Most respiratory diseases have coughing and sputum symptoms. Sputum can be grayish-white mucus sputum or yellowish-green pus sputum, and sometimes coughing up sputum with bright red blood is called hemoptysis. In medical science, bleeding from the trachea, bronchus or lung tissue below the larynx and expelled from the body by coughing is called hemoptysis. The mechanisms of hemoptysis are mainly the following: 1. Increased vascular permeability Due to infection, poisoning or vascular embolism in the lung, pathogens and other products can produce direct damage to the microvasculature or increase the permeability of the microvascular wall through the action of vasoactive substances, and red blood cells enter the alveoli from the dilated microvascular endothelial cells and create small amounts of hemoptysis. 2.Vascular wall erosion and rupture Chronic infection of the lung causes damage to the elastic fibers of the vessel wall, resulting in the formation of small arterial hemangiomas. 3, pulmonary intravascular pressure increase rheumatic heart jaundice with valve stenosis, pulmonary hypertension, high blood grave heart disease and other cases of pulmonary intravascular pressure increase, can cause blood extravasation or small blood vessel rupture and cause hemoptysis. 4, hemostasis, coagulation dysfunction Common in thrombocytopenic purpura and other blood disorders, received in the coagulation factor defects or coagulation process disorders and poor vascular contraction and other factors, on the basis of systemic bleeding tendency may also appear hemoptysis. 5, mechanical injury Trauma or calcified foci of tuberculosis, mechanical injury to blood vessels by bronchial stones cause hemoptysis.