There are many causes of dyspnea, mainly respiratory system and cardiovascular system diseases. 1, respiratory system diseases are common in: (1) airway obstruction: such as larynx, trachea, bronchial inflammation, edema, tumor or foreign body caused by narrowing or obstruction and bronchial asthma, chronic obstructive pulmonary disease; (2) lung diseases: such as pneumonia, lung abscess, tuberculosis, pulmonary atelectasis, pulmonary bruising, pulmonary edema, diffuse interstitial lung disease, fine bronchial alveolar carcinoma, etc.; (3) chest wall, thorax, pleural cavity diseases (4) neuromuscular diseases: such as inflammation of the chest wall, severe thoracic deformity, pleural effusion, spontaneous pneumothorax, extensive pleural adhesions, tuberculosis, trauma, etc.; (4) neuromuscular diseases: such as polio lesions involving the cervical medulla, acute polyneuritis optica and myasthenia gravis involving the respiratory muscles, drug-induced respiratory muscle paralysis, etc.; (5) diaphragmatic dyskinesia: such as diaphragmatic paralysis, massive peritoneal effusion, large abdominal tumors, gastric dilatation and pregnancy (5) Diaphragmatic movement disorders: such as diaphragmatic palsy, massive peritoneal effusion, large abdominal tumors, gastric dilatation and pregnancy. (2) Circulatory system diseases are common due to various causes of left and right heart failure, pericardial compression, pulmonary embolism, and primary pulmonary hypertension. 3. Poisoning is caused by various kinds of poisoning, such as diabetic ketoacidosis, morphine drug poisoning, organophosphorus insecticide poisoning, hydride poisoning, nitrite poisoning and acute carbon monoxide poisoning. 4, neuropsychiatric diseases such as cerebral hemorrhage, traumatic brain injury, brain tumor, encephalitis, meningitis, brain abscess and other cranio-cerebral diseases cause respiratory center dysfunction and respiratory distress due to mental factors, such as hysteria. 5, hematological diseases are common in severe anemia, methemoglobinemia, sulfated hemoglobinemia, etc.