Abstract
The World Health Organisation has called for a 40% increase in personal protective equipment manufacturing worldwide, recognising that frontline workers need effective protection during the COVID-19 pandemic. Current devices suffer from high fit-failure rates leaving significant proportions of users exposed to risk of viral infection. Driven by non-contact, portable, and widely available 3D scanning technologies, a workflow is presented whereby a user’s face is rapidly categorised using relevant facial parameters. Device design is then directed down either a semi-customised or fully-customised route. Semi-customised designs use the extracted eye-to-chin distance to categorise users in to pre-determined size brackets established via a cohort of 200 participants encompassing 87.5% of the cohort. The user’s nasal profile is approximated to a Gaussian curve to further refine the selection in to one of three subsets. Flexible silicone provides the facial interface accommodating minor mismatches between true nasal profile and the approximation, maintaining a good seal in this challenging region. Critically, users with outlying facial parameters are flagged for the fully-customised route whereby the silicone interface is mapped to 3D scan data. These two approaches allow for large scale manufacture of a limited number of design variations, currently nine through the semi-customised approach, whilst ensuring effective device fit. Furthermore, labour-intensive fully-customised designs are targeted as those users who will most greatly benefit. By encompassing both approaches, the presented workflow balances manufacturing scale-up feasibility with the diverse range of users to provide well-fitting devices as widely as possible. Novel flow visualisation on a model face is presented alongside qualitative fit-testing of prototype devices to support the workflow methodology.
Highlights
The World Health Organisation has called for a 40% increase in personal protective equipment manufacturing worldwide, recognising that frontline workers need effective protection during the COVID-19 pandemic
The COVID-19 pandemic has highlighted the need for effective respiratory personal protective equipment (PPE), particular FFP3/N99 filtering standards, that may be comfortably worn by front-line workers for prolonged periods
At the time of writing, alert levels in most countries show the virus in ‘general circulation’, and with vaccine deployment in the early stages alongside the threat of further mutations, front-line workers face an ongoing need for filtering PPE
Summary
The World Health Organisation has called for a 40% increase in personal protective equipment manufacturing worldwide, recognising that frontline workers need effective protection during the COVID-19 pandemic. Users with outlying facial parameters are flagged for the fullycustomised route whereby the silicone interface is mapped to 3D scan data These two approaches allow for large scale manufacture of a limited number of design variations, currently nine through the semi-customised approach, whilst ensuring effective device fit. Acquisition of respiratory PPE has become globally competitive with many local jurisdictions concerned about supply availability[2] Against this backdrop this research aims to address the persistent problems of poor respirator fit rates and user comfort by proposing a system exploiting existing accessible digital technologies to rapidly capture and process facial. Manufacturers recommend users performs a ‘fit check’ upon every donning, by covering the filter and inhaling to feel for a good facial seal The reliability of this method is questionable with Lam et al.[5] reporting accuracy of self-checks between 57.5 and 70.5% compared against quantitative results. One design in the study by Lam et al.[5] revealed pass rates of 72.2% vs. 58.1% for males and females respectively and 63% for males compared with 56% for females in the study by Foereland et al.[9]
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