Space Ventilation Research Articles

Application of anti-inflammatory treatment in two different ovine Acute Respiratory Distress Syndrome injury models: a preclinical randomized intervention study

Whilst the presence of 2 subphenotypes among the heterogenous Acute Respiratory Distress Syndrome (ARDS) population is becoming clinically accepted, subphenotype-specific treatment efficacy has yet to be prospectively tested. We investigated anti-inflammatory treatment in different ARDS models in sheep, previously shown similarities to human ARDS subphenotypes, in a preclinical, randomized, blinded study. Thirty anesthetized sheep were studied up to 48 h and randomized into: (a) OA: oleic acid (n = 15) and (b) OA-LPS: oleic acid and subsequent lipopolysaccharide (n = 15) to achieve a PaO2/FiO2 ratio of < 150 mmHg. Then, animals were randomly allocated to receive treatment with methylprednisolone or erythromycin or none. Assessed outcomes were oxygenation, pulmonary mechanics, hemodynamics and survival. All animals reached ARDS. Treatment with methylprednisolone, but not erythromycin, provided the highest therapeutic benefit in Ph2 animals, leading to a significant increase in PaO2/FiO2 ratio by reducing pulmonary edema, dead space ventilation and shunt fraction. Animals treated with methylprednisolone displayed a higher survival up to 48 h than all others. In animals treated with erythromycin, there was no treatment benefit regarding assessed physiological parameters and survival in both phenotypes. Treatment with methylprednisolone improves oxygenation and survival, more so in ovine phenotype 2 which resembles the human hyperinflammatory subphenotype.

Simulation of the Gas Distribution Law and Operational Risk Analysis of a Vertical Gas Tank in a Ventilation State

As a type of airtight equipment, vertical gas tanks are prone to accumulations of toxic and harmful gases due to their poor ventilation and narrow space. This poses many safety hazards. Therefore, we conducted a FLUENT simulation for vertical gas tanks with different diameters. The results indicated that the larger the diameter, the longer the required ventilation time. It was necessary to monitor the gas concentration after ventilation for at least 6 h when the tank diameter was 2.6 m, after ventilation for at least 24 h when the tank diameter was 5.2 m, and after ventilation for at least 80 h when the tank diameter was 7.8 m. To ensure comprehensive monitoring, at least one monitoring point was required to be placed at the upper and lower ends of the vertical gas tank, respectively. Monitoring was initiated after these requirements were reached. A theoretical numerical analysis and an experimental verification analysis were conducted on the simulation results. The variation trend of the simulation value, the theoretical value, and the experimental test value were the same. The measured value of the ventilation duration was greater than the theoretical value of the ventilation duration and the simulation value of the ventilation duration. Therefore, the simulation results and theoretical analysis could be used for a risk analysis of gas tanks. The determination of ventilation characteristics via a simulation of vertical gas tanks has a practical significance when guiding on-site operations.

Achieving Green Airport Standards by Managing Indoor CO and CO2 Levels at Domestic Terminal of Banyuwangi Airport

Introduction: Green Airport is an airport development concept designed to be healthy. Excess levels of carbon monoxide (CO) and carbon dioxide (CO2) in the room can cause discomfort in the form of headache, nausea, vomiting, vertigo, and feeling confused and weak. This study aimed to determine the implementation of CO and CO2 control in rooms to achieve a green airport at Banyuwangi Airport.&#x0D; Materials and Methods: In this descriptive study, the obtained data were compared with related regulations. The physical and chemical quality of indoor air was measured at 85 points in three main rooms at risk using CO and CO2 detectors. Control was done through observing and measuring ventilation and detection systems in the entire occupied space.&#x0D; Results: The measurement results of CO and CO2 levels have met the specified threshold value below 29 ppm for CO and 5000 ppm for CO2. Physical quality measurements have not met the requirements for indoor temperature above 27.1°C and humidity above 60%. The assessment of ventilation aspects in the domestic terminal building of Banyuwangi Airport was achieved based on SNI 03-6572-2001 received 29 rooms or 74.3% of the rooms, 10 rooms that do not fit the ventilation system are toilet.&#x0D; Conclusion: The results of the assessment conducted show that there are still aspects that are not in accordance with the provisions of green buildings.

The effect of geometry and location of balconies on single-sided natural ventilation in high-rise buildings

The demand for housing and the expansion of urbanization have increased the price of land and vertical growth of buildings, resulting in converting the courtyard and porch to balconies. Nowadays, semi-open spaces, which play a critical role in providing optimal indoor air and thermal conditions, are neglected. In addition, the area of such spaces is regarded as limited and sometimes even the balcony is eliminated, leading to improper thermal behavior and increased energy consumption, while such elements can be used for better natural ventilation of spaces and utilization of natural energy, resulting in reducing energy consumption in addition to controlling the pressure created by the wind in the case of correct design. The purpose of the current paper is to evaluate the performance of balconies on the high-rise buildings using single-sided ventilation in the harsh hot-arid climate of Hamdan in Iran, which there has not been studied already A general basic model is presented according to field studies and criteria. Field survey indicates that most of the high-rise buildings in Hamedan have single-sided natural ventilation, as well as are located on the south side, have a rectangular shape, are enclosed on three sides, and have recessed balconies. Based on the climate data of Hamedan, July is considered the hottest month of the year, during which natural ventilation should be applied. Simulation is conducted by computational fluid dynamics (CFD) method and ANSYS software. Based on the results, 4.5 m width and 1.5 m depth are regarded as the best geometry of the balcony for Hamedan providing a mass flow rate up to 1.38 kg/s. In addition, the position of the balcony in the wall of the building should not be symmetrical. The usage of a balcony in the middle of the façade could provide higher ventilation rate and reduce cooling energy up to 7% compared with the base case. Through a meticulous balcony design, wind could path through the larger spaces then it is led towards the opposite window, and finally exits the building in a single-sided ventilation mode. This causes the air to flow in most of the interior spaces, leading to better ventilation than other methods.

Intrapulmonary distribution of blood flow during exercise in pulmonary hypertension assessed by a new combination technique.

Hyperventilation and inadequate cardiac output (CO) increase are the main causes of exercise limitation in pulmonary hypertension (PH). Intrapulmonary blood flow partitioning between ventilated and unventilated lung zones is unknown. Thoracic impedance cardiography and inert gas rebreathing have been both validated in PH patients for non-invasive measurement of CO and pulmonary blood flow (PBF), respectively. This study sought to evaluate CO behaviour in PH patients during exercise and its partitioning between ventilated and unventilated lung areas, in parallel with ventilation partitioning between ventilated and unventilated lung zones. Eighteen PH patients (group 1 or 4) underwent a cardiopulmonary exercise test (CPET) with a three-step loaded workload protocol. The steps occurred at 0%, 20%, 40%, and 60% of peak workload reached during a preliminary maximum CPET. Ventilatory parameters, arterial blood gases, CO, PBF, and intrapulmonary shunt (calculated as the difference between CO and PBF) were obtained at each step, combining thoracic impedance cardiography and an inert gas rebreathing technique. Dead space ventilation observed throughout the exercise was about 40% of total ventilation. A progressive increase of CO from 4.86 ± 1.24 L/min (rest) to 9.41 ± 2.63 L/min (last step), PBF from 3.81 ± 1.41 L/min to 7.21 ± 2.93 L/min, and intrapulmonary shunt from 1.05 ± 0.96 L/min to 2.21 ± 2.28 L/min was observed. Intrapulmonary shunt was approximately 20% of CO at each exercise step. Although the study population was small, the combined non-invasive CO measurement seems a promising tool for deepening our knowledge of lung exercise haemodynamics in PH patients. This technique could be applied in future studies to evaluate PH treatment influences on CO partitioning, since a secondary increase of intrapulmonary shunt is undesirable.

Real-world implementation and evaluation of a Model Predictive Control framework in an office space

In this work, Model Predictive Control (MPC) is experimentally implemented on a Heating, Ventilation and Air Conditioning (HVAC) system of a large-scale office space. As controller model, a physics-based Modelica building model is calibrated based on historic data pursuing an iterative, nonlinear optimization approach. For the calibration period with a horizon of seven weeks, the calibrated model exhibits a high model accuracy with a Root Mean Square Error (RMSE) of 0.49 °C between the measured and estimated room temperature. The MPC toolchain includes modules for state estimation and forecasts of disturbances quantities (such as outdoor temperature, solar radiation including calculation of the direct and diffuse fraction, supply temperatures and occupancy). The MPC execution comprises the operation of heating based on radiators and floor heating (via regulation of valve openings) as well as shading of three Venetian blind systems (via regulation of vertical position and slat inclination angle). The experiment is conducted during a heating period with a duration of three weeks from October 21 to November 11, 2022. The heating actuators are controlled considering their typical dynamics and take into account the night setback during unoccupied office periods. User acceptance of the automated shading control is included through additional cost function terms for the shading operation. The field test reveals the predictive control capabilities of the proposed MPC toolchain in a real-life scenario, demonstrating energy-efficient building operation and total average discomfort of 0.53 Kh/d. The MPC formulation provides flexibility regarding adjustability of the control towards energy efficiency, thermal comfort, daylight transmission and non-oscillating shading control. Finally, the disturbance forecast accuracies for outdoor temperature and the solar radiation quantities are evaluated and the MPC control performance is compared against a conventional control approach.

Minimizing indoor infection risks with automotive nanofiltration and with laminar vertical flow

The knowledge about nanoaerosols, their potential health effects, their measurement, limitation and administrative-legal treatment has been developed in the last 3 decades in connection with the exhaust gas cleaning of the combustion engines. Nanofiltration, which has thus become known, almost completely eliminates nanoparticles with filters of high durability, high specific filtration areas, and reasonable costs. On the occasion of the Covid pandemic, NanoCleanAir experimentally proved that the viruses in an automotive filter substrate are separated as well as the combustion particles and are also deactivated. To minimize cross exchange of infectious aerosol, new attention must be paid to flow management in ventilated spaces. Digitized flow analysis has also received significant inspiration from engine technology in the past. This paper provides information on some basic investigations and gives valuable advice based on the experimental and numerical results of a retrofitted classroom.

Towards the new generation of courtyard buildings as a healthy living concept for post-pandemic era

COVID-19 has laid a context for holistic research and practical approaches towards health issues in buildings. This study focuses on one particular residential building type, which is a combination of a modern apartment building with private double-oriented terraces, and a traditional courtyard building. This principle improves several aspects of healthy buildings and contributes to address indoor-outdoor interactions, daylighting, and the use of natural ventilation. The purpose of this study is to determine the factors underlying a particular type of semi-outdoor space within building forms and to explain their microclimatic behavior in buildings. One solid model and twelve porous apartment buildings with different numbers of porous sides, and terrace widths are evaluated using computational fluid dynamics. The k–ε turbulence model is adapted to simulate airflow in and around a four-story building. CFD simulations were validated against the wind-tunnel measurements. Investigations indicated that increasing the number of porous sides reduces the internal mean and maximum ages of air by -15.75 and -36.84%, which means improved ventilation performance. However, it leaves a negative trace on ventilation of the semi-outdoor spaces. Meanwhile, increasing the width of the terraces enhances the ventilation performance by reducing the mean age of air in units, courtyards, and terraces by -20%, -20%, and -9%, respectively.

3D modelling and simulation of the impact of wearing a mask on the dispersion of particles carrying the SARS-CoV-2 virus in a railway transport coach

Even though the Covid-19 pandemic seems to be stagnating or decreasing across the world, a resurgence of the disease or the occurrence of other epidemics caused by the aerial dissemination of pathogenic biological agents cannot be ruled out. These agents, in particular the virions of the Covid-19 disease, are found in the particles originating from the sputum of infected symptomatic or asymptomatic people. In previous research, we made use of a three-dimensional Computational Fluid Dynamics (CFD) model to simulate particle transport and dispersion in ventilated semi-confined spaces. By way of illustration, we considered a commuter train coach in which an infected passenger emitted droplets (1 and 10 µm) and drops (100 and 1000 µm) while breathing and coughing. Using an Eulerian approach and a Lagrangian approach, we modelled the dispersion of the particles in the turbulent flow generated by the ventilation of the coach. The simulations returned similar results from both approaches and clearly demonstrated the very distinct aerodynamics of the aerosol of airborne droplets and, at the other end of the spectrum, of drops falling or behaving like projectiles depending on their initial velocity. That numerical study considered passengers without protective masks. In this new phase of research, we first used literature data to develop a model of a typical surgical mask for use on a digital manikin representing a human. Next, we resumed the twin experiment of the railway coach, but this time, the passengers (including the infected one) were provided with surgical masks. We compared the spatial and temporal distributions of the particles depending on whether the spreader passenger wore a mask at all, and whether the mask was perfectly fitted (without leaks) or worn loosely (with leaks). Beyond demonstrating the obvious value of wearing a mask in limiting the dissemination of particles, our model and our simulations allow a quantification of the ratio of particles suspended in the coach depending on whether the infected passenger wears a mask or not. Moreover, the calculations carried out constitute only one illustrative application among many others, not only in public transport, but in any other public or private ventilated space on the basis of the same physical models and digital twins of the places considered. CFD therefore makes it possible to estimate the criticality of the occupation of places by people with or without a mask and to recommend measures in order to limit aerial contamination by any kind of airborne pathogen, such as the virions of Covid-19.

Increased Dead Space Ventilation as a Contributing Factor to Persistent Exercise Limitation in Patients with a Left Ventricular Assist Device.

(1) Background: The exercise capacity of patients with a left ventricular assist device (LVAD) remains limited despite mechanical support. Higher dead space ventilation (VD/VT) may be a surrogate for right ventricular to pulmonary artery uncoupling (RV-PA) during cardiopulmonary exercise testing (CPET) to explain persistent exercise limitations. (2) Methods: We investigated 197 patients with heart failure and reduced ejection fraction with (n = 89) and without (HFrEF, n = 108) LVAD. As a primary outcome NTproBNP, CPET, and echocardiographic variables were analyzed for their potential to discriminate between HFrEF and LVAD. As a secondary outcome CPET variables were evaluated for a composite of hospitalization due to worsening heart failure and overall mortality over 22 months. (3) Results: NTproBNP (OR 0.6315, 0.5037-0.7647) and RV function (OR 0.45, 0.34-0.56) discriminated between LVAD and HFrEF. The rise of endtidal CO2 (OR 4.25, 1.31-15.81) and VD/VT (OR 1.23, 1.10-1.40) were higher in LVAD patients. Group (OR 2.01, 1.07-3.85), VE/VCO2 (OR 1.04, 1.00-1.08), and ventilatory power (OR 0.74, 0.55-0.98) were best associated with rehospitalization and mortality. (4) Conclusions: LVAD patients displayed higher VD/VT compared to HFrEF. Higher VD/VT as a surrogate for RV-PA uncoupling could be another marker of persistent exercise limitations in LVAD patients.

Field performance of a solar air heater used for space heating and ventilation – A case study in New Zealand primary schools

New Zealand (NZ) primary schools are often inadequately ventilated in winter. The majority of NZ schools do not have mechanical ventilation systems. Surveys conducted prior to COVID-19 pandemic showed that only 30% of teachers were regularly opening windows in winter. Therefore there is a need to study an affordable alternative ventilation method. This research was conducted to investigate the space heating and ventilation performance of a roof-mounted solar air heater (SAH) in NZ primary schools in winter. Field experiments over two winters were carried out in Palmerston North, NZ. A SAH was installed on the sun-facing roof of four schools in winter 2013 and six schools in winter 2014. During the experiment, the air temperature and air velocity were measured inside the classroom at the SAH outlet. Ambient weather conditions were measured by a local climate monitoring station. Across all schools and two winters, when the SAH was operated at 75% of the maximum fan speed, a mean (standard deviation, SD) level of the air temperature difference between the SAH outlet and inlet was 16.6 (10.4) °C, the mean (SD) volumetric flow rate of the outlet air was 34.0 (12.9) m3·h-1, and the mean (SD) level of thermal efficiency was 16 (11)%. Results showed that operating a roof-mounted SAH increased the indoor temperature and was useful to supplement the natural ventilation flow rate. This is the first study to investigate the field performance of a roof-mounted SAH in NZ primary schools. Results of this study provide insights for the use of solar energy without need for energy storage to heat and ventilate the classrooms.

Ventilatory Effects of Isoflurane Sedation via the Sedaconda ACD-S versus ACD-L: A Substudy of a Randomized Trial.

Devices used to deliver inhaled sedation increase dead space ventilation. We therefore compared ventilatory effects among isoflurane sedation via the Sedaconda ACD-S (internal volume: 50 mL), isoflurane sedation via the Sedaconda ACD-L (100 mL), and propofol sedation with standard mechanical ventilation with heat and moisture exchangers (HME). This is a substudy of a randomized trial that compared inhaled isoflurane sedation via the ACD-S or ACD-L to intravenous propofol sedation in 301 intensive care patients. Data from the first 24 h after study inclusion were analyzed using linear mixed models. Primary outcome was minute ventilation. Secondary outcomes were tidal volume, respiratory rate, arterial carbon dioxide pressure, and isoflurane consumption. In total, 151 patients were randomized to propofol and 150 to isoflurane sedation; 64 patients received isoflurane via the ACD-S and 86 patients via the ACD-L. While use of the ACD-L was associated with higher minute ventilation (average difference (95% confidence interval): 1.3 (0.7, 1.8) L/min, p < 0.001), higher tidal volumes (44 (16, 72) mL, p = 0.002), higher respiratory rates (1.2 (0.1, 2.2) breaths/min, p = 0.025), and higher arterial carbon dioxide pressures (3.4 (1.2, 5.6) mmHg, p = 0.002), use of the ACD-S did not significantly affect ventilation compared to standard mechanical ventilation and sedation. Isoflurane consumption was slightly less with the ACD-L compared to the ACD-S (-0.7 (-1.3, 0.1) mL/h, p = 0.022). The Sedaconda ACD-S compared to the ACD-L is associated with reduced minute ventilation and does not significantly affect ventilation compared to a standard mechanical ventilation and sedation setting. The smaller ACD-S is therefore the device of choice to minimize impact on ventilation, especially in patients with a limited ability to compensate (e.g., COPD patients). Volatile anesthetic consumption is slightly higher with the ACD-S compared to the ACD-L.

The influence of ventilation on indoor air quality in buildings with variable pollutant emissions

Indoor Air Quality (IAQ) assurance is done mainly through the air exchange between interior and exterior. Lack of adequate ventilation of indoor spaces causes poor air quality and a higher incidence of sick building syndrome (SBS), which is manifested by affecting the comfort and wellbeing in the indoor spaces. Ensuring high energy performance buildings and indoor air quality is efficiently approached by limiting emissions from sources, by partial neutralization of the pollutants or by smarter ventilation. The concept of smart ventilation was developed to ventilate properly while reducing energy loads, allow for the provision of grid services, and promote associated renewable power integration. The above-mentioned information can be obtained by the air quality modelling, using mathematical approaches to predict the way pollutants behave in a certain environment or time scale. The paper presents the results obtained by mathematical modelling of indoor air quality, by including the transfer of pollutants from external sources and variable indoor emissions. The considered pollutants are ozone (O3), particulate matter (PM2.5), formaldehyde (HCHO) and carbon dioxide (CO2), due to the significant adverse effects on human health and their different preponderantly sources: indoor, outdoor or both indoor and outdoor. The main goal of our researches is the reducing of the amount of energy that ventilation uses while maintaining or improving IAQ.

Comparative study regarding retrofitting with a low GWP refrigerant in an ice rink with energy recovery implementation

The authors make a comparative study between an existing R407C indirect refrigeration system which serves an ice rink refrigeration plant with a modern R744 indirect refrigeration system incorporating heat recovery, by using “Pack Calculation Pro” software. The proposed solution involves no alterations in the water-ethylene glycol circuit that ensures the rink’s cooling load. By considering the need for retrofitting to comply with current legislation, the study aims to identify the best solution in terms of environmental impact and the CO2-equivalent release into the atmosphere. The recovered energy can be further used for space heating, ventilation, and domestic hot water preparation. This study is targeted on an existing ice rink placed in Iasi, Romania, and the analysis demonstrates that the implementation of this solution reduces the environmental impact of CO2-equivalent reduction, and the global COP (Coefficient of Performance) value increases.

Discussion of digital transition impact on the facility management sector applied to healthcare buildings.

Since 2020, the rapid global spread of the COVID-19 pandemic has generated unprecedented impacts on the management of hospital buildings, namely: (i) providing space for patients, medical staff, and equipment storage, (ii) imposition of limitations on access by the teams responsible for managing the building, (iii) adapting the space and its functionality quickly, (iv) ensuring continuous control of air quality and adequate ventilation of spaces, (v) development of digital tools for management, and (vi) assets monitoring in real-time. In addition, hospital buildings facilities’ deterioration rate is typically higher than in other buildings, enhanced by the fact that these facilities are open 24 hours a day, year-round. Thus, facilities management (FM) assumes a vital role in the future of healthcare facilities. FM is expected to grow at a 5% annual rate for 2021-2028, representing an acceleration of the industry at a global level. Furthermore, Industry 4.0 may positively impact the FM processes. As a new industrial revolution, providing a set of new approaches and tools will increase the efficiency of operations, significantly impacting the potential of optimization. These trends can improve planning and management of scope, costs, environment, and safety in the value chain of projects and assets, thus creating a more resilient and sustainable industry. Based on a literature review, this paper contributes to the discussion of the questions: How can the digital transition improve the management of the operation and maintenance of infrastructure in healthcare facilities? What is the legacy for FM teams in this post-COVID-19 management of hospital buildings?

Shedding Light on Latent Pulmonary Vascular Disease in Heart Failure With Preserved Ejection Fraction

BackgroundAmong patients with heart failure with preserved ejection fraction (HFpEF), a distinct hemodynamic phenotype has been recently described, ie, latent pulmonary vascular disease (HFpEF-latentPVD), defined by exercise pulmonary vascular resistance (PVR) >1.74 WU. ObjectivesThis study aims to explore the pathophysiological significance of HFpEF-latentPVD. MethodsThe authors analyzed a cohort of patients who had undergone supine exercise right heart catheterization with cardiac output (CO) measured by direct Fick method, between 2016 and 2021. HFpEF-latentPVD patients were compared with HFpEF control patients. ResultsOut of 86 HFpEF patients, 21% qualified as having HFpEF-latentPVD, 78% of whom had PVR >2 WU at rest. Patients with HFpEF-latentPVD were older, with a higher pretest probability of HFpEF, and more frequently experienced atrial fibrillation and at least moderate tricuspid regurgitation (P < 0.05). PVR trajectories differed between HFpEF-latentPVD patients and HFpEF control patients (Pinteraction = 0.008), slightly increasing in the former and reducing in the latter. HFpEF-latentPVD patients displayed more frequent hemodynamically significant tricuspid regurgitation during exercise (P = 0.002) and had more impaired CO and stroke volume reserve (P < 0.05). Exercise PVR was correlated with mixed venous O2 tension (R2 = 0.33) and stroke volume (R2 = 0.31) in HFpEF-latentPVD patients. The HFpEF-latentPVD patients had had higher dead space ventilation during exercise and higher PaCO2 (P < 0.05), which correlated with resting PVR (R2 = 0.21). Event-free survival was reduced in HFpEF-latentPVD patients (P < 0.05). ConclusionsThe results suggest that when CO is measured by direct Fick, few HFpEF patients have isolated latent PVD (ie, normal PVR at rest, becoming abnormal during exercise). HFpEF-latentPVD patients present with CO limitation to exercise, associated with dynamic tricuspid regurgitation, altered ventilatory control, and pulmonary vascular hyperreactivity, portending a poor prognosis.

Historical and urban-planing development оf the Pryvokzalnii district of Chernivtsi

Historical and urban-planing development оf the Pryvokzalnii district of Chernivtsi

Alveolar target ventilation and dead space in children under anaesthesia: The proventiped cohort study.

Ventilator settings in children under anaesthesia remain difficult because of the changes in the physiology and the high dead space. To determine the alveolar minute-volume to sustain normocapnia in children under mechanical ventilation. A prospective observational study. This study was performed between May and October 2019 in a tertiary care children's hospital. Children between 2 months and 12 years, weighing between 5 and 40 kg, admitted for general anaesthesia. Volumetric capnography was used to estimate the alveolar and dead space volume (Vd). Total and alveolar minute ventilation in (ml kg-1 min-1) over 100 breaths. Sixty patients were included comprising 20 per group: 5 to 10 kg (group 1), 10 to 20 kg (group 2), 20 to 40 kg (group 3). Seven patients were excluded for aberrant capnographic curves. After normalisation to weight, the median [IQR] tidal volume per kilogram was similar between the three groups: 6.5 ml kg-1 [6.0 to 7.5 ml kg-1], 6.4 ml kg-1 [5.7 to 7.3 ml kg-1], 6.4 ml kg-1 [5.3 to 6.8 ml kg-1]; P = 0.3. Total Vd (in ml kg-1) was negatively correlated to weight (r = -0.62, 95% confidence interval -0.41 to -0.76, P < 0.001). The total normalised minute ventilation (ml kg-1 min-1) to obtain normocapnia was higher in group 1 than in group 2 and in group 3; 203 ml kg-1 min-1 [175 to 219 ml kg-1 min-1], 150 ml kg-1 min-1 [139 to 181 ml kg-1 min-1] and 128 ml kg-1 min-1 [107 to 157 ml kg-1 min-1]; P < 0.001 (mean ± SD), but (mean ± SD) alveolar minute ventilation was similar between the three groups; 68 ± 21 ml kg-1 min-1. Total dead space volume (including apparatus dead space) represents a major component of tidal volume in children less than 30 kg, when using large heat and moisture exchanger filters. The total minute ventilation necessary to achieve normocapnia decreased with increasing weight, while the alveolar minute ventilation remained constant. ClinicalTrials.gov, identifier: NCT03901599.

Establishment and digital simulation of upper airway in patients with adenoid hypertrophy

Objective: To analyze the flow field characteristics of the upper airway in patients with different adenoid hypertrophy using computational fluid dynamics (CFD). Methods: From November 2020 to November 2021, the cone-beam CT (CBCT) data of 4 patients [2 males and 2 females,age range 5-7 years, mean (6.0±1.2) years] with adenoid hypertrophy who were hospitalized in the Department of Orthodontics and the Department of Otolaryngology at Hebei Eye Hospital were selected. The degree of adenoid hypertrophy in the 4 patients was divided into normal S1 (A/N<0.6), mild hypertrophy S2 (0.6≤A/N<0.7), moderate hypertrophy S3 (0.7≤A/N<0.9) and severe hypertrophy S4 (A/N≥0.9) according to the ratio of adenoid thickness to the width of nasopharyngeal cavity (A/N). The CFD model of the upper airway was established using ANSYS 2019 R1 software, and the internal flow field of the CFD model was numerically simulated. Eight sections were selected as observation and measurement planes for flow field information. Relevant flow field information includes airflow distribution, velocity variation, and pressure variation. Results: In the S1 model, the maximum pressure difference occurred in the 4th and 5th observation planes (ΔP=27.98). The lowest pressures and the maximum flow rates of S2 and S3 were located in the 6th observation plane. The airflow in S1 and S2 models completely passed through the nasal cavity. In the S3 model, the mouth-to-nasal airflow ratio was close to 2∶1. In S4 model, the airflow completely passed through the mouth; in the S1 and S2 models, hard palates were subjected to a downward positive pressure with a pressure difference of 38.34 and 23.31 Pa, respectively. The hard palates in S3 and S4 models were subjected to a downward negative pressure with a pressure difference of -2.95 and -21.81 Pa, respectively. Conclusions: The CFD model can objectively and quantitatively describe the upper airway airflow field information in patients with adenoid hypertrophy. With the increasing degree of adenoid hypertrophy, the nasal ventilation volume gradually decreased, whereas the oral space ventilation volume gradually increased, and the pressure difference between the upper and lower surfaces of the palate gradually decreased until the pressure became negative.

A clinical study of mastoid ventilation tube in tympanoplasty

Background: A ventilated middle ear space is an essential component of a functioning middle ear transformer mechanism. A mastoid ventilation tube (MVT) placed post-aurally in the antrum near the aditus is used in this study for the benefit of improvement in results of tympanoplasty. In support of this concept, very few experimental documents are reported. Aims and Objectives: The aims of this study were to find out if the MVT has any effect on the outcome of tympanoplasty in cases of chronic suppurative otitis media (CSOM) tubo-tympanic disease. Materials and Methods: This study was performed in 50 cases which were selected from the total number of cases using stratified random sampling method. In the research, patients with CSOM, who did not respond to medical therapy and required a combined approach tympanoplasty, were enrolled. Patients who needed just myringoplasty and those found to have cholesteatoma intraoperatively were not included in the research. Results: The study showed significant improvement in graft uptake, air-bone closure, and hearing in cases with MVT, thus resulting in better success rate in cases with MVT than cases without MVT. Furthermore, most of the cases had sclerosed mastoids and very few cases had complications such as MVT block and post-operative discharge. Conclusion: The MVT had a beneficial effect on the final outcome of combined approach tympanoplasty in cases of CSOM tubo-tympanic type active stage.