1260 infection control & hospital epidemiology october 2017, vol. 38, no. 10
Performance of a Novel Non–Fit-Tested HEPA Filtering Face Mask
The use of a fit-tested N95 or FFP2 half-face respirator is recommended to protect against transmission of airborne pathogens,1,2 but poor compliance with correct mask usage due to discomfort and the need for repeated fit-testing are proble- matic. The National Academies Institute of Medicine have recommended research to obviate the need for fit testing.3 We previously studied a compact, reusable, high-efficiency
particulate air (HEPA) filtering mask that can be cut to size (Totobobo, Dream Lab One Pte Ltd, Singapore). Its perfor- mance was suboptimal but not significantly worse than N95 respirators used without regular fit testing.4 The new generation of mask incorporates changes that should result in a better seal. This mask is heat moldable and incorporates
larger HEPA filters that reduce resistance to flow through the filters, which should decrease entrainment of unfiltered air around the mask.
methods
We conducted a pragmatic a prospective, unblinded, crossover study of the filtration factor of next-generation Totobobo masks compared to previously fit-tested N95 respirators (models 1860, 1860s, or 1862; 3M Health Care, St Paul, MN). Secondary end points were the proportion of subjects achieving a filtration factor ≥100 and subjective comfort. Approval was obtained from The Chinese University of Hong Kong New Territories East Cluster Clinical Research Ethics Committee, and informed consent was obtained from each participant. In total, 22 healthy volunteers who had previously passed a
fit test with a model 1860, 1860s, or 1862 N95 respirator tested the Totobobo mask and their previously identified fit-tested respirators in a computer-generated random order. Prior to testing the N95 respirators, subjects adjusted their respirators and performed a user seal test. For each participant, a Totobobo mask was molded to fit the
volunteer’s face after it was immersed in hot water and warmed with a hair dryer. The inventor visually assessed the fit by examining whether a water mark formed a continuous line, indicating a circumferential seal against the participant’s face. If necessary, specially designed rubber bands supplied by the manufacturer were added to improve the fit. The inventor was only involved in fitting and took no part in the measurement of filtration fraction, data analysis, or data interpretation.
Volunteers underwent a standard, previously described, mask- fitting protocol to measure the filtration fraction.4 This pro- cedure involved calculating a filtration fraction from particle concentrations in air samples taken from inside and just out- side the masks while performing different movements. All subjects were asked to complete a questionnaire (Table 1) on mask comfort immediately after the protocol was performed.
table 1. Tolerability Questionnaire Characteristic Breathingb
Ear comfort
Nose comfortb Face comfortb
General comfortb
Type of Mask N95
Totobobo N95
Totobobo N95
Totobobo N95
Totobobo N95
Totobobo
affected. bP=.001 (N95 vs Totobobo).
Filtration factors and questionnaire responseswere analyzed
using the Mann-Whitney U test. The proportion of subjects achieving a filtration factor ≥100 were analyzed using a χ2 test. P<0.05 was considered significant. The sample size was calculated to achieve a power of 80% based on an effect size of a probability of 0.24 that the filtration factor using one mask was less than the filtration factor using the other mask, with an α value of 0.05 (2-tailed).5
results
The median age of study participants was 42 years (inter- quartile range [IQR], 37.25–49.5); 86% were female. The median time since the participant’s lastN95 fit-test was 4 years (IQR, 1–9.75). The median filtration factor was 77.5 (IQR, 49.75–135) for N95 masks and 84.5 (35.5–160.5) for Totobobo masks (P=.981). The filtration factor was ≥100 in 9 of 22 participants with N95 respirators and in 10 of 22 participants with Totobobo masks. Years since fit testing and N95 filtration factor were negatively correlated (Spearman’s ρ, −0.684; P=.01). The results of the tolerability questionnaire are given in Table 1.
discussion
The performance of the Totobobo mask adjusted to fit the subject’s face but not fit tested was similar to the performance of previously fit-tested N95 respirators, although both performance levels were suboptimal. This result suggests that Totobobo masks should not be used to replace N95 respirators if regular fit testing is possible but that these masks do show some promise when regular fit testing is not possible. Fit testing is recommended annually or whenever there
are visible changes in physical condition that could affect respirator fit (eg, facial scarring, dental changes, or cosmetic surgery), or an obvious change in body weight.6,7 This recommendation imposes considerable logistic and financial burdens and is controversial.7 In some situations, such as ours,
Filtration Factora 1 (1–2)
0 (0–1) 1 (0–1) 0 (0–1) 1 (1–2) 0 (0–1) 1 (1–2) 0 (0–1) 1 (1–2) 0 (0–1)
a0, not affected; 1, mildly affected; 2, moderately affected; 3, severely
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