Many hospitals will face PPE shortages in the coming weeks. Shortages of N95 filtering facemask respirators (FFRs) will be most impactful, but also standard masks, gowns and plastic face shields. Stockpiling of used PPE should be commenced NOW so that they will be available for re-use after disinfection. While using a mask that another has already used may be unappealing, it is probably preferable to no mask.
We could set up lidded buckets/ bins for USED, UN-SOILED N95 FFRs, standard masks, gowns and face shields in some areas in the department, then seal and label bags with the date. PPE could even be directly inspected for soiling, with discarding of soiled items, and placement of individual items in separate labelled ziplock bags.
In the event of a complete PPE shortage, once these bags have been sealed for approx. 1 week, they could likely be considered "COIVD-19" free. The longer they are stored, the greater the confidence of no COVID-19 infectious risk and if we (hopefully) never need them they can be dumped.
In addition, various disinfection techniques have been tested for these PPE. There will soon be guidelines on practical, effective disinfection solutions which we can apply to the stockpile of PPE for recycling.
Summary of available literature:
An analysis of the use of hygiene measures and personal protective equipment (PPE) during the early phase of spread of COVID-19 in January 2020 in Wuhan province of China compared healthcare worker infection rates in wards using different infection control precautions (1)
. Three wards using ‘higher precautions’ of N95 masks and ‘frequent’ hand washing were retrospectively compared to three wards with ‘lower precautions’ of no masks and ‘occasional’ hand washing.
Despite a higher exposure odds ratio of 8.33 in the ‘higher precautions group’, this group had no infections in 278 workers compared to 10 infections in 217 in the ‘lower precautions’ group. Caution should be taken attributing the lower rates of infection solely to N95 masks, as the ‘lower precautions’ had an undefined lower rate of hand washing and presumably greater degree of face-touching in the absence of masks as a physical barrier or mental reminder. However, this will still contribute to demand for facemasks, particularly N95.
Historically, influenza spread was believed to occur through droplets or contact with infected secretions(2)
. Quantitative air sampling of healthcare facilities suggest that small airborne particles could contribute to influenza exposure(3)
. Surgical masks provide barrier protection from droplets, but do not prevent aerosolized spread of infection.
The CDC advised N95 masks when caring for novel influenza associated with severe disease(4)
. However, it must be noted in meta-analyses and randomised trials N95 masks have not been shown to reduce influenza-like-illness compared to surgical masks in a healthcare setting (5,6)
. Ad hoc attempts at PPE, such as cloth face masks are likely to provide no benefit to prevent viral respiratory illness compared to no-mask(7)
A 2013 survey of the Infectious Diseases Society of America (IDSA) Emerging Infections Network (EIN) found that, among doctors involved planning for influenza protection, 9% believed influenza is ‘frequently’ transmitted by small-particle aerosols and 34% believed this occurred ‘occasionally’, with 52% considering aerosol transmission to occur rarely or never.
When asked about PPE preferences during a severe pandemic scenario (associated with ≥1% mortality), 67% preferred N95 respirators for providing routine care for influenza patients(8)
. For a “hypothetical setting where N95-level protection was recommended but there was a shortage of N95 respirators; the scenario included a circulating influenza strain with high mortality and no available vaccine”. In this scenario, the most-to-least endorsed strategies were: Extended use of N95 masks, reuse of N95 masks, use of Powered Air-purifying Respirators, use of surgical masks and use of elastomeric respirators.
A multi-site survey published in March 2020 of attitudes of hospital workers to options for FFRs in a high mortality influenza pandemic explored acceptance towards reuse of FFRs after UV light decontamination. It found that reuse of FFR after decontamination was preferable to reuse of FFR without decontamination which was preferable to no FFR. All sites had high (80%+) agreement that UV decontamination would mitigate FFR shortages in a severe pandemic (9)
The Centre for Disease control has specific recommendations for optimising facemask supply in a crisis such as the COVID-19 pandemic (10)
. Need for mask usage should be reduced by rapid isolation of suspected infected patients. Consideration can be given to using stockpiled N95 masks beyond their shelf-life, although they may not function optimally. The use of surgical and N95 masks should be prioritised by activity type, with healthcare providers remaining 6 feet from symptomatic patients not requiring masks, and those going within 3 feet providing care wearing surgical masks if the patient is masked and wearing N95 masks if the patient is not masked. In addition, mask usage could be prioritized for those most at risk of complication of infection.
Where supplies of N95 masks are depleted, the CDC provides recommendations on extended and limited reuse of N95 masks(11)
- Extended use refers to wearing a mask for multiple encounters with infected patients without removing the mask and would be recommended when caring for multiple patients with the same respiratory infection and patients are grouped in the same waiting area/ ward.
- Reuse refers to using the same mask for multiple encounters but removing ‘doffing’ it after each encounter and reapplying ‘donning’ it for the next encounter. This is commonly done for pathogens where contact transmission is not a concern.
Extended use is favoured as it involves less touching of the mask and therefore less contact transmission risk. Length of use is generally dictated by contamination or the mask or practical issues, such as need to eat, rather than a maximum number of hours. A cleanable face shield worn over the N95 will reduce contamination and extend use time.
Reuse is limited by recommendations to discard the mask after contact with a patient infected with a disease requiring contact precautions (such as COVID-19). Allowing for this, a face shield worn over the mask should extend it’s usability period. Between uses, it is suggested to hang used respirators in a designated storage area or keep them in a clean, breathable container such as a paper bag between uses. The CDC suggests masks should not be shared and only used by one individual. A study of the effect of multiple donnings on the facial fit of N95 masks has suggested that after 5 consecutive donnings the facial fit of the mask can be reduced(12)
Fisher et al estimated the influenza contamination level for the entire external surface of an FFR resulting from aerosols in a healthcare setting(13)
. It ranged from 10-100,000 viruses, depending on different scenarios using airborne influenza concentrations published in the literature.
An assessment of the stability of COVID-19 on different surfaces found COVID-19 is undetectable by 96 hours on cardboard, copper, plastic and stainless steel (14)
. A previous study on the survival of a surrogate coronavirus for SARS on PPE found that the virus was detectable for up to 24 hours after inoculation on N95 masks (15)
A recent pandemic simulation estimated that 7.3 billion N95 masks could be needed in the United States alone(16)
. The Institute of Medicine (IOM) projected in 2006 that a 6-week influenza pandemic would require 90 million N95 Filtering Facepiece Respirators (FFRs) (17)
. The IOM considered the feasibility of reusing N95 masks, stating that any method decontaminating a disposable N95 must remove the pathogen, be harmless to the user, and not compromise the integrity of the various parts of the respirator. It determined at the time that no effective decontamination strategy existed. Since then, multiple methods of decontamination have been tested.
- Alcohols cannot be used as they remove the electrostatic charge from the filtration media, degrading the ability to filter particles.
Other methods which have demonstrated utility include:
Ultraviolet Germicidal Irradiation (UVGI)
has been described in several studies(18–21)
. In laboratory conditions, masks contaminated with influenza and soiled with mucin and sebum were exposed to 1 J/cmsq resulting in significant reductions in viable influenza virus in 12 of 15 masks models, equivalent to fully disinfecting masks with the highest level of influenza contamination in a healthcare setting predicted by Fisher et al(13,20,22)
This method is already in use for the COVID-19 pandemic in the university of Nebraska Medical centre(23)
. Healthcare workers write their names on the masks before they use them, then place in paper bags when they are removed. The bags are brought to a UV light room for treatment at ‘three times the concentration of UV light needed to kill coronaviruses’ for 3-5 minutes. Masks are returned to bags with healthcare workers names on them.
Main benefits: Fast (1-20 minutes total), No chemical residue risk
Main Limitations: requires specialised UV equipment most hospitals don’t have.
Microwave Steam Bags (MSB)
are commercially available products marketed for disinfection of breastfeeding supplies, and use a standard home microwave. Use of MSB on N95 masks resulted in saturation of three mask models with hydrophilic layers, however three other mask models had a log 3 (99.9%) reduction in bacteriophage MS2(24)
. After 3 treatment cycles no significant change in filtration was identified.
A similar study using microwave steam without a bag resulted in a log 4 (99.99%) reduction in H1N1 virus on 93% of samples and the authors recommended a standardised reservoir, such as these MSBs, would increase uniformity of steam coverage(25)
. Similar results were reported by Lore et al and Bergman et al with no deleterious effect of microwave generated steam on the filtration performance of N95 FFRs (19,26)
. Both Bergman et al. and Viscusi et al. found fit of the FFR models used in their investigations to be unaffected by the use of microwave generated steam(26,27)
Main Benefits: Easily accessible inexpensive materials, No caustic chemicals
Main Limitations: Needs 1 hour plus drying time
Other options include:
- Bleach (Viscusi 2009)
- Autoclave (Lore 2015) (Viscusi 2011) - autoclaving is highly destructive process for some FFR models
- Ethelene oxide gas (Viscusi 2009)
- Vaporised hydrogen dioxide (Viscusi 2011)
Cleaning is considered a necessary step prior to disinfection to ensure that soiling materials do not interfere with the decontamination process. Commercially available wipes have been shown to be effective for clearing mucin and S. Aureus from N95 masks, with hypochlorite containing wipes resulting in significant disinfection with minimal reduction in filtration ability of masks(28)
Standard protocols have been described for bleach bath disinfection of reusable respirators(29)
. These could possibly be adapted as low tech, relatively low effort to disinfect batches of ‘single-use’ PPE
Even without an established feasible and reliable method to actively disinfect PPE, ‘passive temporal disinfection’ could be considered. Stability testing of COVID-19 on various surfaces identified that no viable virus remained on plastic and stainless steel after 72 hours with shorter times to no viable virus on copper and plastic(14)
. A previous study on the survival of a surrogate coronavirus for SARS on PPE found that the virus was detectable for up to 24 hours after inoculation on N95 masks. Although a definitive safe time threshold where no viable virus remains has yet to be established, there will be a time when masks can be re-used without significant risk of COVID-19.
Shortages of N95 FFRs and other PPE are likely in the very near future. Several methods have been successfully tested for decontamination of FFRs without degrading filtration ability or fit of these masks.
Feasibility and safety of decontamination methods has not been definitively established. Optimal methods are likely to vary with numerous factors including local preferences and resource availability.
The time to start stockpiling used PPE is NOW while plans for how best to decontaminate and reuse these vital resources are finalised.
- Wang X, Pan Z, Cheng Z. Association between 2019-nCoV transmission and N95 respirator use. J Hosp Infect [Internet]. 2020 Mar 3; Available from: http://dx.doi.org/10.1016/j.jhin.2020.02.021
- Glen Mayhall C. Hospital Epidemiology and Infection Control. Lippincott Williams & Wilkins; 2012. 1600 p.
- Bischoff WE, Swett K, Leng I, Peters TR. Exposure to influenza virus aerosols during routine patient care. J Infect Dis. 2013 Apr;207(7):1037–46.
- Website [Internet]. [cited 2020 Mar 19]. Available from: http://www.cdc.gov/flu/avianflu/h7n9-infection-control.htm
- Smith JD, MacDougall CC, Johnstone J, Copes RA, Schwartz B, Garber GE. Effectiveness of N95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis. CMAJ. 2016 May 17;188(8):567–74.
- Long Y, Hu T, Liu L, Chen R, Guo Q, Yang L, et al. Effectiveness of N95 respirators versus surgical masks against influenza: A systematic review and meta-analysis. J Evid Based Med [Internet]. 2020 Mar 13; Available from: http://dx.doi.org/10.1111/jebm.12381
- MacIntyre CR, Seale H, Dung TC, Hien NT, Nga PT, Chughtai AA, et al. A cluster randomised trial of cloth masks compared with medical masks in healthcare workers [Internet]. Vol. 5, BMJ Open. 2015. p. e006577–e006577. Available from: http://dx.doi.org/10.1136/bmjopen-2014-006577
- Pillai SK, Beekmann SE, Babcock HM, Pavia AT, Koonin LM, Polgreen PM. Clinician Beliefs and Attitudes Regarding Use of Respiratory Protective Devices and Surgical Masks for Influenza. Health Secur. 2015 Jul;13(4):274–80.
- Nemeth C, Laufersweiler D, Polander E, Orvis C, Harnish D, Morgan SE, et al. Preparing for an Influenza Pandemic: Hospital Acceptance Study of Filtering Facepiece Respirator Decontamination Using Ultraviolet Germicidal Irradiation. J Patient Saf [Internet]. 2020 Mar 12; Available from: http://dx.doi.org/10.1097/PTS.0000000000000600
- CDC. Coronavirus Disease 2019 (COVID-19) [Internet]. Centers for Disease Control and Prevention. 2020 [cited 2020 Mar 20]. Available from: https://www.cdc.gov/coronavirus/2019-ncov/hcp/respirators-strategy/crisis-alternate-strategies.html
- CDC - Recommended Guidance for Extended Use and Limited Reuse of N95 Filtering Facepiece Respirators in Healthcare Settings - NIOSH Workplace Safety and Health Topic [Internet]. 2020 [cited 2020 Mar 20]. Available from: https://www.cdc.gov/niosh/topics/hcwcontrols/recommendedguidanceextuse.html
- Bergman MS, Viscusi DJ, Zhuang Z, Palmiero AJ, Powell JB, Shaffer RE. Impact of multiple consecutive donnings on filtering facepiece respirator fit. Am J Infect Control. 2012 May;40(4):375–80.
- Fisher EM, Noti JD, Lindsley WG, Blachere FM, Shaffer RE. Validation and application of models to predict facemask influenza contamination in healthcare settings. Risk Anal. 2014 Aug;34(8):1423–34.
- van Doremalen N, Bushmaker T, Morris DH, Holbrook MG, Gamble A, Williamson BN, et al. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. N Engl J Med [Internet]. 2020 Mar 17; Available from: http://dx.doi.org/10.1056/NEJMc2004973
- Casanova L, Rutala WA, Weber DJ, Sobsey MD. Coronavirus survival on healthcare personal protective equipment. Infect Control Hosp Epidemiol. 2010 May;31(5):560–1.
- Carias C, Rainisch G, Shankar M, Adhikari BB, Swerdlow DL, Bower WA, et al. Potential demand for respirators and surgical masks during a hypothetical influenza pandemic in the United States. Clin Infect Dis. 2015 May 1;60 Suppl 1:S42–51.
- Institute of Medicine, Board on Health Sciences Policy, Committee on the Development of Reusable Facemasks for Use During an Influenza Pandemic. Reusability of Facemasks During an Influenza Pandemic: Facing the Flu. National Academies Press; 2006. 106 p.
- Lindsley WG, Martin SB Jr, 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;12(8):509–17.
- 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.
- Mills D, Harnish DA, Lawrence C, Sandoval-Powers M, Heimbuch BK. Ultraviolet germicidal irradiation of influenza-contaminated N95 filtering facepiece respirators. Am J Infect Control. 2018 Jul;46(7):e49–55.
- 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.
- Fisher EM, Shaffer RE. A method to determine the available UV-C dose for the decontamination of filtering facepiece respirators. J Appl Microbiol. 2011 Jan;110(1):287–95.
- Kolata G. As Coronavirus Looms, a Hospital Begins Sterilizing Masks for Reuse [Internet]. 2020 [cited 2020 Mar 21]. Available from: https://www.nytimes.com/2020/03/20/health/coronavirus-masks-reuse.html
- Fisher EM, Williams JL, Shaffer RE. Evaluation of Microwave Steam Bags for the Decontamination of Filtering Facepiece Respirators [Internet]. Vol. 6, PLoS ONE. 2011. p. e18585. Available from: http://dx.doi.org/10.1371/journal.pone.0018585
- 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.
- Bergman MS, Viscusi DJ, Heimbuch BK, Wander JD, Sambol AR, Shaffer RE. Evaluation of Multiple (3-Cycle) Decontamination Processing for Filtering Facepiece Respirators [Internet]. Vol. 5, Journal of Engineered Fibers and Fabrics. 2010. p. 155892501000500. Available from: http://dx.doi.org/10.1177/155892501000500405
- Viscusi DJ, Bergman MS, Novak DA, Faulkner KA, Palmiero A, Powell J, et al. Impact of three biological decontamination methods on filtering facepiece respirator fit, odor, comfort, and donning ease. J Occup Environ Hyg. 2011 Jul;8(7):426–36.
- Heimbuch BK, Kinney K, Lumley AE, Harnish DA, Bergman M, Wander JD. Cleaning of filtering facepiece respirators contaminated with mucin and Staphylococcus aureus. Am J Infect Control. 2014 Mar;42(3):265–70.
- Bessesen MT, Adams JC, Radonovich L, Anderson J. Disinfection of reusable elastomeric respirators by health care workers: a feasibility study and development of standard operating procedures. Am J Infect Control. 2015 Jun;43(6):629–34.
- Salter WB, Kinney K, Wallace WH, Lumley AE, Heimbuch BK, Wander JD. Analysis of residual chemicals on filtering facepiece respirators after decontamination. J Occup Environ Hyg. 2010 Aug;7(8):437–45.