FiO2 Research Articles

Sleep loss effects on physiological and cognitive responses to systemic environmental hypoxia.

In the course of their missions or training, alpinists, but also mountain combat forces and mountain security services, professional miners, aircrew, aircraft and glider pilots and helicopter crews are regularly exposed to altitude without oxygen supplementation. At altitude, humans are exposed to systemic environmental hypoxia induced by the decrease in barometric pressure (<1,013hPa) which decreases the inspired partial pressure of oxygen (PIO2), while the oxygen fraction is constant (equal to approximately 20.9%). Effects of altitude on humans occur gradually and depend on the duration of exposure and the altitude level. From 1,500m altitude (response threshold), several adaptive responses offset the effects of hypoxia, involving the respiratory and the cardiovascular systems, and the oxygen transport capacity of the blood. Fatigue and cognitive and sensory disorders are usually observed from 2,500m (threshold of prolonged hypoxia). Above 3,500m (the threshold for disorders), the effects are not completely compensated and maladaptive responses occur and individuals develop altitude headache or acute altitude illness [Acute Mountain Sickness (AMS)]. The magnitude of effects varies considerably between different physiological systems and exhibits significant inter-individual variability. In addition to comorbidities, the factors of vulnerability are still little known. They can be constitutive (genetic) or circumstantial (sleep deprivation, fatigue, speed of ascent.). In particular, sleep loss, a condition that is often encountered in real-life settings, could have an impact on the physiological and cognitive responses to hypoxia. In this review, we report the current state of knowledge on the impact of sleep loss on responses to environmental hypoxia in humans, with the aim of identifying possible consequences for AMS risk and cognition, as well as the value of behavioral and non-pharmacological countermeasures.

Variability in low-flow oxygen delivery by nasal cannula evaluated in neonatal and infant airway replicas

BackgroundThe nasal cannula is considered a trusted and effective means of administering low-flow oxygen and is widely used for neonates and infants requiring oxygen therapy, despite an understanding that oxygen concentrations delivered to patients are variable.MethodsIn the present study, realistic nasal airway replicas derived from medical scans of children less than 3 months old were used to measure the fraction of oxygen inhaled (FiO2) through nasal cannulas during low-flow oxygen delivery. Parameters influencing variability in FiO2 were evaluated, as was the hypothesis that measured FiO2 values could be predicted using a simple, flow-weighted calculation that assumes ideal mixing of oxygen with entrained room air. Tidal breathing through neonatal and infant nasal airway replicas was controlled using a lung simulator. Parameters for nasal cannula oxygen flow rate, nasal airway geometry, tidal volume, respiratory rate, inhalation/exhalation, or I:E ratio (ti/te), breath waveform, and cannula prong insertion position were varied to determine their effect on measured FiO2. In total, FiO2 was measured for 384 different parameter combinations, with each combination repeated in triplicate. Analysis of variance (ANOVA) was used to assess the influence of parameters on measured FiO2.ResultsMeasured FiO2 was not appreciably affected by the breath waveform shape, the replica geometry, or the cannula position but was significantly influenced by the tidal volume, the inhalation time, and the nasal cannula flow rate.ConclusionsThe flow-weighted calculation overpredicted FiO2 for measured values above 60%, but an empirical correction to the calculation provided good agreement with measured FiO2 across the full range of experimental data.

Initial oxygenation as early predictor of mortality in acute respiratory distress syndrome: a retrospective study

Introduction: Acute respiratory distress syndrome (ARDS) is a major contributor to mortality and morbidity of adult patients admitted to intensive care units (ICU). Numerous scoring systems have been developed for critically ill patients with the goal of more accurately predicting clinical outcomes. However, the variability in these scores among individual patients, and consequently, their individual predictive ability is quite limited. Aim: To evaluate the role of initial oxygenation as an early predictor of mortality in ARDS patients. Methodology: One hundred and six mechanically ventilated adult patients with ARDS were enrolled retrospectively. Baseline parameters from the day of ICU admission were recorded. The details of ventilation, inspired oxygen fraction required, positive end-expiratory pressure and number of days on ventilation along with duration of hospital stay were recorded. Similarly, the status of oxygenation was assessed using PaO2/FiO2 (P/F) ratio. Survival of the patients was correlated with the baseline status of oxygenation. Results: Of the 106 patients, 65 were males and 41 female. The mean (± SD) age was 44 years (16.08). The difference in the P/F ratio between survivors and nonsurvivors was statistically significant. The ROC curve showed a cutoff value for P/F ratio of 108. Among survivors, the ICU stay was shorter in patients in pulmonary group compared to extrapulmonary group. Conclusion: Mortality is high if the baseline P/F ratio at admission is below 108. There is no difference in mortality due to lung injury caused by pulmonary or extrapulmonary aetiologies. ICU stay is longer among survivors if cause of ARDS is extrapulmonary.

Studies on the valveless scheme to produce high-frequency detonations with different purge methods

Producing high-frequency detonations is an important topic for pulse detonations which has received considerable attentions. The valveless scheme has been verified to be able to obtain high-frequency detonations more than 100 Hz. This work has been conducted to investigate the possibility to achieve a higher detonation frequency and clarify the limits of stable operations preliminarily for the valveless scheme with different purge methods. Oxygen, ethylene, and nitrogen or liquid water are utilized as oxidizer, fuel, and purge medium in the experiments while two injection configurations are employed. The maximum detonation frequencies of 180 Hz and 330 Hz have been achieved in stable operations for two different injection configurations when nitrogen is used as the purge gas. The ceiling frequency for stable detonations is 300 Hz if nitrogen is replaced by liquid water, which indicates that water vapor is capable to create an efficient buffer zone to ensure stable operations. The results imply that the injection configuration also has a great impact on the ceiling stable detonation frequency. Three operating modes have been observed in this study, i.e., a stable detonation mode, an unstable detonation mode, and a deflagration mode. In the unstable mode, failure of detonation initiation occurs frequently and one interesting phenomenon is that the detonation frequency is reduced by half exactly when insufficient filling happens. The supply pressure ratios of oxidizer to fuel and purge to fuel are obtained for different operating modes when the purge method is changed. Furthermore, the equivalence ratios have been also studied for different operating modes which reveals that the range will change when different purge methods and injection configurations are employed. According to the equivalence ratio and the mass flow rates, an equivalent volume fraction of oxygen is defined and its range for the stable detonation mode is clarified.

Graded oxygen delivery using low flow rotameter during positive pressure ventilation using self-inflating bag with a leak - an experimental study

Introduction: Bag-mask ventilation does not always guarantee 100% seal around airway opening and hence delivered fraction of oxygen (FDO2) may vary. Aim: To determine the FDO2 via a standard neonatal selfinflating bag with and without application of leak, without a reservoir bag with flow rates of 0.1, 0.2, 0.4, 0.6, 0.8, 1, 2, 4 and 6 L/min. Method: A test lung with a three way rotator to produce 0%, 30%, 50% and 75% leak was connected to a 3.5 mm ID endotracheal tube (ETT) connected to a VBM standard preterm self-inflating bag of 250 mL without a reservoir. The ETT was connected to ENVENTEC oxygen analyser and the bag inlet to a 100% oxygen source. Ventilation was done to a peak pressure of 15-20 cm H2O, at 40 bpm. FDO2 was recorded every 30 s, until the difference between two consecutive values was ≤1%. Result: The change in FDO2 was maximum when compared between 0.1 L/min and 6 L/min. For all leak percentages, the delivered oxygen showed an increasing trend from 0.1 to 0.6 L/min, a plateau from 0.6 to 1 L/min after which it increased. The change in FDO2 was different for different flow rates among various leak percentages. The highest delivered oxygen without leak was 56.15 ± 3.45% with 4 L/min flow. The oxygen delivered with 70% leak was considerably lower when compared to values with different leaks with respective flow rates. Conclusion: FDO2 increases with oxygen flow rates greater than 1 L/min. Leak around the mask has no effect of FDO2. Equilibration of FDO2 is achieved with in 60-90 s.

Coronary Artery Air Embolism in the Non-operating room Anesthesia Setting.

Coronary artery air embolism is a rare complication in the non–operating room anesthesia environment. In this setting, coronary artery air embolism is generally caused by communication between the atmosphere and the pulmonary venous system or by the creation of a bronchial-venous or alveolar-venous fistula during lung biopsy.1 Typical presentation is a result of the ensuing myocardial ischemia, and includes chest pain, arrhythmia, ST segment changes, bradycardia, hypotension, and cardiovascular collapse.2Figure 1 represents the intraprocedural computed tomography imaging of a 74-year-old woman who underwent percutaneous lung biopsy. Clearly visible is the air-fluid level in the ascending aorta, just distal to the right coronary artery ostia. Figure 2 shows air in the proximal right coronary artery. This patient’s procedural course was complicated by profound bradycardia, arrhythmia, and cardiogenic shock secondary to acute myocardial ischemia.Risk of coronary artery air embolism is underappreciated outside the cardiac operating room; thus, the anesthesiologist must maintain a high degree of suspicion and closely monitor the electrocardiogram for change. Risk factors include coughing, positive pressure ventilation, biopsy of cavitary lesions, and use of needle-within-needle biopsy systems.3 In supine patients, the right ventricle is particularly vulnerable to coronary artery air embolism secondary to the anterior takeoff of the right coronary. Treatment involves immediate Trendelenburg positioning to prevent cerebral air embolism, an inspiratory oxygen fraction of 1.0, central access, and catecholamine support of cardiac function and coronary perfusion pressure. Transcutaneous or transvenous pacing, as well as coronary angiography, aspiration, and localized vasodilator injection have also been trialed successfully in the catheterization laboratory.3 Finally, extracorporeal membrane oxygenation or cardiac bypass may be indicated if other measures fail.Support was provided solely from institutional and/or departmental sources.The authors declare no competing interests.

High-flow nasal oxygen in acute hypoxemic respiratory failure: A narrative review of the evidence before and after the COVID-19 pandemic.

High-flow nasal oxygen (HFNO) is a type of non-invasive advanced respiratory support that allows the delivery of high-flow and humidified air through a nasal cannula. It can deliver a higher inspired oxygen fraction than conventional oxygen therapy (COT), improves secretion clearance, has a small positive end-expiratory pressure, and exhibits a washout effect on the upper air space that diminishes dead space ventilation. HFNO has been shown to reduce the work of breathing in acute hypoxemic respiratory failure (AHRF) and has become an interesting option for non-invasive respiratory support. Evidence published before the COVID-19 pandemic suggested a possible reduction of the need for invasive mechanical ventilation compared to COT. The COVID-19 pandemic has resulted in a substantial increase in AHRF worldwide, overwhelming both acute and intensive care unit capacity in most countries. This triggered new trials, adding to the body of evidence on HFNO in AHRF and its possible benefits compared to COT or non-invasive ventilation. We have summarized and discussed this recent evidence to inform the best supportive strategy in AHRF both related and unrelated to COVID-19.

Quantification of changes in lung aeration associated with physiotherapy using lung ultrasound in mechanically ventilated patients: a prospective cohort study

BackgroundLung ultrasound (LUS) is a novel and emerging tool for physiotherapists in ICU and may provide a way of monitoring lung aeration change in response to respiratory physiotherapy treatment during a patient’s ICU stay. ObjectiveTo measure change in the LUS score associated with a respiratory physiotherapy treatment; to determine whether change in LUS score correlates with other physiological measures. Design and settingA single-centre prospective cohort study was undertaken in a tertiary teaching hospital in Sydney, Australia. PatientsAdult mechanically ventilated patients in ICU with suspicion of atelectasis. MeasurementsPrimary outcome: pre-post difference in LUS score. Secondary outcomes: PaO2/FiO2 (PF) ratio, tidal volume (VT), lung auscultation score, driving pressure (DP) and the modified radiological atelectasis score (mRAS) on CXR. Results43 patients were included. There was a mean improvement in total LUS score after physiotherapy treatment of − 2.9 (95%CI −4.4, −1.4), and a mean improvement in LUS of the right and left lungs of − 1.6 (−2.5, −0.7) and − 1.3 (−2.5, −0.1) respectively. There was a mean improvement in PF ratio, VT and auscultation score of 10.4 (−11.89, 32.7), 19 (−7.4, 44.5) and − 1.8 (−2.6, −1.0) respectively. There was no improvement in mRAS or DP. There was a weak correlation between change in LUS score compared with change in mRAS score. LimitationsLimitations included the prospective cohort single site design and the small sample size. ConclusionsThe LUS score can be used to detect changes in lung aeration associated with respiratory physiotherapy treatment for acute lobar atelectasis in mechanically ventilated patients.Australian and New Zealand Clinical Trials Registry Number: ACTRN12619000783123. Contribution of the Paper•Assessment and measurement tools currently used by physiotherapists lack diagnostic accuracy. Lung ultrasound has high diagnostic accuracy in detecting pathologies pertinent to physiotherapists and may be helpful in monitoring treatment response.•The lung ultrasound score detects changes in lung aeration associated with respiratory physiotherapy treatment.•This study highlights lung ultrasound as a potential new tool for lung monitoring for physiotherapists in ICU.

Interleukin 18 and IL-18 BP response to Sars-CoV-2 virus infection.

The immune response to the SARS-CoV-2 infection is crucial to the patient outcome. IL-18 is involved in the lymphocyte response to the disease and it is well established its important role in the complex developing of the host response to viral infection. This study aims at the analysis of the concentrations of IL-18, IL-18BP, INF-γ at the onset of the SARS-CoV-2 infection. The serum levels of measured interleukins were obtained through enzyme-linked immunosorbent assay. Furthermore, the free fraction of IL-18 was numerically evaluated. The enrolled patients were divided in two severity groups according to a threshold value of 300 for the ratio of arterial partial pressure of oxygen and fraction of inspired oxygen fraction and according to the parenchymal involvement as evaluated by computerized tomography at the admittance. In the group of patients with a more severe disease, a significant increase of the IL-18, INF-γ and IL-18BP levels have been observed, whereas the free IL-18 component values were almost constant. The results confirm that, at the onset of the disease, the host response keep the inflammatory cytokines in an equilibrium and support the hypothesis to adopt the IL-18BP modulation as a possible and effective therapeutic approach.

Intranasal Midazolam Premedication for Digital Image-Assisted Fundus Examination in Preterm Neonates.

We aimed to evaluate the feasibility and tolerability of fundus examination in preterm newborns after implementing a premedication with intranasal midazolam as a quality improvement project in a neonatal intensive care unit (NICU). Prospective examination of all fundus examinations between January and June 2022, before 0 (T0) and after 1 (T1), 15 (T15), and 60 (T60) minutes from intranasal midazolam administration. The EDIN (Echelle de Douleur et Incomfort du Nouveau-né [newborn pain and discomfort score-in French]) pain score was calculated and various physiologic parameters were recorded. Data were analyzed with repeated measures ANOVA (analysis of variance). A total of 36 fundus examinations were performed in 27 noninvasively ventilated patients. The mean EDIN score went from 0.8 ± 1 at T0 to 0.72 ± 1.05 at T1, then to 0.22 ± 0.59 at T15, and to 0 ± 0 at T60 (p < 0.001). Thus, it remained below the threshold of 5, which is associated with significant pain. The mean heart rate decreased from 164 ± 16 at T0, to 161 ± 16 at T1, then to 154 ± 14 at T15, and to 153 ± 12 at T60 (p < 0.001). There was no significant change in the oxygen saturation/inspired oxygen fraction ratio across the four time points (p = 0.202) and the mean arterial pressure was similar before and after the administration of midazolam (60 ± 10 vs. 59 ± 10, p = 0.571). Intranasal midazolam provides good comfort and normal physiological parameters; therefore, the implementation of a NICU protocol to improve quality of retinal examinations seems feasible and well tolerated. · Fundus examinations did not cause pain after premedication with intranasal midazolam.. · No respiratory or circulatory adverse effect was reported.. · Implementing such a premedication protocol in the NICU seems feasible, helpful, and well tolerated..

Practice of oxygen use in anesthesiology – a survey of the European Society of Anaesthesiology and Intensive Care

BackgroundOxygen is one of the most commonly used drugs by anesthesiologists. The World Health Organization (WHO) gave recommendations regarding perioperative oxygen administration, but the practice of oxygen use in anesthesia, critical emergency, and intensive care medicine remains unclear.MethodsWe conducted an online survey among members of the European Society of Anaesthesiology and Intensive Care (ESAIC). The questionnaire consisted of 46 queries appraising the perioperative period, emergency medicine and in the intensive care, knowledge about current recommendations by the WHO, oxygen toxicity, and devices for supplemental oxygen therapy.ResultsSeven hundred ninety-eight ESAIC members (2.1% of all ESAIC members) completed the survey. Most respondents were board-certified and worked in hospitals with > 500 beds. The majority affirmed that they do not use specific protocols for oxygen administration. WHO recommendations are unknown to 42% of respondents, known but not followed by 14%, and known and followed by 24% of them. Respondents prefer inspiratory oxygen fraction (FiO2) ≥80% during induction and emergence from anesthesia, but intraoperatively < 60% for maintenance, and higher FiO2 in patients with diseased than non-diseased lungs. Postoperative oxygen therapy is prescribed more commonly according to peripheral oxygen saturation (SpO2), but shortage of devices still limits monitoring. When monitoring is used, SpO2 ≤ 95% is often targeted. In critical emergency medicine, oxygen is used frequently in patients aged ≥80 years, or presenting with respiratory distress, chronic obstructive pulmonary disease, myocardial infarction, and stroke. In the intensive care unit, oxygen is mostly targeted at 96%, especially in patients with pulmonary diseases.ConclusionsThe current practice of perioperative oxygen therapy among respondents does not follow WHO recommendations or current evidence, and access to postoperative monitoring devices impairs the individualization of oxygen therapy. Further research and additional teaching about use of oxygen are necessary.

Numerical analyses on oxygen transport resistances in polymer electrolyte membrane fuel cells using a novel agglomerate model

Characterizing oxygen transport resistances in different components of a polymer electrolyte membrane fuel cell (PEMFC) is essential to achieve better cell performance at high current under low Pt loading. In this work, a macroscopic three-dimensional model, together with a novel agglomerate model was proposed to analyze impacts of operating conditions on these resistances via limiting current strategy. By introducing a focusing factor obtained with lattice Boltzmann method at mesoscopic level, the structure-dependent local transport resistance in ionomer thin-film of the electrode was comprehensively captured and validated by existing experimental studies. Contributions of the cell components to the total transport resistance were dissected. Results show that the present agglomerate model could well reproduce the local transport behaviors of oxygen in catalyst layer by fully considering the detailed nanoscale diffusion and adsorption processes. A small mass fraction of oxygen was favored to minimize the relative deviation of the local transport resistance from its intrinsic one due to the water production and heat generation, which can reach 7% for the mass fraction of oxygen of 1%. Contribution of the in-plane diffusion of oxygen in the inactive electrode is around 1%. The total transport resistance increased with the absolute pressure, mainly due to the dominated molecular diffusion mechanism in gas channel and gas diffusion layer. Gas convection accounted for 26% of the oxygen transport resistance originated from gas channel. The transport resistance of catalyst layer increased significantly with the reduction of Pt loading, and decreased with relative humidity and operating temperature, particularly at high Pt loading.

N-Acetylcysteine and Postoperative Atrial Fibrillation: Comment.

We read with interest the recent work of Amar et al.,1 with the editorial by Karamnov and Muehischlegel2 which demonstrated the feasibility and safety of an antioxidant, N-acetylcysteine, for the prevention of atrial fibrillation after thoracic surgery. We agree with Karamnov and Muehischlegel2 that an anti-inflammatory approach using antioxidants reduces NADPH oxidase activity for postoperative atrial fibrillation, a plausible strategy for prophylaxis.2 However, we have additional potential explanations for why there was no significant difference in the occurrence of postoperative atrial fibrillation in patients who did and did not receive perioperative N-acetylcysteine in the study of Amar et al.1N-Acetylcysteine is an l-cysteine prodrug and glutathione precursor that, via l-cysteine conversion, helps scavenge oxygen-derived free radicals and binds metal ions into complexes, resulting in oxidative stress reduction.3 However, as we showed in a previous study, which was done in rats and focused on the mesenteric artery, l-cysteine induces an oxygen-derived free radical, superoxide production mediated by NADPH oxidase in a high 95% oxygen condition.4 In contrast, it does not cause redox derangement in a 50% oxygen mixture.4 Therefore, the high oxygen exposure under one-lung ventilation during major thoracic surgery seems to cancel l-cysteine’s beneficial role as a radical scavenger and to add oxidative stress. Nevertheless, we do not see any information regarding the inspiratory oxygen fraction in the work of Amar et al.,1 and thus, N-acetylcysteine combined with a high oxygen condition during thoracic surgery may contribute to the results shown by Amar et al.1 Also, previous studies indicated that a membrane-bound NADPH oxidase is the primary source of oxidative stress in human atrial fibrillation,5 while inflammation (or cytokines) activates several subtypes of NADPH oxidase.6 However, there are no clinically specific inhibitors of membrane-bound NADPH oxidase.Support was provided solely from institutional and/or departmental sources.The authors declare no competing interests.

Analysis of Highly CO2-Diluted Oxy-propane Flames Stabilized over a Multihole Burner of a Model Gas Turbine Combustor.

Premixed oxy-propane flames are investigated numerically in a multihole model gas turbine combustor at various inlet mixture compositions over a range of equivalence ratios (Ø: 0.241-0.500), oxygen fractions (OF: 32.4-60.0%), and adiabatic flame temperatures (T ad: 1600-1900 K) at a constant bulk throat velocity of 5.2 m/s. The flames in multihole combustors are highly influenced by their corresponding adiabatic flame temperatures. Similar flame shapes are observed at constant T ad, where cases with (Ø = 0.241, OF = 60%) and (Ø = 0.50, OF = 32.4%) both represent lifted flames at T ad = 1600 K, anchored flames in (Ø = 0.276, OF = 60%) and (Ø = 0.50, OF = 36.6%) at T ad = 1750 K, and anchored stronger flames in cases (Ø = 0.313, OF = 60%), (Ø = 0.392, OF = 50%), and (Ø = 0.50, OF = 40.8%) at T ad = 1900 K. Flames in a multihole combustor are characterized by the presence of an outer recirculation zone (ORZ) only. In comparison with a swirl-stabilized combustor in identical inlet conditions, flames in a multihole combustor demonstrate a lower Damköhler number (Da), higher flame thickness, elevated pattern factor, and increased CO emission. Due to the reduced vorticity level because of the absence of swirl motion, the multihole flames have higher axial temperature than the swirl-stabilized ones.

A physically motivated “charge-exchange method” for measuring electron temperatures within H ii regions

Aims. Temperature uncertainties plague our understanding of abundance variations within the interstellar medium. Using the PHANGS-MUSE large program, we develop and apply a new technique to model the strong emission lines arising from H ii regions in 19 nearby spiral galaxies at ~50 pc resolution and infer electron temperatures for the nebulae. Methods. Due to the charge-exchange coupling of the ionization fraction of the atomic oxygen to that of hydrogen, the emissivity of the observed [O i]λ6300/Hα line ratio can be modeled as a function of the gas phase oxygen abundance (O/H), ionization fraction (fion), and electron temperature (Te). We measure O/H using a strong-line metallicity calibration and identify a correlation between fion and [S iii]λ9069/[S ii]λ6716,6730, tracing ionization parameter variations. Results. We solve for Te and test the method by reproducing direct measurements of Te([N ii]λ5755) based on auroral line detections to within ~600 K. We apply this“charge-exchange method” of calculating Te to 4129 H ii regions across 19 PHANGS-MUSE galaxies. We uncover radial temperature gradients, increased homogeneity on small scales, and azimuthal temperature variations in the disks that correspond to established abundance patterns. This new technique for measuring electron temperatures leverages the growing availability of optical integral field unit spectroscopic maps across galaxy samples, increasing the statistics available compared to direct auroral line detections.

Effect of Lower vs Higher Oxygen Saturation Targets on Survival to Hospital Discharge Among Patients Resuscitated After Out-of-Hospital Cardiac Arrest

The administration of a high fraction of oxygen following return of spontaneous circulation in out-of-hospital cardiac arrest may increase reperfusion brain injury. To determine whether targeting a lower oxygen saturation in the early phase of postresuscitation care for out-of-hospital cardiac arrest improves survival at hospital discharge. This multicenter, parallel-group, randomized clinical trial included unconscious adults with return of spontaneous circulation and a peripheral oxygen saturation (Spo2) of at least 95% while receiving 100% oxygen. The trial was conducted in 2 emergency medical services and 15 hospitals in Victoria and South Australia, Australia, between December 11, 2017, and August 11, 2020, with data collection from ambulance and hospital medical records (final follow-up date, August 25, 2021). The trial enrolled 428 of a planned 1416 patients. Patients were randomized by paramedics to receive oxygen titration to achieve an oxygen saturation of either 90% to 94% (intervention; n = 216) or 98% to 100% (standard care; n = 212) until arrival in the intensive care unit. The primary outcome was survival to hospital discharge. There were 9 secondary outcomes collected, including hypoxic episodes (Spo2 &lt;90%) and prespecified serious adverse events, which included hypoxia with rearrest. The trial was stopped early due to the COVID-19 pandemic. Of the 428 patients who were randomized, 425 were included in the primary analysis (median age, 65.5 years; 100 [23.5%] women) and all completed the trial. Overall, 82 of 214 patients (38.3%) in the intervention group survived to hospital discharge compared with 101 of 211 (47.9%) in the standard care group (difference, -9.6% [95% CI, -18.9% to -0.2%]; unadjusted odds ratio, 0.68 [95% CI, 0.46-1.00]; P = .05). Of the 9 prespecified secondary outcomes collected during hospital stay, 8 showed no significant difference. A hypoxic episode prior to intensive care was observed in 31.3% (n = 67) of participants in the intervention group and 16.1% (n = 34) in the standard care group (difference, 15.2% [95% CI, 7.2%-23.1%]; OR, 2.37 [95% CI, 1.49-3.79]; P &lt; .001). Among patients achieving return of spontaneous circulation after out-of-hospital cardiac arrest, targeting an oxygen saturation of 90% to 94%, compared with 98% to 100%, until admission to the intensive care unit did not significantly improve survival to hospital discharge. Although the trial is limited by early termination due to the COVID-19 pandemic, the findings do not support use of an oxygen saturation target of 90% to 94% in the out-of-hospital setting after resuscitation from cardiac arrest. ClinicalTrials.gov Identifier: NCT03138005.

Stratified Flames in Dual Annular Counter-Rotating Swirl Burner for Wider Operability Gas Turbines

Abstract This study investigates numerically the effects of equivalence ratio (Φ) on flow/flame interactions and emissions of stratified oxy-methane (CH4/O2/CO2) flames in a dual annular counter-rotating swirl (DACRS) burner for wider operability and environmental-friendly gas turbines. The flow mixture entering the combustor is split into two coaxial streams of different equivalence ratios. The central stream is characterized by higher Φ to continuously ignite the flame for enhanced flame stability, whereas the annular stream is a highly lean mixture to sustain the environmental performance of the combustor. The partially premixed combustion model is adopted in the ansys-fluent 2021-r1 software to model the reaction kinetics of the generated stratified flames in the two-dimensional axisymmetric domain. Nine cases of the same inlet velocity ratio (primary stream to secondary stream) of 3.0 are examined at a fixed oxygen fraction (OF: volumetric percentage of oxygen in the O2/CO2 mixture) of both streams of 30%. Flame stratification is achieved by varying the equivalence ratios of the primary (Φp = 0.9, 0.8, and 0.7) and secondary (Φs = 0.7, 0.55, and 0.4) streams. The results indicate effective flame/flow interactions, complete combustion, and reduced emissions for the DACRS stratified flames.

High-throughput characterization of elastic moduli of Ti-Nb-Zr-O biomedical alloys fabricated by field-assisted sintering technique

Compositionally graded samples of Ti-xNb-7Zr-yO alloys (11 ≤ x ≤ 35, 0.49 ≤ y ≤1.01 wt%) were prepared from elemental powders and TiO2 and compacted by the field-assisted sintering technique. By this approach, four layered samples covering together twenty four different chemical compositions were prepared. It allowed efficient sampling of alloys for potential biomedical use. Elastic constants of each layer (the shear modulus G and the Young’s modulus E) were determined using resonant ultrasound spectroscopy. The results show that in the considered compositional space, elastic constants exhibit a dependence on the volume fraction of β-stabilizing niobium and interstitial oxygen. Minimum elastic modulus was achieved for the compositions close to the stability limit between parent β matrix and martensitic α″ phase, while maximum elastic constants were caused by the presence of isothermal ω particles.

Nitrogen cycling in western India as revealed by nitrogen isotopes, and the historic production of saltpetre

AbstractSaltpetre (KNO3) manufacture was a principal monopoly industry in early Modern India when the United Kingdom governed the social and economic systems. The process represented microbial transformation of excrementitious livestock and human wastes deposited around habitats, resulting in formation of salt efflorescence at an economic scale. Low caste people collected these wastes for extraction and production of rough saltpetre under the administrative control of British India. Stable isotope composition (δ15N and δ18O) was used to trace details of the microbial transformation processes, often involving the isotopic fractionation of nitrogen and oxygen. Marked elevation in δ15N and δ18O values for nitrates in soils and deposits, relative to those of primary organic nitrogen in diets and water sources, characterizes the unique processes of historic saltpetre manufacture in British India.

Strong Isotopic Fractionation of Oxygen in TiO2 Obtained by Surface-Enhanced Solid-State Diffusion.

Isotopically pure semiconductors have important applications for cooling electronic devices and quantum computing and sensing. Raw materials of sufficiently high isotopic purity are expensive and difficult to obtain; therefore, a post-synthesis method for removing isotopic impurities would be valuable. Through isotopic self-diffusion measurements of oxygen in rutile TiO2 single crystals immersed in water, we demonstrate fractionation of 18O by a factor of 3 below natural abundance in a near-surface region up to 10 nm wide. The submerged surface injects O interstitials that displace lattice 18O deeper into the solid as a result of the statistics of interstitialcy-mediated diffusion combined with steep chemical gradients of O interstitials. Slightly acidic and slightly basic liquid solutions both enhance the fractionation and affect the details of isotopic profile shapes through several chemical and physical mechanisms.