Table 7.

Evidence Profile: Reuse of N95 Compared to Surgical Masks for Health Care Workers During Gastrointestinal Procedures

Variable	Certainty assessment			Impact
	No. of studies	Study design	Certainty
Infection with COVID-19	8	Anecdotal reports Experiments under laboratory conditions	□◯◯◯ VERY LOWa,b,c	No direct evidence was found with regard to the safety of reuse of masks (surgical masks [SMs] and N95) during a COVID-19 pandemic. Furthermore, indirect evidence from other pandemic outbreaks did not reveal empiric data on infection rates, but rather reports of anecdotal experience or experiments under laboratory conditions or mathematical models. Anecdotal reports on using SMs over N95 as a barrier to pathogens and extend the useful life of the N95 respirator has been published.58 This was sparingly utilized during the SARS outbreak, but the effects of prolonged use of this combination on health care workers and the infection rate have not been reported. Similarly, reports exists that >40% of health care workers reused their N95 during the H1N1 pandemic.59,60 Furthermore, a mathematical model to calculate the potential influenza contamination of facemasks from aerosol sources in various exposure scenarios, showed that single coughs (≈19 viruses) were much less than likely levels from aerosols (4473 viruses on filtering facepiece respirators and 3476 viruses on SMs).61 In laboratory testing, it has been reported that 5 consecutive donnings can be performed before fit factors consistently drop to unsafe levels.62 In addition, decontamination of N95 with hydrogen peroxide has showed that exposure up to 50 cycles does not degrade the filtration media and mechanical testing but has demonstrated that the elastic straps were stiffer after exposure to up to 20 hydrogen peroxide vapor cycles. Thus, more than 20 cycles can impair proper fit.63 There have been narrative reports, news conference reports, and the CDC recommendation90 during H1N1 pandemic suggesting use of a cleanable face shield or surgical mask to reduce N95 respirator contamination.57

^aRisk of bias: There is no comparator with optimal PPE to understand the risk of the acceptable protection from COVID-19.

^bThere are multiple layers of indirectness. The population is different—studies were done on influenza virus or simulation studies on healthy participants, and there are no studies on aerosol generating procedures (AGP). Outcome is indirect as well; most of these studies have tolerability of the mask or laboratory testing as outcomes.

^cUnable to assess for imprecision because outcome cannot be measured.