Agency factors associated with first response systems that improve out-of-hospital cardiac arrest outcomes

Background: Data are conflicting regarding the association between first responder (FR) intervention and improved outcomes after out-of-hospital cardiac arrest (OHCA). We evaluated characteristics of agencies that have positive associations between FR interventions and outcomes.Methods: We analyzed the 2016-2021 national Cardiac Arrest Registry to Enhance Survival (CARES). We defined the exposures as FR CPR and AED. The outcome was survival with favorable neurologic status. We used logistic regression models to evaluate the association between FR interventions with OHCA outcome for each agency, stratifying agencies into positive association (95% confidence interval above 1) and no/inverse association (95% confidence below or including 1). We compared characteristics between cohorts.Results: For the association between FR CPR and outcomes, 21 agencies caring for 42,856 OHCAs had a positive association; 371 agencies car-ing for 449,824 OHCAs had no association. For FR AED, 47 agencies caring for 103,120 OHCAs had a positive association; 262 agencies caring for 327,761 OHCAs had no association. Comparing agency characteristics for FR CPR, agencies with a positive association had more annual OHCAs (+300), lower FR CPR rate (-11.3%), and lower FR AED rate (-10.8%). Comparing FR AED, agencies with a positive association had more OHCAs per year (+150.5), lower FR CPR rate (-6.8%), lower FR AED rate (-13.3%), lower response time (-0.6 minutes), and more OHCAs from high-income neighborhoods (+3.7%).Conclusion: FR AED more commonly had a positive association with outcomes than FR CPR. Agencies with better outcomes from FR interventions treated more OHCAs and had lower rates of FR intervention.