Cerebral oximetry versus end tidal CO2in predicting ROSC after cardiac arrest

Study objective Both end tidal CO2(ETCO2) and cerebral oxygen saturations (rSO2) have been studied to determine their ability to monitor the effectiveness of CPR and predict return of spontaneous circulation (ROSC). We compared the accuracy of ETCO2and rSO2at predicting ROSC in ED patients with out-of-hospital cardiac arrest (OHCA). Methods We performed a prospective, observational study of adult ED patients presenting in cardiac arrest. We collected demographic and clinical data including age, gender, presenting rhythm, rSO2, and ETCO2. We used receiver operating characteristic curves to compare how well rSO2and ETCO2predicted ROSC. Results 225 patients presented to the ED with cardiac arrest between 10/11 and 10/14 of which 100 had both rSO2and ETCO2measurements. Thirty three patients (33%) had sustained ROSC, only 2 survived to discharge. The AUCs for rSO2and ETCO2were similar (0.69 [95% CI, 0.59-0.80] and 0.77 [95% CI, 0.68-0.86], respectively), however, rSO2and ETCO2were poorly correlated (0.12, 95% CI, −0.08-0.31). The optimal cutoffs for rSO2and ETCO2were 50% and 20mm Hg respectively. At these cutoffs, ETCO2was more sensitive (100%, 95% CI 87-100 vs. 48%, 31-66) but rSO2was more specific (85%, 95% CI, 74-92 vs. 45%, 33-57). Conclusions While poorly correlated, rSO2and ETCO2have similar diagnostic characteristics. ETCO2is more sensitive and rSO2is more specific at predicting ROSC in OHCA.