Airway Responsiveness In Preschool Children

Objective: Explore the feasibility of clinical application,the standard of positive and safety of doing bronchial provocation test for preschool children. Investigate the incidence of airway hyper-responsiveness among normal preschool children and the difference between asthmatic children .Methods:190 normal healthy children in Guangzhou who aged 4 to 6 were enrolled in this study. Among them, 156 children(80 males, 76 females) complete the Spirometric tests successfully.Spirometric tests were performed using pneumotach spirometer (Jaeger, Germany). By referring to the acceptable curve standard in the joint statement released by American Thoracic Society and European Respiratory Society in 2007, we detected 10 parameters, including forced vital capacity (FVC), forced expiratory volume in 0.5 second (FEV0.5), forced expiratory volume in 0.75 second (FEV0.75), forced expiratory volume in 1 second (FEV1), FEV0.5/FVC, FEV0.75/FVC, FEV1/FVC, maximum mid expiratory flow (MMEF), maximum expiratory flow (PEF), as well as peak inspiratory flow (PIF). All parameters were analyzed by multiple stepwise linear regression, which led to the regression equation. The children who could finish FVC test were all able to complete the methacholine bronchial provocation test. Airway responsiveness of 156 children was examined by methacholine bronchial provocation test so as to investigate the incidence of hyper-responsiveness in normal children as well as the incidence of adverse events. For those who had positive results in bronchial provocation test, we calculated respectively the cumulative amount of inhaled methacholine when FEV0.5, FEV0.75 and FEV1 reached the expected value of decreasing by 15%(PD15FEV0.5,PD15FEV0.75,PD15FEV1, respectively)and the expected value of decreasing by 20% (PD20FEV0.5, PD20FEV0.75, PD20FEV1, respectively). These recorded data including the positive rate, the rate of adverse events and severity compared with that of the wheezing group (children who were already diagnosed as asthma or had medical history of wheezing who age 4 to 6 years old).Result: The once success rate of spirometric tests was 73.16%(139/190), and twice success rate was 82.11%(156/190). During baseline spirometry test, 154 cases completed three acceptable curves, 2 cases completed only two acceptable curves (1 case in 5-year-old group, 1 case in 6-year-old group). Expiratory time for normal children was 1.74±0.62S, of which 7 cases (4.5%) had an expiratory time of less than 1s. The parameters of pulmonary function all increased with age (P <0.01). Comparison of children with the same age but different gender: in 4-year- old, all parameters of boys were higher than that of girls with the exception of FEF, MMEF and PIF,, in 5-year-old group, all parameters of boys except FVC, PEF, PIF, were higher than that of girls (P <0.05), in 6-year-old group, there was no significant difference between boys and girls (P> 0.05). Multiple regression equation of all indicators for lung function was established. The children who could finish FVC test were able to complete the methacholine bronchial provocation test.The total positive rate of bronchial provocation test in normal group was 6.41% while total positive rate of the wheezing group was 92.45%; In the wheezing group, for children who had positive results in bronchial provocation test, their PD20FEV0.5, PD20FEV0.75 and PD20FEV1 were all lower than that of the normal group ( P <0.05). Both showed that the airway hyperresponsiveness (AHR) of wheezing group was significantly higher than that of normal group. Comparison of PD20FEV0.5, PD20FEV0.75 and PD20FEV1 within the normal group and the wheezing group showed no significant difference (P> 0.05). No serious adverse events in provocation test was recorded.Conclusion: It was feasible to measure airway responsiveness of preschool children in China through applying software games and making use of psychological characteristics of children. Methacholine bronchial provocation test has high safety, no severe adverse reaction is recorded. AHR-positive rate and the total positive rate of the wheezing group are significantly higher than that of the normal group. It is an important means for the diagnosis of asthma in children.