Coma caused by cardiac arrest can be revived at that time if resuscitation is timely. Patients who are not resuscitated in time will be in a coma for a longer period of time and may even be brain dead. Cardiac arrest causes insufficient blood supply to the brain, and the severity of brain damage is related to the duration of ischemia. If cardiopulmonary resuscitation (CPR) is performed early after cardiac arrest, the duration of cerebral hypoxia is relatively short, the brain damage is relatively mild, and the patient may wake up within a short period of time after resuscitation. After cardiac arrest if resuscitation in time, the brain oxygen deprivation time is long, the patient wake up time will be significantly longer, and may even cause permanent death, difficult to wake up, and may even develop into a vegetable. Patients who have suffered cardiac arrest should be resuscitated in a race against time, and early CPR should be performed to restore the blood supply to the brain as soon as possible to avoid brain death.