Proper adherence to infection control precautions, including appropriate selection and use of personal protective equipment (PPE), is of significant importance to the health and well-being of perioperative personnel. Surgical masks are intended for use as a barrier to protect the wearer’s face from large droplets and splashes of blood and other body fluids; however, surgical and high-filtration surgical laser masks do not provide enough protection to be considered respiratory PPE. Potential exposure to airborne contaminants and infectious agents, including those present in surgical smoke, necessitates the use of respiratory PPE, such as a surgical N95 particulate filtering facepiece respirator. Filtering facepiece respirators greatly reduce a wide size range of particles from entering the wearer’s breathing zone and are designed to protect the user from both droplet and airborne particles. Every health care worker who must use a respirator to control hazardous exposures in the workplace must be trained to properly use the respirator and pass a fit test before using it in the workplace.
When a plaid object is presented, the visual system decomposes it into its constituting orientation primitives and integrates them at later processing stages. The present study reveals the time course of this process by applying meta- and paracontrast masking to both simple oriented and plaid gratings. With various stimulus onset asynchronies (SOA) between target gratings and surrounding mask annuli, subjects were asked to identify whether targets were simple gratings collinear to the masks, orthogonal to the masks, plaid, or whether no target was presented. The resulting time courses for each type of stimulus confusion showed that metacontrast peaked when orientation primitives had already begun to be integrated into one object, indicated by a dominance of “no target” responses given to plaid stimuli at SOAs around 70 ms. At SOAs around 10 to 30 ms masking also had a significant impact but acted on separable components, indicated by a dominance of “orthogonal” responses given plaid stimuli. Probability summation of “no target” responses given simple gratings revealed that only at shorter SOAs performance for plaid stimuli could be predicted assuming independent features but not at SOAs of at 50-70 ms. We discuss in how far these results could also be explained by the dynamics of cross-orientation suppression (COS) and how they might relate to the process of feature integration in plaids.
Fibroglandular tissue may mask breast cancers, thereby reducing the sensitivity of mammography. Here, we investigate methods for identification of women at high risk of a masked tumor, who could benefit from additional imaging.
BACKGROUND: Most surgical masks are not certified for use as respiratory protective devices (RPDs). In the event of an influenza pandemic, logistical and practical implications such as storage and fit testing will restrict the use of RPDs to certain high-risk procedures that are likely to generate large amounts of infectious bioaerosols. Studies have shown that in such circumstances increased numbers of surgical masks are worn, but the protection afforded to the wearer by a surgical mask against infectious aerosols is not well understood. AIM: To develop and apply a method for assessing the protection afforded by surgical masks against a bioaerosol challenge. METHODS: A dummy test head attached to a breathing simulator was used to test the performance of surgical masks against a viral challenge. Several designs of surgical masks commonly used in the UK healthcare sector were evaluated by measuring levels of inert particles and live aerosolised influenza virus in the air, from in front of and behind each mask. FINDINGS: Live influenza virus was measurable from the air behind all surgical masks tested. The data indicate that a surgical mask will reduce exposure to aerosolised infectious influenza virus; reductions ranged from 1.1- to 55-fold (average 6-fold), depending on the design of the mask. CONCLUSION: We describe a workable method to evaluate the protective efficacy of surgical masks and RPDs against a relevant aerosolised biological challenge. The results demonstrated limitations of surgical masks in this context, although they are to some extent protective.
Respiratory protective masks are used whenever it is too costly or impractical to remove airborne contamination from the atmosphere. Respirators are used in a wide range of occupations, form the military to medicine. Respirators have been found to interfere with many physiological and psychological aspects of task performance at levels from resting to maximum exertion. Many of these limitations have been investigated in order to determine quantitatively how much performance decrement can be expected from different levels of respirator properties. The entire system, including respirator and wearer interactions, must be considered when evaluating wearer performances. This information can help respirator designers to determine trade-offs or managers to plan to compensate for reduced productivity of wearers.
- Journal of exposure science & environmental epidemiology
- Published over 4 years ago
Inexpensive cloth masks are widely used in developing countries to protect from particulate pollution albeit limited data on their efficacy exists. This study examined the efficiency of four types of masks (three types of cloth masks and one type of surgical mask) commonly worn in the developing world. Five monodispersed aerosol sphere size (30, 100, and 500 nm, and 1 and 2.5 μm) and diluted whole diesel exhaust was used to assess facemask performance. Among the three cloth mask types, a cloth mask with an exhaust valve performed best with filtration efficiency of 80-90% for the measured polystyrene latex (PSL) particle sizes. Two styles of commercially available fabric masks were the least effective with a filtration efficiency of 39-65% for PSL particles, and they performed better as the particle size increased. When the cloth masks were tested against lab-generated whole diesel particles, the filtration efficiency for three particle sizes (30, 100, and 500 nm) ranged from 15% to 57%. Standard N95 mask performance was used as a control to compare the results with cloth masks, and our results suggest that cloth masks are only marginally beneficial in protecting individuals from particles<2.5 μm. Compared with cloth masks, disposable surgical masks are more effective in reducing particulate exposure.Journal of Exposure Science and Environmental Epidemiology advance online publication, 17 August 2016; doi:10.1038/jes.2016.42.
BACKGROUND: Although the wearing of face masks in public has not been recommended for preventing influenza, these devices are often worn in many Asian countries during the influenza season. In Japan, it is thought that such behavior may be an indicator of other positive hygiene practices. The aim of this study, therefore, was to determine if wearing a face mask in public is associated with other positive hygiene practices and health behaviors among Japanese adults. METHODS: We initially recruited around 3,000 Japanese individuals ranging from 20 to 69 years of age who were registered with a web survey company. Participants were asked to recall their personal hygiene practices during the influenza season of the previous year. Logistic regression analysis was then used to examine the associations between wearing a face mask in public and personal hygiene practices and health behaviors. RESULTS: A total of 3,129 persons responded to the survey, among whom 38% reported that they had worn a face mask in public during the previous influenza season. Wearing a face mask in public was associated with various self-reported hygiene practices including: frequent hand washing (adjusted Odds Ratio [OR]: 1.67; 95% Confidence Interval [95%CI]: 1.34-1.96), occasional hand washing (OR: 1.43; 95%CI: 1.10-1.75), frequently avoiding crowds (OR: 1.85; 95%CI: 1.70-1.98), occasionally avoiding crowds (OR: 1.65; 95%CI: 1.53-1.76), frequent gargling (OR: 1.68; 95%CI: 1.51-1.84), occasional gargling (OR: 1.46; 95%CI: 1.29-1.62), regularly avoiding close contact with an infected person (OR: 1.50; 95%CI: 1.33-1.67), occasionally avoiding close contact with an infected person (OR: 1.31; 95%CI: 1.16-1.46), and being vaccinated of influenza in the last season (OR: 1.31; 95%CI: 1.17-1.45). CONCLUSIONS: Overall, this study suggests that wearing a face mask in public may be associated with other personal hygiene practices and health behaviors among Japanese adults. Rather than preventing influenza itself, face mask use might instead be a marker of additional, positive hygiene practices and other favorable health behaviors in the same individuals.
ABSTRACT Respiratory protection provided by a particulate respirator is a function of particle penetration through filter media and through faceseal leakage. Faceseal leakage largely contributes to the penetration of particles through respirator and compromises protection. When faceseal leaks arise, filter penetration is assumed to be negligible. The contribution of filter penetration and faceseal leakage to total inward leakage (TIL) of submicron size bioaerosols is not well studied. To address this issue, TIL values for two N95 filtering facepiece respirator (FFR) models and two surgical mask (SM) models sealed to a manikin were measured at 8 L and 40 L breathing minute volumes with different artificial leak sizes. TIL values for different size (20-800 nm, electrical mobility diameter) NaCl particles representing submicron size bioaerosols were measured using a scanning mobility particle sizer. Efficiency of filtering devices was assessed by measuring the penetration against NaCl aerosol similar to the method used for NIOSH particulate filter certification. Results showed that the most penetrating particle size (MPPS) was ∼45 nm for both N95 FFR models and one of the two SM models, and ∼350 nm for the other SM model at sealed condition with no leaks as well as with different leak sizes. TIL values increased with increasing leak sizes and breathing minute volumes. Relatively, higher efficiency N95 and SM models showed lower TIL values. Filter efficiency of FFRs and SMs influenced the TIL at different flow rates and leak sizes. Overall, the data indicate that good fitting higher efficiency FFRs may offer higher protection against submicron size bioaerosols.
For pandemic influenza outbreaks, the Institute of Medicine has recommended using a surgical mask cover (SM) over N95 filtering facepiece respirators (FFRs) among healthcare workers as one strategy to avoid surface contamination of the FFR which would extend its efficacy and reduce the threat of exhausting FFR supplies. The objective of this investigation was to measure breathing air quality and breathing resistance when using FFRs with US Food and Drug Administration-cleared SM and without SM.
A Randomised Clinical Trial of Three Options for N95 Respirators and Medical Masks in Health Workers
- American journal of respiratory and critical care medicine
- Published about 8 years ago
BACKGROUND: We compared three policy options for the use of medical masks and N95 respirators in healthcare workers (HCWs). Design: A cluster randomised clinical trial of 1669 hospital-based HCWs in Beijing, China in the 2009/2010 winter. METHODS: Participants were randomised to: medical masks; N95 respirators; targeted use of N95 respirators while doing high-risk procedures or barrier nursing. Outcomes included clinical respiratory illness (CRI) and laboratory-confirmed respiratory pathogens in symptomatic subjects. Findings: The rate of CRI was highest in the medical mask arm (98/572, 17%), followed by the targeted N95 arm (61/516, 11•8%), and the N95 arm (42/581, 7•2%), P < 0•05. Bacterial respiratory tract colonisation in subjects with CRI was highest in the medical mask arm (14•7%, 84/572), followed by the targeted N95 arm (10•1%, 52/516) and lowest in the N95 arm (6•2%, 36/581), P = 0•02. After adjusting for confounders, only continuous use of N95 remained significant against CRI and bacterial colonisation, and for just CRI compared to targeted N95 use. Targeted N95 use was not superior to medical masks. Interpretation: Continuous use of N95 respirators was more efficacious against CRI than intermittent use of N95, or medical masks. Most policies for HCWs recommend use of medical masks alone, or targeted N95 respirator use. Also continuous use of N95's resulted in significantly lower rates of bacterial colonisation, a novel finding which points out to more research on the clinical significance of bacterial infection in symptomatic HCWs. This study provides further data to inform occupational policy options for HCWs.