Optimising the impact of smartphone-activated volunteer responder programs on out-of-hospital cardiac arrest outcomes by increasing responder density

The chain of survival outlines the critical steps in resuscitation that increase the likelihood of survival for people who experience out‐of‐hospital sudden cardiac arrest, including bystander cardiopulmonary resuscitation (CPR) and early defibrillation as important components. Some authors suggest that focusing on the links at which most patients enter the chain would achieve the greatest improvements in outcomes.