The main function of the lungs is to perform gas exchange, sending oxygen from the air into the venous blood and expelling carbon dioxide from the venous blood. In addition to this function, the lungs also have the function of participating in metabolism, filtration, blood storage and so on. Because of the strong compensatory capacity of human lung function, under normal circumstances, one side of the lungs of young people can meet the normal physiological needs of the human body, so lung function damage is often difficult to another person to detect, even if the lung function damage has reached a certain level, patients often do not feel. Because of this, the clinical value of pulmonary function measurement is very great, and its clinical applications include: exploring the pathogenesis of diseases, understanding the nature and extent of pulmonary impairment caused by chest or extrathoracic diseases, assisting in the diagnosis of diseases, evaluating the efficacy of treatment of chest or extrathoracic diseases, evaluating the safety of childbirth or surgery and predicting postoperative pulmonary function, guiding the rehabilitation of diseases, monitoring critical resuscitation, and workforce identification. etc. With the advent of an aging population in Shanghai, pulmonary function measurements are playing an increasingly important role in assessing surgical risk, determining whether patients can tolerate general anesthesia, what surgical procedures they can tolerate, whether they can survive the perioperative period, and evaluating postoperative rehabilitation. For COPD and bronchial asthma, regular pulmonary function tests are necessary, especially for COPD patients with progressive asthma, at least twice a year to assess the severity of the disease and to guide the clinical use of medication, as well as to determine the prognosis of the disease treatment.