Background
We assume Smartphone-based alerting systems for voluntary first-aiders could make a contribution to improve the treatment of patients with cardiac arrest in the prehospital setting. For the first time in Germany, such a project, i.e. Mobile Rescuers, has been evaluated regarding feasibility and outcome-related parameters.

Methods
Mobile Rescuers were alerted complementary to the regular emergency medical service (EMS). This was achieved by an app which connected the rescue coordination center with the smartphone of the Mobile Rescuer via a central web service, navigating the first-aider to the emergency scene. 
Primary endpoint was the time period between emergency call and arrival of adequate emergency care at the scene. Secondary endpoints were recruitment of Mobile Rescuers, return of spontaneous circulation and frequency of hospital admission.

Results
In the meanwhile, the smartphone-based alerting system Mobile Rescuers has been implemented in 10 German counties and one urban district covering in total a population of 2.5 million people and an area of 12.000 km2. 1.5‰ of the population, i.e. 3.700 Mobile Rescuers, have been recruited and trained as voluntary first-aiders.
Depending on the differing population densities in the rural and urban regions and the implementation progress, the area-to-Mobile Rescuer relation varies between 1.3 and 6.8 km2 per first aider. Regarding a 30-month evaluation period of the longest running county Guetersloh, in total, 477 resuscitations were registered. In 59% of all cases Mobile Rescuers reached the scene before the EMS.
The average response time was significantly reduced as a result of the activity of Mobile Rescuers (4.4 min vs. 8.7 min, p<0.01).
Return of spontaneous circulation was seen in 63% of the patients resuscitated by Mobile Rescuers compared to 51% of patients initially treated by the EMS team (p=0.12).
The rate of patients admitted to hospital in a stabilized condition was not significantly increased, when resuscitation was initiated by a Mobile Rescuer, just as the rate of patients, who have been admitted under ongoing resuscitation.
  
Conclusions
In comparison with established EMS concepts, the Smartphone-based alerting system Mobile Rescuers is associated with a shorter response time and thus a reduced “No-flow”-time. Thus, the treatment of patients has been improved significantly.

Implementation of the Smartphone-Based First-Aiders Alerting System "Mobile Rescuers"