Lower Inflection Point Research Articles

Sex-specific prognosis of right ventricular size measured by 3D echocardiography following isolated tricuspid valve surgery

Abstract Backgrounds Isolated tricuspid valve surgery (ITVS) is considered a high-risk procedure. Right ventricular (RV) size plays a critical role in the prognosis of ITVS patients. The effect of sex differences in the degree of right ventricular（RV）dilatation in ITVS patients has not been established. Purpose The primary objective of this study was to assess in-hospital major adverse events (AEs) following ITVS in women compared with men on the basis of preoperative RV size measured by 3D echocardiography. Methods Consecutive patients undergoing ITVS were identified from a prospectively maintained database.Transthoracic echocardiography was performed the day before ITVS. In-hospital AEs were defined as one of the following occurring before discharge: death, shock, acute renal failure requiring dialysis, or prolonged (>72h) mechanical ventilation. 3D RV parameters including end-diastolic volume (EDV), end-systolic volume (ESV), EDVi (indexed by body surface area), ESVi (indexed by body surface area) and ejection fraction (EF) were calculated using commercially available software. Comparison of the adjusted odds ratios (ORs) generated by multivariate logistic regression of in-hospital AEs between women and men on the basis of baseline RV parameters. Results 59 patients (median age 62 years, 42.37% male, functional tricuspid regurgitation in 62.71%) were finally enrolled. In-hospital AEs were identified in 23 patients (3 death, 5 shock, 5 renal failure, 10 prolonged mechanical ventilation). The risk of AEs was increased from baseline, when the ESV was 69.73 mL for women and 90.66 mL for men. Regarding EDV, the risk for women increased at 130.49 mL compared with 170.36 mL in men. Accordingly, when indexed by body surface area, women had a lower inflection point for both EDVi and ESVi (76.71 mL/m2 vs 91.35 mL/m2, 34.04 mL/m2 vs 52.49 mL/m2). However, there was no inflection point for increased risk with RVEF in either men or women. Conclusion Women undergoing ITVS have a higher risk of in-hospital AEs with smaller RV size. These results support the use of sex-specific thresholds for RV size when making surgical decisions in patients with severe tricuspid regurgitation.Figure 1.Adjusted ORs for RV size.

Detecting Intrathoracic Airway Closure during Prehospital Cardiopulmonary Resuscitation Using Quasi-Static Pressure-Volume Curves: A Pilot Study.

Background: Intrathoracic airway closure frequently occurs during cardiac arrest, possibly impairing ventilation. Previously, capnogram analysis was used to detect this pathophysiological process. In other populations, quasi-static pressure-volume curves obtained during constant low-flow inflations are routinely used to detect intrathoracic airway closure. This study reports the first use of quasi-static pressure-volume curves to detect intrathoracic airway closure during prehospital cardiopulmonary resuscitation. Methods: Connecting a pressure and flow sensor to the endotracheal tube enabled the performance of low-flow inflations during cardiopulmonary resuscitation using a manual resuscitator. Users connected the device following intubation and performed a low-flow inflation during the next rhythm analysis when chest compressions were interrupted. Determining the lower inflection point on the resulting pressure-volume curves allowed for the detection and quantification of intrathoracic airway closure. Results: The research device was used during the prehospital treatment of ten cardiac arrest patients. A lower inflection point indicating intrathoracic airway closure was detected in all patients. During cardiac arrest, the median pressure at which the lower inflection point occurred was 5.56 cmH20 (IQR 4.80, 8.23 cmH20). This value varied considerably between cases and was lower in patients who achieved return of spontaneous circulation. Conclusions: In this pilot study, quasi-static pressure-volume curves were obtained during prehospital cardiopulmonary resuscitation. Intrathoracic airway closure was detected in all patients. Further research is needed to determine whether the use of ventilation strategies to counter intrathoracic airway closure could lead to improved outcomes and if the degree of airway closure could serve as a prognostic factor.

Explorative study on lower inflection point dynamics during cardiopulmonary resuscitation: Potential implications for airway management

IntroductionIn patients undergoing cardiopulmonary resuscitation (CPR) after an Out-of-Hospital Cardiac Arrest (OHCA), intrathoracic airway closure can impede ventilation, adversely affecting patient outcomes. This explorative study investigates the evolution of intrathoracic airway closure by analyzing the lower inflection point (LIP) during the inspiration phase of CPR, aiming to identify the potential thresholds for alveolar recruitment. Methods and materialsEleven OHCA patients undergoing CPR with endotracheal intubation and manual bag ventilation were included. Flow and pressure measurements were obtained using Sensirion SFM3200AW and Wika CPT2500 sensors attached to the endotracheal tube, connected to a Surface Go Tablet for data collection. Flow data was analyzed in Microsoft Excel, while pressure data was processed using the Wika USBsoft2500 application. Analysis focused on the inspiration phase of the first 6–8 breaths, with an additional 2 breaths recorded and analyzed at the end of CPR. ResultsAcross the cohort, the median tidal volume was 870.00 milliliter (mL), average flow was 31.90 standard liters per minute (slm), and average pressure was 17.21 cmH2O. The calculated average LIP was 31.47 cmH2O. Most cases (72.7%) exhibited a negative trajectory in LIP evolution during CPR, with 2 cases (18.2%) showing a positive trajectory and 1 case remaining inconclusive. The average LIP in the first 8 breaths was significantly higher than in the last 2 breaths (p = 0.018). No significant correlation was found between average LIP and return of spontaneous circulation (ROSC), compression depth, frequency, or end-tidal CO2 (EtCO2). However, a significant negative correlation was observed between the average LIP of the last 2 breaths and CPR duration (p = 0.023). Validation: LIP calculation in low-flow ventilations using the novel mathematical method yielded values consistent with those reported in the literature. Discussion/conclusionThese explorative data demonstrate a predominantly negative trajectory in LIP evolution during CPR, suggesting potential challenges in maintaining airway patency. Limitations include a small sample size and sensor recording issues. Further research is warranted to explore the evolution of LIP and its implications for personalized ventilation strategies in CPR.

Cumulative trophic curves elucidate tropical coral reef ecosystems

There are few generalizable patterns in ecology, with widespread observations and predictability. One possible generalizable pattern is the cumulative trophic theory, which consistently exhibits S-curves of cumulative biomass over trophic level (TL) for over 200 different marine ecosystems. But whether those cumulative biomass patterns persist in some of the more distinct marine ecosystems, coral reefs, is unclear. Coral reefs are unique among marine ecosystems, representing global biodiversity hotspots and providing crucial ecosystem services. They are subject to many pressures, including both global (e.g., climate and ocean changes, warming, acidification) and local (e.g., overexploitation/overfishing, increase in turbidity, bleaching, habitat destruction, invasive species) stressors. The analysis of emergent ecosystem features, such as cumulative biomass S-curves, could represent a useful and new analytical option that can also be implemented for coral reefs. The cumulative biomass approach was applied to 42 U.S. Pacific islands (Guam and the Commonwealth of Northern Mariana Islands, American Samoa, the Pacific Remote Islands Areas, and the Northwestern and Main Hawaiian Islands), using data collected from fish surveys. Results show that coral reef ecosystems do indeed follow the S-curve patterns expected from cumulative trophic theory, which is not trivial for tropical reef systems that tend to be less widely examined and strongly dominated by structuring organisms like corals. The curve parameters results are also consistent with both fish assemblage diversity indexes and the benthic substrate ratio, which suggests this measure could serve as a useful ecosystem indicator to measure the ecological status of reefs. Moreover, the curve shape was consistent with what one would expect for different levels of perturbation, with the areas more densely inhabited showing less pronounced S-curves, in contrast to those observed in low human population density islands. All this is reflected in the curve parameters, particularly inflection point of the TL and steepness, generally showing a negative response to both natural and anthropogenic disturbances. Cross-archipelago differences have also been detected with the Hawaiian Island chain tending to have lower inflection points for biomass and TL than other regions. Collectively our findings demonstrate the potential application of the cumulative biomass approach to evaluate coral reef ecosystems.

Association between nickel exposure and body compositions in the United States: a population-based cross-sectional study

BackgroundIncreasing body fat or decreasing muscle and bone mass were associated with worse health outcomes in the adult population. The effects of nickel exposure on body composition are not known. The aim of the current study was to investigate the relationship between urinary nickel levels and body compositions.Materials and methodsTwo thousand seven hundred sixty-two participants were included in the analysis from the National Health and Nutrition Examination Surveys of 2017–2018 after excluding participants who have missing data on urinary nickel and those with missing all body mass component data. We used weighted generalized linear models to explore the relationship between urinary nickel and body mass components under interpolating missing covariable values. Simultaneously, sensitivity analyses and subgroup analysis were conducted to verify stability of analysis result. Curve fitting and saturation effect analysis were used to explore the possible nonlinear relationship between urine nickel and body compositions.ResultsAmong the 2,762 participants, the average urinary nickel level was 1.58 ug/L. The weighted generalized linear models, the sensitivity analyses and subgroup analyses found no significant linear relationship between urinary nickel and body compositions. For body weight, BMI, TLM, ALM, TRF, TOF and BMC, the urine nickel saturation effect values were 0.76, 0.74, 0.5, 0.67, 0.64, 0.48, and 0.45 ug/L, respectively. For each 1 ug/L rise in urinary nickel levels at levels below the turning point, body weight increases (β = 9.06, 95% CI = 2.75, 15.36, p = 0.01), BMI increases (β = 3.20, 95% CI = 1.36, 5.05, p = < 0.001), TLM decreases (β = -47.39, 95% CI = -97.38, 2.59, p = 0.06), ALM decreases (β = -37.25, 95% CI = -63.25, -11.24, p = 0.01), TRF increases (β = 20.68, 95% CI = 1.50, 39.86, p = 0.03), TOF increases (β = 57.92, 95% CI = -0.12, 115.95, p = 0.05), and BMC decreases (β = -6.84, 95% CI = -12.64, -1.04, p = 0.02).ConclusionsIn summary, our study demonstrated that a dose–response relationship exists between urinary nickel and body compositions, with a low inflection point level of urinary nickel for the saturation effect.

Does Adult Spinal Deformity Affect Cardiac Function? A Prospective Perioperative Study.

Prospective comparative study. The objective of this study was to investigate perioperative cardiac function using echocardiography in patients undergoing surgery for the adult spinal deformity (ASD). Corrective surgery for ASD has increased, especially in older persons. However, perioperative complication rates remain high in ASD surgery, including cardiopulmonary complications. This study included patients with ASD who underwent surgery between May 2016 and April 2018. A cardiologist performed all echocardiography imaging preoperatively and 2 weeks postoperatively. Left ventricular contractility was measured using left ventricular ejection fraction (LVEF), and right ventricular contractility was measured using tricuspid annular plane systolic excursion (TAPSE) and tricuspid annular peak systolic velocity (S'). Spinopelvic radiographic parameters, the apices of thoracic kyphosis and lumbar lordosis, and the inflection point where the vertebral curvature changes from kyphosis to lordosis were also measured. Differences between preoperative and postoperative measurements for continuous variables were analyzed using a paired Student t test. Differences in continuous and categorical variables between two independent groups were analyzed using an unpaired Student t test and Fisher exact test, respectively. Multivariate logistic regression analyses were performed to detect influential factors. Sixty-one patients were included [12 males and 49 females; average age, 64.0 (22-84)yr]. LVEF, TAPSE, and S', respectively changed from 64.4%, 24.9mm, and 14.3cm/s to 65.4%, 25mm, and 15cm/s postoperatively with no significance. However, in LVEF<59.3% (average-1SD), TAPSE<17mm, and S'<11.8cm/s cases, respectively, these increased significantly from 55.7%, 17.9mm, and 10.5cm/s to 60.9%, 21.4mm, and 14.2cm/s postoperatively ( P =0.036, 0.029, and 0.022, respectively). The LVEF<59.3% group showed a significantly lower inflection point level (1.5 vs. 2.9) preoperatively ( P =0.007). The S'<11.8cm/s group showed significantly larger thoracic kyphosis (28.3° vs. 19.4°) preoperatively ( P =0.013). Perioperative cardiac function did not deteriorate after surgery in patients with ASD. In those with lower cardiac function preoperatively, there were significant improvements noted postoperatively. The preoperative inflection point level was significantly lower in the lower LVEF group. Preoperative thoracic kyphosis was significantly larger in the lower tricuspid annular peak systolic velocity group.

Exploring the role of co-agglomeration of manufacturing and producer services on carbon productivity: An empirical study of 282 cities in China

Carbon productivity is a better measure of a region's sustainable economic growth since it considers economic development and carbon emissions at the same time. It is crucial to improve carbon productivity through the co-agglomeration of manufacturing and producer services for China. To better understand the effect and mechanism of co-agglomeration, this study uses panel data of 282 Chinese cities from 2003 to 2017 to examine the effect of manufacturing and producer services co-agglomeration on carbon productivity. Further, moderating effects models and panel threshold models are used to investigate the mechanisms of co-agglomeration effect on carbon productivity. The results suggest that the influence of co-agglomeration on carbon productivity is U-shaped with an inflection point of 3.63, indicating that a high level of co-agglomeration is required for carbon productivity to increase. Compared with other cities, cities in the eastern region or with a large scale have lower inflection points. The upgrading of industrial structure, production efficiency, and the production chain has a positive moderating effect on the influence of co-agglomeration on carbon productivity, while upgrading of non-production chains does not. When the levels of capital misallocation and labor misallocation reach the threshold of 1.115 and 1.557 respectively, industrial co-agglomeration has a promoting effect on carbon productivity. This research offers valuable insights for optimizing the urban industrial layout to improve carbon productivity.

Effects of Cadmium on Superoxide Dismutase Activity in Reed Leaves

Industrial polluted water has become an important water source for irrigation in the majority of constructed wetlands or even natural wetlands in China. The shortage of clean water resources has raised concerns about the potential accumulation of heavy metals, such as cadmium. Plants stressed by high levels of cadmium can increase the activity of superoxide dismutase. We have identified a positive correlation between the superoxide dismutase activity and the cadmium content of reed leaves in the wetland. Regression analysis confirmed that the superoxide dismutase activities fit a logistic curve. The logistic model was then applied to describe the superoxide dismutase activity, estimating parameters under different levels of cadmium stress. According to the findings, higher cadmium concentrations would cause the superoxide dismutase activity to increase at a higher intrinsic rate, have a lower environmental capacity k, and have lower inflection points. The dynamic model predicted an acceptable cadmium concentration of less than 3mg.kg-1. At this concentration, reeds could develop and grow satisfactorily in the presence of cadmium. Therefore, the concentration of cadmium in the irrigated water of polluted water in mine sites, papermaking wastewater, or other industrial wastewater should be less than or equal to 3mg.kg-1 to ensure the normal growth of reeds in related wetlands.

Does a stick work? A meta‐analytic examination of curvilinear relationships between job insecurity and employee workplace behaviors

SummaryThe job insecurity literature has been limited by the dominant linear view on the effects of job insecurity and the misconception that the conceptualizations and operationalizations of job insecurity across studies are homogenous. To challenge these two assumptions, we contrast the integrated perspective based on social exchange theory and job preservation motivation with activation theory and propose competing hypotheses for the curvilinear relationships between job insecurity and employee behavioral outcomes, including task performance, organizational citizenship behavior (OCB), creative performance, safety behavior, and counterproductive work behavior (CWB). We also examine the moderating roles of different conceptualizations of job insecurity (i.e., cognitive vs. affective job insecurity; quantitative vs. qualitative job insecurity) in the proposed curvilinear relationships. Our meta‐analysis demonstrates that the negative relationships of job insecurity with task performance and OCB‐organization turn positive after inflection points, supporting the integrated perspective of social exchange theory and job preservation motivation but not activation theory. Moreover, the negative relationships of job insecurity with OCB‐individual and creative performance turn nonsignificant as job insecurity further increases. Finally, job insecurity has a linear, negative relationship with safety behavior, but a linear, positive relationship with CWB‐organization. Interestingly, affective job insecurity has lower inflection points than cognitive job insecurity, and qualitative job insecurity has lower inflection points than quantitative job insecurity. This study provides a deep and fine‐grained understanding of the curvilinear relationships between job insecurity and workplace behaviors and pushes the literature forward by focusing on the nuanced differences among various types of job insecurity.

Prediction of soil water characteristic curves based on low suction section and inflection point

Abstract Given the cumbersome determination method of the Soil Water Characteristic Curve (SWCC), the collapsible loess (silty clay loam) in Lanzhou was taken as the research object to explore a symmetrical prediction method for SWCC in a low suction section on the inflection point, and to determine the optimal suction section and the inflection point. The results showed that in the range of 0–7,000 cm suction, the spatial variation coefficient (CV) of soil saturation of each bulk density increased with the increase of suction. Soil saturation showed weak spatial variability when suction &amp;lt;800 cm, and moderate spatial variability when suction ≥800 cm. Using a bulk density of 1.58 g/cm3 as an example, the SWCC determined by the symmetry of the bending point was compared with the measured data of 0–300, 0–500, 0–800 and 0–1,000 cm suction sections. It was found that the measured soil saturation of SWCC determined by the data for the 0–800 cm suction section was the most consistent with the predicted value. The measured and predicted saturation points of the SWCC were most consistent with suction segments of 0–800 cm. SWCC data of different textures and bulk density were used to verify the prediction method at low suction section and an inflection point of 0–800 cm. It was found that the average absolute error and root mean square error of statistical indicators were close to 0, and the correlation coefficient was greater than 0.9915. The actual and predicted values of each soil parameter were linearly correlated. This method of predicting SWCCs with low suction and inflection points ensures both a high degree of curve fitting and the accuracy of characteristic soil parameters, providing a simple method for the prediction of SWCCs and guidance for managing soil water in loessial areas.

Computed tomographic assessment of lung aeration at different positive end-expiratory pressures in a porcine model of intra-abdominal hypertension and lung injury

BackgroundIntra-abdominal hypertension (IAH) is common in critically ill patients and is associated with increased morbidity and mortality. High positive end-expiratory pressures (PEEP) can reverse lung volume and oxygenation decline caused by IAH, but its impact on alveolar overdistension is less clear. We aimed to find a PEEP range that would be high enough to reduce atelectasis, while low enough to minimize alveolar overdistention in the presence of IAH and lung injury.MethodsFive anesthetized pigs received standardized anesthesia and mechanical ventilation. Peritoneal insufflation of air was used to generate intra-abdominal pressure of 27 cmH2O. Lung injury was created by intravenous oleic acid. PEEP levels of 5, 12, 17, 22, and 27 cmH2O were applied. We performed computed tomography and measured arterial oxygen levels, respiratory mechanics, and cardiac output 5 min after each new PEEP level. The proportion of overdistended, normally aerated, poorly aerated, and non-aerated atelectatic lung tissue was calculated based on Hounsfield units.ResultsPEEP decreased the proportion of poorly aerated and atelectatic lung, while increasing normally aerated lung. Overdistension increased with each incremental increase in applied PEEP. “Best PEEP” (respiratory mechanics or oxygenation) was higher than the “optimal CT inflation PEEP range” (difference between lower inflection points of atelectatic and overdistended lung) in healthy and injured lungs.ConclusionsOur findings in a large animal model suggest that titrating a PEEP to respiratory mechanics or oxygenation in the presence of IAH is associated with increased alveolar overdistension.

Spatio-temporal changes of AOD in Xinjiang of China from 2000 to 2019: Which factor is more influential, natural factor or human factor?

Aerosol optical depth (AOD), which represents the optical attenuation, poses a major threat to the production activity, air quality, human health and regional sustainable development of arid and semi-arid areas. To some degree, AOD shows areal air pollution level and possesses obvious spatio-temporal characteristics. However, long-time sequences and detailed AOD information can not be provided due to currently limited monitoring technology. In this paper, a daily AOD product, MODIS-based Multi-angle Implementation of Atmospheric Correction (MAIAC), is deployed to analyze the spatio-temporal characteristics in Xinjiang Uygur Autonomous Region from 2000 to 2019. In addition, the importance of influencing factors for AOD is calculated through Random Forest (RF) Model and the propagation trajectories of pollutants are simulated through Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) Model. Spatio distribution of AOD presents a tendency that AOD value in northern Xinjiang is low while the value in southern Xinjiang is high. Regions with high AOD values are mainly concentrated in Tarim Basin. AOD in southern Xinjiang is the highest, followed by that in eastern Xinjiang and AOD value in northern Xinjiang is the lowest. Seasonal variation of AOD is significant: Spring (0.309) > summer (0.200) > autumn (0.161) > winter (0.158). Average AOD value in Xinjiang is 0.196. AOD appears wavy from 2000 to 2014 with its low inflection point (0.157) appearing in 2005, and then increases, reaching its peak in 2014 (0.223). The obvious downward tendency after 2014 shows that the use of coal to natural gas (NG) conversion project improves the conditions of local environment. According to RF Model, NG contributes most to AOD. HYSPLIT Model reveals that aerosol in southern Xinjiang is related to the short-distant carriage of dust aerosol from the Taklimakan Desert. Aerosol there can affect Inner Mongolia through long-distant transport. Blocked by the Tianshan Mountains, fine dust particles can not cross the Tianshan Mountains to become a factor contributing to AOD in northern Xinjiang.

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Figure 1: Pressure-Volume curve. Horizontal axis is airway pressure in cmH2O, vertical axis is resultant tidal volume in ml. LIP: Lower inflection point, HIP: high or upper inflection point, PMC: point of maximum curvature or expiratory inflection point.

Effects of different positive end-expiratory pressure titrating strategies on oxygenation and respiratory mechanics during one- lung ventilation: a randomized controlled trial.

Positive end-expiratory pressure (PEEP) is widely used to reduce the risk of hypoxemia and atelectasis during one-lung ventilation (OLV); however, the optimal strategy for PEEP titrating remains unclear.The purpose of the study was to investigate the effects of different PEEP titrating strategies on oxygenation and respiratory mechanics during OLV. Patients undergoing thoracic surgery with general anesthesia were randomly allocated into five groups. In P0 group, PEEP was set to zero; in PLIP2 group, PEEP was set to 2 cmH2O plus the pressure of lower inflection point (LIP) of pressure-volume (P-V) curve; in PLIPS group, PEEP was titrated to achieve maximum static compliance from the averaged LIP pressure value; in groups PSTAT and PDYN, the incremental PEEP values were titrated to achieve maximum static compliance or maximum dynamic compliance from 4 cmH2O. Hemodynamic measurements, respiratory mechanics, and blood gas analyses were recorded at the beginning of OLV, OLV 15 min, OLV 30 min, OLV 45 min, and OLV 60 min. Also, the intrapulmonary shunt (Qs/Qt), physiological dead space to tidal volume ratio (VD/VT), and oxygenation index (OI) were calculated and compared. Seventy-five patients consented to participate in this study. Dynamic compliance, peak inspiratory pressure (PIP), and plateau inspiratory pressure (Pplat) increased after PEEP titration during OLV. PIP, Qs/ Qt, and OI showed no differences among groups. Group PDYN showed lower Pplat, lower driving pressure, and higher dynamic compliance when compared with zero PEEP group. The PEEP titrating strategy according to dynamic compliance can improve respiratory mechanics, whereas it has no significant effects on oxygenation, dead space ratio, and intrapulmonary shunt, suggesting that it is better during OLV for thoracic surgery.

Real-time monitoring of electrochemically induced calcium carbonate depositions: Kinetics and mechanisms

Calcium carbonate (CaCO3) deposition plays a significant role in processes such as scale formation in power plants and in oil or gas production wells. The development of appropriate methods based on well suitable in situ sensors is important to evaluate and predict the deposition process. In this study, a combination of electrochemical techniques and quartz crystal microbalance with dissipation monitoring (QCM-D) in one analysis setup (EQCM-D) was used for the first time to monitor the CaCO3 deposition in real time and provide kinetic details of the CaCO3 deposition process. Through recording the frequency change of quartz crystal sensors, it allows us to perform a quantitative analysis of the morphology, coverage, deposition rate, and mass changes with nanogram sensitivity. By varying the applied voltage, it was found that a lower applied voltage resulted in more deposition of CaCO3 mass and increase of the thickness of the deposited layer. Under the absence of flow, the CaCO3 growth rate switched from accelerating to decelerating and this point is characterized by an inflection point (IP). A lower applied voltage resulted in a lower IP. Increasing Ca2+ and HCO3− concentrations, both the deposited amount of CaCO3 mass and coating thickness increased correspondingly. With the addition of 50 mM Mg2+, a reduction in the deposition rate of CaCO3 as high as 73% was achieved. The higher the Mg2+ concentration, the larger the deposition rate reduction, which was attributed to the incorporation of Mg2+ into the growing CaCO3 mineral, resulting in the reduction of growth sites (inhibiting effect). The obtained results contribute to a better understanding of electrochemically induced CaCO3 deposition and provide valuable insights into the determination of optimal precipitation parameters, with the aim to optimize industry scaling and anti-scaling processes.

Evidence of Air Trapping During Ex Vivo Lung Perfusion: A Swine Experimental Lung Imaging and Mechanics Study

Ex vivo lung perfusion (EVLP) allows the ventilation and perfusion of lungs to evaluate their viability for transplantation. The aim of this study is to compare the mechanical, morphologic and functional properties of lungs during EVLP with values obtained in vivo to guide a safe mechanical ventilation strategy.Lungs from 5 healthy pigs were studied in vivo and during 4 hours of EVLP. Lung compliance, airway resistance, gas exchange, and hemodynamic parameters were collected at positive end-expiratory pressure (PEEP) of 5 cm H2O. Computed tomography was performed at PEEP 0, PEEP 5, and total lung capacity (TLC). Lung pressure-volume (PV) curves were performed from PEEP 0 to TLC.Lung compliance decreased during EVLP (53 ± 5 mL/cm H2O vs 29 ± 7 mL/cm H2O, P < .05), and the PV curve showed a lower inflection point. Gas content (528 ± 118 mL vs 892 ± 402 mL at PEEP 0) and airway resistance (25 ± 5 vs 44 ± 9 cmH2O/L∗s-1, P < .05) were higher during EVLP. Alveolar dead space (5% ± 2% vs 17% ± 6%, P < .05) and intrapulmonary shunt (9% ± 2% vs 28% ± 13%, P < .05) increased ex vivo compared to in vivo, while the partial pressure of oxygen to inspired oxygen fraction ratio (PO2/FiO2) did not differ (468 ± 52 mm Hg vs 536 ± 14 mm Hg).In conclusion, during EVLP lungs show signs of air trapping and bronchoconstriction, resulting in low compliance and increased alveolar dead space. Intrapulmonary shunt is high despite oxygenation levels acceptable for transplantation.

Gravitational distribution of regional opening and closing pressures, hysteresis and atelectrauma in ARDS evaluated by electrical impedance tomography

BackgroundThe physiological behavior of lungs affected by the acute respiratory distress syndrome (ARDS) differs between inspiration and expiration and presents heterogeneous gravity-dependent distribution. This phenomenon, highlighted by the different distribution of opening/closing pressure and by the hysteresis of the pressure–volume curve, can be studied by CT scan, but the technique expose the patient to radiations, cannot track changes during time and is not feasible at the bedside. Electrical impedance tomography (EIT) could help in assessing at the bedside regional inspiratory and expiratory mechanical properties. We evaluated regional opening/closing pressures, hysteresis and atelectrauma during inspiratory and expiratory low-flow pressure–volume curves in ARDS using electrical impedance tomography.MethodsPixel-level inspiratory and expiratory PV curves (PVpixel) between 5 and 40 cmH2O were constructed integrating EIT images and airway opening pressure signal from 8 ARDS patients. The lower inflection point in the inspiratory and expiratory PVpixel were used to find opening (OPpixel) and closing (CPpixel) pressures. A novel atelectrauma index (AtI) was calculated as the percentage of pixels opening during the inspiratory and closing during the expiratory PV curves. The maximal hysteresis (HysMax) was calculated as the maximal difference between normalized expiratory and inspiratory PV curves. Analyses were conducted in the global, dependent and non-dependent lung regions.ResultsGaussian distribution was confirmed for both global OPpixel (r2 = 0.90) and global CPpixel (r2 = 0.94). The two distributions were significantly different with higher values for OPpixel (p < 0.0001). Regional OPpixel and CPpixel distributions were Gaussian, and in the dependent lung regions, both were significantly higher than in the non-dependent ones (p < 0.001). Both AtI and the HysMax were significantly higher in the dependent regions compared to the non-dependent ones (p < 0.05 for both).ConclusionsGravity impacts the regional distribution of opening and closing pressure, hysteresis and atelectrauma, with higher values in the dorsal lung. Regional differences between inspiratory and expiratory lung physiology are detectable at the bedside using EIT and could allow in-depth characterization of ARDS phenotypes and guide personalized ventilation settings.Graphic abstract

Influence of temperature dependent matrix properties on the high-rate impact performance of thin glass fiber reinforced composites

The influence of measurement temperature on the high velocity (>100 m/s) impact performance was investigated for three thermosetting epoxy resin S-2 glass composite systems. These three model resins were chemically similar but have different glass transition temperatures (Tg) and molecular weights between crosslinks (Mc) through the use of different diamine curing agents (Jeffamine® D230, D400, and D2000). Impact performance was quantified by the projectile kinetic energy absorbed (KE50) as calculated from the characteristic ballistic velocity (V50) of the composites during high velocity impact. Among the resin systems, the KE50 remained essentially constant over a broad range of temperatures for each composite set and modestly increased with decreasing Mc. The superficial damage area associated with delamination showed remarkable sigmoidal behavior as a function of the testing temperature relative to the Tg (T-Tg). Damage was high for low T-Tg values (glassy resin) and decreased as the resin traversed its Tg into the rubbery region. These damage area trends were found to depend on the resin Mc, with higher Mc values resulting in lower overall damage area and a lower inflection point temperature. High speed videography of the back surface of the samples showed that lower damage areas correlated with an increased back face deflection, which enabled energy absorption with relatively less delamination. Composite mechanical tests were performed to validate the impact performance and explain the deformation mechanisms observed during impact energy dissipation. Our results illustrate the critical importance of the resin architecture and temperature-dependent viscoelastic behavior on the impact properties of composites for impact-resistance applications.

Analysis of the spatial association network structure of China's transportation carbon emissions and its driving factors

Using the social network analysis method, this paper explores the characteristics of the spatial association network structure of China's provincial transportation carbon emissions from 2005 to 2015 and its driving factors. The results are as follows: (1) The spatial association of China's provincial transportation carbon emissions exhibits an intuitive network structure. The degree of closeness which were 0.2253 and 0.2333 in 2005 and 2015 respectively shows an increasing trend on the whole. However, it hit the bottom in 2011, reaching a minimum of 0.2230, which is the “low closeness degree inflection point”. (2) The spatial association network presents a significant “core-edge” distribution pattern. Specifically, in the central and eastern regions of China, Henan and Jiangsu have degrees of up to 58.621 and 44.828, which are at the network center. However, some remote regions, like Jilin and Hainan, have degrees of less than 20.000, which are marginalized. (3) The geographical adjacency, the expansion of the difference in R&D investment, and the narrowing of the difference in economic development promote the formation of the interprovincial spatial association. Therefore, in the process of controlling carbon emissions from transportation, the government should focus on the provinces at the network center and pay attention to the impact of the R&D investment on the spatial association of transportation carbon emissions.

Heterogeneity of regional inflection points from pressure-volume curves assessed by electrical impedance tomography

BackgroundThe pressure-volume (P-V) curve has been suggested as a bedside tool to set mechanical ventilation; however, it reflects a global behavior of the lung without giving information on the regional mechanical properties. Regional P-V (PVr) curves derived from electrical impedance tomography (EIT) could provide valuable clinical information at bedside, being able to explore the regional mechanics of the lung. In the present study, we hypothesized that regional P-V curves would provide different information from those obtained from global P-V curves, both in terms of upper and lower inflection points. Therefore, we constructed pressure-volume curves for each pixel row from non-dependent to dependent lung regions of patients affected by acute hypoxemic respiratory failure (AHRF) and acute respiratory distress syndrome (ARDS).MethodsWe analyzed slow-inflation P-V maneuvers data from 12 mechanically ventilated patients. During the inflation, the pneumotachograph was used to record flow and airway pressure while the EIT signals were recorded digitally. From each maneuver, global respiratory system P-V curve (PVg) and PVr curves were obtained, each one corresponding to a pixel row within the EIT image. PVg and PVr curves were fitted using a sigmoidal equation, and the upper (UIP) and lower (LIP) inflection points for each curve were mathematically identified; LIP and UIP from PVg were respectively called LIPg and UIPg. From each measurement, the highest regional LIP (LIPrMAX) and the lowest regional UIP (UIPrMIN) were identified and the pressure difference between those two points was defined as linear driving pressure (ΔPLIN).ResultsA significant difference (p < 0.001) was found between LIPrMAX (15.8 [9.2–21.1] cmH2O) and LIPg (2.9 [2.2–8.9] cmH2O); in all measurements, the LIPrMAX was higher than the corresponding LIPg. We found a significant difference (p < 0.005) between UIPrMIN (30.1 [23.5–37.6] cmH2O) and UIPg (40.5 [34.2–45] cmH2O), the UIPrMIN always being lower than the corresponding UIPg. Median ΔPLIN was 12.6 [7.4–20.8] cmH2O and in 56% of cases was < 14 cmH2O.ConclusionsRegional inflection points derived by EIT show high variability reflecting lung heterogeneity. Regional P-V curves obtained by EIT could convey more sensitive information than global lung mechanics on the pressures within which all lung regions express linear compliance.Trial registrationClinicaltrials.gov, NCT02907840. Registered on 20 September 2016.