Observe the patient’s state during CPR, observe whether the patient’s chest is heaving, whether there is gas coming out of the mouth and nose, tap the patient’s shoulder to see if the patient responds, press the carotid artery to see if there are fluctuations, and determine whether the patient is in respiratory or cardiac arrest. The ABC steps are: A. Keep the airway open, undo the patient’s clothes, fully expose the chest, observe whether there are foreign objects blocking the mouth and nasal cavity, and clean up effectively in time to keep the airway open; B. Mouth-to-mouth artificial respiration, keep the patient’s head up and jaw up. C. Artificial circulation, fold the hands together and press the patient’s lower third of the sternum with the root of the palm, the depth of pressure is 6-8cm, 100-120 times per minute.