Hasani Ali, Dawson Joseph, Fogarasi Magdalene, Snodderly Kirstie, Porter Daniel, Guha Suvajyoti
Division of Applied Mechanics, Office of Science and Engineering Laboratories (OSEL), U.S. Food and Drug Administration (FDA).
J Int Soc Respir Prot. 2023;40(2):1-14.
A manikin fit test method developed by the Center for Disease Control and Prevention's (CDC) National Institute of Occupational Safety and Health (NIOSH) has been proposed as an alternative to fit testing with human subjects. The advantages of a manikin fit test method over actual fit testing are that it does not require human subjects which can be resource intensive, and hence easier to implement. At the beginning of coronavirus 2019 (COVID-19) pandemic, although early studies showed that manikin fit can be maintained after several decontamination cycles, real world evidence obtained using human subjects revealed that the N95 respirators failed only after a few decontamination cycles. The goal of this article was to make modifications to the NIOSH's manikin fit-test method so it can mimic real world performance of N95 respirators better. After making modifications to this method, we then investigated the effect of long-term wear after donning of the respirators, repeated donning and doffing, as well as decontamination methods (i.e. autoclaving and microwave generated steam) on the fit factor. Averaging the overall manikin fit factor across all scenarios, our modified method overpredicted overall fit factor by only 7 % and 14 % compared to adult human subjects using a breathing routine that included simulated heavy breathing rates of 85, and 70 Liters/minute, respectively. In addition, a constant flow produced similar results as cyclic flow using a breathing simulator. The modified test method also offered the following additional insights into reuse of respirators during future pandemics - when reused within a single work shift, more than 5 donnings should be avoided; and microwave generated steam may be a more viable option for decontaminating N95 respirators compared to autoclaving for a single decontamination cycle.
美国疾病控制与预防中心（CDC）下属的国家职业安全与健康研究所（NIOSH）开发的一种人体模型适配测试方法，已被提议作为人体受试者适配测试的替代方法。与实际的适配测试相比，人体模型适配测试方法的优势在于它不需要人体受试者，而这可能会耗费大量资源，因此更易于实施。在2019冠状病毒病（COVID-19）大流行初期，尽管早期研究表明，经过几次消毒循环后人体模型适配仍可保持，但使用人体受试者获得的实际证据显示，N95口罩仅经过几次消毒循环就失效了。本文的目的是对NIOSH的人体模型适配测试方法进行修改，使其能更好地模拟N95口罩在实际使用中的性能。对该方法进行修改后，我们接着研究了佩戴口罩后的长期佩戴效果、反复佩戴和摘下，以及消毒方法（即高压灭菌和微波产生的蒸汽）对适配因子的影响。在所有场景中对整体人体模型适配因子进行平均计算，与分别采用模拟每分钟85升和70升重呼吸率的呼吸程序的成年人体受试者相比，我们改进后的方法对整体适配因子的预测仅高出7%和14%。此外，使用呼吸模拟器时，恒定流量产生的结果与循环流量相似。改进后的测试方法还为未来大流行期间口罩的重复使用提供了以下更多见解——在单个工作班次内重复使用时，应避免超过5次的佩戴；与单次消毒循环的高压灭菌相比，微波产生的蒸汽可能是一种更可行的N95口罩消毒选择。
