Clinical Question

Do high-efficiency air cleaners prevent chronic obstructive pulmonary disease (COPD) exacerbations and improve quality of life in former smokers with moderate to severe COPD?

Bottom Line

In this small, well-designed study, the use of an active air cleaner for six months was effective in decreasing the rates of moderate exacerbations and rescue medication use in former smokers with moderate to severe COPD. (Level of Evidence = 1b−)

Synopsis

The researchers enrolled 116 former smokers with moderate to severe COPD (forced expiratory volume in one second/forced vital capacity [FEV₁/FVC] ratio 70% or less, FEV₁ less than 80% predicted) who resided in homes where the indoor air particulate matter exceeded 10 mcg per m³. The authors randomized the participants (unknown if the allocation was concealed) to receive two active air cleaners or two sham air cleaners. The active cleaners had high-efficiency particulate air (HEPA) and carbon filters; the sham cleaners had these filters removed, so the air movement and noises were identical. The researchers evaluated the participants sequentially for six months. Using intention-to-treat, after three months, the researchers saw no effects. After six months, although there was no difference in overall health-related quality of life, the participants using the active air cleaners had statistically significant improvement in symptom scores (clinical significance unknown). Although the average number of moderate exacerbations (i.e., needing systemic corticosteroids, antibiotics, or urgent health care visits) was 0.4 in the active air cleaner group compared with 1.25 in the sham group (relative risk = 0.32; 95% CI, 0.12 to 0.91), there was no difference in the rate of exacerbations requiring emergency department visits or hospitalizations. The average frequency of the use of rescue medication was lower in the active air cleaner group than in the sham group (1.88 vs. 3.51). The participants with the lowest FEV₁ at baseline and those spending more time indoors with the active air cleaner on more than 80% of the time had the greatest improvements.