Personal Interventions for Reducing Exposure and Risk for Outdoor Air Pollution: An Official American Thoracic Society Workshop Report.

Poor air quality affects the health and wellbeing of large populations around the globe. Although source controls are the most effective approaches for improving air quality and reducing health risks, individuals can also take actions to reduce their personal exposure by staying indoors, reducing physical activity, altering modes of transportation, filtering indoor air, and using respirators and other types of face masks. A synthesis of available evidence on the efficacy, effectiveness, and potential adverse effects or unintended consequences of personal interventions for air pollution is needed by clinicians to assist patients and the public in making informed decisions about use of these interventions. To address this need, the American Thoracic Society convened a workshop in May of 2018 to bring together a multidisciplinary group of international experts to review the current state of knowledge about personal interventions for air pollution and important considerations when helping patients and the general public to make decisions about how best to protect themselves. From these discussions, recommendations were made regarding when, where, how, and for whom to consider personal interventions. In addition to the efficacy and safety of the various interventions, the committee considered evidence regarding the identification of patients at greatest risk, the reliability of air quality indices, the communication challenges, and the ethical and equity considerations that arise when discussing personal interventions to reduce exposure and risk from outdoor air pollution.

Evaluación de la eficacia de las lengüetas en las tiras de la mascarilla autofiltrante para mejorar las técnicas de retirada adecuadas al mismo tiempo que se reduce la transmisión por contacto de los patógenos.

RESUMENLas mascarillas respiratorias autofiltrantes (filtering facepiece respirators, FFR) N95 certificadas por el Instituto Nacional de Seguridad y Salud Laborales (National Institute for Occupational Safety and Health, NIOSH) se utilizan en los centros de atención sanatoria como medida de control para mitigar las exposiciones a partículas atmosféricas infecciosas. Cuando la superficie externa de una FFR se contamina, supone un riesgo de transmisión para el usuario. La guía de los Centros para el Control y Prevención de Enfermedades (Centers for Disease Control and Prevention, CDC) recomienda que el personal sanitario retire las FFR agarrando las tiras en la parte posterior de la cabeza para evitar el contacto con la superficie posiblemente contaminada. Al parecer, la adherencia a la técnica de retirada adecuada es baja, debido a numerosos factores que incluyen la dificultad para ubicar y agarrar las tiras. En este estudio se compara el impacto de lengüetas ubicadas en las tiras de la FFR con el de mascarillas comparativas (sin lengüetas) sobre la retirada adecuada, la facilidad de uso, la comodidad y la reducción de la transmisión de la contaminación al usuario. El uso de un agente fluorescente como rastreador de contactos para explorar la contaminación de las FFR en manos y áreas de la cabeza de 20 sujetos humanos demostró que no hubo diferencia entre las tiras de la FFR con lengüetas y las mascarillas comparativas en el sentido de estimular la retirada adecuada de las mismas (p = 0.48), pero la hizo más fácil (p = 0.04), según indican siete de ocho sujetos que usaron las lengüetas. Siete de 20 sujetos opinaron que las FFR con lengüetas son más fáciles de retirar, mientras que solo dos de 20 sujetos indicaron que las FFR sin lengüetas son más fáciles de retirar. La incomodidad no fue un factor relevante para ninguno de los tipos de tiras de las FFR. Al retirar una FFR con las manos contaminadas, el uso de lengüetas redujo de forma importante la cantidad del rastreador de contactos transferida en comparación con las tiras sin lengüetas (p = 0.012). Las FFR con lengüetas en las tiras están asociadas con la facilidad de la retirada y una transferencia notablemente menor del rastreador de contactos fluorescente.

A Control Banding Framework for Protecting the US Workforce from Aerosol Transmissible Infectious Disease Outbreaks with High Public Health Consequences.

Recent high-profile infectious disease outbreaks illustrate the importance of selecting appropriate control measures to protect a wider range of employees, other than those in healthcare settings. In such settings, where routine exposure risks are often high, control measures may be more available, routinely implemented, and studied for effectiveness. In the absence of evidence-based guidelines or established best practices for selecting appropriate control measures, employers may unduly rely on personal protective equipment (PPE) because of its wide availability and pervasiveness as a control measure, circumventing other effective options for protection. Control banding is one approach that may be used to assign job tasks into risk categories and prioritize the application of controls. This article proposes an initial control banding framework for workers at all levels of risk and incorporates a range of control options, including PPE. Using the National Institutes of Health (NIH) risk groups as a surrogate for toxicity and combining the exposure duration with the exposure likelihood, we can generate the risk of a job task to the worker.

Healthcare personnel exposure in an emergency department during influenza season.

INTRODUCTION: Healthcare personnel are at high risk for exposure to influenza by direct and indirect contact, droplets and aerosols, and by aerosol generating procedures. Information on air and surface influenza contamination is needed to assist in developing guidance for proper prevention and control strategies. To understand the vulnerabilities of healthcare personnel, we measured influenza in the breathing zone of healthcare personnel, in air and on surfaces within a healthcare setting, and on filtering facepiece respirators worn by healthcare personnel when conducting patient care. METHODS: Thirty participants were recruited from an adult emergency department during the 2015 influenza season. Participants wore personal bioaerosol samplers for six hours of their work shift, submitted used filtering facepiece respirators and medical masks and completed questionnaires to assess frequency and types of interactions with potentially infected patients. Room air samples were collected using bioaerosol samplers, and surface swabs were collected from high-contact surfaces within the adult emergency department. Personal and room bioaerosol samples, surface swabs, and filtering facepiece respirators were analyzed for influenza A by polymerase chain reaction. RESULTS: Influenza was identified in 42% (53/125) of personal bioaerosol samples, 43% (28/ 96) of room bioaerosol samples, 76% (23/30) of pooled surface samples, and 25% (3/12) of the filtering facepiece respirators analyzed. Influenza copy numbers were greater in personal bioaerosol samples (17 to 631 copies) compared to room bioaerosol samples (16 to 323 copies). Regression analysis suggested that the amount of influenza in personal samples was approximately 2.3 times the amount in room samples (Wald χ2 = 16.21, p<0.001). CONCLUSIONS: Healthcare personnel may encounter increased concentrations of influenza virus when in close proximity to patients. Occupations that require contact with patients are at an increased risk for influenza exposure, which may occur throughout the influenza season. Filtering facepiece respirators may become contaminated with influenza when used during patient care.

Assessment of environmental and surgical mask contamination at a student health center - 2012-2013 influenza season.

Increased understanding of influenza transmission is critical for pandemic planning and selecting appropriate controls for healthcare personnel safety and health. The goals of this pilot study were to assess environmental contamination in different areas and at two time periods in the influenza season and to determine the feasibility of using surgical mask contamination to evaluate potential exposure to influenza virus. Bioaerosol samples were collected over 12 days (two 6-day sessions) at 12 locations within a student health center using portable two-stage bioaerosol samplers operating 8 hr each day. Surface samples were collected each morning and afternoon from common high-contact non-porous hard surfaces from rooms and locations where bioaerosol samplers were located. Surgical masks worn by participants while in contact with patients with influenza-like illness were collected. A questionnaire administered to each of the 12 participants at the end of each workday and another at the end of each workweek assessed influenza-like illness symptoms, estimated the number of influenza-like illness patient contacts, hand hygiene, and surgical mask usage. All samples were analyzed using qPCR. Over the 12 days of the study, three of the 127 (2.4%) bioaerosol samples, 2 of 483 (0.41%) surface samples, and 0 of 54 surgical masks were positive for influenza virus. For the duration of contact that occurred with an influenza patient on any of the 12 days, nurse practitioners and physicians reported contacts with influenza-like illness patients >60 min, medical assistants reported 15-44 min, and administrative staff reported <30 min. Given the limited number of bioaerosol and surface samples positive for influenza virus in the bioaerosol and surface samples, the absence of influenza virus on the surgical masks provides inconclusive evidence for the potential to use surgical masks to assess exposure to influenza viruses. Further studies are needed to determine feasibility of this approach in assessing healthcare personnel exposures. Information learned in this study can inform future field studies on influenza transmission.

Assessment of influenza virus exposure and recovery from contaminated surgical masks and N95 respirators.

Healthcare workers (HCWs) are at significantly higher risk of exposure to influenza virus during seasonal epidemics and global pandemics. During the 2009 influenza pandemic, some healthcare organizations recommended that HCWs wear respiratory protection such as filtering facepiece respirators, while others indicated that facemasks such as surgical masks (SMs) were sufficient. To assess the level of exposure a HCW may possibly encounter, the aim of this study was to (1.) evaluate if SMs and N95 respirators can serve as "personal bioaerosol samplers" for influenza virus and (2.) determine if SMs and N95 respirators contaminated by influenza laden aerosols can serve as a source of infectious virus for indirect contact transmission. This effort is part of a National Institute for Occupational Safety and Health 5-year multidisciplinary study to determine the routes of influenza transmission in healthcare settings. A coughing simulator was programmed to cough aerosol particles containing influenza virus over a wide concentration range into an aerosol exposure simulation chamber virus/L of exam room air), and a breathing simulator was used to collect virus on either a SM or N95 respirator. Extraction buffers containing nonionic and anionic detergents as well as various protein additives were used to recover influenza virus from the masks and respirators. The inclusion of 0.1% SDS resulted in maximal influenza RNA recovery (41.3%) but with a complete loss of infectivity whereas inclusion of 0.1% bovine serum albumin resulted in reduced RNA recovery (6.8%) but maximal retention of virus infectivity (17.9%). Our results show that a HCW's potential exposure to airborne influenza virus can be assessed in part through analysis of their SMs and N95 respirators, which can effectively serve as personal bioaerosol samplers.

Transfer of bacteriophage MS2 and fluorescein from N95 filtering facepiece respirators to hands: Measuring fomite potential.

Contact transmission of pathogens from personal protective equipment is a concern within the healthcare industry. During public health emergency outbreaks, resources become constrained and the reuse of personal protective equipment, such as N95 filtering facepiece respirators, may be needed. This study was designed to characterize the transfer of bacteriophage MS2 and fluorescein between filtering facepiece respirators and the wearer's hands during three simulated use scenarios. Filtering facepiece respirators were contaminated with MS2 and fluorescein in droplets or droplet nuclei. Thirteen test subjects performed filtering facepiece respirator use scenarios including improper doffing, proper doffing and reuse, and improper doffing and reuse. Fluorescein and MS2 contamination transfer were quantified. The average MS2 transfer from filtering facepiece respirators to the subjects' hands ranged from 7.6-15.4% and 2.2-2.7% for droplet and droplet nuclei derived contamination, respectively. Handling filtering facepiece respirators contaminated with droplets resulted in higher levels of MS2 transfer compared to droplet nuclei for all use scenarios (p = 0.007). MS2 transfer from droplet contaminated filtering facepiece respirators during improper doffing and reuse was greater than transfer during improper doffing (p = 0.008) and proper doffing and reuse (p = 0.042). Droplet contamination resulted in higher levels of fluorescein transfer compared to droplet nuclei contaminated filtering facepiece respirators for all use scenarios (p = 0.009). Fluorescein transfer was greater for improper doffing and reuse (p = 0.007) from droplet contaminated masks compared to droplet nuclei contaminated filtering facepiece respirators and for improper doffing and reuse when compared improper doffing (p = 0.017) and proper doffing and reuse (p = 0.018) for droplet contaminated filtering facepiece respirators. For droplet nuclei contaminated filtering facepiece respirators, the difference in MS2 and fluorescein transfer did not reach statistical significance when comparing any of the use scenarios. The findings suggest that the results of fluorescein and MS2 transfer were consistent and highly correlated across the conditions of study. The data supports CDC recommendations for using proper doffing techniques and discarding filtering facepiece respirators that are directly contaminated with secretions from a cough or sneeze.

Physiological Evaluation of Cooling Devices in Conjunction With Personal Protective Ensembles Recommended for Use in West Africa.

OBJECTIVE: Cooling devices (CDs) worn under personal protective equipment (PPE) can alleviate some of the heat stress faced by health care workers responding to the Ebola outbreak in West Africa. METHODS: Six healthy, young individuals were tested while wearing 4 different CDs or no cooling (control) under PPE in an environmental chamber (32°C/92% relative humidity) while walking (3 METs, 2.5 mph, 0% grade) on a treadmill for 60 minutes. Exercise was preceded by a 15-minute stabilization period and a 15-minute donning period. RESULTS: The control condition resulted in a significantly higher rectal temperature (Tre) at the end of the exercise than did all CD conditions (CD1, P=0.004; CD2, P=0.01; CD3, P=0.000; CD4, P=0.000) with CD1 and CD2 resulting in a higher Tre than CD3 and CD4 (P<0.05). The control condition resulted in a higher heart rate (HR) at the end of exercise than did the CD3 (P=0.01) and CD4 (P=0.009) conditions, whereas the HR of the CD1 and CD2 conditions was higher than that of the CD3 and CD4 conditions (P<0.05). Weight loss in the control condition was higher than in the CD3 (P=0.003) and CD4 (P=0.01) conditions. Significant differences in subjective measurements of thermal stress were found across conditions and time. CONCLUSIONS: Use of CDs can be advantageous in decreasing the negative physiological and subjective responses to the heat stress encountered by health care workers wearing PPE in hot and humid environments. (Disaster Med Public Health Preparedness. 2017;11:573-579).

Physiological Evaluation of Personal Protective Ensembles Recommended for Use in West Africa.

OBJECTIVE: Personal protective equipment (PPE) provides health care workers with a barrier to prevent human contact with viruses like Ebola and potential transmission of the disease. However, PPE can also introduce an additional physiological burden from potentially increased heat stress. This study evaluated the human physiological and subjective responses to continuous light exercise within environmental conditions similar to those in West Africa while wearing 3 different, commonly used PPE ensembles (E1, E2, and E3). METHODS: Six healthy individuals were tested in an environmental chamber (32°C, 92% relative humidity) while walking (3 METs, 2.5 mph, 0% incline) on a treadmill for 60 minutes. All subjects wore medical scrubs and PPE items. E1 also had a face shield and fluid-resistant surgical gown; E2 additionally included goggles, coverall, and separate hood; and E3 also contained a highly impermeable coverall, separate hood, and surgical mask cover over the N95 respirator. RESULTS: Heart rate and core temperature at the end of the exercise were significantly higher for E2 and E3 than for E1. Subjective perceptions of heat and exertion were significantly higher for E2 and E3 than for E1. CONCLUSIONS: Heat stress and PPE training, as well as the implementation of a work-to-rest ratio that avoids dehydration and possible heat stress issues, are recommended. (Disaster Med Public Health Preparedness. 2017;11:580-586).

Recommended test methods and pass/fail criteria for a respirator fit capability test of half-mask air-purifying respirators.

This study assessed key test parameters and pass/fail criteria options for developing a respirator fit capability (RFC) test for half-mask air-purifying particulate respirators. Using a 25-subject test panel, benchmark RFC data were collected for 101 National Institute for Occupational Safety and Health-certified respirator models. These models were further grouped into 61 one-, two-, or three-size families. Fit testing was done using a PortaCount® Plus with N95-Companion accessory and an Occupational Safety and Health Administration-accepted quantitative fit test protocol. Three repeated tests (donnings) per subject/respirator model combination were performed. The panel passing rate (PPR) (number or percentage of the 25-subject panel achieving acceptable fit) was determined for each model using five different alternative criteria for determining acceptable fit. When the 101 models are evaluated individually (i.e., not grouped by families), the percentages of models capable of fitting >75% (19/25 subjects) of the panel were 29% and 32% for subjects achieving a fit factor ≥100 for at least one of the first two donnings and at least one of three donnings, respectively. When the models are evaluated grouped into families and using >75% of panel subjects achieving a fit factor ≥100 for at least one of two donnings as the PPR pass/fail criterion, 48% of all models can pass. When >50% (13/25 subjects) of panel subjects was the PPR criterion, the percentage of passing models increased to 70%. Testing respirators grouped into families and evaluating the first two donnings for each of two respirator sizes provided the best balance between meeting end user expectations and creating a performance bar for manufacturers. Specifying the test criterion for a subject obtaining acceptable fit as achieving a fit factor ≥100 on at least one out of the two donnings is reasonable because a majority of existing respirator families can achieve an PPR of >50% using this criterion. The different test criteria can be considered by standards development organizations when developing standards.

Project BREATHE - Prototype Respirator Evaluation Utilizing Newly Proposed Respirator Test Criteria.

Machine and human subject testing of four prototype filtering facepiece respirators (FFR) and two commercial FFR was carried out utilizing recently proposed respirator test criteria that address healthcare worker-identified comfort and tolerance issues. Overall, two FFR (one prototype, one commercial model) were able to pass all eight criteria and three FFR (two prototypes, one commercial model) were able to pass seven of eight criteria. One prototype FFR was not tested against the criteria due to an inability to obtain satisfactory results on human subject quantitative respirator fit testing. Future studies, testing different models and styles of FFR against the proposed criteria, will be required to gauge the overall utility and effectiveness of the criteria in determining FFR comfort and tolerance issues that may impact user compliance and, by extension, protection.

A comparison of facemask and respirator filtration test methods.

NIOSH published a Federal Register Notice to explore the possibility of incorporating FDA required filtration tests for surgical masks (SMs) in the 42 CFR Part 84 respirator certification process. There have been no published studies comparing the filtration efficiency test methods used for NIOSH certification of N95 filtering facepiece respirators (N95 FFRs) with those used by the FDA for clearance of SMs. To address this issue, filtration efficiencies of "N95 FFRs" including six N95 FFR models and three surgical N95 FFR models, and three SM models were measured using the NIOSH NaCl aerosol test method, and FDA required particulate filtration efficiency (PFE) and bacterial filtration efficiency (BFE) methods, and viral filtration efficiency (VFE) method. Five samples of each model were tested using each method. Both PFE and BFE tests were done using unneutralized particles as per FDA guidance document. PFE was measured using 0.1 µm size polystyrene latex particles and BFE with ∼3.0 µm size particles containing Staphylococcus aureus bacteria. VFE was obtained using ∼3.0 µm size particles containing phiX 174 as the challenge virus and Escherichia coli as the host. Results showed that the efficiencies measured by the NIOSH NaCl method for "N95 FFRs" were from 98.15-99.68% compared to 99.74-99.99% for PFE, 99.62-99.9% for BFE, and 99.8-99.9% for VFE methods. Efficiencies by the NIOSH NaCl method were significantly (p = <0.05) lower than the other methods. SMs showed lower efficiencies (54.72-88.40%) than "N95 FFRs" measured by the NIOSH NaCl method, while PFE, BFE, and VFE methods produced no significant difference. The above results show that the NIOSH NaCl method is relatively conservative and is able to identify poorly performing filtration devices. The higher efficiencies obtained using PFE, BFE and VFE methods show that adding these supplemental particle penetration methods will not improve respirator certification.

Prevalence of Respiratory Protective Devices in U.S. Health Care Facilities: Implications for Emergency Preparedness.

An online questionnaire was developed to explore respiratory protective device (RPD) prevalence in U.S. health care facilities. The survey was distributed to professional nursing society members in 2014 and again in 2015 receiving 322 and 232 participant responses, respectively. The purpose of this study was to explore if the emergency preparedness climate associated with Ebola virus disease changed the landscape of RPD use and awareness. Comparing response percentages from the two sampling time frames using bivariate analysis, no significant changes were found in types of RPDs used in health care settings. N95 filtering facepiece respirators continue to be the most prevalent RPD used in health care facilities, but powered air-purifying respirators are also popular, with regional use highest in the West and Midwest. Understanding RPD use prevalence could ensure that health care workers receive appropriate device trainings as well as improve supply matching for emergency RPD stockpiling.

Speech intelligibility assessment of protective facemasks and air-purifying respirators.

Speech Intelligibility (SI) is the perceived quality of sound transmission. In healthcare settings, the ability to communicate clearly with coworkers, patients, etc., is crucial to quality patient care and safety. The objectives of this study were to: (1) assess the suitability of the Speech Transmission Index (STI) methods for testing reusable and disposable facial and respiratory personal protective equipment (protective facemasks [PF], N95 filtering facepiece respirators [N95 FFR], and elastomeric half-mask air-purifying respirators [EAPR]) commonly worn by healthcare workers; (2) quantify STI levels of these devices; and (3) contribute to the scientific body of knowledge in the area of SI. SI was assessed using the STI under two experimental conditions: (1) a modified version of the National Fire Protection Association 1981 Supplementary Voice Communications System Performance Test at a Signal to Noise Ratio (SNR) of -15 (66 dBA) and (2) STI measurements utilizing a range of modified pink noise levels (52.5 dBA (-2 SNR) - 72.5 dBA (+7 SNR)) in 5.0 dBA increments. The PF models (Kimberly Clark 49214 and 3 M 1818) had the least effect on SI interference, typically deviating from the STI baseline (no-mask condition) by 3% and 4% STI, respectively. The N95FFR (3 M 1870, 3 M 1860) had more effect on SI interference, typically differing from baseline by 13% and 17%, respectively, for models tested. The EAPR models (Scott Xcel and North 5500) had the most significant impact on SI, differing from baseline by 42% for models tested. This data offers insight into the performance of these apparatus with respect to STI and may serve as a reference point for future respirator design considerations, standards development, testing and certification activities.

The Respiratory Protection Effectiveness Clinical Trial (ResPECT): a cluster-randomized comparison of respirator and medical mask effectiveness against respiratory infections in healthcare personnel.

BACKGROUND: Although N95 filtering facepiece respirators and medical masks are commonly used for protection against respiratory infections in healthcare settings, more clinical evidence is needed to understand the optimal settings and exposure circumstances for healthcare personnel to use these devices. A lack of clinically germane research has led to equivocal, and occasionally conflicting, healthcare respiratory protection recommendations from public health organizations, professional societies, and experts. METHODS: The Respiratory Protection Effectiveness Clinical Trial (ResPECT) is a prospective comparison of respiratory protective equipment to be conducted at multiple U.S. study sites. Healthcare personnel who work in outpatient settings will be cluster-randomized to wear N95 respirators or medical masks for protection against infections during respiratory virus season. Outcome measures will include laboratory-confirmed viral respiratory infections, acute respiratory illness, and influenza-like illness. Participant exposures to patients, coworkers, and others with symptoms and signs of respiratory infection, both within and beyond the workplace, will be recorded in daily diaries. Adherence to study protocols will be monitored by the study team. DISCUSSION: ResPECT is designed to better understand the extent to which N95s and MMs reduce clinical illness among healthcare personnel. A fully successful study would produce clinically relevant results that help clinician-leaders make reasoned decisions about protection of healthcare personnel against occupationally acquired respiratory infections and prevention of spread within healthcare systems. TRIAL REGISTRATION: The trial is registered at clinicaltrials.gov, number NCT01249625 (11/29/2010).

Effect of multiple alcohol-based hand rub applications on the tensile properties of thirteen brands of medical exam nitrile and latex gloves.

Current CDC guidance for the disinfection of gloved hands during the doffing of personal protective equipment (PPE) following the care of a patient with Ebola recommends for multiple applications of alcohol-based hand rub (ABHR) on medical exam gloves. To evaluate possible effects of ABHR applications on glove integrity, thirteen brands of nitrile and latex medical exam gloves from five manufacturers and two different ABHRs were included in this study. A pair of gloves were worn by a test operator and the outside surfaces of the gloves were separately treated with an ABHR for 1-6 applications. Tensile strength and ultimate elongation of the gloves without any ABHR treatments (control gloves) and gloves after 1-6 ABHR applications were measured based on the ASTM D412 standard method. In general, tensile strength decreased with each ABHR application. ABHRs had more effect on the tensile strength of the tested nitrile than latex gloves, while ethanol-based ABHR (EBHR) resulted in lesser changes in tensile strength compared to isopropanol-based ABHR (IBHR). The results show that multiple EBHR applications on the latex gloves and some of the nitrile gloves tested should be safe for Ebola PPE doffing based on the CDC guidance. Appropriate hospital staff practice using ABHR treatment and doffing gloves is recommended to become more familiar with changes in glove properties.

Evaluation of gowns and coveralls used by medical personnel working with Ebola patients against simulated bodily fluids using an Elbow Lean Test.

Gowns and coveralls are important components of protective ensembles used during the management of known or suspected Ebola patients. In this study, an Elbow Lean Test was used to obtain a visual semi-quantitative measure of the resistance of medical protective garments to the penetration of two bodily fluid simulants. Tests were done on swatches of continuous and discontinuous regions of fabrics cut from five gowns and four coveralls at multiple elbow pressure levels (2-44 PSI). Swatches cut from the continuous regions of one gown and two coveralls did not have any strike-through. For discontinuous regions, only the same gown consistently resisted fluid strike-through. As hypothesized, with the exception of one garment, fluid strike-through increased with higher applied elbow pressure, was higher for lower fluid surface tension, and was higher for the discontinuous regions of the protective garments.

Assessing the efficacy of tabs on filtering facepiece respirator straps to increase proper doffing techniques while reducing contact transmission of pathogens.

NIOSH-certified N95 filtering facepiece respirators (FFRs) are used in healthcare settings as a control measure to mitigate exposures to airborne infectious particles. When the outer surface of an FFR becomes contaminated, it presents a contact transmission risk to the wearer. The Centers for Disease Control and Prevention (CDC) guidance recommends that healthcare workers (HCWs) doff FFRs by grasping the straps at the back of the head to avoid contact with the potentially contaminated surface. Adherence to proper doffing technique is reportedly low due to numerous factors including difficulty in locating and grasping the straps. This study compares the impact of tabs placed on FFR straps to controls (without tabs) on proper doffing, ease of use and comfort, and reduction of transfer of contamination to the wearer. Utilizing a fluorescent agent as a tracer to track contamination from FFRs to hand and head areas of 20 human subjects demonstrated that there was no difference in tabbed FFR straps and controls with respect to promoting proper doffing (p = 0.48), but did make doffing easier (p = 0.04) as indicated by 7 of 8 subjects that used the tabs. Seven of the 20 subjects felt that FFRs with tabs were easier to remove, while only 2 of 20 indicated that FFRs without tabs were easier to remove. Discomfort was not a factor for either FFR strap type. When removing an FFR with contaminated hands, the use of the tabs significantly reduced the amount of tracer transfer compared to straps without tabs (p = 0.012). FFRs with tabs on the straps are associated with ease of doffing and significantly less transfer of the fluorescent tracer.

Capture of 0.1-µm aerosol particles containing viable H1N1 influenza virus by N95 filtering facepiece respirators.

Nosocomial infections pose an escalating threat to both patients and healthcare workers (HCWs). A widely recommended device for individual respiratory protection, the N95 filtering facepiece respirator (FFR) has been shown to provide efficient filtration of inert particles larger and smaller than the nominal most-penetrating particle size (MPPS) range, 0.03-0.3 µm. Humans generate respiratory aerosols in the MPPS range, suggesting that short-range disease transmission could occur via small infectious particles. Data presented here show that the N95 FFR will afford a significant measure of protection against infectious particles as small as a bare H1N1 influenza virion, and that the capture mechanism does not discriminate in favor of, or against, biological particles.

Temporal changes in filtering-facepiece respirator fit.

A three-year study examined changes in N95 filtering-facepiece respirator (FFR) fit at six-month intervals and the relationship between fit and changes in weight for 229 subjects. During each visit, subjects performed a total of nine fit tests using three samples of the same FFR model. Inward leakage and filter penetration were measured for each donned respirator to determine face seal leakage (FSL). A total of 195 subjects completed the second visit and 134 subjects completed all seven visits. Acceptable fit was defined as 90th percentile FSL ≤ 5% and at least one fit factor ≥ 100. An unacceptable fit was observed for 14, 10, 7, 12, 15, and 16% of subjects on Visits 2-7, respectively. The predicted risk of an unacceptable fit increased with increasing length of time between fit tests, from 10% at Year 1 to 20% at Year 2 and to 25% at Year 3. Twenty-four percent of subjects who lost ≥ 20 lb had an unacceptable fit; these percentages ranged from 7-17% for subjects with lower weight losses or any degree of weight gain. Results support the current OSHA requirement for annual fit testing and suggest that respirator users who lose more than 20 lb should be re-tested for respirator fit.