Paiva EF, et al. - The aim with which this work was planned was to identify whether any level of end-tidal carbon dioxide (ETCO2) measured during cardiopulmonary resuscitation (CPR) correlates with return of spontaneous circulation (ROSC) or survival in adults experiencing cardiac arrest in any setting. Existing evidence suggested that ETCO2 levels have limited prognostic importance for patients who have experienced cardiac arrest. They observed that extreme or trending ETCO2 values could be more useful than static mid-range levels, in view of the many potential confounders that can influence initial levels.