Three minutes after the heart stops beating can lead to massive brain cell death, and more than five minutes later can lead to massive cell death in vital tissues such as the brain, heart, and lungs. Under normal circumstances, death in the physiological sense refers to the cessation of breathing and heartbeat, while the ethical reference to death also includes brain death. Brain cells are unable to metabolize anaerobically to meet energy supply and are sensitive to hypoxia. The oxygen and nutrients remaining in the brain cells are only able to last for 1-3 minutes after the blood supply is stopped. Therefore, massive brain cell death can occur if more than 3 minutes elapse. Irreversible brain damage or cerebral edema usually occurs 4 minutes after cardiac arrest. Cardiac muscle cells are more dependent on oxygen and nutrients than brain cells, but they are not maintained for more than 5 minutes. In cardiac arrest, the patient loses consciousness completely, and if resuscitation is not performed immediately, the patient usually enters death within a few minutes.