368 Efficacy of Continuous Use Disposable N95 Masks in Clinical Practice in the Emergency Department

Study Objectives: During the 2020 COVID-19 pandemic, many emergency departments (EDs) in the United States initiated continuous use of N95 disposable respirators rather than disposing of respirators after each patient encounter in order to conserve personal protective equipment This study investigates the efficacy of wearing disposable n95 respirators continuously throughout an ED shift using qualitative fit testing as a measure of appropriate mask seal and function Methods: This is a prospective cohort study at a single level I trauma center of ED staff required to wear respirators continuously throughout their shifts during the COVID-19 pandemic Subjects were doctors, nurses, and technicians, and enrolled in the study on a voluntary basis over the course of the 6 week duration Subjects were previously fitted for their assigned respirator by employee health per hospital policy, and personnel that failed this initial testing were excluded from the study Investigators enrolling subjects were trained to perform qualitative fit testing using OSHA guidelines Subjects were fit tested periodically throughout their shifts by investigators At any time a mask failed, it was replaced Investigators filled out a questionnaire for each subject enrolled noting the type of respirator and hours of continuous wear that shift, as well as subjective sense of seal security As subjects were working clinically, no attempt was made to modify their on-shift behavior regarding taking breaks or donning/doffing for nourishment or hydration Data were analyzed using descriptive statistics The study was approved by the institutional review board Results: One hundred thirteen disposable N95 respirators were evaluated using qualitative fit testing while on shift in the ED, with 23 failures at first testing These masks were not retested, and the subjects received new masks Twenty-seven masks passed at the start of a shift (time zero) and did not have repeat testing during the course of the shift These were excluded from further analysis Seventeen masks passed testing after several hours of continuous wear, but only had a single fit test done partway or at the end of a shift These were assumed to have passed if tested at shift start, and were assigned as “passes” for continuous use Forty-six disposable N95 masks had an initial pass and were evaluated for continuous use, of which 6 subsequently failed fit testing later in the shift, giving a fail rate with continuous use of 9 5% Of the 29 failed fit tests, the subjects documented that they believed their seal was adequate in 20 cases (69%) Conclusion: Continuous use of disposable N95 masks throughout an ED shift is reasonable during a PPE shortage if wearers are assured of fit at the start of their shift, as most failures occur on initial testing However, passing on initial fit testing is not a guarantee of ongoing fit maintenance Mask wearers have little insight into adequacy of fit