Abstract:

Objective To investigate the value of Expiratory time constant（RCEXP）in the measurement of routine ventilatory pulmonary function test of school⁃aged children. Methods A total of 442 school⁃aged children received routine pulmonary function measurements in the Third Affiliated Hospital of Zhengzhou University，Luohe Second People′s Hospital and Luoyang Maternal and Children Health Hospital between August 2018 and August 2020 were selected. RCEXP differences between sexes，ages，and heights were investigated，and RCEXP values were calculated between groups with normal lung function and groups with various airway obstructions. Furthermore，the corresponding ROC curves were created. The relationships between RCEXP and pulmonary function parameters were investigated. Results RCEXP of girls was significantly lower than that of boys（P < 0.001），RCEXP of younger age group was significantly lower than that of older age group（P < 0.05），and RCEXP of lower height group was signifi⁃ cantly lower than that of higher height group（P < 0.05）；The RCEXP of girls was significantly lower than that of boys. The RCEXP of low age group was significantly lower than that of high age group and the RCEXP of low height group was significantly lower than that of high height group（P < 0.05）；RCEXP in the normal group was significant⁃ ly lower than that in the airway obstruction group（P < 0.001），and the cutoff value of RCEXP was 0.436. RCEXP in the normal group was significantly lower than that in the large airway obstruction group（P < 0.001），and the cutoff value of RCEXP was 0.575. In addition，RCEXP in the normal group was significantly lower than that in the small airway obstruction group（P < 0.001），and the cutoff value of RCEXP was 0.434；RCEXP was negatively correlated with FEV1/FVC%. Conclusion High RCEXP in school⁃aged children suggests airway obstruction. Airway obstruc⁃ tion，large airway obstruction，and minor airway obstruction were indicated by RCEXP values greater than 0.436 s，0.575 s，and 0.434 s，respectively. 

Key words:

RCEXP, school ? aged children, pulmonary function, airway obstruction, application value