Use, re-use or discard? Quantitatively defined variance in the functional integrity of N95 respirators following vaporized hydrogen peroxide decontamination during the COVID-19 pandemic

BACKGROUND

Coronavirus disease 2019 has stretched the ability of many institutions to supply needed personal protective equipment, especially N95 respirators. N95 decontamination and re-use programmes provide one potential solution to this problem. Unfortunately, a comprehensive evaluation of the effects of decontamination on the fit of various N95 models using a quantitative fit test (QNFT) approach is lacking.

AIMS

To investigate the effects of up to eight rounds of vaporized hydrogen peroxide (VHP) decontamination on the fit of N95 respirators currently in use in a hospital setting, and to examine if N95 respirators worn by one user can adapt to the face shape of a second user with no compromise to fit following VHP decontamination.

METHODS

The PortaCount Pro+ Respirator Fit Tester Model 8038 was used to quantitatively define functional integrity, measured by fit, of N95 respirators following decontamination with VHP.

FINDINGS

There was an observable downward trend in the functional integrity of Halyard Fluidshield 46727 N95 respirators throughout eight cycles of decontamination with VHP. Functional integrity of 3M 1870 N95 respirators was reduced significantly after the respirator was worn, decontaminated with VHP, and then quantitatively fit tested on a second user. Furthermore, inconsistencies between qualitative fit test and QNFT results were uncovered that may have strong implications on the fit testing method used by institutions.

CONCLUSIONS

The data revealed variability in the functional integrity of different N95 models after VHP decontamination, and exposed potential limitations of N95 decontamination and re-use programmes.

Decontaminating N95 respirators during the COVID-19 pandemic: simple and practical approaches to increase decontamination capacity, speed, safety and ease of use

Background

The COVID-19 pandemic has caused a severe shortage of personal protective equipment (PPE), especially N95 respirators. Efficient, effective and economically feasible methods for large-scale PPE decontamination are urgently needed.

Aims

(1) to develop protocols for effectively decontaminating PPE using vaporized hydrogen peroxide (VHP); (2) to develop novel approaches that decrease set-up and take-down time while also increasing decontamination capacity; (3) to test decontamination efficiency for N95 respirators heavily contaminated by make-up or moisturizers.

Methods

We converted a decommissioned Biosafety Level 3 laboratory into a facility that could be used to decontaminate N95 respirators. N95 respirators were hung on metal racks, stacked in piles, placed in paper bags or covered with make-up or moisturizer. A VHP® VICTORY™ unit from STERIS was used to inject VHP into the facility. Biological and chemical indicators were used to validate the decontamination process. Findings: N95 respirators individually hung on metal racks were successfully decontaminated using VHP. N95 respirators were also successfully decontaminated when placed in closed paper bags or if stacked in piles of up to six. Stacking reduced the time needed to arrange N95 respirators for decontamination by approximately two-thirds while almost tripling facility capacity. Make-up and moisturizer creams did not interfere with the decontamination process.

Conclusions

Respirator stacking can reduce the hands-on time and increase decontamination capacity. When personalization is needed, respirators can be decontaminated in labelled paper bags. Make up or moisturizers do not appear to interfere with VHP decontamination.

Ability of high-affinity heparin fractions with decreasing affinity for antithrombin III to activate ATIII isoforms

Previous studies investigated the effect of heparin fractions on the rates of thrombin inhibition by naturally occurring antithrombin III (ATIII) isoforms differing in affinity for heparin. Heparin with low-affinity for ATIII increased the rate of thrombin inhibition by the higher affinity isoform about 10-fold more effectively than by the other isoform. This paper reports on the effect of a series of high-affinity heparin fractions with decreasing affinity for ATIII. As affinity decreased, the ability of the heparin fractions to increase the rate of the ATIII-thrombin reactions decreased, and these fractions slightly more effectively increased the rate of thrombin inhibition by the higher-affinity ATIII isoform. The effect of the heparin fractions on the ATIII-factor Xa reactions was also investigated. The activity of the fractions in this reaction also showed a dependence on ATIII-affinity. Studies on the competition of isoforms for immobilized heparin showed that the isoform with higher affinity for ATIII effectively competes with its congener for binding to heparin. The results indicate that heterogeneity in high-affinity heparin results in heterogeneity in affinity for ATIII that is significantly correlated with the ability of the heparin to potentiate ATIII-protease reactions. In spite of about equal activation of the ATIII isoforms by high-affinity heparin, the importance of the higher-affinity isoform is indicated by its ability to compete effectively for these heparin species.