Mechanical ventilation is usually used to improve the symptoms of insufficient ventilation when the symptoms of dyspnea are caused by ventilation dysfunction, pulmonary atelectasis, respiratory muscle fatigue and other factors. 1. Ventilation dysfunction: diseases such as chronic obstructive pulmonary disease, bronchial asthma, pneumonia, etc. lead to severe ventilation dysfunction, which may cause hypoxemia or hypercapnia, and the application of mechanical ventilation can improve lung ventilation and air exchange, and establish normal respiratory function. 2. Lung atelectasis: the lungs cannot expand effectively due to tumor disease or pleural effusion, etc. Mechanical ventilation can increase the gas into the lungs and improve the condition. 3. Respiratory muscle fatigue: If increased airway resistance leads to respiratory muscle fatigue, mechanical ventilation can be used to reduce the burden on the respiratory muscles and help them move. Mechanical ventilation can also be used for traumatic brain injury, cerebrovascular accident and poisoning caused by respiratory failure and other diseases, when the patient has weak or impaired spontaneous respiration, abnormal blood gas analysis or acid-base balance imbalance, etc., need to apply mechanical ventilation to avoid aggravation of the condition, it is recommended that the patient, if in discomfort, actively consult the doctor to avoid delaying the condition.