Recirculation in Veno-Venous Extracorporeal Membrane Oxygenation.

This review focuses on recirculation in the context of Veno-Venous Extracorporeal Life Support in adults. The methods employed to calculate and quantify the extent of recirculation, as well as factors affecting recirculation and interventions that could reduce recirculation, are detailed. As recirculation may significantly reduce extracorporeal oxygen delivery, leading to refractory hypoxemia, detecting and quantifying the recirculation fraction is fundamental in order to optimize VV-ECMO lung support. Although it is necessary to assess extracorporeal oxygen delivery, quantifying the amount of recirculation may be difficult. Besides mathematical methods, different experimental techniques for the direct measurement of recirculation are in development at present. Moreover, specific interventions and ECMO configurations could significantly reduce recirculation, and innovative systems are under study in this regard. Nevertheless, further human studies are needed to validate and standardize their use in clinical practice, and there remain limited data on their effectiveness and safety. More pre-clinical and clinical studies are required to assess the results obtained thus far and to improve the technologies to minimize the potential complications associated with their use.