To achieve this goal, 22 patients with out-of-hospital cardiac arrest (OHCA) treated by physicians of the prehospital physician response system located at the Medical University of Graz shall be included into this trial. All patients will receive Advanced Life Support (ALS) interventions according to current guidelines issued by the European Resuscitation Council (ERC). In addition, arterial lines will be placed and arterial blood pressure will be measured continuously. This intervention is already considered standard of care at this prehospital physician response system and performed routinely as part of the local ALS algorithm.