Chest tightness, medically called dyspnea, refers to the feeling of lack of air and labored breathing, and behaviorally manifests forceful breathing, deep breathing, and in severe cases, open-mouth breathing, sitting breathing, and even blue lips, as well as an increase in the number of breaths and anxiety. This is a very common symptom and has many causes, with respiratory system and cardiovascular system diseases being the most common. Respiratory system: 1, airway abnormalities: throat, trachea, bronchial inflammation, tumors; foreign body-induced airway narrowing or even obstruction, as well as bronchial asthma, chronic obstructive pulmonary disease, etc. 2, lung diseases: lung inflammation (such as pneumonia, tuberculosis), pulmonary atelectasis, pulmonary stasis, pulmonary edema, diffuse interstitial lung disease, and fine bronchoalveolar carcinoma. 3, chest wall, thorax, thoracic cavity diseases: such as chest wall inflammation, severe deformity of the thorax, pleural effusion, pneumothorax, pleural adhesions, trauma, etc. 4, neuromuscular diseases: such as poliomyelitis, polyneuritis optica, myasthenia gravis involving respiratory muscles, and some drugs may also lead to respiratory muscle paralysis. 5, diaphragm movement disorders: such as large amount of peritoneal fluid, huge abdominal tumor, gastric dilatation, pregnancy can limit the diaphragm movement. The above mainly affects the normal ventilation and air exchange function of the body, so that oxygen cannot enter the body or carbon dioxide cannot be eliminated from the body caused by. Circulatory system: various causes of heart failure, pericardial effusion, pulmonary embolism, pulmonary hypertension, etc. Such mainly affect the normal transport of oxygen in the body, resulting in tissue hypoxia causing chest tightness symptoms. Poisoning: such as diabetic ketoacidosis, morphine-based drug poisoning, cyanide poisoning, nitrite poisoning, carbon monoxide poisoning, etc. Toxic substances cause chest tightness by different mechanisms, among which the most common carbon monoxide poisoning is due to carbon monoxide entering the bloodstream and occupying the sites of oxygen transport, so that oxygen cannot reach the body tissues. Neuropsychiatric factors: 1, neurological lesions: brain hemorrhage, brain trauma, brain tumor, encephalitis, meningitis, etc. 2, caused by mental abnormalities: such as hysteria. This category is mostly seen when the disease has affected the respiratory center. Hematological diseases: Commonly seen in severe anemia, methemoglobinemia, sulfated hemoglobinemia, etc. These are mostly due to a decrease in the amount of oxygen carried by the blood. It can be seen that the same symptom does not correspond to a disease, but needs to be identified according to the other symptoms accompanying the chest tightness and the targeted tests, and the treatment varies according to the cause.