What are the criteria for grading lung function?

The classification criteria of pulmonary function are mainly evaluated in two aspects: the first aspect is the evaluation of pulmonary function test, which mainly evaluates the percentage of expiratory volume in the first second to the predicted value, and is divided into mild, moderate, severe and critical degrees. The second assessment is based on the patient's clinical symptoms and risk of exacerbations. If the patient has two or more exacerbations per year and the patient's forced expiratory volume in the first second is less than 50% of the predicted value, it indicates that the patient is a very critical patient.