Reply to letter by Müller et al.

We read with great interest the letter from Müller et al. in response to our research article published in RESUSCITATION.1Stroop R. Kerner T. Strickmann B. Hensel M. Mobile phone-based alerting of CPR-trained volunteers simultaneously with the ambulance can reduce the resuscitation-free interval and improve outcome after out-of-hospital cardiac arrest: a German, population-based cohort study.Resuscitation. 2020; 147: 57-64Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar Although we consider the statements of the authors as an important contribution to the post-peer-review-discussion, we do not consider their criticism of the data quality to be justified. They refer to a very recently published study of our group in which estimated response times were used for benchmarking between different regions. There is obviously a misunderstanding with regard to the exact determination of the response time. The following explanations are intended to provide clarification. We use a mobile phone positioning system to locate Mobile-Rescuers who were near a suspected out-of-hospital cardiac arrest. This is achieved using an application that connected the Emergency Dispatch Centre with the smartphones of the Mobile Rescuers via a central web service, navigating the volunteers by car or on foot to the emergency scene. However, Mobile-Rescuers are only alerted if the estimated response time is 8 minutes or less. This decision is based on GPS positioning data (distance between mobile phone and emergency scene) and estimated values regarding mobility aspects (arrival by car: assumed average speed of 40 kilometers per hour; arrival on foot is assumed if the detected distance between mobile phone and emergency scene is 300 meters or less). In addition, a general set-up time of 1 minute is taken into account. As already mentioned above, this approach is primarily the basis for the decision whether a Mobile Rescuer is alerted or not. Regardless of this, however, an automatic notification is sent as standard to the Emergency Dispatch Centre when the Mobile Rescuer arrives on scene. Accordingly, there is an estimated response time (determined before alerting the Mobile Rescuer) and a measured response time (time between alerting and automatic notification). In the district of Gütersloh (North-Rhine-Westphalia, Germany), the time of automatic notification (Mobile Rescuer arrival time) is fully documented. Consequently, in our paper recently published in RESUSCITATION we exclusively used the measured response time for data analysis. In conclusion, the methodological approach in both studies was different.1Stroop R. Kerner T. Strickmann B. Hensel M. Mobile phone-based alerting of CPR-trained volunteers simultaneously with the ambulance can reduce the resuscitation-free interval and improve outcome after out-of-hospital cardiac arrest: a German, population-based cohort study.Resuscitation. 2020; 147: 57-64Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar, 2Stroop R. Hensel M. Kerner T. Smartphone-basierte Ersthelferalarmierung – Auswertung der Alarmierungsdaten aus 7 Mobile-Retter-Regionen.Notarzt. 2020; 31 (239–)https://doi.org/10.1055/a-1224-4103Crossref Scopus (4) Google Scholar In this respect, we hope that all ambiguities could be clarified. We declare that there is no conflict of interest regarding any financial or personal relationships with any other people or organisations that could inappropriately influence or bias our work. Comment on “Mobile phone-based alerting of CPR-trained volunteers simultaneously with the ambulance can reduce the resuscitation-free interval and improve outcome after out-of-hospital cardiac arrest: A German, population-based cohort study”ResuscitationVol. 158PreviewWe congratulate Stroop and coworkers to their successful implementation of a smartphone alerting system (SAS) in the city of Gütersloh,1 aiming to improve survival following cardiac arrest via shortening no-flow times. An important way to demonstrate the benefit of SAS is assessing first responders’ response times (RTs). Stroop et al. report a RT of 4 min following smartphone alert. However, we are concerned about the validity of the presented data. The authors do not describe the method of how they measure response times. Full-Text PDF