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N95 masks that are well past their expiration date or have been used and re-sterilized are acceptable alternatives to standard new disposable N95 masks, new research indicates. But some masks start with better felt effectiveness than others.
Personal protective equipment (PPE) and especially N95 respirators – named for their ability to filter 95% or more of small 0.3-μm particles – are scarce commodities in the time of COVID-19.
Deficiencies in PPE and N95 masks have led some providers and healthcare systems to be creative, adopting non-standard practices, such as using expired N95 masks and various decontamination processes to prolong their use. Hospitals are also turning to imported or donated masks not approved by the National Institute for Occupational Safety and Health (NIOSH) as a potential replacement for restricted NIOSH-approved N95 masks.
But how safe and effective are these alternatives? A new study published today in JAMA internal medicine provides some reassuring information.
Emily Sickbert-Bennett, PhD, with the Department of Infection Prevention, University of North Carolina Health Care, Chapel Hill, and colleagues test the fat filtration efficiencies (FFEs) of 29 different fit-face alternatives to face masks worn by a male and female volunteer in a custom-built exhibition room.
They measure FFEs during a series of repeated movements of the torso, head and facial muscles to perform typical occupational activities of the mask wearer. They used a particle generator to create environments for individuals in the room.
According to Sickbert-Bennett and colleagues, respirators from N95 to 11 years past their expiration date with intact elastic straps and those sterilized with ethylene oxide and hydrogen peroxide retain FFEs> 95%.
The performance of N95 masks in the wrong size was somewhat lower, with FFEs between 90% and 95%.
The researchers also evaluated steam sterilization for two respirator models. Steam visibly disrupted the 3M 1860 N95 respirators, making them “unsuitable” for reuse. However, the 3M 1870+ Aura face masks were not visibly altered and maintained> 95% FFE when placed through a single cycle of steam autoclaving, they report.
All six of the respirators not listed as approved failed to achieve 95% FFE. They are the SAS Safety Corp 8617 Duckbill; Fangtian Duckbill FT-032 with exhaust valve; Safe living N95 B150; Jia Hu Kang KN95 mask with ear loops; Zhongshan Dongfeng Huangshang GM700; and Guangdong Fei Fan KN95.
In addition, neither of the two imported respirators approved by the US Centers for Disease Control and Prevention but not by NIOSH (Dasheng DTC-3X-1 and DTC-3X-2) 95% FFE; DTC-3X-1 was the more effective of the two (about 80% FFE).
“These respirators, which have elastic ear loops and a vertical fold design, were the least effective when the test individual bent at the waist and looked up and down,” the researchers say.
Surgically, procedure masks probably work well in routine care
Not surprisingly, surgical and procedure masks had substantially lower mean FFEs than the N95 respirators, they found. The variability in their appearance was largely dependent on the tightness of the contact between the material and the wearer’s skin.
In all tests, the FFE of masks secured with straps performed better than those secured with ear loops, researchers say.
Procedural masks with ear loops had FFEs of only 38.1%. They were least effective when moving the wearer’s head from left to right (21.2% FFE), making visible gaps between the face mask and the wearer.
“Taken together, these data suggest that elastic ear loops may not provide adequate tension to maintain a tight fit during a typical range of motion. In addition, these findings illustrate the importance of fit in maximizing the overall effectiveness of both respirators and masks,” researchers write.
“This evaluation provides quantitative results in which health care managers, leadership leaders, and hospital epidemiologists can make evidence-based decisions to protect clinicians and other health professionals during a pandemic or long-term mask shortage,” conclude Sickbert-Bennett and colleagues.
The co-editors of a linked editorial office say despite the apparent “incomplete” FFE of non-NIOSH-approved respirators and surgical masks in the laboratory, “there is reason for optimism about their effectiveness in the world.”
It is “critically important” to find innovative ways to overcome PPE deficits, write Caitlin Dugdale, MD, and Rochelle Walensky, MD, MPH, of Massachusetts General Hospital, Boston.
“Frontline clinicians and essential healthcare professionals participating in the highest risk procedures should receive the highest level of protection with NIOSH-approved N95 respirators,” she points out.
The present study shows that processed use and expired range of N95 masks are “safe and offer excellent alternatives to standard N95 disposable masks. Despite lower filter efficiency of submicron particles, surgical masks and other N95 alternatives are likely to provide adequate protection. against transmission for routine care. “
This study was supported by a collaboration agreement between the University of North Carolina at Chapel Hill and the U.S. Environmental Protection Agency. Sickbert-Bennett has reported that they have oversight costs from PDI and Johnson & Johnson. Dugdale has reported that she has received travel allowance from the Infectious Diseases Society of America and personal allowances from the Joint United Nations Program on HIV / AIDS.
JAMA Intern Med. Published online August 11, 2020. Full text, Editor
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