N95 Filtering Facepiece Respirators Research Articles

Reducing Leak and Increasing Comfort of an N95 Filtering Facepiece Respirator for Aged-Care Workers Using a Customized, Soft, and Compliant Mask Frame

Abstract This prospective cohort study examines the quantitative fit-factor and tolerability impact of a novel custom frame designed to fit beneath N95 filtering facepiece respirators (FFRs) in a healthcare setting. Conducted at a medium-sized metropolitan residential aged care facility (RACF) in South Australia, sixty participants underwent quantitative fit testing while wearing institutional-provided N95 FFRs. Utilizing three-dimensional (3D) face scanning with a proprietary iPhone app, personalized frames were created using flexible silicone foam with a rigid plastic interior “backbone” to ensure compliance and comfort. Following the fitting of custom frames, participants underwent repeat quantitative fit testing using the same style and size of N95 FFRs. Results indicate a remarkable improvement, with 81.5% of participants achieving a pass on quantitative fit testing when using their custom frame in conjunction with the N95 FFRs, compared to a baseline pass rate of only 21.7% (odds ratio (OR) 20.9, 95% confidence interval (CI): 8.26, 58.50, p < 0.001 via logistic regression). Additionally, participants reported a 2.4 times higher level of tolerability when wearing the custom frame with their N95 FFRs compared to using FFRs alone (p < 0.001). In conclusion, the study demonstrates that wearing a customized frame device under an N95 FFR significantly enhances the likelihood of achieving a pass on quantitative fitting and offers a substantially more tolerable experience for wearers. These findings highlight the potential of personalized frame devices to improve respiratory protection efficacy and wearer comfort in healthcare settings.

Health Care Workers' Comfort Ratings for Elastomeric Half-Mask Respirators Versus N95® Filtering Facepiece Respirators During the COVID-19 Pandemic.

Reusable elastomeric half-mask respirators (EHMR) are an alternative to address shortages of disposable respirators. While respirator discomfort has been noted as a barrier to adherence to wearing an N95 filtering facepiece respirator (FFR) among health care personnel (HCP), few have examined EHMR comfort while providing patient care, which was the purpose of this study. Among a cohort of 183 HCP, we prospectively examined how HCP rated EHMR tolerability using the Respirator Comfort, Wearing Experience, and Function Instrument (R-COMFI) questionnaire at Study Week 2 and Week 10. At the completion of the study (Week-12), HCP compared EHMR comfort with their prior N95 FFR use. Overall R-COMFI scores and three subscales (comfort, wear experience, and function) were examined as well as individual item scores. The HCP reported an improved overall R-COMFI score (lower score more favorable, 30.0 vs. 28.7/47, respectively) from Week 2 to Week 10. Many individual item scores improved or remained low over this period, except difficulty communicating with patients and coworkers. The overall R-COMFI scores for the EHMR were more favorable than for the N95 FFR (33.7 vs. 37.4, respectively), with a large proportion of workers indicating their perception that EHMR fit better, provided better protection, and they preferred to wear it in pandemic conditions compared with the N95 FFR. Findings suggest that the EHMR is a feasible respiratory protection device with respect to tolerance. EHMRs can be considered as a possible alternative to the N95 FFR in the health care setting. Future work is needed in the EHMR design to improve communication.

Comparison of the inward leakage rate between N95 filtering facepiece respirators and modified surgical masks during the COVID-19 pandemic.

Owing to shortage of surgical and N95 filtering facepiece respirators (FFRs) during the COVID-2019 pandemic, various masks were developed to prevent infection. This study aimed to examine the inward leakage rate (ILR) of sealed face masks and modified surgical masks using a quantitative fit test and compared it with the ILR of unmodified N95 FFRs. We conducted paired comparisons of ILRs of bent nose-fit wire masks, double masks, and N95 FFRs from October to December 2021. To measure the protective effectiveness of masks, participants wore masks, and the number of particles outside and inside the mask were measured. The ILR was based on the percentage of particles entering the mask using a fit tester. We enrolled 54 participants (20 men and 34 women) in this study. The median ILR for surgical masks without and with a W-shaped bend in the nose-fit wire were 96.44% and 50.82%, respectively. The nose-fit wire adjustment reduced the ILR of surgical masks by a mean of 28.57%, which was significantly lower than the ILR without adjustment (P < 0.001). For double masks, with surgical or polyurethane masks on top of the W-shaped mask, the ILR did not differ significantly from that of N95. Although the filtration performance of double surgical masks matched that of N95 masks, their ILR was notably higher, indicating that double masks do not provide equivalent protection. Wearing N95 masks alone is effective in many cases. However, surgical mask modifications do not guarantee consistent effectiveness. Properly selected, sealed masks with a good fit overcome leakage, emphasizing their crucial role. Without evidence, mask-wearing may lead to unexpected infections. Education based on quantitative data is crucial for preventing adverse outcomes.

Using the Number of N95® Filtering Facepiece Respirator Models as an Indicator of Supply Chain Stability in a US Health-Care System.

Personal protective equipment (PPE) supply chain disruptions force US health-care entities to adopt conservation strategies such as procurement from different respirator manufacturers. This research seeks to better understand how the number of respirator models on hand can serve as an indicator of N95 filtering facepiece respirator (FFR) supply chain stability or disruption. Researchers looked at differences in the mean number of N95 FFR models, averaged weekly, from 10 hospitals in a health-care system over 15 wk from June 1 to September 10, 2020. Participating hospitals entered near-daily PPE inventory data by manufacturer and model number. A linear mixed effect model was run in SPSS v. 26 using a random intercept for hospitals, with week as a fixed predictor and mean number of respirator models (averaged weekly) on hand as the dependent variable. Each week showed a small but significant effect compared with the past week (P < 0.001), where the average weekly number of respirator models on hand decreased. The limited data may indicate a resolution of supply chain disruptions and warrant further investigation. Consequently, the number of respirator models may be applicable as an indicator of supply chain stability and be more easily ascertained and tracked by health-care entities.

Moist heat as a promising method to decontaminate N95 masks: A large scale clinical study comparing four decontamination modalities—moist heat, steam, ultraviolet-C irradiation, and hydrogen peroxide plasma

BackgroundEarly in the COVID-19 pandemic, there was a global shortage of masks. Although mask reprocessing was practiced, no clinical study has assessed systematically the impact of repeated cycles of wear and decontamination on the integrity of N95 filtering facepiece respirators (FFRs). MethodsWe evaluated mask fit assessed by qualitative respirator fit test (QRFT) after each cycle of wear and decontamination, as well as four measures of mask integrity—bacterial filtration efficacy, particle filtration efficacy, differential pressure, and splash resistance through five cycles of wear and decontamination using one of the four modalities (moist heat, steam, ultraviolet-C irradiation, and hydrogen peroxide plasma). ResultsA total of 60.6% (hydrogen peroxide plasma) to 77.5% (moist heat) of the FFRs passed five cycles of wear and decontamination, as assessed by the wearers passing QRFT all five times. Moist heat-decontaminated FFRs retained all technical measures of integrity through all five cycles. ConclusionsThis is the first large-scale study to assess systematically the impact (clinically and quantitatively) on N95 FFR integrity of repeated cycles of wearing followed by decontamination.Our results suggest that moist heat is a promising method for decontaminating N95 FFRs. Performing QRFT after every cycle of wear and decontamination ensures wearer safety. Although there is currently no mask shortage, reprocessing may reduce medical waste and improve sustainability.

Effects of the Use of N95 Masks on the Vital Signs of Healthy Healthcare Workers During the COVID-19 Pandemic: A Hospital-Based Cross-Sectional Study.

The N95 filtering facepiece respirator (FR) is the most commonly recommended respiratory protection used in healthcare settings. However, concerns have been raised about its use because it can increase respiratory resistance and dead space. The primary objective of this study was to determine the effect of wearing N95 masks on the vital signs, i.e., oxygen saturation, pulse rate, and respiratory rate, of the participant health workers. Our secondary objective was to assess the subjective feeling of discomfort when wearing N95 masks. The study participants were healthy healthcare workers taking care of coronavirus disease 2019 (COVID-19)-infected pediatric cases who did at least six hours of continuous shift duty in the pediatric COVID-19 ward at a tertiary care hospital in the eastern part of India. They were evaluated for vital signs at various time intervals while wearing N95 masks. Subjective discomfort at any point in time was also noted. We found a significant variation in the mean oxygen saturation (SpO2) and heart rate (HR) reduction across the four different points. The pair-wise comparison showed a small but significant decrease in the mean SpO2 of 98.3% (1.1)at six hoursas compared with a mean SpO2 of 98.7% (0.9) at three hours. Similarly, a significant increase was noted for a mean HR of 84.7bpm (11.2) at six hours compared with a baseline of 82.3bpm (9.2) and 83.2bpm (8.8) at three hours. The continuous use of an N95 mask leads to a mild increase in respiratory rate. However, heart rate and oxygen saturation vary significantly at different points in time after N95 mask use.

Personalized 3D-printed frames to reduce leak from N95 filtering facepiece respirators: A prospective crossover trial in health care workers

Correctly fitting N95 filtering facepiece respirators (FFRs) have become increasingly important in health care throughout the COVID-19 pandemic. We evaluated the hypothesis that personalized 3D-printed frames could improve N95 FFRs quantitative fit test pass rates and test scores in health care workers (HCWs). HCWs were recruited at a tertiary hospital in Adelaide, Australia (ACTRN 12622000388718). A mobile iPhone camera + app was used to produce 3D scans of volunteers’ faces, which were then imported into a software program to produce personalized virtual scaffolds suited to each user’s face and their unique anatomical features. These virtual scaffolds were printed on a commercially available 3D printer, producing plastic (and then silicone-coated, biocompatible) frames that can be fitted inside existing hospital supply N95 FFR. The primary endpoint was improved pass rates on quantitative fit testing, comparing participants wearing an N95 FFR alone (control 1) with participants wearing the frame + N95 FFR (intervention 1). The secondary endpoint was the fit factor (FF) in these groups, and R-COMFI respirator comfort and tolerability survey scores. N = 66 HCWs were recruited. The use of intervention 1 increased overall fit test pass rates to 62/66 (93.8%), compared to 27/66 (40.9%) for controls. (OR for pFF pass 20.89 (95%CI: 6.77, 64.48, p < 0.001.) Average FF increased, with the use of intervention 1–179.0 (95%CI: 164.3,193.7), compared to 85.2 (95%CI: 70.4,100.0) with control 1. Pass rates and FF were improved with intervention 1 compared to control 1 for all stages of the fit-test: bending, talking, side-to-side, and up-down motion. (p < 0.001 all stages). Tolerability and comfort of the frame were evaluated with the validated R-COMFI respirator comfort score, showing improvement with the frame compared to N95 FFR alone (p = 0.006). Personalized 3D-printed face frames decrease leakage, improve fit testing pass rates and FF, and provide improved comfort compared to the N95 FFR alone. Personalized 3D-printed face frames represent a rapidly scalable new technology to decrease FFR leakage in HCW and potentially the wider population.

Assessing transportation infrastructure impacts from supply chain restructuring for increased domestic production of critical resources

Contrary to past sentiment for globalization in manufacturing and production, the United States (U.S.) and other nations have shown a strong desire for increased domestic manufacturing and production, especially of critical products. While the benefits are many and include increased national security, increased local jobs, greater earnings and improved economies, the costs to support expanded local or regional production capacity may be nontrivial and extend beyond capital investments. That is, there are social costs for a region and nation that should also be considered. This paper proposes an analytical framework and related mathematical procedures for assessing the impacts of supply chain restructuring and domestic capacity expansion needed for increased domestic manufacturing and production on the operation and maintenance of a nation’s roadways. The impacts are given in terms of added traffic congestion, roadway maintenance costs, fuel consumption, emissions and traffic incidents as a function of estimated added domestic truck loads and truck miles required for expanding domestic production capacity. The framework exploits concepts from the mathematical formulation of multi-commodity, multi-echelon, fixed-charge facility location problems. It was applied in a case study involving increased N95 filtering facepiece respirator (FFR) domestic production within the U.S. This application predicts notable impacts due to an increase in U.S.-based N95 FFR production, with sizable impacts stemming from local raw materials and middle products transportation needed to support increased domestic production. Thus, the case study shows the importance of considering the impacts of increased domestic manufacturing and production on infrastructure and the need for the proposed framework and methodologies. The analytical framework has broad utility and can also be used to compare facility siting proposals, as well as localization and regionalization strategies.

Effectiveness of Inexpensive Cloth Facemasks and Their Amendments to Reduce Ambient Particulate Exposures: A Case of Kathmandu, Nepal.

Inexpensive cloth masks are widely used to reduce particulate exposures, but their use became ubiquitous after the outbreak of COVID-19. A custom experimental setup (semiactive at 5.1 m/s airflow rate) was fabricated to examine the efficiency of different types of commercial facemasks collected randomly from street vendors. The sample (N = 27) including (n = 16) cloth masks (CMs), (n = 7) surgical masks (SMs), and (n = 4) N95 filtering facepiece respirators (FFRs), of which SMs and N95 FFRs taken as a standard for efficiency comparison were all tested against ambient aerosols (PM2.5 and PM10 μg/m3). The prototype cloth masks (PTCMs) (N = 5) design was tailored, and their performance was assessed and compared with that of standard commercial masks. The filtering efficiency tested against ambient coarse particulates (PM10) ranged from (5% to 34%) for CMs with an average of 16%, (37% to 46%) for SMs with an average of 42%, (59% to 72%) for PTCMs with an average of 65%, and (70% to 75%) for N95 FFRs with an average of 71%, whereas against fine particulates (PM2.5), efficacy ranged from (4% to 29%) for CMs with an average of 13%, (34% to 44%) for SMs with an average of 39%, (53% to 68%) for PTCMs with an average of 60%, and (68% to 73%) for N95 FFRs with an average of 70%, respectively. The efficiency followed the order N95 FFRs > PTCMs > SMs > CMs showing poor exposure reduction potential in CMs and high exposure reduction potential in N95 FFRs and PTCMs. Amendment in existing CMs using eco-friendly cotton fabric with better facial adherence can protect human health from exposure to fine particulates <2.5 μm and can reduce the risk of micro-plastic pollution caused by polypropylene (PP) facemasks.

Constant vs. cyclic flow when testing face masks and respirators as source control devices for simulated respiratory aerosols

SARS-CoV-2 spreads by infectious aerosols and droplets from the respiratory tract. Masks and respirators can reduce the transmission of infectious respiratory diseases by collecting these aerosols at the source. The ability of source control devices to block aerosols can be tested by expelling an aerosol through a headform using constant airflows, which are simpler, or cyclic airflows, which are more realistic but require more complex methods. Experiments with respirators found that using cyclic vs. constant flows affected the amount of aerosol inhaled, but similar comparisons have not been made for source control devices with exhaled aerosols. We measured the collection efficiencies for exhaled aerosols for two cloth masks, two medical masks with and without an elastic mask brace, a neck gaiter, and an N95 filtering facepiece respirator using 15 L/min and 85 L/min constant and cyclic flows and a headform with pliable skin. The collection efficiencies for the 15 L/min cyclic flow, 15 L/min constant flow, and 85 L/min constant flow were not significantly different in most cases. The apparent collection efficiencies for the 85 L/min cyclic flow were artificially increased by rebreathing and refiltration of the aerosol from the collection chamber. The collection efficiencies correlated well with the fit factors (ρ > 0.95) but not the filtration efficiencies (ρ < 0.54). Our results suggest that the aerosol collection efficiency measurements of source control devices are comparable when testing the devices using either constant or cyclic airflows and that the potential for aerosol rebreathing must be considered when conducting experiments.

Evaluation of Bacterial Contaminants on N95 FFRS after Reuse in Hospital Personnels: A Prospective Study in the Era of COVID-19 Pandemic

Introduction: N95 Filtering Face-piece Respirators (FFRs) prevent the spread of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection and protect medical personnel. It is considered as one of the essential protective equipment. An increased demand for N95 FFRs during the Coronavirus Disease 2019 (COVID-19) pandemic has resulted in shortage crisis for the care of cases arising in hospitals. Therefore, this situation generated the need to implement alternatives like four mask policy that allows reuse of N95 FFRs in settings with limited resources. Aim: To find out the burden of bacterial isolates on N95 FFRs after reuse. Materials and Methods: The present study was a prospective study conducted at Govt. R.D.B.P. Jaipuria hospital, Jaipur, Rajasthan, India, from May 2021 to October 2021 on 526 used N95 FFRs after multiple or extended use by 96 hospital personnel who attended Outpatient Department (OPD) services. Swab samples were collected from both external as well as internal surface of the mask after each use and further subcultured to identify any microorganism present on them. Results: Growth of Gram positive bacilli, and micrococci were found on 499 samples out of total 526 samples. Other bacteria like Pseudomonas spp. and other gram negative were also observed in 19 samples. Furthermore, it was also observed that bacterial load on reused N95 FFRs was mainly commensal flora. Conclusion: Mainly commensal floras were found over internal and external surface of used N95 FFRs. This proves that four mask policy is optimum for judicious use of N95 FFRs and resulted in saving of funds for other more emergency works mainly in OPD settings.

Effect of N95 Filtering Facepiece Respirator on Venous Blood Carbon Dioxide Levels and Hemodynamic Changes in Health Care Workers.

N95 filtering facepiece respirators (FFR) are used by health care workers for prevention of airborne infection, and its use has increased manifolds during COVID-19 pandemic. Prolonged use may result in carbon dioxide (CO2) accumulation, affect hemodynamics, and blood gas values. Although arterial blood gas values accurately measure the blood CO2 levels, venous blood gas values also show acceptable correlation. To evaluate the physiological impact of N95 FFRs on health care workers, including hemodynamic changes and venous blood levels of CO2 during a period of 6 h. Prospective observational study in a tertiary care hospital. The study was conducted on 30 health care workers who performed routine duties while wearing N95 FFR. Venous blood gas values (CO2, pH, and bicarbonate) and vitals (respiratory rate, heart rate, blood pressure, and saturation) were noted at baseline, 2 (T2), and 6 h (T6) after wearing the mask. Discomfort level was also measured on a Visual Analogue Scale (VAS) of 1-10. Repeated measures analysis was done using repeated measures ANOVA or Friedman's test. Group comparisons for continuously distributed data were made using independent sample "t" test or Wilcoxon test. Hemodynamic and blood gas values did not change over time. The VAS for discomfort because of respirator use was 1.33 (1.42) at T2 and 2.77 (1.91) at T6. This was a significant increase in discomfort over time (P = 0.001). About 80% of participants experienced discomfort during this period. N95 FFR did not lead to significant alteration in hemodynamics or change in blood gas values after 6 h of continuous usage. However, discomfort significantly increased over time.

Simple fabrication of an electrospun polystyrene microfiber filter that meets N95 filtering facepiece respirator filtration and breathability standards.

During the global spread of COVID-19, high demand and limited availability of melt-blown filtration material led to a manufacturing backlog of N95 Filtering Facepiece Respirators (FFRs). This shortfall prompted the search for alternative filter materials that could be quickly mass produced while meeting N95 FFR filtration and breathability performance standards. Here, an unsupported, nonwoven layer of uncharged polystyrene (PS) microfibers was produced via electrospinning that achieves N95 performance standards based on physical parameters (e.g., filter thickness) alone. PS microfibers 3-6μm in diameter and deposited in an ~5 mm thick filter layer are favorable for use in FFRs, achieving high filtration efficiencies (≥97.5%) and low pressure drops (≤15 mm H2O). The PS microfiber filter demonstrates durability upon disinfection with hydroxyl radicals (•OH), maintaining high filtration efficiencies and low pressure drops over six rounds of disinfection. Additionally, the PS microfibers exhibit antibacterial activity (1-log removal of E. coli) and can be modified readily through integration of silver nanoparticles (AgNPs) during electrospinning to enhance their activity (≥3-log removal at 25 wt% AgNP integration). Because of their tunable performance, potential reusability with disinfection, and antimicrobial properties, these electrospun PS microfibers may represent a suitable, alternative filter material for use in N95 FFRs.

Filtration performance of three models of N95 filtering facepiece respirators following clinical usage and vaporized hydrogen peroxide decontamination

N95 filtering facepiece respirators (FFRs) are essential personal protective equipment (PPE) for protecting healthcare workers from airborne pathogens. To perform the first large-scale evaluation of particulate filtration efficiency (PFE) of three models of N95 FFRs following clinical usage and vaporized hydrogen peroxide (VHP) decontamination. Three variables were assessed for effect on PFE following VHP decontamination: VHP sterilizer model, N95 respirator model, and prior N95 clinical usage. The VHP sterilizer model and N95 FFR model impacted PFE performance. Worn N95 FFRs had a 91% lower odds of exhibiting ≥95% PFE compared with the control. This work highlights the importance of validating any N95 FFR decontamination programme in its entirety, including prior clinical usage.

Kenneth Theodore Evans

<h3>Abstract</h3> N95 filtering facepiece respirators (FFRs) are essential for the protection of healthcare professionals and other high-risk groups against Coronavirus Disease of 2019 (COVID-19). In response to shortages in FFRs...

Assessing the Fit of N95 Filtering Facepiece Respirators Fitted with an Ear Loop Strap System: A Pilot Study.

Throughout the COVID-19 pandemic, hundreds of millions of people worldwide have become new users of respiratory protective devices. Facemasks and KN95 respirators utilizing an ear loop straps system (ELSS) have recently become popular among occupational and non-occupational populations. Part of this popularity is due to the ease of wearability as compared with traditional devices utilizing two headbands, one worn over the head and the other behind the neck—a universal strap system used in NIOSH-certified N95 filtering facepiece respirators (FFRs). Some users convert the two-strap configuration to an adjustable ELSS. The first objective of this pilot study was to quantitatively characterize how such a conversion impacts the respirator fit. Additionally, a novel faceseal (NFS) technology, which has been previously demonstrated to enhance the fit of N95 FFRs, was deployed to modify the ELSS-converted N95 FFRs. The second objective of this study was to quantify the fit improvement that results from adding the NFS to the ELSS. The study was conducted by performing the Occupational Safety and Health Administration (OSHA)-approved quantitative fit testing (QNFT) on 16 human subjects featuring different facial shapes and dimensions. Three models of cup-shaped N95 FFRs were tested in three versions: the standard version with manufacturer’s strap system, the ELSS-converted, and the ELSS-converted version modified by adding the NFS. QNFT demonstrated that the fit of an N95 FFR featuring the traditional/standard headbands strap system is negatively impacted when this system is converted to an ELSS. The fit of an ELSS-converted respirator can be significantly improved by the addition of the NFS. We found that the FFR model and the strap system version are significant factors affecting the QNFT-determined respirator fit factor (FF), as well as the OSHA QNFT pass rate (FF ≥100). The findings suggest that the current NFS, if further improved, has a potential for developing a ‘universally fitting’ ELSS-equipped N95 FFR that can be used by the general public, the vast majority of whom do not have access to OSHA fit requirements.

Effect of UV-C germicidal irradiation (UVGI) on the structural integrity of N95 and KN95 respirators

This study focuses on reprocessing a group of filtering facepiece respirators (FFR) using ultraviolet germicidal irradiation (UVGI). The aim is to explore the possibility of disinfecting selected KN95 FFRs, in comparison with the N95 FFRs, and assess their viability for reusage. For this purpose, five models of unused N95 and KN95 FFR models obtained from the hospital were exposed to UV-C light using a customized UVGI chamber. The material integrity of treated FFRs was examined in terms of particle penetration and strap tension. The surface morphology of all models is inspected to determine the visible changes of each FFR upon exposure to 1–100 cycles (1 cycle is equivalent to 1 J/cm2 UV dose). The penetration test results indicate that the physical properties of the KN95 and N95 FFRs remain within permissible limits despite being reprocessed by up to 100 cycles (100 J/cm2). Using a microscope, the physical observations also reveal that no visible damage can be seen even after 100 J/cm2 exposure. Apart from the filter bodies, the tension of each strap was also found to not be significantly affected by UV radiation by at least 10 disinfection cycles (10 J/cm2). This confirms that KN95, as well as N95 FFRs, can be subjected to UV treatment as a means of disinfection.

Laboratory assessment of bacterial contamination of a sterile environment when using respirators not traditionally used in a sterile field environment.

During infectious disease outbreaks or pandemics, an increased demand for surgical N95s that create shortages and necessitate the use of alternative National Institute for Occupational Safety and Health (NIOSH)-approved respirators that do not meet the Food and Drug Administration (FDA) additional requirements. The objective of this research was to quantify the level of bacterial contamination resulting from wearing NIOSH-approved respirators lacking the additional protections afforded by surgical N95s. Participants performed simulated healthcare tasks while wearing 5 different respirators approved by the NIOSH. Sterile field contamination resulting from use of a surgical mask cleared by the FDA served as a baseline for comparison with the NIOSH-approved respirators. The bacterial contamination produced by participants wearing the N95 filtering facepiece respirators (FFRs) without an exhalation valve, the powered air-purifying respirators (PAPRs) with an assigned protection factor of 25 or 1,000 was not significantly different compared to the contamination resulting from wearing the surgical mask. The bacterial contamination resulting from wearing the N95 FFR with an exhalation valve and elastomeric half-mask respirator (EHMR) with an exhalation valve was found to be statistically significantly higher than the bacterial contamination resulting from wearing the surgical mask. Overall, NIOSH-approved respirators without exhalation valves maintain a sterile field as well as a surgical mask. These findings inform respiratory guidance on the selection of respirators where sterile fields are needed during shortages of surgical N95 FFRs.

Bayesian network meta-analysis of face masks' impact on human physiology

Several concerns regarding the safety of face masks use have been propounded in public opinion. The objective of this review is to examine if these concerns find support in the literature by providing a comprehensive overview of physiological responses to the use of face masks. We have performed a systematic review, pairwise and network meta-analyses to investigate physiological responses to the use of face masks. The study has been registered with PROSPERO (C RD42020224791). Obtained results were screened using our exclusion and inclusion criteria. Meta-analyses were performed using the GeMTC and meta R packages. We have identified 26 studies meeting our inclusion and exclusion criteria, encompassing 751 participants. The use of face masks was not associated with significant changes in pulsoxymetrically measured oxygen saturation, even during maximal-effort exercises. The only significant physiological responses to the use of face masks during low-intensity activities were a slight increase in heart rate, mildly elevated partial pressure of carbon dioxide (not meeting criteria for hypercarbia), increased temperature of facial skin covered by the mask, and subsequent increase of the score in the rating of heat perception, with N95 filtering facepiece respirators having a greater effect than surgical masks. In high-intensity conditions, the use of face masks was associated with decreased oxygen uptake, ventilation, and RR. Face masks are safe to use and do not cause significant alterations in human physiology. The increase in heart rate stems most likely from increased respiratory work required to overcome breathing resistance. The increase in carbon dioxide is too small to be clinically relevant. An increased rating of heat perception when using face masks results from higher temperature of facial skin covered by the mask.

Design considerations for protective mask development: A remote mask usability evaluation

The design of N95 filtering facepiece respirators (FFRs) continues to pose usability concerns for healthcare workers, which have been exacerbated by the COVID-19 pandemic. The aim of this study was to develop a holistic model to guide mask design improvement. Dental students (n = 38) with experience wearing N95 FFRs participated in a randomized wear trial of three alternative protective masks. A mixed methods survey was used to examine usability of individual mask design components, the relationship of facial/head area to mask features, and overall mask design. Survey results indicated MNmask v1 demonstrated higher usability in seal confidence (M = 3.46), while MNmask v2 performed higher in satisfactory fit (M = 3.50). Design components of nose wire and head/neck bands were the most problematic, while conditions of skin irritation and tight/loose fit created an unfavorable wear experience. To consider healthcare workers’ needs in improving the usability of protective masks, a model is presented to consider characteristics of fit, comfort, material, and design.