Abstract：
The aim of the present study was to define an initial angle called β and to assess its diagnostic value for identifying poor-quality maneuvers in spirometry testing in children. Furthermore, its predictive equation or normal value was explored. Children aged 4-14 years with respiratory symptoms who underwent spirometry were enrolled. Based on the efforts labeled during maneuvering and the quality control criteria of the guidelines, children were categorized into good-quality and poor-quality groups. According to ventilatory impairment, children in the good-quality group were divided into three subgroups: normal, restricted, and obstructed. Angle β was the angle between the line from the expiratory apex to the origin of coordinates and the x-axis of the maximal expiratory flow-volume (MEFV) curve. Demographic characteristics, angle β, and other spirometric parameters were compared among groups. The diagnostic values of angle β, forced expiratory time (FET), and their combination were assessed using receiver operating characteristic curves. Data from 258 children in the good-quality group and 702 healthy children in our previous study were used to further explore the predictive equation or normal value of angle β. The poor-quality group exhibited a significantly smaller angle β (76.44° vs. 79.36°; P < 0.001), significantly lower peak expiratory flow (PEF), FET, and effective FET (ETe), and significantly higher expiratory volume at peak flow rate (FEV-PEF) and ratio of extrapolated volume and forced vital capacity (EV/FVC) than the good-quality group. There was no significant difference in angle β among the normal, restricted, and obstructed groups. Logistic regression analysis revealed that smaller angle β and FET values indicated poor-quality MEFV curves. The combination of angle β < 74.58° and FET < 4.91 s had a significantly larger area under the curve than either one alone. The normal value of angle β of children aged 4-14 years was 78.40 ± 0.12°. Conclusions: Angle β contributes to the quality control evaluation of spirometry in children. Both angle β < 74.58° and FET < 4.91 s are predictors of poor-quality MEFV curves, while their combination offers the highest diagnostic value. What is Known: • A slow start is one of the leading causes of poor-quality maximal expiratory flow-volume (MEFV) curves, which is a particularly prominent issue among children due to limited cooperation, especially those younger than 6 years old. • It is relatively difficult to differentiate between ventilatory dysfunction and poor cooperation when a slow start occurs in children; therefore, there is an urgent need for an objective indicator that is unaffected by ventilatory impairment to evaluate quality control of spirometry. What is New: • The initial angle β, which was introduced at the ascending limb of the MEFV curve in the present study, has a certain diagnostic value for poor-quality MEFV curves in children. • Angle β < 74.58° is a predictor of poor-quality MEFV curves, and its combination with FET < 4.91 s offers a higher diagnostic value.
摘要：
本研究的目的是定义一个称为β的初始角度，并评估其诊断价值，以识别儿童肺活量测定测试中的劣质动作。此外，探讨了其预测方程或正常值。纳入4-14岁有呼吸道症状并接受肺活量测定的儿童。根据机动期间标记的努力和指南的质量控制标准，儿童被分为质量好和质量差的组.根据通气障碍，优质组的儿童分为三个亚组：正常，受限制,和阻碍。角度β是从呼气顶点到坐标原点的线与最大呼气流量-容积（MEFV）曲线的x轴之间的角度。人口特征，角度β,和其他肺活量测定参数进行组间比较。β角的诊断值,用力呼气时间(FET),并使用受试者工作特征曲线评估它们的组合。我们先前研究中来自优质组258名儿童和702名健康儿童的数据被用于进一步探索角度β的预测方程或正常值。劣质组表现出明显较小的角度β（76.44°与79.36°;P<0.001),显著降低峰值呼气流量(PEF)，FET,和有效FET(ETe)，峰值流量时的呼气量（FEV-PEF）以及外推容量和用力肺活量的比率（EV/FVC）明显高于优质组。正常之间的角度β没有显着差异，受限制,阻挠团体。Logistic回归分析显示，较小的角度β和FET值表明MEFV曲线质量较差。角度β<74.58°和FET<4.91s的组合具有比任一单独的曲线下显著更大的面积。4～14岁儿童β角正常值为78.40±0.12°。结论:β角有助于儿童肺活量测定的质量控制评价。角度β<74.58°和FET<4.91s都是低质量MEFV曲线的预测因子,而它们的组合提供了最高的诊断价值。缓慢启动是导致不良质量最大呼气流量-容积(MEFV)曲线的主要原因之一,由于合作有限，这是儿童中一个特别突出的问题，尤其是6岁以下的人。•当儿童开始缓慢时，很难区分通气功能障碍和合作不良；因此，迫切需要一种不受通气损害影响的客观指标来评估肺活量测定的质量控制。新增内容：•初始角度β，在本研究中，它被引入MEFV曲线的上升分支，对儿童MEFV曲线质量差具有一定的诊断价值。•角度β<74.58°是低质量MEFV曲线的预测指标，其与FET<4.91s的组合提供了更高的诊断价值。
