N95 Respirators or Surgical Mask for Protection from Influenza?By current knowledge, a surgical mask is sufficient. Save N95 respirators for TB and other aerosol-transmitted diseases.World Health Organization guidelines for protection of healthcare workers from influenza recommend standard droplet precautions — including surgical masks — except during aerosolizing procedures, when N95 respirators should be used. Researchers performed a literature review to determine whether this recommendation is evidence based and identified 21 studies of respiratory protection in healthcare settings and 25 laboratory studies of the devices' filtering efficiency. Clinical studies evaluated transmission of respiratory syncytial virus, Bordetella pertussis, and severe acute respiratory syndrome (SARS). Reviewers rated only one clinical study as high quality.Three studies that evaluated surgical masks reported protection when masks were used in conjunction with hand hygiene, gloves, and gowns; two reported no protection; and one was equivocal. Three studies that evaluated N95 respirators reported protection, and six studies were inconclusive. Four studies that evaluated N95 respirators and surgical masks showed decreased SARS transmission when either device was used consistently, and one study reported no protective effect. One study of combined use of the two devices was inconclusive.Filtering efficiencies ranged from 0% to 99% for surgical masks, as compared with 95.0% to 99.5% for N95 respirators. Although a recent trial comparing surgical masks and N95 respirators (JW Infect Dis Oct 21 2009) showed equal protection with the two devices, the authors of the literature review suggest that based on findings of the laboratory studies, "aerosol transmission of influenza is plausible," and the currently recommended 1-meter respiratory zone should be enlarged.Comment: Despite the article's title, none of the clinical studies examined influenza transmission, and only three directly compared use of N95 respirators and surgical masks. In addition, many confounders compromised the studies' ability to discriminate between the effects of respiratory protection and other factors. Influenza is considered to spread via droplet rather than aerosol. Absent clear evidence of additional benefit over standard surgical masks, N95 respirators should be reserved for protection from diseases that are clearly aerosol transmitted (e.g., varicella, measles, tuberculosis).— Kristi L. Koenig, MD, FACEPPublished in Journal Watch Emergency Medicine November 6, 2009Citation:Gralton J and McLaws M-L. Protecting healthcare workers from pandemic influenza: N95 or surgical masks? Crit Care Med 2009 Sep 1; [e-pub ahead of print]. (http://tinyurl.com/yztbnke) [Medline® Abstract]
Copyright © 2009. Massachusetts Medical Society. All rights reserved.The above message comes from "Journal Watch", who is solely responsible for its content.
No comments:
Post a Comment