Unexpected cardiac arrest is a frequent and devastating event with a high mortality and morbidity. Half of the patients who survive to ICU admission ultimately die because of hypoxic-ischemic encephalopathy. With CPR and advanced life support, blood and oxygen delivery to heart and brain is preserved until circulation is restored. During CPR, coronary perfusion pressure is a significant predictor of increased rates of return of spontaneous circulation (ROSC) and survival to hospital discharge, while cerebral perfusion pressure is crucial for good neurologic outcome. Existing efforts to reduce mortality and morbidity focus on rapid recognition of cardiac arrest, initiation of basic and advanced life support (ALS), and optimization of post-arrest care. Clamping the descending aorta during cardio-pulmonary resuscitation (CPR) should redistribute the blood flow towards brain and heart. Animal models of continuous balloon occlusion of the aorta in non-traumatic cardiac arrest have shown meaningful increases in coronary artery blood flow, coronary artery perfusion pressure and carotid blood flow, leading to improved rates of ROSC, 48h-survival and neurological function. In humans, occlusion of the aorta using a REBOA catheter in the management of non-compressible abdominal or pelvic hemorrhage has shown improvements in hemodynamic profiles and has proved to be feasible in both, clinical and preclinical settings for trauma patients in hemorrhagic shock. These promising data provide an opportunity to improve outcome after cardiac arrest in humans too. The investigators have developed a protocol for the reliable and safe placement of a REBOA-catheter during cardiac arrest in a clinical setting (see ClinicalTrials.gov Identifier: NCT03664557). Damage to heart and brain from lack of oxygen supply occurs during the first minutes following cardiac arrest. It is therefore crucial to apply any measure to improve efficacy of CPR early in the course of events and therapy. After proving feasibility in a clinical setting in the trial mentioned above, the next logical step and specific goal of this study is to transfer this protocol to the preclinical setting, and to investigate the effect of temporary endovascular occlusion of the descending aorta on the efficacy of CPR early in the course of treatment of out-of hospital cardiac arrest by means of an increase in blood pressure.