Advertisement

Optimizing twin sampling tube stabilization improves quantitative fit test results for flat-fold duckbill filtering facepiece respirators

Open AccessPublished:October 06, 2022DOI:https://doi.org/10.1016/j.ajic.2022.09.026

      Highlights

      • Quantitative fit testing (QNFT) requires a sampling tube attachment.
      • Robust sampling tube stabilization is needed for QNFT of flat-fold type respirators.
      • Lanyard technique had significantly lower QNFT pass rates than hand-hold technique.
      • Fit testers should pay close attention to the sampling tube during QNFT.

      Introduction

      When performing quantitative fit testing (QNFT) on filtering facepiece respirators using an ambient aerosol technique, a twin sampling tube is connected between the condensation nuclei count machine and the probed respirator. To achieve high quality and repeatable QNFT results, robust sampling tube stabilization is required.

      Methods

      In this prospective randomized crossover study, conducted in December 2021 to February 2022, we compared the commonly used hand-hold technique with the manufacturer-recommended lanyard technique in stabilizing the sampling tube during QNFT on a Halyard N95 respirator. Outcomes included QNFT pass rates, overall and individual fit factors, and concordance between the two techniques.

      Results

      A total of 228 out of 316 participants (72.2%) passed the QNFT with the hand-hold technique, compared to the lanyard technique (166/316, 52%, P < .001). The most significant drop in the fit factors with the lanyard technique occurred during head movement side-to-side and up-and-down. The concordance between the 2 techniques was fair (Kappa coefficient = 0.39).

      Conclusion

      Our study demonstrates that the method of sampling tube stabilization during QNFT has a significant impact on fit test pass rates, with a potential for false negative fit tests due to inadequate tube stabilization. Further research is required to examine the generalizability of these results to other respirators and fit testing apparatuses.

      Key Words

      During viral respiratory pandemics in the twenty-first century, most health care workers have used lightweight disposable filtering facepiece respirators (FFRs) and should have undergone quantitative fit testing (QNFT) as a part of a dedicated respiratory protection program.

      International Standard ISO 16975-3:2017(E) 3.3 Respiratory protective devices — Selection, use and maintenance — Part 3: Fit-testing procedures. Available at: https://ohdusa.com/sites/default/files/ISO_16975-3_1-19-2018.pdf. (Accessed May 2022)

      Victorian Department of Health and Human Services. COVID-19 Respiratory Protection Program guidelines. Available at: https://www.health.vic.gov.au/victorian-respiratory-protection-program-COVID-19-pdf. (Accessed May 2022)

      Australian NSW Government. Clinical Excellence Commission. Respiratory Protection Program. Available at: https://www.cec.health.nsw.gov.au/keep-patients-safe/COVID-19/respiratory-protection-program. (Accessed May 2022)

      The Occupational Health and Safety Administration (OSHA) has set out a QNFT protocol for FFRs, called the ambient aerosol condensation nuclei counter (AACNC) technique.

      United States Department of Labor. Occupational Safety and Health Administration. Personal Protective Equipment. 1910.134 App A. Fit testing procedures (mandatory). Part 1. OSHA-accepted fit test protocols. Available at: https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134AppA. (Accessed May 2022)

      It involves the use of a twin sampling tube, which connects between the CNC machine and a probed respirator.

      United States Department of Labor. Occupational Safety and Health Administration. Personal Protective Equipment. 1910.134 App A. Fit testing procedures (mandatory). Part 1. OSHA-accepted fit test protocols. Available at: https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134AppA. (Accessed May 2022)

      The twin sampling tube allows measurement of the fit factor (respirator fit) by comparing the concentration of the particles outside the mask to inside the mask.

      United States Department of Labor. Occupational Safety and Health Administration. Personal Protective Equipment. 1910.134 App A. Fit testing procedures (mandatory). Part 1. OSHA-accepted fit test protocols. Available at: https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134AppA. (Accessed May 2022)

      The modified AACNC for FFRs technique requires the test subject to perform four specific exercises: (1) Bending over at the hips and returning to upright repeatedly while taking 2 breaths during the bend over; (2) Reading a standardized text aloud; (3) Moving the head side-to-side; and (4) Moving the head up-and-down.

      United States Department of Labor. Occupational Safety and Health Administration. Personal Protective Equipment. 1910.134 App A. Fit testing procedures (mandatory). Part 1. OSHA-accepted fit test protocols. Available at: https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134AppA. (Accessed May 2022)

      Unfortunately, the dynamic nature of the exercises may result in the twin sampling tube pulling on the probed respirator and breaking the face seal. This can potentially result in an erroneous failed QNFT or false negative test result. To achieve high quality and repeatable quantitative fit test results when assessing FFRs, robust sampling tube stabilization needs to be assured.
      TSI instruments, which manufacture the PortaCount AACNC instrument (PortaCount Pro. 8048; TSI Incorporated, St Paul, MN, USA), recommend using a dedicated lanyard (neck strap) technique for twin sampling tube stabilization when assessing FFRs.

      TSI. Portcount Respirator Fit Tester 8048. Available at: https://tsi.com/products/respirator-fit-testers/portacount-respirator-fit-tester-8048/. (Accessed May 2022)

      Single-use lanyards add to the cost of the fit testing, whereas re-use of a material lanyard among participants raises the issue of infection risk.

      Australian Government. National Health and Medical Research Council. Australian Guidelines for the Prevention and Control of Infection in Health Care. Published 2019. 2020. Available at: https://www.nhmrc.gov.au/sites/default/files/documents/infection-control-guidelines-feb2020.pdf. (Accessed May 2022)

      • Murphy CM
      • Ruscio FD
      • Lynskey M
      • et al.
      Identification badge lanyards as infection control risk: a cross-sectional observation study with epidemiological analysis.
      • Kotsanas D
      • Scott C
      • Gillespie EE
      • Korman TM
      • Stuart RL.
      What's hanging around your neck? Pathogenic bacteria on identity badges and lanyards.
      The requisite length of free tubing to allow unencumbered movement during the OSHA modified AACNC protocol also means that extra tube length is dependent when using the lanyard technique. This may result in tube momentum during dynamic exercises and potentially disrupt the seal of lightweight disposable FFRs.
      Consequently, a commonly used alternative to the lanyard technique has evolved where the test subject stabilizes the twin sampling tube in one hand whilst performing the OSHA recommended exercises.

      NSW Government. Clinical Excellence Commission. Education, training, and videos. Fit testing. Available at: https://www.cec.health.nsw.gov.au/keep-patients-safe/COVID-19/education-training-videos. (Accessed May 2022)

      This requires instructing the participant to hold the sampling tube like a microphone, to ensure that the hand moves in synchronization with the respirator when performing all exercises.
      The aim of this study was to compare hand-hold and lanyard sampling tube stabilization techniques to examine whether there was any difference in quantitative fit factors and fit test pass rates, and to deduce the concordance between the 2 techniques.

      Methods

      This prospective randomized crossover study was approved by the local ethics committee, Melbourne Health Human Research Ethics Committee (QA2020174). It was conducted through the Respiratory Protection Program at the Royal Melbourne Hospital.
      A preliminary investigation was undertaken to determine the optimal attachment point of the lanyard clip to the sampling tube. We performed a video analysis, which showed that head movements, including side-to-side and up-and-down movements, required additional length of the twin sampling tube to prevent pulling on the FFR. An attachment point of 50 cm from the sampling probe of the respirator was found to be the minimum length required (Fig 1A). If any pull was detected during the pre-QNFT assessment, the length was adjusted by increasing 2 cm increments until no pull was detected. Whereas for the hand-hold technique, the optimal position was to hold the twin sampling tube at 30cm from the respirator probe indicated by black mark, while keeping the hand 15 cm below the respirator by curling the sampling tube slightly to make a smooth c-shaped curve (Fig 1B). This allows almost zero vertical weight of the sampling tube on the respirator (Appendix A). Participants were required to keep the hand at approximately 15cm below the respirator throughout all the exercises, holding the sample tube like a microphone.
      Fig 1
      Fig 1Pictures demonstrating tube stabilization techniques: 1A lanyard 1B hand-hold.
      The respirator used in this study was the medium-sized flat-fold duckbill type Halyard Fluidshield N95 respirator (Halyard, Alpharetta, Georgia, USA). This FFR type was chosen because out of all the commonly available N95/P2 FFRs in our institution, it has the lightest weight while having quantitative fit test pass rates above 65% (Appendix B).
      All the participants in this study completed a basic demographic survey via REDCap 10.5.2 (Vanderbilt University, Nashville, Tennessee, USA), as part of the respiratory protection program requirement. Figure 2 provides details of the data collection process. They underwent QNFT on the Halyard N95 respirator using both the hand-hold and the lanyard sampling tube stabilization techniques. The order of the stabilization technique to be employed first was randomly allocated, according to the computer-generated randomization method,

      Research randomizer. Available at: https://www.randomizer.org. (Accessed May 2022)

      in blocks of ten, and stratified into male and female group. All male participants were clean shaven.
      Fig 2
      Fig 2Data collection process. RPP, respiratory protection program; FFRs, filtering facepiece respirators; QNFT, quantitative fit testing.
      The QNFT was performed by fit testers, who were all qualified by a certified training program, using a Portacount machine (PortaCount Respiratory Fit Tester 8048, TSI Incorporated, St Paul, Minnesota, USA). The test was carried out according to the OSHA modified AACNC for FFRs protocol with four conventional exercises as stated above.

      United States Department of Labor. Occupational Safety and Health Administration. Personal Protective Equipment. 1910.134 App A. Fit testing procedures (mandatory). Part 1. OSHA-accepted fit test protocols. Available at: https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134AppA. (Accessed May 2022)

      The range of head movement was consistent for all participants, that is, 60 degrees for up-and-down and 180 degrees for side-to-side head movement. Each movement transition was performed at a consistent time of 2-3 seconds. All exercises were performed standing up and autonomously without prompting. Real-time measurements were not allowed. Any breach of the protocol was addressed by recommencing the test. Standardized remedial guidance was provided if the participant failed their initial fit test. The QNFT results were recorded on the Portacount machine and transferred to the respiratory protection program REDCap database.
      The primary outcome was to compare the quantitative fit test pass rates between the two techniques (defined as a harmonic mean fit factor of ≥100, as recommended in the Australian Standards for half-face P2 respirators including FFRs). Secondary outcomes were to compare the overall fit factors, individual fit factors, and the concordance between 2 techniques.

      Statistical analysis

      The QNFT pass rate of the Halyard N95 respirator was 77% based on previous published literature.
      • Williams DL
      • Kave B
      • Lee K
      • et al.
      A randomized crossover study to compare the user seal check and quantitative fit test between two types of duckbill N95 particulate respirator masks: the Halyard Fluidshield N95 and the BSN Medical ProShield N-95 particulate respirator masks.
      To demonstrate a clinically important difference of 10%, at least 335 participants per group would be required for a power of 0.8. Therefore, we aimed to recruit a total of 350 participants.
      Descriptive statistics such as means, medians and percentages were used to present the demographic data, quantitative fit factors, and fit test pass rates. McNemar test was used to compare the fit test pass rates and Wilcoxon sign-rank test to compare the fit factors between the two sampling tube stabilization techniques. P-value of < .05 was considered statistically significant. Statistical analysis was performed using Stata 13.0 (Statacorp, College Station, Texas, USA).

      Results

      This study was conducted from December 15, 2021 till February 9, 2022. A total of 350 health care workers who participated in the respiratory protection program were recruited in this study. Thirty-four records were removed due to administrative errors or missing data (Fig 3). A total of 316 datasets were analyzed, with 156 participants randomized to the hand-hold technique first and 160 to the lanyard technique first. Table 1 shows the participants’ demographic data. Most of the participants were female with an average BMI of 26kgm−2.
      Table 1Participants’ baseline characteristics. Values are expressed as mean ± S.D., number (percentage)
      Baseline characteristicsN = 316
      Age, y36.7 ± 12.5
      Sex, M:F:Other:Missing81:230:1:4
      BMI, kgm−226.0 ± 5.5
      Randomised first sampling tube stabilisation technique
      Hand-hold technique156 (49.4%)
      Lanyard technique160 (50.6%)
      A total of 228 out of 316 participants (72.2%) passed the QNFT with the hand-hold sampling tube stabilization technique. This was significantly higher than the lanyard stabilization technique (166 of 316, 52%, P < .001). There was also a statistically significant reduction in the overall fit factor [167 (IQR, 89-201) vs 112 (IQR, 52-196), P < .001] and individual fit factors for the lanyard technique compared to the hand-hold technique (Table 2). The most significant drop in the fit factors occurred during exercise 3 and 4, which were moving the head side-to-side [183 (IQR, 80-201) vs 104 (IQR, 0-201), P < .001] and up-and-down [172 (IQR, 62-201) vs 91 (IQR, 0-201), P < .001] respectively. The concordance between the 2 techniques was fair, with a Kappa value of 0.39.
      Table 2Comparison of quantitative fit test results between hand-hold and lanyard sampling tube stabilization techniques. Values are expressed as number (percentage) and median [IQR (range)]
      Hand-hold techniqueLanyard techniqueP-value
      Pass fit test228 (72.2%)166 (52.5%)<0.001
      Statistically significant.
      Overall fit factor167 (89-201[1-201])112 (52-196[1-201])<0.001
      Statistically significant.
      Individual fit factor
      Bending over201(103-201[1-201])153 (56-201[1-201])<0.001
      Statistically significant.
      Talking201(130-201(0-201])189 (63-201[0-201])<0.001
      Statistically significant.
      Head side-to-side183 (80-201[0-201])104 (0-201[0-201])<0.001
      Statistically significant.
      Head up-and-down172 (62-201[0-201])91 (0-201[0-201])<0.001
      Statistically significant.
      low asterisk Statistically significant.

      Discussion

      Our findings demonstrated that for QNFT on flat-fold duckbill type FFRs, the hand-hold sampling tube stabilization technique provided superior fit testing results compared to stabilization with the TSI-recommended lanyard technique. We believe this to be the first such study in the literature to examine the method of sampling tube stabilization in QNFT, with implications for the testing protocols of respiratory protection programs in jurisdictions where duckbill FFRs are commonly used.
      The aim of QNFT in the health care setting is to determine whether a given FFR provides adequate respiratory protection to a health care worker in the workplace through simulating common physical activities as prescribed by the OSHA protocol.

      United States Department of Labor. Occupational Safety and Health Administration. Personal Protective Equipment. 1910.134 App A. Fit testing procedures (mandatory). Part 1. OSHA-accepted fit test protocols. Available at: https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134AppA. (Accessed May 2022)

      United States Department of Labor. Occupational Safety and Health Administration. Assigned protection factor for the revised respiratory protection standard. Available at: https://www.osha.gov/sites/default/files/publications/3352-APF-respirators.pdf. (Accessed May 2022)

      However, the fit testing procedure is only a simulation of workplace activity, and one of the main differences between QNFT and true workplace activity is the presence of a sampling tube attached to the FFR. Importantly, our study demonstrates that the method of stabilization for the tube can have significant effects on the outcome of fit testing.
      The Halyard N95 FFR used in this study is lighter in weight (7.88 g) than other commonly available disposable respirator models, such as the 3-panel flat fold 3M Aura (8.55 g), and Trident (9.58 g) and also the semi-rigid cone 3M 1860 (11.29 g). As a consequence, this FFR may be more prone to shear forces generated by the sampling tube, and it is for this reason that we undertook this study on this particular FFR model. The most significant decrease in fit factors between the 2 techniques was observed in the exercises with neck and head movement, being the “head side-to-side” and “head up-and-down” exercises. This supports the hypothesis when the lanyard is used, shear forces from the tube are disrupting the shape and seal of the mask on the face. Further research is necessary to determine if this effect is generalizable to other, more sturdy respirator models.
      Our study demonstrates that suboptimal tube stabilization, as seen with the lanyard technique in our cohort, can potentially lead to false negative fit tests. False negative QNFT results can conceivably impact staff confidence in their PPE and can also impact hospital procurement decisions.
      • Regli A
      • Thalayasingam P
      • Bell E
      • Sommerfield A
      • von Ungern-Sternberg BS.
      More than half of front-line health care workers unknowingly used an N95/P2 mask without adequate airborne protection: An audit in a tertiary institution.
      Furthermore, false negatives also unnecessarily limit the FFR choices available to health care workers, which is an undesired consequence during a pandemic that has seen supply constraints on personal protective equipment.
      • Wild CEK
      • Wells H
      • Coetzee N
      • et al.
      Mixed-methods survey of health care workers’ experiences of personal protective equipment during the COVID-19 pandemic in Aotearoa/New Zealand.
      We acknowledge that our study has several limitations. Firstly, only one style of FFR, the flat-fold duckbill was examined and therefore the results may not be applicable to other models of FFR or elastomeric face masks due to differences in mask weight, design, and strap tension. Secondly, only one fit testing apparatus, the Portacount 8,048 was utilized, however, given that all portable AACNC quantitative fit test apparatuses use similar twin tube assemblies, the results should be applicable to other Centers for Disease Control (CDC) accredited devices. Thirdly, our study sample of 300 participants was small but nevertheless provided a statistically and clinically significant outcome.
      Lastly, we cannot completely exclude the converse hypothesis that the hand-hold technique provides greater stability to breathing zone of the respirator and in fact enhances the facial seal of the FFR during QNFT. Nevertheless, we deem this to be unlikely due to the fact that our protocol standardized the position of the hands on the tube to create a curvature, imparting minimal forces on the respirator. Furthermore, due to the collapsible nature of this respirator, it is counterintuitive to expect the tube to be able to generate sufficient force to improve facial seal.

      Conclusion

      In conclusion, our study demonstrates that the method of sampling tube stabilization during QNFT has a significant impact on fit test pass rates, with a potential for false negative fit tests as a consequence of inadequate tube stabilization. We encourage further research to examine the generalizability of these results on other respirators and portable condensed nuclei count fit testing apparatuses.

      Data sharing statement

      All the individual de-identified data that support the findings of this study are available upon request from the corresponding author. Study protocol and statistical analysis are also available. Information will be available immediately following publication until five years after publication.

      Authorship statement

      Professor Daryl L Williams: obtained ethics approval, conceptualization, data curation, methodology, project administration, resources, validation, writing – original draft, review and editing. Dr Ben Kave: conceptualization, methodology, resources, writing – original draft, review and editing. Ms Fiona Begg: conceptualization, methodology, project administration, resources, writing – review and editing. Mr Charles Bodas: conceptualization, methodology, project administration, resources, writing – review and editing. Ms Megan Roberts: methodology, project administration, resources, data curation, writing – review and editing. Dr Irene Ng: obtained ethics approval, conceptualization, data curation, statistical analysis, writing - original draft, review and editing.

      Acknowledgments

      We would like to thank all the staff from the Royal Melbourne Hospital Respiratory Protection Program for their assistance in completing this project. We also acknowledge TSI incorporated for providing the lanyards for this study.

      Appendix. SUPPLEMENTARY MATERIALS

      References

      1. International Standard ISO 16975-3:2017(E) 3.3 Respiratory protective devices — Selection, use and maintenance — Part 3: Fit-testing procedures. Available at: https://ohdusa.com/sites/default/files/ISO_16975-3_1-19-2018.pdf. (Accessed May 2022)

      2. Victorian Department of Health and Human Services. COVID-19 Respiratory Protection Program guidelines. Available at: https://www.health.vic.gov.au/victorian-respiratory-protection-program-COVID-19-pdf. (Accessed May 2022)

      3. Australian NSW Government. Clinical Excellence Commission. Respiratory Protection Program. Available at: https://www.cec.health.nsw.gov.au/keep-patients-safe/COVID-19/respiratory-protection-program. (Accessed May 2022)

      4. United States Department of Labor. Occupational Safety and Health Administration. Personal Protective Equipment. 1910.134 App A. Fit testing procedures (mandatory). Part 1. OSHA-accepted fit test protocols. Available at: https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134AppA. (Accessed May 2022)

      5. TSI. Portcount Respirator Fit Tester 8048. Available at: https://tsi.com/products/respirator-fit-testers/portacount-respirator-fit-tester-8048/. (Accessed May 2022)

      6. Australian Government. National Health and Medical Research Council. Australian Guidelines for the Prevention and Control of Infection in Health Care. Published 2019. 2020. Available at: https://www.nhmrc.gov.au/sites/default/files/documents/infection-control-guidelines-feb2020.pdf. (Accessed May 2022)

        • Murphy CM
        • Ruscio FD
        • Lynskey M
        • et al.
        Identification badge lanyards as infection control risk: a cross-sectional observation study with epidemiological analysis.
        J Hosp Infect. 2017; 96: 63-66
        • Kotsanas D
        • Scott C
        • Gillespie EE
        • Korman TM
        • Stuart RL.
        What's hanging around your neck? Pathogenic bacteria on identity badges and lanyards.
        Med J Aust. 2008; 188: 5-8
      7. NSW Government. Clinical Excellence Commission. Education, training, and videos. Fit testing. Available at: https://www.cec.health.nsw.gov.au/keep-patients-safe/COVID-19/education-training-videos. (Accessed May 2022)

      8. Research randomizer. Available at: https://www.randomizer.org. (Accessed May 2022)

        • Williams DL
        • Kave B
        • Lee K
        • et al.
        A randomized crossover study to compare the user seal check and quantitative fit test between two types of duckbill N95 particulate respirator masks: the Halyard Fluidshield N95 and the BSN Medical ProShield N-95 particulate respirator masks.
        Anesthesia Intens Care. 2021; 49: 112-118
      9. United States Department of Labor. Occupational Safety and Health Administration. Assigned protection factor for the revised respiratory protection standard. Available at: https://www.osha.gov/sites/default/files/publications/3352-APF-respirators.pdf. (Accessed May 2022)

        • Regli A
        • Thalayasingam P
        • Bell E
        • Sommerfield A
        • von Ungern-Sternberg BS.
        More than half of front-line health care workers unknowingly used an N95/P2 mask without adequate airborne protection: An audit in a tertiary institution.
        Anesthesia Intens Care. 2021; 49: 404-411
        • Wild CEK
        • Wells H
        • Coetzee N
        • et al.
        Mixed-methods survey of health care workers’ experiences of personal protective equipment during the COVID-19 pandemic in Aotearoa/New Zealand.
        Int J Environ Res Pu. 2022; 19: 2474