The causes of breathlessness and dyspnea are mainly respiratory diseases, cardiovascular diseases, poisoning, blood diseases and neuropsychiatric diseases. 1. Respiratory diseases: the most common causes of breathlessness and dyspnea, including lung diseases, such as pulmonary bruising, pulmonary edema and severe acute respiratory distress syndrome; respiratory obstruction, such as laryngeal spasm, tumors and foreign bodies; thoracic movement disorders, such as severe thoracic spinal deformity, pneumothorax and massive pleural effusion. 2. Cardiovascular diseases: such as severe heart failure due to various reasons, such as left heart failure, pericardial effusion, etc. 3. Poisoning: such as diabetic ketoacidosis, morphine poisoning, carbon monoxide poisoning. 4. Blood diseases: such as severe anemia, methemoglobinemia. 5. Neuropsychiatric diseases:Neurological diseases, such as traumatic brain injury, tumor, encephalitis, etc., mental diseases, such as hysteria, etc., can cause breathlessness and dyspnea. There are other causes of breathlessness and dyspnea, patients should consult the doctor in time for early treatment so as not to delay the condition.