After approval by NHTMRI-IRB Ethical Committee.All demographic data will be obtained including the patients' age, sex, associated co-morbidities (e.g. diabetes mellitus hypertension), cause of cardiac arrest, and duration of CPR. Resuscitation for patients will be held according to ERC (Advanced life support) ALS Algorithm 2021.1 Electrocardiogram of manual defibrillator, pulse oximeter (Nihon-Kohden, Mindray) will be attached to the middle finger or thumb7 and the capnography will be attached between endotracheal tube and Bag mask valve. Both readings of the ETCO2 and pulse oximeter derived perfusion index will be recorded every minute till the end of CPR.The medical staff did not alter the patient's treatment based on PI results. One week and 30 day survival will be followed.