After a long research process, the KATRETTER-App was launched on October 16 at the Berlin fire department. In order to improve the chances of survival in case of cardiovascular arrest, volunteers in the immediate vicinity of the emergency scene shall be alerted. These volunteers can be on the scene faster than professional rescue teams and start a cardiac massage early. The KATRETTER app is the result of the ENSURE research project, in which the DRU was also involved as a project partner.