Validation of N95 Filtering Facepiece Respirator Decontamination Methods Available at a Large University Hospital
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Abstract
Background
Due to unprecedented shortages in N95 filtering facepiece respirators, healthcare systems have explored N95 reprocessing. No single, full-scale reprocessing publication has reported an evaluation including multiple viruses, bacteria, and fungi along with respirator filtration and fit.
Methods
We explored reprocessing methods using new 3M 1860 N95 respirators, including moist (50%–75% relative humidity [RH]) heat (80–82°C for 30 minutes), ethylene oxide (EtO), pulsed xenon UV-C (UV-PX), hydrogen peroxide gas plasma (HPGP), and hydrogen peroxide vapor (HPV). Respirator samples were analyzed using 4 viruses (MS2, phi6, influenza A virus [IAV], murine hepatitis virus [MHV)]), 3 bacteria (Escherichia coli, Staphylococcus aureus, Geobacillus stearothermophilus spores, and vegetative bacteria), and Aspergillus niger. Different application media were tested. Decontaminated respirators were evaluated for filtration integrity and fit.
Results
Heat with moderate RH most effectively inactivated virus, resulting in reductions of >6.6-log10 MS2, >6.7-log10 Phi6, >2.7-log10 MHV, and >3.9-log10 IAV and prokaryotes, except for G stearothermohphilus. Hydrogen peroxide vapor was moderately effective at inactivating tested viruses, resulting in 1.5- to >4-log10 observable inactivation. Staphylococcus aureus inactivation by HPV was limited. Filtration efficiency and proper fit were maintained after 5 cycles of heat with moderate RH and HPV. Although it was effective at decontamination, HPGP resulted in decreased filtration efficiency, and EtO treatment raised toxicity concerns. Observed virus inactivation varied depending upon the application media used.
Conclusions
Both moist heat and HPV are scalable N95 reprocessing options because they achieve high levels of biological indicator inactivation while maintaining respirator fit and integrity.
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SciScore for 10.1101/2020.04.28.20084038: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Bacterial indicators reveal a potential limitation of VHP. Although both Geobacillus and E. coli showed complete inactivation, S. aureus inactivation was not complete and colonies were always detected on the decontamination …
SciScore for 10.1101/2020.04.28.20084038: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Bacterial indicators reveal a potential limitation of VHP. Although both Geobacillus and E. coli showed complete inactivation, S. aureus inactivation was not complete and colonies were always detected on the decontamination coupons. Notably, there is no standard for S. aureus inactivation with VHP treatment systems, even though it is known to be catalase-positive and it known to be resistant to VHP treatment (22, 23). Our results suggest that S. aureus persistence under VHP may extend to soft fomite surfaces, such as the FFR material evaluated in this study. The implications of this pertaining to hospital infection control needs further consideration, as S. aureus (including MRSA) is a major nosocomial threat. Through this study, we learned that experimental protocols can significantly influence results; specifically, our results demonstrate the impact that virus application medium has on the effectiveness of N95 FFR decontamination. This has practical implications. The FDA EUA recommends treatments achieve >3 log10 removal of viruses, but does not give guidance on the application media used to deposit viruses on the masks. The outcomes of this study suggest that >3 log10 for a specific virus could depend on the deposition solution. With VHP, for example, the MS2 removal in DMEM was greater than 3 log10 under two different treatment conditions, but the MS2 removal in PBS was less than 2 log10 under the same conditions. Viruses propagated in tissue cultures are often deposited...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
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