The SO2 values in IVC-FA were considered as basal level. The difference of oxygen saturation (ΔSO2) was obtained by subtracting the basal SO2 values from the SO2 values in SVC-FA, IVC-CA and FA-IJV, respectively. Basal levels were similar among sheep shifted to different cannulation. *P <0.01 vs. SVC-FA; #P <0.05 vs. IVC-CA; §P <0.01 vs. IVC-CA. FA-IJV: an additional return cannula was added into the internal jugular vein on the basis of femoral veno-arterial extracorporeal membrane oxygenation; IVC: inferior vena cava; IVC-CA: a drainage cannula was inserted into the inferior vena cava and a return cannula was inserted into the carotid artery; IVC-FA: a drainage cannula was placed into the inferior vena cava through the femoral vein and a return cannula was inserted into the femoral artery; PA: pulmonary artery; SO2: oxygen saturation; SVC: superior vena cava. SVC-FA: a drainage cannula was placed into the superior vena cava through the femoral vein and a return cannula was placed into the femoral artery.