Modifiable Factors Associated With Survival After Out-of-Hospital Cardiac Arrest in the Pan-Asian Resuscitation Outcomes Study Hideharu Tanaka, MD; Marcus E. H. Ong, MBBS*; Fahad J. Siddiqui, MBBS; Matthew H. M. Ma, MD; Hiroshi Kaneko, MBA; Kyung Won Lee, MD; Kentaro Kajino, MD; Chih-Hao Lin, MD; Han Nee Gan, MBBS; Pairoj Khruekarnchana, MD; Omer Alsakaf, PhD; Nik H. Rahman, MBCHB; Nausheen E. Doctor, MBBS; Pryseley Assam, PhD; Sang Do Shin, MD; for the PAROS Clinical Research Network † *Corresponding Author. E-mail: marcus.ong.e.h@sgh.com.sg. Study objective: The study aims to identify modifiable factors associated with improved out-of-hospital cardiac arrest survival among communities in the Pan-Asian Resuscitation Outcomes Study (PAROS) Clinical Research Network: Japan, Singapore, South Korea, Malaysia, Taiwan, Thailand, and the United Arab Emirates (Dubai). Methods: This was a prospective, international, multicenter cohort study of out-of-hospital cardiac arrest in the Asia- Pacific. Arrests caused by trauma, patients who were not transported by emergency medical services (EMS), and pediatric out-of-hospital cardiac arrest cases (<18 years) were excluded from the analysis. Modifiable out-of-hospital factors (bystander cardiopulmonary resuscitation [CPR] and defibrillation, out-of-hospital defibrillation, advanced airway, and drug administration) were compared for all out-of-hospital cardiac arrest patients presenting to EMS and participating hospitals. The primary outcome measure was survival to hospital discharge or 30 days of hospitalization (if not discharged). We used multilevel mixed-effects logistic regression models to identify factors independently associated with out-of-hospital cardiac arrest survival, accounting for clustering within each community. Results: Of 66,780 out-of-hospital cardiac arrest cases reported between January 2009 and December 2012, we included 56,765 in the analysis. In the adjusted model, modifiable factors associated with improved out-of-hospital cardiac arrest outcomes included bystander CPR (odds ratio [OR] 1.43; 95% confidence interval [CI] 1.31 to 1.55), response time less than or equal to 8 minutes (OR 1.52; 95% CI 1.35 to 1.71), and out-of-hospital defibrillation (OR 2.31; 95% CI 1.96 to 2.72). Out-of-hospital advanced airway (OR 0.73; 95% CI 0.67 to 0.80) was negatively associated with out-of-hospital cardiac arrest survival. Conclusion: In the PAROS cohort, bystander CPR, out-of-hospital defibrillation, and response time less than or equal to 8 minutes were positively associated with increased out-of-hospital cardiac arrest survival, whereas out-of-hospital advanced airway was associated with decreased out-of-hospital cardiac arrest survival. Developing EMS systems should focus on basic life support interventions in out-of-hospital cardiac arrest resuscitation. [Ann Emerg Med. 2017;-:1-10.] Please see page XX for the Editor’s Capsule Summary of this article. 0196-0644/$-see front matter Copyright © 2017 by the American College of Emergency Physicians. http://dx.doi.org/10.1016/j.annemergmed.2017.07.484 INTRODUCTION Background The incidence of out-of-hospital cardiac arrest ranges from 50 to 60 per 100,000 person-years globally. 1 Out-of- hospital cardiac arrest registries in the United States 2,3 and Europe 4,5 have reported survival rates ranging from 7.5% to 10.8%. However, out-of-hospital cardiac arrest survival in Asia is lower. The Pan-Asian Resuscitation Outcomes Study (PAROS) registry has observed an out-of-hospital cardiac arrest survival rate of only 5.4%. 6 This finding implies that survival can be improved further in out-of- hospital cardiac arrest systems in Asia. North American studies have identified several modifiable factors in the chain of survival 7 (eg, bystander cardiopulmonary resuscitation [CPR], defibrillation) associated with out-of-hospital cardiac arrest survival. 8 The importance of these factors in Asian communities is unknown. For example, although countries such as Japan, Korea, Singapore, and Taiwan have well-established emergency medical services (EMS) † All investigators are listed in the Appendix. Volume -, no. - : - 2017 Annals of Emergency Medicine 1 EMERGENCY MEDICAL SERVICES/ORIGINAL RESEARCH