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Comparing mask fit and usability of traditional and nanofibre N95 filtering facepiece respirators before and after nursing procedures

  • L.K.P. Suen
    Correspondence
    Corresponding author. Address: Squina International Centre for Infection Control, School of Nursing, The Hong Kong Polytechnic University, HungHom, Hong Kong. Tel.: +852 2766 7475; fax: +852 2364 9663.
    Affiliations
    Squina International Centre for Infection Control, School of Nursing, The Hong Kong Polytechnic University, HungHom, Hong Kong
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  • Y.P. Guo
    Affiliations
    Squina International Centre for Infection Control, School of Nursing, The Hong Kong Polytechnic University, HungHom, Hong Kong
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  • S.S.K. Ho
    Affiliations
    Squina International Centre for Infection Control, School of Nursing, The Hong Kong Polytechnic University, HungHom, Hong Kong
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  • C.H. Au-Yeung
    Affiliations
    Squina International Centre for Infection Control, School of Nursing, The Hong Kong Polytechnic University, HungHom, Hong Kong
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  • S.C. Lam
    Affiliations
    Squina International Centre for Infection Control, School of Nursing, The Hong Kong Polytechnic University, HungHom, Hong Kong
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Open AccessPublished:September 20, 2019DOI:https://doi.org/10.1016/j.jhin.2019.09.014

      Summary

      Background

      The reliability of N95 filtering facepiece respirators (FFRs) depends on correct fitting. The perceived usability of FFRs is equally important because discomfort during usage may affect compliance. Body movements during nursing procedures may also increase the risk of face seal leakage.

      Aim

      To evaluate the mask fit and usability of the best-fitting 3M N95 FFR and the nanofibre N95 FFR before and after nursing procedures. The physical properties of these FFRs were also examined.

      Methods

      This experimental study had a one-group multiple comparison design. In total, 104 nursing students participated, and performed nursing procedures for 10 min when wearing the best-fitting 3M FFR and the nanofibre FFR. Mask fit and perceived usability of the FFRs were evaluated.

      Findings

      More participants failed to obtain a fit factor ≥100 when using the best-fitting 3M FFR than when wearing the nanofibre FFR (33.7% vs 21.2%) after the procedures (P=0.417). The nanofibre FFR also demonstrated higher usability than the 3M FFRs in terms of facial heat, breathability, facial pressure, speech intelligibility, itchiness, difficulty of maintaining the mask in place, and comfort level (P<0.001). The nanofibre FFR was also lighter, thinner and had slightly higher bacterial filtration efficiency than the 3M FFRs.

      Conclusion

      The nanofibre FFR demonstrated significantly better usability than the 3M FFRs. None of the respirators were able to provide consistent protection for the wearer, as detected by face seal leakage after performing nursing procedures. Further improvement in the prototype design is needed to increase compliance and ensure the respiratory protection of users.

      Keywords

      Introduction

      The N95 particulate filtering facepiece respirator (FFR) has been recommended by public health organizations as a tool to reduce the transmission of airborne infectious diseases (e.g. tuberculosis, measles and chickenpox) and to provide protection from other aerosol-generating procedures with infectious patients [
      National Institute for Occupational Safety and Health
      Workplace solutions: preparedness through daily practice: the myths of respiratory protection in healthcare.
      ]. The numerical designation ‘95’ indicates the ability to filter at least 95% of particles with the most penetrating particle size range of 0.3 μm under test conditions [
      National Institute for Occupational Safety and Health
      42 CFR Part 84 Respiratory protective devices.
      ]. Reliability of N95 FFRs depends on correct fitting [
      National Institute for Occupational Safety and Health
      42 CFR Part 84 Respiratory protective devices.
      ,
      • Lam S.C.
      • Lee J.K.
      • Yau S.Y.
      • Charm C.Y.
      Sensitivity and specificity of the user-seal-check in determining the fit of N95 respirators.
      ]. Healthcare workers (HCWs) who use a respirator in their workplace must undergo training on proper usage and pass a fit test [
      • Lee M.C.
      • Takaya S.
      • Long R.
      • Joffe A.M.
      Respirator-fit testing: does it ensure the protection of healthcare workers against respirable particles carrying pathogens?.
      ]. HCWs may be infected in clinical settings via exposure to a minimal amount of micro-organisms. Thus, the leakage of protective respirators must be prevented to ensure adequate protection for users [
      • Clayton M.
      • Vaughan N.
      Fit for purpose: the role of fit testing in respiratory protection.
      ,
      • Roberge R.J.
      • Monaghan W.D.
      • Palmiero A.J.
      • Shaffer R.
      • Bergman M.S.
      Infrared imaging for leak detection of N95 filtering facepiece respirators: a pilot study.
      ].
      To fulfil the stringent requirements, manufacturers should ensure that the thickness of a respirator must be increased and fibre diameter must be decreased [
      • Li J.
      • Gao F.
      • Liu Q.
      • Zhang Z.
      Needleless electro-spun nanofibers used for filtration of small particles.
      ]. Hence, the traditional N95 FFRs are thicker than surgical masks, thereby compromising breathability [
      • Baig A.S.
      • Knapp C.
      • Eagan A.E.
      • Radonovich Jr., L.J.
      Health care workers’ views about respirator use and features that should be included in the next generation of respirators.
      ,
      • Gralton J.
      • McLaws M.L.
      Protecting healthcare workers from pandemic influenza: N95 or surgical masks?.
      ,
      • Roberge R.J.
      • Coca A.
      • Williams W.J.
      • Palmiero A.J.
      • Powell J.B.
      Surgical mask placement over N95 filtering facepiece respirators: physiological effects on healthcare workers.
      ]. Although surgical masks have been recommended as part of universal precautions in the clinical setting, they cannot provide adequate protection for users under specific contagious conditions [
      National Institute for Occupational Safety and Health Science
      N95 respirators and surgical masks.
      ]. Discomfort experienced by HCWs who wear N95 respirators is often associated with the tight-fit models [
      • Gosch M.E.
      • Shaffer R.E.
      • Eagan A.E.
      • Roberge R.J.
      • Davey V.J.
      • Radonovich Jr., L.J.
      B95: a new respirator for health care personnel.
      ]. A variety of sensations and experiences, such as facial pressure, facial heat, facial movement or skin itchiness, may lead to discomfort, thereby affecting compliance during usage [
      National Institute for Occupational Safety and Health
      Workplace solutions: preparedness through daily practice: the myths of respiratory protection in healthcare.
      ,
      • Baig A.S.
      • Knapp C.
      • Eagan A.E.
      • Radonovich Jr., L.J.
      Health care workers’ views about respirator use and features that should be included in the next generation of respirators.
      ]. Perceived exertion, perceived shortness of air, complaints of headache or lightheadedness, difficulty in communication and respirator adjustments by users may increase over time [
      • Rebmann T.
      • Carrico R.
      • Wang J.
      Physiologic and other effects and compliance with long-term respirator use among medical intensive care unit nurses.
      ]. Discomfort associated with the device may also interfere with the occupational duties of workers [
      • Shenal B.V.
      • Radonovich Jr., L.J.
      • Cheng J.
      • Hodgson M.
      • Bender B.S.
      Discomfort and exertion associated with prolonged wear of respiratory protection in a health care setting.
      ]. Therefore, the perceived usability of FFRs is as important as mask fit. Evidently, the improvement and modification of FFRs warrants further investigation to increase the acceptance of this tool and improve the compliance rates of users.
      Electrospinning technology has enabled the Nano and Advanced Materials Research Institute of Hong Kong (NAMI), a research and development centre designated by the Innovation and Technology Commission of the Government of Hong Kong Special Administrative Region, to successfully combine meltblown and spunbond fibres with nanofibres with diameters ranging from a few nanometres to a few hundred nanometres, which cannot be obtained via traditional fabrication techniques. However, an experimental study illustrated that body movements during nursing procedures may increase the risk of face seal leakage [
      • Suen L.K.P.
      • Yang L.
      • Ho S.S.K.
      • Fung K.H.K.
      • Boost M.V.
      • Wu C.S.T.
      • et al.
      Reliability of N95 respirators for respiratory protection before, during and after nursing procedures.
      ]. Thus, the purpose of the current study was to evaluate the mask fit and usability of traditional N95 and nanofibre N95 FFRs before and after nursing procedures. In addition, the physical properties of FFRs under testing were examined.

      Methods

      This experimental study had a one-group multiple comparison design.

      Respirators

      The three 3M models tested were 1860, 1860S and 1870+ (3M, St Paul, MN, USA); these are the most commonly used FFR models in hospitals under the Hospital Authority of Hong Kong. For the N95 nanofibre FFR, the prototype was composed of an ultrafine fibrous coating on a microfibrous substrate. This ultrafine fibrous coating comprised partially gelled submicron fibres interweaved with nanofibres. The material and structural details of the nanofibre FFR can be found in US10201198B2 (filed on 10th December 2015, granted on 12th February 2019).

      Study participants

      The participants were a group of students from a university baccalaureate nursing programme. They had no prior experience in using an N95 FFR in the clinical setting, but had received formal training in performing the nursing procedures tested [
      • Suen L.K.P.
      • Yang L.
      • Ho S.S.K.
      • Fung K.H.K.
      • Boost M.V.
      • Wu C.S.T.
      • et al.
      Reliability of N95 respirators for respiratory protection before, during and after nursing procedures.
      ]. This inclusion criterion ensured that prior experience in using an N95 FFR would not be a confounder of the outcome [
      • Hannum D.
      • Cycan K.
      • Jones L.
      • Stewart M.
      • Morris S.
      • Markowitz S.M.
      • et al.
      The effect of respirator training on the ability of healthcare workers to pass a qualitative fit test.
      ]. Subjects who were smokers or drinkers (apart from being social drinkers) were excluded because alcohol and smoking may have negative effects on exercise performance and breathing capacity. Subjects who were pregnant, had a beard or were diagnosed as having respiratory problems were also excluded.

      Procedures for mask fitness and usability evaluation

      The experiments were conducted at the ‘Mask Fitting and Personal Protective Equipment Skill Station’ of the university. To minimize variation in concentration of the suspended particles and dust in the environment, all procedures were performed in a standardized setting at a mean temperature of 23.05 °C and humidity of 57.08% [
      • Lam S.C.
      • Lui A.K.
      • Lee L.Y.
      • Lee J.K.
      • Wong K.F.
      • Lee C.N.
      Evaluation of the user seal check on gross leakage detection of 3 different designs of N95 filtering facepiece respirators.
      ]. Ethical approval was obtained from the Human Research Ethics Review Committee of The Hong Kong Polytechnic University (Reference No. HSEARS20150717001), which approved all experimental protocols adopted in this study. All methods used were implemented in accordance with the relevant guidelines and regulations. Participation in this study was voluntary. Written informed consent was obtained from each subject following explanation of the risks and benefits of their participation.
      Prior to the trial, sociodemographic data of the participants, including sex, age, body mass index (kg/m2), years of study and clinical experience (in weeks), were collected. After briefing the participants on the protocol for the proper donning of the N95 FFRs, every participant underwent a quantitative fit test (QNFT) using Portacount Plus (TSI Inc., Shoreview, MN, USA) [
      • Lam S.C.
      • Lee J.K.
      • Lee L.Y.
      • Wong K.F.
      • Lee C.N.
      Respiratory protection by respirators: the predictive value of user seal check for the fit determination in healthcare settings.
      ]. Thereafter, the best-fitting 3M FFR was identified from the three commonly used FFR models in hospitals under the Hospital Authority of Hong Kong, namely, 1860, 1860S and 1870+ (3M). The best-fitting 3M FFR model for each participant was confirmed based on the fit factor readings. All participants were required to perform the user seal check to ensure that no leakage would occur before the procedure [
      • Lam S.C.
      • Lee J.K.
      • Yau S.Y.
      • Charm C.Y.
      Sensitivity and specificity of the user-seal-check in determining the fit of N95 respirators.
      ].
      The trial for comparing the two respirators (i.e. best-fitting 3M FFR and nanofibre FFR) commenced after identifying the best-fitting 3M FFR model for the individual participants. The sequence of wearing FFRs was determined using a computer-generated randomized table to ensure that user performance was unaffected by the experience of receiving either the 3M N95 FFR or nanofibre N95 FFR during the experiment. The baseline QNFT measurements of face seal leakage were taken after each subject wearing the first FFR had remained seated for 10 min. Thereafter, the participants performed two nursing procedures for 10 min. Suctioning and Ryle's tube insertion procedures may induce aerosol generation in clinical settings. In addition, these procedures might involve patient positioning and procedures that might increase the level of physical exertion, thus challenging the wearability, comfort level and filtration capacity of the FFRs under testing. The performance of all participants should be consistent, given that everyone had received prior training in performing these procedures. After the procedures were completed, the participants were asked to rest for 5 min before QNFT readings were collected again.
      A 30-min rest was provided before testing the second FFR in order to avoid fatigue that may affect performance. The participants were blinded to the type of FFR being used to prevent bias in evaluating the usability level of the respirators. They were likewise instructed that regardless of the test outcome, no re-adjustment or re-donning of FFRs should be performed during and after the nursing procedures. Figure 1 shows the details of the data collection procedures.
      Figure 1
      Figure 1Data collection procedures. FFR, filtering facepiece respirator; QNFT, quantitative fit testing.
      When evaluating usability, the subjects were asked to evaluate eight perceptions, including facial heat, breathability, facial pressure, speech intelligibility (ease in talking), itchiness, difficulty of maintaining the mask in place, comfort on ear lobe and overall comfort level after wearing each FFR. Each parameter was rated using a five-point scale from 1 (very unsatisfactory) to 5 (very satisfactory). This scale was modified from the usability scale of Meyer et al. (1997) [
      • Meyer J.P.
      • Hery M.
      • Herrault J.
      • Hubert G.
      • Francois D.
      • Hecht G.
      • et al.
      Field study of subjective assessment of negative pressure half-masks: influence of the work conditions on comfort and efficiency.
      ]. Upon completion of the experiment, a shopping coupon of HK$100 (approximately ₤10) was provided to the participants as a token of appreciation for their participation.

      Examination of physical properties of the respirators

      The following physical properties of the tested FFRs were examined: weight (g/m2), thickness (mm), air permeability [ventilation resistance R (kPa s/m)], cumulative one-way transport capacity (OWTC), overall moisture management capacity (OMMC) and bacterial filtration efficiency (BFE).
      Fabric weight was defined as the mass per unit area of the fabric and was measured in g/m2 in accordance with the ASTM D3776 Standard Method (2017) [
      ASTM D3776 / D3776M-09a
      Standard test methods for mass per unit area (weight) of fabric.
      ]. Fabric thickness was defined as the distance between two fabric surfaces under a specified applied pressure [
      • Rose S.
      Textiles and fashion: materials, design and technology. Woodhead Publishing Series in Textiles.
      ], and was measured on the basis of ASTM D1777 [
      ASTM D1777-96
      Standard test method for thickness of textile materials.
      ]. Air permeability was measured using KES-F8 API (Kato Tech Co., Ltd, Kyoto, Japan), which enables the measurement of ventilation resistance, in which values can be obtained with minute amounts of ventilation. Measurement conditions were similar to the ventilation of the clothing worn, in which lower values indicate higher breathability and permeability [
      ].
      OWTC was defined as the difference in the cumulative moisture content between the two surfaces of a fabric in the unit testing time period, and was tested using the moisture management tester (MMT) to evaluate the textile moisture management properties [
      • Hu J.
      • Li Y.
      • Yeung K.W.
      • Wong A.S.
      • Xu W.
      Moisture management tester: a method to characterize fabric liquid moisture management properties.
      ]. The values were graded as follows: Grade 1: < 50, poor; Grade 2: 50–100, fair; Grade 3: 101–200, good; Grade 4: 201–400, very good; and Grade 5: > 400, excellent [
      • Yao B.G.
      • Li Y.
      • Hu J.Y.
      • Kwok Y.L.
      • Yeung K.W.
      An improved test method for characterizing the dynamic liquid moisture transfer in porous polymeric materials.
      ].
      OMMC shows the overall ability of a fabric to manage the transport of liquid moisture, and involves the moisture absorption rate of the bottom side, one-way liquid transport ability and moisture drying speed of the bottom side (represented by the maximum spreading speed). OMMC was also tested using MMT [
      • Hu J.
      • Li Y.
      • Yeung K.W.
      • Wong A.S.
      • Xu W.
      Moisture management tester: a method to characterize fabric liquid moisture management properties.
      ]. High values indicate high overall moisture management ability of a fabric. The value grading system was adapted from Yao [
      • Yao B.G.
      • Li Y.
      • Hu J.Y.
      • Kwok Y.L.
      • Yeung K.W.
      An improved test method for characterizing the dynamic liquid moisture transfer in porous polymeric materials.
      ]: Grade 1: 0–0.2, poor; Grade 2: >0.2–0.4, fair; Grade 3: >0.4–0.6, good; Grade 4: >0.6–0.8, very good; and Grade 5: >0.8, excellent [
      • Yao B.G.
      • Li Y.
      • Hu J.Y.
      • Kwok Y.L.
      • Yeung K.W.
      An improved test method for characterizing the dynamic liquid moisture transfer in porous polymeric materials.
      ]. BFE was defined as the percentage of particles filtered by the respiratory protection material. High numbers in this test indicate superior barrier efficiency [
      • Mueller W.
      • Horwell C.J.
      • Apsley A.
      • Steinie S.
      • McPherson S.
      • Cherrie J.W.
      • et al.
      The effectiveness of respiratory protection worn by communities to protect from volcanic ash inhalation. Part I: Filtration efficiency tests.
      ].

      Statistical analyses

      Descriptive statistics were used to compute the sociodemographic characteristics of the participants and the physical properties of the 3M and nanofibre FFRs. Fit factors of ≥100 and <100 indicate pass and fail results, respectively, in the PortaCount Plus Fit test. Chi-squared analysis was conducted to identify the association between demographic characteristics and fit factor (99, fail; ≥100, pass) after the procedures. Paired t-test was used to compare the fit factor of the best-fitting 3M FFR and nanofibre FFR before and after the nursing procedures. Wilcoxon signed ranks test was conducted to compare the usability of FFRs tested.

      Results

      In total, 104 undergraduate nursing students (21 males and 83 females) participated in this study. The best-fitting 3M FFRs (in sequence) were 1870+ (N=60), 1860S (N=40) and 1860 (N=4) (Table I). The average fit factor of both types of FFR (i.e. 3M model vs nanofibre) decreased significantly after completion of the nursing procedures (3M model: 185.08 vs 135.52; nanofibre mask: 188.44 vs 149.13). That is, the 3M model resulted in a consistent lower fit factor during the different body movements than the nanofibre model. When the cut-off fit factor was used as an indicator (i.e. 0–99, fail; ≥100, pass), approximately one-third of the participants (N=35, 33.7%) failed to obtain an overall fit factor ≥100 when using the best-fitting 3M FFR. In contrast, only 21.2% (N=21) of the participants failed after the procedures when wearing the nanofibre FFR (χ2=0.66, P=0.417) (Table II). No association was found between the specific variables (sex, year of study, age, clinical experience and body mass index) and fit factor (pass/fail) following the procedures (Table SI, see online supplementary material). The nanofibre FFR had consistent and significant higher usability than the 3M FFRs for all eight parameters (i.e. facial heat, breathability, facial pressure, speech intelligibility, itchiness, difficulty of maintaining the mask in place, comfort on ear lobe and overall comfort level) (t=5.28, P<0.001) (Table III). For physical properties, 10 FFRs of each model were tested, and the average of the values were taken. The nanofibre FFR was lighter and thinner than the three 3M FFRs (i.e. 1860, 1860S, 1870 Plus). Air permeability of the nanofibre FFR was lower than that of the N95 flat-fold model (1.050 kPa·s/m vs.1.2716 kPa·s/m) but slightly higher than the cup-shaped model. The OWTC and OMMC values of all FFRs were <50 and 0–0.2, respectively, indicating Grade 1 (poor). The bacterial filtration efficiency of the nanofibre FFR was slightly higher than that of the 3M models (99.9% vs 99.0%). Table IV shows the details of the physical properties of FFRs.
      Table IBaseline background and demographic characteristics of the study sample (N=104)
      VariablesValues
      Sex
       Male21 (20.2%)
       Female83 (79.8%)
      Year of study
       116 (15.4%)
       237 (35.6%)
       327 (26.0%)
       422 (21.2%)
       52 (1.9%)
      Best-fitting N95 3M FFR
       1860S40 (38.5%)
       18604 (3.8%)
       1870+60 (57.7%)
      Age, years22.08±2.56
      Clinical experiences, weeks11.65±15.48
      Body mass index (kg/m2)21.05±2.74
      Room temperature, °C22.91±1.40
      Room relative humidity,%57.63±10.18
      FFR, filtering facepiece respirator.
      Values are N, N (%) or mean±standard deviation.
      Table IIFit factors determined by the quantitative fit test between the best-fitting 3M filtering facepiece respirator (FFR) and nanofibre FFR before and after nursing procedures
      Body movementsFit factor before proceduresFit factor after procedures
      Best-fitting 3M FFRNanofibre FFRP-valueBest-fitting 3M FFRNanofibre FFRP-value
      Normal breathing198.09±7.62199.48±2.97>0.05151.27±69.56169.64±59.84>0.05
      Deep breathing197.27±11.95198.53±10.58>0.05152.07±68.20169.34±57.84<0.05
      Statistically significant at P<0.05, computed by paired Student's t-test.
      Head side to side192.06±25.07198.31±8.17<0.05
      Statistically significant at P<0.05, computed by paired Student's t-test.
      149.80±70.62161.97±63.84>0.05
      Head up and down186.98±30.89194.56±20.84<0.05
      Statistically significant at P<0.05, computed by paired Student's t-test.
      143.48±70.24165.06±60.67<0.05
      Statistically significant at P<0.05, computed by paired Student's t-test.
      Talking191.08±23.46195.33 (19.30)>0.05150.94±61.32164.39 (54.28)>0.05
      Bending over174.86±42.63179.16±47.46>0.05129.27±72.63144.78±67.78>0.05
      Normal breathing184.68±33.95191.12±30.29>0.05143.26±70.13159.73±66.48>0.05
      Overall fit factor185.08±24.52188.44±25.28>0.05135.52±68.33149.13±59.95>0.05
      N (%)N (%)
      Fit factor (1–99)

      Fit factor (≥100)
      35 (33.7%)

      69 (66.3%)
      21 (21.2%)

      82 (78.8%)
      χ2 = 0.66,

      P=0.417
      Values are mean±standard deviation unless otherwise indicated.
      a Statistically significant at P<0.05, computed by paired Student's t-test.
      Table IIIComparison of usability between the best-fitting 3M filtering facepiece respirator (FFR) and nanofibre FFR after nursing procedures (N=104)
      Best-fitting 3M FFRNanofibre FFRP-values
      Comparison of means using Wilcoxon signed ranks test.
      Facial heat3.76±0.874.12±0.73<0.001
      Statistically significant at P<0.001.
      Breathability3.63±0.994.32±0.61<0.001
      Statistically significant at P<0.001.
      Facial pressure3.54±1.104.08±0.82<0.001
      Statistically significant at P<0.001.
      Speech intelligibility3.81±0.924.20±0.78<0.01
      Statistically significant at P<0.01.
      Itchiness3.82±0.924.23±0.85<0.001
      Statistically significant at P<0.001.
      Difficulty of maintaining the mask in place3.74±0.944.05±0.70<0.01
      Statistically significant at P<0.01.
      Comfort on ear lobe3.85±1.024.23±0.71<0.01
      Statistically significant at P<0.01.
      Overall comfort3.71±0.894.21±0.53<0.001
      Statistically significant at P<0.001.
      Values are mean±standard deviation unless otherwise indicated.
      1, very unsatisfactory; 5, very satisfactory.
      a Comparison of means using Wilcoxon signed ranks test.
      b Statistically significant at P<0.01.
      c Statistically significant at P<0.001.
      Table IVPhysical properties of N95 3M and nanofibre filtering facepiece respirators (FFRs)
      Ten specimens were tested for each FFR.
      3M 1860/1860S3M 1870 PlusNanofibre
      NIOSH approvedN95N95N95
      ShapeCupFlat-foldFlat-fold
      SizeRegular or smallStandard (one size only)Standard (one size only)
      Weight (g/m2)

      Mean (SD)
      9.04356 ± 0.0001710.14386 ± 0.000294.8795±0.442
      Thickness (mm)

      Mean (SD)
      2.506±0.0631.846±0.0380.5184±0.025
      Air permeability [ventilation resistance R (kPa·s/m)]0.9280±0.00241.2716±0.06111.050±0.065
      Cumulative one-way transport capacity-195.085±53.250-309.692±97.127-696.261±19.759
      Overall moisture management capacity0.000±0.0000.044±0.0660.000±0.000
      Bacterial filtration efficiency99.0%>99.0%>99.9% (Nelson lab tested)
      Exhalation valveNoNoNo
      Tethering devicesBraided headbands, cushioning nose foamSoft inner materials and soft nose foam; sculpted top panel helps improve field of vision, and reduce eyewear fogging;

      chin tab for ease of positioning, donning and adjustment
      Soft inner materials and soft nose foam
      Other featuresThree-panel flat-fold design for convenient storage prior to useFlat-fold design for convenient storage prior to use
      FDA clearedYesYesNo
      NIOSH, National Institute for Occupational Safety and Health; FDA, Food and Drug Administration; SD, standard deviation.
      a Ten specimens were tested for each FFR.

      Discussion

      This study showed that the nanofibre FFR has a better facial seal and higher usability than the 3M FFRs. Although the fit factors of the nanofibre FFR were higher than the best-fitting 3M FFR before and after the nursing procedures, the average fit factor of both FFRs decreased significantly after completion of the nursing procedures, as measured using QNFT at different body postures. This result is consistent with those from a previous study, which found that adequately sealed N95 FFRs may not provide consistent protection for the wearer whilst performing nursing procedures and that body movements may increase the risk of face seal leakage [
      • Suen L.K.P.
      • Yang L.
      • Ho S.S.K.
      • Fung K.H.K.
      • Boost M.V.
      • Wu C.S.T.
      • et al.
      Reliability of N95 respirators for respiratory protection before, during and after nursing procedures.
      ]. Accordingly, the prototype should be further enhanced for an improved respirator fit to guarantee the respiratory protection of users. In particular, the development of a superior fit FFR should be prioritized to eliminate or at least minimize face seal leakage during usage for procedures requiring body movements.
      Meanwhile, discomfort was the most common reason given by HCWs for improper use of respirators [
      • Shaffer R.E.
      • Janssen L.L.
      Selecting models for a respiratory protection program: what can we learn from the scientific literature?.
      ]. Perceptions of increased body heat when wearing the N95 FFR are likely not caused by effects on core temperature but may be associated with warming of facial skin covered by the respirator and warming of inspired air [
      • DiLeo T.
      • Roberge R.J.
      • Kim J.H.
      Effect of wearing an N95 filtering facepiece respirator on superomedial orbital infrared indirect brain temperature measurements.
      ,
      • Roberge R.
      • Benson S.
      • Kim J.H.
      Thermal burden of N95 filtering facepiece respirators.
      ]. Poor communication and speech intelligibility have been shown to be concerns when wearing a respirator, given the potential for miscommunication that leads to critical treatment mistakes [
      • Gosch M.E.
      • Shaffer R.E.
      • Eagan A.E.
      • Roberge R.J.
      • Davey V.J.
      • Radonovich Jr., L.J.
      B95: a new respirator for health care personnel.
      ]. The nanofibre FFR tested in this study had consistent and significantly higher usability than the 3M FFRs for all eight parameters, thereby providing an alternate option for HCWs.
      Electrospinning technology has enabled NAMI to successfully combine meltblown and spunbond fibres with nanofibres with diameters ranging from a few nanometres to a few hundred nanometres. This result cannot be obtained using traditional fabrication techniques. The nanofibre FFR can trap small particles effectively using various mechanisms, such as Brownian diffusion, because these masks are characterized by a small fibre diameter and high specific surface area [
      • Qin X.H.
      • Wang S.Y.
      Filtration properties of electrospinning nanofibers.
      ]. Therefore, the nanofibre FFR was thinner and more breathable than traditional N95 FFRs (as indicated in the usability results), thereby enhancing general comfort for users. This feature encourages users to keep nanofibre FFRs on their faces, thereby possibly leading to improved user compliance.
      In this study, the best-fitting 3M FFRs for the participants (in sequence) were 1870+, 1860S and 1860. Model 1870+ and the nanofibre FFR are flat-fold in shape, whereas the 1860 series are cup-shaped. An experimental study using sterophotogrammetry technology on 20 subjects found that more individuals passed fit testing when wearing flat-fold respirators than when wearing cup-shaped respirators. It was demonstrated that flat-fold N95 respirators offer the possibility of enhanced facial comfort without compromising protection [
      • Niezgoda G.
      • Kim J.H.
      • Roberge R.J.
      • Benson S.M.
      Flat fold and cup-shaped N95 filtering facepiece respirator face seal area and pressure determinations: a stereophotogrammetry study.
      ].
      Studies have shown that FFRs with additional weight could impose an ergonomic burden that translates into cardiac stress [
      • Johnson A.T.
      Do respirators stress the cardiovascular system?.
      ] and reduce work performance time [
      • Johnson A.T.
      Effects of PAPR helmet weight on voluntary performance time at 80–85 % of maximal aerobic capacity.
      ]. The nanofibre FFR tested in this study was lighter than the 3M models, thereby possibly contributing to minimal cardiac stress burden and longer work performance time for the nanofibre mask. A study on the in-vivo protective performance of surgical marks and N95 respirators demonstrated that nano-masks have stronger water repellency and antibacterial activities than normal N95 and surgical masks. The coating of nano-functional particles for enhancement of water repellency could account for a slightly higher bacterial filtration efficiency in the nanofibre FFR than in 3M models (99.9% vs 99.0%).
      The nanofibre FFR has significantly higher air permeability (lower air resistance) than the N95 flat-fold model, indicating that the nanofibre FFR is more breathable. The three FFR models are made of non-woven fabrics, which provide specific functions such as filtration and can be used as a bacterial barrier. However, these fabrics are also liquid repellent. Thus, the three FFR models have poor cumulative one-way transport capacity and overall moisture management capacity.
      The Project Better Respiratory Equipment using Advanced Technologies for Healthcare Employees (BREATHE) Working Group, which comprises numerous federal stakeholders, was formed in the USA in 2008 to discuss strategies for improving respirator compliance, including the need for comfortable respirators. The Working Group developed 28 desirable performance characteristics for a new class of respirators (B95) which would substantially address the unique needs of HCWs [
      • Gosch M.E.
      • Shaffer R.E.
      • Eagan A.E.
      • Roberge R.J.
      • Davey V.J.
      • Radonovich Jr., L.J.
      B95: a new respirator for health care personnel.
      ]. Although the nanofibre FFR tested in this study could not fulfil all the B95 recommendations, this project attempted to address those wearer-subjective factors on respirator usability that may enhance compliance, including improvement of breathability, causing minimal discomfort from pressure on the face, inducing minimal facial heat and causing minimal facial irritation and allergenicity. Considerable effort should be exerted to improve the prototype design to attain the other B95 recommendations in the near future.

      Limitations and recommendations

      Given the limited scope of this study, the prolonged tolerability, cost-effectiveness and shelf-life durability of FFRs were not examined. Moreover, the thermophysiologic impact (e.g. cardio-respiratory parameters and thermal stress) of N95 FFRs on HCWs under prolonged use of respirators should be determined in future studies to simulate clinical situations.
      In conclusion, the findings of this study demonstrated that the nanofibre FFR had a higher pass rate on fit testing and significantly better usability than the 3M FFRs. The nanofibre FFR was also lighter, thinner and had slightly higher bacterial filtration efficiency than the 3M FFRs. However, none of the FFRs could provide consistent protection for the wearer, as detected by face seal leakage after performing nursing procedures. Consequently, further effort should be exerted to improve the prototype design with superior fitness and high usability, thereby increasing compliance and ensuring the respiratory protection of users.

      Acknowledgements

      The authors wish to thank the Squina International Centre for Infection Control, School of Nursing, The Hong Kong Polytechnic University for providing the venue and devices for data collection; Dr Lin Yang and Mr Keith Fung for their advice; the participants who offered their support to this study; Dr Ho-Wang Tong and Dr Connie Kwok, from the Nano and Advanced Materials Research Institute, for their expert advice on nanofibre technology; and Ms Sarinda Kwok, from the Profit Royal Pharmaceutical Limited, for supplying the nanofibre masks tested in this study.

      Conflict of interest statement

      None declared. To prevent any potential conflict of interest, the Profit Royal Pharmaceutical Limited, which supplied the nanofibre masks tested in this study, did not participate in the data analyses.

      Funding source

      This project was supported by a grant from the Departmental General Research Fund (1-ZVFF), School of Nursing, Hong Kong Polytechnic University , Hong Kong Special Administrative Region of the People’s Republic of China.

      Appendix A. Supplementary data

      The following is the Supplementary data to this article:

      References

        • National Institute for Occupational Safety and Health
        Workplace solutions: preparedness through daily practice: the myths of respiratory protection in healthcare.
        (Publication No. 2016-109) U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH), Cincinnati, OH2015
        • National Institute for Occupational Safety and Health
        42 CFR Part 84 Respiratory protective devices.
        U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH), Cincinnati, OH1997 (Available at:)
        • Lam S.C.
        • Lee J.K.
        • Yau S.Y.
        • Charm C.Y.
        Sensitivity and specificity of the user-seal-check in determining the fit of N95 respirators.
        J Hosp Infect. 2011; 7: 252-256
        • Lee M.C.
        • Takaya S.
        • Long R.
        • Joffe A.M.
        Respirator-fit testing: does it ensure the protection of healthcare workers against respirable particles carrying pathogens?.
        Infect Control Hosp Epidemiol. 2008; 29: 1149-1156
        • Clayton M.
        • Vaughan N.
        Fit for purpose: the role of fit testing in respiratory protection.
        Ann Occup Hyg. 2005; 49: 545-548
        • Roberge R.J.
        • Monaghan W.D.
        • Palmiero A.J.
        • Shaffer R.
        • Bergman M.S.
        Infrared imaging for leak detection of N95 filtering facepiece respirators: a pilot study.
        Am J Ind Med. 2011; 54: 628-636
        • Li J.
        • Gao F.
        • Liu Q.
        • Zhang Z.
        Needleless electro-spun nanofibers used for filtration of small particles.
        Express Polym Lett. 2013; 7: 683-689
        • Baig A.S.
        • Knapp C.
        • Eagan A.E.
        • Radonovich Jr., L.J.
        Health care workers’ views about respirator use and features that should be included in the next generation of respirators.
        Am J Infect Control. 2010; 38: 18-25
        • Gralton J.
        • McLaws M.L.
        Protecting healthcare workers from pandemic influenza: N95 or surgical masks?.
        Crit Care Med. 2010; 38: 657-667
        • Roberge R.J.
        • Coca A.
        • Williams W.J.
        • Palmiero A.J.
        • Powell J.B.
        Surgical mask placement over N95 filtering facepiece respirators: physiological effects on healthcare workers.
        Respirology. 2010; 15: 516-521
        • National Institute for Occupational Safety and Health Science
        N95 respirators and surgical masks.
        U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH), Cincinnati, OH2009 (Available at:)
        • Gosch M.E.
        • Shaffer R.E.
        • Eagan A.E.
        • Roberge R.J.
        • Davey V.J.
        • Radonovich Jr., L.J.
        B95: a new respirator for health care personnel.
        Am J Infect Control. 2013; 41: 1224-1230
        • Rebmann T.
        • Carrico R.
        • Wang J.
        Physiologic and other effects and compliance with long-term respirator use among medical intensive care unit nurses.
        Am J Infect Control. 2013; 41: 1218-1223
        • Shenal B.V.
        • Radonovich Jr., L.J.
        • Cheng J.
        • Hodgson M.
        • Bender B.S.
        Discomfort and exertion associated with prolonged wear of respiratory protection in a health care setting.
        J Occup Environ Hyg. 2012; 9: 59-64
        • Suen L.K.P.
        • Yang L.
        • Ho S.S.K.
        • Fung K.H.K.
        • Boost M.V.
        • Wu C.S.T.
        • et al.
        Reliability of N95 respirators for respiratory protection before, during and after nursing procedures.
        Am J Infect Control. 2017; 45: 974-978
        • Hannum D.
        • Cycan K.
        • Jones L.
        • Stewart M.
        • Morris S.
        • Markowitz S.M.
        • et al.
        The effect of respirator training on the ability of healthcare workers to pass a qualitative fit test.
        Infect Control Hosp Epidemiol. 1996; 17: 636-640
        • Lam S.C.
        • Lui A.K.
        • Lee L.Y.
        • Lee J.K.
        • Wong K.F.
        • Lee C.N.
        Evaluation of the user seal check on gross leakage detection of 3 different designs of N95 filtering facepiece respirators.
        Am J Infect Control. 2016; 44: 579-586
        • Lam S.C.
        • Lee J.K.
        • Lee L.Y.
        • Wong K.F.
        • Lee C.N.
        Respiratory protection by respirators: the predictive value of user seal check for the fit determination in healthcare settings.
        Infect Control Hosp Epidemiol. 2011; 32: 402-403
        • Meyer J.P.
        • Hery M.
        • Herrault J.
        • Hubert G.
        • Francois D.
        • Hecht G.
        • et al.
        Field study of subjective assessment of negative pressure half-masks: influence of the work conditions on comfort and efficiency.
        Appl Ergon. 1997; 28: 331-338
        • ASTM D3776 / D3776M-09a
        Standard test methods for mass per unit area (weight) of fabric.
        ASTM International, West Conshohocken, PA2017 (Available at:) ([last accessed June 2019])
        • Rose S.
        Textiles and fashion: materials, design and technology. Woodhead Publishing Series in Textiles.
        Elsevier Science, Amsterdam2015: 307-335
        • ASTM D1777-96
        Standard test method for thickness of textile materials.
        ASTM International, West Conshohocken, PA2015 (Available at:) ([last accessed June 2019])
      1. KES-F8 e Air Permeability Tester. Kato Tech Co., Ltd., Japan2016 (Available at:) ([last accessed June 2019])
        • Hu J.
        • Li Y.
        • Yeung K.W.
        • Wong A.S.
        • Xu W.
        Moisture management tester: a method to characterize fabric liquid moisture management properties.
        Text Res J. 2005; 75: 57-62
        • Yao B.G.
        • Li Y.
        • Hu J.Y.
        • Kwok Y.L.
        • Yeung K.W.
        An improved test method for characterizing the dynamic liquid moisture transfer in porous polymeric materials.
        Polym Test. 2006; 25: 677-689
        • Mueller W.
        • Horwell C.J.
        • Apsley A.
        • Steinie S.
        • McPherson S.
        • Cherrie J.W.
        • et al.
        The effectiveness of respiratory protection worn by communities to protect from volcanic ash inhalation. Part I: Filtration efficiency tests.
        Int J Hyg Environ Health. 2018; 221: 967-976
        • Shaffer R.E.
        • Janssen L.L.
        Selecting models for a respiratory protection program: what can we learn from the scientific literature?.
        Am J Infect Control. 2015; 43: 127-132
        • DiLeo T.
        • Roberge R.J.
        • Kim J.H.
        Effect of wearing an N95 filtering facepiece respirator on superomedial orbital infrared indirect brain temperature measurements.
        J Clin Monit Comput. 2016; 31: 67-73
        • Roberge R.
        • Benson S.
        • Kim J.H.
        Thermal burden of N95 filtering facepiece respirators.
        Ann Occup Hyg. 2012; 56: 808-814
        • Qin X.H.
        • Wang S.Y.
        Filtration properties of electrospinning nanofibers.
        J Appl Polym Sci. 2006; 102: 1285-1290
        • Niezgoda G.
        • Kim J.H.
        • Roberge R.J.
        • Benson S.M.
        Flat fold and cup-shaped N95 filtering facepiece respirator face seal area and pressure determinations: a stereophotogrammetry study.
        J Occup Environ Hyg. 2013; 10: 419-424
        • Johnson A.T.
        Do respirators stress the cardiovascular system?.
        J Int Soc Respir Prot. 2003; 20: 26-36
        • Johnson A.T.
        Effects of PAPR helmet weight on voluntary performance time at 80–85 % of maximal aerobic capacity.
        J Int Soc Respir Prot. 2006; 23: 111-118