Department of Labour, Inspections and Enforcement Services, Mpumalanga Provincial Office, Witbank, South Africa.
Division of Occupational Health, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa.
Ann Work Expo Health. 2019 Oct 11;63(8):930-936. doi: 10.1093/annweh/wxz060.
N95 filtering facepiece respirators (FFRs) are widely used in healthcare to reduce transmission of airborne infectious diseases. These respirators are generally described as single use or limited reuse devices, but cost and operational issues mean that they may be donned and doffed multiple times. There is scant research on the effect of this practice on adequacy of fit.
The purpose of this study was to measure the effect on respirator fit of multiple donning and doffing of N95 FFRs.
This was an experiment in which 16 women and 9 men employed by the National Institute for Occupational Health (NIOH), Johannesburg, donned their same N95 FFR six times. All 25 were trained in the correct wearing of the devices before the experiment. Four models of respirators were used: the six who did not use respirators at work (novice subjects) were issued a 3M 1860 FFR and the others used their currently supplied one. During the experiment subjects donned their respirators under the supervision of the tester. Quantitative fit testing was done in the NIOH Occupational Hygiene laboratory after each donning according to the OSHA-Accepted Fit Test Protocol using the TSI PortaCount Pro+ Model 8038 Respirator Fit Tester. During the test, fit was measured after each of seven exercises and then an overall fit factor was computed. Only individuals who achieved an initial overall fit factor of ≥100 were allowed to continue participation in the study. Median overall fit factors were calculated for the 25 subjects for each donning and changes across them was examined using Wilcoxon rank sum tests. Men and women and frequent and infrequent users were compared across the six tests. Infrequent use was defined as subjects who wore respirators ≤ once per week, and novice subjects.
Two subjects (8%) had an overall fit factor <100 at fit Test 2, 6 (24%) at Test 3, and 8 (32%) at Tests 4, 5, and 6. Thirteen respirator users (52%) achieved ≥100 throughout the fit testing, so 12 had at least one failure at either Tests 2-6. Five of the 12 subjects with at least one failure showed persistent failures on all subsequent donnings. Six subjects out of 12 (50%) who failed a fit test achieved an overall fit factor >100 at a subsequent test. There was a significant difference between the median first and sixth overall fit factors (195 versus 150; P = 0.0271), but not between the second and sixth (161 versus 150; P = 0.3584). Men and women had similar overall fit factors, but infrequent users had larger average overall fit factors than frequent users after all six donnings.
Forty-eight percent of study subjects failed at least one fit test after re-donning an N95 FFR. The fit test data suggest that donning practices probably accounted for the fit test failures. The 50% of subjects who produced overall fit factors ≥100 after a test of <100 supports this contention.
N95 过滤式面罩（FFR）在医疗保健中被广泛用于减少空气传播传染病的传播。这些呼吸器通常被描述为一次性或有限重复使用的设备，但成本和操作问题意味着它们可能会被多次穿戴和脱下。关于这种做法对贴合度的影响，研究甚少。
本研究旨在测量多次穿戴和脱下 N95 FFR 对面罩贴合度的影响。
这是一项实验，约翰内斯堡国家职业健康研究所（NIOH）的 16 名女性和 9 名男性员工重复佩戴他们相同的 N95 FFR 六次。所有 25 名员工均在实验前接受了正确佩戴设备的培训。使用了四种型号的呼吸器：六名不在工作中使用呼吸器的人（新手受试者）被发放了 3M 1860 FFR，其余人则使用他们目前供应的呼吸器。在实验过程中，受试者在测试人员的监督下佩戴呼吸器。根据 OSHA 认可的 Fit 测试协议，在每次佩戴后，在 NIOH 职业卫生实验室进行定量 Fit 测试，使用 TSI PortaCount Pro+ Model 8038 呼吸器 Fit 测试仪。在测试过程中，在进行了七项运动后，分别测量了 Fit，然后计算了整体 Fit 因子。只有达到初始整体 Fit 因子≥100 的个人才被允许继续参与研究。对于每个佩戴者，为 25 名受试者计算了中位数整体 Fit 因子，并使用 Wilcoxon 秩和检验检查了它们之间的变化。比较了六次测试中的男性和女性以及频繁和不频繁使用者。不频繁使用者定义为每周佩戴呼吸器≤一次的受试者和新手受试者。
在 Fit 测试 2 时，有 2 名受试者（8%）整体 Fit 因子<100，在 Fit 测试 3 时，有 6 名受试者（24%），在 Fit 测试 4、5 和 6 时，有 8 名受试者（32%）。13 名呼吸器使用者（52%）在整个 Fit 测试中均达到≥100，因此，在 Fit 测试 2-6 中有 12 人至少有一次失败。在 12 名至少有一次失败的受试者中，有 5 名在所有后续佩戴中均出现持续失败。在 12 名未能通过 Fit 测试的受试者中，有 6 名（50%）在随后的测试中达到了整体 Fit 因子>100。第一次和第六次中位数整体 Fit 因子之间存在显著差异（195 与 150；P = 0.0271），但第二次和第六次之间无显著差异（161 与 150；P = 0.3584）。男性和女性的整体 Fit 因子相似，但在六次佩戴后，不频繁使用者的平均整体 Fit 因子大于频繁使用者。
48%的研究受试者在重新佩戴 N95 FFR 后至少有一次 Fit 测试失败。Fit 测试数据表明，穿戴实践可能是导致 Fit 测试失败的原因。50%的受试者在 Fit 测试<100 后产生了≥100 的整体 Fit 因子，这支持了这一论点。
