Dyspnea includes inspiratory, expiratory and mixed dyspnea, which is mainly characterized by abnormal respiratory rate and depth, hypoxia, and auxiliary respiratory muscle compensation. 1. Inspiratory dyspnea: mainly manifested in inspiratory phase effort, extreme exertion of respiratory muscles, increased inspiratory amplitude, and in severe cases, the three concave signs (suprasternal fossa, supraclavicular fossa, and intercostal space depression) can be seen, which can be accompanied by a dry cough and inspiratory laryngeal tinnitus. 2. Expiratory dyspnea: the expiratory phase is laborious, slow and prolonged, and may be accompanied by expiratory rales. 3. Mixed dyspnea: both inspiratory and expiratory phases are labored, accompanied by increased respiratory rate and shallow depth. Dyspnea can also be accompanied by cyanosis, increased heart rate, impaired consciousness, shock and other hypoxic symptoms. Some special causes of dyspnea can also have more specific manifestations, such as metabolic acidosis can have deep and long regular breathing. Dyspnea can be caused by chronic obstructive pulmonary disease, pulmonary embolism, left heart failure, neuromuscular junction disease and other respiratory, circulatory, neuropsychiatric disorders, the presence of dyspnea should be timely consultation, identify the cause of the disease and then active treatment.