On any occasion, when encountering a critically ill person, it seems logical to immediately dial “120” and call the medical emergency center for help. However, for patients with sudden cardiac death (i.e., sudden cardiac arrest), even if the emergency vehicle arrives at the scene in a hurry, it is often too late. Because of the data analysis, 12.8% of the patients who caused sudden cardiac death were acute myocardial infarction, 11.7% were coronary thrombosis, 8.8% were a combination of the above two causes, and the rest were of unknown origin. However, regardless of the cause of sudden death, the basic lesion is ventricular fibrillation, ventricular arrest or separation of electrical and mechanical activity of the heart, as a result of which the cardiac blood displacement is reduced, and the organs most seriously affected by it are the coronary arteries with reduced perfusion and the brain and kidneys, where the urgent need to restore the blood oxygen supply is in the brain tissue. As experience shows, under normal circumstances, once the brain is deprived of blood and oxygen for 5-6 minutes, irreversible damage can be caused. For this reason, every second must count for a patient with sudden cardiac death. Even an ordinary person should have the initial knowledge of first aid and perform on-site “CPR”, which is the key to saving the patient’s life. In recent years, in some countries, the technique of on-the-spot first aid for sudden cardiac death has been widely promoted and popularized among firefighters, police officers, high school students, salesmen and service workers, and has achieved remarkable results. How to determine sudden cardiac death? The following points are the main basis: ① the patient suddenly fainted, loss of consciousness or first brief convulsions; ② whistling stopped, the root of the neck can not feel the vascular pulsation; ③ pale or purple face; ④ pupils (i.e., the black part of the eye) dilated. The practice of on-site cardiac resuscitation is: the patient is immediately flattened on the ground or a hard bed, remove the dentures in the mouth and other things, such as one person resuscitation, first in the patient’s precordial area with a fist root fierce 1-2 times, then the rescuer will straighten both arms, the root of the right hand on the patient’s sternum on the junction of the upper 2 / 3 and lower 1/3, the left hand flat on the back of the right hand, using the strength of both shoulders and upper body to The patient’s crest is squeezed in the direction of the crest, and the squeezing force is appropriate to press the sternum down 3-4 cm deep, at a rate of 80 times per minute. Pressing the heart at the same time, but also mouth-to-mouth inhalation, the method is: the operator one hand behind the patient’s neck to raise the neck, the other hand pinch the patient’s nostrils, and then inhale, the mouth to the patient’s mouth (do not leak air), slowly and evenly blow into the number of heart compressions and mouth-to-mouth blowing ratio is 10 to 2. If two people operate at the same time, one person squeeze the heart 5 times, the other mouth-to-mouth blowing 1 time. The above CPR should be performed consistently. The indicators of successful resuscitation are: ① the patient begins to stir or struggle; ② large blood vessels can be felt pulsating, skin bruising improves; ③ the patient itself appears to whistle. At this point, cooperate with the medical personnel of the first aid station and continue to rescue or send to the hospital for further treatment.