Functionalized non-woven surfaces for combating the spread of the COVID-19 pandemic

The worldwide outbreak of SARS-CoV-2 infection has necessitated mandatory use of face masks, personal protective equipment and intake of a healthy diet for immunity boosting. As per WHO's recommendation, continuous use of masks has been proven effective in decreasing the SARS-CoV-2 infection rate. The present study reports on the bacterial filtration efficacy (BFE) of a novel 4-ply functionalized non-woven face mask. We synthesized a polypropylene-based fabric with inner layers of melt-blown fine fibres coated with polylactic acid and immune-boosting herbal phytochemicals. Experimental studies on the synthesized face mask demonstrated a BFE of greater than 99% against Staphylococcus aureus (a bacterium species frequently found in mammalian respiratory tract). A thorough computational analysis using LibDock algorithm demonstrated an effective docking performance of herbal phytochemicals against harmful virus structures. More importantly, the face mask also showed sufficient and stable breathability as per regulatory standards. A breathing resistance of 30 Pa at an aerosol flow rate of 30 l h −1 was reported under standard temperature and pressure conditions, indicating a high potential for real-world applications.

Effect of Wearing Surgical Face Masks During Exercise: Does Intensity Matter?

Face masks are widely recommended as means of controlling the coronavirus disease outbreak. This study aimed to examine the physiological and perceptual responses of wearing surgical face masks while exercising at different intensities. Thirteen healthy young adults (mean age, 21.9 ± 1.4 years) conducted randomized crossover trials with or without a surgical face mask. In each trial, participants completed an incremental treadmill protocol, with three 6-min stages (light, moderate, and vigorous at 25, 50, and 75% maximal oxygen uptake, respectively). Physiological outcomes (heart rate, blood lactate, and oxygen saturation level), perceived exertion and discomfort feeling were assessed. No significant differences were observed in physiological outcomes with or without masks at different exercise intensities (p > 0.05). However, the rating of perceived exertion (RPE) was significantly higher when exercising vigorously (mask: 15.5 ± 1.5 vs. no-mask: 14.2 ± 2.1, p < 0.05). Participants wearing masks reported marked discomfort, such as feeling hot, humid, and breathing resistance. Although face mask-wearing during exercise may not have detrimental effects on major physiological parameters, it can increase perceived exertion level and discomfort when the exercise intensity exceeds a certain threshold. Therefore, healthcare professionals should cautiously evaluate each person’s ability to exercise while wearing a mask and tailor their prescription accordingly.

CONDITIONED REFLEX MECHANISMS OF ADAPTATION TO ADDITIONAL BREATHING RESISTANCE

The problem of adaptation to additional breathing resistance has recently become more urgent due to the growth of bronchopulmonary diseases. Therefore, there is a natural interest in non-drug strategies compensating resistive breathing in humans. The aim of the study was to assess conditioned reflex changes in the functional state of the subjects under additional breathing resistance. Materials and Methods. The work was carried out on 55 practically healthy subjects of both sexes, aged 18–36. Additional breathing resistance was modeled by inspiratory resistive loads of 40, 60, 70, and 80 % of the maximum intraoral pressure. The conditioned respiratory reflex to resistive respiratory load was developed as a short-delayed conditioned signal with a 30-second period of isolated action. The authors examined behavioral, vegetative, gas and energy indicators of the organism before and after the formation of a conditioned reflex. Results. It was observed that conditioned reflex shifts of physiological parameters in the process of adaptation to additional breathing resistance differ significantly from the corresponding unconditioned reflex changes both in nature and in intensity. Conditioned reflex mechanisms reduce the intensity of shifts in the motor component of the external respiration system, which, apparently, is the main reason to decrease the aversive behavior. Conclusion. Behavioral changes after the formation of a conditioned respiratory reflex to additional respiratory resistance are characterized by a decrease in aversive behavior patterns. The conditioned reflex realization of increasing resistive loads is expressed in a lower physiological cost of adaptation to additional respiratory resistance relative to the unconditioned reflex type of realization. Keywords: adaptation, conditioned respiratory reflex, additional breathing resistance. Проблема приспособления к дополнительному респираторному сопротивлению в последнее время становится все более актуальной в связи с ростом бронхолегочных заболеваний. Поэтому естественен интерес к нелекарственным механизмам компенсации резистивного дыхания человека. Целью исследования являлась оценка условно-рефлекторных изменений функционального состояния испытуемых в условиях дополнительного респираторного сопротивления. Материалы и методы. Работа проведена на 55 практически здоровых испытуемых обоего пола в возрасте от 18 до 36 лет. Дополнительное респираторное сопротивление моделировалось инспираторными резистивными нагрузками величиной 40, 60, 70 и 80 % от максимального внутриротового давления. Условный дыхательный рефлекс на резистивные дыхательные нагрузки вырабатывался по типу короткоотставленного с периодом изолированного действия условного сигнала 30 с. Исследовались поведенческие, вегетативные, газовые и энергетические показатели организма до и после формирования условного рефлекса. Результаты. Показано, что условно-рефлекторные сдвиги физиологических показателей в процессе приспособления к дополнительному респираторному сопротивлению существенно отличаются от соответствующих безусловно-рефлекторных изменений как по характеру, так и по интенсивности. Условно-рефлекторные механизмы уменьшают интенсивность сдвигов моторного компонента системы внешнего дыхания, что, по-видимому, является основной причиной снижения вероятности появления аверсивного поведения. Выводы. Поведенческие изменения после формирования условного дыхательного рефлекса на дополнительное респираторное сопротивление характеризуются снижением вероятности появления аверсивных форм поведения. Условно-рефлекторная реализация возрастающих по интенсивности резистивных нагрузок выражается в меньшей физиологической стоимости приспособления к дополнительному респираторному сопротивлению относительно безусловно-рефлекторного типа реализации. Ключевые слова: приспособление, условный дыхательный рефлекс, дополнительное респираторное сопротивление.

Research of Operational Properties of Household Fabrics for Production of Protective Masks

Experimental studies have been conducted to determine the operational properties of fabrics used for the manufacture of protective masks. For the experimental study, 22 different fabrics were used, which are available in everyday life. Determination of the operational properties was carried out according to three indicators: the penetration coefficient of the test aerosol, paraffin oil (filtering property), breathing resistance (ergonomic property), resistance to dusting (protective action period) in accordance with the requirements of DSTU EN 149-2017 standard. According to the results of the experimental study to determine the operational properties of fabrics: breathing resistance, penetration coefficient and resistance to dust, it was found that out of the twenty-two samples tested, only eight can be used for the manufacture of protective masks, since their characteristics are able to provide a sufficient level of protection from minimal physiological impact on human (wool, two-thread cloth, velor, tricotin, jersey, frieze and satin). Theoretical calculation of the operational properties of protective masks, which can be made of these fabrics, based on experimental data allowed to make their compliance with the first class of protection according to the requirements of DSTU EN 149-2017. The scientific novelty is to clarify the relationship between the operational properties of fabrics and the operational properties of protective masks.

Evaluation of filtration effectiveness of various types of facemasks following with different sterilization methods

Due to the ongoing pandemic, various types of facemasks such as certified N-95, non-woven fiber and fabric/textile masks are being used as an essential protective measure to reduce the risk of spread of the SARS-Cov-2 virus. The aerosols size-dependent filtration efficiency and breathing resistance of these masks were tested before and after sterilization by five different methods for two flow rates (20 and 90 L/min) conditions corresponding to regular breathing rate and moderate/strenuous exertion, in the particle size range 0.3–10 µm. Sterilization techniques used here are autoclaving (30 and 60 minutes), dry air oven heating (30 and 60 minutes), ionizing irradiation (15 and 25 kGy), hot water washing with and without detergent and immersing in a 10% concentration of liquid hydrogen peroxide for 30 minutes. Further, the filtration efficiency of each type of masks is also studied with laboratory generated two-order higher aerosol concertation. The certified mask has the most outstanding filtering efficiency among all the other type of facemasks. The ionizing radiation causes a significant reduction in filtration efficacy, so that it is not recommended for sterilization purpose. The best method to sterilize certified N-95 masks without affecting their performance is by using dry air heating with temperature ranging from 70–80 °C. The performance of the cloth and surgical masks is found to be comparable for both flow conditions. As an affordable sterilization method, hot water washing is recommended, which does not deteriorate the fabric masks efficiency and can be used by the common people. The recommended masks for the general people are textile/fabric masks which serves fit for the purpose than non-woven masks because it can help to reduce non-biodegradable waste (facemask) and prevent respiratory droplet transmission. The non-woven mask can be sterilized with dry heat, hot water wash and autoclave.

Assessment of N95 respirator for reuse after sterilization: filtration efficacy, breathing resistance, quality factor, chemical structure and surface charge density

In the present ongoing pandemic, the N95 respirator is an essential protective barrier to suppress the spread of the SARS-Cov-2 virus and protect the frontline worker from exposure. The N95 respirators are meant for single usage; however, they can be used after decontamination in-light of the economy and shortfall in availability. At this juncture, the respirators performance after various types of sterilization and usage condition is required to be analyzed in detail. With this motto, this work has proceeded. The filtration efficiency, pressure drop, and quality factor of the respirator are evaluated for two face velocities (5.8 and 26.4 cm/s) following different sterilization methods. Sterilization techniques used here are dry air oven heating, gamma irradiation, and immersing in a 10% concentration of liquid hydrogen peroxide. The particle filtration performance and electrostatic surface charge density measurement are used to determine the facemasks efficacy after sterilization. The methods recommended to sterilize N95 masks without affecting their performance are (i) using dry air heat at 80oC and (ii) H2O2 soaking. The highest reduction in filtration efficiency is observed to be 30-35% after gamma irradiation due to a change in the electrostatic properties of the respirator layers. However, the filtration efficiency does not change significantly for other sterilization methods despite a change in charge density, but there is no direct correlation with filtration efficiency. Electrostatic charge measurement of the filtration layer is a crucial indicator of filtration efficiency degradation. Policymakers can use these data during potential future N95 shortage to assess the viability of sterilization methods.

Screening of core filter layer for the development of respiratory mask to combat COVID-19

The severe outbreak of respiratory coronavirus disease 2019 has increased the significant demand of respiratory mask and its use become ubiquitous worldwide to control this unprecedented respiratory pandemic. The performance of a respiratory mask depends on the efficiency of the filter layer which is mostly made of polypropylene melt blown non-woven (PP-MB-NW). So far, very limited characterization data are available for the PPE-MB-NW in terms to achieve desired particulate filtration efficiency (PFE) against 0.3 µm size, which are imperative in order to facilitate the right selection of PP-MB-NW fabric for the development of mask. In present study, eight different kinds of PP-MB-NW fabrics (Sample A–H) of varied structural morphology are chosen. The different PP-MB-NW were characterized for its pore size and distribution by mercury porosimeter and BET surface area analyzer was explored first time to understand the importance of blind pore in PFE. The PP-MB-NW samples were characterized using scanning electron microscopy so as to know the surface morphology. The filtration efficiency, pressure drop and breathing resistance of various PP-MB-NW fabric samples are investigated in single and double layers combination against the particle size of 0.3, 0.5 and 1 µm. The samples which are having low pore dia, high solid fraction volume, and low air permeability has high filtration efficiency (> 90%) against 0.3 µm particle with high pressure drop (16.3–21.3 mm WC) and breathing resistance (1.42–1.92 mbar) when compared to rest of the samples. This study will pave the way for the judicial selection of right kind of filter layer i.e., PP-MB-NW fabric for the development of mask and it will be greatly helpful in manufacturing of mask in this present pandemic with desired PFE indicating considerable promise for defense against respiratory pandemic.

Size-Dependent Filtration Efficiency of Alternative Facemask Filter Materials

The use of facemasks is proven to mitigate the spread of the coronavirus and other biological agents that cause disease. Various forms of facemasks, made using different materials, are being used extensively, and it is important to determine their performance characteristics. The size-dependent filtration efficiency and breathing resistance of household sterilization wrap fabrics, and isolation media (American Society for Testing and Materials (ASTM)- and non-ASTM-rated), were measured in filter-holder- and mannequin-in-chamber-based systems, focusing on particles sizes between 20 nm and 2 μm. Double-layer MERV-14 (Minimum Efficiency Reporting Values with rating 14) showed the highest filtration efficiency (94.9–73.3%) amongst household filter media, whereas ASTM-rated isolation masks showed the highest filtration efficiencies (95.6–88.7) amongst all the masks considered. Filtration efficiency of 3D-printed masks with replaceable filter media was found to depend on the degree of sealing around the media holder, which depended on the material’s compressibility. Filtration efficiencies of triple-layer combinations (95.8–85.3%) follow a profile similar to single layers but with improved filtration efficiencies.

Antimicrobial Nanofiber Based Filters for High Filtration Efficiency Respirators

Electrospinning has been used to develop and upscale polyacrylonitrile (PAN) nanofibers as effective aerosol filtration materials for their potential use in respirators. The fibers were deposited onto non-woven spunbond polypropylene (SPP) and the basis weight (grammage, g/m2) was varied to assess the resulting effect on filtration efficiency and breathing resistance of the materials. The results indicated that a basis weight in excess of 0.4 g/m2 of PAN electrospun fibers yielded a filtration efficiency over 97%, with breathing resistance values that increased proportionally with the amount of basis weight added. With the aim of retaining filter efficiency whilst lowering breathing resistance, the basis weight of 0.4 g/m2 and 0.8 g/m2 of PAN electrospun fibers were strategically split up and stacked with SPP in different configurations. The results suggested that a symmetric structure based on SPP/PAN/PAN/SPP was the optimal structure, as it reduces SPP consumption while maintaining an FFP2-type of filtration efficiency, while reducing breathing resistance, specially at high air flow rates, such as those mimicking FFP2 exhalation conditions. The incorporation of zinc oxide (ZnO) nanoparticles within the electrospun nanofibers in the form of nanocomposites, retained the high filtration characteristics of the unfilled filter, while exhibiting a strong bactericidal capacity, even after short contact times. This study demonstrates the potential of using the symmetric splitting of the PAN nanofibers layer as a somewhat more efficient configuration in the design of filters for respirators.