The clinical manifestations of cardiac arrest are as follows: 1, unconsciousness: the patient is unconscious and should not be called; 2, no aortic pulsation: the carotid artery or femoral artery pulsation can not be felt; 3, no respiration or weak respiration, sighing respiration; 4, pupil dilatation, or even dilated pupils appear to be fixed, no reflex to the light, or a weak reflex to the light. In practical application, the doctor to determine the cardiac arrest method includes judging consciousness, judging the large artery pulsation, judging the respiratory situation, if determined to be cardiac arrest, need to carry out emergency cardiopulmonary resuscitation.