The efficacy of continuous use disposable N95 masks in clinical practice in the emergency department

Abstract

During the SARS-CoV-2 pandemic, many emergency departments (EDs) initiated continuous use of N95 disposable respirators (N95s) rather than discarding them after each use to conserve respirators. This study investigates the efficacy of wearing disposable N95s continuously during clinical work. Methods This is a prospective cohort study of ED staff required to wear N95s continuously throughout their shifts. Subjects were doctors, nurses, and technicians who were previously fitted for their assigned N95 by employee health. Subjects were fit tested periodically throughout their shifts. Investigators filled out a questionnaire for each subject noting the hours of continuous N95 wear. Data were analyzed using descriptive statistics. Results One hundred thirteen N95s were evaluated, with 23 failures at first testing. These were not retested. Twenty-seven N95s passed at the start of a shift and did not have repeat testing during the course of the shift. These were excluded from further analysis. Seventeen N95s 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 N95s had an initial pass and were evaluated for continuous use, of which 6 subsequently failed later in the shift, giving a fail rate with continuous use of 9.5%. Conclusion Continuous use of disposable N95s throughout an ED shift is reasonable during a PPE shortage if wearers are assured of fit at the start of their shift.

Incidence of Fit Test Failure During N95 Respirator Reuse and Extended Use

“…[11][12][13] However, evidence of the safety of reuse practices in clinical settings is lacking, 14 as few prospective studies have been conducted to explicitly determine the incidence of fit failure during N95 reuse. [15][16][17] A pilot study conducted by some of us in 1 ED found that N95 reuse during increasing numbers of shifts was significantly associated with increased fit test failure. 15 These studies were limited, as single-center enrollment and cross-sectional designs did not permit definitive estimates of whether N95s could safely be reused.…”

“…15 These studies were limited, as single-center enrollment and cross-sectional designs did not permit definitive estimates of whether N95s could safely be reused. [15][16][17] We conducted a multicenter prospective cohort study of frontline HCWs across 6 EDs in the US to measure the incidence of qualitative fit test failure during N95 reuse, which included multiple donnings and doffings. We also sought to compare the incidence of fit test failure between HCWs across various N95 types.…”

“…Several laboratory-based experimental studies evaluating the safety of reuse found that N95 fit was reduced after 5 donnings and doffings . However, evidence of the safety of reuse practices in clinical settings is lacking, as few prospective studies have been conducted to explicitly determine the incidence of fit failure during N95 reuse . A pilot study conducted by some of us in 1 ED found that N95 reuse during increasing numbers of shifts was significantly associated with increased fit test failure .…”

“…A pilot study conducted by some of us in 1 ED found that N95 reuse during increasing numbers of shifts was significantly associated with increased fit test failure . These studies were limited, as single-center enrollment and cross-sectional designs did not permit definitive estimates of whether N95s could safely be reused …”