Performance of The Decarboxylation Index To Predict CO2 Removal And Mechanical Ventilation Reduction Under VV-ECMO Or High-Flow ECCO2R

Abstract Background: Optimal decarboxylation dose under extracorporeal respiratory support to ensure sufficient reduction of mechanical ventilation stress remains unclear and understudied. The aim of this study was to assess the interdependence of blood flow (BF) and gas flow (GF) in predicting CO2 removal and mechanical ventilation reduction (MVR) under extracorporeal respiratory support. Methods: All patients who benefited from veno-venous ECMO (HLS-maquet 7.0, 1.8 m²) and high-flow ECCO2R (HLS-maquet 5.0, 1.3 m²) in our intensive care unit over a period of 18 months were included. CO2 removal was calculated from inlet/outlet blood gases performed in clinical practice during the first 7 days of oxygenator use. The relationship between the BF × GF product and CO2 removal or MVR was studied using linear regression models. Results: Eighteen patients were analysed, corresponding to 24 oxygenators and 261 datasets. CO2 removal was 393 mL/min (IQR, 310–526 mL/min) for 1.8 m2 oxygenators and 179 mL/min (IQR, 165–235 mL/min) for 1.3 m2 oxygenators. The decarboxylation index was associated linearly with CO2 removal (R2 = 0.62 and R2 = 0.77 for the two oxygenators, respectively) and MVR (R2 = 0.72 and R2 = 0.62, respectively). Values in the range 20−30L2/min2 were associated with an MVR ratio between 38% and 58% for 1.8 m2 oxygenators, and between 37% and 55% for 1.3 m2 oxygenators. Conclusion: The decarboxylation index is a simple parameter to predict CO2 removal and MVR under extracorporeal respiratory support. A BF of 2 L2/min2 or more may be necessary to obtain a significant reduction of mechanical convection.Trial Registration: Being a retrospective study, no trial registration was made.