Materials and Experimental Methods. A Galaxy S4 smartphone (Samsung Electronics Co., Seoul, South Korea) with android (mobile operating system of Google) and an iPhone 5 (Apple Inc., Cupertino, CA, USA) with iOS (mobileoperating system of Apple) were used for our investigation.Both mobile operating systems have a 99.8% market share in Korea (iOS 23.1% and android 76.7%) [19]. Therefore, we searched for and identified mobile apps from the Google Play Store and the Apple App Store, the two largest online stores for mobile apps (as of September 2015). Search terms included were “cardiopulmonary resuscitation” OR “CPR” OR “chest compression” OR “basic life support” in both English and Korean languages. In South Korea, the proportion of trueborn Korean is 97.8% [20], and almost all use and speak Korean language with low diversity of languages [21]. Therefore, we excluded apps with no Korean language in screening. And selected versions in the Google Play Store that were also present in the Apple App Store. From the selected apps, we excluded apps that did not contain CPR-related content and had error for operation of apps. Finally, we included apps that contained the following features:(1) training features and (2) emergency support for real-life incidents. “Emergency support for real-life incidents” means that layperson could be served guidance or accurate information for CPR within apps in real cardiac arrest situation; we selected this as mandatory feature. The identification and selection of apps included
in this study are based on Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines