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Background The potential harmful effects of particle-contaminated infusions for critically ill adult patients are yet unclear. So far, only significant improved outcome in critically ill children and new-borns was demonstrated when using in-line filters, but for adult patients, evidence is still missing. Methods This single-centre, retrospective controlled cohort study assessed the effect of in-line filtration of intravenous fluids with finer 0.2 or 1.2 μm vs 5.0 μm filters in critically ill adult patients. From a total of n  = 3215 adult patients, n  = 3012 patients were selected by propensity score matching (adjusting for sex, age, and surgery group) and assigned to either a fine filter cohort (with 0.2/1.2 μm filters, n  = 1506, time period from February 2013 to January 2014) or a control filter cohort (with 5.0 μm filters, n  = 1506, time period from April 2014 to March 2015). The cohorts were compared regarding the occurrence of severe vasoplegia, organ dysfunctions (lung, kidney, and brain), inflammation, in-hospital complications (myocardial infarction, ischemic stroke, pneumonia, and sepsis), in-hospital mortality, and length of ICU and hospital stay. Results Comparing fine filter vs control filter cohort, respiratory dysfunction (Horowitz index 206 (119–290) vs 191 (104.75–280); P  = 0.04), pneumonia (11.4% vs 14.4%; P  = 0.02), sepsis (9.6% vs 12.2%; P  = 0.03), interleukin-6 (471.5 (258.8–1062.8) ng/l vs 540.5 (284.5–1147.5) ng/l; P  = 0.01), and length of ICU (1.2 (0.6–4.9) vs 1.7 (0.8–6.9) days; P  <  0.01) and hospital stay (14.0 (9.2–22.2) vs 14.8 (10.0–26.8) days; P  = 0.01) were reduced. Rate of severe vasoplegia (21.0% vs 19.6%; P  > 0.20) and acute kidney injury (11.8% vs 13.7%; P  = 0.11) was not significantly different between the cohorts. Conclusions In-line filtration with finer 0.2 and 1.2 μm filters may be associated with less organ dysfunction and less inflammation in critically ill adult patients. Trial registration The study was registered at ClinicalTrials.gov (number: NCT02281604 ).

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  μ m) 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  μ m. Compared with cloth masks, disposable surgical masks are more effective in reducing particulate exposure.

The ongoing worldwide outbreak of COVID-19 has set personal protective equipment in the spotlight. A significant number of countries impose the use of facemasks in public spaces and encourage it in the private sphere. Even in countries where relatively high vaccination rates are achieved at present, breakthrough infections have been frequently reported and usage of facemasks in certain settings has been recommended again. Alternative solutions, including community masks fabricated using various materials, such as cotton or jersey, have emerged alongside facemasks following long-established standards (e.g., EN 149, EN 14683). In the present work, we present a computational model to calculate the ability of different types of facemasks to reduce the exposure to virus-laden respiratory particles, with a focus on the relative importance of the filtration properties and the fitting on the wearer’s face. The model considers the facemask and the associated leakage, the transport of respiratory particles and their accumulation around the emitter, as well as the fraction of the inhaled particles deposited in the respiratory system. Different levels of leakages are considered to represent the diversity of fittings likely to be found among a population of non-trained users. The leakage prevails over the filtration performance of a facemask in determining the exposure level, and the ability of a face protection to limit leakages needs to be taken into account to accurately estimate the provided protection. Filtering facepieces (FFP) provide a better protection efficiency than surgical and community masks due to their higher filtration efficiency and their ability to provide a better fit and thus reduce the leakages. However, an improperly-fitted FFP mask loses a critical fraction of its protection efficiency, which may drop below the protection level provided by properly-worn surgical and community masks.

Based on the current knowledge of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) transmission, wearing a mask has been recommended during the COVID-19 pandemic. Bacterial filtration efficiency (BFE) measurements enable designing and regulating medical masks to prevent bioaerosol dissemination; however, despite the simplicity of these measurements, several scientific questions remain unanswered regarding BFE tests. Here, we investigated (1) the impact of substituting 100-mm Petri dishes with 90-mm disposable Petri dishes, (2) the impact of colony-counting methods on the bioaerosol aerodynamic size, and (3) the impact of colony-counting methods on the total viable particle counts. We demonstrated that disposable 90-mm Petri dishes can be used to replace the 100-mm dishes. We also showed that an automatic high-resolution colony counter can be used to directly count viable particles on collection substrates and to measure the bioaerosol size parameters. Our results enable possible modernization of the outdated testing methods recommended in the US and European standards for BFE measurements. Specifically, use of a modernized colony counter should be clearly regulated and permitted to avoid the counting of positive holes. The median aerodynamic diameter appears to be the most relevant parameter for characterizing bioaerosol size.

This report describes the current state of flattening filter‐free (FFF) radiotherapy beams implemented on conventional linear accelerators, and is aimed primarily at practicing medical physicists. The Therapy Emerging Technology Assessment Work Group of the American Association of Physicists in Medicine (AAPM) formed a writing group to assess FFF technology. The published literature on FFF technology was reviewed, along with technical specifications provided by vendors. Based on this information, supplemented by the clinical experience of the group members, consensus guidelines and recommendations for implementation of FFF technology were developed. Areas in need of further investigation were identified. Removing the flattening filter increases beam intensity, especially near the central axis. Increased intensity reduces treatment time, especially for high‐dose stereotactic radiotherapy/radiosurgery (SRT/SRS). Furthermore, removing the flattening filter reduces out‐of‐field dose and improves beam modeling accuracy. FFF beams are advantageous for small field (e.g., SRS) treatments and are appropriate for intensity‐modulated radiotherapy (IMRT). For conventional 3D radiotherapy of large targets, FFF beams may be disadvantageous compared to flattened beams because of the heterogeneity of FFF beam across the target (unless modulation is employed). For any application, the nonflat beam characteristics and substantially higher dose rates require consideration during the commissioning and quality assurance processes relative to flattened beams, and the appropriate clinical use of the technology needs to be identified. Consideration also needs to be given to these unique characteristics when undertaking facility planning. Several areas still warrant further research and development. Recommendations pertinent to FFF technology, including acceptance testing, commissioning, quality assurance, radiation safety, and facility planning, are presented. Examples of clinical applications are provided. Several of the areas in which future research and development are needed are also indicated. PACS number: 87.53.‐j, 87.53.Bn, 87.53.Ly, 87.55.‐x, 87.55.N‐, 87.56.bc

The Coronavirus Disease 2019 (COVID-19) has swept the whole world with high mortality. Since droplet transmission is the main route of transmission, wearing a mask serves as a crucial preventive measure. However, the virus has spread quite quickly, causing severe mask shortage. Finding alternative materials for homemade masks while ensuring the significant performance indicators will help alleviate the shortage of masks. Referring to the national standard for the \"Surgical Mask\" of China, 17 materials to be selected for homemade masks were tested in four key indicators: pressure difference, particle filtration efficiency, bacterial filtration efficiency and resistance to surface wetting. Eleven single-layer materials met the standard of pressure difference (≤49 Pa), of which 3 met the standard of resistance to surface wetting (≥3), 1 met the standard of particle filtration efficiency (≥30%), but none met the standard of bacterial filtration efficiency (≥95%). Based on the testing results of single-layer materials, fifteen combinations of paired materials were tested. The results showed that three double-layer materials including double-layer medical non-woven fabric, medical non-woven fabric plus non-woven shopping bag, and medical non-woven fabric plus granular tea towel could meet all the standards of pressure difference, particle filtration efficiency, and resistance to surface wetting, and were close to the standard of the bacterial filtration efficiency. In conclusion, if resources are severely lacking and medical masks cannot be obtained, homemade masks using available materials, based on the results of this study, can minimize the chance of infection to the maximum extent.

ABSTRACT Objectives: to assess the effectiveness of filters in filtering particulate matter. Methods: a systematic literature review was conducted with the research question: which filters efficiently adsorb chemical and/or biological particles present in the air when tested in scientific interventions? The databases used were Medical Literature Analysis and Retrieval System Online, Web of Science, Scopus, Latin American and Caribbean Literature in Health Sciences, American Chemical Society, Royal Society Chemistry, Sci Finder, and Scientific Electronic Library Online. Results: forty-seven studies were included in this review. The High Efficiency Particulate Arrestance filter was tested in 36 studies. The seven studies used for the meta-analysis were homogeneous. Conclusions: filtration performed using the High Efficiency Particulate Arrestance filter reduced particulate matter concentrations by 70% to 80% in the assessments and interventions presented, contributing to the evidence that this filter reduces particulate matter concentrations. RESUMEN Objetivos: evaluar la eficacia de los filtros para filtrar material particulado. Métodos: se realizó una revisión sistemática de la literatura con la pregunta de investigación: ¿Qué filtros adsorben eficientemente partículas químicas y/o biológicas presentes en el aire al ser probados en intervenciones científicas? Las bases de datos utilizadas fueron Medical Literature Analysis and Retrieval System Online, Web of Science, Scopus, Literatura Latinoamericana y del Caribe en Ciencias de la Salud, American Chemical Society, Royal Society Chemistry, Sci Finder y Scientific Electronic Library Online. Resultados: se incluyeron 47 estudios en esta revisión. El filtro de alta eficiencia para la retención de partículas se probó en 36 estudios. Los siete estudios utilizados para el metanálisis fueron homogéneos. Conclusiones: la filtración con el filtro de alta eficiencia para la retención de partículas redujo las concentraciones de material particulado entre un 70% y un 80% en las evaluaciones e intervenciones presentadas, lo que refuerza la evidencia de que este filtro reduce las concentraciones de material particulado. RESUMO Objetivos: avaliar a efetividade dos filtros na filtração de material particulado. Métodos: revisão sistemática da literatura com a pergunta de pesquisa: quais filtros adsorvem partículas químicas e/ou biológicas presentes no ar de forma eficiente quando testados em intervenções científicas? As bases de dados utilizadas foram Medical Literature Analysis and Retrieval System Online, Web of Science, Scopus, Literatura Latino-Americana e do Caribe em Ciências da Saúde, American Chemical Society, Royal Society Chemistry, Sci Finder e Scientific Eletronic Library Online. Resultados: foram incluídos nesta revisão 47 estudos. O filtro High Efficiency Particulate Arrestance foi testado em 36 estudos. Os sete estudos utilizados para realização da metanálise foram homogêneos. Conclusões: a filtração realizada com o uso do filtro High Efficiency Particulate Arrestance reduziu concentrações de material particulado em 70% a 80% nas avaliações e intervenções apresentadas, contribuindo para evidências que esse filtro reduz as concentrações de material particulado.

Household water purifiers are increasingly used to treat drinking water at the household level, but their influence on the microbiological safety of drinking water has rarely been assessed. In this study, representative purifiers, based on different filtering processes, were analyzed for their impact on effluent water quality. The results showed that purifiers reduced chemical qualities such as turbidity and free chlorine. However, a high level of bacteria (102–106 CFU/g) was detected at each stage of filtration using a traditional culture-dependent method, whereas quantitative PCR with propidium monoazide (PMA) treatment showed 106–108 copies/L of total viable bacteria in effluent water, indicating elevated microbial contaminants after purifiers. In addition, high-throughput sequencing revealed a diverse microbial community in effluents and membranes. Proteobacteria (22.06–97.42%) was the dominant phylum found in all samples, except for purifier B, in which Melainabacteria was most abundant (65.79%). For waterborne pathogens, Escherichia coli (100–106 copies/g) and Pseudomonas aeruginosa (100–105 copies/g) were frequently detected by qPCR. Sequencing also demonstrated the presence of E. coli (0–6.26%), Mycobacterium mucogenicum (0.01–3.46%), and P. aeruginosa (0–0.16%) in purifiers. These finding suggest that water from commonly used household purifiers still impose microbial risks to human health.

A variety of filters assays have been described to enrich circulating tumor cells (CTC) based on differences in physical characteristics of blood cells and CTC. In this study we evaluate different filter types to derive the properties of the ideal filter for CTC enrichment. Between 0.1 and 10 mL of whole blood spiked with cells from tumor cell lines were passed through silicon nitride microsieves, polymer track-etched filters and metal TEM grids with various pore sizes. The recovery and size of 9 different culture cell lines was determined and compared to the size of EpCAM+CK+CD45-DNA+ CTC from patients with metastatic breast, colorectal and prostate cancer. The 8 µm track-etched filter and the 5 µm microsieve had the best performance on MDA-231, PC3-9 and SKBR-3 cells, enriching >80% of cells from whole blood. TEM grids had poor recovery of ∼25%. Median diameter of cell lines ranged from 10.9-19.0 µm, compared to 13.1, 10.7, and 11.0 µm for breast, prostate and colorectal CTC, respectively. The 11.4 µm COLO-320 cell line had the lowest recovery of 17%. The ideal filter for CTC enrichment is constructed of a stiff, flat material, is inert to blood cells, has at least 100,000 regularly spaced 5 µm pores for 1 ml of blood with a ≤10% porosity. While cell size is an important factor in determining recovery, other factors must be involved as well. To evaluate a filtration procedure, cell lines with a median size of 11-13 µm should be used to challenge the system.

To evaluate (1) the relationship between heating, ventilation, and air conditioning (HVAC) systems and bioaerosol concentrations in hospital rooms, and (2) the effectiveness of laminar air flow (LAF) and high efficiency particulate air (HEPA) according to the indoor bioaerosol concentrations. Databases of Embase, PubMed, Cochrane Library, MEDLINE, and Web of Science were searched from 1st January 2000 to 31st December 2020. Two reviewers independently extracted data and assessed the quality of the studies. The samples obtained from different areas of hospitals were grouped and described statistically. Furthermore, the meta-analysis of LAF and HEPA were performed using random-effects models. The methodological quality of the studies included in the meta-analysis was assessed using the checklist recommended by the Agency for Healthcare Research and Quality. The mean CFU/m3 of the conventional HVAC rooms and enhanced HVAC rooms was lower than that of rooms without HVAC systems. Furthermore, the use of the HEPA filter reduced bacteria by 113.13 (95% CI: -197.89, -28.38) CFU/m3 and fungi by 6.53 (95% CI: -10.50, -2.55) CFU/m3. Meanwhile, the indoor bacterial concentration of LAF systems decreased by 40.05 (95% CI: -55.52, -24.58) CFU/m3 compared to that of conventional HVAC systems. The HVAC systems in hospitals can effectively remove bioaerosols. Further, the use of HEPA filters is an effective option for areas that are under-ventilated and require additional protection. However, other components of the LAF system other than the HEPA filter are not conducive to removing airborne bacteria and fungi. Although our study analysed the overall trend of indoor bioaerosols, the conclusions cannot be extrapolated to rare, hard-to-culture, and highly pathogenic species, as well as species complexes. These species require specific culture conditions or different sampling requirements. Investigating the effects of HVAC systems on these species via conventional culture counting methods is challenging and further analysis that includes combining molecular identification methods is necessary. Our study was the first meta-analysis to evaluate the effect of HVAC systems on indoor bioaerosols through microbial incubation count. Our study demonstrated that HVAC systems could effectively reduce overall bioaerosol concentrations to maintain better indoor air quality. Moreover, our study provided further evidence that other components of the LAF system other than the HEPA filter are not conducive to removing airborne bacteria and fungi. Our research showed that HEPA filters are more effective at removing bioaerosols in HVAC systems than the current LAF system. Therefore, instead of opting for the more costly LAF system, a filter with a higher filtration rate would be a better choice for indoor environments that require higher air quality; this is valuable for operating room construction and maintenance budget allocation.