Letter by Cornet et al regarding article, "Relationship between supranormal oxygen tension and outcome after resuscitation from cardiac arrest".

Letter by Cornet et al Regarding Article, “Relationship Between Supranormal Oxygen Tension and Outcome After Resuscitation From Cardiac Arrest” To the Editor: We read with great interest the article by Kilgannon and coworkers1 demonstrating a dose-dependent linear relationship between supranormal oxygen tension after resuscitation from cardiac arrest and in-hospital death. This observation is important and merits further investigation, but we question the definition of hypoxia. The present study1 is a secondary analysis of a previously published multicenter cohort study,2 in which Project IMPACT was analyzed. A total of 6326 patients met the inclusion criteria in both studies. However, in the original analysis,2 hypoxia was defined as PaO2 60 mm Hg or PaO2 to fraction of inspired oxygen ratio 300 mm Hg, rendering 3999 patients hypoxic. In the secondary analysis, hypoxia was defined as PaO2 60 mm Hg or PaO2 to fraction of inspired oxygen ratio 200 mm Hg, defining 1867 patients as hypoxic. In other words, 2132 patients were “hypoxic” in the primary analysis but “normoxic” in the secondary analysis. Why did the authors use different definitions of hypoxia? Disclosures None.