Ventilation Index Research Articles

換気効率指標Net Escape Velocityを用いた不均一濃度場の形成構造解明に関する研究 : 第1報-Net Escape Velocityの定義及びRANSモデルによる解析

換気効率指標Net Escape Velocityを用いた不均一濃度場の形成構造解明に関する研究 : 第1報-Net Escape Velocityの定義及びRANSモデルによる解析

換気効率指標Net Escape Velocityを用いた不均一濃度場の形成構造解明に関する研究 : 第2報-3次元流れ場・汚染物質拡散へのNEVの適用

換気効率指標Net Escape Velocityを用いた不均一濃度場の形成構造解明に関する研究 : 第2報-3次元流れ場・汚染物質拡散へのNEVの適用

換気効率指Net Escape Velocityを用いた不均一濃度場の形成構造解明に関する研究 第3報-各種の局所換気装置を対象とした空気質制御問題へのNEV適用

換気効率指Net Escape Velocityを用いた不均一濃度場の形成構造解明に関する研究 第3報-各種の局所換気装置を対象とした空気質制御問題へのNEV適用

In Vivo Evaluation of the Acute Pulmonary Response to Poractant Alfa and Bovactant Treatments in Lung-Lavaged Adult Rabbits and in Preterm Lambs with Respiratory Distress Syndrome.

Poractant alfa (Curosurf®) and Bovactant (Alveofact®) are two animal-derived pulmonary surfactants preparations approved for the treatment of neonatal respiratory distress syndrome (nRDS). They differ in their source, composition, pharmaceutical form, and clinical dose. How much these differences affect the acute pulmonary response to treatment is unknown. Comparing these two surfactant preparations in two different animal models of respiratory distress focusing on the short-term response to treatment. Poractant alfa and Bovactant were administered in a 50-200 mg/kg dose range to surfactant-depleted adult rabbits with acute respiratory distress syndrome induced by lavage and to preterm lambs (127-129 days gestational age) with nRDS induced by developmental immaturity. The acute impact of surfactant therapy on gas exchange and pulmonary mechanics was assessed for 1 h in surfactant-depleted rabbits and for 3 h in preterm lambs. Overall, treatment with Bovactant 50 mg/kg or Poractant alfa 50 mg/kg did not achieve full recovery of the rabbits' respiratory conditions, as indicated by significantly lower arterial oxygenation and carbon dioxide values. By contrast, the two approved doses for clinical use of Poractant alfa (100 and 200 mg/kg) achieved a rapid and sustained recovery in both animal models. The comparison of the ventilation indices of the licensed doses of Bovactant (50 mg/kg) and Poractant alfa (100 mg/kg) showed a superior performance of the latter preparation in both animal models. At equal phospholipid doses, Poractant alfa was superior to Bovactant in terms of arterial oxygenation in both animal models. In preterm lambs, surfactant replacement therapy with Poractant alfa at either 100 or 200 mg/kg was associated with significantly higher lung gas volumes compared to Bovactant treatment with 100 mg/kg. At the licensed doses, the acute pulmonary response to Poractant alfa was significantly better than the one observed after Bovactant treatment, either at 50 or at 100 mg/kg dose, in two animal models of pulmonary failure.

A Statistical Investigation of the Dependence of Tropical Cyclone Intensity Change on the Surrounding Environment

A progression of advanced statistical methods is applied to investigate the dependence of the 6-h tropical cyclone (TC) intensity change on various environmental variables, including the recently developed ventilation index (VI). The North Atlantic (NA) and western North Pacific (WNP) observations from 1979 to 2014 are used. As a first step, a model of the intensity change is developed as a linear function of 13 variables used in operational models, obtaining statistical R2 values of 0.26 for NA and 0.3 for WNP. Statistical variable selection techniques are then applied to significantly reduce the number of predictors (to 5–11), while keeping similar R2 values with linear or nonlinear models. Further reduction of the number of predictors (to 5–7) and significant improvement of R2 (0.41–0.53) are obtained with mixture modeling, indicating that the dependence of TC intensification on the environment is nonhomogeneous. Applying VI as the environmental predictor in the mixture modeling gives R2 results (0.41–0.74) similar to or better than those with more environmental variables, confirming that VI is a dominant environmental variable, although its effect on TC intensification is quite heterogeneous. However, the overall predictive R2 results of the mixture models are relatively low (<0.3), as the considered environmental variables have limited predictability for the occurrence of extreme/rapid intensification. Finally, nonparametric regression with six predictors [current intensity, previous intensity change, the three components of VI (maximum potential intensity, shear, and entropy deficit), and 200-hPa zonal wind] performs relatively well with predictive R2 values of 0.37 for NA and 0.36 for WNP. The predictability of these statistical models may be further improved by adding oceanic and inner-core process predictors.

Anaesthesia for electroconvulsive therapy - new tricks for old drugs: a systematic review.

The objective of this review is to investigate existing literature in order to delineate whether the use of anaesthesia and timing of seizure induction in a new and optimised way may improve the efficacy of electroconvulsive therapy (ECT). PubMed/MEDLINE was searched for existing literature, last search on 24 June 2015. Relevant clinical studies on human subjects involving choice of anaesthetic, ventilation and bispectral index (BIS) monitoring in the ECT setting were considered. The references of relevant studies were likewise considered. Propofol yields the shortest seizures, etomidate and ketamine the longest. Etomidate and ketamine+propofol 1 : 1 seems to yield the seizures with best quality. Seizure quality is improved when induction of ECT is delayed until the effect of the anaesthetic has waned - possibly monitored with BIS values. Manual hyperventilation with 100% O2 may increase the pO2/pCO2-ratio, which may be correlated with better seizure quality. Etomidate or a 1 : 1 ketamine and propofol combination may be the best method to achieve general anaesthesia in the ECT setting. There is a need for large randomised prospective studies comparing the effect of methohexital, thiopental, propofol, ketamine, propofol+ketamine 1 : 1 and etomidate in the ECT treatment of major depressed patients. These studies should investigate safety and side effects, and most importantly have antidepressant efficacy and cognitive side effects as outcome measures instead of seizure quality.

Improving Wind Environment of Residential Neighborhoods by Understanding the Relationship between Building Layouts and Ventilation Efficiency

This research attempts to probe into the correlation between the residential building layout and ventilation performance of various spaces in an operative level. To quantify the influence of design change on outdoor ventilation, numerical modeling technology is adopted with ANSYS-Fluent as the simulation tool. As to evaluate the ventilation efficiency of exterior space, local mean age of air (L-MAA), which is common used in recent urban form studies, is further discussed for local region's ventilation efficiency in residential neighborhoods. Using this ventilation index, several cases are calculated and three types of building layout changes (lateral spacing, building lengths and stagger of location) are discussed. The simulation results show that L-MAA is a useful ventilation index to access the design changes on urban space ventilation and these design changes have great effects on exterior space ventilation. Building length has great influence on ventilation efficiency of different spaces, while the influence of lateral spacing and stagger of location changes varies greatly in different local regions.

Hemodynamic, Autonomic, Ventilatory, and Metabolic Alterations After Resistance Training in Patients With Coronary Artery Disease: A Randomized Controlled Trial.

The aim of this work was to evaluate the hemodynamic, autonomic, and metabolic responses during resistance and dynamic exercise before and after an 8-week resistance training program using a low-intensity (30% of 1 repetitium maximum), high-repetition (3 sets of 20 repetitions) model, added to an aerobic training program, in a coronary artery disease cohort. Twenty male subjects with coronary artery disease (61.1 ± 4.7 years) were randomly assigned to a combined training group (resistance + aerobic) or aerobic training group (AG). Heart rate, stroke volume, cardiac output, minute ventilation, blood lactate, and parasympathetic modulation indices of heart rate (square root of the mean squared differences of successive RR intervals [RMSSD] and dispersion of points perpendicular to the line of identity that provides information about the instantaneous beat-to-beat variability [SD1]) were obtained before and after an 8-week RT program while performing exercise on a cycle ergometer and a 45-degree leg press. Resistance training resulted in an increase in maximal and submaximal load tolerance (P < 0.01), a decreased hemodynamic response (P < 0.01), and a reduction in blood lactate in the combined training group compared to the aerobic training group during the 45-degree leg press. During exercise on a cycle ergometer, there was a decreased hemodynamic response and increased minute ventilation (P < 0.01). The 8-week RT program resulted in greater parasympathetic tone (RMSSD and SD1) and an increase in the SDNN index during exercise on a cycle ergometer and 45-degree leg press (P < 0.05). An 8-week resistance training program associated with aerobic training may attenuate hemodynamic stress, and modify metabolic and autonomic responses during resistance exercise. The training program also appeared to elicit beneficial cardiovascular and autonomic effects during exercise.

A four-dimensional computed tomography comparison of healthy and asthmatic human lungs

The purpose of this study was to explore new insights in non-linearity, hysteresis and ventilation heterogeneity of asthmatic human lungs using four-dimensional computed tomography (4D-CT) image data acquired during tidal breathing. Volumetric image data were acquired for 5 non-severe and one severe asthmatic volunteers. Besides 4D-CT image data, function residual capacity and total lung capacity image data during breath-hold were acquired for comparison with dynamic scans. Quantitative results were compared with the previously reported analysis of five healthy human lungs. Using an image registration technique, local variables such as regional ventilation and anisotropic deformation index (ADI) were estimated. Regional ventilation characteristics of non-severe asthmatic subjects were similar to those of healthy subjects, but different from the severe asthmatic subject. Lobar airflow fractions were also well correlated between static and dynamic scans (R2>0.84). However, local ventilation heterogeneity significantly increased during tidal breathing in both healthy and asthmatic subjects relative to that of breath-hold perhaps because of airway resistance present only in dynamic breathing. ADI was used to quantify non-linearity and hysteresis of lung motion during tidal breathing. Non-linearity was greater on inhalation than exhalation among all subjects. However, exhalation non-linearity among asthmatic subjects was greater than healthy subjects and the difference diminished during inhalation. An increase of non-linearity during exhalation in asthmatic subjects accounted for lower hysteresis relative to that of healthy ones. Thus, assessment of non-linearity differences between healthy and asthmatic lungs during exhalation may provide quantitative metrics for subject identification and outcome assessment of new interventions.

Tropical Cyclones Downscaled from Simulations with Very High Carbon Dioxide Levels

A method to simulate thousands of tropical cyclones using output from a global climate model is applied to simulations that span very high surface temperatures forced with high levels of carbon dioxide (CO2). The climatology of the storms downscaled from a simulation with modern-day conditions is compared to that of events downscaled from two other simulations featuring 8 and 32 times preindustrial-era levels of CO2. Storms shift poleward with warming: genesis locations and track densities increase in subtropical and higher latitudes, and power dissipation increases poleward of 20°S and 30°N. The average latitude at which storms reach their maximum intensity shifts poleward by more than 1.5° latitude in the 8 × CO2 experiment and by more than 7° latitude in the 32 × CO2 case. Storms live longer and are more numerous in both of the warmer climates. These increases come largely from an expansion of the area featuring favorable conditions into subtropics and midlatitudes, with some regions of the Arctic having the thermodynamic conditions necessary to sustain systems in the hottest case. Storms of category 5 intensity are 52% more frequent in the 8 × CO2 experiment but 40% less so in the 32 × CO2 case, largely owing to a substantial decline in low-latitude activity associated with increases in a normalized measure of wind shear called the ventilation index. Changes in genesis and track densities align well with differences in the ventilation index, and environmental conditions become substantially more favorable poleward of about 20° latitude in the warmer climates.

Evaluation value of oxygenation index of mechanical ventilation on the prognosis of patients with ARDS: a retrospective analysis with 228 patients

To investigate the evaluation value of oxygenation index at different times of mechanical ventilation (MV) on the prognosis of patients with acute respiratory distress syndrome (ARDS). A retrospectively analysis was conducted. A total of 228 patients with ARDS admitted to Department of Emergency of China Medical University Affiliated First Hospital from February 2014 to June 2016 were enrolled. All patients underwent MV treatment, and recruitment maneuver (RM) was performed by pressure-controlled ventilation (PCV) 30 minutes after the implementation of the protective ventilation strategy. Arterial blood gas analysis was performed at MV immediately, after RM and at 6, 12, 24 hours of MV, and oxygenation index was calculated. Vital signs, laboratory data, ultrasonic echocardiography, sequential organ failure assessment (SOFA) score, duration of MV, and ventilator related parameters of patients were collected. The patients were divided into survivors and non-survivors according to the prognosis of 28 days. The survivors were subdivided into high and low oxygenation group (oxygenation index was ≥ 150 mmHg and < 150 mmHg, respectively, 1 mmHg = 0.133 kPa). Differences in clinical indicators between survivors and non-survivors were compared. The correlation between the oxygenation index after RM and the oxygenation index at each time after MV was analyzed by bivariate correlation analysis. Receiver operating characteristic (ROC) curve was plotted to analyze predictive value of oxygenation index measured at different times for the 28-day outcome of patients with ARDS. Among 228 patients, 99 patients died within 28 days, and 129 survived, with mortality rate of 43.4%. (1) The oxygenation index after RM and at 6, 12, 24 hours after MV in survivors and non-survivors showed a continuously increased tendency, which was significantly lower in non-survivors than that in survivors (all P < 0.05). There was no significant difference in the duration of MV between high oxygenation group and low oxygenation group at MV immediately and after RM, but the duration of MV in high oxygenation group was significantly shorter than that of the low oxygenation group at 6, 12, 24 hour of MV (all P < 0.01). (2) After ventilation for 24 hours, serum creatinine (SCr), brain natriuretic peptide (BNP), lactate (Lac), right ventricular internal diameter, and SOFA score in non-survivors were significantly higher than those of survivors, and arterial partial pressure of oxygen (PaO2), platelet (PLT) and right ventricular ejection fraction (RVEF) were significantly lower than those of survivors (all P < 0.05). (3) After 24 hours ventilation, positive end-expiratory pressure (PEEP), tidal volume (VT), and minute ventilation (VE) in non-survivors were significantly higher than those of survivors, and static compliance of thorax (Cdyn) was significantly lower than that of survivors (all P < 0.01). (4) It was shown by correlation analysis that the oxygenation index after RM was positively correlated with those at 6, 12, 24 hours of MV (r values were 0.856, 0.765, and 0.758, respectively, all P < 0.001). (5) It was shown by ROC curve that the area under the ROC curve (AUC) of the oxygenation index after RM for predicting 28-day prognosis was 0.688. When the cut-off value was 80.75 mmHg, the sensitivity was 97.7%, and the specificity was 42.4%, which could only be used for preliminary judgment of prognosis. The AUC of oxygenation index at 6, 12, 24 hours of MV for 28-day survival of ARDS patients were 0.719, 0.727, 0.754, respectively. When the cut-off values were 171.50, 192.14, and 161.75 mmHg, the sensitivity was 69.8%, 67.4%, 86.0%, and the specificity was 78.8%, 78.8%, and 63.6%, respectively. It indicated that the predictive value was higher, and no significant difference was found among the oxygenation index at different time points. The oxygenation index after the early stage of RM can preliminarily determine the prognosis of patients. The predictive value of oxygenation index after MV for 28-day survival of ARDS patients was higher, so the oxygenation index measured at 6 hours of MV may be considered to evaluate the prognosis of patients with ARDS.

Is there a determining factor that predicts mortality in patients with congenital diaphragmatic hernia?

AimThis study was designed to investigate the factors affecting the prognosis in neonates with congenital diaphragmatic hernia (CDH) who were treated in our clinic. These factors included prenatal lung-head ratio (LHR), prenatal stomach and liver presence in the thorax, blood gases in the first 24 h and the modified ventilation index (MVI).Material and methodsThe study was carried out retrospectively in 30 neonates with prenatally diagnosed left CDH who were treated in our clinic between January 2007 and 2013. Data were collected, evaluated, and statistically analyzed for gender, birth weight, gestational age, prenatal LHR, prenatal presence of stomach and liver in the thorax, postnatal initial blood gases in the first 24 h and MVI.ResultsThe median LHR for non-survivors was 1.49 and for survivors 1.51. No statistically significant difference in LHR was detected between survivors and non-survivors. In 19 neonates, prenatal ultrasonography (USG) revealed intrathoracic stomach, and 9 of these infants died. Intrathoracic liver was seen in 15 neonates, and 9 of these died. A statistically significant difference was not found between survivors and non-survivors in the intrathoracic liver or intrathoracic stomach neonates. A comparison between the non-survivors and survivors showed a median pH value of 7.10 in non-survivors and 7.24 in survivors (p = 0.002). The median PaCO2 value was 69.4 mm Hg in non-survivors and 51.9 mm Hg in survivors (p = 0.01). There were statistically significant differences in pH and PaCO2 values. The median value of MVI was 33 in survivors and 100 in non-survivors. There was a statistically significant difference between overall non-survivors and survivors in the MVI value (p < 0.05).ConclusionsBased on the findings, postnatal pH, and PaCO2 and MVI values are favorable prognostic factors in CDH in our selected group of patients.

Climatology of wintertime long-distance transport of surface-layer air masses arriving urban Beijing in 2001–2012

In this study, the FLEXPART-WRF coupled modeling system is used to conduct 12-year Lagrangian modeling over Beijing, China, for the winters of 2001–2012. Based on large trajectory tracking ensembles, the long-range air transport properties, in terms of geographic source regions within the atmospheric planetary boundary layer (PBL) and large-scale ventilation, and its association with air quality levels were quantified from a climatological perspective. The results show the following: (1) The air masses residing in the near-surface layer over Beijing potentially originate from broader atmospheric boundary-layer regions, which cover vast areas with the backward tracking time elapsed. However, atmospheric transport from northeastern China and, to a lesser extent, from the surrounding regions of Beijing is important. (2) The evolution of air quality over Beijing is negatively correlated with large-scale ventilation conditions, particularly at a synoptic timescale. Thus, the simple but robust backward-trajectory ventilation (BV) index defined in this study could facilitate operational forecasting of severe air pollution events. (3) By comparison, the relatively short-range transport occurring over transport timescales of less than 3 days from southern and southeastern Beijing and its surrounding areas plays a vital role in the formation of severe air pollution events during the wintertime. (4) Additionally, an interannual trend analysis suggests that the geographic sources and ventilation conditions also changed, at least over the last decade, corresponding to the strength variability of the winter East Asian monsoon.

Indoor pollution in high-altitude dwellings: An assessment of affecting factors across four Sherpa villages in the Khumbu region, Nepal

Household air pollution (HAP) from biomass fuel smoke is a major health risk, especially in developing countries. The ventilation of buildings and the type of fume discharge could also affect HAP. The present study aims to investigate the impact of stove type and kitchen characteristics on levels of pollutants. In particular, we investigated the potential geometric ventilation of buildings using geometric ventilation index (GVI), the presence of chimneys, the type of fuel and the environmental carbon monoxide level (a marker of indoor pollution) in the households of four Sherpa villages located in a mountain region of Nepal at altitudes between 2500 and 3900 m. We analysed 114 buildings (76 private residences and 38 lodges that accommodate tourists). Lodges had a more effective discharge system and a higher GVI, which had an inverse, significant correlation with indoor CO levels (r = 0.52). The level of indoor CO was more than 50% higher in private residences than in lodges. In the univariate analysis, only the absence of a chimney was associated with higher indoor CO (OR 3.4 (CL95%, 1.2–10.0), p = 0.02). We conclude that the adoption of chimneys and sealed stoves with exhaust pipes should be the first measure taken to reduce pollutants inside the households of high mountain regions until a switch to clean fuels can be achieved.

Modelling responses of the inert-gas washout and MRI to bronchoconstriction

Many lung diseases lead to an increase in ventilation heterogeneity (VH). Two clinical practices for the measurement of patient VH are in vivo imaging, and the inert gas multiple breath washout (MBW). In this study computational modelling was used to compare the responses of MBW indices LCI and scond and MRI measured global and local ventilation indices, σr and σlocal, to constriction of airways in the conducting zone of the lungs. The simulations show that scond, LCI and σr behave quite similarly to each other, all being sensitive to increases in the severity of constriction, while exhibiting little sensitivity to the depth at which constriction occurs. In contrast, the local MRI index σlocal shows strong sensitivity to depth of constriction, but lowered sensitivity to constriction severity. We finish with an analysis of the sensitivity of MRI indices to grid sizes, showing that results should be interpreted with reference to the image resolution. Overall we conclude that the application of both local and global VH measures may help to classify different types of bronchoconstriction.

Comparing High-Frequency Ventilation and Conventional Ventilation on Morphology of Brain, Kidney and Liver in Preterm Babies with Respiratory Distress

Background: The increase in the ventilator rates by conventional mechanical ventilation (CMV) is limited by a minimum amount of time needed for a complete inspiration and expiration. In preterm babies with respiratory distress syndrome, it may not be sufficient to manage the hypercapnia and hypoxia associated. High-frequency ventilation (HFV) can be considered as a substitute for CMV in premature infants by increasing the ventilator rate further and reducing the tidal volume. The current study evaluates the efficacy and effects on brain, liver and kidney morphology of HFV in preterm babies with respiratory distress. Methods: This prospective and analytical study was conducted from December 2011 to January 2013 on 83 preterm babies’ with an initial provisional diagnosis of respiratory distress that needed respiratory support at birth or soon after admission. Initial and follow up blood gas (BG) and cranial U/S, and renal and hepatic function tests were done. Results: The study was conducted on 83 preterm babies, aged less than 37 weeks of gestation, who were divided into control (40) and study (43) groups. The study group showed significantly higher PEEP and PIP values than control in CMV and were shifted to HFV thereafter. The control group needed only CMV. After the intervention, statistically significant improvement in arterial blood gas parameters with respect to blood pH, pCO2 and pO2. The mean blood pH was found to be 7.386 ±0.039, with increase in mean pO2 (before shift =45.44±4.36 vs. after shift=40.56 ±2.597 mm Hg respectively, p= 0.01) and decrease in mean pCO2 (before shift= 38.23±0.03 vs. after shift=42.87 ± 6.915 mm Hg respectively, p=0.01). We can say that HFV helped to reduce acidosis, hypoxia, and hypercapnia in the neonates in the study group. In terms of renal functions, the serum sodium content marginally increased with HFV (After shift= 136.00±3.910 vs. before shift=135.00±5.686 mol/l, p=0.000), Significant increase in mean 24-hour urinary creatinine from their initial CMV values after subjecting them to HFV (before shift 14.509± 4.874 mg/dl vs after shift 15.340±7.054 mg/dl, p=0.002). In terms of hepatic functions, significant difference was observed after intervention was detected with higher PT in HFV group (0.01); on the other hand, no significant difference regarding ALT, PTT and fibrinogen between study and control groups was detected after HFV intervention. Brain ultra-sound scan (BUSS) results showed that the intraventricular haemorrhage (IVH) was reduced in the HFV group as compared to the CMV group. BUSS outcome also showed that there is a significant correlation between IVH and surfactant medication. Conclusion: Rescue HFV improved oxygenation, ventilation, lung recruitment and better oxygenation indices and there was no increased incidence of IVH. In addition, HFV had no deleterious effect on other organs such as the brain, kidney and liver.

Vasoactive-ventilation-renal score reliably predicts hospital length of stay after surgery for congenital heart disease

ObjectivesWe aimed to further validate the vasoactive-ventilation-renal score as a predictor of outcome in patients recovering from surgery for congenital heart disease. We also sought to determine the optimal time point within the early recovery period at which the vasoactive-ventilation-renal score should be measured. MethodsWe prospectively reviewed consecutive patients recovering from cardiac surgery within our intensive care unit between January 2015 and June 2015. The vasoactive-ventilation-renal score was calculated at 6, 12, 24, and 48 hours postoperatively as follows: vasoactive-ventilation-renal score = ventilation index + vasoactive-inotrope score + Δ creatinine [change in serum creatinine from baseline*10]. Primary outcome of interest was prolonged hospital length of stay, defined as length of stay in the upper 25%. Receiver operating characteristic curves were generated, and areas under the curve with 95% confidence intervals were calculated for all time points. Multivariable logistic regression modeling also was performed. ResultsWe reviewed 164 patients with a median age of 9.25 months (interquartile range, 2.6-58 months). Median length of stay was 8 days (interquartile range, 5-17.5 days). The area under the curve value for the vasoactive-ventilation-renal score as a predictor of prolonged length of stay (>17.5 days) was greatest at 12 hours postoperatively (area under the curve = 0.93; 95% confidence interval, 0.89-0.97). On multivariable regression analysis, after adjustment for potential confounders, the 12-hour vasoactive-ventilation-renal score remained a strong predictor of prolonged hospital length of stay (odds ratio, 1.15; 95% confidence interval, 1.10-1.20). ConclusionsIn a heterogeneous population of patients undergoing surgery for congenital heart disease, the novel vasoactive-ventilation-renal score calculated in the early postoperative recovery period can be a strong predictor of prolonged hospital length of stay.

Dynamical downscaling of tropical cyclones from CCSM4 simulations of the Last Glacial Maximum

AbstractDynamical downscaling of simulations of the Last Glacial Maximum (LGM) and late twentieth century (20C) were conducted using the Weather Research and Forecasting (WRF) model with the aim of (1) understanding how the downscaled kinematic and thermodynamic variables influence simulated tropical cyclone (TC) activity over the western North Pacific during the LGM and the 20C periods and (2) to test the relevance of TC genesis factors for the colder LGM climate. The results show that, despite the lower temperatures during the LGM, the downscaled TC climatology over the western North Pacific in the LGM simulation does not differ significantly from that in the 20C simulation. Among the TC environmental factors, the TC potential intensity, mid‐tropospheric entropy deficit, and vertical wind shear during the LGM were consistent with previous analyses of TC genesis factors in LGM global climate model simulations. Changes in TC genesis density between the LGM and the 20C simulations seem to be well represented by the ventilation index, a nondimensional measure of the combined effects of vertical wind shear, and thermodynamic properties, suggesting the potential applicability of those factors for TC activity evaluation during the LGM and possibly other climates.

Respiratory weakness after mechanical ventilation is associated with one-year mortality - a prospective study.

BackgroundDiaphragm dysfunction in mechanically ventilated patients is associated with poor outcome. Maximal inspiratory pressure (MIP) can be used to evaluate inspiratory muscle function. However, it is unclear whether respiratory weakness is independently associated with long-term mortality. The aim of this study was to determine if low MIP is independently associated with one-year mortality.MethodsWe conducted a prospective observational cohort study in an 18-bed ICU. Adults requiring at least 24 hours of mechanical ventilation with scheduled extubation and no evidence of pre-existing muscle weakness underwent MIP evaluation just before extubation. Patients were divided into two groups: low MIP (MIP ≤30 cmH2O) and high MIP (MIP >30 cmH2O). Mortality was recorded for one year after extubation. For the survival analysis, the effect of low MIP was assessed using the log-rank test. The independent effect of low MIP on post mechanical ventilation mortality was analyzed using a multivariable Cox regression model.ResultsOne hundred and twenty-four patients underwent MIP evaluation (median age 66 years (25th–75th percentile 56–74), Simplified Acute Physiology Score (SAPS) 2 = 45 (33–57), duration of mechanical ventilation 7 days (4–10)). Fifty-four percent of patients had low MIP. One-year mortality was 31 % (95 % CI 0.21, 0.43) in the low MIP group and 7 % (95 % CI 0.02, 0.16) in the high MIP group. After adjustment for SAPS 2 score, body mass index and duration of mechanical ventilation, low MIP was independently associated with one-year mortality (hazard ratio 4.41, 95 % CI 1.5, 12.9, p = 0.007). Extubation failure was also associated with low MIP (relative risk 3.0, 95 % CI 1, -9.6; p = 0.03) but tracheostomy and ICU length of stay were not.ConclusionLow MIP is frequent in patients on mechanical ventilation and is an independent risk factor for long-term mortality in ICU patients requiring mechanical ventilation. MIP is easily evaluated at the patient’s bedside.Trial RegistrationThis study was retrospectively registered in www.clinicaltrials.gov (NCT02363231) in February 2015.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-016-1418-y) contains supplementary material, which is available to authorized users.

Numerical investigation of wind-driven natural ventilation performance in a multi-storey hospital by coupling indoor and outdoor airflow

This study employed two ventilation indexes: local mean age of air and air change rate per hour, to investigate wind-induced natural ventilation of 260 wards of a multi-storey hospital building in suburb of Guangzhou using computational fluid dynamics simulations. Using the surface-grid extrusion technique, high-quality hexahedral grid cells were generated for the coupled outdoor and indoor airflow field. Turbulence was solved by the renormalisation group k-ɛ model validated against experimental data with grid independence studies. Homogeneous tracer gas emission was adopted to predict room age of air. The air change rate of cross ventilation and single-sided ventilation can reach 30–160 h−1 and 0.5–7 h−1, respectively. Due to different locations of room openings on the balconies, natural ventilation of a room can be greatly better than its neighbouring room. The wind-induced cross ventilation highly depends on the distance from the room opening to the stagnation point and on the resulting pressure distribution on the target building surface. Furthermore, it is significantly influenced by the upstream buildings, the bent shape of the target building, and the prevailing wind directions. The coupled computational fluid dynamics methodologies with integrated ventilation indexes are useful for assessing the natural ventilation performance in other complex built environments.