It is usually not necessary to have an empty stomach when having a lung function test. A doctor specialized in doing lung function tests is needed to instruct the examinee how to breathe normally, such as how to inhale and exhale deeply and normally, so as to make the results of the test more accurate and illustrative. It is not advisable to eat too much when doing the lung function test, as overeating can cause gastroesophageal reflux. You need to hold the patient’s nose with a nose clip when doing the pulmonary function test, and be sure to instruct the patient to breathe through the mouth correctly. When doing pulmonary function tests, you must hold the mouthpiece to ensure that there is no air leakage during the test. The success of the lung function test is mainly related to the patient’s cooperation, the better the patient cooperates, the higher the success rate of the test will be. Lung function test is an examination technique that uses specialized medical equipment to detect the airflow rate and airflow rate produced by the respiratory tract during breathing, so as to understand whether the respiratory function is normal or not. Lung function test is used in internal medicine clinical diagnosis, treatment and surgical risk assessment. It can be used to diagnose the site of airway obstruction, assess the nature and degree of lung function impairment, can assist in guiding clinical medication, and can predict the risk of surgery and the ability to recover from surgery, and lung function test is of great practical significance in clinical practice.