key: cord-317047-86rb6hov authors: Ippolito, Mariachiara; Vitale, Filippo; Accurso, Giuseppe; Iozzo, Pasquale; Gregoretti, Cesare; Giarratano, Antonino; Cortegiani, Andrea title: Medical masks and Respirators for the Protection of Healthcare Workers from SARS-CoV-2 and other viruses date: 2020-04-27 journal: Pulmonology DOI: 10.1016/j.pulmoe.2020.04.009 sha: doc_id: 317047 cord_uid: 86rb6hov Abstract The use of medical masks and respirators as personal protective equipment is pivotal to reducing the level of biological hazard to which healthcare workers are exposed during the outbreak of highly diffusible pathogens, such as the recent novel coronavirus SARS-CoV-2. Unfortunately, during this pandemic, supplies are rapidly running out worldwide, with potential consequences for the rate of occupational infections. Also, knowledge about specific characteristics of respirators is of utmost importance to select the proper type according to the clinical setting. A wide variety of literature is available on the topic, but mostly based on Influenza viruses infection models. Clinical evidence on the use of respirators is poor and interest in the topic has not been constant over time. A better understanding of SARS-CoV-2 transmission is needed, together with high-quality clinical data on the use of respirators or alternative devices. Moreover, healthcare workers, regardless of their level of experience, should receive specific training. This review aims to summarize the available evidence on the use of medical masks and respirators in the context of viral infections, especially the current coronavirus disease 2019 (COVID-19). The outbreak of highly diffusible pathogens, such as the recent pandemic of 81 SARS-CoV-2 infection, can increase the level of biological hazard to which 82 healthcare workers are exposed thus requiring the use of personal protective 83 equipment (PPE). Healthcare institutions should also plan the early isolation of 84 sources and provide training program on the appropriate use of PPE. [1] PPE, 85 defined as 'equipment worn to minimize exposure to hazards that cause serious 86 workplace injuries and illnesses', includes masks and respirators. [2] The use of PPE 87 and the application of other safety measures, especially in the context of a public 88 health emergency of international concern, is regulated by international and national 89 authorities that issue indications for healthcare workers and general population, 90 according to the characteristics of transmission and the different levels of exposure to 91 risk. [3] Unfortunately, in the case of a pandemic, the supply of PPE can be 92 insufficient or heterogeneously distributed around the world, due to centralized 93 production hubs, transport difficulties, lack of stockpiles, panic buying and 94 appropriate heavy use. [7] with a rising demand for incontrovertible and clear data. The term 'respirators', in the context of personal protective equipment, should 126 be intended as filtering media, usually in the form of half-face or full-face masks, 127 used as protection for healthcare workers exposed to pathogens. 128 The main performance characteristics of medical masks and respirators are 130 summarized in Table 1 . 131 Medical masks are loose-fitting and disposable. They are meant to reduce the 132 spread of the wearers' respiratory droplets to other people and the environment and 133 to provide a general protection of the wearer from large droplets, usually generated 134 by cough or sneezing, and body fluid splashes. Type I medical masks are generally 135 used for patients with the aim of controlling the source, and Type II or Type IIR by 136 healthcare workers in operatory room or procedural settings. The main difference 137 among the types is according to their bacterial filtration efficiency, i.e. the efficiency 138 as a barrier to bacteria penetration. The protection from splashes is only provided by 139 and size. Inhalation and exhalation seal checks will be then performed before every 160 use, to tighten the device properly and confirm that it was put on properly. Filtering 161 facepiece respirators are also available in versions with an expiratory valve, which 162 make them more comfortable for long-time wearing. The valve, in fact, opens during 163 the expiratory phase of the wearer's breathing, allowing the exhaled air to flow-out. 164 The protection from body fluids and splashes is rarely guaranteed by valved FFR, 165 and has to be confirmed by the label "Type IIR", as for medical masks. The presence 166 of an expiratory valve also reduces goggles fogging. [10,11] The nominal protection 167 factor is an important index of a respirator performance. It is measured as the ratio 168 between external concentration of contaminant and its concentration measured on 169 the inner side of the device (Cout/Cin). If we assume Cout to be 1, with Cin = (1 -170 filtration performance), we can easily calculate the nominal protection factor. As an 171 example, a respirator with a 94% filtration performance, will have a nominal 172 protection factor of 16. In this case, the value means that the contaminant is 16 times less concentrated inside the device than in the external environment. Another 174 parameter to be known is the threshold limit value, a threshold level of concentration, 175 specific for each contaminant, which must not be exceeded if the safety of the wearer 176 is to be guaranteed. The real-life protection given by a respirator, in fact, depends on 177 its assigned protection factor, an index that depends on the protection factor provided 178 by the respirator, but also by the ratio between the concentration of the contaminant 179 and its threshold limit value. [11] In the case of some biological contaminants, such 180 as the case of SARS-CoV-2, a threshold limit value is not known, and so the 181 An interesting pilot study has evaluated N95 respirator and medical masks in 288 the setting of home care [30] . The participants were three nurses, involved in 289 healthcare assistance at a patient 's home. The workplace protection factor was the 290 primary outcome of the study, defined as Cout/Cin, i.e. the ratio between the aerosol 291 concentrations inside (Cin) and outside (Cout) the device. The measurement of workplace protection factor was repeated twice for each participant, one with N95 293 respirator and one with medical mask. N95 respirators provided higher respiratory 294 protection in comparison to medical masks, but the protection factors varied on an 295 individual basis, also depending on the activity performed, with a greater risk in 296 specific tasks like tracheal suctioning or nebulizer treatments. [30] bench study, they found that applying a medical mask on the source could 312 significantly reduce the exposure of the receiver to a radiolabeled aerosol, providing 313 a higher protection than a N95 respirator worn by the receiver. The study was 314 conducted in a chamber designed with 6 air exchanges per hour to permit both 315 dilution and deflection of exhaled particles, and the effect was lost at 0 air exchange per hour. Since the effectiveness of respirators is strongly dependent on their 317 capacity to seal to the face, a more recent bench study has used modern and more steam, and moist heat) on two models of N95 respirators, previously contaminated 354 with H5N1. [36] Post decontamination viral load results decreased with all the 355 methods. Filter performance was also tested, and no alterations were registered. 356 These findings were in line with data on six respirators with H1N1 contamination [37] . 357 Other studies have observed physical degradation of respirator materials such as the 358 fibers composing the body material, which is probably less resistant than the filters. 359 [38] Thus, the decontamination should balance the need for inactivation of the 360 specific pathogen, even from the interior layers of the respirator, and the need to 361 preserve the filtering performance, the structure of the respirator and its fitting 362 characteristics. Further studies are needed to clarify the safety profiles of re-using 363 procedures of disposable PPE. Meanwhile, if re-use is needed, the user should check that the decontamination tests have already been performed on the specific 365 model of FFR. 366 The use of cloth-masks in comparison with medical mask and usual 367 protection, has also been investigated by a multicentre cluster randomized trial, 368 including 1607 healthcare workers. The trialshowed a significantly higher rate of ILI in 369 the cloth-mask intervention group (RR=13.00, 95% CI 1.69 to 100.07) compared with 370 the medical mask intervention group and with the entire control group, where 371 healthcare workers wore their usual protection (including N95 respirator, no mask, 372 medical mask, cloth mask or a combination of medical and cloth mask). 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