Dyspnea, or difficulty breathing, can be caused by lung disease, airway obstruction, or circulatory disease. 1. Lung diseases: when there are many lung diseases such as pneumonia, lung abscess or pulmonary atelectasis, the lung function will be impaired, which will make the gas unable to enter the lungs normally, and the patient will have the symptom of tightness of breath and dyspnea. 2. Airway obstruction: the presence of bronchial inflammation, edema or tumors and other diseases will lead to airway obstruction, and also prone to the above symptoms. 3. Circulatory diseases: circulatory diseases such as cardiopulmonary embolism or pulmonary embolism can lead to abnormal gas exchange and induce the symptoms mentioned above. Difficulty in breathing can also be caused by other reasons. Patients should go to the respiratory medicine department of the hospital in time and choose appropriate methods to control the symptoms.