FiO2 Research Articles

Otolith-temperature estimates in Atlantic bluefin tuna (Thunnus thynnus) from the Mediterranean Sea: Insights from clumped isotope measurements

The subpopulation and/or contingent structure of Atlantic bluefin tuna (Thunnus thynnus) within the Mediterranean Sea is undefined, leading to uncertainty regarding the best strategy for an effective assessment and management of this highly exploited stock. This study aimed to reconstruct temperatures experienced by Atlantic bluefin tuna during the early life period (<3.5 months) using clumped isotope temperature proxy, an innovative geothermometer for carbonates, that does not require previous knowledge of other environmental parameters such as water oxygen composition. We examined otolith chemistry in fish captured from 3 different areas of the Mediterranean Sea and adjacent waters. We found that mean seasonal temperature estimates from clumped isotopes did not differ significantly from satellite derived and otolith oxygen stable isotopic ratios derived temperatures, except for the central Mediterranean Sea, were clumped isotopes derived temperatures were significantly higher than satellite derived temperatures. However, the sensitivity of the clumped isotope thermometer was found to be lower than that based on oxygen fractionation equation, with high variance observed in the clumped isotopes derived temperature estimates. We also observed that clumped isotope derived temperatures were undistinguishable among bluefin tuna captured in the Gibraltar Strait, the central, and eastern Mediterranean Sea. In this paper, we discuss the major sources of uncertainty in temperature reconstructions using bluefin tuna otoliths.

Maturity characterization of soot in laminar coflow diffusion flames of methane/anisole under different oxygen indices

Anisole fuel has gained increased attention, since it is considered a biofuel, and its addition to gasoline increases the octane number, improving the engine performance. This study focuses on the comprehensive characterization of soot maturity and sooting propensity of a well-controlled laminar coflow diffusion flame fueled with anisole and using methane as the carrier gas. Four laminar non-premixed flames were established below the smoke point. The oxidizer composition ranged from a molar fraction of oxygen (oxygen index, OI) of 21% to 35% (doped with pure oxygen), while keeping constant the total volumetric flow rate of oxidizer stream. Multi-wavelength line-of-sight attenuation experiments were performed from visible to infrared wavelengths, and the measurements of the extinction coefficient and flame temperature were used to retrieve two dimensional fields of soot temperature, volume fraction, radiative intensity and degree of soot maturity. In general, the sooting propensity and radiative behavior of the anisole flames follows a similar trend than typical hydrocarbon fuels when increasing the OI. However, the spatial distribution of soot volume fraction is enhanced, particularly near the flame centerline. In contrast, the soot production is promoted by the OI, near the flame wings. The same effect can be observed for the soot temperature. Indeed, temperature increases, promoting formation and oxidation processes, specially at the locations near the maximum soot volume fraction. In general, the maturity of soot particles is affected as the OI is changed. Also, it is observed that the degree of maturity is enhanced by flame temperature. In order to support these local observations, a statistical analysis was carried out. Finally, the results obtained yield a curated database for validating detailed soot production models of oxygenated fuels, and to gain further insights on the evolution of soot maturity and propensity of these particular fuels under different oxidizer conditions.

Pulmonary vasoconstriction plays a major role in the acute phase of pulmonary embolism in pigs

Abstract Background Pulmonary vascular resistance (PVR) increases in acute pulmonary embolism (PE) due to both mechanical obstruction and pulmonary vasoconstriction. Attenuation of adverse pulmonary vasoconstriction has shown promise as a treatment of acute PE in experimental studies. However, clinical trials have failed to replicate these beneficial effects in PE patients. Time may be a factor in this discrepancy between experimental and clinical studies. In experimental PE studies, PVR acutely increases and decreases within hours. Meanwhile in clinical trials, the time from symptom onset to study inclusion is often days, at which time PVR may already be decreased. Whether this decrease in PVR is due to reduced mechanical obstruction by endogenous fibrinolysis or attenuation of adverse pulmonary vasoconstriction is unknown. Purpose To investigate the contribution of the mechanical obstruction and pulmonary vasoconstriction to PVR in two days following PE in pigs. Methods In a controlled animal study, using an estabilished model of autologous PE in pigs (PE, n=12 ∼60 kg), changes in pulmonary hemodynamics and clot burden were evaluated. CT pulmonary angiograms were performed at baseline (BL), after acute PE and the following two days, quantifying clot burden using the Qanadli Obstruction Score. Hemodynamics were evaluated with real-time biventricular catheterization and systemic invasive pressures. To evaluate the vasoactive component, pulmonary vasodilators sildenafil (bolus 0.1 mg/kg) and oxygen (inspired fraction of oxygen 40%) were administered. Results Following PE, both mean PVR (Figure 1A) and pulmonary obstruction scores (Figure 1B) increased. PVR decreased at day one and remained unchanged at day two (Figure 1A). Meanwhile, mean obstruction score decreased slightly at day one but remained elevated throughout the study (Figure 1B). Vasodilatation induced by sildenafil and oxygen (SIL+OXY) decreased PVR at day zero but displayed no effect on the subsequent days (Figure 1A). Conclusion Pulmonary vasoconstriction and mechanical obstruction both contributed to the increase in PVR during the acute phase of PE. PVR decreased towards levels of baseline already day one and remained unchanged at day two. The contribution of pulmonary vasoconstriction decreased at day one and two, while the mechanical obstruction remained significantly increased. Accordingly, the effects of pulmonary vasodilators were only present in the acute phase of PE.Figure 1

Plasma-catalytic removal of toluene over bimetallic M/Mn-BTC catalysts in dielectric barrier discharge reactor

In this study, novel bimetallic metal–organic frameworks (MOFs) catalysts were synthesized using a simple solvothermal method. These catalysts involved the incorporation of transitional metals such as Co, Cu, Ce, and Fe into Mn-BTC, which served as the precursor substrate. This approach was undertaken to address the limitations of catalytic degradation of toluene observed in both plasma-based and traditional catalytic materials. The physicochemical characterization confirmed successful synthesis of the bimetallic MOFs with well-defined crystal shape and structure. In toluene degradation experiments, the DBD-coupled bimetallic MOFs (M/Mn-BTC) presented higher toluene removal efficiency, CO2 selectivity, mineralization degree, and fewer by-products when compared to both DBD-coupled single metal MOFs and the DBD-alone system. Besides, the catalytic activity of the DBD-coupled M/Mn-BTC followed the order: Co/Mn-BTC > Cu/Mn-BTC > Ce/Mn-BTC > Fe/Mn-BTC. Furthermore, it was observed that the Co/Mn molar ratio played a significant role in influencing the properties of MOFs catalysts and subsequently had an impact on their performance. The highest catalytic activity was observed at a Co/Mn molar ratio of 1:1. Under conditions of an energy density of 808.99 J‧L-1 and an oxygen fraction of 4% (v/v), Co/Mn-BTC exhibited a CO2 selectivity of 54.1%, a mineralization degree of 93.9%, and a toluene abatement efficiency of 96.2%. Additionally, an energy efficiency of 8.32 g·kWh−1 was achieved. The mechanism of toluene degradation was analyzed, uncovering a synergistic effect between DBD and Co/Mn-BTC. High-energy electron and adsorbed oxygen (denoted as Oads), along with active oxygen species (O*) from O3 decomposition, played crucial roles in the catalytic oxidation reaction. The interactions between Mn and Co enhanced electron mobility and accelerated the formation of Oads and O*, thereby facilitating toluene oxidation within the hybrid catalytic system.

Impact of Positive End-Expiratory Pressure and FiO2 on Lung Mechanics and Intrapulmonary Shunt in Mechanically Ventilated Patients with ARDS Due to COVID-19 Pneumonia.

Purpose: This study aimed to investigate the effects of inspired oxygen fraction (FiO2) and positive end-expiratory pressure (PEEP) on gas exchange in mechanically ventilated patients with COVID-19. Methods: Two FiO2 (100%, 40%) were tested at 3 decreasing levels of PEEP (15, 10, and 5 cmH2O). At each FiO2 and PEEP, gas exchange, respiratory mechanics, hemodynamics, and the distribution of ventilation and perfusion were assessed with electrical impedance tomography. The impact of FiO2 on the intrapulmonary shunt (delta shunt) was analyzed as the difference between the calculated shunt at FiO2 100% (shunt) and venous admixture at FiO2 40% (venous admixture). Results: Fourteen patients were studied. Decreasing PEEP from 15 to 10 cmH2O did not change shunt (24 [21-28] vs 27 [24-29]%) or venous admixture (18 [15-26] vs 23 [18-34]%) while partial pressure of arterial oxygen (FiO2 100%) was higher at PEEP 15 (262 [198-338] vs 256 [147-315] mmHg; P < .05). Instead when PEEP was decreased from 10 to 5 cmH2O, shunt increased to 36 [30-39]% (P < .05) and venous admixture increased to 33 [30-43]% (P < .05) and partial pressure of arterial oxygen (100%) decreased to 109 [76-177] mmHg (P < .05). At PEEP 15, administration of 100% FiO2 resulted in a shunt greater than venous admixture at 40% FiO2, ((24 [21-28] vs 18 [15-26]%, P = .005), delta shunt 5.5% (2.3-8.8)). Compared to PEEP 10, PEEP of 5 and 15 cmH2O resulted in decreased global and pixel-level compliance. Cardiac output at FiO2 100% resulted higher at PEEP 5 (5.4 [4.4-6.5]) compared to PEEP 10 (4.8 [4.1-5.5], P < .05) and PEEP 15 cmH2O (4.7 [4.5-5.4], P < .05). Conclusion: In this study, PEEP of 15 cmH2O, despite resulting in the highest oxygenation, was associated with overdistension. PEEP of 5 cmH2O was associated with increased shunt and alveolar collapse. Administration of 100% FiO2 was associated with an increase in intrapulmonary shunt in the setting of high PEEP. Trial registration: NCT05132933.

Numerical investigation of the effect of changing the geometry of a U-shaped fuel cell channel with asymmetric gas flow and its effect on hydrogen consumption

In this study, the simulation of a fuel cell is done to investigate how to reduce hydrogen loss in a fuel cell. Hydrogen and oxygen enter two channels in opposite directions. This study focuses on reducing hydrogen loss using H-shaped channels by changing the width of its vertical and horizontal parts at different voltages in the range of 0.05–0.8 V. Also, the values of cell power, electrolyte potential, mole fraction (MOF) of water and oxygen, and MOF of hydrogen are estimated. The finite element method (FEM) and COMSOL software are used for the simulations. The results demonstrate that the reduction of electrolyte potential by increasing the voltage from 0.1 to 0.8 V for the channel widths of 2–5 cm is 76.6 %, 83.3 %, 75.6 %, and 69.7 %, respectively. By enhancing the width of the channel from 2 to 5 cm at the voltages of 0.1 and 0.8 V, the MOF of hydrogen is decreased by 1.9 % and 4.8 %, respectively. When the width of channels changes from 2 to 5 cm, the amount of cell power is reduced by 54.3 %, 53.5 %, 52.4 %, and 52.6 %, respectively, by changing the voltage from 0.3 to 0.8 V. By increasing the voltage from 0.1 to 0.8 V, the MOF of hydrogen is decreased by 23.8 %, 24.4 %, 21.8 %, and 30.2 %, respectively, for the channel width of 2–5 cm.

Prediction model for in-hospital mortality in patients at high altitudes with ARDS due to COVID-19.

The diagnosis of acute respiratory distress syndrome (ARDS) includes the ratio of pressure arterial oxygen and inspired oxygen fraction (P/F) ≤ 300, which is often adjusted in locations more than 1,000 meters above sea level (masl) due to hypobaric hypoxemia. The main objective of this study was to develop a prediction model for in-hospital mortality among patients with ARDS due to coronavirus disease 2019 (COVID-19) (C-ARDS) at 2,600 masl with easily available variables at patient admission and to compare its discrimination capacity with a second model using the P/F adjusted for this high altitude. This study was an analysis of data from patients with C-ARDS treated between March 2020 and July 2021 in a university hospital located in the city of Bogotá, Colombia, at 2,600 masl. Demographic and laboratory data were extracted from electronic records. For the prediction model, univariate analyses were performed to screen variables with p <0.25. Then, these variables were automatically selected with a backward stepwise approach with a significance level of 0.1. The interaction terms and fractional polynomials were also examined in the final model. Multiple imputation procedures and bootstraps were used to obtain the coefficients with the best external validation. In addition, total adjustment of the model and logistic regression diagnostics were performed. The same methodology was used to develop a second model with the P/F adjusted for altitude. Finally, the areas under the curve (AUCs) of the receiver operating characteristic (ROC) curves of the two models were compared. A total of 2,210 subjects were included in the final analysis. The final model included 11 variables without interaction terms or nonlinear functions. The coefficients are presented excluding influential observations. The final equation for the model fit was g(x) = age(0.04819)+weight(0.00653)+height(-0.01856)+haemoglobin(-0.0916)+platelet count(-0.003614)+ creatinine(0.0958)+lactate dehydrogenase(0.001589)+sodium(-0.02298)+potassium(0.1574)+systolic pressure(-0.00308)+if moderate ARDS(0.628)+if severe ARDS(1.379), and the probability of in-hospital death was p (x) = e g (x)/(1+ e g (x)). The AUC of the ROC curve was 0.7601 (95% confidence interval (CI) 0.74-0, 78). The second model with the adjusted P/F presented an AUC of 0.754 (95% CI 0.73-0.77). No statistically significant difference was found between the AUC curves (p value = 0.6795). This study presents a prediction model for patients with C-ARDS at 2,600 masl with easily available admission variables for early stratification of in-hospital mortality risk. Adjusting the P/F for 2,600 masl did not improve the predictive capacity of the model. We do not recommend adjusting the P/F for altitude.

External Validation of a Multivariate Model for Targeted Surfactant Replacement

Introduction: Early targeted surfactant therapy for preterm infants is recommended but the best criteria to personalize treatment are unclear. We validate a previously published multivariate prognostic model based on gestational age (GA), lung ultrasound score (LUS), and oxygen saturation to inspire oxygen fraction ratio (SatO2/FiO2) using an independent data set. Methods: Pragmatic, observational study in 10 Italian and Spanish NICUs, including preterm babies (250 and 336 weeks divided into 3 GA intervals) with clinical signs of respiratory distress syndrome and stabilized on CPAP. LUS and SatO2/FiO2 were collected soon after stabilization. Their prognostic accuracy was evaluated on the subsequent surfactant administration by a rigorously masked physician. Results: One hundred seventy-five infants were included in the study. Surfactant was given to 74% infants born at 25–27 weeks, 38.5% at 28–30 weeks, and 26.5% at 31–33 weeks. The calibration curve comparing the validation and the development populations showed significant overlap with an intercept = 0.08, 95% CI (−0.34; 0.5) and a slope = 1.53, 95% CI (1.07–1.98). The validation cohort had a high predictive accuracy. Its ROC curve showed an AUC = 0.95, 95% CI (0.91–0.99) with sensitivity = 0.93, 95% CI (0.83–0.98), specificity = 0.81, 95% CI (0.73–0.88), PPV = 0.76, 95% CI (0.65–0.84), NPV = 0.95, 95% CI (0.88–0.98). LUS ≥9 demonstrated the highest sensitivity (0.91, 95% CI [0.82–0.97]) and specificity = 0.81, 95% CI (0.72–0.88) as individual predictor. LUS and SatO2/FiO2 prognostic performances varied with GA. Conclusion: We validated a prognostic model based on LUS and Sat/FiO2 to facilitate early, customized surfactant administration that may improve respiratory management of preterm neonates.

Intraoperative individualization of positive-end-expiratory pressure through electrical impedance tomography or esophageal pressure assessment: a systematic review and meta-analysis of randomized controlled trials.

This systematic review of randomized-controlled trials (RCTs) with meta-analyses aimed to compare the effects on intraoperative arterial oxygen tension to inspired oxygen fraction ratio (PaO2/FiO2), exerted by positive end-expiratory pressure (PEEP) individualized trough electrical impedance tomography (EIT) or esophageal pressure (Pes) assessment (intervention) vs. PEEP not tailored on EIT or Pes (control), in patients undergoing abdominal or pelvic surgery with an open or laparoscopic/robotic approach. PUBMED®, EMBASE®, and Cochrane Controlled Clinical trials register were searched for observational studies and RCTs from inception to the end of August 2022. Inclusion criteria were: RCTs comparing PEEP titrated on EIT/Pes assessment vs. PEEP not individualized on EIT/Pes and reporting intraoperative PaO2/FiO2. Two authors independently extracted data from the enrolled investigations. Data are reported as mean difference and 95% confidence interval (CI). Six RCTs were included for a total of 240 patients undergoing general anesthesia for surgery, of whom 117 subjects in the intervention group and 123 subjects in the control group. The intraoperative mean PaO2/FiO2 was 69.6 (95%CI 32.-106.4 ) mmHg higher in the intervention group as compared with the control group with 81.4% between-study heterogeneity (p < 0.01). However, at meta-regression, the between-study heterogeneity diminished to 44.96% when data were moderated for body mass index (estimate 3.45, 95%CI 0.78-6.11, p = 0.011). In patients undergoing abdominal or pelvic surgery with an open or laparoscopic/robotic approach, PEEP personalized by EIT or Pes allowed the achievement of a better intraoperative oxygenation compared to PEEP not individualized through EIT or Pes. CRD 42021218306, 30/01/2023.

Integrating SARS-CoV-2-specific interferon-γ release assay testing in the evaluation of patients hospitalized with COVID-19.

T cell-mediated immunity is crucial for protection against severe COVID-19. The performance of SARS-CoV-2-specific IFN-γ release assays (IGRAs) to measure T cell responses during severe acute infection is unknown. We conducted a prospective, longitudinal analysis of patients hospitalized for confirmed COVID-19. A standardized SARS-CoV-2-specific quantitative IGRA was measured on admission. Follow-up lasted 90 days. Two hundred forty-eight patients were included; 181 (73%) were vaccinated, 142 (57.3%) were infected with the Omicron variant, and 106 (42.7%) were infected with the Delta variant. The SARS-CoV-2-IGRA result was positive (>200 mIU/mL) in 125 (50.5%) patients, with 44 (35.2%) showing concomitant mitogen-induced IFN-γ response. Compared with patients with negative and borderline results, those with positive SARS-CoV-2 IGRA were younger and showed lower frequency of co-existing comorbidities, lower median Charlson comorbidity index, lower frequency of World Health Organization (WHO) severity score > 4, higher peripheral arterial oxygen saturation to inspired fraction of oxygen (SpO2/FiO2) ratio on admission, higher S-IgG and N-IgG antibody responses, and lower mortality at 28/60/90 days. These findings were consistent for both the Omicron and Delta variants. Similar patterns to those described above were observed in the subset of patients with positive SARS-CoV-2-IGRA and indeterminate mitogen-induced responses, as well as in those exhibiting both positive SARS-CoV-2-specific and mitogen responses. Twenty-eight (11.3%) patients had borderline (100-200 mIU/mL) SARS-CoV-2-IGRA results and shared several similarities with patients with negative SARS-CoV-2 IGRA. In an adjusted Cox model, a negative SARS-CoV-2-IGRA result was found to be an independent predictor of mortality. Using a receiver operating characteristics curve analysis, we found that an IFN-γ value of 150 mIU/mL was identified as the optimal cut-off point for predicting mortality, with 79% [95% confidence interval (CI) 61-93] sensitivity, 61% (95% CI 55-68) specificity, 18% (95% CI 15-22) positive predictive value, 96% (95% CI 93-98) negative predictive value, and an area under the curve (AUC) of 70%. The assay's performance remained consistent regardless of mitogen results or the presence of the Delta or Omicron variants. IMPORTANCE The cellular immune response is essential in the protection against severe disease in patients with established SARS-CoV-2 infection. The novelty of this study lies in the evaluation of the overall performance of a standardized assay to measure cellular immune response, the SARS-CoV-2-specific interferon-γ release assay (IGRA), in hospitalized patients with severe COVID-19. The SARS-CoV-2 IGRA was shown to accurately classify patients based on disease severity and prognosis, and the study revealed that test performance was not affected by the SARS-CoV-2 variant or control tube results. We identified an assay cut-off point with a high negative predictive value against mortality. The SARS-CoV-2 IGRA in patients hospitalized for COVID-19 may be a useful tool to assess cellular immunity and adopt targeted therapeutic and preventive measures.

On the Effects of Flow Swirl on Static Stability Limits and Flow/Flame Characteristics of Premixed Oxy-Methane Flames: An Experimental Study

ABSTRACT An experimental study was performed to investigate the effects of flow swirl on flow/flame characteristics and stability of atmospheric premixed oxy-methane (CH4/O2/CO2) flames. The flames generated by two swirlers of 55° and 45° swirl angles were tested on a test stand for a dry low emission (DLE) model gas turbine combustor at constant inlet flow velocity of 5.2 m/s and over ranges of operating oxygen fraction (OF: 21% to 70% - by volume in the O2/CO2 mixture) and equivalence ratio (: 0.2 to 1.0). Combustor static stability limits (flashback and blow-out) were determined experimentally in the -OF domain to identify the operational ranges of the combustor while varying inlet flow swirl. To understand the mechanisms for flashback and blow-out, the lines representing the stability limits were displayed in the -OF domain against the contours of combustor power density (PD: MW/m3/atm), adiabatic flame temperature (AFT), and inlet flow Reynolds (Re). Comparison of flame macrostructure and measurements of local flame temperatures were performed for the two swirlers over ranges of , OF, and AFT to determine the effects of such operational parameters on flow/flame interactions and flame stability and to serve as a database for validating numerical models for such flames. The results show that, for both swirlers, the flames blow-out at a very similar AFT of ~1600 K indicating the dominant role of AFT in controlling premixed oxy-flame stability near the blow-out limit. Compared to the same combustor with a 55° swirler, the 45° swirler has a wider stable combustion zone. Comparing the flames of the same AFT, at fixed inlet flow velocity, shows almost identical flame macrostructure whatever the operating inlet flow swirl, OF and φ.

Oxygen tri-clusters make glass highly crack-resistant

Identifying key structural factors that surmount their intrinsic brittleness and poor crack initiation resistance (CR) is crucial for designing glass efficiently and predictably. In this study, we present three significant discoveries that contribute to the design of glasses with superior mechanical performances. Firstly, the CR of the aluminosilicate glasses exhibited a drastic increase when the alumina content surpasses a critical threshold. Secondly, the fraction of three-coordinated oxygens (i.e., oxygen tri-cluster fraction [(3)O]) was successfully quantified using our new Nuclear Magnetic Resonance technique. Thirdly, a correlation between the evolution trend of the [(3)O] and the alumina content was established, which aligns closely with the CR trend. These findings suggest that oxygen tri-clusters play a crucial role in significantly enhancing CR in aluminosilicate glasses.

Performances and limits of Bag-Valve-Device for pre-oxygenation and manual ventilation: A comparative bench and cadaver study

IntroductionBag-Valve-Device (BVD) is the most frequently used device for pre-oxygenation and ventilation during cardiopulmonary resuscitation (CPR). A minimal expired fraction of oxygen (FeO2) above 0.85 is recommended during pre-oxygenation while insufflated volume (VTi) should be reduced during manual ventilation. The objective was to compare the performances of different BVD in simulated conditions. MethodsNine BVD were evaluated during pre-oxygenation: spontaneous breathing patients were simulated on a test lung (mild and severe conditions). FeO2 was measured with and without positive end-expiratory pressure (PEEP). CO2 rebreathing was evaluated. Then, manual ventilation was performed by 36 caregivers (n = 36) from three hospitals on a specific manikin; same procedure was repeated by 3 caregivers (n = 3) on two human cadavers with three of the nine BVD: In non-CPR scenario and during mechanical CPR with Interrupted Chest Compressions strategy (30:2). ResultsPre-oxygenation: FeO2 was lower than 0.85 for three BVD in severe condition and for two BVD in mild condition. FeO2 was higher than 0.85 in eight of nine BVD with an additional PEEP valve (PEEP 5 cmH2O). One BVD induced CO2 rebreathing.Manual ventilation: For non-CPR manual ventilation, mean VTi was within the predefined lung protective range (4–8 mL/kg PBW) for all BVD on the bench. For CPR manual ventilation, mean VTi was above the range for three BVD on the bench. Similar results were observed on cadavers. ConclusionsSeveral BVD did not reach the FeO2 required during pre-oxygenation. Manual ventilation was significantly less protective in three BVD. These observations are related to the different BVD working principles.

Numerical study on the ignition and combustion of a CH4 jet flame in diluted and undiluted coflows

This study numerically investigates the ignition and evolution of CH4 jet flames in a hot coflow (JHC) using large eddy simulation (LES). Three coflow oxygen fractions are carefully selected to compare moderate or intense low-oxygen dilution (MILD, YO2,C = 6 % and 9 %) and high temperature combustion (HTC, YO2,C = 23.3 %). Systematic investigations are performed on flame ignition, lift-off, reaction progress, and stabilization mechanisms. The results show that for the MILD cases, both the ignition process and final stable flame are controlled by turbulent mixing and chemistry in a state far from chemical equilibrium. In contrast, the reactions are much stronger for HTC, and the final flame is controlled by chemistry through equilibrium reactions. Moreover, for all three cases, the reactions always progress more rapidly at the lean side than at the rich side; thus, autoignition dominates the former, whereas flame propagation is more important for the latter. In addition, the premixing of fuel and oxidant prior to main reactions is crucial for realizing MILD combustion; therefore, the flame is lifted and stabilized by the autoignition of partially premixed reactants in the fuel-lean region. In contrast, the final HTC flame attaches to the burner exit and is stabilized by both the lean-side autoignition and rich-side flame propagation. For all three cases, the lean-side and stoichiometric flames adopt the nonpremixed mode, whereas the rich-side reactions are in the premixed mode, except for the flame base.

Individualized PEEP without Recruitment Maneuvers Improves Intraoperative Oxygenation: A Randomized Controlled Study.

Individualized positive end-expiratory pressure (PEEP) combined with recruitment maneuvers improves intraoperative oxygenation in individuals undergoing robot-assisted prostatectomy. However, whether electrical impedance tomography (EIT)-guided individualized PEEP without recruitment maneuvers can also improve intraoperative oxygenation is unknown. To test this, fifty-six male patients undergoing elective robot-assisted laparoscopic prostatectomy were randomly assigned to either individualized PEEP (Group PEEPIND, n = 28) or a control with a fixed PEEP of 5 cm H2O (Group PEEP5, n = 28). Individualized PEEP was guided by EIT after placing the patients in the Trendelenburg position and performing intraperitoneal insufflation. Patients in Group PEEPIND maintained individualized PEEP without intermittent recruitment maneuvers, and those in Group PEEP5 maintained a PEEP of 5 cm H2O intraoperatively. Both groups were extubated in a semi-sitting position once the extubation criteria were met. The primary outcome was arterial oxygen partial pressure (PaO2)/inspiratory oxygen fraction (FiO2) prior to extubation. Other outcomes included intraoperative driving pressure, plateau pressure and dynamic, respiratory system compliance, and the incidence of postoperative hypoxemia in the post-operative care unit (PACU). Our results showed that the intraoperative median for PEEPIND was 16 cm H2O (ranging from 12 to 18 cm H2O). EIT-guided PEEPIND was associated with higher PaO2/FiO2 before extubation compared to PEEP5 (71.6 ± 10.7 vs. 56.8 ± 14.1 kPa, p = 0.003). Improved oxygenation extended into the PACU with a lower incidence of postoperative hypoxemia (3.8% vs. 26.9%, p = 0.021). Additionally, PEEPIND was associated with lower driving pressures (12.0 ± 3.0 vs. 15.0 ± 4.4 cm H2O, p = 0.044) and better compliance (44.5 ± 12.8 vs. 33.6 ± 9.1 mL/cm H2O, p = 0.017). Our data indicated that individualized PEEP guided by EIT without intraoperative recruitment maneuvers also improved perioperative oxygenation in patients undergoing robot-assisted laparoscopic radical prostatectomy, which could benefit patients with the risk of intraoperative hemodynamic instability caused by recruitment maneuvers. Trial registration: China Clinical Trial Registration Center Identifier: ChiCTR2100053839. This study was registered on 1 December 2021. The first patient was recruited on 15 December 2021.

Unusual severe hypoxemia due to unilateral pulmonary edema after conventional cardiopulmonary bypass salvaged by veno-venous extracorporeal membrane oxygenation: a case report

BackgroundWe report a case in which veno-venous extracorporeal membrane oxygenation (V-V ECMO) saved the life of a patient who developed severe hypoxemia due to unusual unilateral pulmonary edema (UPE) after cardiopulmonary bypass (CPB).Case presentationA 69-year-old man underwent aortic valve replacement and coronary artery bypass grafting. Following uneventful weaning off CPB, he developed severe hypoxemia. The ratio of arterial oxygen tension to inspired oxygen fraction (PaO2/FiO2) decreased from 301 mmHg 5 min after CPB to 42 mmHg 90 min after CPB. A chest X-ray revealed right-sided UPE. Immediately established V-V ECMO increased PaO2/FiO2 to 170 mmHg. Re-expansion pulmonary edema (REPE) was likely, as the right lung remained collapsed during CPB following the accidental opening of the right chest cavity during graft harvesting.ConclusionsV-V ECMO was effective in improving oxygenation and saving the life of a patient who had fallen into unilateral REPE unusually developing after conventional CPB.

Acute chemical pulmonary edema with inhaled nitrogen dioxide intoxication

Nitrogen dioxide is released by the interaction of some metals with nitric acid. Inhalation intoxication with nitrogen dioxide leads to chemical pulmonary edema. This study presents the case of a patient who had acute inhalation exposure to an unidentified brown gaseous substance (presumably nitrogen dioxide) when he etched a metal product with nitric acid. Twenty-four hours after contact with the gas, he manifested signs of intoxication, such as chest pain, tachypnea, and decreased saturation. Laboratory tests revealed hemoconcentration, hyperfermentemia, and arterial hypoxemia. The X-ray image of the entire lung surface revealed a sharp increase and deformation of the pulmonary pattern due to the vascular component. The diagnosis was T65, i.e., toxic effect of other and unspecified substances. With treatment, the patients condition improved. On day 4 after therapeutic exposure, with decreased oxygen fraction in the inhaled gas mixture to 0.3, the saturation increased to 98%, and tachypnea disappeared. On day 6, with ongoing treatment (oxygen therapy, use of antioxidants, antihypoxants, anti-inflammatory, and antibacterial drugs), the inflammatory reaction stopped, the rheological properties of the blood improved, and the gas composition of arterial blood normalized, i.e., the oxygenation index was 436, which indicated the disappearance of arterial blood oxygenation disorders. During the radiological examination, the normal radiological picture of the lungs was determined. Thus, on day 6 after the start of therapy, signs of intoxication were completely stopped. Specific changes in the lungs during radiation research techniques, hemoconcentration, inflammation, and hypoxemia during laboratory blood tests should be considered prognostic signs of chemical pulmonary edema. As a pathogenetic therapy, treatment must be supplemented with drugs that stop the cascade of free radical oxidation reactions (acetylcysteine and sodium thiosulfate). Individuals exposed to nitrogen dioxide should be considered a high-risk group for lung damage and hospitalized for dynamic observation for at least 2 days. Taking into account the genotoxic effects of nitrogen dioxide, affected patients should be classified as at risk of developing neoplasms and undergo further dynamic monitoring.

ROX index to predict failure with low flow devices in COVID-19

The ROX index (iROX) obtained from pulse oximetry saturation/inspired fraction of oxygen and respiratory rate, predicts success with high-flow nasal cannula (HFNC), however its performance for low-flow oxygenation devices (DOBF) is unknown. To determine suitability of iROX at 12 hours as a predictor of mechanical ventilation (VMI) in hospitalized patients with severe COVID-19 and DOBF. An historical cohort was performed. Adults with COVID-19, hospitalized, with supplemental oxygen supply are included, excluding patients with pathologies in chronic stages that could alter the results, calculating the iROX at 12 hours, obtaining the cut-off point using a ROC curve and Youden index, the risk of VMI is prolonged using relative risk (RR), with 95% confidence intervals (95%CI). Confounding variables were evaluated to determine the performance of the iROX. The dependent variable mechanical ventilation recorded as reported in the file and the independent iROX obtained in the same way as the previous one. 63 patients with a median age of 62 years were included. The best iROX cut-off point at 12 hours was 5.35. With this cut-off point, VMI was associated with a RR of 8.75 (95% CI 2.36-32.35). In the multivariate model with an OR of 9.26; (95% CI, 2.39 - 35.78), after initiation of DOBF was consistently associated with an increased risk of intubation. In hospitalized patients with severe COVID-19, an iROX < 5.35 at 12 hours appears to be a predictor for the onset of VMI.

Saturation index and fraction of inspired oxygen as a predictor in COVID-19

Coronavirus disease leads to silent hypoxia, ARDS, and organ failure. The saturation and fraction of inspired oxygen have been related to the degree of lung damage, can be considered as a monitoring tool for lung function during hospitalization and a predictor of mortality in patients with pneumonia by COVID-19. To evaluate the usefulness of the oxygen saturation index and fraction of inspired oxygen as a predictor of mortality in patients with COVID-19 pneumonia. A retrospective, longitudinal, analytical study. Files of eligible patients with a diagnosis of SARS-CoV-2 pneumonia were admitted to HGR No.2, complete file, recording of oxygen saturation and inspired fraction of oxygen, were included. Patients dependent on supplemental oxygen, who did not require supplemental oxygen during their hospitalization, incomplete records, patients who have died from non-pulmonary causes, were excluded. A sample of 175 files with a diagnosis of pneumonia with SARS-CoV-2 was obtained. A logistic regression model was performed including age over 60 years BE of 2.68, with CI (1.09-6.5), DM2 with a BE of 2.35 with CI (0.99-5.59), HTA with a BE of 0.80, with CI (0.32-2.02), SAFI index less than 310 with a BE of 6.63, with a CI (2.64-16.65), endotracheal intubation with a BE 48.43, and a CI (2.64-16.65). The SpO2/Fio2 index can be used for continuous monitoring of lung function in patients with COVID-19 pneumonia, in an accessible, easy and economical way. A relationship with mortality was obtained in patients with SpO2/FiO2 less than 310 associated with other factors.

Clinical Parameters in the First 5 Minutes after Birth Have a Predictive Value for Survival of Extremely Preterm Infants

Abstract Extreme preterm infants (&lt;28 weeks' gestation) often require positive pressure ventilation with oxygen during postnatal stabilization in the delivery room. To date, optimal inspired fraction of oxygen (FiO2) still represents a conundrum in newborn care oscillating between higher (&gt;60%) and lower (&lt;30%) initial FiO2. Recent evidence and meta-analyses have underscored the predictive value for survival and/or relevant clinical outcomes of the Apgar score and the achievement of arterial oxygen saturation measured by pulse oximetry ≥85% at 5 minutes after birth. New clinical trials comparing higher versus lower initial FiO2 have been launched aiming to optimize postnatal stabilization of extreme preterm while avoiding adverse effects of hypoxemia or hyperoxemia.