PERSONAL P ROT ECT ION EQUI PMENT
is implemented, it is crucial to determine whether the specific masks used within the hospital are suitable for reprocessing. Please refer to the published data in references (e.g. TU Delft, Austrian Army Research). If the available mask type is classified as “emergency steam sterilisable” it is still necessary to run test batches on site, to verify that no deformation of the mask takes place. The process should be tested on new masks and on masks that were actually used by healthcare workers (HCW). The total workflow depends to some extent upon the country and the responsible person for infection control, as well as the on the available infrastructure. The number of reuses of FFP2 / N95 masks varies currently from one (Austria) to two (Netherlands). Each country is continuing their testing to determine if more reuse cycles are acceptable.
Workflow
In terms of equipment, some hospitals are sterilising masks in separate batches or as a temporary measure dedicating a steriliser specifically for this purpose. Other sites with an existing 121°C / 250°F sterilisation program in place for other goods, have decided to sterilise mixed loads in the same cycle, where it is deemed advantageous for the CSSD workflow. From a regulatory perspective, there are no clear rules in place; however, as long as the masks are packed correctly there should be no concerns for cross-contamination.
Example for reprocessing of FFP respirator masks l Collection of used masks in a container in the ward
l Transport to the CSSD l Inspection of masks by trained and PPE- protected sterilisation technician. Masks that are dirty, damaged or have already been reprocessed the maximum number of times are disposed
l Mark of the mask with an “X” with a
suitable pen, for every reprocessing cycle
l Packaging in pouches for sterilisation – Individually – In packs of four (4) or five (5) units (Individual packing is preferred since it allows every HCW to receive a previously untouched mask)
l Where the hospital has decided to reprocess different categories of mask, then each type must be packed into a suitable sterilisation pouch: – Masks suitable for steam sterilisation – Masks that are only suitable for H2
sterilisation
l Sterilisation at 121˚C / 250˚F with 15-20 minutes holding time
l Delivery of the reprocessed masks in their closed packaging to the respective point of use
l Healthcare workers control the fitting of their mask (as with a new mask). Where the HCW notices a compromised fit, the mask is thrown away.
Some minor physical changes of the reprocessed mask were reported by HCWs, but they also stated that new masks do not always have a perfect fit for all faces. HCWs are generally free to ask for a new mask if they are uncomfortable with the feel or fit of the decontaminated mask.
Some small hospitals have personalised this one-time reuse procedure: l Every second day, an HCW is instructed to place his/her mask into a sterilisation pouch at the end of the working day, and to write their name on it.
l On the following day, the HCW can recollect the mask from the previous day, having been sterilised (in the pouch).
In larger hospitals or when the logistics are difficult, HCWs can also receive reprocessed masks without any
personalisation.Many hospitals have decided to install the steam sterilisation process for reprocessing FFP2 masks as a risk-reduction procedure (for
potential out of stock situations within the next 4-6 weeks). The reprocessed masks are kept in stock in the event that no new masks are available. Some hospitals (NL) have tested the filtration capacities of newly sourced masks (lower quality) and found that some new masks actually had worse filtration properties than steam sterilised high quality masks. This has resulted in the decision to first issue reprocessed (high quality) masks to employees before giving newly sourced (lower quality) masks.
O2
Dry heat disinfection of respiratory masks in Germany Decontamination of respiratory masks with dry heat was identified by various experts as a promising approach especially in terms of material compatibility. As mentioned in the introduction mask manufacturers generally cannot give their guarantee that mask properties remain within the minimum specifications as defined by relevant technical standards (e.g. in terms of filter capacity or in terms of fit) after a certain decontamination procedure. In that aspect hot air disinfection may be seen as an exception at least for masks sold in Europe. The reason is that to obtain a CE mark respiratory masks have to comply with the technical standard EN 149 which requires that a mask can maintain its full functionality after a treatment of 24 hours at 70˚C dry heat.
At the same time there is published scientific evidence (e.g. Kampf et al 2020) that SARS-CoV-2 virus and SARS-CoV-1 virus infectivity is reduced by at least 4 log10 under conditions of 60°C / 140°F for 30 minutes, 65°C / 149°F for 15 minutes or 80°C / 176°F for 1 minute respectively. A limiting factor is that most of the underlying data was produced with virus in suspension (i.e. moist heat) versus in hot air (dry heat). Kampf et al argue that for the case of the SARS-CoV-2 it appears unlikely that there is a major difference between dry heat and moist heat in terms of inactivation efficacy. When making this assumption it is important to emphasise that the masks need to be already completely dry at the beginning of the treatment time. As long as there is residual water present there will be a cooling effect by the evaporating water and thus no thermal equilibrium between the heating medium (air) and the object to be heated (masks). The inactivation mechanism was reported to be thermal aggregation of SARS- CoV membrane protein which was shown to completely denaturate at about 55˚C for 10 minutes.
Single-use surgical gown in sterilisation pouch after steam sterilisation. OCTOBER 2020
If these two factors (dry heat stability of masks and heat sensitivity of the virus) are combined it should be possible to design a dry heat decontamination protocol that at least inactivates SARS-CoV-2 with a sufficient level of safety while having
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