Cardiopulmonary resuscitation (CPR) in patients suffering from cardiac arrest out of hospitals is based on strict clinical practice guidelines. However, the evidence base for these treatment recommendation is insufficient in many respects. While knowledge about basic interventions, that are capable of restoring spontaneous circulation and improving neurologically intact survival - chest compressions, application of oxygen and early defibrillation -, has increased over the last decade, advanced treatment options - advanced airway management, vascular access, application of vasoactive drugs - are still recommended, although clinical trials of varying quality failed to demonstrate any benefit in patient related outcomes.