is sO₂(a). The analyzer symbol may be sO₂.

What does sO₂ tell you?
sO₂(a) is the percentage of oxygenated hemoglobin in relation to the amount of hemoglobin capable of carrying oxygen. sO₂ allows evaluation of oxygenation and dissociation of oxyhemoglobin as expressed in the ODC.

Reference ranges
sO₂(a) normal range (adult): 95-99 % (0.95-0.99)
disclaimer

Clinical interpretation
High (normal) sO₂:
Sufficient utilization of actual oxygen transport capacity. Potential risk of hyperoxia (see pO₂).

Low sO₂:
Common causes of low sO₂:

• Impaired oxygen uptake
• Right shift of ODC

Be aware of the risk of preanalytical errors (air bubbles, storage) on sO₂ values.

For more information, go to Preanalytical considerations.