Normal mixed venous oxygen tension (PvO2) is approximately 40 mmHg, representing the balance between oxygen consumption and oxygen delivery. A true PvO2 measurement must come from a mixed venous blood sample containing venous drainage from the SVC, IVC, and the heart. Thus, the sample should be obtained from a pulmonary artery catheter. There are several factors that determine PvO2, which can be remembered using the mnemonic COALS:
- Cardiac output
- Oxygen consumption
- Amount of hemoglobin
- Loading of hemoglobin
- Saturation of hemoglobin
Of note, PvO2 can be used in lieu of SvO2 (mixed venous oxygen saturation), which is normally 65-75%.
- Butterworth IV, JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s Clinical Anesthesiology, 5th ed. New York, NY: McGraw Hill; 2013
- Jensen, Niels (2003). Clinical Arterial Blood Gas Analysis. Retrieved from https://www.anesthesiologyboards.com/written/sample.html.