Patients suffering from out-of-hospital cardiac arrest (OHCA) and receiving cardiopulmonary resuscitation (CPR) in terms of advanced life support (ALS) in the city of Vienna, Austria, will be included. A special study team will be dispatched to the event sites by the ambulance service. Trained study fellows will include patients by placing NIRS optodes on the patients' forehead as soon as possible during and/or after CPR. Measurements will continue until 72h post return of spontaneous circulation (ROSC) or the patient's death.
Measurement of Near-Infrared Spectroscopy (NIRS) during and after out-of-hospital cardiac arrest (OHCA) in the city of Vienna and the tertiary university hospital of the Medical University of Vienna, Austria.~NIRS will be evaluated as a tool for resuscitation quality assessment as well as a prognosticator for cardiac arrest outcomes. Already-existing literature will be taken into account, and already-existing cutoffs and prognosticating values will be assessed and - if eligible - validated in a real-life setting.