First, the relationship between the structure and function of the respiratory system and diseases. The respiratory system has the most frequent contact with the external environment among the various systems of the human body and has a large contact area. In the resting state of adults, 12,000L of gas enters and leaves the respiratory tract daily, and 300-750 million alveoli (total area of about 100m2) exchange gas with the capillaries of the pulmonary circulation, taking in oxygen from the external environment and expelling carbon dioxide to the outside of the body. In the process of breathing, organic or inorganic dust in the external environment, including various microorganisms, allergens, dust particles and harmful gases can be inhaled into the respiratory tract and lungs to cause various diseases. Primary infections are most common with viral infections, which first appear in the upper respiratory tract, followed by bacterial infections; exogenous asthma and exogenous allergic alveolitis; pneumoconiosis caused by inhalation of production dust, with silicosis, coal silicosis and asbestosis being the most common; acute and chronic respiratory tract infections and pneumonia can occur with inhalation of irritant gases such as sulfur dioxide, chlorine and ammonia, which are highly water soluble, while Inhalation of low water-soluble gases such as nitrogen oxides, phosgene, and dimethyl sulfate damages the alveoli and pulmonary capillaries and causes acute pulmonary edema. The lungs are supplied by two groups of blood vessels: the arteries and veins of the pulmonary circulation are functional vessels for gas exchange; the bronchial arteries and veins of the body circulation are nutrient vessels for the airways and the dirty pleura. The lungs are connected to the blood and lymphatic circulation of all organs in the body, so the bacterial embolus of skin and soft tissue boils and carbuncles, the thrombus of embolic phlebitis, and the cancer embolus of tumors can reach the lungs and cause secondary lung abscess, pulmonary infarction, and metastatic lung cancer, respectively. Lung cancer of the digestive system, pulmonary lesions can also spread to the whole body, such as lung cancer and tuberculosis to bone, brain, liver and other organs; likewise, focal spread can occur in the lung itself. The vasculature of the pulmonary circulation is also becoming more and more divided from the trachea-bronchus, and the cross-sectional area of the small arteries is large, while the pulmonary capillary bed is larger and easily dilated. Therefore, the lung is a low-pressure (blood pressure in the pulmonary circulation is only 1/10th of the blood pressure in the body circulation), low-resistance, high-volume organ. Interstitial pulmonary edema, or leakage of fluid from the chest cavity, occurs when there is mitral stenosis, left heart failure, cirrhosis, nephrotic syndrome, and hypoproteinemia from malnutrition. Some immune, autoimmune or metabolic systemic diseases such as nodular disease, systemic lupus erythematosus, rheumatoid arthritis, dermatomyositis, and scleroderma can involve the lungs. The lung also has non-respiratory functions, such as endocrine syndrome produced by the production and release of ectopic hormones in lung cancer. Second, the aging of the social population. With the rapid advancement of science and medical technology, the rate of human life span extension has also accelerated rapidly. It is recorded that two thousand years ago the average life expectancy was second only to 20 years, and increased to 30 years in the 18th century, and reached 40 years at the end of the 19th century. According to the United Nations Population Division, the world’s population over 60 years of age will increase to 1.121 billion by 2025, accounting for 13.7% of the world’s population, of which 12% in developing countries and 23% in developed countries. at the end of 1993, the number of elderly people over 60 years of age in Shanghai had exceeded 2.1 million, accounting for 16% of the total population, and by 2025 the number of elderly people will reach 4 million, accounting for more than 28%. Respiratory system diseases such as chronic obstructive pulmonary disease and lung cancer are increasing with age, and their prevalence is also rising; due to the low immune function of the elderly body, and easy to cause inhalation pneumonia, even though a variety of new antibiotics have been introduced, lung infections still rank first in the elderly infectious diseases, often as a direct factor causing death. Third, the hazards of air pollution and smoking. Etiological studies have confirmed that the increase in respiratory diseases and air pollution, smoking is closely related. Some data prove that when the air soot or sulfur dioxide exceeds 1000ug/m3, the acute attack of chronic bronchitis increases significantly; other dust such as carbon dioxide, coal dust, cotton dust, etc. can stimulate the bronchial mucosa, impair lung clearance and natural defense functions, creating conditions for microbial invasion. The higher incidence of lung cancer in industrially developed countries than in industrially backward countries indicates that it is related to the pollution of the atmosphere by carcinogenic substances in industrial waste gas. Smoking is the main source of pollution of the small environment, smoking and chronic bronchitis and lung cancer concerns. 1994 on the World Health Organization proposed smoking is the world’s largest “plague” that causes death, the survey showed that in developing countries in the last half century, smoking devoured 60 million people, 2/3 of them are 45 to 65 years old, smokers than Smokers die 20 years earlier than non-smokers. If the current smoking situation continues, by 2025, the world’s annual death due to smoking will reach 1000 people, three times the current mortality rate, of which China accounts for 2 million people. Now China’s total consumption of tobacco accounts for the world’s first, the obvious increase in smoking among young people, the next 20 years indeed, the death of people due to smoking will increase sharply. Fourth, advances in medical science and applied technology to improve the level of diagnosis. In recent years, the progress of scientific research in various fields such as physiology, biochemistry, immunology, pharmacology, nuclear medicine, laser, ultrasound, and electronic technology has provided conditions for the diagnosis of respiratory diseases. Cellular and molecular biology techniques are now used to gain a new and more comprehensive understanding of the etiology, pathogenesis and pathophysiology of some respiratory diseases, enabling more accurate and early diagnosis of diseases. Fifth, respiratory diseases have not received sufficient attention for a long time. Since the respiratory organs have a huge reserve capacity for physiological functions, only 1/20 of the lung respiratory function is usually needed to maintain a normal life, so the pathological changes of the lung are often not reflected clinically; the symptoms of respiratory diseases such as cough, sputum, hemoptysis, chest pain and shortness of breath lack specificity and are often mistaken by people and clinicians for colds and bronchitis, while the diagnosis of severe pneumonia, tuberculosis or lung cancer and other diseases is delayed. The diagnosis is often delayed due to severe pneumonia, tuberculosis or lung cancer, or due to repeated respiratory infections, which are only taken seriously when they develop into emphysema, pulmonary heart disease and respiratory failure, but it is too late to reverse the pathology and physiological functions.