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Reused duckbill N95 masks have higher fit test failure rate than dome-shaped masks
During a recent shift in the ED, Nida F. Degesys, MD, redonned her used duckbill N95 mask and thought to herself, “Does this mask still fit my face properly?”
“I, like many front-line providers, have been concerned about becoming infected with COVID-19,” Degesys, a clinical assistant professor in the department of emergency medicine at University of California, San Francisco, told Healio. “With the CDC’s personal protective equipment (PPE) guidelines changing so rapidly, I found myself wondering whether the N95 that I was reusing was still protecting me.”
This thought prompted her to check her mask, as well as those of several other faculty members, with fit tests, which the masks failed. The results led Degesys, with the support of her emergency department (ED) leadership, and colleagues to initiate a quality improvement project at UCSF EDs.
The researchers conducted a cross-sectional study of N95 t in UCSF EDs from April 4 to 6, 2020. They enrolled a convenience sample of health care workers, including physicians, nurses, nurse practitioners, physician assistants and patient care technicians, during their clinical shifts when the researchers were present. All health care workers in the study had passed a standard N95 fit test required by the Occupational Safety and Health Administration within the last 1 to 2 years.
Degesys and colleagues performed a qualitative t test of dome-shaped and duckbill N95s at different points during extended use and reuse using a standardized hood and 3M FT32 bitter testing solution. Participants who could taste the solution failed the t test and were tted with a new N95.
Among the 68 health care workers included in the study, 51 used dome-shaped masks and 17 used duckbill masks. Overall, 38.2% of participants failed the fit test. Study data revealed that duckbill N95s had a high failure rate, with over 70% of masks failing, whereas dome-shaped masks had a failure rate of 27.5%. Dome-shaped mask failure correlated with increased number of shifts used (median, 4 shifts vs. 2 shifts), number of donnings and doffings (median, 15 vs. 8) and number of hours used (14 vs. 12). Results were significant for number of shifts used and number of donnings and doffings (P < .001 for both), but not number of hours worn.
“Our findings of high rates of mask failure after reuse and extended use call into question whether such practices offer adequate protection against health care worker COVID-19 infection,” Degesys said. “Further studies looking at precisely when masks fail will be very helpful in guiding hospital policies should we find ourselves in another shortage. Until then, we are only able to make some preliminary recommendations based on the limited data we collected.”
If masks can be reused safely, for multiple shifts, health care workers will be able to preserve more of them and the stockpile will increase, Degesys said, “but that is not enough.”
“Even if N95 masks fit properly for several shifts, until we have better decontamination methods, it may still be safest to dispose of masks after a single encounter,” she said. “Ideally, we need to produce an adequate supply of masks so that health care workers do not need to reuse them. We also need to develop and test easily accessible decontamination methods that do not affect the integrity or fit of the mask.”
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