Pulmonary Ventilation Function (PVF) is a test to determine whether there is a decrease in lung capacity and whether there is obstruction of the large airways and the small airways. 1. Lung volume: Lung volume is one of the basic indicators of pulmonary ventilation, which can determine whether there is an abnormal decline in lung volume. 2. Large airway obstruction: when large airway obstruction occurs, it will be shown on the graph of pulmonary function test, and may require further evaluation by CT, bronchoscopy and other related tests. 3. Small airway obstruction: when small airway obstruction occurs, there will often be obstructive ventilatory function changes, which can be interpreted by the report of pulmonary function. To summarize, pulmonary ventilation examination is one of the main items of pulmonary function test, which is valuable in determining the patient’s condition. There are other items in pulmonary function test, such as diffusion function, bronchodilator test, etc., which need to be selected by professional doctors according to the condition.