11 August 2020 18:39
This spring, due to limited national supplies of N95 face masks, hospitals across the country asked the public and private companies to donate personal protective equipment (PPE), including many different types of masks, to be sure healthcare workers were protected while caring for patients. With so many options, infection prevention experts at the UNC Medical Center set out to gather evidence on the fitted filtration efficiency of dozens of different types of masks and mask modifications, including masks sterilized for reuse, expired masks, novel masks sourced from domestic and overseas sources, and homemade masks. Their data, published today in JAMA Internal Medicine, show that reused, sterilized N95 masks and very out-of-date N95 masks retain their effectiveness at protecting healthcare workers from COVID-19 infection. To assess mask fitted filtration effectiveness, Emily Sickbert-Bennett, PhD, director of Infection Prevention at UNC Medical Center and colleagues turned to someone she knew she could trust: her dad, William Bennett, PhD, professor of medicine, who leads the Mucociliary Clearance and Aerosol Research Laboratory at the UNC Center for Environmental Medicine, Asthma, and Lung Biology (CEMALB). I told him we had two types of masks – used, sterilized and expired N95 masks – and we needed to know whether they would offer safe and effective protection, in case we needed our healthcare co-workers to use them.
And he said it would be possible for his lab to test them and give us data upon which to base our decision-making." Emily Sickbert-Bennett, PhD, Director of Infection Prevention, UNC Medical Center Thanks to a cooperative agreement with the EPA Human Studies Facility on the UNC-Chapel Hill campus, in which Bennett's labs reside, Bennett, assistant professor Phillip Clapp, PhD, and research associate Kirby Zeman, PhD, teamed with EPA research scientist, James Samet, PhD, to measure the fraction of submicron particles that penetrate into the breathing space of subjects wearing a mask while performing a series of tasks that simulate conditions such as speech and movement during a work shift. Such tests provided infection prevention leaders quantitative data they used to rank the best respiratory protection options for healthcare personnel during the COVID-19 outbreak. The researchers found that certain N95 masks – as rated by the National Institute of Occupational Safety and Health (NIOSH) Administration – provide greater than 95 percent effectiveness at keeping the wearer from inhaling very small airborne particles that may carry SARS-CoV-2 – the virus that can cause COVID-19. Furthermore, these masks retain such effectiveness many years beyond the masks' expiration dates. In addition, these NIOSH-rated masks can be subjected to sterilization with hydrogen peroxide or ethylene oxide without compromising their efficiency.
Finally, their fitted filtration procedures showed that surgical masks with ties were approximately 70 percent effective at filtering their inhaled particles, while surgical masks with ear loops were about 40 percent effective. Clapp, co-first author, emphasized that, "One of the keys to protection is how snug a mask fits. An N95 mask that forms a tight seal offers the optimal infection prevention. However, evidence from previous studies suggests that even the surgical masks with <95% efficiency are effective in preventing acquisition of epidemic coronaviruses. "Our hierarchy of mask supplies essentially amounts to always using the safest option on the shelf, especially for those healthcare workers caring for COVID-19 patients," said Sickbert-Bennett, co-first author of the JAMA Internal Medicine paper. "To date, UNC Health has maintained adequate supplies of NIOSH-approved PPE," Sickbert-Bennett said. "We feel confident we can maintain protection of the UNC Health workers with the variety of face masks and respirators tested as part of this JAMA-published study." Dive Brief: For hospitals still facing N95 respirator shortages, expired N95 masks and those sterilized using new decontamination methods are acceptable alternatives, according to a study published Tuesday in JAMA Internal Medicine. Researchers looked at 29 face mask alternatives to the industry-standard N95s in short supply and high demand amid the COVID-19 pandemic. N95 masks sanitized with ethylene oxide and vaporized hydrogen peroxide retained their filtration efficiencies of more than 95%. N95 masks up to 11 years past their expiration date had the same results. Surgical and procedure masks fitted with ties were less effective, filtering about 70% of particles, while those secured with elastic ear loops only filtered about 38%. Dive Insight: One of the biggest problems health systems have faced during the COVID-19 crisis is securing enough personal protective equipment, including masks, to keep providers safe. As the problem became clear, the Centers for Disease Control and Prevention rolled back regulations on when N95s must be used. The agency also offered guidance on their re-use. Nurses have been angered by the lack of protection,which has helped spark strike threats and other labor actions. In New York, nurses cited lack of PPE in lawsuits they filed against two hospitals and the state health department. A survey from the country's largest nurses union found 63% reported they had been forced to re-use an N95, though it did not indicate whether or how the equipment was decontaminated. The JAMA Internal Medicine findings point to the possibility that protection is maintained when proper cleaning is done. And a separate study from the same publication, also posted Tuesday, found that the rate of positive COVID-19 tests among healthcare workers at a community hospital in Roslyn, New York, was lower than that of the surrounding community. Those researchers said "this is strong evidence that current PPE practices are protective, easing health care workers' concern and psychological distress." The best results from the face mask study came from a Controlled Air Purifying Respirator System (MAXAIR) fitted with a face shield — preventing more than 99% of particles from entering someone's breathing space. Those masks and N95 respirators fitted to the face are still the preferred choice of protection against the novel coronavirus, though they're still in short supply after supply chain issues earlier this year. In a recent survey from group purchasing organization Premier, more than half of hospitals said N95s were heavily backordered. Researchers conducted the study between April and June in a laboratory setting supplemented with sodium chloride particles to see how well various N95 mask alternatives filtered out particles on a male and female volunteer. N95 respirators in the wrong size had slightly decreased performance, and procedural face masks secured with elastic ear loops were the least efficient of all alternatives. Another interesting finding involved imported respirators, such as KN95 masks from China. Many have been donated or acquired by hospitals as a potential replacement for limited N95 respirators, though they aren't an acceptable alternative, according to the study, which found neither achieved 95% filtration. The more effective of the two imported respirators achieved just 80%. In an editorial published alongside the findings, Caitlin Dugdale, an infectious disease physician at Massachusetts General Hospital, wrote that while competition and price gouging for masks has certainly hindered access, supply is the biggest problem. Prior to the pandemic, surgical and N95 masks generally cost about 8 cents and 50 cents, respectively, Dugdale wrote. KN95 masks which are not typically sold in the U.S., have been sold during the crisis from $2 to $4 per mask. "Until we have a better understanding of how filtration efficacy translates to improved protection against SARS-CoV-2 transmission, health care systems are left to pay top dollar to keep their most valuable resources —clinicians and health care workers — safe," Dugdale wrote.