Perhaps you have seen this report: a stroke patient recuperating in bed, his condition improved and began to get up and move around, but suddenly fainted when he got up to go to the toilet, and then never woke up. You may wonder why a good person would do that. Was it because he had another stroke? Or is it because of a heart attack? In fact, the most likely cause of the tragedy is a pulmonary embolism. The official name of pulmonary embolism is pulmonary artery embolism. After the venous blood of the whole body reaches the right atrium and right ventricle, it is pressed into the pulmonary artery, and then flows through the alveoli through the pulmonary artery branches and then enters the body circulation system through the pulmonary vein, left atrium and left ventricle. Therefore, the pulmonary artery is an essential route for blood circulation. Once blocked, blood will also be unable to enter the pulmonary circulation from the right heart system, and will also be unable to enter the left heart and body circulation, and the patient will suffer from severe hypotension and hypoxia, and even cardiac arrest. Since pulmonary embolism comes suddenly, the patient is often gone in a flash, and the success rate of resuscitation is very low. Even if the acute pulmonary embolism occurs in the hospital, the success rate of resuscitation is very low because there is no effective first aid method. According to the relevant clinical data, the mortality rate of untreated pulmonary embolism is up to 30% or more, and the mortality rate of active resuscitation is still 2-8%. So why do you get hit even if you are lying down properly? This is actually related to the characteristics of human venous circulation. The human body’s venous circulation pressure is very low, by the heart’s suction back to the heart is actually very difficult, so a large part of the venous return of the lower extremities is by the lower extremity muscle contraction when the pressure (that is, muscle pump action). When bed-ridden and sedentary for a long time, a lot of blood stays in the veins of the lower limbs. Blood that is not flowing tends to grow clots. If the blood flows again at this time, the clot may enter the pulmonary artery and cause a pulmonary embolism. In fact, not only bedridden patients with stroke, but also many bedridden patients after major surgery and orthopedic bedridden patients are at high risk. In addition, some patients with high coagulation status, such as tumor patients, maternal patients, oral contraceptive patients, etc. are also prone to deep vein thrombosis and pulmonary embolism. In addition, some sedentary people are also at risk. For example, if a person is sedentary on an intercontinental flight, he or she may develop a blood clot in the lower extremity, which may suddenly cause a pulmonary embolism. I have also encountered cases of pulmonary embolism caused by sitting still for long periods of time in a home workshop. So how to prevent pulmonary embolism? 1. Try to avoid prolonged bed rest or prolonged sitting. If you really need to stay in bed for a long time, you should do some movements that can contract the muscles of the lower limbs regularly. If you can’t even do this, then having a chaperone massage the lower extremity muscles (from far to near) regularly can also improve the venous return to the lower extremities. 2. Improve blood pressure hypercoagulability. Avoid some medications that cause hypercoagulation, such as oral contraceptives. Some patients should consider using some anticoagulants, such as heparin, low molecular heparin, warfarin, dabigatran, rivaroxaban, etc. For patients at high risk of pulmonary embolism, if they have sudden onset of chest tightness, chest pain, shortness of breath, etc., they should seek prompt medical attention, which can reduce the risk of death.