Factors Influencing Recirculation in Veno-Venous Extracorporeal Membrane Oxygenation: Insights From a Controlled Bench Study

This study investigated factors influencing recirculation in veno-venous extracorporeal membrane oxygenation (VV ECMO) using a controlled bench model comprising a VV ECMO circuit and a mock circulatory loop with a porcine cadaver heart simulating human right heart anatomy. Several single-lumen cannula (SLC) configurations (15/21 Fr, 15/23 Fr, 17/21 Fr, 17/23 Fr) and double-lumen cannulae (DLC) from two manufacturers were evaluated. Different cannula positions (distance, rotation), ECMO flow (ECF), cardiac output (CO), central venous pressure (CVP) were assessed for their impact on recirculation, measured by ultrasound dilution method. In 31 experimental series (1,641 measurements), increasing CO consistently reduced recirculation, irrespective of cannulation configuration (SLC: R = -0.99; DLC: R = -0.87; p < 0.01), whereas elevating ECF increased it. CO/ECF ratio had a greater impact than CO or ECF alone, with higher values reducing recirculation in both SLC and DLC. In SLC, cannula size or retraction beyond a threshold distance had minimal effect on recirculation. However, in DLCs exact positioning is crucial, as suboptimal placement or rotation markedly increased recirculation.CO and CO/ECF ratio are key determinants of recirculation in all cannulation scenarios. In clinical settings, accurate monitoring of recirculation and CO is essential to optimize VV ECMO oxygen transfer efficiency and should become standard troubleshooting practice.