Calculating Mixed Venous Saturation during Veno-Venous Extracorporeal Membrane Oxygenation

Introduction: Recirculation (R), the shunting of arterial blood back into to the venous lumen, commonly occurs during veno-venous extracorporeal membrane oxygenation (VV-ECMO) and renders the monitoring of the venous line oxygen saturation no longer reflective of patient mixed venous oxygen saturation (SVO2). Previously, we failed to prove the hypothesis that, once R is known, it is possible to calculate the SVO2 of a patient on VV-ECMO. We hypothesize that we can calculate SVO2 during VV-ECMO if we account for and add an additional correction factor to our model for dissolved oxygen content. Therefore, the purpose of this study is to derive a more accurate model that will allow clinicians to determine SVO2 during VV-ECMO when ultrasound dilution is being used to quantify R. Methods: Using an extracorporeal circuit primed with fresh porcine blood, two stocks of blood were produced; (1) arterial blood (AB), and (2) venous blood (VB). To mimic recirculation, the AB and VB were mixed together in precise rati...