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Covid-19: Experts question guidance to reuse PPE

BMJ 2020; 369 doi: https://doi.org/10.1136/bmj.m1577 (Published 20 April 2020) Cite this as: BMJ 2020;369:m1577

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Re: Covid-19: Experts question guidance to reuse PPE

Dear Editor
The shortage of Personal Protective Equipment (PPE), including gowns, face shields, eye protection, and respirators has been a contentious and difficult issue for frontline health care workers, and for care workers in general. Official guidance around use of PPE has been conflicting over the last few weeks, and updated recommendations from Public Health England (PHE) and the WHO seem to be the minimum that health professional groups and occupational health experts are recommending (1,2). Even if stringent protective measures were advised for our frontline workers, as some are now advocating, how will these be met if there isn’t enough PPE? Physicians are rightly questioning the need to reuse or wear PPE for extended periods of time. For respiratory protective equipment (RPE), the potential to safely reuse single or limited use RPE following decontamination is actively being investigated by hospitals. These are not new sanitisation methods, and several have previously been tested before the emergence of the SARS-CoV-2 virus, due to concerns over the very situation we find ourselves in (3–6). Even the US CDC and 3M, a major worldwide respirator manufacturing company, have acknowledged that reuse may be needed and have released summaries of evidence around decontamination methods (7,8).

Duke University has already started using vapourized hydrogen peroxide (VHP) in their hospital, having confidence that both the decontamination is successful and that the treated respirators are able to adequately fit staff (9). VHP and some other methods, however, require investment in specialised and expensive equipment. Heat treatment (up to about 100°C) can also deactivate SARS-Cov-2 and retain the respirator filtration capabilities (10–12). Heat would require nothing more than a low temperature oven with the ability to distribute heat evenly and consistently over time.

We have carried out pilot work on heating respirators of a variety of styles certified to EU FFP2 and FFP3 standards (13). This work involved a pre-treatment quantitative fit test and a post-treatment fit test with the same respirator on the same wearer. We tested nine masks and two failed the second fit test; the masks that failed showed signs of being distorted. From prior tests of heat-treated respirators, it is likely that it is the fit to face which was faulty rather than the filtration efficiency of the respirator, although we did not test this latter aspect specifically. After one heating cycle the fit factor of most of the mask decreased, and as Fischer et al. (10) found, respirator integrity will probably degrade after only a couple cycles of extended wear and decontamination. Still, even one successful reuse of a mask after heat treatment doubles the amount of respirators available. However, it is important to note that effective respirator fit is partly determined by the facial features of the person, and the degradation of mask performance may differ between wearers, as evidenced by the failure of two of the respirators in our study. We had a duplicate of one of the failed respirators, worn by a second tester and this passed both the pre- and post- treatment tests. These are useful results and we plan to undertake more extensive testing of the various types of respirators used across Scotland and to use this to provide advice to hospitals and other care facilities.

RPE decontamination must be undertaken with caution. Even with a new respirator there is no guarantee that the fit will be adequate, nor that the protection it confers remains the same across the time it is worn. Under current circumstances, we need to develop the best practice for decontamination and re-use, recognizing that it is impossible to re-test each decontaminated respirator. In the future we need to evaluate our preparedness for the next public health crisis to avoid the desperation that we face now.

References:
1. Sayburn A. Are UK doctors getting sufficient protective equipment against covid-19? BMJ [Internet]. 2020 Apr 2 [cited 2020 Apr 21];369. Available from: https://www.bmj.com/content/369/bmj.m1297
2. Brosseau LM. Are Powered Air Purifying Respirators a Solution for Protecting Healthcare Workers from Emerging Aerosol-Transmissible Diseases? Ann Work Expo Health [Internet]. [cited 2020 Apr 21]; Available from: https://academic.oup.com/annweh/article/doi/10.1093/annweh/wxaa024/5802550
3. Heimbuch BK, Wallace WH, Kinney K, Lumley AE, Wu C-Y, Woo M-H, et al. A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets. Am J Infect Control. 2011 Feb;39(1):e1-9.
4. Lindsley WG, Martin SB, Thewlis RE, Sarkisian K, Nwoko JO, Mead KR, et al. Effects of Ultraviolet Germicidal Irradiation (UVGI) on N95 Respirator Filtration Performance and Structural Integrity. J Occup Environ Hyg. 2015 Jul 1;12(8):509–17.
5. Viscusi DJ, Bergman MS, Eimer BC, Shaffer RE. Evaluation of Five Decontamination Methods for Filtering Facepiece Respirators. Ann Occup Hyg. 2009 Nov;53(8):815–27.
6. Lore MB, Heimbuch BK, Brown TL, Wander JD, Hinrichs SH. Effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators. Ann Occup Hyg. 2012 Jan;56(1):92–101.
7. Decontamination Methods for 3M N95 Respirators [Internet]. 2020 [cited 2020 Apr 21]. Available from: https://multimedia.3m.com/mws/media/1824869O/decontamination-methods-for...
8. CDC. Coronavirus Disease 2019 (COVID-19) [Internet]. Centers for Disease Control and Prevention. 2020 [cited 2020 Apr 11]. Available from: https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontaminati...
9. Duke Starts Novel Decontamination of N95 Masks to Help Relieve Shortages | Duke School of Medicine [Internet]. [cited 2020 Apr 21]. Available from: https://medschool.duke.edu/about-us/news-and-communications/med-school-b...
10. Fischer R, Morris DH, Doremalen N van, Sarchette S, Matson J, Bushmaker T, et al. Assessment of N95 respirator decontamination and re-use for SARS-CoV-2. medRxiv. 2020 Apr 15;2020.04.11.20062018.
11. Massey T, Paik S, Fuhrer K, Bora M, Haque R, Baxamusa SH. Quantitative form and fit of N95 filtering facepiece respirators are retained after dry and humid heat treatments for coronavirus deactivation. medRxiv. 2020 Apr 20;2020.04.15.20065755.
12. Smith JS, Hanseler H, Welle J, Rattray R, Campbell M, Brotherton T, et al. Effect of various decontamination procedures on disposable N95 mask integrity and SARS-CoV-2 infectivity. medRxiv. 2020 Apr 15;2020.04.11.20062331.
13. Loh M, Clark R, Cherrie JW. Heat treatment for reuse of disposable respirators during Covid-19 pandemic: Is filtration and fit adversely affected? medRxiv. 2020 Apr 25;2020.04.22.20074989.

Competing interests: No competing interests

01 May 2020
Miranda M Loh
Head of Environment and Public Health
John W. Cherrie, Robert J. Aitken
Institute of Occupational Medicine
Edinburgh United Kingdom