This pilot study investigates the effects of mechanical chest compressions on passive ventilation in out-of-hospital cardiac arrest (OHCA) scenarios. While the topic is relatively niche, the clinical implications of the results could be highly relevant for future guidelines on cardiopulmonary resuscitation (CPR) and their implementation in daily practice. Numerous studies have previously addressed passive ventilation through chest compression-only CPR. Passive ventilation is defined as pulmonary ventilation created by chest compressions only, without extra measures to provide air to the lungs. However, the application of such techniques in pre-hospital settings remains underexplored. Current guidelines typically do not recommend chest compression-only CPR or the use of mechanical chest compression devices as standard practice. This study aims to provide insights into the impact of the Stryker LUCAS 3, an active compression decompression (ACD) device, on airflow within a still compliant thorax and its respiratory system by analysing its effects in an out-of-hospital setting. The results indicate that the passive ventilation achieved through mechanical chest compressions is significantly greater than that observed during manual compressions. This study not only demonstrates larger net inspiratory tidal volumes but also reveals a distinct flow pattern in patients undergoing mechanical compressions, which may suggest more efficient alveolar ventilation. Such improvements could ultimately influence resuscitation outcomes. While further investigation is necessary to fully understand the effects of mechanical chest compression devices on passive ventilation in pre-hospital settings, this study highlights the key differences between manual and mechanical compression techniques. Enhancing passive ventilation through optimizing mechanical chest compressions could further improve oxygen delivery to patients in OHCA, potentially impacting outcomes positively. Furthermore, this thesis addresses CPR in OHCA, a leading cause of mortality in developed countries. Any contributions toward improving outcomes, whether through enhancing survival rates or gathering resuscitation data with previously unknown significance, could have a substantial impact on addressing one of the most prevalent causes of death in our regions, both now and in the future.