Pulmonary function measurement
All children were tested for pulmonary function on the day of the physical examination. Pulse oscillations (first) and pulmonary ventilation (second) were also measured. If ventilation function is abnormal, pulse data will not be used. The Masterscreen IOS lung function detector from Yager Company in Germany is adopted and operated by specially trained lung function technicians.
All operations and procedures are in accordance with ATS (American Thoracic Society, ATS), the European Respiratory Society (European Respiratory Society, ERS) and the Chinese children’s lung function testing guidelines recommending [1-4], The specific operations are as follows: 1 minute to collect data, display VT and RF constant volume-time curve, FRC is smooth, the impedance spectrum repeatability is good, Zrs, Rrs, Xrs, and Fres stability, at least three times the acceptable data.