Twenty minutes after the initiation of ECMO extracorporeal circulation with an auxiliary flow rate of 4 L/min, the arterial partial pressure of oxygen (PaO2) was found to be an average of 140 mmHg with inferior vena cava (IVC) drainage and superior vena cava (SVC) infusion, 120 mmHg with right atrial (RA) infusion, and 85 mmHg with IVC infusion. It was orally presented that the optimal infusion site is the SVC.