Grant: CIHR-ICRH Travel Awards - General pool

BACKGROUND: While individuals with out-of-hospital cardiac arrest (OHCA) benefit from the presence of a bystander witness, most cases remain unwitnessed and very few of these survive. Biosensor technologies have been proposed as a solution to address unwitnessed OHCA which may result in more survivors to hospital discharge. We sought to estimate the impact of increased recognition, to simulate the potential impact of biosensors to detect OHCA. . METHODS: We included cases from the British Columbia Cardiac Arrest Registry (2019-2020), which includes Emergency Medical Services (EMS)-assessed OHCAs. We excluded cases that would not have benefitted from early recognition (EMS-witnessed, terminal illness, or do-not-resuscitate). Using a mediation analysis, we estimated the relative benefits on survival of a witness recognizing vs. intervening in an OHCA; and estimated the expected additional number of survivors resulting from increasing recognition alone using a bootstrap logistic regression framework. RESULTS: Of 13,655 EMS-assessed cases, 11,412 were included (6314 EMS-treated, 5098 EMS-untreated). Survival to hospital discharge was 191/8879 (2.2%) in unwitnessed cases and 429/2533 (17%) in bystander-witnessed cases. Of the total effect attributable to a bystander witness, recognition accounted for 84% (95% CI: 72, 80) of the benefit. If all previously unwitnessed cases had been bystander witnessed, we would expect 1198 additional survivors. If these cases had been recognized, but no interventions performed, we would expect 912 additional survivors. (Table 1). CONCLUSION: Unwitnessed OHCA account for the majority of OHCAs, yet survival is dismal. Methods to improve recognition, such as with biosensor technologies, may lead to substantial improvements in overall survival.