What is the formula to calculate venous oxygen saturation (SvO2)?

The correct formula to calculate venous oxygen saturation (SvO2) is best understood through the concept of oxygen delivery and consumption in the body. SvO2 represents the balance between oxygen delivery (DO2) and oxygen consumption (VO2).

Oxygen delivery (DO2) refers to the amount of oxygen the blood carries to the tissues, determined by factors like cardiac output and hemoglobin levels. Oxygen consumption (VO2) is the amount of oxygen utilized by the tissues to meet metabolic demands. The difference between these two values is crucial, as it indicates how much oxygen is left in the blood after the tissues have extracted what they need.

When using the formula SvO2 = DO2 - VO2, it reflects the fact that the oxygen saturation in venous blood is influenced by how much oxygen has been used by the tissues compared to what has been delivered. Hence, SvO2 signifies how much oxygen remains in the blood after it has passed through the systemic circulation, which is determined by the ratio of oxygen delivery to consumption.

This means that SvO2 can typically be viewed as a direct measure of how well the body is balancing oxygen delivery and consumption, highlighting its importance in assessing patient oxygenation status, particularly in critical care and