Adapting re‐usable elastomeric respirators to utilise anaesthesia circuit filters using a 3D‐printed adaptor ‐ a potential alternative to address N95 shortages during the COVID‐19 pandemic

  1. D. C. Y. Liu
  2. T. H. Koo
  3. J. K. K. Wong
  4. Y. H. Wong
  5. K. S. C. Fung
  6. Y. Chan
  7. H. S. Lim

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Abstract

The COVID‐19 pandemic has increased the demand for disposable N95 respirators. Re‐usable elastomeric respirators may provide a suitable alternative. Proprietary elastomeric respirator filters may become depleted as demand increases. An alternative may be the virus/bacterial filters used in anaesthesia circuits, if they can be adequately fitted onto the elastomeric respirators. In addition, many re‐usable elastomeric respirators do not filter exhaled breaths. If used for sterile procedures, this would also require modification. We designed a 3D‐printed adaptor that permits elastomeric respirators to interface with anaesthesia circuit filters and created a simple modification to divert exhaled breaths through the filter. We conducted a feasibility study evaluating the performance of our modified elastomeric respirators. A convenience sample of eight volunteers was recruited. Quantitative fit testing, respiratory rate and end‐tidal carbon dioxide were recorded during fit testing exercises and after 1 h of wear. All eight volunteers obtained excellent quantitative fit testing throughout the trial. The mean (SD) end‐tidal carbon dioxide was 4.5 (0.5) kPa and 4.6 (0.4) kPa at baseline and after 1 h of wear (p = 0.148). The mean (SD) respiratory rate was 17 (4) breaths.min −1 and 17 (3) breaths.min −1 at baseline and after 1 h of wear (p = 0.435). Four out of eight subjects self‐reported discomfort; two reported facial pressure, one reported exhalation resistance and one reported transient dizziness on exertion. Re‐usable elastomeric respirators to utilise anaesthesia circuit filters through a 3D‐printed adaptor may be a potential alternative to disposable N95 respirators during the COVID‐19 pandemic.

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  1. ScreenIT

    SciScore for 10.1101/2020.04.10.20061291: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board StatementIRB: We recruited 8 volunteers after ethics approval by the Hospital Authority Research Ethics Committee and written informed consent.
    Consent: We recruited 8 volunteers after ethics approval by the Hospital Authority Research Ethics Committee and written informed consent.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot 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:
    Limitations of our study include our small sample size, short duration of respirator usage and that only 1 model of filter was tested. We chose to test the respirators for 1 hour as most aerosol generating procedures can be completed within this timeframe, after which a lower level of respiratory protection with surgical masks may be adequate. Preliminary testing on one of the authors suggests that the respirator can be worn for 4 hours without significant change in respiratory rate and end-tidal carbon dioxide but further studies are required to evaluate their safety and effectiveness after prolonged usage. Most manufacturers recommend that their breathing system filters can be used for up to 24 hours[8]. In conclusion, we successfully converted a piece of anaesthetic equipment into personal protective equipment that can be used in sterile fields. When N95/FFP3 respirators and NIOSH/CE approved filters are difficult to source, breathing system filters combined with properly fitted reusable elastomeric respirators is a safe alternative.

    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.

    About SciScore

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  2. Version published to 10.1111/anae.15108
  3. Version published to 10.1101/2020.04.10.20061291v1 on medRxiv