Integrating initial end-tidal CO2 and early changes in cerebral oxygen saturation to predict ROSC in out-of-hospital cardiac arrest: a retrospective feasibility study

• Combined initial ETCO2 and early ΔStO2 improved prediction of sustained ROSC in OHCA. • ROSC patients had higher initial ETCO2 and rising StO2 during early CPR. • ΔStO2 at 4 min plus initial ETCO2 was strongly associated with ROSC (OR 16.29). • Dual-parameter monitoring may support real-time prognostication during resuscitation. To evaluate whether integrating initial end-tidal carbon dioxide (ETCO2) and early changes in cerebral oxygen saturation (StO2) measured by near-infrared spectroscopy (NIRS) improves the prediction of return of spontaneous circulation (ROSC) in patients with out-of-hospital cardiac arrest (OHCA). Retrospective observational feasibility study. A tertiary emergency critical care centre in Japan between August 2019 and April 2020. Adult patients with OHCA transported to the emergency department (ED). Patients without NIRS monitoring—most commonly those presenting at night when monitoring was not feasible with available staffing—were excluded. The primary outcome was sustained ROSC. Predictive parameters included initial StO2, initial ETCO2, and changes (Δ) in StO2 at 4, 8, and 16 min. Of 359 eligible patients, 55 underwent dual monitoring and were included. The ROSC group had significantly higher initial ETCO 2 (P = 0.036). Time-series analysis revealed that an increase in StO 2 (ΔStO 2 ) at 4 min, combined with initial ETCO 2 , was significantly associated with ROSC (Odds Ratio 16.29; 95% CI 1.65 to 160.43), with better apparent discrimination than either single parameter alone. Combining early changes in StO 2 with initial ETCO 2 may improve ROSC prediction compared with either parameter alone. Dual-parameter monitoring shows potential for real-time prognostication during CPR.