Table 8.

Evidence Profile: Prolonged Use of N95 Compared to Surgical Masks for Health Care Workers During Gastrointestinal Procedures as a Last Resort in Resource-Limited Settings

Variable	Certainty assessment			Impact
	No. of studies	Study design	Certainty
Infection with COVID-19	4	Anecdotal reports Experiments under laboratory conditions	□◯◯◯ VERY LOWa,b,c	No direct evidence was found with regard to the safety of extended use 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. Experiment on tolerability of the N95 with prolonged use on health care workers showed that health care workers were able to tolerate the N95 for 89 of 215 (41%) total shifts of 8 hours. Other 59% mask was discarded before 8 hours because it became contaminated or intolerance.91 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 Additionally, there was a survey on health care workers during H1N1 pandemic and >40% of the health care workers were reusing or had a prolong use on their N95.59,60

^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 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.