Pulmonary embolism (PE) is a clinical and pathophysiological syndrome of pulmonary circulatory impairment due to blockage of the main trunk or branches of the pulmonary artery by emboli generated from various causes. It is a common acute fatal cardiovascular disease characterized by high morbidity, misdiagnosis, mortality, and recurrence rates. In the United States, it is one of the three most common cardiovascular diseases with an annual incidence of 600,000 to 650,000 cases, second only to coronary heart disease and tumors, and ranks 3rd among all causes of death with more than 100,000 deaths per year. 70% of thrombus emboli causing pulmonary embolism come from lower limb veins and pelvic vein thrombus, and a few from upper limb, head and neck veins. After the pulmonary artery or its branches are blocked, through the effect of mechanical blockage and neurohumoral factors, it can lead to increased resistance of pulmonary circulation, elevated pulmonary artery pressure and disproportionate ventilation and blood flow, and then cause a series of changes such as right heart insufficiency and reduced blood pressure of body circulation, bruising, severe hypoxemia, etc. In serious cases, pulmonary infarction and pulmonary atrophy can occur, which can damage the function of heart, brain, kidney and other important organs, and even sudden death. There are many causes that can induce pulmonary embolism, mainly include: 1. Blood stagnation. Paralysis, long-term bed rest, immobilization of limbs, etc. can slow down the blood flow, and the muscle pump function of the lower limbs disappears, which induces thrombosis. 2, vascular injury. Such as venipuncture, surgical injury to blood vessels and chemical injury such as infusion of various irritating or hypertonic solutions. 3, the hypercoagulable state of blood. Surgery, trauma, myocardial infarction, atrial fibrillation and other activation of coagulation mechanisms lead to blood hypercoagulation. 4, Obesity, pregnancy, oral contraceptives, elderly patients, diabetes mellitus, thrombocytosis, connective tissue disease, etc. interfere with the balance of coagulation and hemolysis, leading to the development of venous thrombosis. The clinical manifestation of typical pulmonary embolism is the triad of “dyspnea, chest pain and hemoptysis”, but the incidence is less than 30%. The common symptoms are dyspnea, chest pain, hemoptysis, syncope, cough, chest tightness, shortness of breath and sudden death, which cannot be explained by other reasons.