Introduction: Post-cardiac arrest patients are often exposed to 100% oxygen during cardiopulmonary resuscitation and the early post-arrest period. It is unclear whether this contributes to development of pulmonary dysfunction or other patient outcomes.
Methods: We performed a retrospective cohort study including post-arrest patients who survived and were mechanically ventilated at least 24 hours after return of spontaneous circulation. Our primary exposure of interest was inspired oxygen, which we operationalized by calculating the area under the curve of the fraction of inspired oxygen (FiO₂AUC) for each patient over 24 hours. We collected baseline demographic, cardiovascular, pulmonary and cardiac arrest-specific covariates. Our main outcomes were change in the respiratory subscale of the Sequential Organ Failure Assessment score (SOFA-R) and change in dynamic pulmonary compliance from baseline to 48 hours. Secondary outcomes were survival to hospital discharge and Cerebral Performance Category at discharge.
Results: We included 170 patients. The first partial pressure of arterial oxygen (PaO₂):FiO₂ ratio was 241 ± 137, and 85% of patients had pulmonary failure and 55% had cardiovascular failure at presentation. Higher FiO₂AUC was not associated with change in SOFA-R score or dynamic pulmonary compliance from baseline to 48 hours. However, higher FiO₂AUC was associated with decreased survival to hospital discharge and worse neurological outcomes. This was driven by a 50% decrease in survival in the highest quartile of FiO₂AUC compared to other quartiles (odds ratio for survival in the highest quartile compared to the lowest three quartiles 0.32 (95% confidence interval 0.13 to 0.79), P = 0.003).
Conclusions: Higher exposure to inhaled oxygen in the first 24 hours after cardiac arrest was not associated with deterioration in gas exchange or pulmonary compliance after cardiac arrest, but was associated with decreased survival and worse neurological outcomes.