Indications: Recurrent cough or wheezing; cough lasting more than 2-3 weeks and ineffective antibiotic treatment; recurrent “cold” developing in the lower respiratory tract for more than 10 days; evaluation of the condition of children with asthma; acute attacks of choking, hoarseness, dyspnea; early differentiation of acute bronchitis, pneumonia and asthma in infants and children; other Respiratory diseases. Contraindications Large hemoptysis, pneumothorax, giant alveoli within the last week and not ready for surgical treatment; unstable cardiac function; laryngeal or vocal cord edema. Characteristics of pulmonary function in children 1. varies by age, easy to cooperate over 10 years old, better cooperation at 7-9 years old, partial cooperation at 6-7 years old, more difficult to cooperate at <5 years old; 2. large variability (poor repeatability), may require multiple examinations. Importance of pulmonary function tests for children with asthma 1. Timely diagnosis. If a child has the following problems, he or she should seek medical attention and undergo pulmonary function tests: (1) recurrent cough and wheezing; (2) unexplained dyspnea; (3) chronic cough, especially at night; (4) exercise intolerance or induced cough; (5) cough or wheezing caused by climate change or cold air exposure; (6) recurrent or slowly absorbed bronchitis or pneumonia, etc. 2. Condition assessment and testing.