Prognostic accuracy of end-tidal carbon dioxide in cardiac arrest: a systematic review and meta-analysis

Background Cardiac arrest, a critical emergency with high fatality rates, needs accurate early predictors of resuscitation outcomes. End-tidal carbon dioxide (ETCO 2 ) monitoring, reflecting tissue perfusion and metabolic activity, is highlighted in guidelines for predicting return of spontaneous circulation (ROSC). This systematic review and meta-analysis evaluates the prognostic accuracy of ETCO 2 at various time points and cut-offs to enhance clinical decision-making during cardiac arrest. Methods A systematic search of MEDLINE, Embase and the Cochrane Library identified relevant prognostic accuracy studies. Inclusion criteria were original articles reporting prognostic accuracy of ETCO 2 for ROSC prediction in adult cardiac arrest patients. Sensitivity, specificity and 95% CIs were calculated for ETCO 2 measurements at initial, 10 and 20 min using 2×2 contingency tables. A multiple thresholds model was used for meta-analysis, and the Median of Medians method analysed median ETCO2 values. Results Fourteen studies with 3186 cardiac arrest patients were included. The optimal ETCO 2 cut-off was 19.8 mm Hg at initial (sensitivity 0.75 (95% CI 0.60 to 0.85), specificity 0.53 (95% CI 0.40 to 0.65)), 15.7 mm Hg at 10 min (sensitivity 0.91 (95% CI 0.72 to 0.97), specificity 0.68 (95% CI 0.56 to 0.78)) and 8.5 mm Hg at 20 min (sensitivity 0.95 (95% CI 0.53 to 0.99), specificity 0.78 (95% CI 0.39 to 0.95)). The highest area under the curve (AUC) was 0.88 (95% CI 0.31 to 0.98) at 20 min, followed by 0.82 (95% CI 0.61 to 0.91) at 10 min and 0.67 (95% CI 0.57 to 0.75) initially. Conclusions While initial ETCO 2 demonstrates limited prognostic accuracy for ROSC with a pooled AUC of only 0.67, ETCO 2 measurements taken at 10 and 20 min provide a negative predictive value exceeding 0.95 when using a cut-off of 10 mm Hg. However, to meet the stringent criteria for termination of resuscitation (TOR) decisions, a lower cut-off, such as 5 mm Hg, or the incorporation of additional prognostic indicators would be necessary. Serial ETCO 2 monitoring could also be considered as a potential adjunct in current TOR guidelines. Significant variability between studies necessitates cautious interpretation of these results. PROSPERO registration number CRD42024527811.