Re-evaluation Of Hypo- And Hyperoxemia In Patients With Respiratory Failure And Veno-Venous Extracorporeal Membrane Oxygenation

Background: Many patients in the ICU receive oxygen to secure blood and tissue oxygenation. Increasing evidence shows exposure to high fractions of inhaled oxygen (FiO2) being associated with adverse effects. In patients with severe ARDS, veno-venous Extracorporeal Membrane Oxygenation (VV-ECMO) can be implemented as a rescue therapy and PaO2 levels can be controlled by the blood flow of the VV-ECMO. Yet, optimal oxygenation targets in ARDS patients treated with VV-ECMO are unknown. Methods: Retrospective analysis of 443 patients with severe ARDS treated with VV-ECMO. Regression analyses were performed for mortality and time-weighted averages of PaO2 and FiO2. Furthermore, considering a possible non-linear relationship, a restricted cubic spline (RCS) model was performed for PaO2. Results: A simple logistic regression for mean PaO2 and ICU mortality showed a significant positive association (per mmHg OR 0.99 [95%CI 0.98-1.00], p=0.002). RCS analysis showed a U-shaped association of mortality and mean paO2 (paO2 69.70-90.24mmHg: OR 0.92 [95%CI 0.89-0.94], p<0.001; paO2 90.24-123.40mmHg: OR 1.09 [95%CI 1.06-1.13], p<0.001). A model including PaO2 as RCS variable and FiO2 showed significant associations of mortality with both variables (PaO2 69.70-90.24mmHg: OR 0.94 [95%CI 0.91-0.97], p<0.001; paO2 90.24-123.40 mmHg: OR 1.07 [95%CI 1.04-1.11], p<0.001; FiO2: OR 35.98 [95%CI 8.67-158.60], p<0.001, VIF<1.11). Conclusions: PaO2-levels in patients with ARDS and VV-ECMO have a U-shaped association with mortality. Optimal outcomes are observed in the 90-123 mmHg range, which is higher compared to non-ECMO settings. Whether this is explainable by increased tissue oxygenation with concurrent avoidance of pulmonary hypoxia should be subject of future research.