The goal of this clinical trial is to learn whether using Positive End-Expiratory Pressure (PEEP) during cardiopulmonary resuscitation (CPR) improves outcomes for adults who experience out-of-hospital cardiac arrest, a condition where the heart suddenly stops beating. PEEP is used during ventilation, which may enhance oxygen levels by keeping the airways open throughout CPR. This study aims to determine if using PEEP during CPR helps restart the heart more effectively, improves survival rates, and enhances survival with good neurologic outcomes after a cardiac arrest compared to standard CPR without PEEP. Researchers will randomly assign participants to one of two groups: one receiving CPR with PEEP set at 5 cm of water pressure and the other receiving standard CPR without PEEP. Participants will be treated by emergency medical teams trained in advanced life support, and specialised sensors will measure airflow and airway pressure during resuscitation. Additionally, the study will evaluate potential side effects associated with PEEP, such as increased pressure within the chest or lung injuries. Findings from this trial will guide recommendations on the usage of PEEP in standard CPR practices to potentially improve patient outcomes.