The accumulation of blood in the pleural cavity is called hemothorax, and the accumulation of blood and air at the same time is called hemopneumothorax. Hemothorax is very common in patients with chest trauma. Bleeding can come from intercostal blood vessels, intrathoracic blood vessels, lung lacerations, or trauma to the heart and large blood vessels in the chest. The amount of hemothorax depends on the size of the ruptured blood vessels, the level of blood pressure, and the duration of bleeding. Most of the bleeding in lung tissue is caused by the broken ends of the rib fractures piercing the pleura and lungs. Because the ruptured blood vessels are small and the blood pressure in the pulmonary circulation is low, the bleeding site can often be closed by blood clots and stop by itself, and the amount of bleeding is generally not much. When the intercostal artery or internal thoracic artery ruptures, the bleeding is not easy to stop by itself due to the high blood pressure in the systemic circulation arteries, and the amount of bleeding is relatively large. When the heart or large blood vessels in the chest such as the aorta and its branches, the superior and inferior vena cava, and the pulmonary artery and vein rupture, the amount of bleeding is large and the injury is serious. The patient often dies of shock due to massive blood loss in a short period of time.