Shunt equation AKA the Berggren equation - quantifies extent to which venous blood bypasses oxygenation in the capillaries of the lung (R-to-L)
It relates the percentage of blood flow that is not exposed to inhaled gas, called the shunt fraction Qs/Qt, to the content of oxygen in venous, arterial, and pulmonary capillary blood.
Qs/Qt = (CcO2 − CaO2) / (CcO2 − CvO2)
Where:
Qs = Pulmonary Physiologic Shunt (mL/min)
Qt = Cardiac Output (mL/min)
CcO2 = End-pulmonary-capillary Oxygen Content
CaO2 = Arterial oxygen content
CvO2 = Mixed Venous Oxygen Content
If we assume that end-pulmonary capillary blood is saturated entirely and that the hemoglobin concentration does not change, then
Qs/Qt = (1− SaO2) / (1− SvO2)
Where:
SaO2 is arterial oxygen saturation
SvO2 is venous oxygen saturation
