Prediction of successful veno-venous extracorporeal life support liberation using the oxygen challenge test

The oxygen challenge test (OCT) is an underutilized measure of lung recovery, easily performed prior to proceeding with a trial-off V-V ECLS as part of a weaning algorithm. Evidence-based thresholds for OCT results which support continuing with V-V ECLS weaning are lacking, making interpretation of these tests challenging in clinical practice.

We performed a retrospective review of patients commenced on V-V ECLS as a bridge-to-recovery at Vancouver General Hospital from 2015-2019. The absolute PaO₂ post-OCT and change in PaO₂ proportional to incremental FiO₂ change on the ventilator (∆PaO₂ ) were evaluated as predictive screening metrics for identifying conditions favorable for successful trial-off of V-V ECLS.

An optimal cut-off of PaO₂  ≥ 240 mm Hg post-OCT (AUC 0.77) and ∆PaO₂  ≥ 250 mm Hg (AUC 0.76) was identified as a threshold for predicting successful trials-off. A total of 26 and 24 patients achieved post-OCT PaO₂ and ∆PaO₂ thresholds, and 100% of these patients were liberated successfully from ECLS during their admission.

The OCT can serve as an effective screen of shunt reduction and native lung recovery which can be used alongside other measures of ventilation to assess for suitability of liberation from V-V ECLS prior to a trial-off. Achieving a PaO₂  ≥ 240 mm Hg post-OCT is a strong prognostic indicator for successful liberation from V-V ECLS during ICU admission.