Oxygen Tension Research Articles

Development and external validation of an interpretable machine learning model for the prediction of intubation in the intensive care unit

Given the limited capacity to accurately determine the necessity for intubation in intensive care unit settings, this study aimed to develop and externally validate an interpretable machine learning model capable of predicting the need for intubation among ICU patients. Seven widely used machine learning (ML) algorithms were employed to construct the prediction models. Adult patients from the Medical Information Mart for Intensive Care IV database who stayed in the ICU for longer than 24 h were included in the development and internal validation. The model was subsequently externally validated using the eICU-CRD database. In addition, the SHapley Additive exPlanations method was employed to interpret the influence of individual parameters on the predictions made by the model. A total of 11,988 patients were included in the final cohort for this study. The CatBoost model demonstrated the best performance (AUC: 0.881). In the external validation set, the efficacy of our model was also confirmed (AUC: 0.750), which suggests robust generalization capabilities. The Glasgow Coma Scale (GCS), body mass index (BMI), arterial partial pressure of oxygen (PaO2), respiratory rate (RR) and length of stay (LOS) before ICU were the top 5 features of the CatBoost model with the greatest impact. We developed an externally validated CatBoost model that accurately predicts the need for intubation in ICU patients within 24 to 96 h of admission, facilitating clinical decision-making and has the potential to improve patient outcomes. The prediction model utilizes readily obtainable monitoring parameters and integrates the SHAP method to enhance interpretability, providing clinicians with clear insights into the factors influencing predictions.

Study on the clinical characteristics, treatment, and outcome influencing factors of severe pneumonia complicated with ARDS.

To investigate the clinical characteristics, treatment methods, and factors influencing the prognosis of patients with severe pneumonia complicated by Acute Respiratory Distress Syndrome (ARDS), aiming to provide references for clinical decision-making and improve patient outcomes. A retrospective analysis was conducted on 118 patients with severe pneumonia complicated by ARDS treated at our hospital from June 2018 to December 2022. Based on treatment outcomes, patients were divided into a death group (n = 75) and a survival group (n = 43). General data and clinical laboratory indicators, including blood urea nitrogen, serum creatinine, C-reactive protein, procalcitonin, arterial partial pressure of oxygen, and arterial partial pressure of carbon dioxide, were collected and compared between the 2 groups to identify independent factors affecting prognosis. Among the 118 patients, the mortality rate was 63.56%. Patients in the death group had a significantly higher average age (57.15 ± 13.38 years) and a higher proportion of severe ARDS (66.67%) compared to the survival group (40.02 ± 11.41 years, 30.23%, P < .001). The death group had significantly lower white blood cell counts (8.10 ± 1.64 × 109/L), oxygenation index (19.82 ± 2.29), and duration of mechanical ventilation (7.79 ± 2.11 days) compared to the Survival group (8.92 ± 1.22 × 109/L, 13.42 ± 1.82, 12.23 ± 3.05 days, P < .05). Conversely, the death group had significantly higher levels of blood urea nitrogen (6.87 ± 1.80 mmol/L), C-reactive protein (130.55 ± 50.28 mg/L), procalcitonin (5.50 ± 2.11 ng/mL), arterial partial pressure of carbon dioxide (41.12 ± 5.56 mm Hg), and a higher proportion of viral infections (48.00%) compared to the survival group (5.90 ± 1.72 mmol/L, 101.77 ± 55.56 mg/L, 3.98 ± 1.15 ng/mL, 35.59 ± 6.22 mm Hg, 27.91%, P < .05). Logistic regression analysis revealed that age (odds ratios [OR] = 1.990, 95% confidence interval [CI]: 1.306-3.033, P < .001), oxygenation index (OR = 1.426, 95% CI: 1.123-1.649, P < .001), and duration of mechanical ventilation (OR = 0.694, 95% CI: 0.557-0.864, P < .001) were independent factors influencing patient prognosis. This indicates that an increase in age and a decrease in oxygenation index are associated with a significantly higher risk of mortality, while shorter mechanical ventilation duration is related to poorer prognosis. Advanced age, lower oxygenation index, and shorter duration of mechanical ventilation are unfavorable prognostic factors in patients with severe pneumonia complicated by ARDS. These findings aid clinicians in identifying high-risk patients, optimizing treatment plans, and improving patient prognosis.

The impact of Tanreqing injection on mucus hypersecretion and cough in bronchiectasis: A meta-analysis of randomized controlled trials.

Bronchiectasis clinically manifests airway mucus hypersecretion as mucopurulent sputum production and chronic cough. In the past decade, Tanreqing injection (TRQ) has been often used in clinical practice as an add-on treatment for bronchiectasis in China. Several in vivo studies have indicated that TRQ is effective in improving sputum expectoration and cough in acute exacerbation of bronchiectasis but results of individual studies are inconsistent. Therefore, systematically and critically evaluating the effectiveness and safety of TRQ on mucus hypersecretion and cough in bronchiectasis is necessary. Randomized controlled trials examining the treatment of bronchiectasis with TRQ were systematically searched from databases including PubMed, Cochrane Library, Embase, Web of Science, Chinese National Knowledge Infrastructure, Vip Information Database, Wanfang data, and Chinese Biomedical Literature Database, based on a preregistered protocol and adhering to Cochrane methods. Pertinent data were taken out from the included studies and a methodological quality assessment was done. R language (version 4.4.1) was used to perform the meta-analysis. Twenty randomized controlled trials involving 1544 patients were analyzed. The results demonstrated that TRQ significantly improved mucus hypersecretion, shortened the duration of cough and phlegm, reduced symptom scores, and enhanced both forced expiratory volume in 1 second and forced vital capacity. Additionally, TRQ effectively lowered inflammatory markers, including C-reactive protein, procalcitonin, white blood cell count, neutrophil count, interleukin-6, and tumor necrosis factor-alpha. Moreover, TRQ increased the partial pressure of oxygen and decreased carbon dioxide pressure. The findings suggest that TRQ positively impacts mucus hypersecretion and mucociliary clearance, leading to improvements in sputum production and cough during bronchiectasis exacerbations, without increasing the risk of adverse effects. TRQ may be considered a viable option for managing bronchiectasis and could serve as a novel mucus-modifying agent.

Hot Uniaxial Pressing and Pressureless Sintering of AlCrCuFeMnNi Complex Concentrated Alloy-A Comparative Study.

External pressure is often applied during sintering to obtain materials with improved properties. For complex concentrated alloys (CCAs), this processing step is commonly performed in vacuum. However, this can promote the evaporation of elements and increase the oxide content, thereby degrading the properties of the alloy. In this study, we compared the microstructures and properties of AlCrCuFeMnNi CCA samples obtained by hot uniaxial pressing sintering (HPS) and pressureless sintering (PLS) using a helium atmosphere purified by an oxygen getter system. The powders were prepared from mixtures of CrFeMn, AlNi and Cu and sintered by HPS at 900 °C for 1 h with an applied pressure of 30 MPa and by PLS at 1050 °C for 1 h. The samples were characterised using X-ray diffraction, scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron backscattering diffraction, density measurements and hardness tests. It was found that the oxygen getter system promoted oxygen partial pressure values at sintering temperatures similar to those of a mixture of 90% helium and 10% hydrogen. The HPS allowed us to obtain almost fully dense samples with a smaller average grain size and finer distribution of aluminium oxides than PLS. These differences increased the hardness of the samples sintered under pressure.

Impact of low-grade iron ore on sintering reactions: Rapid heating experiments and thermodynamic modeling

BackgroundSinter is a primary feedstock for blast furnace-based ironmaking. Recently, the proportion of low-grade iron ore, which contains a high amount of gangue (mainly SiO2), has been increasing in the sintering process. Therefore, the impact of increased SiO2 content on the quality of sinter needs to be clarified. MethodsIn this study, we designed a rapid-heating furnace to simulate the actual thermal profile of the sintering process. The effects of basicity values, sintering temperature, and atmosphere, on the microstructure and phase formation of the Fe2O3-CaO-SiO2 ternary mixtures during sintering reactions, are investigated using X-ray diffractometry and scanning electron microscopy. The experimental results are analyzed using CALPHAD-type computational thermodynamics. Significant findingsWe found that solid-state reactions dominate at the lower temperature of 1250 °C, while liquid-assisted sintering occurs at the higher temperature (1300 °C). As the SiO2 content in the sinter increases, the content of the calcium-ferrite bonding phase decreases, while the content of Ca2SiO4 and Fe2O3 increases. Regarding the role of the atmosphere, more calcium ferrite bonding phases form under a lower oxygen partial pressure compared to an ambient atmosphere, which facilitates the densification of the Fe2O3-CaO-SiO2 sinter. In addition, a guideline for sintering operation with low-grade iron ore is proposed.

Electrical properties and redox stability of series novel high-entropy Bi2VO5.5-based oxides

Exceptional high ionic conductivities have been well documented in the Bi2VO5.5-based materials. However, the poor phase and redox stabilities under a reducing atmosphere hindered their wide applications. Herein, with the aim to improve the phase and redox stabilities under a reducing atmosphere, a high-entropy strategy of multiple-metal-doping was applied to prepare series Bi2V1–4x(GaSiTaZr)xO5.5-δ (0 ≤ x ≤ 0.1) materials by a traditional solid state reaction method. The results revealed that multiple-metal-doping could stabilize the tetragonal phase of Bi2VO5.5 to room temperature and shown good phase and structural stabilities under inert or high oxygen partial pressure atmospheres, as well as pure oxide ion conduction which was about two orders of magnitude higher than that of the parent material, e.g. ∼2.0×10−2 S/cm at 400 ºC for the x = 0.05 sample while ∼1.5×10−4 S/cm for the x = 0 sample. Although the Bi2V1–4x(CuNiNbTi)xO5.5-δ materials would still be readily reduced under a reducing environment and introduce strong electronic conduction, the phase stability was apparently improved. Thus, improving the redox stability and suppressing the electronic conduction of the stabilized Bi2VO5.5-based materials under a reducing atmosphere is still the direction we should strive for.

Impact of intracranial hypertension and cerebral perfusion pressure on spreading depolarization.

Spreading depolarization (SD) develops after stroke and traumatic brain injury and may contribute to secondary brain damage. These diseases are often accompanied by intracranial hypertension, but little is known about the effects of intracranial pressure (ICP) on SD. Here, we study the effect of increased ICP on hemodynamic and metabolic response to SD in rats. SDs were triggered at different ICPs and cerebral perfusion pressures (CPP). The regional cerebral blood flow (rCBF), partial pressure of brain tissue oxygen (PbtO2), cerebral extracellular glucose and lactate concentrations were recorded. Fluoro-Jade staining was used to quantify neuronal injury in cortex. At high ICP (50 mmHg) with low CPP (30 mmHg), rCBF and PbtO2 were monophasically decreased in contrast to a monophasically increased pattern under normal conditions. Neuronal death increased in both hemispheres but much more on the side where SDs were triggered. At high ICP (50 mmHg) with normal CPP (70 mmHg), CBF and metabolism during SD did not differ from baseline, and neuronal death did not increase even on the side of SD induction. These data suggest that maintaining CPP at 70 mmHg, even when the ICP is as high as 50 mmHg, preserves normal blood flow and metabolism during SD events and prevents neuronal degeneration.

Early Stages of High‐Temperature Oxidation Behavior and Its Phase Evolution of 9% Ni Steel

Herein, the effects of oxygen partial pressure (5–20%) and oxidation time (0.5–6 h) on the growth behavior and phase structure of 9% Ni steel oxide layer are studied by means of high‐temperature oxidation experiment, scanning electron microscopy, and X‐ray diffraction. The results show that the inner and outer oxide layers of 9% Ni steel grow opposite to each other along the initial surface direction of the vertical matrix during the high‐temperature oxidation process. From the perspective of the phase, the phase transition of Fe2O3→Fe3O4→FeO mainly undergoes from the outside and the inside, the results of thermodynamic calculations show that &lt;&lt;&lt;0, and the main factor affecting the phase transition is the diffusion concentration of free O and Fe atoms. During the high‐temperature oxidation process of 9% Ni steel, the diffusion of O and Fe atoms along grain boundaries promotes preferential oxidation at these boundaries. The columnar structure formed in the outer oxide layer of 9% Ni steel may be related to the uneven diffusion rate of Fe atoms at different positions at the interface between the inner and outer oxide layers.

Model development for real oxygen delignification processes

Previous extensive work has been done on modeling the oxygen delignification process, based on how the basic parameters, i.e., temperature, kappa number, concentration of alkali, and concentration of oxygen, affect the delignification rate. However, these models are not used extensively to evaluate the performance of real processes, primarily because they have not been able to properly consider all the essential issues affecting delignification in practice. Such issues include the mass transfer and consumption of oxygen, which defines the concentration of dissolved oxygen in the process, and the effect of that concentration on the delignification rate. In this paper, a new way to model the oxygen delignification process is used in which these parameters, among other smaller matters, are taken into account. The basic model and its parameters were defined by the information obtained from the literature, delignification made in the laboratory tests, and mill processes and mill tests. An essential aspect of these studies was the information obtained from the oxygen concentration measured in the residual gas obtained from the top of the reactor. With the aid of this measurement, it was possible to define more accurately the consumption of oxygen and partial pressure of oxygen that define the concentration of dissolved oxygen in the reactor. Using mill experiments, a model was formed that predicts the operation of the oxygen delignification process. The model was used to show how much the process could be improved by optimizing the charge of the oxygen. The mill experiments also confirmed that mass transfer of oxygen is modeled correctly enough, except when the charge of oxygen is very low and/or the mixing is not efficient enough. In that case, there is variation in the concentration of oxygen in the process that should be taken into account in the modeling.

Oxygen sensing in the kidney.

The kidneys fulfil several essential homeostatic functions for the body. One of them is the maintenance of sufficient oxygen supply to the organs. For this purpose, the kidneys control the formation of red blood cells by the production of the hormone erythropoietin. This control of red cell formation is not only relevant to prevent states of oxygen deficiency but also to prevent an unwanted increase of red cell numbers causing thromboembolic risks. The adequate production of erythropoietin requires a sensing of the arterial oxygen content and transduction to hormone production. This oxygen sensing is a two-step process which includes a translation of the arterial oxygen content to respective oxygen tension in the tubulointerstitium and a perception of the resulting local interstitial oxygen tension to translate them into specific cellular responses such as the production of erythropoietin. This contribution will describe these steps of oxygen sensing for the healthy kidney and for the changes occurring during states of chronic renal disease, which are commonly associated with anemia. In this context a special focus will also be set on intrarenal hypoxia and oxygen sensing in the diabetic kidney including the treatment with tubular glucose transport (SGLT-2) inhibitors which might influence the oxygen sensing in the kidney. Finally, we will consider the effects of prolylhydroxylase inhibitors (PHD-I), which fundamentally interfere with the cellular oxygen sensing and which are meanwhile treatment options in renal anemia.

Efficacy of Cytoreg in the treatment of diabetic foot disease.

Complications from diabetic foot wounds, including bacterial infection, ulceration and gangrene, are major causes of hospitalisation and are responsible for 85% of amputations in patients with diabetes. Given that orally administered investigational therapeutic Cytoreg (Cytorex de Venezuela SA, Venezuela), a defined aqueous mixture of hydrofluoric, hydrochloric, sulfuric, phosphoric, citric and oxalic acids, has been shown to increase levels of arterial blood oxygen in a Wistar rat model, oral and oral+topical Cytoreg were tested on patients with diabetic foot ulcers (DFUs) under a humanitarian, compassionate-use protocol. All patients received oral Cytoreg (5.0 ml concentrate in fruit juice) for 30 days; half also received weekly wound washing with Cytoreg concentrate in isotonic saline (1:50 volume/volume) (oral+topical group). In addition to standard clinical observations, wounds were monitored against the Saint Elian checklist system for the diabetic foot. A total of 10 patients took part in the study. Complete wound closure was observed in 4/5 patients in the oral+topical group; in the remaining patient, necrotic and fibrin tissues on the wound edges were eliminated. Half (2/4) of the patients receiving oral-only Cytoreg experienced complete wound closure; one patient in this group was removed prematurely because of an unrelated illness and was not replaced. During the study, no significant differences were observed between groups in either the oxygen saturation of the affected tissues or in insulin and glycaemia levels (p<0.05). Significant increases in arterial haemoglobin and arterial oxygen partial pressure (p<0.05) were observed, and significant decreases were measured in the levels of glycosylated haemoglobin, aspartate aminotransferase, glutamic-pyruvic transaminase, creatine and urea (p<0.05). The results of this study justify an expanded clinical study for the treatment of DFUs with Cytoreg.

On the product phases and the reaction kinetics of carbothermic reduction of UO2+C at relatively low temperatures

The synthesis of UC using carbothermic reduction of UO2 and C mixtures has been well studied at high temperatures. However, the product phase behavior of carbothermic reduction at low temperatures (≤1773 K) is not well studied. Such a study is important as low temperatures permit single phase UC synthesis without forming secondary higher carbides, and it further supports the knowledge base of the process that needs to be used for transuranic elements such as plutonium that have high vapor pressures at elevated temperatures. Therefore, a low temperature carbothermic reduction of two different C/UO2 molar ratios under inert and reducing environments have been studied here. Two different sample holding crucibles, alumina (Al2O3) and graphite, were also used here to differentiate the hypostoichiometric (UC1-a) and oxygen dissolved (UC1-xOx) uranium monocarbide phases adding more details on the two systems. Also, the reaction kinetics involved in the formation of UC via the carbothermic reduction of UO2+C using product phases instead of evolved gases such as carbon monoxide is reported here. Under inert atmospheres but with significant oxygen partial pressures, the low temperature carbothermic reduction of UO2+C produced up to 90 wt.% UC1-xOx type oxycarbides as was confirmed by Xray powder diffraction. Reducing Ar-4%H2 environments at these temperatures were not successful in synthesizing UC as it reduces the amount of C required for the carbothermic reduction, leaving UC phase at a non-equilibrium state. Inert atmospheres with low or negligible oxygen partial pressures on the other hand produced near stoichiometric UC at high phase purity, especially at 1673 – 1773 K temperature range. An activation energy of 377±75 kJmol-1 was also calculated using product phase concentrations of the carbothermic reduction of UO2+C under these inert Ar(g) atmospheres.

Deletion of both anaerobic regulator genes fnr and narL compromises the colonization of Salmonella Typhimurium in mice model.

Salmonella Typhimurium (STM), a zoonotic pathogen, can adjust its metabolic pathway according to the variations in the partial pressure of atmospheric oxygen and nitrate via fumarate nitrate reductase regulator (Fnr) and NarL, the response regulator for nitrate reductase. Both Fnr and NarL have been individually reported to be the contributors of virulent phenotypes of STM. Hypoxia along with nitrate-rich environment are prevalent in macrophages and the Salmonella-induced inflammatory lumen of the host's large intestine activates both fnr and narL genes. In this study, the double (fnr and narL) knockout STM showed a synergistic reduction in the swimming (62%), swarming (84%) and biofilm density (86%) phenotypes anaerobically in association with its significant aerobic attenuation. The intracellular replication of the double mutant was reduced by 2.3 logs in chicken monocyte-derived macrophages. Furthermore, the competitive index of the double mutant in liver and spleen was found to be 0.3 and 0.44 respectively at 120h post-infection (PI) in mice. Surprisingly, no double mutant could be recovered from the infected mouse liver 3 days PI. Histopathological findings showed moderate infiltration of mononuclear cells in the large intestine of mice infected with double mutant, but severe infiltration was seen with the wild-type strain.

An underrecognized phenotype of pulmonary emphysema with marked pulmonary gas exchange but with mild or moderate airway obstruction

In patients with pulmonary emphysema and mild to moderate airflow limitation, one does not expect the features marked exertional dyspnea and hypoxemia as well as a profound decrease in diffusing capacity of the lung for carbon monoxide (DLCO). Here we describe this phenotype and its prognosis. From our database, we retrospectively selected cases associating emphysema, exertional breathlessness, O2 requirement at least upon exercise, forced expiratory volume in 1 sec (FEV1) ≥ 50% predicted, and DLCO ≤ 50% predicted, without associated combined pulmonary fibrosis and emphysema, right-to-left shunt, or severe pulmonary hypertension. Over a 12-year period, we identified 16 patients with emphysema and the above presentation. At the initial evaluation, the median age was 62 years (interquartile range 53.8–68.9). The median FEV1 and DLCO% predicted and mean pulmonary artery pressure were 86 (65–95)%, 38 (31–41)%, and 20 (17–25) mm Hg, respectively. On room air, the median arterial partial pressure of oxygen and partial pressure of carbon dioxide in arterial blood were 63.5 (55.8–69) mm Hg and 34.5 (31–36) mm Hg with increased median alveolar-arterial oxygen difference (46 [39–51] mm Hg). After the initial evaluation, the respiratory condition worsened in 13 of 14 (92.8%) patients with one or more re-evaluations (median follow-up 2.6 [0.9–5.8] years). In 12, lung transplantation was considered. Four patients died after 5.8, 5.7, 7.1, and 0.8 years of follow-up, respectively. We describe an underrecognized phenotype of pulmonary emphysema featuring a particular profile characterized by marked exertional dyspnea, impaired pulmonary gas exchange with low DLCO and marked oxygen desaturation at least on exercise but with mild or moderate airway obstruction.

Amorphous NiO nanopyramids with superior electrochromic energy storage properties

In this work, amorphous NiO nanopyramid film has been obtained by using the pulsed magnetron sputtering technique. The uniform amorphous NiO nanostructures exhibit significant electrochromic modulation efficiency in the visible and near-infrared ranges, achieving a high modulation efficiency of 60.73 % at 550 nm and 21.58 % at 1500 nm. It exhibits rapid response time (coloring takes 2.4 s, and bleaching takes 1.0 s) and significant coloring efficiency (43.23 cm2C-1). Moreover, amorphous NiO nanopyramid film displays promising properties of energy storage. The NiO nanopyramid film shows high areal capacitance (7.08 mF/cm2), along with satisfying rate capability. The alteration in the electrode color offers a convenient method for monitoring the quantity of energy stored. Furthermore, the microstructure characteristic, degree of crystallization and electrochemical performance of the NiO film are significantly influenced by both oxygen partial pressure and sputtering time. These findings highlight the potential of employing this bifunctional amorphous NiO nanopyramid film in diverse advanced nanodevices, encompassing electrochromic energy storage applications with superior performance.

Multiplet XPS analysis of the Mn 2p for Mn3O4 thin films

In this work, we performed a detailed analysis of the x-ray photoemission spectroscopy (XPS) of the Mn 2ppeak for Mn3O4(001) thin films. This is a challenging task since Mn3O4is composed of two different cations, Mn2+at tetrahedral and Mn3+at octahedral sites, which both contribute to the XPS spectra. The oxide spectra consist of many multiplets arising from the angular momentum coupling of the open Mn 2pand 3dshells, thus increasing the spectrums' complexity. Moreover, the energy spacing and intensities of the different multiplets also reflect the covalent mixing between Mn 3dand O 2pshells. However, we show that a detailed analysis, which provides relevant information about the cations in the oxide structure, is possible. We prepared experimentally different Mn3O4films on Au(111), and their structure was monitored with the diffraction pattern obtained with low-energy electron diffraction. The Mn 2pspectra were fit, guided by cluster model theoretical predictions, and checked for films prepared at different oxygen partial pressures. Therefore, we could observe the Mn2+and Mn3+cations' relative concentration in the Mn 2pmains peaks.

Risk Factors for INtubation-SURfactant-Extubation Failure in Infants With Neonatal Respiratory Distress Syndrome

To identify clinical characteristics predictive of failure or success of the INtubation-SURfactant-Extubation (INSURE) strategy, to distinguish infants who could be managed using this strategy to prevent mechanical ventilation (MV). Infants with a gestational age <32 weeks were classified into two groups according to whether they required reintubation and MV within 72 h after birth. The clinical characteristics of the two groups were subsequently analyzed. INSURE was unsuccessful in 77 infants (20.7%). Infants in the INSURE failure group had a higher incidence of severe respiratory distress syndrome, as evidenced by radiological grade; lower blood pH, partial oxygen pressure, and base excess (BE) levels; higher partial carbon dioxide pressure levels at the first arterial blood gas analysis; lower Apgar scores at 1 and 5 min; lower use of antenatal steroids; and higher occurrence of gestational diabetes mellitus, versus those in the INSURE success group. Multiple regression analysis confirmed severe radiological grade, lower BE levels at the first arterial blood gas analysis, and decreased use of antenatal steroids as independent risk factors for INSURE failure. Compared with infants in the INSURE success group, those in the INSURE failure group also had higher mortality. We successfully identified specific predictors of an unsuccessful INSURE strategy. Maintaining high-risk preterm infants with one or several predictors intubated and treated with MV after surfactant administration can prevent reintubation and reduce mortality.

Uniaxial static strain enhances osteogenic and angiogenic potential under hypoxic conditions in distraction osteogenesis

ObjectiveBone incision leads to interrupted and sluggish blood flow in the process of distraction osteogenesis (DO), creating a hypoxia (0–2% oxygen tension) at the center of the bone callus. This hypoxia is critical in the coupling of osteogenesis and angiogenesis during DO. This study aimed to investigate the effect of Uniaxial Static Strain (USS) on osteogenesis in osteoblasts under hypoxic conditions, with a focus on the expression of osteogenic markers and angiogenic factors.MethodsThe USS was made by a multi-unit tension compression device.Osteoblasts were subjected to 10% USS made under hypoxic conditions to mimic the process of DO in vitro. The cell proliferation, alkaline phosphatase (ALP) activity, mineralized nodule formation, and expression of osteogenic and angiogenic markers were evaluated by using a CCK-8 assay, alkaline phosphatase (ALP) staining, ALP activity assay, alizarin red S staining, qRT-PCR, Western blotting and ELISA.ResultsHypoxia inhibited osteoblast cell proliferation, ALP activity, mineralized nodule formation, and the expression of runt-related transcription factor 2 (Runx- 2), osteopontin(OPN), osteocalcin (OCN), collagen type I (Col1a1). Conversely, hypoxia upregulated the expression of hypoxia-inducible factor 1-alpha (HIF-1α) and vascular endothelial growth factor (VEGF), which are associated with angiogenesis. However, the application of USS enhanced osteoblasts’ osteogenic capacity and upregulated angiogenic factors under hypoxic conditions.ConclusionUSS can enhance osteogenesis in osteoblasts under hypoxic conditions. Moreover, it may stimulate angiogenesis by promoting the expression of VEGF, which further contributes to bone formation. This finding provides important implications for understanding the mechanisms involved in bone regeneration and may have clinical applications in optimizing the effectiveness of DO techniques.

Electrochemical characterization of Bi3Ru3O11 – 40 wt% Bi1.6Er0.4O3 as an EOG electrode material

This paper reports on the study of the electrochemical behavior of porous Bi3Ru3O11 – 40 wt% Bi1.6Er0.4O3 electrodes on a Bi2O3 – 10 wt% Bi24B2O39 electrolyte in a symmetric cell configuration by impedance spectroscopy. The dependence of the area specific resistance (ASR) for electrode polarization on the partial pressure of oxygen replaced from PO2−1/2 to PO2−3/4 with decreasing thickness of the layer, which inhibited wetting. This indicates a change in the rate-limiting oxidation-reduction reactions of oxygen. It is assumed that the dissociation of adsorbed oxygen molecules on the active catalytic centers of the triple phase boundary (TPB) is the limiting stage of a surface oxygen exchange, and with a decrease in the layer thickness, additional difficulty in the transfer of gaseous oxygen molecules from the gas phase to these active catalytic centers is observed.

Discrepancy Between Pulmonary Artery Catheter and Co-Oximeter Value of Mixed Venous Oxygen Saturation After Graft Reperfusion During Living Donor Liver Transplantation

Monitoring tissue oxygenation is critical in liver recipients. The pulmonary artery catheter (PAC) provides continuous monitoring of mixed venous oxygen saturation (SvO2) using fiberoptic reflectance spectrophotometry. Despite the need for in vivo calibration during liver transplantation, recalibration guidelines are absent, and we frequently observed a significant discrepancy between PAC and reference co-oximeter SvO2 values after graft reperfusion. This study aimed to assess the incidence and risk factors of a significant discrepancy after reperfusion during living donor liver transplantation. This retrospective study included 54 recipients who underwent living donor liver transplantation at our institution between October 2021 and April 2022. A PAC was inserted, and in vivo calibration was conducted using the co-oximeter SvO2 value. We defined a significant discrepancy as a drift was ≥ 3% at 1 hour after reperfusion. Logistic regression analysis was performed to determine the association between perioperative variables and the risk of significant discrepancy. PAC SvO2 was higher than co-oximeter SvO2 in 51 recipients. A significant discrepancy was observed in 37 recipients (68.5%). The risk of significant discrepancy decreased with a high preoperative hemoglobin concentration (odds ratio [OR] = 0.65 [0.47-0.91], P = .011) and a high arterial oxygen partial pressure (PaO2) at 1 hour after reperfusion (OR = 0.96 [0.94-0.99], P = .004) but increased with a high baseline co-oximeter SvO2 value (OR = 1.29 [1.05-1.59], P = .015). PAC SvO2 significantly drifted from the reference co-oximeter value in over two-thirds of recipients after reperfusion. Therefore, in vivo recalibration is required for the reliable measurement of PAC SvO2 during living donor liver transplantation.