b'CARES 2023 Annual ReportWhat makes a first responder system effective?Ryan Huebinger, MD, Associate Professor of Emergency Medicine, University of New Mexico, Albuquerque, New MexicoOptimizing time to out-of-hospital cardiac arrest (OHCA) interventions, such as CPR and Automated External Defibrillator (AED) placement, is critical to maximizing their effectiveness. Ideally, these interventions are performed by the first person witnessing the OHCA, such as a bystander. However, in situations where bystanders are unable to administer these life-saving therapies, first responders (FR) can often respond to the OHCAs more quickly than the EMS team, decreasing the time to high-quality CPR and AED placement. Since FRs decrease the time to OHCA treatments, it would be logical to assume that FR care would be linked to better outcomes. However, studies evaluating the association between FR intervention and improved outcomes have produced mixed results, with some finding no association. No prior study had attempted to evaluate the difference between OHCA response systems that effectively use FRs compared to those that do not. Therefore, we sought to identify characteristics of EMS agencies that have a positive association between FR intervention and better outcomes.To answer this question, we first identified EMS agencies that had a positive association between FR intervention and patient outcomes. We defined FR interventions as either CPR or AED first initiated by a FR, and the outcome was defined as survival with favorable neurologic status (CPC of 1 or 2). Using the 2016-2021 national CARES dataset, we performed nearly two thousand logistic regressions to evaluate the association between FR interventions and outcomes. After excluding 457 EMS agencies in CARES due to poor model fit, we identified agencies that had a positive association between the FR intervention and outcome, defined as an odds ratio and 95% confidence interval entirely above 1 (Figure 1).Figure 1. Individual agency association between FR CPR and survival with favorable neurologic status; black dots represent odds ratios and grey bars represent 95% CIs; red diamonds represent agencies with 95% CIs that fall entirely above 1 (21 agencies) or below 1 (5 agencies). Odds ratios and CIs 4 are attenuated to 4. Using these results, we stratified agencies into two groups: those with positive association and those with no association between FR CPR/AED and good outcomes. We then compared the characteristics of agencies in each stratum to identify differences that might explain the varying outcomes. We found that more agencies had a positive association between FR CPR (21) and outcomes, than FR AED and outcomes (47). For FR CPR, compared to agencies with no association, those with a positive association treated more OHCAs per year, had lower rates of FR interventions, lower bystander CPR rates, and treated fewer rural OHCAs (Table 1). These findings were similar for FR AED, with the additional differences of agencies with a positive association having lower responses times and a higher proportion of OHCAs occurring in high income communities (Table 2). At first glance, the results suggest that using FRs less often leads to better outcomes. However, we believe these findings reflect more about the effectiveness of an agencys overall system when a FR is the first provider on scene. In a highly effective system with minimal gaps in coverage, FRs might be utilized to enhance the systems quality of care. Conversely, if a system has large coverage gaps, FRs may be used to compensate for deficiencies in ambulance coverage. In such an system, early FR intervention may be indicative of an OHCA that occurred in a coverage gap with prolonged response or transport time. Thus, by virtue of having a FR intervention, the patient might be receiving inferior care than a patient that experienced an OHCA in an area with better ambulance coverage. This interpretation is supported by the finding that positive association agencies treated fewer rural OHCAs and had lower response times. 28'