Abstract Su204: Association between delta E _T CO ₂ and Return of Spontaneous Circulation in a National US Cohort

Introduction: International guidelines support use of end-tidal carbon dioxide (E T CO 2 ) for monitoring resuscitation in out-of-hospital cardiac arrest (OHCA). Specific E T CO 2 cutoffs have been proposed for termination of resuscitation, though data on rates of ROSC based on changes in E T CO 2 is limited. We aimed to evaluate the relationship between change in E T CO 2 in OHCA and its relationship to return of spontaneous circulation (ROSC) using a US national database. Methods: This retrospective analysis of National Emergency Medical Services Information System (NEMSIS) datasets from 2020 to 2022 evaluated all adult patients who underwent resuscitation for OHCA and had multiple E T CO 2 measurements. We excluded cases with missing data. The highest difference between two sequential E T CO 2 measurements (MΔE T CO 2 ) and total difference between minimum and maximum E T CO 2 measurements [TΔE T CO 2 ] were calculated for each case. ΔE T CO 2 groups were stratified into 10-unit increments and we compared rates of ROSC between groups. We then used multivariable logistic regression to evaluate the association between each 5 unit increase in ΔE T CO 2 and ROSC. We adjusted for age, sex, location, witness status, initial shockable rhythm, and CPR or AED prior to EMS arrival. Results: We included 274,516 total patients with 1,686,390 E T CO 2 measurements. The median number of E T CO 2 measurements was 5 (IQR 3-8). Median age was 65, 62.8% were male, 60.1% had witnessed arrests, and 78.3% received CPR and 32.3% received AED placement prior to EMS arrival. ROSC rates based on MΔE T CO 2 were 0-10 mmHg [33.3%], 10-20 mmHg [42.3%], 20-30 mmHg [49.7%], 30-40 mmHg [53.2%], and >40 mmHg [56.6%]. ROSC rates for TΔE T CO 2 were 0-10 mmHg [29.6%], 10-20 mmHg [36.7%], 20-30 mmHg [43.5%], 30-40 mmHg [48.9%], and >40 mmHg [54.6%]. Adjusted odds of ROSC per 10 mmHg increase in MΔE T CO 2 was 1.21 [1.21-1.22] and TΔE T CO 2 was 1.19 [1.19-1.19]. Conclusions: Increasing max and overall ΔE T CO 2 was associated with increased rates and odds of ROSC for OHCA.