Nicholas School of the Environment, Duke University, Durham, North Carolina.
Department of Pediatrics, Shanghai General Hospital, Shanghai Jiao Tong University, Shanghai, China.
JAMA Pediatr. 2020 Jun 1;174(6):533-542. doi: 10.1001/jamapediatrics.2020.0140.
Fine particles (particulate matter 2.5 μm [PM2.5]), a ubiquitous air pollutant, can deposit in the small airways that play a vital role in asthma. It appears to be unknown whether the use of a PM2.5 filtration device can improve small airway physiology and respiratory inflammation in children with asthma.
To discover what pathophysiological changes in the small airways are associated with using a PM2.5-removing device in the bedrooms of children with asthma.
DESIGN, SETTING, AND PARTICIPANTS: Children with mild or moderate asthma were enrolled in this double-blind, crossover study. The participants used a true filtration device and a sham filtration device in their bedrooms in a random order for 2 weeks each with a 2-week washout interval. The study was conducted in a suburb of Shanghai, China, during a low-ozone season.
Ozone and PM2.5 were measured inside bedrooms and outside a window.
Impulse oscillometry, spirometry, and fractional exhaled nitric oxide were measured at the beginning and the end of each intervention. Peak expiratory flow was measured twice daily at home.
Forty-three children (5-13 years old; 26 boys [60%]) participated. Outdoor 24-hour mean PM2.5 concentrations were moderately high, ranging from 28.6 to 69.8 μg/m3 (median, 53 μg/m3). During true filtration, bedroom PM2.5 concentrations were a mean (SD) of 63.4% (35.9%) lower than during sham filtration. Compared with sham filtration, true filtration was significantly associated with improved airway mechanics, reflected in a 24.4% (95% CI, 11.8%-37.1%) reduction in total airway resistance, a 43.5% (95% CI, 13.7%-73.3%) reduction in small airway resistance, a 22.2% (95% CI, 2.2%-42.2%) reduction in resonant frequency, and a 73.1% (95% CI, 0.3%-145.8%) increase in airway reactance. True filtration was also associated with significant improvements in fractional exhaled nitric oxide (a 27.6% [95% CI, 8.9%-42.4%] reduction) and peak expiratory flow (a 1.6% [95% CI, 0.8%-2.5%] increase). These improvements were significantly associated with bedroom PM2.5 reduction. Improvements in small airway function were nonsignificant (8.4% [95% CI, -1.4% to 18.3%]) in all participants but significant (13.2% [95% CI, 1.2%-25.1%]) in participants without eosinophilic airway inflammation at baseline. No improvements were observed for forced vital capacity, forced expiratory volume during the first second, and the ratio of these in all participants or subgroups.
Per these results, indoor PM2.5 filtration can be a practical method to improve air flow in an asthmatic lung through improved airway mechanics and function as well as reduced inflammation. This warrants a clinical trial to confirm.
ClinicalTrials.gov Identifier: NCT03282864.
重要性：细颗粒物（PM2.5）是一种普遍存在的空气污染物，可沉积在对哮喘至关重要的小气道中。目前尚不清楚使用 PM2.5 过滤设备是否可以改善哮喘儿童的小气道生理学和呼吸道炎症。
目的：发现哮喘儿童在卧室使用 PM2.5 去除装置与哪些小气道病理生理变化有关。
设计、地点和参与者：本双盲、交叉研究纳入轻度或中度哮喘的儿童。参与者随机使用真正的过滤装置和假过滤装置，每种装置使用 2 周，间隔 2 周洗脱期。该研究在中国上海郊区进行，在臭氧含量较低的季节进行。
暴露：测量卧室和窗户外面的臭氧和 PM2.5。
主要结果和措施：在每次干预的开始和结束时，使用脉冲振荡法、肺活量测定法和呼出气一氧化氮分数进行测量。在家中每天测量两次呼气峰流量。
结果：43 名儿童（5-13 岁；26 名男孩[60%]）参与了研究。室外 24 小时平均 PM2.5 浓度处于中等偏高水平，范围为 28.6 至 69.8μg/m3（中位数为 53μg/m3）。与假过滤相比，真过滤时卧室 PM2.5 浓度平均（SD）降低了 63.4%（35.9%）。与假过滤相比，真过滤显著改善气道力学，总气道阻力降低 24.4%（95%CI，11.8%-37.1%），小气道阻力降低 43.5%（95%CI，13.7%-73.3%），共振频率降低 22.2%（95%CI，2.2%-42.2%），气道反应性增加 73.1%（95%CI，0.3%-145.8%）。真过滤也与呼出气一氧化氮分数显著降低（27.6%[95%CI，8.9%-42.4%]）和呼气峰流量显著增加（1.6%[95%CI，0.8%-2.5%]）有关。这些改善与卧室 PM2.5 减少显著相关。在所有参与者中，小气道功能的改善不显著（8.4%[95%CI，-1.4%至 18.3%]），但在基线时无嗜酸性气道炎症的参与者中显著（13.2%[95%CI，1.2%-25.1%]）。在所有参与者或亚组中，用力肺活量、第一秒用力呼气量和这些比值均未观察到改善。
结论和相关性：根据这些结果，室内 PM2.5 过滤可以通过改善气道力学和功能以及减轻炎症来改善哮喘患者的气流，这是一种实用的方法。这需要进行临床试验来证实。
试验注册：ClinicalTrials.gov 标识符：NCT03282864。
