How long to wear non-invasive ventilator for each day of hospitalization for chronic obstructive pulmonary disease cannot be generalized, and it should be decided by the severity of respiratory failure, whether the causative factors of acute exacerbation of chronic obstructive pulmonary disease are under control or not, and the lung function of the patient. 1. Degree of respiratory failure: patients with chronic obstructive pulmonary disease are often hospitalized with different degrees of respiratory failure, and the results of blood gas analysis can be used to determine the existence of respiratory failure, such as patients with PO₂＜60mmHg, PCO₂＞50mmHg, there is type II respiratory failure. A noninvasive ventilator can be used when severe hypoxemia and/or carbon dioxide retention is present. 2. Triggers: Hospitalization of patients with COPD is mostly due to acute exacerbation, and the trigger is mostly lung infection. If the lung infection is controlled, the respiratory function can be improved and the duration of ventilator use can be gradually reduced. 3. Lung function: patients with COPD need to wear a ventilator for a longer period of time if their basic lung function is poor. The length of time a patient with COPD should wear a ventilator should be determined by the patient’s condition, and it is recommended to use the ventilator in accordance with the doctor’s instructions.