The prognosis of cardiac arrest patients is generally poor. Recent studies have showed that the high quality of CPR increases the survival after cardiac arrest. Therefore the investigators planned this prospective observational study to determine the epidemiology of sudden cardiac arrest in the prehospital setting of Tampere area, the quality of the CPR, and also the associations between depth and frequency of chest compressions and invasive arterial pressure, EtCO2,cerebral oxygenation and iatrogenic injuries associated to chest compressions 1) in patients resuscitated out of hospital by emergency medical service's (EMS's) personals and 2) in-hospital by hospital resuscitation team members. In addition, the investigators will analyze the effects of the chosen method of resuscitation on critical vital signs (Etco2 and invasive pressures): closed-chest CPR is compared to open-chest CPR, or mechanical CPR with a device (AutoPulse-CPR, Cardio Pump) compared to manual CPR guided with quality CPR device. The results will give the investigators important insights into the haemodynamics of CPR which may guide future strategies for the management of cardiac arrest. The research group is also interested in CPR related injuries and mattress effect. Quality of life after CA is evaluated among survivals and the cause of death among non-survivors.