VV-ECMO Recirculation Calculator VV-ECMO Recirculation Calculator This calculator determines the percentage of recirculation during VV-ECMO using oxygen saturation values. Saturation of blood entering the oxygenator (SpreO2) (%): Saturation of blood leaving the oxygenator (SpostO2) (%): Saturation of blood in the pulmonary artery (SvO2) (%): Calculate Recirculation (%)