Trend in survival after out-of-hospital cardiac arrest and its relationship with bystander cardiopulmonary resuscitation: a six-year prospective observational study in Beijing

Background: Out-of-hospital cardiac arrest (OHCA), a global health problem with a survival rate ranging from 2 to 22% across different countries, has been a leading cause of premature death for decades. The aim of this study was to evaluate the trends of survival after OHCA over time and its relationship with bystander cardiopulmonary resuscitation (CPR), initial shockable rhythm, return of spontaneous circulation (ROSC), and survived event. Methods: In this prospective observational study, data of OHCA patients were collected following the"Utstein style" by the Beijing, China, Emergency Medical Service (EMS) from January 2011 (data from February to June in 2011 was not collected) to October 2016. Patients who had a cardiac arrest and for whom an ambulance was dispatched were included in this study. All cases were followed up to determine hospital discharge or death. The trend of OHCA survival was analyzed using the Chi-square test. The relationship among bystander CPR, initial shockable rhythm, ROSC, survived event, and OHCA survival rate was analyzed using multivariate path analyses with maximum standard likelihood estimation. Results: A total of 25,421 cases were transferred by the Beijing EMS; among them, 5042 (19.8%) were OHCA (median age: 78 years, interquartile range: 63-85, 60.1% male), and 484 (9.6%) received bystander CPR. The survival rate was 0.6%, which did not improve from 2012 to 2015 (P=0.569). Overall, bystander CPR was indirectly associated with an 8.0% (beta = 0.080, 95% confidence interval [CI] = 0.064-0.095, P= 0.002) increase in survival rate. The indirect effect of bystander CPR on survival rate through survived event was 6.6% = 0.066, 95% CI= 0.051-0.081, P=0.002), which accounted for 82.5% (0.066 of 0.080) of the total indirect effect. With every 1 increase in survived event, the possibility of survival rate will directly increase by 53.5% (beta= 0.535, 95% CI= 0.512-0.554, P=0.003). Conclusions: The survival rate after OHCA was low in Beijing which has not improved between 2012 and 2015. The effect of bystander CPR on survival rate was mainly mediated by survived event.