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Swine flu: How good are those N95 masks anyway?

September 30, 2009 |  2:00 pm


Imagine you’re a critical care specialist, and you’ve just been paged to the hospital room of a 28-year-old patient with swine flu symptoms and shortness of breath. Donning a gown and gloves is second nature. But should you cover your nose and mouth? If so, what should you use?

The best answer that public health experts have come up with so far is to wear an N95 respirator mask. The Centers for Disease Control and Prevention recommended the masks in May (when the outbreak was just getting underway), and a report this month from the Institute of Medicine agreed that the fitted masks offer more protection than standard surgical masks.

But in a Perspective published online today in the New England Journal of Medicine, several members of the IOM committee noted that even N95 masks leave much to be desired.


For starters, healthcare workers have long relied on surgical masks to protect themselves from flu germs they might otherwise pick up from patients. “Yet there are no convincing scientific data that support the effectiveness of masks for respiratory protection,” they write.

Studies of regular surgical masks – which fit loosely on the sides, top and bottom – find that they fail to capture between 4% and 90% of aerosolized particles. N95 masks are much better when they are properly adjusted to fit snugly against the wearer’s face, protecting the nose and mouth. They are also capable of filtering out up to 99% of airborne particles.

But, as the authors point out, they only work when people actually wear them. And even in the U.S., plenty of people don’t. One study found that more than 70% of healthcare workers ditched their masks for at least some portion of an 8-hour shift. Not only did they make it hard to communicate with patients, they were just plain uncomfortable.

And as if that weren’t bad enough, the Institute of Medicine committee found anecdotal evidence that the N95 masks are in short supply.

The authors called for a randomized, controlled trial to test whether the scarce N95 respirators actually outperform regular surgical masks in halting the spread of flu. At the moment, the Food and Drug Administration doesn’t distinguish between the two. If they’re equally effective – or ineffective – the shortage would become moot.

-- Karen Kaplan

Photo: Does this mask really help? Credit: Pat Roque/AP