Debate Over Respiratory Protection for Healthcare Workers Continues

The debate over the best respiratory protection for healthcare workers against H1N1 influenza continues, leaving clinicians eager to comply but caught between the guidance issued by government agencies, the data from various researchers, and the recommendations from infectious diseases and infection control associations.

A study which suggested that N95 respirators offered better protection against the H1N1 influenza virus than surgical face masks was called into question at the annual meeting of the Infectious Diseases Society of America (IDSA) in October.

The paper was written by Raina MacIntyre, PhD, a professor of infectious diseases epidemiology and the head of the University of New South Wales School of Public Health and Community Medicine, in Sydney, Australia. MacIntyre and her colleagues tracked healthcare workers in Beijing, China, who wore surgical face masks and N95 respirators, and compared rates of influenza and respiratory illness. Preliminary findings were presented at a meeting of the Interscience Conference on Antimicrobial Agents and Chemotherapy in September. MacIntyre says the research has not been retracted, but that the same data had been analyzed differently for the final paper; in essence, researchers excluded a control group of almost 500 healthcare workers and adjusted the statistics, and they maintain that the difference in infection rates between mask and respirator use was not statistically significant. At the time of writing, McIntyre’s research has not yet been published in a journal.

Proponents of surgical face masks say they are less expensive and easier to wear than N95 respirators; but scientifically, there is evidence indicating the effectiveness of each type of protective apparel. In a randomized trial designed to study surgical masks vs. N95 respirators for preventing influenza transmission, Loeb et al. (2009) conducted a randomized controlled trial of 446 nurses in emergency departments, medical units and pediatric units in eight tertiary-care hospitals. Nurses wore either a fit-tested N95 respirator or a surgical mask when providing care to patients with febrile respiratory illness during the 2008-2009 influenza season; 225 nurses received surgical face masks and 221 received N95 respirators. Influenza infection occurred in 50 nurses (23.6 percent) in the surgical face mask group and in 48 (22.9 percent) in the N95 respirator group. The researchers concluded that there was no difference in influenza rates among nurses using one type of protective device versus the other.

Srinivasan and Perl (2009) point out that “the Centers for Disease Control and Prevention (CDC) guidelines for preventing transmission of seasonal influenza are intended to limit exposure to large respiratory droplets and recommend the use of a medical (surgical) mask during the care of a patient with influenza as part of a comprehensive infection control strategy. However, data suggest that under certain conditions, influenza viruses can be transmitted via smaller particles that evade filtration by such masks. Unlike medical masks, N95 particulate respirators protect wearers from small particles when appropriately designed and worn. Recommendations to prevent influenza transmission take on special importance during pandemics, when there is little, if any, native immunity and vaccine is not available immediately.”