The effect of dispatcher-assisted cardiopulmonary resuscitation on early defibrillation and return of spontaneous circulation with survival

Background: Dispatcher-assisted cardiopulmonary resuscitation (DA-CPR) programs are implemented to augment bystander CPR and improve outcomes of patients with out-of-hospital cardiac arrest (OHCA). To understand the pathway of how DA-CPR improves outcomes of OHCA, we aimed to evaluate the effect of DA-CPR on defibrillation and return of spontaneous circulation (ROSC) with survival to hospital discharge within 90 min. Methods: We conducted a population-based observational study of all adults with OHCA with presumed cardiac aetiology treated by emergency medical services (EMS) between 2013 and 2016, using a national OHCA registry. We excluded cases without a witness, those that occurred in hospital, were witnessed by an EMS provider, or defibrillated by a layperson. The exposure was bystander CPR status: no bystander CPR (No BCPR), bystander CPR without dispatcher assistance (NDA-BCPR), and bystander CPR with dispatcher assistance (DA-BCPR). The observation time was set to a maximum of 90 min for survival analysis. The primary outcome was ROSC within 90 min leading to being discharged alive (ROSC with survival). The secondary outcomes were ROSC within 90 min leading to being discharged with cerebral performance category I or II (ROSC with good CPC) and first defibrillation within 90 min (defibrillation). Multivariable Cox proportional hazards analysis was performed to calculate adjusted hazard ratios (AHRs), according to bystander CPR status adjusted for potential confounders. Results: Of 25,450 eligible OHCAs, NDA-BCPR was provided for 3193 cases (12.5%) and DA-BCPR was provided for 12,154 cases (47.8%). ROSC with survival was observed in 13.2% of cases with NDA-BCPR and 12.0% with DA-BCPR. Compared with No BCPR, both type of bystander CPR were associated with 44% and 55% increases in ROSC with survival to discharge (AHR, 95% confidence interval (CI): 1.44, 1.27-1.63 for NDA-BCPR and 1.55, 1.41-1.69 for DA-BCPR). DA-BCPR was also associated with defibrillation compared with No-BCPR, accounting for ROSC as a competing risk (AHR 1.16, 95% CI 1.12-1.21). Conclusions: Compared with no bystander CPR provided, both bystander CPR with or without dispatcher assistance were associated with defibrillation and ROSC leading to survival to discharge in patients with witnessed OHCA.