Cardiac arrest is a cardiology emergency with three main features: first, loss of consciousness, you can tap the patient’s shoulder with both hands and call out to the patient, if there is no response to the behavior, consider the heart to have stopped beating. Second, arterial pulsation, mainly by touching the large arteries on the body surface, commonly used is the carotid artery, you can use the laryngeal node as a positioning mark, slide 2-3cm down to the side, and touch the pulsation of the carotid artery with the index and middle fingers, if it is not touched, it means the heart may stop beating. Third, breathing, you can use the ear close to the patient’s nostrils to feel whether there is airflow, and observe whether the thorax is undulating, so as to determine whether the patient is breathing. The above process should be completed within 10s, and if it is determined to be cardiac arrest, CPR should be performed immediately to save the patient.