If the patient’s lips appear purple, we should consider the following reasons: 1. We should consider whether there are factors of poisoning, for example, when there is nitrite poisoning in food poisoning, the lips will be cyanotic. 2. We should consider whether the patient has shock, for example, cardiogenic shock, hypovolemic shock, infectious shock, the patient’s lips will appear cyanotic. 3. Cardiogenic factors, for example, coronary heart disease, unstable angina, myocarditis, pericarditis, etc., the patient’s lips will also appear purple because of insufficient blood supply and oxygen supply to the heart. 4. In cases of angina pectoris, myocarditis, pericarditis, etc., the patient’s lips will also appear purple because of insufficient blood supply and oxygen supply to the heart. 4, Some respiratory system diseases, such as chronic obstructive pulmonary disease, pulmonary hypertension, history of chronic pulmonary heart disease, and severe deficiency of arterial oxygen saturation, the lips will also appear purple.