Performance of the decarboxylation index to predict CO removal and minute ventilation reduction under extracorporeal respiratory support.

Background: The aim of this study was to assess the interdependence of extracorporeal blood flow (Qec) and gas flow (GF) in predicting CO removal and reduction of minute mechanical ventilation under extracorporeal respiratory support.

Methods: All patients who benefited from V-V ECMO and high-flow ECCO R in our intensive care unit over a period of 18 months were included. CO removal was calculated from inlet/outlet blood port gases during the first 7 days of oxygenator use. The relationship between the Qec × GF product (named decarboxylation index and expressed in L /min ) and CO removal or expired minute mechanical ventilation reduction ( MV ratio) was studied using linear regression models.

Results: Eighteen patients were analyzed, corresponding to 24 oxygenators and 261 datasets. CO removal was 393 ml/min (IQR, 310-526) for 1.8 m oxygenators and 179 ml/min (IQR, 165-235) for 1.3 m oxygenators. The decarboxylation index was associated linearly with CO removal (R  = 0.62 and R  = 0.77 for the two oxygenators, respectively) and MV ratio (R  = 0.72 and R  = 0.62, respectively). The 20L /min value (considering Qec = 2 L/min and GF = 10 L/min) was associated with an MV ratio between 61% and 29% for 1.8 m oxygenators, and between 62% and 38% for 1.3 m oxygenators.

Conclusion: The decarboxylation index is a simple parameter to predict CO removal and MV ratio under extracorporeal respiratory support.