Mathematical modelling of oxygenation under veno-venous ECMO configuration using either a femoral or a bicaval drainage

Background: The bicaval drainage under veno-venous extracorporeal membrane oxygenation (W ECMO) was compared in present experimental study to the inferior caval drainage in terms of systemic oxygenation. Method: Two mathematical models were built to simulate the inferior vena cavato-right atrium (IVC -> RA) route and the bicaval drainage-to-right atrium return (IVC+SVC -> RA) route using the following parameters: cardiac output (Q(C)), IVC flow/Q(c) ratio, venous oxygen saturation, extracorporeal pump flow (Q(EC)), and pulmonary shunt (PULM-Shunt) to obtain pulmonary artery oxygen saturation (SPAO2) and systemic blood oxygen saturation (SaO(2)). Results: With the IVC -> RA route, SPAO2 and SaO(2) increased linearly with Q(EC)/Q(C) until the threshold of the IVC flow/Q(C) ratio, beyond which the increase in SPAO2 reached a plateau. With the IVC+SVC -> RA route, SPAO2 and SaO(2) increased linearly with Q(EC)/Q(C) until 100% with Q(EC)/Q(C) = 1. The difference in required Q(EC)/Q(C) between the two routes was all the higher as SaO(2) target or PULM-Shunt were high, and occurred all the earlier as PULM-Shunt were high. The required Q(EC) between the two routes could differ from 1.0 L/min (Q(C) = 5 L/min) to 1.5 L/min (Q(C) = 8 L/min) for SaO(2) target= 90%. Corresponding differences of Q(EC) for SaO(2) target= 94% were 4.7 L/min and 7.9 L/min, respectively. Conclusion: Bicaval drainage under ECMO via the IVC+SVC -> RA route gave a superior systemic oxygenation performance when both QEc/Qc and pulmonary shunt were high. The W-VECMO configuration (IVC+SVC -> RA route) might be an attractive rescue strategy in case of refractory hypoxaemia under W ECMO.