The brain can function for some time after the heart stops, but not for very long. The weight of the brain is about 2% of the body weight, but about 15% of the blood from the heart to the aorta is supplied to the brain, and the total blood flow for 24 hours is about 2000 ml. The amount of oxygen taken by the brain from the blood is very high, and the total oxygen consumption accounts for 25% of the whole body oxygen consumption, such high oxygen consumption, once the heart stops beating the brain blood flow is suddenly interrupted, the brain can barely function within 10 seconds, more than 10 seconds the brain will stop functioning, the patient will show a sudden loss of consciousness, and then within 4-6 minutes, the brain cells will appear edema and degeneration, during this period if If CPR and other resuscitation measures are carried out in time, the brain cells may return to normal function and the brain may also resume operation. If this time is missed, it will cause irreversible death of brain cells and it will be difficult to restore the brain to function.