ScvO2, or "central venous oxygen saturation," is a measurement of the relationship between oxygen demand and oxygen consumption in the body. If ScvO2 values are low, then the oxygen delivered is insufficient for the body's metabolic demand, and a high ScvO2 value shows high oxygen delivered for the body's demand. Normal ScvO2 values are equal to about 70 percent.
Tissues and organs demand oxygen, but cannot store it for future use; all oxygen used for metabolic processes must come from the arterial system. Oxygen consumption is measured by taking the difference between the oxygen delivered by the arteries and the oxygen returned to the heart by the veins. ScvO2 values are generally higher than mixed venous oxygen saturation, or SvO2 values, because ScvO2 measurements are not mixed with the venous blood from the coronary sinus, though both values trend together. These values are considered one of the vital signs in the health of an individual, as they measure the oxygen balance in an individual that is necessary to sustain life. In individuals where the oxygen consumed is less than the oxygen demand, local tissue hypoxia, or oxygen starvation, occurs. Global tissue hypoxia is a is a key development in multi-organ failure and eventually death.