Small airway dysfunction (SAD) widely exists in different stages of childhood asthma, which is based on airway inflammation, airway remodeling and airway hyperresponsiveness. Among them, airway inflammation is the main pathological feature of SAD. It has been recently found that immune cells involved in the progression of the disease, such as type 2 innervate lymphoid cells (ILC2s), macrophages, and granulocyte, played an important role in clinical control and targeted therapy of asthma. At the same time, with continuous improvement of clinical detection technologies such as impulse oscillometry and exhaled nitric oxide detecting, more and more evidence suggests that SAD is associated with the early occurrence and development of pediatric asthma. The development of ultra-fine particle aerosol and monoclonal antibody targeting small airways has provided a new means for the precise control of asthma. Therefore, the function of small airways in chronic respiratory diseases, including asthma, has received extensive attention in recent years. Previous studies have shown that SAD increases the risk of uncontrolled asthma in children, but it is often ignored. This article describes the latest research progress of SAD and childhood asthma from the aspects of pathogenesis, diagnostic evaluation and treatment, so as to provide a new perspective and understanding for long-term asthma management targeting small airways.
ZHU Siyu, DONG Xiaoyan. New insights in small airway dysfunction of childhood asthma. Journal of Shanghai Jiao Tong University (Medical Science)[J], 2023, 43(4): 500-506 doi:10.3969/j.issn.1674-8115.2023.04.014
第一秒用力呼气量（forced expiratory volume in first second，FEV1）通常作为评估气道高反应性的指标。英国胸科协会（British Thoracic Society，BTS）发布的指南和全球哮喘防治创议（Global Initiative for Asthma，GINA）等也将其作为哮喘和与其他呼吸系统疾病鉴别诊断的重要指标，但是其在个体间的变异性限制了其应用［37］。临床研究［38］表明哮喘患儿小气道功能下降程度与气道高反应性的严重程度密切相关。最大呼气中期流量（maximal mid-expiratory flow curve，MMEF）能够预测气道高反应性的发生，其降低出现在FEV1改变之前，对气道阻塞更敏感，可反映哮喘早期小气道功能及预后情况［39］。
3 小气道功能评估在儿童哮喘诊断中的意义
常规肺通气法在评价儿童小气道功能中应用最广，一般认为用力呼出50%肺活量的呼气流量（forced expiratory flow at 50% of FVC exhaled，FEF50）、FEF75、MMEF反映小气道功能，最大呼气流量（peak expiratory flow，PEF）、FEF25反映大气道功能。研究［40］表明，急性哮喘患者大小气道功能均存在异常，PEF、FEV1等大气道指标轻中度降低，FEF50、FEF75等小气道指标中重度降低，并且哮喘发作程度越严重，小气道功能指标降低越显著。一项回顾性研究［41］表明，MMEF是反映哮喘患者SAD的敏感指标，且低MMEF与哮喘严重程度增加相关，并且可能是儿童哮喘症状持续存在的风险因素。由于大气道阻塞在哮喘缓解期可缓解，MMEF等小气道指标更有助于提示气道阻塞情况，可用于儿童哮喘缓解期的病情监测。但对于部分控制良好的哮喘患儿，如仍有小气道功能异常要注意鉴别其他原因引起的小气道功能下降［42］。
The relevant literature was collected and analyzed by ZHU Siyu.The first version of the manuscript was written by ZHU Siyu. The revision of the manuscript was reviewed and guided by DONG Xiaoyan. Both authors have read the last version of paper and consented for submission.
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COMPETING INTERESTS
Both authors disclose no relevant conflict of interests.
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