\[OER=\frac{C_{aO_2}-C_{vO_2}}{C_{aO_2}}\]
Variables
OERoxygen extraction ratio
CaO2[CaO₂]arterial oxygen content (mL O₂/L blood)
CvO2[CvO₂]mixed venous oxygen content (mL O₂/L blood)
Description
What is this formula?
The Oxygen Extraction Ratio (OER) quantifies the fraction of delivered oxygen that is actually extracted and utilized by body tissues.
When to use it
Use this formula when assessing tissue oxygen utilization, shock states, cardiac function, oxygen transport efficiency, or critical care patients.
Example
Data:
CaO2 = 200 mL O₂/L
CvO2 = 150 mL O₂/L
Formula:
OER = (CaO₂ − CvO₂) / CaO₂
Substitution:
OER = (200 − 150) / 200
OER = 50 / 200
Result:
OER = 0.25
OER = 25%
The tissues extract approximately 25% of the oxygen delivered by the circulation.
Applications
- Critical care medicine
- Shock evaluation
- Cardiology
- Exercise physiology
- Hemodynamic monitoring