Effects Of Ventilation Research Articles

Smoke movement and stratification of tunnel fires under coupled effects of rainfall and ventilation

This study investigates the smoke movement and stratification characteristics of tunnel fires under coupled effects of rainfall and ventilation through a series of reduced-scale tests. Results show that the smoke movement is affected by both ventilation and rainfall-induced airflow. The smoke tends to move downstream of the dominant airflow. As the increase in ventilation velocity, the height of the downstream smoke layer decreases. Conversely, as the rainfall intensity increases, the height of the upstream smoke layer decreases. Forced shear airflow consistently disrupts the smoke stratification downstream of the flow for both ventilation airflow and rainfall-induced airflow. A strong ventilation although capable of controlling smoke downstream, it may destroy the downstream smoke stratification. Compared to critical velocity, the confinement velocity is more suitable for tunnel smoke control as it maintains the stability of downstream smoke and thus can be applied in the early stage of fires. The confinement velocity is found to be 0.73 times the critical velocity. A model of the confinement velocity under the effect of rainfall is established. Findings are helpful in emergency rescue and evacuation of tunnel fires under rainfall conditions.

Comparison of short-term outcomes between Nasal Continuous Positive Airway Pressure and Nasal Intermittent Positive Pressure Ventilation in preterm neonates with respiratory distress syndrome.

Objective: To compare the safety and effectiveness of nasal continuous positive airway pressure (NCPAP) versus nasal intermittent positive pressure ventilation (NIPPV) as initial respiratory therapy among preterm neonates with respiratory distress syndrome (RDS). Study Design: Randomized Controlled Trial. Setting: The Neonatal Intensive Care Unit (NICU) of Indus Hospital and Health Network, Muzaffargarh, Pakistan. Period: January 2024 to June 2024. Methods: A total of 118 preterm neonates with 26-34 weeks gestation and admitted to NICU with RDS were randomly allocated to either NCPAP or NIPPV. Success respiratory support, along with complications, and mortality were noted. Results: In a total of 118 newborns, 64 (54.2%) were girls. The mean gestational age, and birth weight were 30.94±1.43 weeks, and 1479.07±310.69 grams. In NIPPV group, 49 (83.1%) babies showed successful outcome versus 29 (49.2%) in NCPAP group (p<0.001). Necessitation of intubation within 7 days (40.7% vs. 22.0%, p=0.029). Surfactant requirement (37.3% vs. 16.9%, p=0.013), and bronco pulmonary dysplasia (BDP) (11.9% vs. 0%, p=0.006) were significantly more in NCPAP group. Pneumothorax was significantly more prevalent in NIPPV group (18.6% vs. 3.4%, p=0.008). Duration of non-invasive support was significantly more in NCPAP group (10.58±6.07 vs. 8.15±3.58 days, p=0.009). Conclusion: NIPPV significantly outperformed NCPAP in terms of successful outcomes, as measured by reduced rates of intubation, surfactant requirement, and the incidence of BPD.

Impacts of HVAC cleaning on energy consumption and supply airflow: A multi-climate evaluation

Energy-efficiency interventions are crucial for sustainable building operations to accommodate emerging indoor air quality (IAQ) criteria into their engineering life cycles. While several studies have addressed building energy consumption and IAQ considerations separately, few provide integrated analysis of these aspects in response to building hygiene practices. In response, this study evaluates the effectiveness of routine heating, ventilation, and air conditioning (HVAC) cleaning on energy consumption and supply airflow patterns in non-residential public buildings. This study juxtaposes HVAC energy consumption and ventilation performance before, during and after routine HVAC cleaning, across buildings situated in four different climate zones, while operating in cooling mode. Each site had nearly identical HVAC systems serving similar architectural features and occupational loads; these were segregated into an intervention (cleaned HVAC system) that could be compared to an otherwise identically operating HVAC (control system), which was not cleaned. Following prescriptive cleaning, HVAC systems exhibited significant energy consumption reductions and delivered higher airflows compared to their uncleaned counterparts. On average, intervention systems saved between 41 % and 60 % on conveyance (fan/blower) energy, with one exception, and supplied 10 % and 46 % more airflow compared to their uncleaned counterparts. This research demonstrates how a new generation of low-cost HVAC system monitors can compile Internet of Things (IoT) archives to show immediate energy consumption benefits associated with cleaning HVAC components and their associated ductwork serving relatively high occupancy commercial and educational spaces.

Experimental study of ventilation performance of three ventilation strategies using aerosols and tracer gas

Effective ventilation plays a crucial role in reducing the risk of infection by airborne contaminants. This study was conducted in a hospital ward of specific dimensions (41.58 m3) equipped with two respiratory thermal manikins: a healthcare worker and an infected patient. Three ventilation strategies were employed in the ventilation system: supply and exhaust air through upper grilles, upper and lower grilles, and swirl diffusers with lower grilles. The air flow rate of the ventilation system was maintained constant at 200 m3/h. The airflow was distributed 50-50% by a combination of a personalised ventilation system and personalised exhaust system. The effectiveness of a ventilation system and its combination with a personalised exhaust system was investigated using aerosol and tracer gas techniques. The efficacy of contaminant removal was evaluated in both the patient and healthcare inhaled volume. Determination of the clean air flow rate of the three ventilation system strategies at inhaled volume was carried out. Also, the exposure of healthcare worker to the contaminants exhaled by infected patient in the microenvironment formed by both was analysed. Experimental findings revealed that CO2 showed a higher ventilation efficiency compared to particles, independently of the ventilation strategy used. The highest clean air flow rate values were detected in the inhaled volume of patient infected. On the other hand, the highest particle removal efficiency was observed in swirl diffusers with lower grilles, which combined the ventilation system with the PES. This strategy also showed the lowest exposure values in the microenvironment.

Investigation of the combustion law of delayed ignition ethanol spill fire in longitudinal ventilation

The environmental conditions under which sustained spill fire accidents occur are complex and variable, and this paper investigates experimentally the effect of longitudinal ventilation in tunnel on the combustion law of delayed ignition spill fires. Experiments on instantaneous ignition and spill fires with delay of 10 s, 20 s, and 30 s were carried out using ethanol at a spill rate of 78 ml/min under a longitudinal wind speed of 0–1.5 m/s in tunnel. The results show that with the increase of longitudinal wind speed the flame inclination of the spill fire increases and the flame length first increases and then decreases. By analysing the force on the fuel layer and the force on the flame, and combining with the previous research, the prediction models of flame length and flame inclination were established. In the case of longitudinal wind speed, the spill fire burning area increases and then decreases with the increase of wind speed, and there is a critical wind speed, which is related to the delayed ignition time. The heat loss of the substrate in the longitudinal wind and the influence of the flame morphology on the thermal radiation feedback of the flame were considered, and it was found that the heat transfer of the fuel layer with the increase of the wind speed was gradually transitioned from the radiation dominated to the convection dominated. It was found that there was a general trend of increasing combustion rate with increasing wind speed and delayed ignition time.

An Investigation of the Ventilation Systems of Whole-Indoor Urban Substations

The electricity load increases significantly with the development of the economy, which raises the issue of scarce land resources; therefore, the application of whole-indoor urban substations has become more and more extensive. However, both the closed environment of indoor substations and their unreasonable ventilation systems mean that the heat dissipation of the equipment cannot be discharged in time. In this study, a combination of natural and mechanical ventilation systems is developed to solve the problem of high indoor temperatures, and corresponding studies are conducted via both numerical simulation and experimental research. Firstly, the ventilation and heat dissipation problem of the whole-indoor urban substation was investigated using numerical simulation technology, and then the feasibility of the ventilation system was determined. Secondly, the experimental platform (including the heat dissipation equipment and ventilation system) was set up, the heat dissipation of the reactor room was analyzed, and the system was tested experimentally. Afterward, the noise generated by the experimental platform was measured and predicted. Finally, via the numerical simulation analysis, it was found that the ventilation effect would be improved regardless of the heat dissipation and that reducing the outdoor temperature or increasing the ventilation volume would reduce the indoor temperature, which could be controlled within 40 °C. The results of this study provide a reference basis and technical guidance for the engineering projects of ventilation systems for indoor substations, which can effectively solve the problem of excessive indoor temperature caused by heat dissipation from substation equipment while providing a favorable guarantee for sustainable operation of the substation.

Wind tunnel experimental study on the influence of super-large natural ventilation cooling tower on the flow and diffusion of pollutants

ABSTRACT In this paper, a wind tunnel experiment was carried out to study the atmospheric flow and pollutant diffusion around a super-large natural ventilation cooling tower of a nuclear power plant. Considering the effect of the natural ventilation of the cooling tower, with the chimney as the center, X-type hot-wire probes were used to measure the average flow field and turbulence structure of the atmosphere around the cooling tower and other complexes, and pollutant diffusion studies were carried out by tracer experiments. The results show that the super-large natural ventilation cooling tower and its thermal plume emission have a significant effect on pollutant flow and diffusion, changing the trajectory of the plume. When the chimney is located upwind of the cooling tower, some pollutants are emitted secondly due to the entrainment effect through the cooling tower when the plume passes through the natural ventilation cooling tower, regardless of whether or not the cooling tower is operating. Compared with the cooling tower that does not operate, the thermal plume and natural ventilation effects generated by the cooling tower during operation cause the plume dispersion range to widen, the maximum concentration to decrease, and the impact on vertical diffusion to be more significant than that on horizontal diffusion.

Study on noise reduction and structural optimization of ventilated bio-metamaterial plates for acoustic applications

This study focuses on the noise reduction performance and structural optimization of ventilated metamaterial plates designed for bio-acoustic applications, where effective sound attenuation and ventilation are both crucial. Traditional soundproofing materials, which rely on mass and thickness, are inadequate for bio-acoustic environments that require lightweight and compact solutions. In contrast, bio-acoustic metamaterials use resonance effects to attenuate sound while maintaining necessary airflow selectively. This research evaluates multiple metamaterial plate configurations through computational simulations and experimental testing, examining their performance in terms of Sound Transmission Loss (STL), airflow rates, and von Mises stress. The results reveal that Plate Configuration 1 offers the highest STL at 39.14 dB but at the cost of lower airflow efficiency (0.69 m3/s) and increased structural stress (24.83 MPa). Plate Configuration 2 achieves the best airflow efficiency (0.82 m3/s) but with lower noise reduction (STL of 35.42 dB). Plate Configuration 3 provides a balanced performance, with moderate noise attenuation (STL of 37.89 dB), good airflow (0.75 m3/s), and structural stability (von Mises stress of 22.12 MPa). The study concludes that bio-acoustic metamaterials can be effectively optimized for different bio-acoustic applications by carefully tuning their geometry, making them suitable for eco-acoustics, wildlife monitoring, and medical devices where noise control and airflow are critical.

Aeration Optimization for the Biodrying of Market Waste Using Negative Ventilation: A Lysimeter Study

This study investigates the optimization of aeration rates for the biodrying of market waste using negative-pressure ventilation. Market waste, characterized by a high moisture content (MC) and rapid decomposition, presents challenges in waste management. Over 12 days, three aeration rates (ARs) of 0.2, 0.4, and 0.6 m3/kg/day were examined, and the most effective continuous ventilation configuration was identified in terms of heat generation, moisture reduction, and biodrying efficiency. The results indicate that the most effective AR for heat retention and moisture removal was 0.2 m3/kg/day, achieving a 6.63% MC reduction and a 9.12% low heating value (LHV) increase. Gas analysis showed that, while AR 0.2 supported high microbial activity during the initial 7 days, AR 0.6 sustained higher overall CO2 production due to its greater aeration rate. The findings also suggest that the biodrying of market waste with a high initial MC can achieve significant weight loss and leachate generation when paired with a high aeration rate of 0.6 m3/kg/day, with a 69.8% weight loss and increased waste compaction being recorded. The study suggests that variable ARs can optimize biodrying, making market waste more suitable for conversion to refuse-derived fuel or landfill pre-treatment and improving waste-to-energy processes and sustainability.

Long Term Ventilation in Pediatric Central Apnea: Etiologies and Therapeutic Approach over a Decade.

This retrospective study aimed to analyze the clinical characteristics, ventilatory strategies, and effectiveness of ventilation in pediatric patients with central apneas treated at the Sleep Medicine and Long-Term Ventilation Unit of the Bambino Gesù Children's Hospital in Rome from 2012 to 2022. Among all ventilated patients at our Center from January 2012 to December 2022, we retrospectively included children with a cAHI ≥ 1 events/h on baseline poly(somno)graphic study. Additional parameters assessed included the underlying disease, type of ventilation (non-invasive vs. invasive), age at ventilation onset, ventilation mode, and transcutaneous capnometry parameters. To assess the effectiveness of ventilation on central apneas, we compared the cAHI at baseline and on ventilation. Sixty-seven patients met the inclusion criteria for central apnea (cAHI > 1 events/h). Diagnoses included hypoxic-ischemic encephalopathy, 15 (22.4%); Ondine syndrome, 14 (20.9%); polymalformative syndrome, 10 (14.9%); Prader-Willi syndrome, 8 (11.9%); brain tumor, 6 (9.0%); Down syndrome, 4 (6.0%); ROHHAD syndrome, 2 (3.0%); other infrequent pathologies were, Arnold-Chiari II, primary central apnea, epilepsy, lisosomal diseases, hydrocephalus, myopathy, obesity, Rett Syndrome. Pressure-supported ventilation (PSV) was the most common mode used (45 out 67 patients, 67.2%), followed by pressure-controlled ventilation (PCV) (15 out 67 patients, 22.4%) and continuous positive airway pressure (CPAP) (7 out 67 patients, 10.4%). Statistically significant improvement (p < 0.05) in cAHI was observed in patients with polymalformative syndrome (3.5 vs. 0.3, p = 0.01), hypoxic-ischemic encephalopathy (3.1 vs. 0.1, p = < 0.01), and Prader-Willi syndrome (3.5 vs. 0.1, p = 0.03), while there was no significant improvementn in children with brain tumor (6.2 vs. 1.5, p = 0.21). Central apneas are present in children with various underlying pathologies. Ventilatory strategies tailored to the specific diagnosis and severity of central apneas yield significant improvements in cAHI. PSV was the preferred ventilation mode in this study and there was notable effectiveness across different diagnostic categories. PCV was employed in most severe cases. CPAP was exclusively used in patients with predominantly obstructive sleep apneas.

Point-of-Care Lung Ultrasound to Evaluate Lung Isolation During One-Lung Ventilation in Children: A Blinded Observational Feasibility Study.

Minimally invasive thoracic surgical techniques require effective lung isolation using one-lung ventilation (OLV). Verification of lung isolation may be confirmed by auscultation, visual confirmation using fiberoptic bronchoscopy (FOB), or more recently, point-of-care ultrasound (POCUS). The aim of this study was to prospectively compare lung ultrasound with clinical auscultation to confirm OLV before thoracic surgery in pediatric patients. This prospectively blinded feasibility study included 40 patients ranging in age from 0 to 20 years. After confirmation of lung separation by the primary anesthesia team using FOB, the sonographer and the auscultator, both blinded to the laterality of surgery and lung separation, entered the operating room. The sonographer evaluated for pleural lung sliding and the auscultator listened for breath sounds. Successful lung separation was definitively confirmed by direct visualization of lung collapse during the operation. In confirming effective single-lung ventilation, lung ultrasound had a diagnostic accuracy of 95% (95% confidence interval [CI], 82.7%-98.5%). In contrast, auscultation could only reliably confirm lung isolation with 68% accuracy (95% CI, 51.5%-80.4%). The McNemar test showed a statistically significant difference between the use of lung ultrasound and auscultation (P < .001). The median time to perform ultrasonography was 67 seconds (interquartile range [IQR], 46-142) and the median time to perform auscultation was 21 seconds (IQR, 10-32). Based on the initial results of our feasibility trial, lung ultrasound proved to be a fast and reliable method to verify single-lung ventilation in pediatric patients presenting for thoracic surgery with a high degree of diagnostic accuracy.

Comparing strategies for the mitigation of SARS-CoV-2 airborne infection risk in tiered auditorium venues

The COVID-19 pandemic demonstrated that reliable risk assessment of venues is still challenging and resulted in the indiscriminate closure of many venues worldwide. Therefore, this study used an experimental, numerical and analytical approach to investigate the airborne transmission risk potential of differently ventilated, sized and shaped venues. The data were used to assess the magnitude of effect of various mitigation measures and to develop recommendations. Here we show that, in general, positions in the near field of an emission source were at high risk, while the risk of infection from positions in the far field varied depending on the ventilation strategy. Occupancy, airflow rate, residence time, virus variants, activity level and face masks affected the individual and global infection risk in all venues. The global infection risk was lowest for the displacement ventilation case, making it the most effective ventilation strategy for keeping airborne transmission and the number of secondary cases low, compared to mixing or natural ventilation.

Manifestations of toxic pulmonary edema during respiratory support in an experiment

BACKGROUND: Currently, respiratory support is successfully used to treat pulmonary edema of non-toxic origin. The manifestations of pulmonary edema of non-toxic origin and toxic pulmonary edema have similar features, so respiratory support can be effective in treating the latter. AIM: To describe the manifestations of toxic pulmonary edema in rabbits and demonstrate the effectiveness of artificial pulmonary ventilation with support of positive end-expiratory pressure (PEEP) in case of severe intoxication with thermal destruction products of fluoroplastic-4. MATERIALS AND METHODS: Three rabbits were used in the study: rabbit N 1 (control), rabbit N 2 (intoxication) and rabbit N 3 (treatment). Rabbits N 2 and 3 were subjected to severe intoxication with thermal destruction products of fluoroplastic-4 (1,5 HLC50, 15 min). For treatment, rabbit N 3 (treatment), an hour after exposure, underwent mechanical ventilation with PEEP (pressure-controlled mode; oxygen fraction — 0,3; starting PEEP — 5 cm H2O, tidal volume — 20–25 ml). At various times, chest radiography was performed, oxygenation index, hemoglobin saturation (SaO2), and partial pressure of carbon dioxide in exhaled air (PetCO2) were determined. Posthumously, pathological changes in lung tissue, pulmonary coefficient were determined, and histological examination was performed. RESULTS: Exposure of rabbit N 2 (intoxication) to the thermal destruction products of fluoroplastic-4 led to the sequential formation of the interstitial and alveolar phases of toxic pulmonary edema, which contributed to its death 13 hours after exposure. As SaO2 decreased and PetCO2 increased (3 and 5 hours after exposure), in rabbit N 3 (treatment), during respiratory support, PEEP was increased twice by 2 cm H2O (maintaining a given respiratory volume), which led to the normalization of the studied parameters. On the 7th day after exposure, the condition of rabbit N 3 (treatment) did not differ from the condition of rabbit N 1 (control); no pathological changes in the respiratory system were detected. CONCLUSION: Carrying out mechanical ventilation with PEEP, started an hour after exposure (with a stepwise increase in PEEP as the condition worsens), is effective for correcting toxic pulmonary edema in rabbits caused by severe intoxication with the thermal destruction products of fluoroplastic-4.

Heterogeneous Treatment Effects of High-Frequency Oscillatory Ventilation for Acute Respiratory Distress Syndrome: A Post Hoc Analysis of the Oscillation for Acute Respiratory Distress Syndrome Treated Early (OSCILLATE) Trial.

We sought to evaluate whether different subgroups of adults with acute respiratory distress syndrome (ARDS) respond differently to high-frequency oscillatory ventilation (HFOV). The Oscillation for ARDS Treated Early (OSCILLATE) trial was a randomized controlled trial of HFOV vs. conventional ventilation that found an increased risk of in-hospital mortality (primary outcome) with HFOV. In a post hoc analysis, we applied three different approaches to evaluate heterogeneity of treatment effect for in-hospital mortality: 1) subgroup analyses based on baseline Pao2:Fio2 ratio and oxygenation index (OI); 2) a risk-based approach using a multivariable outcome prediction model; and 3) a clustering approach via multivariable latent class analysis. We used multivariable logistic regression models to assess for interaction. Thirty-nine ICUs, five countries. Five hundred forty-eight adults with moderate to severe ARDS. HFOV vs. conventional mechanical ventilation with low tidal volume and higher positive end-expiratory pressure. The effect of HFOV on in-hospital mortality was consistent across categories of Pao2:Fio2 ratio (adjusted odds ratio [aOR], 2.04; 95% CI, 1.32-3.17 and aOR, 1.16; 95% CI, 0.49-2.75 for groups with Pao2:Fio2 above or equal to 80, vs. below 80, respectively; interaction p = 0.23) and OI (aOR, 1.78; 95% CI, 0.67-4.70; aOR, 3.19; 95% CI, 1.44-7.09; aOR, 1.73; 95% CI, 0.82-3.65; and aOR, 1.33; 95% CI, 0.61-2.90 for quartiles of baseline OI, respectively; interaction p = 0.44). Point estimates for the effect of HFOV were consistent across risk categories (aOR, 2.44; 95% CI, 0.40-14.83; aOR, 1.69; 95% CI, 0.75-3.85; and aOR, 2.10; 95% CI, 0.59-7.54 for the lowest, moderate, and highest risk categories, respectively; interaction p = 0.32). Using a clustering approach, point estimates for HFOV were also consistent (cluster 1: aOR, 1.85; 95% CI, 1.15-3.00 and cluster 2: aOR, 1.75; 95% CI, 0.91-3.38; interaction p = 0.75). We did not identify heterogeneity in the effect of HFOV across different subgroups of patients with ARDS.

Experimental investigation of natural gas leakage and dispersion characteristics in utility tunnels under the effects of real facility layout and forced ventilation

Natural gas leakage occurring in underground utility tunnels usually poses a significant threat to public safety. In order to prevent unexpected fires and explosions, the evolution mechanism of natural gas leakage and dispersion in utility tunnels is urgently needed. In this study, an experimental apparatus was built to facilitate the understanding of leakage and dispersion dynamics in utility tunnels. Methane with a purity of 99.9% is used as a surrogate for natural gas. A schlieren imaging system with a Z-shaped optical path was designed to visualize the high-speed gas jet. The concentration distribution, alarm time, dilution efficiency, and gas jet image were analyzed under the effect of various facility layouts, ventilation, and leakage rates. The results show that the gas leakage and dispersion process can be divided into three zones: upwind zone, leak zone, and downwind zone, characterized by complicated airflow collision, high-speed get jets, and stable dilution dispersion respectively. Scenario analysis highlights the significance of key facilities, such as cable brackets, in experimental and numerical modeling due to their impact on dispersion trajectories. Higher ventilation rates prove beneficial in reducing peak concentration, hazardous areas, and enhancing purge efficiency. Conversely, higher leakage rates exacerbate the likelihood and severity of gas explosions. Alarm time exhibits a V-shaped distribution relative to the leak point, while purge time correlates positively with sensor positions. These findings are of practical importance in enhancing quantitative risk assessment and designing mitigation strategies for gas leakage accidents, which helps to improve the safety-risk-control capabilities of utility tunnels.

A Numerical and Experimental Study to Compare Different IAQ-Based Smart Ventilation Techniques

Maintaining indoor environmental quality in residential buildings is essential for occupants’ comfort, productivity, and health, with effective mechanical ventilation playing a key role in removing or diluting indoor pollutants. A two-week experimental campaign was conducted in an apartment in Lyon, France, known for its poor urban air quality, assessing temperature, relative humidity, CO2, and PM2.5 concentrations. A model verification study was performed to compare experimental measurements against numerical modeling in the living room and bedroom, leading to errors in the accuracy of the sensors. In addition, this study also investigates the impact of different ventilation strategies on indoor air quality. This research evaluates a baseline mechanical exhaust-only ventilation approach with constant air volume against two innovative smart ventilation approaches: mechanical exhaust-only ventilation with humidity control and mechanical exhaust-only ventilation with room-level CO2 and humidity control. A key contribution of this research is the novel coupling of multizone simulation models (DOMUS and CONTAM) with a CFD tool to refine pressure coefficients on the building façade, which enhances the accuracy of indoor air quality predictions. The smart ventilation strategies showed improvements, including a 20% reduction in CO2 concentration and a 5% reduction in the third-quartile PM2.5 concentration, highlighting their effectiveness in enhancing ventilation and pollutant dilution. This research provides valuable insights into advanced ventilation strategies and modeling techniques in urban environments.

Comparative Study Of Proseal Laryngeal Mask Airway Versus Cuffed Endotracheal Tube In Patietns Undergoing Laparoscopic Cholecystectomy Under General Anesthesia

Background: LC is a surgical technique that uses a set of cameras and specially designed instruments to remove the gallbladder through a series of small abdominal incisions. Due to their low invasive nature, laparoscopic surgeries are considered day care procedures. As a result, patients undergoing laparoscopic procedures now get less invasive airway management, such as PLMA, rather than ETT. Nowadays, SADs are frequently employed in the control of airways, falling somewhere among tracheal tubes and face masks both in terms of structural placement and degree of invasiveness. These devices provide a hands-free approach to seal an airway against gas. The two most often utilized methods for managing airways are endotracheal intubation and LMA ProSeal The present study aimed to compare the efficacy and safety of ProSeal LMA with Endotracheal Tube in patients undergoing Laparoscopic Cholecystectomy under general anaesthesia. To compare ProSeal LMA and Endotracheal tube with respect to intra-operative haemodynamic responses in patients undergoing laparoscopic cholecystectomy under general anaesthesia. Materials and Methods: The study was carried out at the Department of Anaesthesiology, Katihar Medical College &amp; Hospital, Katihar, Bihar, study was done for 1 Year, 60 individuals were enrolled, Group S (Study Group) with 30 patients received ProSeal LMA (PLMA) with an introducer and Group C (Control Group) with 30 patients received a cuffed Endotracheal Tube (ETT). Every variable was subjected to statistical analysis within the same individual and between 2 treatment categories using a suitable biostatistical methodology. Results:. The PLMA required fewer attempts for successful insertion compared to ETT (1.63±0.49 vs 2.03±0.89, p=0.034). NGT insertion was quicker with PLMA compared to ETT. The PLMA group showed lower EtCO2 levels at multiple time points compared to the ETT group. The PLMA group had a lower incidence of sore throat and nausea but a higher incidence of airway trauma compared to the ETT group. The PLMA group had a higher rate of device removal without complications (93.3% vs 80%) and smooth postoperative recovery (90% vs 80%) compared to the ETT group. Conclusion: In conclusion, our study demonstrates that the ProSeal Laryngeal Mask Airway (PLMA) offers several advantages over the conventional cuffed Endotracheal Tube (ETT) in patients undergoing laparoscopic cholecystectomy under general anesthesia. The PLMA was associated with easier insertion, more stable hemodynamics, effective ventilation, and a smoother postoperative course

Effect of natural ventilation on aerosol transmission and infection risk in a minibus

High passenger density, prolonged exposure, and close interpersonal distance create a high infection risk (IR) in minibuses. While improving natural ventilation induced by turbulent airflows is essential for controlling IR in minibuses, comprehensive studies on its effectiveness are lacking. To address this, we conducted computational fluid dynamics simulations studies coupling indoor–outdoor turbulent airflows to examine the impact of window opening locations, window opening sizes, and initial droplet diameters (dp) on the ventilation airflow and dispersion of pathogen-laden droplets. Results show that the surrounding turbulent flow patterns create higher surface pressure at bus rear than bus front, which is a key factor influencing bus ventilation. When all windows are closed, ventilation is primarily provided by skylights at bus rooftops. Ventilation through only two skylights resulted in an air change rate per hour (ACH) of 17.55 h−1, leading to high IR of passengers. In contrast, fully opening front and rear windows increases ACH by 27.28-fold to 478.79 h−1, significantly reducing IR by 1–2 orders of magnitude compared to skylight ventilation. Expanding window opening sizes can effectively enhance ventilation when both front and rear windows open (attributed to the pumping effect), while is ineffective when only front windows open. To reduce IR in minibuses, we recommend opening multiple windows at the bus front and rear. Even if the total opening area of the front and rear windows is only two-thirds of that of the front window, its ACH is 2.8 times more than only opening front windows.

Discrete-event modeling of human behavior for spread of diseases on university campuses

The COVID-19 pandemic has highlighted the importance of defining sound policies to make attending workplaces safely. Sometimes, deciding on different policies is challenging as this highly depends on the behavior of the individuals. This research introduces a Discrete Event-based methodology and a prototype implementation to study such policies, including human behavior along with information about the workplace layout and building characteristics such as ventilation rate or room capacity. The method is based on a combination of agent-based models, diffusion processes and discrete-event simulation. We exemplify how to use this method using a case study based on Carleton University’s Campus, in which we use the methodology and tools to study the effect of ventilation, as well as the application of a policy where sick students are denied entry to the campus on the number of disease cases on campus.

Safety of Small-Diameter Endotracheal Tubes in Microlaryngeal Surgery.

Microlaryngeal surgeries require unique considerations for airway management to facilitate patient safety and adequate surgical exposure. Small-diameter endotracheal tubes (ETTs) are widely used but have raised concerns regarding patient safety, including questions about the potential for barotrauma, effective ventilation, and adequate oxygenation. We hypothesize that small ETTs will prove to be safe in a variety of cases. We conducted a case series analyzing the safety of 5.0 ETTs in microlaryngeal surgeries at Washington University School of Medicine from November 2020 to November 2023. Outcome measures included intraoperative desaturations (SpO2 < 90% for >2 min), high peak inspiratory pressures (PIPs) (>40 cm H2O), and prolonged extubation times (>15 min). Univariate regression models were used to analyze associations of sociodemographic and clinical variables with these outcome measures. This study included 76 small-ETT microlaryngeal surgeries. There were 5 instances of desaturations, no reported incidents of barotrauma, and no cases in which intraoperative tube exchange was required due to issues with oxygenation or ventilation. Median PIP was 38 cm H2O, with a range of 17-78 cm H2O. 46% of patients had a PIP above 40 cm H2O. There were prolonged extubation times in 14% of procedures. No association was shown between sociodemographic and clinical variables with risk of desaturations, high PIPs, or prolonged extubation times. Our study suggests that 5.0 ETTs are safe for microlaryngeal surgery in a variety of patients. Otolaryngologists and anesthesiologists should consider this information when choosing between the multiple available options for airway management during microlaryngeal surgery. Level 4 Laryngoscope, 2024.