Out-of-hospital cardiac arrest is a serious emergency. In many areas, trained volunteers are alerted by a smartphone app to help before emergency services arrive. While this can save lives, these situations can also be emotionally stressful for the volunteers. This study looks at how these experiences affect volunteer first responders and how they cope with them. It also examines whether a structured follow-up conversation after an event can help reduce stress.

People who respond to a cardiac arrest alert can take part in the study. Participants will answer short questionnaires about their well-being about four weeks and ten weeks after the event. Some participants will also be offered a guided conversation to talk about their experience, while others will not.

The researchers will compare both groups to see if the conversation helps reduce stress over time. The study will also explore which factors may increase or reduce emotional burden.

Participants can stop answering the questionnaires at any time. If signs of increased stress are identified, support options are available. With consent, the study team may contact participants to offer further information and help connect them with support services.

The results of this study may help improve support for volunteer first responders in the future.

Out-of-hospital cardiac arrest (OHCA) remains a major cause of mortality worldwide. Early initiation of cardiopulmonary resuscitation by bystanders is a key determinant of survival. To improve response times, many regions have implemented smartphone-based alerting systems that notify nearby volunteer first responders of suspected cardiac arrest events.

While these systems have demonstrated clinical benefits, the psychological impact on volunteer responders is not yet fully understood. Responding to OHCA incidents may involve exposure to emotionally challenging situations, including unsuccessful resuscitation attempts or distressing scene conditions. At the same time, engagement in such life-saving efforts may also be associated with positive psychological effects, such as a sense of meaning or competence. A better understanding of both burden and resilience factors is needed to optimize support strategies for this population.

The BRAVE study (Burden and Resilience After Volunteer Engagement) is designed to investigate the psychological impact of smartphone-based OHCA alerts on volunteer first responders and to evaluate whether a structured post-event debriefing intervention can improve psychological outcomes.

Participants are recruited via the Corhelper smartphone application, which is routinely used to alert volunteer responders. After completing a routine post-event questionnaire, responders may indicate their interest in being contacted about study participation. Only individuals who provide explicit consent will be contacted by the study team and receive detailed study information.

The study follows a randomized controlled design. Participants are prospectively assigned to either an intervention group receiving a structured debriefing conversation or a control group without this intervention. The allocation ratio is approximately 1:2 due to resource constraints related to the delivery of the intervention.

The structured debriefing consists of a guided conversation conducted by a physician member of the study team, with the option to involve trained personnel from the psychosocial support (PSU) team. The conversation focuses on the reconstruction of the event, clarification of medical and situational aspects, and the individual processing of the experience. The intervention aims to support participants in understanding and coping with the event.

Psychological outcomes are assessed using standardized questionnaires at approximately four weeks (T1) and ten weeks (T2) after the event. Symptoms of post-traumatic stress are measured using the Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5). Personality traits are additionally assessed using the Big Five Inventory (BFI).

Exploratory analyses will additionally assess potential correlations between post-traumatic stress symptoms and individual or event-related factors. These may include prior medical background, previous resuscitation experience, pre-existing personal stress, personality traits measured by the BFI, time to arrival at the scene, resuscitation outcome, and the number of first responders present.

To ensure participant safety, a structured support pathway is implemented. Signs of increased psychological distress are identified based on questionnaire results and/or clinical impression during personal interactions. If indicated, participants may receive additional support, including further conversations with the study team, involvement of the PSU team, or referral to specialized mental health services in cooperation with the Alexianer Center for Mental Health. In the case of questionnaire-based assessments, participants may be contacted proactively by the study team if they have previously consented to such contact.

The study aims to generate evidence on the psychological effects of first responder systems and to evaluate the potential benefit of structured debriefing interventions. The results are expected to inform the development of targeted support strategies for volunteer first responders and contribute to the sustainable implementation of smartphone-based alerting systems.

Inclusion Criteria:

• Volunteer first responders alerted through the "Corhelper" smartphone application
• Sufficient German language skills to understand the study information and to participate in the debriefing conversation and questionnaires
• Written informed consent for study participation
• Actual arrival at the scene with direct exposure to the resuscitation situation (e.g., visual contact with the patient or active participation in resuscitation measures)

Exclusion Criteria:

• Age below 18 years
• Anticipated severe post-traumatic stress symptoms during the course of the study, in order to avoid possible retraumatization
• Already enrolled in the study following a different Corhelper alert event

Individual participant data will not be shared due to the sensitive nature of the psychological and personal data collected in this study and the risk of participant re-identification despite pseudonymization.

Participants and investigators are not blinded due to the nature of the intervention. However, interview data are analyzed independently by assessors who are blinded to group allocation.