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 ETCO2 and rSO2 at 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 rSO2 and ETCO2 predicted ROSC.
Results: 225 patients presented to the ED with cardiac arrest between 10/11 and 10/14 of which 100 had both rSO2 and ETCO2 measurements. Thirty three patients (33%) had sustained ROSC, only 2 survived to discharge. The AUCs for rSO2 and ETCO2 were similar (0.69 [95% CI, 0.59-0.80] and 0.77 [95% CI, 0.68-0.86], respectively), however, rSO2 and ETCO2 were poorly correlated (0.12, 95% CI, -0.08-0.31). The optimal cutoffs for rSO2 and ETCO2 were 50% and 20mm Hg respectively. At these cutoffs, ETCO2 was more sensitive (100%, 95% CI 87-100 vs. 48%, 31-66) but rSO2 was more specific (85%, 95% CI, 74-92 vs. 45%, 33-57).
Conclusions: While poorly correlated, rSO2 and ETCO2 have similar diagnostic characteristics. ETCO2 is more sensitive and rSO2 is more specific at predicting ROSC in OHCA.
Keywords: Accuracy; Cerebral oximetry; End tidal CO(2); Resuscitation; Return of spontaneous circulation.
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