Effect Of Ventilation Strategy Research Articles

Analyzing temperature distribution in cable cabins within utility tunnels: Developing effective ventilation strategies for local thermal environment enhancement

Convection heat transfer between the cables and the air in the cable cabin of the utility tunnel can lead to high temperatures in the cable cabin. High-temperature environments may cause the performance of cable systems to degrade, threatening the stability of the city's power supply. Increasing ACH (air changes per hour) alone could not effectively improve the high temperature at the end of the cable cabin. This paper employed numerical simulations and rigorous experimental validation to study the summer temperature field of cable cabins in Xi'an. An innovative disturbance ventilation method was proposed to alleviate the high-temperature phenomenon. The results indicated that as the wind flow length increases, the temperatures rise rapidly with the distance increased, resulting in a stable high-temperature area at the end of the cable cabin and the high-temperature air accumulated at the top by thermal buoyancy. When the ACH (air changes per hour) increased from 2 to 6, the temperature field range decreased by 3.25–6.39 %, and the variance decreased by 6.03–14.42 %. After installing a disturbance fan at the beginning of the stable zone, the temperature field in the cable cabin was fully mixed. Compared to directly increasing the ACH, the temperature field range decreased by 20.65–44.76 %, and the variance decreased by 40.28–64.47%. The introduction of a disturbance fan could thoroughly mix the air and effectively improve the local thermal environment in the cable cabin. This study contributed to the optimization of cable cabin ventilation strategies.

The influence of ventilation on airborne transmission between stacking toilets

Multiple COVID-19 outbreaks in high-rise residential buildings have been linked to the vertical spread of the virus along the building. This study aimed to provide empirical evidence and experimental results to evaluate the effects of toilet ventilation on the spread of bathroom aerosols in high-rise residential buildings. This study explored potential transmission pathways by conducting tracer gas experiments in a full-scale mock-up toilet facility and identified effective strategies to minimize tracer gas surge and overall exposure. A novel IoT-enabled tracer gas sensing network was used to evaluate tracer gas dispersion from a lower-floor toilet to an upper-floor toilet and the roof under 32 different ventilation conditions of windows, exhaust fans, and forward-facing wind. The findings confirmed the potential for vertical airborne transmission through toilet ventilation and suggested effective ventilation strategies for forward-facing wind and no-wind conditions. This study provided novel experimental results on vertical aerosol transmission, contributing to further analysis and validation in this field. Appropriate ventilation measures were also discussed to ensure clean, virus-free air intake, reducing the risk of airborne cross-infection via the vertical transmission pathway.

Experimental comparison on the smoke movement in horizontal and downhill tunnel fires under subcritical ventilation

In longitudinally ventilated tunnel fires, subcritical ventilation is widely used in the early stage of accidents to maintain smoke stratification. Due to the stack effect, the smoke movement in inclined tunnels is different from that in horizontal tunnels. In this study, a series of brine-water experiments are carried out to compare the characteristics of buoyant contaminants flow in horizontal and downhill tunnels under subcritical ventilation, which has not been experimentally investigated. The results suggest that subcritical ventilation is an effective longitudinal ventilation strategy in the early stage of horizontal tunnel fires, as it can retain the smoke stratification and an acceptable back-layering flow. Moreover, the critical ventilation condition can be resumed after the ventilation pressure increases to the critical value. However, if subcritical ventilation is first adopted in downhill tunnel fires, no stable back-layering flow will be observed, the buoyant contaminants consistently flow out from the higher exit, ultimately leading to the establishment of a “stack-dominated flow regime”. Under this circumstance, even if the ventilation pressure increases to the critical value or slightly higher, the buoyant contaminants upstream of the source still cannot be pushed back. Moreover, the reduced gravity of the smoke in the tunnel increases as the ventilation pressure rises. Therefore, subcritical ventilation is not suitable for downhill tunnel fires. The study is helpful for understanding the smoke movement in horizontal and inclined tunnel fires under subcritical ventilation.

The effects of ventilation conditions on mitigating airborne virus transmission

The effects of ventilation strategies on mitigating airborne virus transmission in a generic indoor space representative of a lobby area or information desk found in a hotel, company, or cruise ship are presented. Multiphase computational fluid dynamics simulations are employed in conjunction with evaporation modeling. Four different ventilation flow rates are examined based on the most updated post-COVID-19 pandemic standards from health organizations and recent findings from research studies. Three air changes per hour provide the best option for minimizing droplet spreading at reasonable energy efficiency. Thus, a higher ventilation rate is not the best solution to avoid spreading airborne diseases. Simultaneous coughing of all occupants revealed that contagious droplets could be trapped in regions of low airflow and on furniture, significantly prolonging their evaporation time. Multiphase flow simulations can help define ventilation standards to reduce droplet spreading and mitigate virus transmission while maintaining adequate ventilation with lower energy consumption. The present work significantly impacts how heat, air-conditioning, and ventilation systems are designed and implemented.

Ventilation Strategies for Mitigating Indoor Air Pollutants in High-Rise Residential Buildings: A Case Study in Dubai

This study investigates the effectiveness of different ventilation methods in reducing indoor air pollutants in newly constructed residential buildings, focusing on indoor air quality (IAQ) in Dubai. The paper highlights the growing concern for IAQ in response to residents’ increasing awareness of their well-being and environmental sustainability. The study examines the concentrations of formaldehyde (HCHO), volatile organic compounds (VOCs), and total volatile organic compounds (TVOC) in bedrooms and living rooms before and after implementing various ventilation methods during the construction phase. The findings indicate that mechanical exhaust ventilation, mainly through bathroom and kitchen exhaust fans, was highly effective in reducing HCHO levels. Combining kitchen and bathroom exhaust fans demonstrated the most significant reduction in HCHO concentrations. Similarly, reductions in VOCs, such as ethylbenzene, toluene, and xylene, were observed with different ventilation methods. Natural ventilation also proved effective in reducing pollutant concentrations. The results emphasize the importance of implementing appropriate ventilation strategies to improve IAQ in residential buildings. However, the study acknowledges the limitations of a single-location measurement and recommends further research to validate the findings across different building types and locations. Additionally, long-term studies are necessary to assess the sustained effects of ventilation methods on IAQ. The study highlights the significance of addressing IAQ concerns in residential buildings and suggests potential research directions to explore other ventilation strategies and their energy efficiency implications. Ultimately, this research contributes to developing healthier and sustainable living environments by promoting effective ventilation strategies to mitigate indoor air pollutants.

CFD modeling of room airflow effects on inactivation of aerosol SARS-CoV-2 by an upper-room ultraviolet germicidal irradiation (UVGI) system

Ultraviolet germicidal irradiation (UVGI) systems inactivate microorganisms indoors. Upper-room UVGI systems use wall- or ceiling-mounted fixtures to create an air disinfection zone above the occupied zone. The performance of upper-room UVGI systems varies with indoor airflow patterns induced by mechanical ventilation and thermal plumes from indoor heat sources. Little information is available on the effects of ventilation strategies on upper-room UVGI system performance for the control of viral aerosols in occupied spaces. This study simulated the effects of ventilation system characteristics in an office space on the ability of an upper-room UVGI system to inactivate viral aerosols with UV-C susceptibility representative of coronaviruses. UVGI reduced viral aerosol concentration by two orders of magnitude relative to the concentration without UVGI. Air change rates and air distribution strategy (mixing vs. displacement) had notable effects on the effectiveness of the UVGI system. For mixing ventilation, as the recirculation airflow rate increased from 0 to 5.3 h−1 for a room volume of 108 m3 with a fixed outdoor air change rate of 0.7 h−1, UVGI inactivation increased by 96.7%. Mixing ventilation with 100% outdoor air of 0.7 h−1 yielded airborne virus inactivation that was double that of displacement ventilation, due to enhanced air mixing.

The assessment of personal exposure in restaurants considering heat sources and ventilation strategies

Outbreaks of airborne infections during meal consumption in diverse restaurant settings have been extensively reported. It is widely recognized that effective ventilation strategies are essential to minimize the infection risk in indoor environments, and these strategies should be tailored to the heat sources. The purpose of this study is to compare the spatial distribution of risk in restaurant rooms that use mixing or displacement ventilation, specifically focusing on the heat sources used for different food types, namely hotpot, normal Chinese food, and iced food. Computational Fluid Dynamics (CFD) was employed to assess exposure risk. Our results indicate that the use of low-temperature heat sources can elevate the risk of infection by increasing the local vertical temperature gradient. In comparison to no heat source, the risk increased by 190.9% and 99.6% for displacement and mixing ventilation strategies, respectively. Under mixing ventilation, both low-temperature and no heat sources showed lower infection risks when compared to displacement ventilation. However, displacement ventilation is found to be highly effective in reducing the risk of infection when using a high-temperature heat source, with only 12.3% of the infection risk observed in mixing ventilation. Furthermore, the use of displacement ventilation resulted in a significant reduction in the odors emitted by hotpot, which were instead absorbed by clothes in the mixing ventilation scenario. Our findings provide crucial insights into the development of appropriate ventilation strategies for reducing personal exposure to airborne infections in diverse restaurant settings. Specifically, we recommend using displacement ventilation in restaurants that utilize high-temperature heat sources, as it can substantially reduce the risk of infection.

Overlooked Impacts of Urban Environments on the Air Quality in Naturally Ventilated Schools Amid the COVID-19 Pandemic

The density, form, and dimensions of urban morphology are important for healthy living conditions in cities, especially if they are related to the climate and air pollution. Morphology and environmental conditions determine the relationship between open and built space, the width of street spaces, the aerodynamic characteristics of wind currents, albedo, and the retention of pollutants, as well as determining the radiative exchange with the atmosphere. Studies on the COVID-19 pandemic have focused on the assumption of a possible relationship between the spread of the SARS-CoV-2 virus and the presence and concentration of airborne particulate matter (PM10 and PM2.5). This paper focuses on the research of indoor air quality (IAQ) in two schools with naturally ventilated classrooms in Ljubljana, Slovenia. The presence of particulate matter (PM2.5 and PM10) and the concentration of CO2 were studied, along with other microclimatic conditions, e.g., ambient temperature, relative humidity, air pressure, and wind conditions. These were compared and assessed via analysis of variance (ANOVA) and Duncan’s post hoc test. The main concern was to see how effective different ventilation strategies are, as well as how the openings in the classroom impact the concentrations of CO2 relative to the concentrations of PM2.5 and PM10 particles as a side effect of these ventilation strategies. The inconsistent application of recommended COVID-19 ventilation strategies suggests that IAQ in naturally ventilated classrooms is highly determined by individual perceptions of indoor air quality. The results also suggest that the IAQ is significantly affected by the schools’ urban environment; however, this is not considered within the national COVID-19 ventilation recommendations. Future ventilation guidelines for pandemics should also include the urban environment as a risk factor for inadequate IAQ, instead of focusing solely on pathogen characteristics.

An intelligent HVAC control strategy for supplying comfortable and energy-efficient school environment

In South Korea, school buildings require significant energy inputs for heating and air-conditioning, and the majority of the occupants are adolescent students, whose health and cognitive performance are vulnerable to poor indoor air quality (IAQ) and thermal discomfort. Using field measurements, some previous studies have reported that some Korean schools have poor IAQ and thermal conditions. Thus, it is necessary to develop effective heating, ventilation, and air-conditioning (HVAC) control strategies to improve the indoor environment and reduce energy consumption. Therefore, this study proposes an intelligent HVAC integrated control strategy that can improve indoor environmental quality (IEQ) and reduce energy consumption in school buildings. The proposed strategy utilizes an integrated neural network prediction model for IEQ and a heuristic method that can optimize control objectives (i.e., the predicted mean vote [PMV], carbon dioxide [CO2], particulate matter with diameters of 10 and 2.5 μm [PM10 and PM2.5, respectively], and HVAC energy consumption). To evaluate the control performance of the proposed strategy, the present study employs two base algorithms (i.e., a rule-based and a non-adaptive control approach) under non-disturbance and forcing disturbance scenarios. The control failure period for PMV is found to be 1.6420% and 9.4773% of the total occupancy period under the non-disturbance and forcing disturbance scenarios, respectively, while CO2 control failure does not occur under either scenario. The control failure periods for PM10 and PM2.5 were 5.1676%, and 7.1844%, respectively, under forcing disturbance. Under the non-disturbance scenario, the proposed strategy consumed 2,467.07 kWh and 870,26 kWh for heating and cooling, respectively, representing 91.1% and 84.08% of that for the rule-based algorithm. The proposed strategy can thus effectively improve the IEQ of a building and has the potential for use in the development of integrated environmental management solutions for buildings.

Effect of Ventilation Strategy During Cardiopulmonary Bypass on Arterial Oxygenation and Postoperative Pulmonary Complications After Pediatric Cardiac Surgery: A Randomized Controlled Study

To compare the effects of 3 ventilation strategies during cardiopulmonary bypass (CPB) on arterial oxygenation and postoperative pulmonary complications (PPCs). A prospective, randomized, controlled study. A single-center tertiary teaching hospital. One hundred twenty pediatric patients undergoing elective repair of congenital acyanotic heart diseases with CPB. Patients were assigned randomly into 3 groups according to ventilation strategy during CPB as follows: (1) no mechanical ventilation (NOV), (2) continuous positive airway pressure (CPAP) of 5 cmH2O, (3) low tidal volume (LTV), pressure controlled ventilation (PCV), respiratory rate (RR) 20-to-30/min, and peak inspiratory pressure adjusted to keep tidal volume (Vt) 2 mL/kg. The PaO2/fraction of inspired oxygen (FIO2) ratio and PaO2 were higher in the 5 minutes postbypass period in the LTV group but were nonsignificant. The PaO2/FIO2 ratio and PaO2 were significant after chest closure and 1 hour after arrival to the intensive care unit with a higher PaO2/FIO2 ratio and PaO2 in the LTV group. Regarding the oxygenation index, the LTV group was superior to the NOV group at the 3 time points, with lower values in the LTV group. There were no significant differences in the predictive indices among the 3 groups, including the extubation time, and postoperative intensive care unit stays days. The incidence of PPCs did not significantly differ among the 3 groups. Maintaining ventilation during CPB was associated with better oxygenation and did not reduce the incidence of PPCs in pediatric patients undergoing cardiac surgery.

Solar Chimneys as an Effective Ventilation Strategy in Multi-Storey Public Housing in the Post-COVID-19 Era

This paper studies the effectiveness of a solar chimney for improving ventilation and air-exchange rates in multi-storey public housing in tropical climates for the potential mitigation of airborne disease transmission. Virtual models of a typical apartment room with natural cross-ventilation, replicated across four levels to mimic a multi-storey block, were set up with six internal wind velocity sensor points per floor. The simulation software Energy2D was then used to evaluate the performance of the models, first testing the presence of a solar chimney, and then additionally the degree to which the solar chimney model was affected by a complementary ceiling fan. Wind velocity was also measured, as this is a variable that affects ACH rates. Using a non-parametric Wilcoxon signed-rank test, the introduction of a solar chimney was found to have a significant impact on air-flow rates (a variable that positively affects air-exchange rates), resulting in a p-value of 0.000 and Z-value of −3.920. Regression analysis determined that the solar chimney’s effect was enhanced when complemented by a ceiling fan (R-squared value of 0.4687). Consequently, we propose several design strategies that may enable the adoption of the solar chimney concept to improve natural ventilation in residential units.

Programmed multi-level ventilation in COVID-19-related acute respiratory distress syndrome: a multi-center retrospective observational study.

ObjectiveWe evaluated pressure-controlled ventilation (PCV) with multiple programmed levels of positive end expiratory pressure (programmed multi-level ventilation; PMLV) in patients with coronavirus disease 2019 (COVID-19)-related acute respiratory distress syndrome (ARDS).MethodsWe conducted a multicenter, retrospective study from November 2020 to February 2021. PMLV was used with PCV in all patients with intensive care admission until improvement in oxygenation (fraction of inspired oxygen [FiO2] ≤0.50 and oxygen saturation [SpO2] >92%). The observed outcomes were improvement of hypoxemia, length of mechanical ventilation, partial pressure of carbon dioxide (PaCO2) stability, and adverse events.ResultsOf 188 mechanically ventilated patients with COVID-19-related ARDS, we analyzed 60 patients treated with PMLV. Hypoxemia improved in 55 (92%) patients, as measured by the change in partial pressure of oxygen/FiO2 and SpO2/FiO2 ratios on day 3 versus day 1, and in 32 (66%) ventilated patients on day 7 versus day 3. The median (interquartile range) length of mechanical ventilation for survivors and non-survivors was 8.4 (4.7–14.9) and 6.7 (3.6–10.3) days, respectively.ConclusionsPMLV appears to be a safe and effective ventilation strategy for improving hypoxemia in patients with COVID-19-related ARDS. Further studies are needed comparing the PMLV mode with the conventional ARDS ventilatory approach.

Examining lung mechanical strains as influenced by breathing volumes and rates using experimental digital image correlation

BackgroundMechanical ventilation is often employed to facilitate breathing in patients suffering from respiratory illnesses and disabilities. Despite the benefits, there are risks associated with ventilator-induced lung injuries and death, driving investigations for alternative ventilation techniques to improve mechanical ventilation, such as multi-oscillatory and high-frequency ventilation; however, few studies have evaluated fundamental lung mechanical local deformations under variable loading.MethodsPorcine whole lung samples were analyzed using a novel application of digital image correlation interfaced with an electromechanical ventilation system to associate the local behavior to the global volume and pressure loading in response to various inflation volumes and breathing rates. Strains, anisotropy, tissue compliance, and the evolutionary response of the inflating lung were analyzed.ResultsExperiments demonstrated a direct and near one-to-one linear relationship between applied lung volumes and resulting local mean strain, and a nonlinear relationship between lung pressures and strains. As the applied air delivery volume was doubled, the tissue surface mean strains approximately increased from 20 to 40%, and average maximum strains measured 70–110%. The tissue strain anisotropic ratio ranged from 0.81 to 0.86 and decreased with greater inflation volumes. Local tissue compliance during the inflation cycle, associating evolutionary strains in response to inflation pressures, was also quantified.ConclusionVentilation frequencies were not found to influence the local stretch response. Strain measures significantly increased and the anisotropic ratio decreased between the smallest and greatest tidal volumes. Tissue compliance did not exhibit a unifying trend. The insights provided by the real-time continuous measures, and the kinetics to kinematics pulmonary linkage established by this study offers valuable characterizations for computational models and establishes a framework for future studies to compare healthy and diseased lung mechanics to further consider alternatives for effective ventilation strategies.

Aggressive repeat manual pulmonary recruitment maneuver with pure oxygen as a new treatment of venous air embolism

Venous air embolism (VAE) is a largely iatrogenic clinical problem, which can result in serious morbidity and even death. Even with appropriate treatment, VAE still leads to a high overall one-year mortality. New feasible and effective treatment will be life-saving, especially when the routine treatment failed or is contraindicated. The manual pulmonary recruitment maneuver is an effective ventilation strategy to improve respiratory mechanics, increase pulmonary oxygen exchange and arterial oxygenation, and improve patient outcomes. Meanwhile, it could squeeze the heart, which could smash the air embolism and drive the air to move out from the pulmonary outflow tract then relieve the pulmonary obstruction. Recently, we success treatment a patient with intraoperative VAE by this maneuver as the routine treatment failed. However, there is still a lack of trials to evaluate the efficiency of a new treatment for VAE. Hence, we hypothesize that an aggressive repeat manual pulmonary recruitment maneuver with pure oxygen could be an effective alternative treatment in a patient with intraoperative VAE when the routine treatment failed or was contraindicated.

Optimization of Embodied energy and operational energy of school design by comparing conventional and sustainable Material configurations

In recent times, the use of sustainable building materials is gaining momentum as the general public has started understanding the energy exploitation and also ill effects of using pollutant emitting materials. Also, usage of high energy-intensive materials is on the decline as all international agencies have started making a strong call on climate change (carbon release). Therefore, usage of materials with less embodied energy is the need of the hour. Hence this study aims at exploring the possibilities to optimize the embodied energy and operational energy by selecting sustainable building materials, ventilation and lighting aspects in the design of school buildings. Two designs of school buildings have been done, namely conventional and Regenerative. The conventional design has typically used construction materials like RCC, fired clay brick etc., whereas in regenerative design materials of less embodied energy like CSEB blocks, no VOC paints, etc., have been used. Also in regenerative design, effective ventilation strategies and more openness to sky areas have been done in order to make buildings more passive. Embodied energy for all building components like floor, roof, foundations, wall has been calculated separately and cumulated for the entire floor area. Operational energy was also calculated for both conventional and regenerative design using modeling software plugin. As findings, both embodied energy and operational energy was found to be low for regenerative design when compared with conventional design. As a result, a design with low embodied energy and operational energy has been proposed with all supporting data. Future studies can be done on different material configurations for wall, roofs, floors, foundations and Embodied energy as output for each variable of input. For different ventilation and lighting configurations, operational energy can be found.

Effect of ventilation strategy during cardiopulmonary bypass on postoperative pulmonary complications after cardiac surgery: a randomized clinical trial

BackgroundTo determine whether maintaining ventilation during cardiopulmonary bypass (CPB) with a different fraction of inspired oxygen (FiO2) had an impact on the occurrence of postoperative pulmonary complications (PPCs).MethodsA total of 413 adult patients undergoing elective cardiac surgery with CPB were randomly assigned into three groups: 138 in the NoV group (received no mechanical ventilation during CPB), 138 in the LOV group (received a tidal volume (VT) of 3–4 ml/kg of ideal body weight with the respiratory rate of 10–12 bpm, and the positive end-expiratory pressure of 5–8 cmH2O during CPB; the FiO2 was 30%), and 137 in the HOV group (received the same ventilation parameters settings as the LOV group while the FiO2 was 80%).ResultsThe primary outcomes were the incidence and severity of PPCs during hospitalization. The composite incidence of PPCs did not significantly differ between the NoV (63%), LOV (49%) and HOV (57%) groups (P = 0.069). And there was also no difference regarding the incidence of PPCs between the non-ventilation (NoV) and ventilation (the combination of LOV and HOV) groups. The LOV group was observed a lower proportion of moderate and severe pulmonary complications (grade ≥ 3) than the NoV group (23.1% vs. 44.2%, P = 0.001).ConclusionMaintaining ventilation during CPB did not reduce the incidence of PPCs in patients undergoing cardiac surgery.Trial registration: Chinese Clinical Trial Registry ChiCTR1800015261. Prospectively registered 19 March 2018. http://www.chictr.org.cn/showproj.aspx?proj=25982

Identification of distinct clinical phenotypes of acute respiratory distress syndrome with differential responses to treatment

BackgroundAcute respiratory distress syndrome (ARDS) is a heterogeneous syndrome, and the identification of homogeneous subgroups and phenotypes is the first step toward precision critical care. We aimed to explore whether ARDS phenotypes can be identified using clinical data, are reproducible and are associated with clinical outcomes and treatment response.MethodsThis study is based on a retrospective analysis of data from the telehealth intensive care unit (eICU) collaborative research database and three ARDS randomized controlled trials (RCTs) (ALVEOLI, FACTT and SAILS trials). We derived phenotypes in the eICU by cluster analysis based on clinical data and compared the clinical characteristics and outcomes of each phenotype. The reproducibility of the derived phenotypes was tested using the data from three RCTs, and treatment effects were evaluated.ResultsThree clinical phenotypes were identified in the training cohort of 3875 ARDS patients. Of the three phenotypes identified, phenotype I (n = 1565; 40%) was associated with fewer laboratory abnormalities, less organ dysfunction and the lowest in-hospital mortality rate (8%). Phenotype II (n = 1232; 32%) was correlated with more inflammation and shock and had a higher mortality rate (18%). Phenotype III (n = 1078; 28%) was strongly correlated with renal dysfunction and acidosis and had the highest mortality rate (22%). These results were validated using the data from the validation cohort (n = 3670) and three RCTs (n = 2289) and had reproducibility. Patients with these ARDS phenotypes had different treatment responses to randomized interventions. Specifically, in the ALVEOLI cohort, the effects of ventilation strategy (high PEEP vs low PEEP) on ventilator-free days differed by phenotype (p = 0.001); in the FACTT cohort, there was a significant interaction between phenotype and fluid-management strategy for 60-day mortality (p = 0.01). The fluid-conservative strategy was associated with improved mortality in phenotype II but had the opposite effect in phenotype III.ConclusionThree clinical phenotypes of ARDS were identified and had different clinical characteristics and outcomes. The analysis shows evidence of a phenotype-specific treatment benefit in the ALVEOLI and FACTT trials. These findings may improve the identification of distinct subsets of ARDS patients for exploration in future RCTs.

A hybrid deep transfer learning strategy for thermal comfort prediction in buildings

Since the thermal condition of living spaces affects the occupants' productivity and their quality of life, it is important to design effective heating, ventilation and air conditioning (HVAC) control strategies for better energy efficiency and thermal comfort. An essential step in HVAC control and energy optimization is thermal comfort modeling. Recently, data-driven thermal comfort models have been preferred over the Fanger's Predicted Mean Vote (PMV) model due to higher accuracy and ease of use. However, the unavailability of comprehensive labelled thermal comfort data from the occupants poses a significant modeling challenge. This paper addresses data inadequacy issues by adopting ‘transfer learning’ to leverage well learned knowledge from source domain (same climate zones) to target domain (different climate zone) where modeling data is sparse. Specifically, a Transfer Learning based Convolutional Neural Networks-Long Short Term Memory neural networks (TL CNN-LSTM) is designed for effective thermal comfort modeling that exploits the spatio-temporal relations in the thermal comfort data. The significant modeling parameters for TL CNN-LSTM are identified using the Chi-squared test. Further, the lack of sufficient samples across all thermal conditions in the available thermal comfort datasets was handled by Synthetic Minority Oversampling Technique (SMOTE). Experiments with two source (ASHRAE RP-884 and Scales Project) and one target (Medium US office) datasets demonstrate the ability of TL CNN-LSTM in achieving an accuracy of >55% with limited data in target buildings. The limitation of TL CNN-LSTM is its continued dependence on intrusive parameters and the challenges in assessing its adaptability to different climate zones.

A Multicenter Cross-sectional Questionnaire-based Study to Know the Practices and Strategies of Ventilatory Management of COVID-19 Patients among the Treating Physicians.

IntroductionCOVID-19 has been declared a pandemic by the World Health Organization (WHO). Many of the COVID-19 patients develop acute respiratory distress syndrome (ARDS) and require ventilatory support based on their severity for which conventional strategies are being used along with few newer strategies. We conducted this multicenter survey to know the physician's current ventilation strategies adopted for the care of COVID-19 patients.Materials and methodsThe survey was conducted after taking the ethical committee clearance. The web-based multicenter, cross-sectional questionnaire study was sent to physicians, who were involved in the management of COVID-19 patients. The questionnaire was segregated into three parts: part one consisted of general information and consent form, part two was concerned regarding demographic characteristics, and part three was concerned about their practices and strategies for ventilation of COVID-19 patients.ResultsA total of 223 responders replied for the questionnaire; 190 participated in the study saying that they are involved in the management of COVID-19 patients. The answers to the questionnaires were expressed as a percentage of total responses. 86% of the respondents said they have a designated intensive care unit (ICU) and 89% of the responders said they have an intubation/extubation protocol for suspect/confirmed COVID-19 patients. The responses of junior residents (JRs), senior residents (SRs), assistant professors/junior consultants, and professors/consultants were analyzed separately, and a few significant differences were observed. 39% of JRs were aware of prone ventilation as the most effective rescue ventilation strategy compared to 69% of consultants/professors. Extracorporeal membranous oxygenation (ECMO) strategy was also more significant in consultants/professors (40%) vs JRs (12%). The responders were also diverged based on medical college and corporate hospitals, and their responses were noted. Most commonly, responders in the corporate hospitals had a facility to ventilate COVID-19 patients in a negative pressure isolation facility compared to a nonnegative pressure room isolation facility in medical colleges.ConclusionMost of the responders were practicing ventilation strategies in a standard manner. JRs need to undergo further training in a few aspects of the ventilatory management, and also, they need to update themselves with newer treatment modalities as they keep evolving. Medical colleges are providing at par facility compared to corporate hospitals except for few advance care facilities.Clinical significanceThis study highlights the current practice of ventilatory management of COVID-19 patients, which is satisfactory. The survey can be used to develop study tools, to educate resident doctors, to further improve quality of care of critical COVID-19 patients.How to cite this articleMaddani SS, Deepa HC, Rao S, Chaudhuri S. A Multicenter Cross-sectional Questionnaire-based Study to know the Practices and Strategies of Ventilatory Management of COVID-19 Patients among the Treating Physicians. Indian J Crit Care Med 2020;24(8):643–648.

Effects of intraoperative individualized PEEP on postoperative atelectasis in obese patients: study protocol for a prospective randomized controlled trial

BackgroundObese patients undergoing general anesthesia and mechanical ventilation during laparoscopic abdominal surgery commonly have a higher incidence of postoperative pulmonary complications (PPCs), due to factors such as decreasing oxygen reserve, declining functional residual capacity, and reducing lung compliance. Pulmonary atelectasis caused by pneumoperitoneum and mechanical ventilation is further aggravated in obese patients. Recent studies demonstrated that individualized positive end-expiratory pressure (iPEEP) was one of effective lung-protective ventilation strategies. However, there is still no exact method to determine the best iPEEP, especially for obese patients. Here, we will use the best static lung compliance (Cstat) method to determine iPEEP, compared with regular PEEP, by observing the atelectasis area measured by electrical impedance tomography (EIT), and try to prove a better iPEEP setting method for obese patients.MethodsThis study is a single-center, two-arm, prospective, randomized control trial. A total number of 80 obese patients with body mass index ≥ 32.5 kg/m2 scheduled for laparoscopic gastric volume reduction and at medium to high risk for PPCs will be enrolled. They will be randomly assigned to control group (PEEP5 group) and iPEEP group. A PEEP of 5 cmH2O will be used in PEEP5 group, whereas an individualized PEEP value determined by a Cstat-directed PEEP titration procedure will be applied in the iPEEP group. Standard lung-protective ventilation methods such as low tidal volumes (7 ml/kg, predicted body weight, PBW), a fraction of inspired oxygen ≥ 0.5, and recruitment maneuvers (RM) will be applied during and after operation in both groups. Primary endpoints will be postoperative atelectasis measured by chest electrical impedance tomography (EIT) and intraoperative oxygen index. Secondary endpoints will be serum IL-6, TNF-α, procalcitonin (PCT) kinetics during and after surgery, incidence of PPCs, organ dysfunction, length of in-hospital stay, and hospital expense.DiscussionAlthough there are several studies about the effect of iPEEP titration on perioperative PPCs in obese patients recently, the iPEEP setting method they used was complex and was not always feasible in routine clinical practice. This trial will assess a possible simple method to determine individualized optimal PEEP in obese patients and try to demonstrate that individualized PEEP with lung-protective ventilation methods is necessary for obese patients undergoing general surgery. The results of this trial will support anesthesiologist a feasible Cstat-directed PEEP titration method during anesthesia for obese patients in attempt to prevent PPCs.Trial registrationwww.chictr.org.cn ChiCTR1900026466. Registered on 11 October 2019