Figure 17-28 The equivalent circuit of the pulmonary circulation in a patient with a 50% right-to-left shunt. Oxygen content is in mL/100 mL of blood (vol%). A decrease in cardiac output (T) or an increase in O₂ consumption (V̇O₂ ) can cause a decrease in mixed venous oxygen content (from 15 to 10 vol% in this example), which in turn will cause a decrease in the arterial content of oxygen (from 17.5 to 15.0 vol%). In this 50% shunt example, the decrease in mixed venous oxygen content was twice the decrease in arterial oxygen content.