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Original Investigation
April 6, 2020

Association Between Bedroom Particulate Matter Filtration and Changes in Airway Pathophysiology in Children With Asthma

Author Affiliations
  • 1Nicholas School of the Environment, Duke University, Durham, North Carolina
  • 2Department of Pediatrics, Shanghai General Hospital, Shanghai Jiao Tong University, Shanghai, China
  • 3Global Health Research Center, Duke Kunshan University, Kunshan, Jiangsu Province, China
  • 4Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina
  • 5Department of Building Science, Tsinghua University, Beijing, China
  • 6Beijing Key Laboratory of Indoor Air Quality Evaluation and Control, Beijing, China
  • 7Beijing Innovation Center for Engineering Science and Advanced Technology and State Key Joint Laboratory of Environment Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China
  • 8Department of Pulmonary Medicine, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
  • 9Department of Civil and Environmental Engineering, College of Engineering, University of Wisconsin–Madison, Madison
  • 10Underwriters Laboratories Inc, Marietta, Georgia
  • 11Duke Global Health Institute, Durham, North Carolina
JAMA Pediatr. 2020;174(6):533-542. doi:10.1001/jamapediatrics.2020.0140
Key Points

Question  Fine particles (particulate matter 2.5 μm) are capable of reaching and being deposited in the small airways; can the use of a particle-removing device be associated with improvements in airflow and inflammation in children with asthma?

Findings  In this randomized, double-blind, crossover study of 43 children with mild or moderate asthma, using a particle-removing device in bedrooms for 2 weeks was significantly associated with improved small airway mechanics, increased peak expiratory flow, and reduced pulmonary inflammation.

Meaning  Indoor air filtration was associated with improved airflow in the small airways and reduced respiratory inflammation, and it thereby may serve as an important preventive measure in asthma management.


Importance  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.

Objective  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.

Exposures  Ozone and PM2.5 were measured inside bedrooms and outside a window.

Main Outcomes and Measures  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.

Results  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.

Conclusions and Relevance  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.

Trial Registration  ClinicalTrials.gov Identifier: NCT03282864

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