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With frequent outbreaks of COVID-19, the rapid and effective construction of large-space buildings into Fangcang shelter hospitals has gradually become one of the effective means to control the epidemic. Reasonable design of the ventilation system of the Fangcang shelter hospital can optimize the indoor airflow organization, so that the internal environment can meet the comfort of patients and at the same time can effectively discharge pollutants, which is particularly important for the establishment of the Fangcang shelter hospital. In this paper, through the reconstruction of a large-space gymnasium, CFD software is used to simulate the living environment and pollutant emission efficiency of the reconstructed Fangcang shelter hospital in summer under different air supply temperatures, air supply heights and exhaust air volume parameters. The results show that when the air supply parameters are set to an air supply height of 4.5 m, an air supply temperature of 18 °C, and an exhaust air volume of a single bed of 150 m3/h, the thermal comfort can reach level I, and the ventilation efficiency for pollutants can reach 69.6%. In addition, the ventilation efficiency is 70.1% and 70.3% when the exhaust air volume of a single bed is continuously increased to 200 and 250 m3/h, which can no longer effectively improve the pollutant emission and will cause an uncomfortable blowing feeling to patients. © 2023 by the authors.
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The respiratory pump that provides pulmonary ventilation includes the respiratory center, peripheral nervous system, chest and respiratory muscles. The aim of this study was to evaluate the activity of the respiratory center and the respiratory muscles strength after COVID-19 (COronaVIrus Disease 2019). Methods. The observational retrospective cross-sectional study included 74 post-COVID-19 patients (56 (76%) men, median age - 48 years). Spirometry, body plethysmography, measurement of lung diffusing capacity (DLCO), maximal inspiratory and expiratory pressures (MIP and MEP), and airway occlusion pressure after 0.1 sec (P0.1) were performed. In addition, dyspnea was assessed in 31 patients using the mMRC scale and muscle strength was assessed in 27 of those patients using MRC Weakness scale. Results. The median time from the COVID-19 onset to pulmonary function tests (PFTs) was 120 days. The total sample was divided into 2 subgroups: 1 - P0.1 <= 0.15 kPa (norm), 2 - > 0.15 kPa. The lung volumes, airway resistance, MIP, and MEP were within normal values in most patients, whereas DLCO was reduced in 59% of cases in both the total sample and the subgroups. Mild dyspnea and a slight decrease in muscle strength were also detected. Statistically significant differences between the subgroups were found in the lung volumes (lower) and airway resistance (higher) in subgroup 2. Correlation analysis revealed moderate negative correlations between P0.1 and ventilation parameters. Conclusion. Measurement of P0.1 is a simple and non-invasive method for assessing pulmonary function. In our study, an increase in P0.1 was detected in 45% of post-COVID-19 cases, possibly due to impaired pulmonary mechanics despite the preserved pulmonary ventilation as well as normal MIP and MEP values.Copyright © Savushkina O.I. et al., 2023.
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Objectives: The effectiveness of prone positioning (PP) under VV-ECMO for severe COVID-19 still be unclear. Until now, PP under VV-ECMO was often performed as the trump card for refractory hypoxemia and weaning off ECMO. On the other hand, PP has the effect of promoting homogenization of Lung aeration and leading to prevention of VILI. Combine use of early prone positioning together VV-ECMO may have synergy effects of ultra-lung protective strategy. In this study, we analyzed early PP cases under VV-ECMO for severe COVID-19 in our hospital and examined their efficacy and feasibility. Method(s): We performed a retrospective study of patients with SARS-CoV-2-induced ARDS submitted to early PP during VV-ECMO. During VVECMO, PP was considered in case of "Type-H transition in imaging findings (CT / LUS) " and cases that the physician deemed necessary. The lung aeration is evaluated by LUS before and after each PP. If there is a finding that the dorsal collapsed lung is improved through PP, it is implemented as effective, and it continued. Result(s): From April 2021 to August 2021, there were a total of 10 early PP cases under ECMO, and the age was (average) 56 years. ECMO was implanted with P/F 98 and Murray score 3.3 points, and PP was started 14 hours after the ECMO implantation. The average PP duration is 17.4 hours and PP performed 5.8 times per patient. Comparing blood gas and respiratory mechanics before and after PP showed a significant difference in PaCO2 (before: 46 +/- 8 vs after: 42 +/- 9, p = 0.02). Finally, there were 10 ECMO successful weaning (100%) and 8 surviving discharges (80%). No major complications were observed. Conclusion(s): Early PP under VV-ECMO for severe COVID-19 can be safely performed, and it is suggested that the synergy effect of ultra-lung protective strategy may be associated with a reduction of hospital mortality.
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Dental services are yet to return to a semblance of normality owing to the fear and uncertainty associated with the possible airborne transmission of diseases. The present study aims to investigate the impacts of environmental conditions [changes in ventilation location, ventilation rate, and relative humidity (RH)] and variations in dental patient's breathing rate on droplet transmission during dental service. Computational fluid dynamics simulation was performed based on our previous experimental study during ultrasonic scaling. The impacts of different factors were numerically analyzed by the final fate and proportion of emitted droplets in the dental surgery environment. The results revealed that about 85% of droplets deposited near the dental treatment region, where the patient's torso, face, and floor (dental chair) accounted for around 63%, 11%, and 8.5%, respectively. The change in the ventilation location had a small impact on the deposition of larger droplets (> 60 mu m), and a spatial region with high droplet mass concentration would be presented near the dental professional. The change in the ventilation rate from 5 to 8 ACH led to a 1.5% increment in the fraction of escaped droplets. 50% RH in dental environments was recommended to prevent droplets' fast evaporation and potential mold. Variations in the patient's breathing rate had little effect on the final fate and proportion of emitted droplets. Overall, environmental factors are suggested to maintain 50% RH and larger ACH in dental surgery environments. The findings can give policymakers insights into the role of environmental factors on infection control.
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Indoor airflow patterns and the spreading of respiratory air were studied using the large-eddy simulation (LES) computational fluid dynamics (CFD) approach. A large model room with mixing ventilation was investigated. The model setup was motivated by super-spreading of the SARS-CoV-2 virus with a particular focus on a known choir practice setup where one singer infected all the other choir members. The room was heated with radiators at two opposite walls in the cold winter time. The singers produced further heat generating buoyancy in the room. The Reynolds number of the inflow air jets was set to Re=2750, corresponding to an air-changes-per-hour (ACH) value of approximately 3.5. The CFD solver was first validated after which a thorough grid convergence study was performed for the full numerical model room with heat sources. The simulations were then executed over a time of t=20 min to account for slightly more than one air change timescale for three model cases: (1) full setup with heat sources (radiators+singers) in the winter scenario, (2) setup without radiators in a summer scenario, and (3) theoretical setup without buoyancy (uniform temperature). The main findings of the paper are as follows. First, the buoyant flow structures were noted to be significant. This was observed by comparing cases 1/2 with case 3. Second, the dispersion of the respiratory aerosol concentration, modeled as a passive scalar, was noted to be significantly affected by the buoyant flow structures in cases 1–2. In particular, the aerosol cloud was noted to either span the whole room (cases 1–2) or accumulate in the vicinity of the infected singer (case 3). Turbulence was clearly promoted by the interaction of the upward/downward moving warmer/cooler air currents which significantly affected the dispersion of the respiratory aerosols in the room. The study highlights the benefits of high-resolution, unsteady airflow modeling (e.g. LES) for interior design which may consequently also impact predictions on exposure to potentially infectious respiratory aerosols.
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Eye discomfort is a major complaint reported in indoor spaces and has been suggested to be exacerbated by environmental conditions such as low humidity and high air velocity. Wearing face masks, which has become essential in our daily lives during the COVID-19 pandemic, can also cause eye discomfort by affecting the microclimate around the eyes. We conducted a pilot study to evaluate the effect of wearing masks on eye discomfort by measuring the physical environment around the eyes and short-term physiological and psychological responses and comparing them with and without surgical face masks. The results showed that when the participant wore a mask, exhaled air flowed out through the gap at the top edge of the mask, resulting in a higher air velocity and absolute humidity around the eyes than when the mask was not worn. No significant differences were found in subjective discomfort, tear-film stability, ocular surface temperature or blink frequency. However, the tear evaporation rate, estimated based on physical measurements, was greater when wearing a mask than when not wearing it. This study revealed that wearing face masks can negatively affect the environment around the eyes in terms of tear-film health.
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Ventilation performance plays a significant role in distributing contaminants and airborne infections indoors. Thus, poorly ventilated public spaces may be at high risk due to the presence of both infectious and susceptible people. Adapting HVAC ventilation systems to mitigate virus transmission requires considering ventilation rate, airflow patterns, air balancing, occupancy, and feature placement. The study aims to identify poorly ventilated spaces where airborne transmission of pathogens such as SARS-CoV-2 could be critical. This study is focused on evaluating the ventilation performance of the building stock and the safety of using the facilities based on measured indoor CO2. The results revealed the spaces with the potential risk of indoor airborne transmission of COVID-19. The study proposes recommendations for utilising air ventilation systems in different use cases. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
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The COVID-19 pandemic has created a new type of waste (surgical mask waste "WMs") that presents a major challenge now and in the future, given the strong possibilities of similar epidemics to reoccur. In order to find an effective industrial solution to the millions of WMs produced daily, this research aims to develop a new eco-friendly strategy to convert WMs into H-2-CH4-rich syngas, carbon nanoparticles (CNPs), and benzene-rich tar using an updraft gasifier system. The experiments started with the preparation of WM granules using shredding followed by granulation processes. Subsequently, the granules were processed in a lab-scale reactor with a capacity of 0.9-1 kg/h and consisted of a continuous WM feed system, a gasifier, a sampling system for syngas and tar, a ceramic filtration unit for separating the CNPs against the synthesis gas, and a burner. The gasification experiments were performed in ambient air with different air-fuel equivalence ratios (ER: 0.21, 0.25, and 0.29) and temperatures (700 degrees C, 800 degrees C, and 900 degrees C) to determine the optimal conditions that yield the maximum amount of H-2-CH4-rich syngas and CNPs with less impurities. The chemical composition and morphology of the obtained gasification products (syngas, tar, and CNPs) were observed using GC-FID, FTIR, and SEM. The results showed that the maximum production of syngas (4.29 +/- 0.16 kg/h with HHV of 3804 kJ/kg) and CNPs (0.14 +/- 0.011 kg/h) accompanied by a moderate tar rate (0.123 +/- 0.009 kg/h with HHV of 41,139.88 kJ/kg) could be obtained at 900 degrees C and ER = 0.29, while the highest H-2 (16.93 +/- 1.7 vol.%) and CH4 (10.44 +/- 0.85 vol.%) contents in syngas product were synthesized at 900 degrees C and ER = 0.19. Benzene and toluene were the major GC-FID compounds in the formulated tar product with abundance up to 25.6% and 11%, respectively. Meanwhile, gasification conditions of 900 degrees C and ER = 0.24 allowed the best morphology to be formulated for spherical-shaped CNPs with a diameter of less than 200 nm.
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Site visits were made to ten (non-healthcare) workplace COVID-19 outbreaks to assess ventilation. Measurements of carbon dioxide (CO2), temperature and humidity were made. Room activity and occupancy was observed, and ventilation management assessed. CO2 readings were used to identify areas of poor air quality, and where possible, airflow measurements were made at ventilation openings and CO2 decay rates were used to estimate ventilation rates. Poorly ventilated, regularly occupied spaces were frequently identified by this work. Measures to reduce transmission risk and improve ventilation included opening windows and reducing room capacities. Attempts at reconfiguration of mechanical ventilation systems were not common. Thermal comfort and heating costs were factors cited that influenced decision making. Overall understanding of ventilation was low and identified a need for simple tools to allow stakeholders to assess their workspaces. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
ABSTRACT
Risk calculators have been utilised to predict the risk of infection from SARS-CoV-2. Inputs include the dimensions of the indoor space, number of infected persons and activity, and inhalation rate of susceptible persons. The compartment model requires an estimate of the Air Changes per Hour (ACH) in the space, as the concentration is changing as a result of the dynamic balance between the generation and removal of exhaled quanta. ACH can be estimated using CO2, engineering drawings, or airflow measurements, but these estimates are often incorrect due to mechanical anomalies and mixing inefficiencies, or in the case of CO2, an absence of continuous occupancy for a sufficient amount of time. SF6 as a tracer gas to establish ACH has been used extensively for many decades to measure air exchange. This approach was utilised to assist a school in managing risk of infection in their facility during an exam period. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
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Purpose of Study In March of 2020, the World Health Organization declared the coronavirus (COVID-19) a global pandemic. As the number of cases increased worldwide, existing hospital infrastructure struggled to keep up with the demand for equipment and supplies.This exposed healthcare workers to contracting the disease. The purpose of this study is to demonstrate an emergency innovation response in overcoming shortages of personal protective equipment within a university hospital setting, with a special focus on powered air purifying respirators (PAPRs). Methods Used The Center for Medical Innovation (CMI)-a center designed to promote research and development of high-impact healthcare products at the University of Utah (UofU)-enlisted university engineers to develop an open source PAPR system made from readily available commercial materials. Parts were selected to meet filtration, airflow, and protection specifications as outlined by industry standards. Commercially available parts consistent with these specifications were assembled into a novel PAPR system which utilized 3D printed pieces on demand to achieve compatibility. Once assembled, each PAPR went through protection testing to demonstrate health worker safety. A fit factor of 200 is the minimum requirement needed as defined by NIOSH. Testing procedures were carried out with industry standard equipment. Summary of Results A human centered design approach was utilized in iterating versions of the product based on repeated fit testing. Failures were addressed in subsequent models. All PAPRs passed fit testing with a score of > 1000. Following the lean processing standard of just in time inventory, materials to fabricate 1000 PAPRs were procured and assembled on demand. PAPRs are now being used by the UofU Hospital as well as other affiliate entities globally and are filling the gap needed for PPE. Approximately 200 units have been donated to Navajo Nations hospitals in the state of Utah and others have been donated to university sister entities in India, Nepal, and Kenya. Conclusions The Center for Medical Innovation at the University of Utah has facilitated a rapid emergency innovative response in filling the PPE needs locally and abroad by creating this open source accessible PAPR system.
ABSTRACT
The respiratory pump that provides pulmonary ventilation includes the respiratory center, peripheral nervous system, chest and respiratory muscles. The aim of this study was to evaluate the activity of the respiratory center and the respiratory muscles strength after COVID-19 (COronaVIrus Disease 2019). Methods. The observational retrospective cross-sectional study included 74 post-COVID-19 patients (56 (76%) men, median age - 48 years). Spirometry, body plethysmography, measurement of lung diffusing capacity (DLCO), maximal inspiratory and expiratory pressures (MIP and MEP), and airway occlusion pressure after 0.1 sec (P0.1) were performed. In addition, dyspnea was assessed in 31 patients using the mMRC scale and muscle strength was assessed in 27 of those patients using MRC Weakness scale. Results. The median time from the COVID-19 onset to pulmonary function tests (PFTs) was 120 days. The total sample was divided into 2 subgroups: 1 - P0.1 <= 0.15 kPa (norm), 2 - > 0.15 kPa. The lung volumes, airway resistance, MIP, and MEP were within normal values in most patients, whereas DLCO was reduced in 59% of cases in both the total sample and the subgroups. Mild dyspnea and a slight decrease in muscle strength were also detected. Statistically significant differences between the subgroups were found in the lung volumes (lower) and airway resistance (higher) in subgroup 2. Correlation analysis revealed moderate negative correlations between P0.1 and ventilation parameters. Conclusion. Measurement of P0.1 is a simple and non-invasive method for assessing pulmonary function. In our study, an increase in P0.1 was detected in 45% of post-COVID-19 cases, possibly due to impaired pulmonary mechanics despite the preserved pulmonary ventilation as well as normal MIP and MEP values.Copyright © Savushkina O.I. et al., 2023.
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Background: Chemoprophylaxis is a critical tool for many infectious diseases, and in COVID-19 may have particular benefit for vulnerable patients that do not maximally benefit from vaccination. Nafamostat inhibits TMPRSS2, which catalyses a critical cell entry pathway for SARS-CoV-2. This study sought to assess efficacy of intranasal nafamostat against airborne transmission of SARSCoV-2 in Syrian Golden hamsters. Method(s): Male hamsters were intranasally administered water or 5 mg/kg nafamostat in water twice daily for 5 days (sentinels). One day after treatment initiation, sentinels were co-housed with an untreated hamster that was intranasally inoculated with 1 x 104 PFU of Wuhan SARS-CoV-2 (donor). Sentinels were separated from the donor by a perforated divider, allowing airflow between zones but not contact. Hamsters were weighed and throat-swabbed throughout. At day 4, all animals were culled, and lung and nasal turbinates were harvested. N-RNA was quantified relative to 18S-RNA by qPCR. A 2-way ANOVA with Bonferroni correction was applied to compare weight changes in the nafamostat group to those in controls. An unpaired t-test was used to compare viral RNA in lung and nasal turbinate between groups. Result(s): SARS-CoV-2 viral RNA was significantly lower in the nasal turbinates of nafamostat-treated hamsters compared to water-treated controls (P = 0.012;Figure 1). Within the lung, SARS-CoV-2 RNA was undetectable in the nafamostat-treated hamsters, but was detectable in the water-treated controls. Viral RNA was undetectable in the swabs of the nafamostat-treated hamsters at all timepoints, but was quantifiable in the water-treated control group from day 3. Body weight of the nafamostat-treated hamsters was significantly lower (P = < 0.001) than in the water-treated animals throughout. SARS-CoV-2 viral RNA was detectable in the donor hamsters lung, nasal turbinate and swab samples confirming validity of the experiment. Conclusion(s): This study demonstrated a protective effect of intranasal nafamostat against airborne SARS-CoV-2 transmission in Syrian golden hamsters. A phase IIa study of intravenously administered nafamostat yielded no evidence of clinical efficacy in hospitalised patients, but further investigation of intranasally administered nafamostat in a prophylactic setting may be warranted.
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Purpose: Ventilation of indoor spaces is required for the delivery of fresh air rich in oxygen and the removal of carbon dioxide, pollutants and other hazardous substances. The COVID-19 pandemic brought the topic of ventilating crowded indoors to the front line of health concerns. This study developed a new biologically inspired concept of biomimetic active ventilation (BAV) for interior environments that mimics the mechanism of human lung ventilation, where internal air is continuously refreshed with the external environment. The purpose of this study is to provide a detailed proof-of-concept of the new BAV paradigm using computational models. Design/methodology/approach: This study developed computational fluid dynamic models of unoccupied rooms with two window openings on one wall and two BAV modules that periodically translate perpendicular to or rotate about the window openings. This study also developed a time-evolving spatial ventilation efficiency metric for exploring the accumulated refreshment of the interior space. The authors conducted two-dimensional (2D) simulations of various BAV configurations to determine the trends in how the working parameters affect the ventilation and to generate initial estimates for the more comprehensive three-dimensional (3D) model. Findings: Simulations of 2D and 3D models of BAV for modules of different shapes and working parameters demonstrated air movements in most of the room with good air exchange between the indoor and outdoor air. This new BAV concept seems to be very efficient and should be further developed. Originality/value: The concept of ventilating interior spaces with periodically moving rigid modules with respect to the window openings is a new BAV paradigm that mimics human respiration. The computational results demonstrated that this new paradigm for interior ventilation is efficient while air velocities are within comfortable limits. © 2023, Emerald Publishing Limited.
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Background: Low temperature is conducive to the survival of COVID-19. Some studies suggest that cold-chain environment may prolong the survival of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and increase the risk of transmission. However, the effect of cold-chain environmental factors and packaging materials on SARS-CoV-2 stability remains unclear. Methods: This study aimed to reveal cold-chain environmental factors that preserve the stability of SARS-CoV-2 and further explore effective disinfection measures for SARS-CoV-2 in the cold-chain environment. The decay rate of SARS-CoV-2 pseudovirus in the cold-chain environment, on various types of packaging material surfaces, i.e., polyethylene plastic, stainless steel, Teflon and cardboard, and in frozen seawater was investigated. The influence of visible light (wavelength 450 nm-780 nm) and airflow on the stability of SARS-CoV-2 pseudovirus at -18°C was subsequently assessed. Results: Experimental data show that SARS-CoV-2 pseudovirus decayed more rapidly on porous cardboard surfaces than on nonporous surfaces, including polyethylene (PE) plastic, stainless steel, and Teflon. Compared with that at 25°C, the decay rate of SARS-CoV-2 pseudovirus was significantly lower at low temperatures. Seawater preserved viral stability both at -18°C and with repeated freeze-thaw cycles compared with that in deionized water. Visible light from light-emitting diode (LED) illumination and airflow at -18°C reduced SARS-CoV-2 pseudovirus stability. Conclusion: Our studies indicate that temperature and seawater in the cold chain are risk factors for SARS-CoV-2 transmission, and LED visible light irradiation and increased airflow may be used as disinfection measures for SARS-CoV-2 in the cold-chain environment.
Subject(s)
COVID-19 , SARS-CoV-2 , Humans , COVID-19/prevention & control , Refrigeration , Disinfection , Stainless Steel , Plastics , Polytetrafluoroethylene , PolyethylenesABSTRACT
Since the beginning of the COVID19 pandemic, there has been a lack of data to quantify the role played by breathing-out of pathogens in the spread of SARS-Cov-2 despite sufficient indication of its culpability. This work aims to establish the role of aerosol dispersion of SARS-Cov-2 virus and similar airborne pathogens on the spread of the disease in enclosed spaces. A steady-state fluid solver is used to simulate the air flow field, which is then used to compute the dispersion of SARS-Cov-2 and spatial probability distribution of infection inside two representative classrooms. In particular, the dependence of the turbulent diffusivity of the passive scalar on the air changes per hour and the number of inlet ducts has been given due consideration. By mimicking the presence of several humans in an enclosed space with a time-periodic inhalation-exhalation cycle, this study firmly establishes breathing as a major contributor in the spread of the pathogen, especially by superspreaders. Second, a spatial gradient of pathogen concentration is established inside the domain, which strongly refutes the well-mixed theory. Furthermore, higher ventilation rates and proximity of the infected person to the inlet and exhaust vents play an important role in determining the spread of the pathogen. In the case of classrooms, a ventilation rate equivalent to 9 air changes or more is recommended. The simulations show that the "one-meter distance rule"between the occupants can significantly reduce the risk of spreading infection by a high-emitter. © 2023 Author(s).
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Negative pressure wards are significant in preventing the spread of infectious pathogens which play a crucial role in fighting against COVID-19. Owing to the negative pressure, contaminated air with pathogens is not able to flow from the wards to non-contaminated zones while fresh filtered air will be transported to the ward via the ventilation system. As airflow controlled by ventilation systems affects the motion of pathogens, for example, infectious aerosol particles, the ability of a negative pressure ward to reduce the risk of infection highly relies on an effective ventilation system. In this investigation, impacts of airflow patterns under various human postures and ventilation processes aerosols diffusion are analyzed via the computational fluid dynamics (CFD) simulation. According to the results, among three airflow patterns, the highest contaminant removal efficiency is 57% at 200 s with the top supply and bottom return mode;besides, in three postures, in the case that the patient is in a standing position, the contaminant removal efficiency is the highest. Furthermore, it is found that the best airflow scheme is a slit tuyere in the ward, with a top supply and side return mode and a sitting position for the patient. This study may provide a reference for the design of airflow in negative pressure isolation wards, control of contaminants, and prevention of viral infections, so as to ensure a good working and recovery environment for medical staff and patients. [ FROM AUTHOR] Copyright of Simulation is the property of Sage Publications, Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full . (Copyright applies to all s.)
ABSTRACT
The Air borne transmission is a very big concern for highly infectious diseases like Covid-19 and other airborne diseases. A micro droplet and aerosol can be carried out in the air and can remain flowing in air over a distance in a confined space, leading to affecting high number of people getting prone to infection and it is very dangerous in enclosed spaces or shared spaces. Public places, shared facilities are the areas, where infectious aerosol can be present in the air for a long duration. Ventilation of closed spaces, shared spaces is the need of hour to have analysed and deep study in context of infectious airborne diseases. Introduction of fresh air into the enclosed environment at regular interval of times may lead to fast dilution of air present in the enclosed space. The prominent building codes and HVAC guidelines allows as to calculate ACPH (Air changes per hour) in an enclosed space as per the occupancy and flow rate. The age of air is the criteria to define the amount of air residing in the enclosed space when it enters the space till its exhaust from that space. The more the age of air in the particular area the more can be the infection probability among the occupants. It is predominant to study the airflow pattern caused due to ventilation which can be collaborated with age of air to know about the infection probability. Typically, a classroom geometry is assumed with inlet outlet boundary conditions where exhaust fan is playing a major role of displacement ventilation. Study of air recirculation zones and dead zones is the point of interest of this study. Computational fluid dynamics is the most powerful tool in the present era to study the air flow pattern in enclosed and shared spaces.Copyright © 2022, Anka Publishers. All rights reserved.
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With increasing the COVID-19 pandemic and the time spent indoor, there is a growing research interest in the issue of Indoor Environmental Quality in building including thermal environment and indoor air quality (IAQ). Research and intervention in schools are a particular focus, as children are especially vulnerable to air pollution. The aim of this study is to assess the impact of energy renovation, including the installation of a balanced ventilation system with a filter (F7 type), on the IAQ of a school building located in a polluted outdoor environment. The study is based on measurements of some parameters of thermal environment and IAQ. To this end, two classrooms were chosen for two measurement campaigns. Each campaign covered 2 months in winter in 2018 and 2020 before and after renovation, respectively. The measurements included ventilation airflow rates, temperature, relative humidity, carbon dioxide, and particle concentration (PM2.5). The main result of installing the balanced ventilation was an increase in the air change rate from 0.1 h−1 and 0.05 h−1 before the renovation to 1.5 h−1 and 1.7 h−1 after the renovation, for classroom 1 and classroom 2, respectively. This increase changed the ICONE air stuffiness level from average air stuffiness to fresh air (no air stuffiness). However, this increase resulted in a significant entry of outdoor particles. As consequence, the highest indoor/outdoor concentration ratio (57%) was observed after the renovation. All these results highlights that ventilation performance should be extended to parameters as filtration efficiencies in order to increase IAQ. © 2023 Elsevier Ltd
ABSTRACT
Introduction: Many COVID-19 patients need prolonged artificial ventilation. Skeletal muscle wastes rapidly when deprived of neural activation, and in ventilated patients the diaphragm muscle begins to atrophy within 24 hours (ventilator induced diaphragmatic dysfunction, VIDD). This profoundly weakens the diaphragm, complicating the weaning of the patient off the ventilator, and increasing the risk of complications such as bacterial pneumonia. 40% of the total duration of mechanical ventilation in ITU patients is accounted for by the weaning period, after the initial illness has resolved. Prevention of VIDD would therefore both improve individual outcomes, and also release ITU capacity. We aim to prevent VIDD by exercising the diaphragm with electrical stimulation of the nerves that control it. Evidence suggests that muscle wasting can be prevented by quite low levels of exercise (e.g. 200 contractions per day). Materials / Methods: The diaphragm is activated by the phrenic nerves, formed from branches of the C3-C5 nerve roots in the neck. These nerves may be electrically stimulated in the lower neck. An electrode array is positioned on each side of the neck using surface landmarks. The system automatically determines the best electrode to use in each array. Sensors built into the ventilatory circuit are monitored both to match stimulation to the respiratory cycle and to determine the effects of stimulation. Result(s): We have designed and built a prototype system for unsupervised noninvasive phrenic nerve stimulation. The system delivers one contraction every 7 minutes, synchronised to early inspiration so as not to disrupt ventilation. Electrode impedances are measured before each stimulus, and the closed loop system continuously monitors the effects of stimulation on airflow and adjusts stimulation parameters to compensate for changes in coupling, for example due to head movement. Discussion(s): This stimulator system overcomes several limitations of existing solutions, namely the resource implications and risk profile of invasive electrodes, and the requirement for supervised operation. While invasive systems are applied selectively for these reasons, routine use of our system can be envisaged. This system was inspired by COVID-19 patients but is not limited to them, and has broad applicability to ventilated intensive care patients in general, for example patients with traumatic brain injury. Conclusion(s): Non-invasive stimulation of the phrenic nerves using pressure-free skin surface electrodes is feasible and safe. It offers the potential for prevention of VIDD and thereby faster ventilator weaning and shorter stay on ITU. Clinical trials are planned in 2022. Learning Objectives: After this presentation delegates should be aware of: 1. Ventilation induced diaphragm dysfunction (VIDD) and its importance in patients having lengthy periods of ventilation, as in many cases of COVID-19. 2. The fact that low levels of activity can maintain the condition of skeletal muscles including the diaphragm muscle 3. The potential for noninvasive stimulation of the phrenic nerves to provide 'diaphragm exercise' and prevent VIDD. Keywords: phrenic nerve stimulation, diaphragm, ventilation, COVID-19Copyright © 2022