Cardiac arrest, including but not limited to respiratory and cardiac arrest due to heart disease, drowning, electric shock, etc. Note that transient syncope and seizures are not indications for CPR. Before CPR, determine whether the patient’s breathing and heartbeat are normal, and start CPR only if there is no breathing and heartbeat. 1.Assess the safety of the scene environment Ensure that first aid measures are carried out in a safe environment and do not cause secondary injuries. 2.Identification (1) Determine consciousness: tap the patient’s shoulders with both hands and call out, “Hey! What’s wrong with you?” See if there is a response. (2) Judgment of respiration: Observe whether the patient’s chest is rising and falling, and judge for no more than 10 seconds. (3) Check carotid pulsation: limited to medical personnel, non-professionals can directly start the operation of chest compressions without consciousness and breathing. (3) Chest compressions (C), open airway (A), artificial ventilation (B) Chest compressions should be started before open airway and artificial ventilation (C-A-B) (A-B-C in the old version) to reduce the time delay of the first compressions. (1) C: chest compressions Patient position: lying flat, on a hard bed or on the floor, withdrawing all objects from the head and under the body. Compression site: lower part of the sternum. Key points: the root of the palm of one hand is placed on the compression site, the other hand overlaps it, the fingertips are raised, not touching the chest wall, and the shoulder, elbow and wrist joints are perpendicular to the ground. Adequate rate and amplitude: The recommended rate of chest compressions is 100 to 120 compressions per minute, and the recommended amplitude of chest compressions for adults is at least 2 inches (5 cm) but no more than 2.4 inches (6 cm). It is also important to ensure complete thoracic recoil after each compression to minimize interruption of compressions and avoid hyperventilation. The ratio of the number of chest compressions to artificial respiration is 30:2. (2) A: Open the airway Remove debris and dentures from the mouth first; then use the head-up chin lift method: place the root of the palm of one hand on the patient’s forehead, force the palm backward, and hold the chin with the index and middle fingers of the other hand and lift it so that the tip of the jaw and the earlobe line are perpendicular to the ground. (3) B: Artificial ventilation Out-of-hospital use mouth-to-mouth artificial ventilation: pinch the patient’s nostrils, completely wrap the patient’s mouth after natural inspiration, blow the air into the patient’s lungs, so that the patient’s chest is lifted; after blowing up is complete, release the fingers pinching the nostrils and see the patient’s chest spring back. Balloon mask ventilation can be used in-hospital. The ratio of the number of chest compressions to artificial respiration was 30:2, with 30 chest compressions and 2 artificial respirations as one group. The effectiveness of resuscitation is judged after 5 sets of operation (observation of respiration). Any moment the defibrillator arrives at the scene, a rhythm check should be performed immediately, and if it is a defibrillable rhythm, it should be defibrillated immediately.