There are many causes of dyspnea, commonly found in respiratory system diseases, cardiovascular system diseases, poisoning, blood diseases, neuropsychiatric factors and so on. 1. Respiratory system diseases: lung diseases, such as pneumonia, pulmonary stasis, interstitial pulmonary fibrosis, severe acute respiratory distress syndrome, etc.; respiratory obstruction, such as laryngeal inflammation, tumor or foreign body obstruction; thoracic obstruction diseases, such as severe thoracic deformity, large amount of pleural effusion, etc., will cause respiratory distress. 2. Cardiovascular system diseases: severe heart failure caused by various reasons, such as left heart failure, pericardial tamponade, pulmonary hypertension, etc. can cause dyspnea. 3. Poisoning: such as uremia, diabetic ketoacidosis, morphine poisoning, etc., can cause severe dyspnea, respiratory depression and so on. 4. Blood diseases: such as severe anemia, methemoglobinemia, etc., hemoglobin oxygenation is insufficient, thus leading to dyspnea. 5. Neuropsychiatric factors: such as cerebral hemorrhage, brain tumor compression, traumatic brain injury, hysteria and so on will also appear dyspnea. There are many causes of dyspnea, patients should go to the hospital in time to identify the cause of the disease, under the guidance of the doctor for treatment.