One size fits all?: A simulation framework for face-mask fit on population-based faces

Perceived benefits, barriers, perceptions, and readiness to use exoskeletons in the construction industry: Differences by demographic characteristics

Exoskeletons (EXOs) are a promising wearable intervention to reduce work-related musculoskeletal disorder risks among construction workers. However, the adoption of EXOs may differ with demographic characteristics. Survey data (n = 361) were collected from construction industry stakeholders and a summation score method was used to summarize respondent's benefits and barriers to EXO use, along with perceptions and readiness to use. Responses were stratified by race (White vs. non-White), sex (male vs. female), and age (<47 years vs. ≥47 years). Both a higher Benefits score and a higher Perceptions score were significantly and positively associated with a higher Readiness to Use score. There were also significant differences in perceived barriers to EXO use by race and sex. These results demonstrate substantial interest in EXO use but also emphasize the need to ensure proportionate access to the potential benefits of EXO technology.

Initial evidence that skin health deteriorates for younger age groups and with increased daily use of face masks for healthcare professionals at a dental hospital in the United Kingdom

OBJECTIVE

To determine the incidence and site of any adverse effects of wearing face masks via an online questionnaire.

METHODS

Healthcare workers in a dental hospital who wear Respiratory Protective Equipment (RPE) were invited to participate. An online questionnaire was used to identify adverse effects as a result of wearing face masks and possible remedies.

RESULTS

Red marks (72.1 %) and indentations (66.7 %) were the most frequently reported issues with increased use of the RPE. The bridge of the nose and cheeks were the most frequently reported sites of facial skin problems, such as blanching (54.1 % and 42.2 %, respectively) and pressure damage (42.3 % and 24.3 %, respectively). Overall perceived facial skin health deteriorated strongly and significantly (P < 0.001) following the use of RPE, where the mean skin health score (0 = best possible skin health and 10 = worst possible skin health) increased from 2.68 to 4.76. Broadly, there was increased discomfort with increased hours of use of RPE per day (P = 0.049). 71 % of participants said that they generally felt safe or very safe using RPE.

CONCLUSION

The facial skin health of respondents deteriorated strongly after the use of RPE. Guidelines for using RPE should be made clearer. A greater range of face mask sizes or bespoke masks should be made available to improve the fit and wearability, as well as to reduce the frequency and incidence of surface skin problems.

CLINICAL SIGNIFICANCE

This study has identified the factors influencing adverse skin reactions from face mask use, which can be used to inform face mask designers and manufacturers to improve the fit and wearability of face masks.

Designing better cloth masks: The effect of fabric and attachment-style on discomfort

Cloth masks are a tool for controlling community transmission during pandemics, as well as during other outbreak situations. However, cloth masks vary in their designs, and the consequences of this variability for their effectiveness as source control have received little attention, particularly in terms of user discomfort and problematic mask-wearing behaviors. In the present studies, common design parameters of cloth masks were systematically varied to ascertain their effect(s) on the subjective discomfort and frequency of problematic mask-wearing behaviors, which detract from the effectiveness of cloth masks as source control. The type of fabric comprising a mask (flannel or twill made of 100% cotton) and the attachment-style of a mask (i.e., ear loops or fabric ties) were varied in adults (18 to 65 years) and children (ages 6 to 11 years). For adults, ear loops were less comfortable than ties (p = .035) and were associated with greater face- (p = .005) and mask-touching (p = .001). Children, however, found flannel masks to be more breathable than twill masks (p = .007) but touched their masks more frequently when wearing a mask made of flannel than twill (p = .033). Common design parameters of cloth masks not only affect user discomfort and behavior but do so differently in adults and children. To improve the effectiveness of cloth masks as source control, the present studies highlight the importance of measuring the effect(s) of design decisions on user discomfort and behavior in different populations.

A combined imaging, deformation and registration methodology for predicting respirator fitting

N95/FFP3 respirators have been critical to protect healthcare workers and their patients from the transmission of COVID-19. However, these respirators are characterised by a limited range of size and geometry, which are often associated with fitting issues in particular sub-groups of gender and ethnicities. This study describes a novel methodology which combines magnetic resonance imaging (MRI) of a cohort of individuals (n = 8), with and without a respirator in-situ, and 3D registration algorithm which predicted the goodness of fit of the respirator. Sensitivity analysis was used to optimise a deformation value for the respirator-face interactions and corroborate with the soft tissue displacements estimated from the MRI images. An association between predicted respirator fitting and facial anthropometrics was then assessed for the cohort.

The Adverse and Advantage Effects of Wearing a Facemask in Thai Children: A Survey During the COVID-19 Pandemic

BACKGROUND

There is little information on facemask use during the COVID-19 pandemic in the pediatric population. This became the main purpose of the present study to investigate demographic data of facemask wearing in children, types, and length of facemask, as well as the benefits, drawbacks, and negative consequences of facemask wearing in this population.

METHODS

A cross-sectional study was conducted using a structured questionnaire sent via Google Forms. Caregivers for consecutive convenience were asked in the survey (parents of children under the age of 18).

RESULTS

A total number of 706 children were enrolled. There were 320 boys (45.33%), and 386 girls (54.67%). The children's ages range between 4 months and 18 years, with a median age of 9 years. A surgical mask (549, 77.76%) was the most frequent type of facemask in the study population, followed by a cloth mask (86, 12.18%). Facemasks have been shown to be beneficial in the pediatric population. When compared to a former time when facemasks were not used routinely, there were considerably fewer respiratory infections, reduced diarrhea symptoms, and a drop in hospital admissions. In 317 cases (44.9%), children were shown to have negative consequences from wearing facemasks. The most prevalent adverse effect observed in the study population was non-cutaneous (respiratory discomfort/breathing difficulty) which were found in 240 cases (33.99%). Double masking method (surgical + surgical) and wearing a facemask oversize revealed a higher risk in the presence of facemask adverse effects, whereas wearing a proper size facemask reduces the risk of adverse effects from facemask use in children (Adjusted OR [95% CI] = 0.55 [0.38-0.78], P .0003).

CONCLUSIONS

Wearing a proper-size facemask reduces the risk of adverse effects from facemask use in children. The future suggestion of an appropriate facemask size for a certain age will aid in the avoidance of facemask adverse effects in the pediatric population.

How long and effective does a mask protect you from an infected person who emits virus-laden particles: By implementing one-dimensional physics-based modeling

SARS-CoV-2 spreads via droplets, aerosols, and smear infection. From the beginning of the COVID-19 pandemic, using a facemask in different locations was recommended to slow down the spread of the virus. To evaluate facemasks' performance, masks' filtration efficiency is tested for a range of particle sizes. Although such tests quantify the blockage of the mask for a range of particle sizes, the test does not quantify the cumulative amount of virus-laden particles inhaled or exhaled by its wearer. In this study, we quantify the accumulated viruses that the healthy person inhales as a function of time, activity level, type of mask, and room condition using a physics-based model. We considered different types of masks, such as surgical masks and filtering facepieces (FFPs), and different characteristics of public places such as office rooms, buses, trains, and airplanes. To do such quantification, we implemented a physics-based model of the mask. Our results confirm the importance of both people wearing a mask compared to when only one wears the mask. The protection time for light activity in an office room decreases from 7.8 to 1.4 h with surgical mask IIR. The protection time is further reduced by 85 and 99% if the infected person starts to cough or increases the activity level, respectively. Results show the leakage of the mask can considerably affect the performance of the mask. For the surgical mask, the apparent filtration efficiency reduces by 75% with such a leakage, which cannot provide sufficient protection despite the high filtration efficiency of the mask. The facemask model presented provides key input in order to evaluate the protection of masks for different conditions in public places. The physics-based model of the facemask is provided as an online application.

A critical review on the role of leakages in the facemask protection against SARS-CoV-2 infection with consideration of vaccination and virus variants

The protection provided by facemasks has been extensively investigated since the beginning of the SARS-CoV-2 outbreak, focusing mostly on the filtration efficiency of filter media for filtering face pieces (FFP), surgical masks, and cloth masks. However, faceseal leakage is a major contributor to the number of potentially infectious airborne droplets entering the respiratory system of a susceptible individual. The identification of leaking spots and the quantification of leaking flows are crucial to estimate the protection provided by facemasks. This study presents a critical review on the measurement and calculation of facemask leakages and a quantitative analysis of their role in the risk of SARS-CoV-2 infection. It shows that the pairing between the mask dimensions and the wearer's face is essential to improve protection efficiency, especially for FFP2 masks, and summarizes the most common leaking spots at the interface between the mask and the wearer's face. Leakage is a crucial factor in the calculation of the protection provided by facemasks and outweighs the filtration performances. The fit factors measured among mask users were summarized for different types of face protection. The reviewed data were integrated into a computational model to compare the mitigation impact of facemasks with vaccination with consideration of new variants of SARS-CoV-2. Combining a high adoption rate of facemasks and a high vaccination rate is crucial to efficiently control the spread of highly infectious variants.

Bridge the gap: correlate face mask leakage and facial features with 3D morphable face models

BACKGROUND

Face masks have been proven to be effective in protecting the public against airborne transmitted diseases when fitted appropriately. However, for homemade cloth masks and surgical masks, the fit is often poor, allowing viruses to escape through the gap.

OBJECTIVE

This work aims to identify the correlation between the mask leakage, mask configurations, and individual's facial features.

METHODS

A novel locally morphing 3D face model, and a minimum-energy-based mask deployment model are used to systematically examine the mask fit for a large cohort of exemplars.

RESULTS

The results show that the mask size and tuck-in ratio, along with selective facial features, especially nose height and chin length, are key factors determining the leakage location and extent. A polynomial regression model is presented for mask fitness based on localized facial features.

SIGNIFICANCE

This study is a complete pipeline to test various masks on a wide range of faces with controlled modification of distinct regions of the face, which is difficult to achieve with human subjects, and provide knowledge on how the masks should be designed in the future.

IMPACT STATEMENT

The face mask "fit" affects the mask's efficacy in preventing airborne transmission. To date, research on the face mask fit has been conducted mainly using experiments on limited subjects. The limited sample size in experimental studies makes it hard to reach a statistical correlation between mask fit and facial features in a population. Here, we employ a novel framework that utilizes a morphable face model and mask's deployment simulation to test mask fit for many facial characteristics and mask designs. The proposed technique is an important step toward enabling personalized mask selection with maximum efficacy for society members.

Influence of expiratory flow pulsatility on the effectiveness of a surgical mask

BACKGROUND

Expiratory events, such as coughs, are often pulsatile in nature and result in vortical flow structures that transport expiratory particles. The World Health Organization recommends wearing face masks to reduce the airborne transmission of diseases such as SARS-CoV-2 (COVID-19). However, masks are not perfect as flow leakage occurs around the mask, and their effectiveness under realistic (multi-pulse) coughing conditions is unknown.

OBJECTIVE

To assess the influence of expiratory flow pulsatility on the effectiveness of a surgical face mask by quantifying and classifying the flow leakage around the mask.

METHODS

A custom-built pulsatile expiratory flow simulator is used to generate single- and multi-pulsed coughing events. Flow visualization and particle image velocimetry are used to assess the penetration distance and volume of leakage flow at the top and sides of a surgical mask.

RESULTS

Leakage flow velocity profiles at the top and sides of a surgical mask take the form of a wall jet and a free-shear jet, respectively. Multi-pulsed expiratory flow events are found to generate greater leakage flow around the mask than single-pulsed events.

SIGNIFICANCE

For the first time, the leakage volume of a surgical mask is shown to be correlated to the pulsatile nature of a cough.

IMPACT STATEMENT

The novelties of this study are: First, flow field measurements are used to quantify and classify the leakage flow fields around the top and sides of a surgical mask, providing a benchmark for quantitative modeling of leakage flow velocity profiles. Second, the influence of pulsatility on the effectiveness of surgical face masks is studied by quantifying the leakage volume. For the first time, the leakage volume of a surgical mask is shown to be correlated to the pulsatile nature of a cough, as multi-pulsed expiratory flow events are found to generate greater flow leakage around the mask than single-pulsed events.

Investigation of the Role of Face Shape on the Flow Dynamics and Effectiveness of Face Masks

Due to the COVID-19 pandemic, face masks have been used extensively in society. The effectiveness of face masks depends on their material, design, and fit. With much research being focused on quantifying the role of the material, the design and fit of masks have been an afterthought at most. Recent studies, on the other hand, have shown that the mask fit is a significant factor to consider when specifying the effectiveness of the face mask. Moreover, the fit is highly dependent on face topology. Differences in face types and anthropometrics lead to different face mask fit. Here, computational fluid dynamics simulations employing a novel model for porous membranes (i.e., masks) are used to study the leakage pattern of a cough through a face mask on different faces. The three faces studied (female, male, and child) are characteristic faces identified in a previous population study. The female face is observed to have the most leakage through the periphery of the mask, which results in the lowest fitted filtration efficiency of the three faces. The male and child faces had similar gap profiles, leakage and fitted filtration efficiencies. However, the flow of the three faces differs significantly. The effect of the porosity of the mask was also studied. While all faces showed the same general trend with changing porosity, the effect on the child’s face was more significant.

Technological scouting of bi-material face masks: experimental analysis on real faces

The need for personal protective equipment rapidly grew during the COVID-19. Companies had to face problems related to their products' sustainability, adherence, and comfortability. Designing a face mask with proper adherence and comfortability in wearing and breathing became a matter of great importance. In this work, the adherence of an innovative face mask and its comfortability were experimentally tested with real faces, considering the deformation of the mask and the soft facial tissues. A stereophotogrammetric acquisition was made of the face with the face mask during these tests. A comparison between the geometries of the face and the mask, undeformed and deformed, gave the respective deformations. The force applied by the mask to the face was calculated, measuring the elastic strain of the mask bands during wearing and the deformation.

Quantitative modeling of the impact of facemasks and associated leakage on the airborne transmission of SARS-CoV-2

The ongoing worldwide outbreak of COVID-19 has set personal protective equipment in the spotlight. A significant number of countries impose the use of facemasks in public spaces and encourage it in the private sphere. Even in countries where relatively high vaccination rates are achieved at present, breakthrough infections have been frequently reported and usage of facemasks in certain settings has been recommended again. Alternative solutions, including community masks fabricated using various materials, such as cotton or jersey, have emerged alongside facemasks following long-established standards (e.g., EN 149, EN 14683). In the present work, we present a computational model to calculate the ability of different types of facemasks to reduce the exposure to virus-laden respiratory particles, with a focus on the relative importance of the filtration properties and the fitting on the wearer's face. The model considers the facemask and the associated leakage, the transport of respiratory particles and their accumulation around the emitter, as well as the fraction of the inhaled particles deposited in the respiratory system. Different levels of leakages are considered to represent the diversity of fittings likely to be found among a population of non-trained users. The leakage prevails over the filtration performance of a facemask in determining the exposure level, and the ability of a face protection to limit leakages needs to be taken into account to accurately estimate the provided protection. Filtering facepieces (FFP) provide a better protection efficiency than surgical and community masks due to their higher filtration efficiency and their ability to provide a better fit and thus reduce the leakages. However, an improperly-fitted FFP mask loses a critical fraction of its protection efficiency, which may drop below the protection level provided by properly-worn surgical and community masks.