Half a month before the Spring Festival of the Yangtze River, 55-year-old Sun took a train from overseas to her hometown in Anhui Province to prepare for the New Year. After getting off the train, she suddenly felt chest tightness and discomfort, and was treated with intravenous fluids at a local clinic for “bronchitis”, which she felt was not serious and ignored. During the Spring Festival, the chest tightness suddenly increased, and she could not lie down and was sweating profusely. After emergency thrombolysis, anticoagulation and other treatments, she was brought back from the death line and was recently discharged from the hospital. Why did Sun’s sister have a serious pulmonary embolism? After a thorough examination, the doctor did not find any underlying disease that led to thrombosis. After a detailed medical history, it was learned that Sun had taken the train for more than 20 hours continuously before the onset of the disease and had hardly done any activities during the period. It turned out that the lower extremity vein thrombosis occurred because of the long time sitting in the car, and the embolus was dislodged and brought to the lung by the return blood, which caused a serious pulmonary embolism. Such a thing, in fact, is not the first time to happen. As early as 1954, scholars discovered and reported cases of lower extremity venous thrombosis during prolonged air travel, and in 1988, the term “economy class syndrome” began to be used specifically to describe this phenomenon. Later, it was discovered that it occurs not only in long flights, but also in long car rides (trains, automobiles, etc.). It turns out that the human body will occur in the case of prolonged sitting venous blood stagnation, lower limb venous blood flow rate and blood flow can be reduced by 2/3, and therefore easy to lead to thrombosis. Experts remind: long-distance travel sedentary will increase the risk of lower limb thrombosis. In order to prevent thrombosis, the following measures should be taken: get up and walk every hour during long-distance flights. If traveling by car, stop and walk several times every hour. Move appropriately: Raise your toes up and down. Flex and rotate your ankles or squeeze your calves toward the front seat. Flex and stretch your thigh muscles. Drink plenty of water before and during the trip. Dehydration promotes blood clot formation. Wear medical compression stockings to improve circulation, if necessary, as recommended by your physician. Pulmonary embolism is a collective term for a group of disorders of the pulmonary circulation caused by blockage of the pulmonary arteries by foreign emboli. The main cause of pulmonary thromboembolism is deep vein thrombosis. Pulmonary embolism usually presents as a sudden onset of dyspnea and has a high morbidity and mortality rate but is difficult to diagnose. The mortality rate of untreated pulmonary embolism is 25-30%, while the mortality rate can be significantly reduced with timely diagnosis and treatment. Prevention should be taken into account in high-risk groups. For example, post-fracture or surgical operation, long-term bed-ridden for various reasons, patients with malignant tumors, and people who are sedentary for a long time.