O2 Fraction Research Articles

Abstract 15332: Post-Resuscitation Epinephrine Infusion Restores Blood Pressure but Not Blood Flow in a Rat Model of Severe Pediatric Cardiac Arrest

Introduction: In children resuscitated from cardiac arrest (CA), post-arrest hypotension occurs often and worsens outcomes. Continuous infusion of epinephrine (Epi) is the 1st-line treatment for post-arrest hypotension but may worsen organ perfusion due to vasoconstriction. Hypothesis: Epi infusion after resuscitation from pediatric asphyxial CA restores blood pressure but not organ perfusion. Methods: Immature rats (PND18-22, n=34) underwent 11.5 minutes of asphyxial CA followed by resuscitation. Rats with hypotension (mean arterial pressure (MAP)<80% baseline) after resuscitation received infusions of either 0.9% NaCl (NS) or Epinephrine (Epi). MAP, carotid and femoral arterial blood flows (Fc, Ff) and renal oxygen tension (PrO2) were recorded. Results: One hour after resuscitation, MAP, Fc and Ff were 61.73 ± 2.68; 42.58 ± 3.84; and 19.53 ± 7.00 % of baseline, respectively. Epi infusion increased MAP in a dose-dependent manner, reaching 95.13 ± 7.93 % of baseline at 0.5 μg/kg/min. In contrast, Epi infusion up to 0.5 μg/kg/min increased Fc only to 49.55 ± 6.49 and Ff to 53.28 ± 7.13 % of baseline. NS infusion at equivalent volume had a more salutary effect than Epi on improving blood flow (Fc 64.62 ± 6.64 and Ff 60.25 ± 7.60 % of baseline). PrO2 reached 100% of baseline with Epi infusion and inspired O2 fraction (FiO2) = 1. However, at FiO2 = 0.21, Epi failed to restore PrO2 which reached 42% of baseline. Interestingly, a single 10 cc/kg NS bolus increased PrO2 to 100% of baseline at all FiO2 tested. Conclusions: In this rat model of severe pediatric asphyxial CA and resuscitation, post-resuscitation Epi infusion failed to restore carotid and femoral arterial blood flow despite normalizing blood pressure. Furthermore, Epi infusion restored neither renal perfusion nor oxygenation. In contrast, infusion of NS at comparable volumes was more effective than Epi at normalizing carotid and femoral blood flows as well as renal oxygenation. If validated in a large animal model, these results may indicate that Epi infusion after CA resuscitation contributes to organ injury and morbidity in children.

Effectiveness, implementation, and monitoring variables of intermittent hypoxic bicycle training in patients recovered from COVID-19: The AEROBICOVID study.

Hypoxic exposure is safely associated with exercise for many pathological conditions, providing additional effects on health outcomes. COVID-19 is a new disease, so the physiological repercussions caused by exercise in affected patients and the safety of exposure to hypoxia in these conditions are still unknown. Due to the effects of the disease on the respiratory system and following the sequence of AEROBICOVID research work, this study aimed to evaluate the effectiveness, tolerance and acute safety of 24 bicycle training sessions performed under intermittent hypoxic conditions through analysis of peripheral oxyhemoglobin saturation (SpO2), heart rate (HR), rate of perceived exertion (RPE), blood lactate concentration ([La-]) and symptoms of acute mountain sickness in patients recovered from COVID-19. Participants were allocated to three training groups: the normoxia group (GN) remained in normoxia (inspired fraction of O2 (FiO2) of ∼20.9%, a city with 526m altitude) for the entire session; the recovery hypoxia group (GHR) was exposed to hypoxia (FiO2 ∼13.5%, corresponding to 3,000m altitude) all the time except during the effort; the hypoxia group (GH) trained in hypoxia (FiO2 ∼13.5%) throughout the session. The altitude simulation effectively reduced SpO2 mean with significant differences between groups GN, GHR, and GH, being 96.9(1.6), 95.1(3.1), and 87.7(6.5), respectively. Additionally, the proposed exercise and hypoxic stimulus was well-tolerated, since 93% of participants showed no or moderate acute mountain sickness symptoms; maintained nearly 80% of sets at target heart rate; and most frequently reporting session intensity as an RPE of "3" (moderate). The internal load calculation, analyzed through training impulse (TRIMP), calculated using HR [TRIMPHR = HR * training volume (min)] and RPE [TRIMPRPE = RPE * training volume (min)], showed no significant difference between groups. The current strategy effectively promoted the altitude simulation and monitoring variables, being well-tolerated and safely acute exposure, as the low Lake Louise scores and the stable HR, SpO2, and RPE values showed during the sessions.

Mechanical ventilation characteristics and their prediction performance for the risk of moderate and severe bronchopulmonary dysplasia in infants with gestational age <30 weeks and birth weight <1,500 g

Moderate and severe bronchopulmonary dysplasia (BPD) is a common pulmonary complication in premature infants, which seriously affects their survival rate and quality of life. This study aimed to describe the mechanical ventilation characteristics and evaluate their prediction performance for the risk of moderate and severe BPD in infants with gestational age <30 weeks and birth weight <1,500 g on postnatal Day 14. In this retrospective cohort study, 412 infants with gestational age <30 weeks and birth weight <1,500 g were included in the analysis, including 104 infants with moderate and severe BPD and 308 infants without moderate and severe BPD (as controls). LASSO regression was used to optimize variable selection, and Logistic regression was applied to build a predictive model. Nomograms were developed visually using the selected variables. To validate the model, receiver operating characteristic (ROC) curve, calibration plot, and clinical impact curve were used. From the original 28 variables studied, six predictors, namely birth weight, 5 min apgar score, neonatal respiratory distress syndrome (≥Class II), neonatal pneumonia, duration of invasive mechanical ventilation (IMV) and maximum of FiO2 (fraction of inspiration O2) were identified by LASSO regression analysis. The model constructed using these six predictors and a proven risk factor (gestational age) displayed good prediction performance for moderate and severe BPD, with an area under the ROC of 0.917 (sensitivity = 0.897, specificity = 0.797) in the training set and 0.931 (sensitivity = 0.885, specificity = 0.844) in the validation set, and was well calibrated (P Hosmer-Lemeshow test = 0.727 and 0.809 for the training and validation set, respectively). The model included gestational age, birth weight, 5 min apgar score, neonatal respiratory distress syndrome (≥Class II), neonatal pneumonia, duration of IMV and maximum of FiO2 had good prediction performance for predicting moderate and severe BPD in infants with gestational age <30 weeks and birth weight <1,500 g on postnatal Day 14.

Formation and consumption of HO2 radicals in ns pulse O2–He plasmas over a liquid water surface

Hydroperoxyl (HO2) radicals are an important precursor in the formation of hydrogen peroxide (H2O2), a key species in plasma-liquid interactions, such that their formation and consumption pathways need to be understood. In this work, the generation and decay of HO2 have been studied in a controlled environment, in ns pulse discharge O2–He plasmas in contact with a liquid water surface. For this, time-resolved, absolute number densities of HO2 in O2–He mixtures excited by a repetitive ns pulse discharge are measured in situ by cavity ring down spectroscopy (CRDS). The discharge cell with external electrodes to generate the plasma and a water reservoir are integrated into the CRDS cavity. The high-reflectivity cavity mirrors are purged with helium to protect them from water vapor condensation. The experimental results are obtained at near room temperature, both during the discharge pulse burst and in the afterglow. The HO2 number density is inferred from the CRDS data using a spectral model exhibiting good agreement with previous measurements of absolute HO2 absorption cross sections. HO2 is generated during the discharge burst and decays in the afterglow between the bursts. The HO2 number density is also measured vs. the O2 fraction in the mixture. Comparison with the kinetic modeling predictions demonstrates good agreement with the data and identifies the dominant HO2 generation and decay processes. HO2 in the plasma is formed predominantly by the recombination of H atoms, generated by the electron impact dissociation of water vapor, with O2 molecules. Reactions with O atoms and hydroxyl (OH) radicals are among the main HO2 decay processes in the afterglow. HO2 is also detected when O2 is not present in the mixture. In this case, it is generated primarily by the recombination of OH radicals, via the formation of H2O2. The results demonstrate that CRDS can also be used for HO2 and other plasma chemical reaction product measurements in atmospheric pressure plasma jets impinging on a liquid water surface in ambient air.

Investigation on charged particles in inductively coupled Ar/O2 plasmas: The role of Ar proportion

In this paper, a 2D fluid model is built to reveal the inductively coupled Ar/O2 plasma behavior at 300 W, 30 mTorr, in the gas mixture of 95% Ar −5% O2 and 10% Ar −90% O2. The reliability of the model is first verified by comparing the calculated results with the experimental data, and the consistent results are obtained. Then, the spatial distributions of the charged species densities are investigated. As Ar fraction decreases, the maximum densities of charged particles shift toward the coil significantly, and the O2+ becomes the dominant positive ion at higher O2 fractions. The main reaction mechanisms are also discussed. It is concluded that the electrons are generated by the ionization of background gases, and the Ar+ ions are primarily formed by the ionization of Ar. However, the charge exchange processes account for the most production of O2+ and O+ ions at a high Ar fraction. The loss at the walls is the most important process to the consumption of positive ions. For the O− ions, they are first generated by the dissociative attachment of O2 at ground state, followed by the metastable state, and they are destroyed either by the ion–ion recombination with Ar+ ions or the detachment with O atoms as the Ar proportion varies. Finally, the effect of the ion–ion recombination reaction rate coefficients is discussed. The results indicate that rate coefficients of the recombination reactions have a significant influence on the positive ion densities when the Ar fractions are high.

An Analysis of the Effect of Noninvasive Positive Pressure Ventilation on Patients with Respiratory Failure Complicated by Diabetes Mellitus.

Objective To observe the clinical effectiveness of noninvasive positive pressure ventilation in patients with respiratory failure complicated by diabetes. Methods From May 2021 to May 2022, 90 patients with respiratory failure complicated by diabetes treated in our hospital were recruited and randomly assigned to receive either medication (control group) or noninvasive positive pressure ventilation (study group), with 45 patients in each group. The clinical endpoint was therapeutic outcomes. Results Noninvasive positive pressure ventilation resulted in significantly lower Self-Rating Anxiety Scale (SAS) and Self-Rating Depression Scale (SDS) scores versus medications (P < 0.05). Patients with noninvasive positive pressure ventilation showed better pulmonary function indices versus those with medications (P > 0.05). There was no significant difference in arterial oxygen (PaO2), carbon dioxide partial pressure (PaCO2), and arterial oxygen pressure/inspired fraction of O2 (PaO2/FiO2) between the two groups prior to the intervention (P > 0.05). However, patients in the study group had significantly elevated PaO2 and PaO2/FiO2 and lower PaCO2 levels than those in the control group (P < 0.05). Following the intervention, noninvasive positive pressure ventilation resulted in significantly lower inflammatory factor levels versus medications (P > 0.05). After the intervention, markedly better glucose control was observed in the study group versus the control group (P < 0.05). The incidence of complications in the control group was 2.38%, which was significantly lower than that of the control group (16.67) (P < 0.05). Conclusion Noninvasive positive pressure ventilation effectively suppresses the inflammatory response, improves the blood gas analysis index, and eliminates the negative emotions of patients, thereby maintaining hemodynamic stability and improving clinical efficacy with a better safety profile. Further studies are recommended prior to clinical promotion.

A randomized controlled trial of positive end-expiratory pressure on pulmonary oxygenation and biventricular function in esophageal cancer patients receiving one-lung ventilation under a lower FiO2

Arterial oxygenation is often impaired during one-lung ventilation (OLV), due to both pulmonary shunt and atelectasis. Lower fraction of inspiration O2 (FiO2) may reduce inflammation and complications, but may increase the risk of hypoxemia. The aim of this randomized controlled parallel trial was to analyze whether higher positive end-expiratory pressure (PEEP) could improve oxygenation and maintain lower levels of inflammation during OLV under a lower FiO2. One hundred and twenty patients with selective thoracotomy for esophageal cancer (EC) were classified randomly into four groups on a ratio of 1:1:1:1 using a computer-generated list, including Group A (FiO2 =0.6, PEEP =0), Group B (FiO2 =0.6, PEEP =5 cmH2O), Group C (FiO2 =1.0, PEEP =8 cmH2O), and Group D (FiO2 =1.0, PEEP =10 cmH2O). The oxygenation and pulmonary shunt were primary outcomes. Haemodynamics, respiratory mechanics, serum IL-6 and IL-10 levels, and complications were taken as secondary outcomes. Follow-up was terminated until discharge. Two patients in Group A and two in Group D were excluded due to hypoxemia and hypotension, respectively. Then the data of 116 patients (Group A =28, Group B =30 Group C =30, and Group D =28) were assessed for final analysis. Compared with Group B, the partial pressure of oxygen (PaO2) and dynamic compliance during OLV in Group D were significantly increased from 15 minutes to 60 minutes, while pulmonary shunt was significantly decreased (P>0.05). Patients in Group D had higher levels of central venous pressure (CVP) and airway pressure (Paw) during OLV and higher levels of IL-6 and IL-10 after OLV compared with Group B (P>0.05). No statistical differences were found in oxygen saturation (SaO2), PvO2 (partial pressure of oxygen in venous blood), partial pressure of end-tidal carbon dioxide (ETCO2), partial pressure of carbon dioxide in artery (PaCO2), heart rate (HR), mean arterial pressure (MAP), and complications among the four groups (P>0.05). Higher PEEP increased the oxygenation under 60% O2 during OLV. However, the haemodynamics and respiratory mechanics changed, and the levels of inflammation increased. A higher PEEP under 60% O2 during OLV is not recommended. Chinese Clinical Trial Registry ChiCTR1900024726.

Non-invasive ventilation for preoxygenation before general anesthesia: a systematic review and meta-analysis of randomized controlled trials

Background and objectivesPreoxygenation is crucial for providing sufficient oxygen reservoir to a patient before intubation and enables the extension of the period between breathing termination and critical desaturation (safe apnoea time). Conventionally, face mask ventilation is used for preoxygenation. Non-invasive ventilation is a new preoxygenation method. The study objective was to compare the outcomes of non-invasive ventilation and face mask ventilation for preoxygenation.MethodPubMed, Embase, Cochrane Library, and the ClinicalTrials.gov registry were searched for eligible studies published from database inception to September 2021. Individual effect sizes were standardized, and a meta-analysis was conducted using random effects models to calculate the pooled effect size. Inclusion criteria were randomised controlled trials of comparing the outcomes of non-invasive ventilation or face mask ventilation for preoxygenation in patients scheduled for surgeries. The primary outcome was safe apnea time, and the secondary outcomes were post-operative complications, number of patients who achieved the expired O2 fraction (FeO2) after 3 min of preoxygenation, minimal SpO2 during tracheal intubation, partial pressure of oxygen in the arterial blood (PaO2) and partial pressure of carbon dioxide (PaCO2) after preoxygenation, and PaO2 and PaCO2 after tracheal intubation.Results13 trials were eligible for inclusion in this study. Significant differences were observed in safe apnoea time, number of patients who achieved FeO2 90% after preoxygenation for 3 min, and PaO2 and PaCO2 after preoxygenation and tracheal intubation. Only in the non-obese subgroup, no significant difference was observed in safe apnoea time (mean difference: 125.38, 95% confidence interval: − 12.26 to 263.03).ConclusionNon-invasive ventilation appeared to be more effective than conventional methods for preoxygenation. We recommend non-invasive ventilation based on our results.

Air-CO2 and oxygen-enriched air-CO2 biomass gasification in an autothermal downdraft gasifier: Experimental studies

The mounting CO2 emission and rapid depletion of fossil fuels are two significant challenges for sustaining growing energy requirements and keeping the environment clean. Biomass gasification using CO2 as a gasifying agent may be one of the alternative techniques to tackle such emerging problems. CO2 behaves as an inert gas at low temperatures and can be converted to CO at high temperatures. In the present study, air-CO2 and oxygen-enriched air-CO2 biomass gasification are successfully conducted in the autothermal reactor. The impacts of varying concentrations of CO2 and oxygen in the gasifying agent on the performance of the gasifier are analyzed. The CO2 content in the gasifying agent is varied from 0 to 45 vol% at two different oxygen concentrations (21 and 35 vol%). The reactor used is an Imbert-type downdraft gasifier with a thermal capacity of approximately 10 kW. The results reveal that the yield of CO in the producer gas increases compared to air gasification resulting in a higher heating value of the producer gas. However, the average temperature in the gasifier reduces with increasing CO2 percentage in the gasifying agent. Upon increasing the O2 fraction from 21 to 35 vol%, while keeping 30 vol% CO2 content constant, CO content is found to upsurge from 23.96 to 31.37 vol%. The inclusion of CO2 inside the gasifier promotes the endothermic Boudouard reaction that causes the conversion of CO2 into CO.

Numerical simulation of CO emission in a sintering pot under flue gas recirculation

A transient two-dimensional sintering model coupling porous medium flow, interphase heat mass transfer and reactions was established through computational fluid dynamics (CFD) method by Comsol Multiphysics 6.0 for a sintering pot under sintering flue gas recirculation (SFGR). The ignition was considered and CO was the carbon combustion intermediate and experienced catalytic oxidation in the ferric oxide bed. The model was verified by sintering pot experimental data of flue gas temperature and components fractions with maximum deviation less than 10 %. The bed temperature, CO emission and solid fuel consumption were focused under different SFGR parameters by the verified model. Ignition was important for the beginning flue gas component fractions, especially when the bed height was less than 700 mm. The effect of SFGR parameters on the maximum bed temperature (MBT) was sequenced: inlet gas velocity > inlet CO fraction > inlet O2 fraction > inlet gas temperature. MBT grew up when each of the four parameters increased. The impact on the CO emission was different: inlet CO fraction > inlet O2 fraction > inlet gas velocity > inlet gas temperature. CO emission declined when each of the parameters increased. The total reaction rate of CO was studied for explanation. The reduction of solid fuel consumption was studied by energy conservation to evaluate the influence of inlet CO, inlet gas temperature and flue gas recirculation fraction. The three factors had positive linear correlation with solid fuel consumption reduction. The reduction maximally reached 16.6 % at flue gas recirculation fraction of 50 %, inlet 2 % CO and 473.15 K temperature, providing theoretical support for SFGR application.

Studies of Low and Intermediate Temperature Oxidation of Propane up to 100 Atm in a Supercritical-Pressure Jet-Stirred Reactor

The low and intermediate temperature oxidation of propane has been investigated by using a novel supercritical pressure jet stirred reactor (SP-JSR) with and without 20% CO2 additions at fuel lean and rich conditions at 10 and 100 atm and 500–1000 K. The mole fractions of C3H8, O2, CO, CO2, CH2O, C2H4, CH3CHO, and C3H6 were quantified by using a micro-gas chromatograph (µ-GC). The experiment showed that different from that of 10 atm, at 100 atm only a weak negative temperature coefficient (NTC) behavior was observed because of the significant shift of the intermediate temperature HO2 chemistry to lower temperature. In addition, at 100 atm, existing models in literatures could successfully capture the onset temperatures of the low and intermediate chemistry, while under-predict the fuel oxidation quantitatively and fail to capture the NTC behavior between 650 and 780 K at both fuel lean and rich conditions. Similar discrepancy was observed in studies of n-butane and dimethyl ether (DME) oxidations in literatures, implying that there existed large uncertainties in hierarchy model development of fuels with low temperature chemistries at extremely high pressures. Reaction pathways and sensitivity analyses showed that RO2 competing reactions through (P1) RO2 = QOOH, (P2) RO2 = C3H6 + HO2, (P3) RO2 + CH2O/HO2 = RO2H + HCO / O2 dominated the low and intermediate temperature chemistries, followed by HO2 / H2O2 chemistry at 100 atm, which differed from the dominant pathway through QOOH consumption reactions at lower pressures. Especially, P3 is a new pathway of RO2 consumption at high pressures, which was not observed in importance at low pressures. Special attention should be paid to the accurate computations of n-C3H7O2 / i-C3H7O2 + CH2O and n-C3H7O2 / i-C3H7O2 + in the P3 pathway and n-C3H7O2 / i-C3H7O2 decomposition reactions in the P2 pathway at high pressures.

Hyperoxia by short-term promotes oxidative damage and mitochondrial dysfunction in rat brain

Oxygen (O2) therapy is used as a therapeutic protocol to prevent or treat hypoxia. However, a high inspired fraction of O2 (FIO2) promotes hyperoxia, a harmful condition for the central nervous system (CNS). The present study evaluated parameters of oxidative stress and mitochondrial dysfunction in the brain of rats exposed to different FIO2. Male Wistar rats were exposed to hyperoxia (FIO2 40 % and 60 %) compared to the control group (FIO2 21 %) for 2 h. Oxidative stress, neutrophilic infiltration, and mitochondrial respiratory chain enzymes were determined in the hippocampus, striatum, cerebellum, cortex, and prefrontal cortex after O2 exposure. The animals exposed to hyperoxia showed increased lipid peroxidation, formation of carbonyl proteins, N/N concentration, and neutrophilic infiltration in some brain regions, like hippocampus, striatum, and cerebellum being the most affected. Furthermore, CAT activity and activity of mitochondrial enzyme complexes were also altered after exposure to hyperoxia. Rats exposed to hyperoxia showed increase in oxidative stress parameters and mitochondrial dysfunction in brain structures.

New classification method of coal spontaneous combustion three zones in the goaf based on non-parametric kernel density estimation.

The accurate division of three zones of coal spontaneous combustion in the goaf plays a vital role for coal fire prevention. Based on the O2 and CO volume fraction acquired from in situ test, this paper first fits the linear equation (characteristic equation) of O2 volume fraction with the length of the goaf. Then a cloud map of the kernel density distribution of O2 and CO volume fraction and the length of the goaf was drawn. According to the cloud map of CO, the distribution interval of CO volume fraction can be obtained, in which 0-100 ppm is the acceptable range, and greater than 100 ppm is the dangerous range, which can be used as a critical indicator for early warning of coal spontaneous combustion. According to the kernel density distribution cloud map of O2 volume fraction, there are 3 peaks of the kernel density of O2 volume fraction. According to the difference test, the 3 goaf lengths (characteristic lengths) corresponding to the 3 kernel density peaks are determined to be 12 m, 34 m, and 59 m, respectively. The characteristic O2 volume fractions are obtained by substituting characteristic lengths into the characteristic equation, which are 17.9%, 13.6%, and 8.9%. Different from the traditional dividing method, the characteristic O2 volume fractions and characteristic lengths divide the goaf into four areas: the heat dissipation zone, the first oxidation zone, the second oxidation zone, and the asphyxiation zone. The results of this study could refine the division of coal spontaneous combustion dangerous areas, reflect the dynamic change process of coal spontaneous combustion dangerous areas, and improve the efficiency of coal spontaneous combustion prevention.

A numerical study on the combustion limits of mesoscale methane jet flames with hydrogen addition

A meso-scale jet flame model was established for the flame ports of domestic gas stoves. The influences of hydrogen addition ratio (β = 0%–25%) on the combustion limits were explored. The results show that with the increase of hydrogen addition ratio, the blow-off limit increases obviously, while the extinction limit decreases slightly, namely, the combustible range expands significantly. Quantitative analysis was carried out in terms of chemical effect and thermal effect. It was found that hydrogen addition will reduce O2 fraction in the pre-mixture for a constant equivalence ratio. Under near-extinction limit condition, since the flame is located at the nozzle exit, the external O2 cannot be entrained into or diffuse into the upstream of the flame, which leads to the decrease of reaction rate. However, for the near-blow-off cases, the external O2 can be entrained and diffuse into the flame, which compensates the difference of O2 content in the pre-mixture. Therefore, the combustion reaction is enhanced by hydrogen addition because more H radicals can be produced. In addition, as the flame is located closer to the tube with the increase of hydrogen addition ratio, heat transfer between flame and tube wall is augmented and the preheating of fresh mixture is strengthened by the inner tube wall. This heat recirculation effect becomes especially notable in low velocity cases. In conclusion, the extension of extinction limit by hydrogen addition is attributed to the thermal effect, while the increase of blow-off limit is mainly due to the intensification of chemical effect.

Too much tolerance for hyperoxemia in mechanically ventilated patients with SARS-CoV-2 pneumonia? Report from an Italian intensive care unit.

BackgroundIn COVID-19 patients requiring mechanical ventilation, the administration of high oxygen (O2) doses for prolonged time periods may be necessary. Although life-saving in most cases, O2 may exert deleterious effects if administered in excessive concentrations. We aimed to describe the prevalence of hyperoxemia and excessive O2 administration in mechanically ventilated patients with SARS-CoV-2 pneumonia and determine whether hyperoxemia is associated with mortality in the Intensive Care Unit (ICU) or the onset of ventilator-associated pneumonia (VAP).Materials and methodsRetrospective single-center study on adult patients with SARS-CoV-2 pneumonia requiring invasive mechanical ventilation for ≥48 h. Patients undergoing extracorporeal respiratory support were excluded. We calculated the excess O2 administered based on the ideal arterial O2 tension (PaO2) target of 55–80 mmHg. We defined hyperoxemia as PaO2 > 100 mmHg and hyperoxia + hyperoxemia as an inspired O2 fraction (FiO2) > 60% + PaO2 > 100 mmHg. Risk factors for ICU-mortality and VAP were assessed through multivariate analyses.ResultsOne hundred thirty-four patients were included. For each day of mechanical ventilation, each patient received a median excess O2 of 1,121 [829–1,449] L. Hyperoxemia was found in 38 [27–55]% of arterial blood gases, hyperoxia + hyperoxemia in 11 [5–18]% of cases. The FiO2 was not reduced in 69 [62–76]% of cases of hyperoxemia. Adjustments were made more frequently with higher PaO2 or initial FiO2 levels. ICU-mortality was 32%. VAP was diagnosed in 48.5% of patients. Hyperoxemia (OR 1.300 95% CI [1.097–1.542]), time of exposure to hyperoxemia (OR 2.758 [1.406–5.411]), hyperoxia + hyperoxemia (OR 1.144 [1.008–1.298]), and daily excess O2 (OR 1.003 [1.001–1.005]) were associated with higher risk for ICU-mortality, independently of age, Sequential Organ failure Assessment score at ICU-admission and mean PaO2/FiO2. Hyperoxemia (OR 1.033 [1.006–1.061]), time of exposure to hyperoxemia (OR 1.108 [1.018–1.206]), hyperoxia + hyperoxemia (OR 1.038 [1.003–1.075]), and daily excess O2 (OR 1.001 [1.000–1.001]) were identified as risk factors for VAP, independently of body mass index, blood transfusions, days of neuromuscular blocking agents (before VAP), prolonged prone positioning and mean PaO2/FiO2 before VAP.ConclusionExcess O2 administration and hyperoxemia were common in mechanically ventilated patients with SARS-CoV-2 pneumonia. The exposure to hyperoxemia may be associated with ICU-mortality and greater risk for VAP.

High-flow nasal oxygen therapy in patients after esophageal interventions: аdvantages and disadvantages

BACKGROUND: Pulmonary complications in patients who underwent esophagectomy with one-stage esophagoplasty are a frequent cause of death in the intensive care unit (ICU). However, the use of noninvasive ventilation (NIV) in these patients is not indicated because of the failure of esophagogastric anastomosis. Compared with NIV and standard oxygen therapy, high-flow oxygen therapy (HFOT) reduces the rate of transfer to mechanical ventilation (MV) in the case of acute respiratory failure.&#x0D; AIM: This study aimed to assess the clinical advantages and disadvantages of HFOT in patients with respiratory failure after esophagectomy.&#x0D; MATERIALS AND METHODS: Ninety patients with esophagectomy were examined. Two groups were formed by randomization: group 1 (n=45) with standard respiratory therapy, incentive spirometry, and nasal oxygen therapy with NIV sessions and low end-expiratory pressure (up to 6 mmHg) and group 2 (n=45) with HFOT. Therapy parameters were selected according to oxygenation (PaO2/FiО2) and saturation (SaО2) index values. Parameter changes, session duration, patients tolerance to respiratory therapy methods (from 1 to 10 points), dynamics of chest X-ray pattern, and duration of treatment in ICU were analyzed.&#x0D; RESULTS: The advantages of HFOT were the absence of discomfort during the session, possibility to decrease O2 flow required for an adequate level of oxygenation, high flow with controlled O2 fraction allowed to reach target values of oxygenation index, decreased frequency of patients transfer to MV, and time spent in ICU.&#x0D; CONCLUSIONS: The use of HFOT is justified as part of the complex respiratory therapy in patients with moderate respiratory failure. In patients with severe respiratory failure, HFOT is an alternative to other high-flow techniques and NIV. The choice between these methods should be individualized and depend on the patients condition and ventilation requirement.

Pulmonary gas exchange evaluated by machine learning: a computer simulation

Using computer simulation we investigated whether machine learning (ML) analysis of selected ICU monitoring data can quantify pulmonary gas exchange in multi-compartment format. A 21 compartment ventilation/perfusion (V/Q) model of pulmonary blood flow processed 34,551 combinations of cardiac output, hemoglobin concentration, standard P50, base excess, VO2 and VCO2 plus three model-defining parameters: shunt, log SD and mean V/Q. From these inputs the model produced paired arterial blood gases, first with the inspired O2 fraction (FiO2) adjusted to arterial saturation (SaO2) = 0.90, and second with FiO2 increased by 0.1. ‘Stacked regressor’ ML ensembles were trained/validated on 90% of this dataset. The remainder with shunt, log SD, and mean ‘held back’ formed the test-set. ‘Two-Point’ ML estimates of shunt, log SD and mean utilized data from both FiO2 settings. ‘Single-Point’ estimates used only data from SaO2 = 0.90. From 3454 test gas exchange scenarios, two-point shunt, log SD and mean estimates produced linear regression models versus true values with slopes ~ 1.00, intercepts ~ 0.00 and R2 ~ 1.00. Kernel density and Bland–Altman plots confirmed close agreement. Single-point estimates were less accurate: R2 = 0.77–0.89, slope = 0.991–0.993, intercept = 0.009–0.334. ML applications using blood gas, indirect calorimetry, and cardiac output data can quantify pulmonary gas exchange in terms describing a 20 compartment V/Q model of pulmonary blood flow. High fidelity reports require data from two FiO2 settings.

Development and validation of a survival prediction model for patients received mechanical ventilation in the intensive care unit: a large sample size cohort from the MIMIC database.

Mechanical ventilation remains one of the primary management measures for critically ill patients in intensive care units (ICUs). However, previous studies on the prognosis prediction of ICU patients received mechanical ventilation were limited. This study was to develop and validate a nomogram for predicting short- and long-term survival among patients who received mechanical ventilation in the ICU. This was a retrospective cohort study with a 3-year follow-up. Demographic, laboratory, clinical data of 16,775 participants aged ≥18 years who received mechanical ventilation in the ICU were extracted from the Medical Information Mart for Intensive Care III (MIMIC-III) database. The outcomes of this study were 1-month, 3-month, 1-year, and 3-year survival. All eligible patients were randomly classified into the training and testing groups with a ratio of 7:3. A multivariate Cox regression in the training group was used to explore the predictors and develop the predictive nomogram. Internal and subgroup validations were performed, and the C-index was calculated to estimate the predictive performance of the nomogram. The time-dependent receiver operating characteristic curves were drawn, and corresponding areas under the curve (AUC) were calculated. Totally 6,291 patients died during the follow-up duration. Age, gender, ethnicity, ICU type, comorbidity, days of mechanical ventilation, white blood cell count, blood urea nitrogen, the fraction of inspiration O2, Sequential Organ Failure Assessment scores, and the Glasgow coma score were predictors of the survival of ICU patients who received mechanical ventilation (P<0.05). The C-index of the nomogram was 0.819 and was validated in the testing group at 0.816. The AUCs for the prognostic nomogram for 1-month, 3-month, 1-year, and 3-year survival were 0.889, 0.892, 0.882, and 0.866, respectively. This nomogram showed good predictive performance for short- and long-term survival in ICU patients treated with mechanical ventilation, which may be a useful tool for clinicians to assess the prognosis of patients and to adjust treatment strategies in time.

0742 Characteristics of the Low ArTH phenotype in patients with OSA

Abstract Introduction Obstructive sleep apnea (OSA) is a heterogenous disease with both anatomic and nonanatomic factors contributing to the pathophysiology. Recently low arousal threshold (ArTH) has been described in some patients with sleep apnea and there is early evidence emerging that it could be a clinical phenotype. The aim of this study was to characterize this phenotype in a large cohort of patients with sleep apnea confirmed by overnight polysomnography Methods The setting was a community sleep center. We performed a retrospective review of patient charts. We included patients who underwent full-night diagnostic PSG. OSA was defined as an apnea hypopnea index (AHI) of &amp;gt; 5. Epworth score, body mass index (BMI), neck circumference, and upper airway size using Modified Friedman (MF) were recorded. Low ArTH was calculated using AHI, fraction of hypopneas and O2 nadir.Abnormal airway narrowing was defined by MF &amp;gt;2. Large neck was defined by neck circumference ≥ 17 inches in males or ≥ 16 in females. Obesity was defined by BMI&amp;gt;30 kg/m2. Results 652 patients were included - 421(65%) were male, and 230 (35%) female. 299 (46%) of patients had a low ArTH phenotype. Mean age was similar in both groups 54 +/- 14 vs 55 +/- 13 years. Male % was less pronounced in the low ArTH group (57% of patients with low ArTH male vs 71% of without low ArTH; p&amp;lt;0.05). Patients with a low ArTH had lower percentage of abnormal airway narrowing (53.5 vs 62.6%, p&amp;lt;0.001), large neck circumference ( 64.6 vs 78.8%, p&amp;lt;0.001) and obesity (65.6 vs 77.9%, p&amp;lt;0.001). Average BMI was lower in the low ArTH group (34.8 +/- 8 vs 36.9 +/- 8; p &amp;lt; 0.005), and neck circumference was also lower in low ArTH group (NC 16.5 +/- 1.8 vs 17.4 +/- 1.8 respectively). Epworth sleepiness scale was lower in low ArTh group (10 +/- 8 vs 11 +/- 9; p 0.007) Conclusion We describe the phenotypic characteristics of low ArTH phenotype in a large cohort of patients with OSA. Patients with low ArTH have lower BMI, lower neck circumference, and lower Modified Friedman. Further research studies should focus on whether there are differences in therapeutic responses to this phenotype, and what clinical characteristics might help clinicians more effectively detect this phenotype. Support (If Any) NA

Comparative Analysis of Cardiorespiratory Parameters of Basketball and Soccer Players Using Principal Component Analysis

Principal component analysis (PCA) is a statistical technique used to identify variations in multivariate data obtained during the performance of the maximum ergospirometry test (MET). To use the PCA to compare the coefficients of change of the principal component (PC1) using the eigenvalue and the maximum values ​​of the cardiorespiratory variables obtained in the athletes' in MET. 10 soccer players and 10 basketball players, all male, were evaluated. The PCA analyzed the values ​​of the variables during the performance of the MET. The PC1 for each variable was calculated, and the eigenvalue was generated, representing the coefficients of variation of the PC1 of all variables. In the quantitative assessment (maximum values), a higher VO2max (3.93±0.62 vs. 3.41±0.37 l·min-1) was observed in basketball players compared to soccer players (p&lt;0.05). The qualitative evaluation using PC1 of cardiorespiratory parameters (heart rate, minute volume, O2 consumption, CO2 production, expired fraction of O2 and expired fraction CO2) was observed as an eigenvalue (6.50±0.27 vs. 6.22±0.19) high for basketball players compared to soccer players (p&lt;0.05). It is concluded that the basketball players showed more significant variability in their cardiorespiratory variables during the performance of the MET and higher VO2max at the end of the MET. These findings indicate that basketball players were less efficient in buffering the ventilatory acidosis observed during the MET. The results of this study highlight the importance of making complex assessments of the cardiorespiratory system, providing qualitative information to complement the quantitative data.