Ventilation Flow Research Articles

Efficacy of High Flow Nasal Cannula in the Treatment of Patients with COVID-19 with Acute Respiratory Distress Syndrome: Results of Single Centre Study in Vietnam.

Most hospitalized patients required invasive or non-invasive ventilation and High Flow Nasal Cannula (HFNC). Therefore, this study was conducted to describe the characteristics of patients with severe Coronavirus Disease-2019 (COVID-19) treated by HFNC and its effectiveness for reducing the rate of intubated-mechanical ventilation in the Intensive Care Unit (ICU) of Phu Chanh COVID-19 Department-Binh Duong General Hospital. It was a cross-sectional and descriptive study. All severe patients with COVID-19 with acute respiratory failure eligible for the study were included. Patient characteristics, clinical symptoms, laboratory results, and treatment methods were collected for analysis; parameters and data related to HFNC treatment and follow-up were analysed. 80 patients, aged of 49.7 ± 16.6years, were treated with HFNC at admission in ICU. 14 patients had type 2 diabetes (17.5%), 3 patients had chronic respiratory disease (3.8%), 19 patients had high blood pressure (23.8%), and 5 patients with other comorbidities (7.4%). The majority of patients with severe COVID-19 had typical symptoms of COVID-19 such as shortness of breath (97.5%), intensive tired (81.3%), cough (73.7%), anosmia (48.3%), ageusia (41.3%), and fever (26.3%). The results of arterial blood gases demonstrated severe hypoxia under optimal conventional oxygen therapy (PaO2 = 52.5 ± 17.4mmHg). Respiratory rate, SpO2, PaO2 were significantly improved after using HFNC at 1st day, 3rd day and 7th day (P < 0.05; P < 0.05; P < 0.01; respectively). Receiver operating characteristics (ROC) index was significantly increased after treating with HFNC vs before HFNC treatment (4.79 ± 1.86, 5.53 ± 2.39, and 7.41 ± 4.24 vs 2.97 ± 0.39; P < 0.05, P < 0.05 and P < 0.01, respectively). 54 (67.5%) patients were success with HFNC treatment and 26 (32.5%) patients with HFNC failure needed to treat with Continuous Positive Airway Pressure (CPAP) (13 patients; 50%) or intubated ventilation (13 patients; 50%). HFNC therapy could be considered as a useful and effective alternative treatment for patients with acute respiratory failure. HFNC might help to delay the intubated ventilation for patients with respiratory failure and to minimise the risk of invasive ventilation complications and mortality. However, it is crucial to closely monitor the evolution of patient's respiratory status and responsiveness of HFNC treatment to avoid unintended delay of intubation-mechanical ventilation. An independent ethics committee approved the study (The Ethics Committee of Binh Duong General Hospital; No. HDDD-BVDK BINH DUONG 9.2021), which was performed in accordance with the Declaration of Helsinki, Guidelines for Good Clinical Practice.

Creation and Preclinical Testing of a Spirometer with Extended Functionality

RELEVANCE. We present the results of preclinical testing of an upgraded portable AR­1 gas flow analyzer produced by JSC Krasnogvardeets (Saint Petersburg) in order to create import-substituting technologies and develop practical and scientific spheres of healthcare.THE AIM OF THE STUDY. was to substantiate the possibility of clinical use of the upgraded device, originally intended for testing ventilators and inhalation anesthesia devices, as a monitor of the external respiration apparatus function.MATERIAL AND METHODS. The preclinical study of the upgraded gas flow analyzer was conducted at the V.A. Almazov National Medical Research Center in comparison with devices for conventional (Bellavista 950, Berner Ross Medical, Russia) and high-frequency (IPV-2C, Intrapulmonary Percussive Ventilation, Percussionaire Corporation, USA) mechanical ventilation in volume- and pressure-controlled modes using an artificial lung. The following reflected spirometry parameters were compared: tidal and minute volume under inhalation and exhalation, respiratory rate, maximum and minimum flows, peak and positive end expiratory pressure, fraction of inspired oxygen.RESULTS. A high accuracy of parameter matching shown by the gas flow analyzer and ventilators was demonstrated.CONCLUSION. The upgraded model of the gas flow analyzer can be used clinically as a portable spirometer at the prehospital and hospital stages.

Insights into turbulent airflow structures in blind headings under different ventilation duct distances

The paper explores the 3D stationary vortex structure of turbulent airflow near the dead-end face of a blind heading, ventilated via a forcing ventilation system. Despite its significance in blind heading ventilation, previous studies primarily focused on temporal dynamics of harmful impurities, overlooking flow structure details crucial for mass transfer processes. Our study delves into the ventilation flow structure across diverse parameters of the auxiliary ventilation system. Alongside standard flow visualization tools, we introduce three dimensionless indicators to comprehensively characterize flow structure, facilitating analysis of its variations with parameter changes and quantitative evaluation of system efficiency. Analysis revealed the formation of a single large-scale vortex within the entire range of considered ventilation system parameters in the heading. This vortex induces a significant increase in air circulation, approximately 2.5–3.5 times greater than airflow emerging from the ventilation duct’s end, thus intensifying mass transfer processes within the heading. We found that ventilation efficiency of the dead-end face zone in a blind heading with a 29.2 m² cross-section decreases linearly with increasing distance between the ventilation duct’s end and the dead-end face. However, compensating for this distance by increasing duct velocity is feasible, bearing significant implications for mine ventilation safety, particularly in ventilating blind headings with distant ducts from the dead-end face.

Lentinan combined with docetaxel and nedaplatin in the treatment of pulmonary tuberculosis complicated by nonsmall cell lung cancer

Purpose: To investigate the efficacy and safety of lentinan combined with docetaxel and nedaplatin (DN) in the treatment of pulmonary tuberculosis complicated by non-small cell lung cancer (NSCLC). Methods: A total of 100 patients diagnosed with pulmonary tuberculosis combined with NSCLC in Ankang People's Hospital, Ankang, China were randomized equally into study and control groups. Control group received standard anti-tuberculosis therapy and intravenous chemotherapy regimen based on docetaxel (75 mg/m² on day 1) and nedaplatin (80 – 100 mg/m²), while the study group received, in addition, lentinan (given intravenously every two days). The patients received a total of 2 courses of treatment. Tumor response, survival, adverse reactions, quality of life score, and pulmonary function indices were compared before and after treatment. Results: The study group showed significantly higher total response rate than the control group (p &lt; 0.05). Median overall survival and progression-free survival in the study group was significantly higher than in the control group (p &lt; 0.05). Also, the study group showed significantly lower incidence of adverse reactions compared to control group (p &lt; 0.05). Quality of life score, maximum voluntary ventilation (MVV) and peak expiratory flow (PEF) levels in the study group was significantly higher compared to control group (p &lt; 0.05). Conclusion: Lentinan combination with DN chemotherapy regimen improves response rate, prolongs survival, reduces incidence of adverse reactions, improves quality of life and pulmonary function in patients with pulmonary tuberculosis complicated by NSCLC. These findings provide a new perspective for future studies on the application of lentinan in the treatment of pulmonary tuberculosis complicated by NSCLC.

Night cooling by hybrid supply ventilation – analytical predictions of airflow rates and the ‘hybrid ventilation triangles’

Overheating in buildings can be mitigated during periods of excessively warm weather through the application of a night purge ventilation strategy. Building on the mathematical model of Waterson and Hunt (2024), we investigate the emerging field of hybrid ventilation – specifically the rates of airflow achieved by the simultaneous combination of ‘stack-driven’ natural displacement ventilation and a mechanical supply. Whilst the focus of Waterson and Hunt (2024) was specifically on predicting the time taken to complete a purge, herein we focus on airflow rates and in doing so elucidate the somewhat counter intuitive role that the mechanical supply has on the natural ventilation flow rates. Our results challenge the perception that a hybrid approach must be superior to both solely natural and mechanical strategies. Focusing on the variation in airflow rates during a hybrid purge, our model reveals: (i) a hybrid purge offers an improvement over a solely mechanical purge only during one of the two distinct flow regimes identified; and (ii) the manner in which the stack-driven and mechanical components combine is highly nuanced and cannot be predicted by the linear superposition of the constituent stack-driven and mechanical contributions.

Wind tunnel measurements of cross-ventilation flow in a realistic building geometry: Influence of building partitions and wind direction

Wind tunnel measurements have widely been used for validation of computational fluid dynamics simulations of natural ventilation airflows. However, the majority of such measurements employed simple generic single-zone buildings, while there is a lack of studies on realistic buildings including flow-critical geometrical features (e.g. internal partitions). To assess the effect of internal partitions at different incident flow angles (α = 0° and α = 30°), wind tunnel measurements of velocities in and around a cross-ventilated realistic residential building (with and without internal partition) were performed. Measurements were conducted at a geometric scale 1:40, using laser Doppler anemometry. Results indicate a large impact of the internal partition on indoor airflow distribution and resulting ventilation flow rates. For instance, for α = 0°, on the partitioned building side, regions of velocity increase (from ∼0 m/s to ∼80% of the outdoor reference velocity, Uref), but also regions of velocity decrease (from ∼50% of Uref to ∼0 m/s) were observed. The ventilation flow rate through the windows at the partitioned side decreased by 23% and 32%, respectively. For the partitioned building, a change from α = 0° to α = 30° resulted in regions of velocity increase from 0 m/s to ∼60% of Uref.

The post ICU trajectory: Post Acute and post ICU nutritional care

ICU survivors are growing but a persistent physical and mental disability may occur. The patients discharged from ICU are frequently malnourished and their medical nutritional support is impaired by oral intake limitation due to respiratory support such as non invasive ventilation or high flow nasal cannula oxygen therapy, dysphagia and difficulties to determine energy and protein targets. ICU acquired weakness must be recognized and could be minimized by better energy intake determined by indirect calorimetry, optimal protein intake and physical activity. Early physical activity has become a pivotal element of the improvement of the physical and cognitive condition in the post ICU.

Study on the diffusion and blocking behavior of bubble plumes in Cross-Flow

Abstract With the deepening of the concept of environmental protection, environmental problems in dredging engineering have attracted more and more attention. The diffusion of suspended particulate matter is inevitable in the process of dredging. A bubble plume, as a multiphase linear plume, has been widely studied because it can block the diffusion of suspended particulate matter in water. To explore the formation characteristics of the bubble plume, we evaluate the formation quality of the bubble plume qualitatively and quantitatively, analyze the effect of the bubble plume on blocking the diffusion of suspended particulates under different operating conditions (the type of bubble plume generation device, the number of bubble plume rows, and the ventilation flow rate) and environmental conditions (water flow velocity), and study the movement trajectory of blocked particles and blocked failed particles. A series of experiments on bubble plume characteristics and bubble plume blocking the diffusion of suspended particles were conducted to analyze the particle distribution characteristics and bubble plume blocking effect under the interaction of transverse flow and bubble plume. The results show that the better the quality of the bubble plume is, the lower the transverse flow intensity is, and the better the barrier effect of the bubble plume is.

CARETestLung: A mechanical test lung with Configurable airway Resistance, lung Elastance, and breathing efforts

A mechanical test lung is a crucial tool in accurately simulating patient-specific physiological responses of patients undergoing mechanical ventilation (MV), which, in turn, offer clinicians insight into lung mechanics during MV. In particular, it can be used to facilitate better methods to identify optimal ventilator settings, modes for individual patients by providing a platform to experiment with different MV settings. This addresses the challenge of optimising MV settings caused by variability in pathological conditions and the progression of respiratory disease over time within patients. However, the accessibility and cost of versatile test lungs limit widespread adoption in clinical settings, underscoring the need for affordable alternatives. This paper presents detailed instructions for the design and construction of a replicable, cost-effective mechanical test lung. The design features 3 subsystems: 1) the lung compartment; 2) the airway; and 3) a spontaneous breathing system. A detailed tests series shows its ability to replicate clinically realistic lung elastance values ranging from 25 to 85 cmH2O/L and airway resistance values from 10 to 45 cmH2O·s/L. It can also simulate a range of clinically realistic spontaneous breathing patterns. These capabilities yield pressure and flow ventilation data comparable to certified clinical test lungs across diverse scenarios, as well as matching clinically observed behaviours and dynamics. This accessible and versatile test lung offers valuable opportunities for optimising MV settings and advancing patient care, as well as its use in developing a range of physiological models for model-based decision support.

Mechanical power in decelerating flow versus square flow ventilation in pediatric ARDS.

Mechanical power (MP) is a summary variable quantifying the risk of ventilator-induced lung injury (VILI). The original MP equation was developed using square flow ventilation. However, most children are ventilated using decelerating flow. It is unclear whether MP differs according to mode of flow delivery. We compared MP in children with acute respiratory distress syndrome (ARDS) who received both square and decelerating flow ventilation. This was a secondary analysis of a prospectively enrolled cohort of pediatric ARDS. Patients were ventilated on decelerating flow, and then placed in square flow and allowed to stabilize. Ventilator metrics from both modes were collected within 24 hours of ARDS onset. Paired t-tests were used to compare differences in MP between the modes. We enrolled 185 subjects with a median oxygenation index of 9.5 (IQR 7, 13) and median age 8.3 years (IQR 1.8, 14). MP was lower in square flow (mean 0.46 J・min-1·Kg-1, SD 0.25, 95% CI 0.42-0.50) than in decelerating flow modes (mean 0.49 J・min-1·Kg-1, SD 0.28, 95% CI 0.45-0.53) with a mean difference of 0.03 J・min-1·Kg-1 (SD 0.08, 95% CI 0.014-0.038) (p<0.001). This result remained statistically significant when stratified by age < 2 years in square flow compared to decelerating flow and also when stratified by age >/= 2 years in square flow compared to decelerating flow. The elastic contribution in square flow was 70% and the resistive contribution was 30%. MP was marginally lower in square flow than in decelerating flow, although the clinical significance of this is unclear. Upward of 30% of MP may go towards overcoming resistance, regardless of age. This is nearly three-fold greater resistance compared to what has been reported in adults.

Modes of administration of nitric oxide devices and ventilators flow-by impact the delivery of pre-determined concentrations

BackgroundNitric oxide (NO) is a strong vasodilator, selectively directed on pulmonary circulation through inhaled administration. In adult intensive care units (ICU), it is mainly used for refractory hypoxemia in mechanically ventilated patients. Several medical delivery devices have been developed to deliver inhaled nitric oxide (iNO). The main purpose of those devices is to guarantee an accurate inspiratory NO concentration, whatever the ventilator used, with NO2 concentrations lower than 0.3 ppm. We hypothesized that the performances of the different available iNO delivery systems could depend on their working principle and could be influenced by the ventilator settings. The objective of this study was to assess the accuracy of seven different iNO-devices combined with different ICU ventilators’ flow-by to reach inspiratory NO concentration targets and to evaluate their potential risk of toxicity.MethodsWe tested seven iNO-devices on a test-lung connected to distinct ICU ventilators offering four different levels of flow-by. We measured the flow in the inspiratory limb of the patient circuit and the airway pressure. The nitric oxide/nitrogen (NO/N2) flow was measured on the administration line of the iNO-devices. NO and NO2 concentrations were measured in the test-lung using an electrochemical analyzer.ResultsWe identified three iNO-device generations based on the way they deliver NO flow: “Continuous”, “Sequential to inspiratory phase” (I-Sequential) and “Proportional to inspiratory and expiratory ventilator flow” (Proportional). Median accuracy of iNO concentration measured in the test lung was 2% (interquartile range, IQR -19; 36), -23% (IQR -29; -17) and 0% (IQR -2; 0) with Continuous, I-Sequential and Proportional devices, respectively. Increased ventilator flow-by resulted in decreased iNO concentration in the test-lung with Continuous and I-Sequential devices, but not with Proportional ones. NO2 formation measured to assess potential risks of toxicity never exceeded the predefined safety target of 0.5 ppm. However, NO2 concentrations higher than or equal to 0.3 ppm, a concentration that can cause bronchoconstriction, were observed in 19% of the different configurations.ConclusionWe identified three different generations of iNO-devices, based on their gas administration modalities, that were associated with highly variable iNO concentrations’ accuracy. Ventilator’s flow by significantly impacted iNO concentration. Only the Proportional devices permitted to accurately deliver iNO whatever the conditions and the ventilators tested.

The experimental and numerical studies of formation and collapse processes of ventilated supercavitating flow

The aim of this paper is to investigate the ventilated cavitating flow behavior, through experimental and numerical methods. The experiments are performed for a test model placed in a water tunnel and a high-speed camera is used to image the formation and collapse of the supercavity. For the numerical simulations, Ansys CFX commercial software is employed to solve the Reynolds-averaged Navier–Stokes (RANS) equations and additional transport equation for the liquid volume fraction in the unsteady condition. Both the experimental observation and numerical prediction show a hysteresis behavior for ventilated supercavity in which the value of the air entrainment coefficient required to maintain the supercavity in the formation process is less than the amount required to form it. The good agreement observed between the numerical prediction and experimental data, revealed the accuracy and capability of the numerical scheme. Also, the numerical simulation shows that the variations in the supercavity length, in addition to the air entrainment, are a function of the air leakage regime from the closure region of supercavity.

Numerical Investigation of Cross Ventilation Flow in A Gable Roof Building with Asymmetric Opening Positions

Natural ventilation can be a suitable alternative to mechanical ventilation as it is cost-effective and environmentally friendly. Therefore, an effective design of the natural ventilation system is very crucial. In this work, an attempt has been made to investigate the impact of opening positions and roof pitch on the performance of wind-induced cross-ventilation in a gable roof building. Numerical simulations were carried out using the computational fluid dynamics (CFD) technique based on the steady Reynolds averaged Navier-Stokes equations (RANS) model. Six configurations with asymmetric openings on opposite facades were considered to evaluate the effect of opening positions. Further, for studying the influence of roof pitch on the flow properties, three roof pitches, viz. 3:10, 5:10 and 7.5:10 were considered. It is found that the configuration with a windward opening in the middle and a leeward opening at the bottom (Configuration D) has the highest flow rate. The configuration with a windward opening at the top and a leeward opening at the bottom (Configuration B) has the lowest flow rate. Furthermore, the investigation with different roof pitches reveals that buildings with lower roof pitches are more vulnerable to wind loading due to higher flow separation at the windward eave. The investigation concludes that the opening position and roof pitch significantly influences the indoor airflow characteristics thereby affecting the ventilation performance.

Nasal high flow or noninvasive ventilation? navigating hypercapnic COPD exacerbation treatment: A randomized noninferiority clinical trial

BackgroundNoninvasive ventilation (NIV) has been the cornerstone for managing acute exacerbations of COPD (AECOPD) with hypercapnic respiratory failure. Nasal high flow (NHF) oxygen therapy has emerged as a potential alternative, offering a more tolerable modality with promising outcomes. The aim of the present study was to evaluate whether NHF respiratory support is noninferior to NIV with respect to treatment failure, in patients with mild-to-moderate hypercapnic AECOPD. MethodsIn this multi-center, randomized, noninferiority trial, 105 patients with AECOPD and respiratory failure type II were enrolled. Participants were randomly assigned to receive either NHF therapy or NIV. The primary endpoint was the frequency of treatment failure, defined as the need for intubation and invasive mechanical ventilation or a switch to the alternative treatment group. Secondary endpoints included changes in respiratory parameters, patient comfort indicators, and the occurrence of complications. ResultsThe findings revealed no significant difference in the primary outcome between the groups, with a treatment failure rate of 19.6 % (10 out of 51) in the NHF group and 14.8 % (8 out of 54) in the NIV group. Interestingly, NHF users reported significantly lower levels of dyspnea and discomfort at multiple follow-up points. Despite the differences in patient comfort, respiratory parameters such as respiratory rate, arterial blood gases, and use of accessory muscles of respiration showed no significant disparities between the groups throughout the study period. ConclusionsNHF therapy was similar to NIV in preventing treatment failure among patients with hypercapnic AECOPD, offering a viable alternative with enhanced comfort. Trial registrationThe study was prospectively registered in ClinicalTrials.gov (Identifier: NCT03466385) on March 15, 2018.

The flow regimes of two parallel-connected chambers respectively with a mechanical extractor and a buoyancy source

This research studies the ventilation flow patterns and density stratification in two parallel-connected chambers which respectively have a mechanical extractor and a localized buoyancy source. Two parallel-connected chambers are denoted as the forced and extracted chambers. The forced chamber having a continuous localized buoyancy source is located upstream, and the extracted chamber having a mechanical extractor is located downstream. Two chambers are interconnected by an internal connection opening and are connected to the exterior in a parallel manner through their own connection openings. The effects of the adjoining chamber having a mechanical extractor on the ventilation flow patterns and density stratification in the space are investigated in this study. The flow driving forces include the buoyant and inertial forces in this ventilated space. The buoyant force results from the buoyancy source, and the inertial force is due to the mechanical extractor. This research uses the theoretical analysis approach and the laboratory reduced-scale model to investigate this problem. This paper focuses on the ventilation flow patterns in the steady state and discusses different flow regimes due to the adjoining extracted chamber effect. The internal connection opening level and orientation between two chambers are discussed in this study. Three flow regimes, the small (or reduced), transition, and large (or enhanced) flow regimes, are found in two parallel-connected chambers and there is a range of critical flow rates to determine the flow regime when the internal connection opening is located in a partition wall as investigated in this research. If the internal connection opening is located in a horizontal ceiling, a clear-cut critical flow rate is expected and only two flow regimes exist. This study discusses the characteristics of different flow regimes in the space of two parallel-connected chambers. The paper presents three derived theoretical models and analogous salt-bath experimental results for three flow regimes, and comparisons between them show reasonable agreement.

Effects of longitudinal ventilation and GHEs on geothermal energy extraction and HRC in high geothermal tunnels

With the excavation of deep tunnels, the problem of high geothermal heat is becoming more and more prominent. However, high geothermal heat can be utilized as a renewable energy source. In order to effectively reduce thermal damage and utilize geothermal energy, it is necessary to study the effects of longitudinal ventilation and ground heat exchanges (GHEs) on the heat-regulating circle of the surrounding rock. In this study, an experimental platform was designed and constructed in a laboratory to test different geothermal heat exchanger flow rates and ventilation air velocities and to monitor the heat extraction from the geothermal heat exchanger, the ventilation heat extraction, and the temperature field of the surrounding rock. The experimental results show that when the temperature field tends to be stabilized, the flow rate and ventilation velocity of the GHEs are closely related to the temperature distribution of the surrounding rock. The initial heat storage and heat replenishment capacity of the enclosing rock have a great influence on the heat extraction efficiency. Ventilation has a great influence on the heat extraction efficiency of GHEs, and the optimal wind speed range is 1.5∼2 m/s considering the cooling and heat extraction efficiency. When the wind speed is less than 1.5 m/s, the heat extraction efficiency of GHEs can be improved, and the total heat transfer can be increased. When the wind speed is greater than 1.5 m/s, the situation is reversed. The thermal entropy theory for circular tunnels is not fully applicable to arched tunnels containing GHEs.

The similitude of indoor airflow in natural ventilation for a reduced-scale model: Investigation of nonisothermal flow fields by RANS simulation

Reduced-scale experiments and simulations are important approaches in natural ventilation research, and the similarity requirement is fundamental for generalising the flow characteristics obtained from reduced-to full-scale conditions. However, the similarity requirement of a nonisothermal natural ventilation flow in a reduced-scale model poses additional challenges because of the reduced approaching flow, which can potentially result in Reynolds dependence issues. This study investigated the Reynolds number (Re) independence of indoor airflow in natural ventilation under isothermal and nonisothermal conditions using computational fluid dynamics (CFD) with Reynolds-averaged Navier–Stokes. A wind tunnel experiment was first conducted to validate the accuracy of the CFD using a reduced-scale model. Indoor airflow fields characterised by the same Archimedes number (Ar) but with varying approaching wind velocities and temperatures were compared between the full-scale and 1/10 reduced-scale simulations. The dimensionless ventilation rate showed the least dependence on the Re number, while the temperature field was very sensitive to the Re number, especially in the near-wall region. However, the temperature field on the ventilation pathway is much less dependent on the Re number, the deviation of which is less than 10 % compared to the full-scale simulation. The temperature distribution in the reduced-scale simulation exhibits a thermal stratification pattern similar to that in the full-scale simulation.

Effects of Crosswinds on the Aerothermal Behaviour of a Double-Skin Façade

Abstract In double-skin facades, airflow is mainly induced by buoyancy forces due to temperature gradients and air compressibility. In practice, this passive system is also affected by ambient crosswind. The present work is focused on the analysis of the aerothermal behavior of an asymmetrically heated channel interacting with a transverse airflow. To achieve this, we utilized the computational fluid dynamics (CFD) technique based on the finite volume method to predict the system’s performance. After validating the adopted numerical model, we examined the flow structure for different channel widths, and we determined the corresponding ventilation flow rates. We integrated the effect of wind with the thermosiphon effect. The thermo-aerodynamic performance of the facade was presented as a function of wind velocities, which significantly influence the airflow through the cavity and its openings.

Assessing the predictors for paediatric intensive care unit for inter-hospital transfer patients on high-flow nasal cannula or continuous positive airway pressure ventilation at a tertiary Australian paediatric hospital.

The aim of the present study was to assess the predictors of need for paediatric intensive care unit (PICU) admission for inter-hospital transfer patients to a tertiary paediatric hospital ED on high flow (HF) or continuous positive airway pressure (CPAP) ventilation. Single-centre retrospective study of patients transferred to the state's tertiary paediatric hospital. Demographic information and disease management information was obtained. Between October 2021 and September 2022, 53 patients were transferred to the tertiary hospital on HF or CPAP. Of these, 23 required admission to PICU. Those admitted to PICU had a higher median fraction of inspired oxygen than those not admitted (0.4 vs 0.3, respectively, P = 0.013). Patients transported by road (vs flight) were more likely (20/23 patients, RR = 3.15, P = 0.016) to be admitted to PICU (56% vs 18%). Those who had received CPAP prior to or during transfer were more likely to require PICU admission (P = 0.012). We have demonstrated that children who require CPAP to manage their respiratory disease are more likely to require PICU care on transfer to the tertiary paediatric hospital. In addition, those patients being transferred from secondary metropolitan hospitals after a trial of HF are also likely to require PICU care. This suggests that these patients should be directly admitted to PICU, allowing for improved patient experience and flow as well as reducing unnecessary ED resource utilisation.

Exploration of the effect of hot smoke generated by tunnel fire on the ventilation flow field of jet fan

Abstract To reduce the hazard of hot smoke from tunnel fires, ventilation becomes a necessary control strategy. Uniform ventilation is the main method used in the study of tunnel fires, but it has obvious differences from the widely used jet fan ventilation in practice, and the two have different performances in controlling smoke. Therefore, the distribution of the upstream flow field with jet fan ventilation will be studied in a tunnel fire. Considering several parameters such as the HRR and the velocity of fan exit, numerical simulations were conducted to monitor the fire development by using a Fire dynamics simulator (FDS). The results suggest that the center-line velocity decay of a jet fan can be categorized into three regions: linear decay, power function decay, and stabilization. The decay coefficient (n) related to power function decay correlates with HRR, and therefore, a new prediction for the center-line velocity distribution of the jet fan is proposed. The predicted results correlate well with the available experimental data.