Impact of Indoor-Outdoor Temperature Difference on Building Ventilation and Pollutant Dispersion within Urban Communities

Mechanical ventilation consumes a huge amount of global energy. Natural ventilation is a crucial solution for reducing energy consumption and enhancing the capacity of atmospheric self-purification. This paper evaluates the impacts of indoor-outdoor temperature differences on building ventilation and indoor-outdoor air pollutant dispersion in urban areas. The Computational Fluid Dynamics (CFD) method is employed to simulate the flow fields in the street canyon and indoor environment. Ventilation conditions of single-side ventilation mode and cross-ventilation mode are investigated. Air change rate, normalized concentration of traffic-related air pollutant (CO), intake fraction and exposure concentration are calculated to for ventilation efficiency investigation and exposure assessment. The results show that cross ventilation increases the air change rate for residential buildings under isothermal conditions. With the indoor-outdoor temperature difference, heating could increase the air change rate of the single-side ventilation mode but restrain the capability of the cross-ventilation mode in part of the floors. Heavier polluted areas appear in the upstream areas of single-side ventilation modes, and the pollutant can diffuse to middle-upper floors in cross-ventilation modes. Cross ventilation mitigates the environmental health stress for the indoor environment when indoor-outdoor temperature difference exits and the personal intake fraction is decreased by about 66% compared to the single-side ventilation. Moreover, the existence of indoor-outdoor temperature differences can clearly decrease the risk of indoor personal exposure under both two natural ventilation modes. The study numerically investigates the building ventilation and pollutant dispersion in the urban community with natural ventilation. The method and the results are helpful references for optimizing the building ventilation plan and improving indoor air quality.

Assessing the Asynchrony Event Based on the Ventilation Mode for Mechanically Ventilated Patients in ICU

Respiratory system modelling can assist clinicians in making clinical decisions during mechanical ventilation (MV) management in intensive care. However, there are some cases where the MV patients produce asynchronous breathing (asynchrony events) due to the spontaneous breathing (SB) effort even though they are fully sedated. Currently, most of the developed models are only suitable for fully sedated patients, which means they cannot be implemented for patients who produce asynchrony in their breathing. This leads to an incorrect measurement of the actual underlying mechanics in these patients. As a result, there is a need to develop a model that can detect asynchrony in real-time and at the bedside throughout the ventilated days. This paper demonstrates the asynchronous event detection of MV patients in the ICU of a hospital by applying a developed extended time-varying elastance model. Data from 10 mechanically ventilated respiratory failure patients admitted at the International Islamic University Malaysia (IIUM) Hospital were collected. The results showed that the model-based technique precisely detected asynchrony events (AEs) throughout the ventilation days. The patients showed an increase in AEs during the ventilation period within the same ventilation mode. SIMV mode produced much higher asynchrony compared to SPONT mode (p < 0.05). The link between AEs and the lung elastance (AUC Edrs) was also investigated. It was found that when the AEs increased, the AUC Edrs decreased and vice versa based on the results obtained in this research. The information of AEs and AUC Edrs provides the true underlying lung mechanics of the MV patients. Hence, this model-based method is capable of detecting the AEs in fully sedated MV patients and providing information that can potentially guide clinicians in selecting the optimal ventilation mode of MV, allowing for precise monitoring of respiratory mechanics in MV patients.

The Effect of Volume Controlled and Pressure Controlled Ventilation Modes on Cerebral Oximetry and Blood Gas Status in Laparoscopic Cholecystectomy, A Randomized Controlled Trial

Background: To compare the volume-controlled and pressure-controlled ventilation modes with near infrared spectroscopy (NIRS) cerebral oximetry and blood gas status in laparoscopic cholecystectomyMethods: Seventy patients (n=70), who underwent elective laparoscopic cholecystectomy operation were randomized into two groups (volume control ventilation - group V, pressure control ventilation - group P). Demographic data (age, gender, body mass index) and operative data (anesthesia, surgery, and insufflation durations) were recorded. Patients’ single derivation electrocardiogram, pulse oximetry, non-invasive arterial pressure, NIRS cerebral oximetry and end-tidal CO2 parameters were recorded. Measurements were done at the start of anesthesia (T0), at the end of intubation (T1), 5 minutes after the insufflation (T2), at the time just before desufflation (T3) and 5 minutes after desufflation (T4).The patients’ heart rate, systolic and diastolic arterial pressure, saturation of pulse oximetry, and NIRS values were recorded for time points. Additionally, arterial gas results and mechanical ventilation parameters were recorded as well. Results: No significant difference was found in age, sex, body mass index. Operation, anesthesia and insufflation durations were similar for the groups. In Group P, NIRS right T1-2-3 averages and NIRS left T2-3 averages were significantly higher than Group V (p=0.030, p=0.001, p=0.001, p=0.006, p=0.002 respectively). In Group P T1-T2-T4, mean peak pressures and mean plateau pressures were significantly lower than Group V (p=0.003, p=0.001, p<0.001, p=0.011, p=0.001, p<0.001 respectively).Conclusion: Mechanical ventilation that performed in pressure-control ventilation mode is resulted with better tissue oxygenation than volume-control ventilation mode. In pressure-control ventilation mode, peak pressure and plateau pressure were lower.Registration of study at ClinicalTrials.gov was made at 25/01/2021 with the NCT04723043 number.

Ventilation Conversion Mechanisms in Karst Caves

Ventilation modes in karst caves are of great significance for exploring issues regarding "carbon sources and sinks" in karst areas. Therefore, this study conducted continuous monitoring of air temperature, humidity, and CO2 concentrations inside and outside the Dafeng cave in Suiyang, Guizhou from August 2015 to July 2020 in order to comprehensively analyze each element using a systematic analysis method. The results revealed that: (1) the Dafeng cave is mainly divided into three ventilation modes: ① during summer and autumn, the inside of the cave is mainly in a restricted ventilation mode, wherein air exchange inside and outside the cave is suppressed, and the CO2 concentration in the cave easily forms a cumulative effect; ②during winter, the inside of the cave is mainly in an active ventilation mode, wherein there is strong air exchange, and the CO2 concentration inside the cave is close to that outside the cave; ③ during spring, due to the variable climate and rising temperature, the inside of the cave gradually transitions from an active to restricted ventilation mode and the air exchange intensity gradually changes. The isotope data change characteristics outside the cave at the Yemingzhu monitoring site verifies the ventilation mode of the tunnel during each season. (2) Due to the influence of tourists, air changes inside and outside the cave, and the structure of the tunnel, there may be multiple ventilation modes within a single season. Tourists and tunnel structure primarily affect the structure of the tunnel. A change in the air environment outside the cave mainly affects the virtual temperature outside the cave, increasing or reducing the virtual temperature difference between the inside and outside of the cave, thereby affecting the ventilation mode. Thus, our study suggests that more consideration should be given to changes in external climate or weather conditions when studying the conversion mechanism of karst cave ventilation modes.

Survival Predictors of Preterm Neonates - Single Center Experience.

Introduction: Adequate prenatal and postnatal care for preterm neonates not only affects the survival rate, but also the occurrence of chronic diseases, and in the future also affects the quality of life of that children. Aim: To examine the influence of independent predictors (weeks of gestation, body weight, sex) on the outcome of the disease and to analyze the influence of the applied ventilatory mode on the final outcome of treatment. Material and methods: The study included neonates (n = 248) born prematurely who were treated in the neonatal intensive care unit for a period of one year due to immaturity-related difficulties. Results: The mean age of male neonates (n = 119) at birth was 31.13 ± 3.3 weeks of gestation (WG), and females (n = 129) 31.59 ± 3.2 WG. Weeks of gestation have a statistically significant effect on survival (p = 0.0001), for each more week of gestation, the chances of survival increase by 21%. There was no significant difference between birth weight and sex (p = 0.289), and the birth weight of the neonates had a statistically significant effect on survival (p = 0.0001). For every 10 grams of body weight, in our sample, the chance of survival increases by 2%. Ventilation mode showed a statistically significant effect on neonatal survival (p < 0.05), and intubation mode was used as an indicator. If neonates are switched from non-invasive to invasive ventilation mode, the chance of survival in our sample is reduced by 88%. Conclusion: Weeks of gestation, birth weight, and the use of a noninvasive mode of ventilation are predictors of a positive outcome for preterm neonates.

Noninvasive High-Frequency Shock Ventilation Based on Chest X-Ray Reconstruction Algorithm for Neonatal Respiratory Distress Syndrome

Objective. To explore the use of the noninvasive high-frequency oscillatory ventilation and CPAP ventilation mode in the treatment of neonatal respiratory distress syndrome and to compare the treatment effect and the incidence of complications and whether it can reduce the time to go to the hospital and the number of hospital stays. Methods. Seventy-four children with RDS treated in hospital were selected and divided into the noninvasive high-frequency group (NHFV group, 36 children) and noninvasive positive pressure ventilation group (NCPAP group, 38 cases), and they were compared with the changes in arterial blood gas, the occurrence of complications, and the time on the machine before and after the operation on 12, 24, 48, and 72 hours. Results. In the NHFV group, PO2, a/APO2, and SaO2 were higher than those in the NCPAP group at 12, 24, 48, and 72 h after the respiratory support was given, and the differences were statistically significant (all P < 0.05 ). PaCO2 in the NHFV group was given respiratory support. After support, the results at 12, 24, 48, and 72 h were lower than those in the NCPAP group, and the difference was statistically significant (both P < 0.05 ). The children in both groups were cured and discharged from the hospital, with air leakage, persistent pulmonary hypertension, and bronchopulmonary dysplasia; there were no statistically significant differences in the incidence of complications such as retinopathy, pulmonary hemorrhage, and intracranial hemorrhage ( P > 0.05 ). The NHFV group had less tracheal intubation, operation time, and hospital stays than the NCPAP group. The differences were significant. Statistical significance was at P < 0.05 . Conclusion. Noninvasive high-frequency ventilation is effective in the treatment of RDS, and compared with the CPAP ventilation mode, it can reduce CO2 retention, increase the oxygenation index, and reduce time of operation and length of hospital stay in children with RDS. It is worthy of clinical promotion and application.