In clinical practice, children with asthmatic-related symptoms such as wheezing, cough, and chest tightness should first undergo pulmonary ventilation function examination. When forced expiratory volume in one second (FEV₁) <70%, which indicates obvious airflow restriction or airway obstruction, and bronchodilation test should be performed. However, some children with normal FEV₁ but decreased small airway function may have mild airflow restriction or airway obstruction. In addition, the bronchial stimulation test is complicated, expensive, risky, and more primary hospitals do not have the equipment and personnel conditions to carry out, but the bronchial diastole test for these children can also be positive, which has certain significance for the diagnosis of asthma.

To investigate the necessity of bronchial diastole test in children with normal FEV₁, forced vital capacity (FVC) and FEV₁/FVC but decreased small airway function.

A case-control study was conducted on 180 children with asthma aged 5 to 14 years who had symptoms such as wheezing, coughing and chest tightness and visited the outpatient department of the Third Affiliated Hospital of Zhengzhou University from May 29, 2019 to September 20, 2024. All subjects underwent routine pulmonary ventilation function examination and bronchodilation test, and the results of routine pulmonary ventilation function examination showed that FEV₁, FVC and FEV₁/FVC were normal, but the small airway function was decreased. Subjects were divided into positive group (n=33) and negative group (n=147) with FEV₁ improvement rate≥12% as the positive criterion of bronchodilation test, and the basic data and pulmonary ventilation function indexes of the two groups were compared. The correlation between small airway function index and bronchodilation test was analyzed by Pearson. Receiver operating characteristic (ROC) curve was used to analyze the efficacy of small airway function indicators in predicting positive results of bronchodilation tests.

The forced expiratory flow 50% of vital capacity as a percentage of the predicted value (FEF₅₀%pred), forced expiratory flow 75% of vital capacity as a percentage of the predicted value (FEF₇₅%pred) and maximum mid-expiratory flow as a percentage of the predicted value (MMEF%pred) in positive group were significantly lower than those in negative group (P<0.05). FEF₅₀%pred, FEF₇₅%pred and MMEF%pred were correlated with the results of bronchodilation test (P<0.001). The area under curve (AUC) of FEF₅₀%pred, FEF₇₅%pred and MMEF%pred in predicting positive results of bronchial diastolic tests were 0.733 (95%CI=0.644-0.822) 、0.827 (95%CI=0.756-0.898) 、0.849 (95%CI=0.789-0.909), respectively, and the cut-off values were 66.85%, 50.00% and 63.35%, respectively. The AUC of FEF₅₀%pred combined with FEF₇₅%pred, FEF₅₀%pred combined with MMEF%pred, FEF₇₅%pred combined with MMEF%pred and the combination of the three indexes were 0.859, 0.855, 0.865, 0.865, respectively. The AUC value of positive bronchial diastole test predicted by the combination of the three factors was greater than that predicted by FEF₅₀%pred and FEF₇₅%pred alone (Z=-2.801, -1.994; P=0.005, 0.046).

For children with asthma-related symptoms such as wheezing, chest tightness, and cough, small airway function indicators should be paid attention to even if FEV₁, FVC, and FEV₁/FVC are normal. When FEF₅₀%pred≤66.85% or FEF₇₅%pred≤50.00% or MMEF%pred≤63.35%, the positive result of bronchial diastole test can be predicted to a certain extent, and bronchial diastole test should be actively performed to assist the diagnosis of asthma.

临床中对于有喘息、咳嗽、胸闷等哮喘相关症状患儿首先行肺通气功能检查，当第1秒用力呼气容积（FEV₁）<70%提示存在明显的气流受限或呼吸道阻塞，应行支气管舒张试验，但部分患儿FEV₁正常但小气道功能下降，提示可能存在轻度气流受限或呼吸道阻塞，且进行支气管激发试验较复杂、费用较高、具有一定的危险性、较多基层医院不具备开展的设备和人员条件，但这部分儿童进行支气管舒张试验也可以为阳性，对于哮喘诊断有一定意义。

探讨FEV₁、用力肺活量（FVC）及一秒率（FEV₁/FVC）正常但小气道功能下降患儿行支气管舒张试验的必要性。

选取2019-05-29—2024-09-20就诊于郑州大学第三附属医院门诊的180例5~14岁有喘息、咳嗽、胸闷等症状的哮喘患儿进行病例对照研究。研究对象已行常规肺通气功能检查及支气管舒张试验，且其常规肺通气功能检查结果显示FEV₁、FVC及FEV₁/FVC均正常、但小气道功能下降。以FEV₁改善率≥12%作为支气管舒张试验阳性判断标准分为阳性组（n=33）及阴性组（n=147），比较两组基本资料及肺通气功能指标。采用Pearson相关性分析探讨小气道功能指标与支气管舒张试验结果的相关性。采用受试者工作特征（ROC）曲线分析小气道功能指标预测支气管舒张试验阳性结果的效能。

支气管舒张试验阳性组患儿用力呼出50%肺活量时的瞬间流量占预测值百分比（FEF₅₀%pred）、用力呼出75%肺活量时的瞬间流量占预测值百分比（FEF₇₅%pred）及最大呼气中期流量占预测值百分比（MMEF%pred）均低于阴性组（P<0.05）。FEF₅₀%pred、FEF₇₅%pred、MMEF%pred与支气管舒张试验结果均具有相关性（P<0.001）。FEF₅₀%pred、FEF₇₅%pred、MMEF%pred预测支气管舒张试验阳性结果的曲线下面积（AUC）分别是0.733（95%CI=0.644~0.822）、0.827（95%CI=0.756~0.898）、0.849（95%CI=0.789~0.909），最佳截断值分别为66.85%、50.00%、63.35%；FEF₅₀%pred联合FEF₇₅%pred、FEF₅₀%pred联合MMEF%pred、FEF₇₅%pred联合MMEF%pred及三指标联合预测支气管舒张试验阳性结果的AUC分别为0.859、0.855、0.865、0.865；三指标联合预测支气管舒张试验阳性结果的AUC值大于FEF₅₀%pred、FEF₇₅%pred指标单独预测（Z=-2.801、-1.994，P=0.005、0.046）。

对于存在喘息、胸闷、咳嗽等哮喘相关症状的患儿，即使FEV₁、FVC及FEV₁/FVC正常，仍需关注小气道功能指标，当FEF₅₀%pred≤66.85%或FEF₇₅%pred≤50.00%或MMEF%pred≤63.35%时可预测支气管舒张试验阳性结果，应积极行支气管舒张试验以辅助哮喘诊断。