Ventilation Index Research Articles

Effects of roadside morphologies and moving vehicles on street canyon ventilation

The influence of roadside morphology and the movement of vehicles on street canyon ventilation is important, but their coupling effect is still unclear. This study aimed to determine the best structural design for roadside buildings while considering moving vehicles’ effect on ventilation. The morphologies examined were podium, cantilever, rain shed, balcony, outdoor air-conditioning unit, and reference structures. The ventilation capacity of partial areas and the entire lane in the sidewalk and cycle lane was analyzed based on the age of air and net escape velocity (NEV). When a vehicle moves through a street canyon, the ventilation capacity of the zone part at the rear of the vehicle is improved, especially for the cycle lane on the windward side. However, for the entire lane, moving vehicles reduce the ventilation capacity by about 0.2–1.4%, with an average reduction of 0.8%. Therefore, when a vehicle passed through the street canyon, it reduced the ventilation capacity of an entire lane under a perpendicular wind direction. The cantilever morphology exhibited the best ventilation based on the vortex distribution and ventilation indices analysis. Its NEV values were 5% higher than that of the reference.

A novel in-line high frequency interrupter for use with bubble CPAP: A feasibility study in a premature lamb model.

Recent in vitro testing of high frequency (HF) oscillation applied to bubble continuous positive airway pressure (BCPAP) using a novel flow interrupter device (HFI) demonstrated significantly improved CO2 washout while not altering delivered mean airway pressure (MAP) in a premature infant lung model. This study's aim was to evaluate the safety and efficacy of the HFI paired with BCPAP in an animal model of prematurity prior to clinical testing. Twelve fetal lambs, 131-135 days gestation, weight 3.51±0.42 kg, were delivered by Cesarean section. The lambs were supported by mechanical ventilation and weaned to spontaneous breathing with BCPAP at 6 cmH2O. A combined CO2/airflow sensor measured end-tidal (EtCO2) and tidal volume (VT). Blood gases, heart rate (HR), arterial pressure (Part), minute ventilation (MV), MAP, ventilatory efficiency index (VEI), thoracoabdominal phase angle and labored breathing index (LBI) were recorded over a 10-minute baseline period followed by four randomized 10-minute intervals with HFI set to either 8, 10, 12 or 15 Hz. EtCO2 decreased from baseline by 11.1±2.2SE%, 16.6±4.3SE%, 13.5±4.9SE%, and 19.5±4.5SE% at 8, 10, 12, and 15 Hz respectively (p < 0.001). Blood gases, SpO2, HR, Part, MAP, VT, MV, esophageal pressure, phase angle, and LBI underwent no significant change with HF. Respiratory rate decreased, and VEI increased, by 14.9±4.5SD% (p = 0.037) and 83±22SD% (p < 0.011) respectively, averaged over all frequencies. We demonstrated the safety and efficacy of a novel BCPAP flow interrupter device. HF applied to the respiratory system resulted in significantly improved CO2 clearance and ventilation efficiency with no deleterious physiological effects in a pre-term lamb model.

Exploring urban space quantitative indicators associated with outdoor ventilation potential

• Explores an urban form indicator associated with local outdoor ventilation potentials. • Provides a method for the correlation study between urban space form and regional spatial ventilation condition based on spatial partition. • Space partition method is an important factor that affects the degree of correlation between the SVF and ventilation index. • SVF could be an urban form parameter related to urban spatial ventilation for urban space. Urban ventilation conditions, which are significantly influenced by urban space forms, are essential for healthy and livable urban environments. In urban design practice, morphological indicators related to urban ventilation could be improved for the effective assessment of ventilation quality and timely adjustment of the design. This study attempted to explore local spatial morphological indicators related to ventilation performance. Considering the sky view factor ( SVF ) as a quantitative parameter of urban local spaces, this study investigated the correlation between the SVF and outdoor ventilation performance. The SVF was calculated using single and multipoint methods, and a wind velocity ratio <V*> was adopted as the spatial ventilation performance indicator. In addition, local spaces were defined using three different partition methods (GSP1, GSP2, and CSP), as the urban space is continuous and complex. A typical urban centre space in Nanjing, China, was adopted as the research subject. The wind flows were calculated using the computational fluid dynamics (CFD) method for two wind directions. The results showed a positive correlation between the SVF and ventilation indices. Different partitioning methods had a considerable impact on the correlation, as the value of R 2 between SVF and <V*> could reach around 0.3 in GSP1 and CSP but only 0.05 in GSP2.

Comparison of standard prophylactic, intermediate prophylactic and therapeutic anticoagulation in patients with severe COVID-19: protocol for the ANTICOVID multicentre, parallel-group, open-label, randomised controlled trial

IntroductionCOVID-19 induces venous, arterial and microvascular thrombosis, involving several pathophysiological processes. In patients with severe COVID-19 without macrovascular thrombosis, escalating into high-dose prophylactic anticoagulation (HD-PA) or therapeutic anticoagulation (TA) could...

Late Holocene centennial to millennial-scale variability in lower trophic level productivity off southern Hokkaido, Japan, and its response to dissolved iron-replete Coastal Oyashio dynamics

AbstractLittle is known about the dynamics of marine food chains spanning primary to higher trophic levels on centennial and longer timescales, especially where the supply of dissolved iron limits primary productivity. To elucidate the long-term dynamics of biological productivity in the Coastal Oyashio (CO), which is a major pathway for transporting dissolved iron into the western North Pacific from winter to spring, we reconstructed the lower trophic level productivity over the last 3000 years in the CO. Our results demonstrate that the concentrations and mass accumulation rates of both Chl-a (chlorophyll a and its derivatives) and biogenic opal used as proxies of primary productivity, and steryl chlorin esters (SCEs) used as that of zooplankton productivity, show a millennial-scale increasing trend and centennial-scale variability beginning ca. AD 400. SCEs were positively correlated with Chl-a, indicating that changes in zooplankton productivity were induced by bottom-up control of primary productivity. The Chl-a and SCEs showed synchronous centennial-scale patterns with a relative abundance of sea-ice-associated diatom species transported by CO, and with a ventilation index in the Okhotsk Sea Intermediate Water. This synchronous pattern indicates that lower trophic-level productivity during the spring bloom responded to the intensity of iron-replete CO.

Role of pyroptosis pathway related molecules in acute lung injury induced by gas explosion in rats

Objective: To explore the role and significance of pyroptosis in gas explosion-induced acute lung injury (ALI) in rats. Methods: In February 2018, 126 SPF male SD rats were selected and randomly divided into blank control group (18 rats) and experimental group (40 m, 80 m, 120 m, 160 m, 200 m and 240 m, 18 per group) . The experimental group carried out gas explosion in the roadway to build the ALI model, the control group did not carry out gas explosion, and other conditions were consistent with the experimental group. Respiratory function indexes such as respiratory frequency (f) , tidal volume (TV) , minute ventilation (MV) and airway stenosis index (Penh) were measured 24 hours after the explosion. 5 rats in each group were sacrificed after anesthesia, Hematoxylin-Eosin (HE) staining was used to observe the pathological morphology of lung tissue. Immunohistochemistry was used to detect the content of Caspase-1. Western blotting was used to detect the content of cell pyroptosis including nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) , Caspase-1, interleukin-1β (IL-1β) and interleukin-18 (IL-18) in lung tissue related protein expression. Results: The f and MV of rats in the experimental group were higher than those in the control group (P<0.05) . Except for the 40 m and 80 m groups, the TV of rats in the other experimental groups were higher than those in the control group (P<0.05) . Except for the 40 m group, the Penh of rats in the experimental groups were lower than those in the control group (P<0.05) . HE staining showed that the lung tissue of the experimental groups at different distance points showed obvious edema of the pulmonary interstitium and alveoli, a large number of red blood cells and inflammatory cells exuded in the alveolar space, thickening of the pulmonary interstitium, and increased lung injury score (P<0.05) . The results of immunohistochemistry showed that the positive expression of Caspase-1 in each experimental group was higher than that in the control group (P<0.05) . Western blotting results showed that the expression of pyroptosis-related proteins in each experimental group was higher than that in the control group (P<0.05) . Conclusion: Pyroptosis is involved in the pathophysiological process of gas explosion-induced ALI in rats.

Effect of 15° Reverse Trendelenburg Position on Arterial Oxygen Tension during Isoflurane Anesthesia in Horses.

Simple SummaryHorses commonly develop low blood oxygen levels during anesthesia, especially when they are placed on their backs. This study investigated whether a 15° head-up tilt, in a homogenous group of anesthetized horses positioned on their backs, would result in better blood oxygen levels as compared to no tilt. The results showed significantly greater blood oxygen levels with tilt compared to no tilt in five out of six horses tested. In one horse the effect was the opposite. The concurrent effect on cardiovascular function remains to be tested in detail. Further studies are needed to confirm these findings in a larger group of horses and to determine the effects on blood pressure and treatment options.Lower than expected arterial oxygen tension (PaO2) continues to be an unresolved problem in equine anesthesia. The aim of this randomized, crossover, and prospective study using six adult horses is to determine if a 15° reverse Trendelenburg position (RTP) increases PaO2 during inhalation anesthesia. Under constant-dose isoflurane anesthesia, dorsally recumbent horses were positioned either horizontally (HP) or in a 15° RTP for 2 h. Lungs were mechanically ventilated (15 mL/kg, 6 breaths/min). Arterial carbon dioxide tension (PaCO2), PaO2, inspired oxygen fraction (FiO2), and end-tidal carbon dioxide tension (EtCO2) were determined every 30 min during anesthesia. Indices of dead-space ventilation (Vd/Vt), oxygenation (P–F ratio), and perfusion (F–shunt) were calculated. Dobutamine and phenylephrine were used to support mean arterial pressure (MAP). Data are presented as median and range. In one horse, which was deemed an outlier due to its thoracic dimensions and body conformation, indices of oxygenation worsened in RTP compared to HP (median PaO2 438 vs. 568 mmHg; P–F ratio 454 vs. 586 mmHg, and F–shunt 13.0 vs. 5.7 mmHg). This horse was excluded from calculations. In the remaining five horses they were significantly better with RTP compared to HP. Results in remaining five horses showed that PaO2 (502, 467–575 vs. 437, 395–445 mmHg), P-F ratio (518, 484–598 vs. 455, 407–458 mmHg), and F-shunt (10.1, 4.2–11.7 vs. 14.2, 13.8–16.0 mmHg) were significantly different between RTP and HP (p = 0.03). Other variables were not significantly different. In conclusion, the 15° RTP resulted in better oxygenation than HP in dorsally recumbent, isoflurane-anesthetized horses, although worsening of oxygenation may occur in individual horses. A study detailing the cardiovascular consequences of RTP is necessary before it can be recommended for clinical practice.

Implementing a ventilation index for assessing indoor air PM2.5 concentrations in biomass-using households

Biomass combustion in indoor kitchens contributes a lot to the PM2.5 exposure burden among millions of people worldwide. Emitted potential pollutants from the biomass combustion oven may enormously degrade indoor air quality during cooking time and impact crowded rooms with inadequate indoor ventilation. The concept of developing a "ventilation index" may be a valuable alternative to assess indoor air quality. A new empirical formula of the ventilation index has been proposed recently, in which multiple studies need to be validated by various studies. This study is a part of the validation process and has ended up with supportive evidence-based insight into residential indoor air quality. Ninety-three households were selected from 25 villages of Tamil Nadu, India, to monitor the parameters required to apply in the empirical formula. However, the association between indoor air velocity and PM2.5 (considered a surrogate component of indoor air quality) was focused on emphatically. Other important variables, e.g., used amount of biomass cooking fuel, kitchen room index, room temperature, and relative humidity, were also monitored to observe the ventilation index. Indoor PM2.5 data were compared categorically with variable air velocities. Those who were using only biomass for cooking in indoor kitchens were recruited in the study. The air pollution exposure burden among the community population is expected to be minimized when the desired ventilation index is optimized and applied in configured kitchens and living rooms. Then, it may attract government policy to accept the ventilation index as a critical parameter for green housing schemes.

THE MAIN EPIDEMIOLOGICAL AND DIAGNOSTICAL FEATURES OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE IN SERVICEMEN OF THE ARMED FORCES OF UKRAINE IN THE CONDITIONS OF JOINT FORCES OPERATION

The aim: The aim of the work was to determine the leading epidemiological, diagnostical features, disturbance of spirometric indices, changes in the immune system in servicemen with COPD, who take part in Joint Forces Operation (JFO). Materials and methods: 89 male patients were examined, who sought medical help for COPD, group B. They were divided into two groups. 1 group (42 patients) − with COPD, who took part in the JFO not more than 6 month, the 2 group consisted of 47 patients with COPD, who took part in the JFO during the period more than 6 month. Results: The patients in the group 2 had veraciously more points of cough and sputum expectoration in daily amount of 30 and more ml. The type of sputum in 53.2% patients was predominantly mucus-pus. There were also more percentage of patients with feeling short of breath and the high point, achieved at CAT. There were significant differences in systolic and diastolic blood pressure levels, LV mass index between two groups. Conclusions: It was found that servicemen who took part in JFO for more than 6 months had a more severe course of COPD with a higher score in the CAT and probably lower obstructive ventilatory indices, in a probably higher percentage of cases there were detected such a concomitant pathology as AH stage II and GERD. They had Th17 immune response predomination with significant elevation of IL-17, TGF-β, IL-6 concentrations in serum and high concentration of soluble adhesion molecules. KEY WORDS: Obstructive ventilatory defects, immune, external respiration function, fuel combustion products

Studies of ventilation and thermal comfort in different wind tower-room configurations considering humidification for a warm climate of Mexico

Air conditioning systems in buildings demand a high energy consumption and will only be exacerbated by the threat of climate change, as coping with the increased temperatures will require a higher consumption of electricity for ventilation and cooling. The use of passive techniques to save energy and provide thermal comfort inside the buildings should be a priority for research. This work investigates the effectiveness of the passive natural ventilation system called the wind tower (windcatcher) to provide thermal comfort in a room without and with air humidification, for warm climatic conditions. The study was carried out using CFD considering three-dimensional turbulent flow for the continuous phase and a Lagrangian approach for the discrete phase. In addition, the parameters and indices of natural ventilation and thermal comfort were calculated. 54 different configurations of the wind tower and the room outlet window were evaluated. The influence of a chamfer in the tower and the optimization of water consumption in the humidifier were also investigated. The results showed that the selection of a suitable configuration and the use of a chamfer, can substantially improve ventilation and thermal comfort. In addition, the optimal mass flow rate for humidification that provides a sensation of neutral thermal comfort and minimal water consumption was found. The use of a wind tower and the application of humidification at the critical hours of the day, will provide thermal comfort throughout the day with a predicted percentage of dissatisfied lower than 10%. These results show that low energy consuming systems utilizing natural ventilation and air humidification in a wind tower-room system can be sufficient for appropriate cooling and thermal comfort.

Effect of Position Change From the Bed to a Wheelchair on the Regional Ventilation Distribution Assessed by Electrical Impedance Tomography in Patients With Respiratory Failure.

Background: There is limited knowledge about the effect of position change on regional lung ventilation in patients with respiratory failure. This study aimed to examine the physiological alteration of regional lung ventilation during the position change from lying in bed to sitting on a wheelchair.Methods: In this study, 41 patients with respiratory failure who were weaned from the ventilators were prospectively enrolled. The electrical impedance tomography (EIT) was used to assess the regional lung ventilation distribution at four time points (Tbase: baseline, supine position in the bed, T30min: sitting position in the wheelchair after 30 min, T60min: sitting position in the wheelchair after 60 min, Treturn: the same supine position in the bed after position changing). The EIT-based global inhomogeneity (GI) and center of ventilation (CoV) indices were calculated. The EIT images were equally divided into four ventral-to-dorsal horizontal regions of interest (ROIs 1–4). Depending on the improvement in ventilation distribution in the dependent regions at T60min (threshold set to 15%), the patients were divided into the dorsal ventilation improved (DVI) and not improved (non-DVI) groups.Results: When the patients moved from the bed to a wheelchair, there was a significant and continuous increase in ventilation in the dorsal regions (ROI 3 + 4: 45.9 ± 12.1, 48.7 ± 11.6, 49.9 ± 12.6, 48.8 ± 10.6 for Tbase, T30min, T60min, and Treturn, respectively; p = 0.015) and CoV (48.2 ± 10.1, 50.1 ± 9.2, 50.5 ± 9.6, and 49.5 ± 8.6, p = 0.047). In addition, there was a significant decrease in GI at T60min compared with Tbase. The DVI group (n = 18) had significantly higher oxygenation levels than the non-DVI group (n = 23) after position changing. ROI4Tbase was significantly negatively correlated with the ΔSpO2 (R = 0.72, p < 0.001). Using a cutoff value of 6.5%, ROI4Tbase had 79.2% specificity and 58.8% sensitivity in indicating the increase in the dorsal region related to the position change. The corresponding area under the curve (AUC) was 0.806 (95% CI, 0.677–0.936).Conclusions: Position change may improve the ventilation distribution in the study patients. The EIT can visualize real-time changes of the regional lung ventilation at the bedside to guide the body position change of the patients in the intensive care unit (ICU) and measure the effect of clinical practice.Trial Registration: Effect of Early Mobilization on Regional Lung Ventilation Assessed by EIT, NCT04081129. Registered 9 June 2019—Retrospectively registered. https://register.clinicaltrials.gov/prs/app/action/SelectProtocol?sid=S00096WT&selectaction=Edit&uid=U00020D9&ts=2&cx=v2cwij.

Ventilation improvement after pneumonia treatment evaluated with electrical impedance tomography: an observational study

Objective. Due to radiation exposure, not all patients with pneumonia receive chest x-rays or CT measurements to confirm treatment effectiveness. The aim of this study was to examine the ability to use electrical impedance tomography (EIT) to evaluate the treatment effectiveness in such patient group. Approach . A total of 35 consecutive patients with non-severe pneumonia were included in this prospective study. The patients received standard treatment according to our internal protocol. EIT measurements were performed in supine position before the treatment started and on day 6 of the treatment period. The EIT-based global inhomogeneity (GI) index and center of ventilation (CoV) index were calculated. The clinical pulmonary infection score (CPIS) was obtained at both time points. Main r esults. Clinically significant improvements in GI and CoV were found in the patient group (ΔGI: −34% ± 17% and ΔCoV: −10% ± 11%; p<0.001). Although the CPIS was also significantly improved (ΔCPIS −0.70 ± 0.17, p<0.001), no correlations were demonstrated when compared to ΔGI or ΔCoV. Significance. EIT demonstrated individual improvement of ventilation heterogeneity after standard treatment in non-severe pneumonia, and provided different information compared to CPIS. EIT has the potential to become a routine non-invasive, non-radiative tool to assess pneumonia treatment effectiveness.

The Effect of Physical Therapy on Regional Lung Function in Critically Ill Patients.

Early mobilization has become an important aspect of treatment in intensive care medicine, especially in patients with acute pulmonary dysfunction. As its effects on regional lung physiology have not been fully explored, we conceived a prospective observational study (Registration number: DRKS00023076) investigating regional lung function during a 15-min session of early mobilization physiotherapy with a 30-min follow-up period. The study was conducted on 20 spontaneously breathing adult patients with impaired pulmonary gas exchange receiving routine physical therapy during their intensive care unit stay. Electrical impedance tomography (EIT) was applied to continuously monitor ventilation distribution and changes in lung aeration during mobilization and physical therapy. Baseline data was recorded in the supine position, the subjects were then transferred into the seated and partly standing position for physical therapy. Afterward, patients were transferred back into the initial position and followed up with EIT for 30 min. EIT data were analyzed to assess changes in dorsal fraction of ventilation (%dorsal), end-expiratory lung impedance normalized to tidal variation (ΔEELI), center of ventilation (CoV) and global inhomogeneity index (GI index).Follow-up was completed in 19 patients. During exercise, patients exhibited a significant change in ventilation distribution in favor of dorsal lung regions, which did not persist during follow-up. An identical effect was shown by CoV. ΔEELI increased significantly during follow-up. In conclusion, mobilization led to more dorsal ventilation distribution, but this effect subsided after returning to initial position. End-expiratory lung impedance increased during follow-up indicating a slow increase in end-expiratory lung volume following physical therapy.

INFLUENCE OF SEX, AGE AND BODY MASS INDEX ON SOME FUNCTIONA INDICES OF PULMONARY VENTILATION IN PHYSICALLY ACTIVE CHILDREN

Purpose: The purpose of the present study is to examine the impact of age, sex and body mass index (BMI) on some indices of the pulmonary ventilation in healthy children actively practicing sport, between 11 and 14 years of age, living in Plovdiv, Bulgaria. Materials and methods: A group of 22 healthy volunteers (boys, n=14 and girls, n=8) with high level physical activity underwent a functional test for the evaluation of pulmonary ventilation. In order to assess the influence of age, BMI and sex on some indices of pulmonary ventilation, they were divided into the following groups: in accordance with the age - group 11-12 years old (n=14) and group 13-14 years old (n=8); in accordance with the BMI group &lt; 20 kg/m2 (n=14) and BMI group &gt;20 kg/m2 (n=8) and in accordance with the sex – boys group (n=14) and girls group (n=8). The results are presented as X±SD. The data has been analyzed with Independent Samples Test (t-test) (SPSS v. 13. 0). The difference at P&lt;0.05 was accepted as significant. Results: We did not find significant differences in most of the indices between the groups by age, body mass index and sex. Although there was higher maximum pulmonary ventilation and higher peak (maximal) expiratory flow in boys compared with the girls. Conclusion: Despite the good health condition and high level of physical activity, we found out higher maximum pulmonary ventilation and higher peak (maximal) expiratory flow in boys as compared with the girls.

Spatial and Temporal Variations in Atmospheric Ventilation Index Coupled with Particulate Matter Concentration in South Korea

The spatiotemporal variations in the atmospheric ventilation index (AVI) with the particulate matter (PM) concentrations in South Korea were investigated using a regional grid model derived from the National Center for AgroMeteorology and PM10 concentration data obtained from AirKorea and the Korea Meteorological Administration. To construct a high-resolution AVI database with 1 h time intervals and a spatial resolution of approximately 2.4 km, a medium-range prediction was performed using a regional model twice a week from December 2018 to November 2019. The resultant dataset was used to explore the seasonal patterns of the areal distribution of a novel index: Ventilation Index coupled with PM (VIP), defined by the ratio of the AVI to PM. To determine the effects of geography on the VIP, diurnal variations of the VIP were examined at three major cities in South Korea. The emphasis of the investigation was on major cities that are planned to be developed into smart cities. This study reveals the specific spatiotemporal structure of the AVI in South Korea for the first time at a high resolution and introduced the potential usefulness of the VIP. The results provide insights that could aid decision making for determining favorable locations for better air-quality cities on an annual basis and can enable the sustainable management of fine PM in and around the areas of interest.

Педагогічні передумови фізичної терапії хворих із пневмонією на стаціонарному етапі

Pneumonia cases go on taking primary places among diseases of breathing system at the present moment in the whole world which are leading among those that cause temporary loss of productivity. Besides mentioned, great part (up to 25 % of cases) and number of pneumonia complications gross is observed. Methods. The purpose of research is to analyze literature sources, set up and evaluate peculiarities of physical therapy of ill people with pneumonia at in-patient stage. To reach the set goals, theoretical analysis and summarizing of science literature data were used. Clinical development of illness was thoroughly studied. Evaluating the physical state of patient with pneumonia, we used peak flow metry and pneumotachometry, researched the function of external breathing - spirography, Shtange and Genche tests, muscles testing. Results. Treatment effectiveness criteria are full absence of inflammation process in lungs (absence of remaining changes in lungs tissue according to X-ray), abolishment of muscle misbalance, considerable improvement or normalization of ventilation index, increasing of hypoxia resistance. Course of therapeutic gymnastics has to include not less than 3-4 practices a day with rehabilitation therapist with further transferring to self-training. The following is recommended to patient during self-training:1) therapeutic gymnastics (breathing, relaxing exercises and isometric and post isometric relaxation of muscles) which is based on functional muscles testing results, researching of external breathing function, pulse oxymetry in the process of performing exercises during practices; 2)sport-applied exercises: dosed walking, riding bicycle trainer. Conclusion. Comprehensive program of treatment people with pneumonia at in-patient stage, which includes developed methodology of physical rehabilitation assisted, according to X-ray testing, faster finishing of inflammation process. Breathing exercises, chosen considering localization of process and peculiarities of changing in spirography index, and miocorrection assisted more distinct increasing of external breathing function and decreasing of patient’s muscle misbalance.

국부적 정체 기류 지표(역류량 지수) 제안과 구조형상 영향 분석

A traditional ventilation index (ACH: Air Change per Hour) is determined by the total volume and supply/exhaust flow rate. However, this index is not suitable to evaluate the local stagnant air flow. In this paper, a new index (κ: Reverse-flow rate index) is proposed by using a reverse-flow rate in order to indicate the local stagnant air flow quantitatively. In addition, the amount of local stagnant air flow is evaluated by the change of structural shape variables. The structural shape variables which induced an influence on the fluid flow are considered by the porosity (ρ) and the number of gaps (N ). As the result from the analysis of computational fluid dynamics (CFD), the performance of natural ventilation by the structural shape variables is similar, but there is a disparity for size of a local stagnant air flow by presence or absence of gaps. In addition, it is showed that the reverse-flow rate index has a tendency to increase the value with decreasing the value of porosity and the number of gaps each. Based on these performances, the approximated values of reverse-flow rate and the reverse-flow rate index are presented by a function of the porosity and the number of gaps through the regression of surface fitting.

Effect of greening on pollutant dispersion and ventilation at urban street intersections

To improve ventilation efficiency and reduce pollution concentration in urban spaces, eco-strategies, including greening, have been suggested. However, there is still very little evidence to assert the benefits of such greening options, particularly at urban street intersections. Therefore, in this work, air flow and pollutant dispersion within urban-like three-way, four-way, and roundabouts intersections are investigated with three simple and five combined greening layouts. Three-dimensional computational fluid dynamics (CFD) analysis using the Reynolds-averaged Navier–Stokes model was conducted considering multiple wind directions. The ventilation efficiency was evaluated using the ventilation indices purging flow rate (PFR) and net escape velocity (NEV). The investigation of simple greening layouts shows that shrubs alone may enhance increase ventilation (i.e., increase PFR and NEV), and trees could increase the pollutant concentration at the pedestrian level. A comparison of greening layouts combining trees and shrubs shows that the presence of greening reduces ventilation and worsens the pollution condition at street intersections, except for shrubs located in the central zone within roundabouts. Specifically, NEV decreases by 16%–43% at four-way and three-way intersections owing to the presence of greening. Greening layouts with two rows of trees located 2.2 m away from buildings show overall significant negative effects on ventilation, particularly for wind directions ϕ = 0°, 45°, and 90°. The impact of shrubs and trees on ventilation at the roundabout is less significant, with NEV varying by 4%–11%.

Characterizing respiratory parameters, settings, and adherence in real-world patients using adaptive servo ventilation therapy: big data analysis.

There is minimal guidance around how to optimize inspiratory positive airway pressure (IPAP) levels during use of adaptive servo ventilation (ASV) in clinical practice. This real-world data analysis investigated the effects of IPAP and minimum pressure support settings on respiratory parameters and adherence in ASV-treated patients. A United States-based telemonitoring database was queried for patients starting ASV between August 1, 2014 and November 30, 2019. Patients meeting the following criteria were included: United States-based patients aged ≥ 18 years; AirCurve 10 device (ResMed); and ≥ 1 session with usage of ≥ 1 hour in the first 90 days. Key outcomes were mask leak and residual apnea-hypopnea index at different IPAP settings, adherence and therapy termination rates, and respiratory parameters at different minimum pressure support settings. There were 63,996 patients included. Higher IPAP was associated with increased residual apnea-hypopnea index and mask leak but did not impact device usage per session (average > 6 h/day at all IPAP settings; 6.7 h/day at 95th percentile IPAP 25 cm H2O). There were no clinically relevant differences in respiratory rate, minute ventilation, leak, and residual apnea-hypopnea index across all possible minimum pressure support settings. Patients with a higher 95th percentile IPAP or with minimum pressure support of 3 cm H2O were most likely to remain on ASV therapy at 1 year. Our findings showed robust levels of longer-term adherence to ASV therapy in a large group of real-world patients. There were no clinically important differences in respiratory parameters across a range of pressure and pressure support settings. Future work should focus on the different phenotypes of patients using ASV therapy. Malhotra A, Benjafield AV, Cistulli PA, etal. Characterizing respiratory parameters, settings, and adherence in real-world patients using adaptive servo ventilation therapy: big data analysis. J Clin Sleep Med. 2021;17(12):2355-2362.

Nasal High Flow at 25 L/min or Expiratory Resistive Load Do Not Improve Regional Lung Function in Patients With COPD: A Functional CT Imaging Study.

BackgroundNasal high flow (NHF) is a non-invasive breathing therapy that is based on the delivery via a large-caliber nasal cannula of heated and humidified air at flow rates that exceed peak inspiratory flow. It is thought that positive airway pressure generated by NHF can help reduce gas trapping and improve regional lung ventilation. There are no data to confirm this hypothesis at flow rates applicable in stable chronic obstructive pulmonary disease (COPD) patients.MethodsIn this study, we used non-rigid registration of computed tomography (CT) images acquired at maximal expiration and inspiration to compute regional lung attenuation changes (ΔHU), and lung displacement (LD), indices of regional lung ventilation. Parametric response maps (Galban et al., 2012) were also computed in each experimental condition. Eight COPD patients were assessed at baseline (BL) and after 5 min of NHF and expiratory resistive loading (ERL).ResultsΔHU was: BL (median, IQR): 85 (67.2, 102.8); NHF: 90.7 (57.4, 97.6); ERL: 74.6 (46.4, 89.6) HU (p = 0.531); and LD: 27.8 (22.3, 39.3); 17.6 (15.4, 27.9); and 20.4 (16.6, 23.6) mm (p = 0.120) in the 3 conditions, respectively. No significant difference in trapping was observed. Respiratory rate significantly decreased with both treatments [BL: 17.3 (16.4, 18.9); NHF: 13.7; ERL: 11.4 (9.6, 13.2) bpm; and p < 0.001].ConclusionNeither NHF at 25 L/min nor ERL significantly improved the regional lung ventilation of stable COPD patients with gas trapping, based on functional lung CT imaging. Further study including more subjects is needed to assess the potential effect of NHF on regional lung function at higher flow rates.Clinical Trial Registrationwww.clinicaltrials.gov/under, identifier NCT03821311.