FiO2 Research Articles

Experimental study on the combustion and flame propagation characteristics of CH4/O2/N2 premixed turbulent jets

The combustion and flame propagation characteristics of CH4/O2/N2 premixed turbulent jets are investigated experimentally in a constant volume chamber (CVC) under different initial temperature (Tini, 300/400/500/600K) and oxygen fractions (γ, 0.4/0.6/0.8/1.0) conditions using High-speed camera and schlieren system. Four types of jet tip velocity were found: primary vortex motion at the jet top (M-type 1), secondary vortex motion (M-type 2), weaker positive and negative feedback between the flame and the flow field (M-type 3), and stronger positive and negative feedback (N-type 4). With the decrease of γ, the jet acceleration and deceleration mechanism is changed from the top vortex motion mechanism in M-type 1 and M-type 2 to the positive and negative feedback mechanism in M-type 3 and N-type 4. The interaction between the pulsating flow field and the heat release from the pre-chamber transitions to the flow field momentum dissipation. For M-type 1 and M-type 2, there is no significant difference in overpressure dynamics. The N-type 4 exhibits lower peak pressure and pressure rise rates. Moreover, the flame mode was predicted under higher Pini (10 bar ≤ Pini) and lower γ (γ ≤ 0.4) based on empirical equations established by the self-similar analytical model.

Prediction of Initial CRP/Albumin Ratio on In-Hospital Mortality in Isolated Traumatic Brain Injury Patients.

The CRP/albumin ratio (CAR) is a mortality predictor in intensive care unit (ICU) patients. The aim of the current study was to investigate the ability of CAR to predict in-hospital mortality (IHM) in patients with isolated traumatic brain injury (iTBI). We performed a retrospective analysis including 200 patients with iTBI admitted to our neurosurgical intensive care unit (NICU) between September 2014 and December 2016. Serum biomarkers, demographic and radiological data, several ICU scores, and cardiopulmonary parameters were analyzed. The rate of IHM was 27.5% (55/200) and significantly associated with a higher AIS head score (p < 0.0001), a lower albumin level (p < 0.0001), and the necessity of a higher level of inspiratory oxygen fraction (p = 0.002). Furthermore, advanced age (odds ratio [OR] = 0.953, 95% confidence interval [CI] = 0.927-0.981, p = 0.001), a lower GCS score (OR = 1.347, 95% CI = 1.203-1.509, p < 0.0001), a higher level of lactate (OR = 0.506, 95% CI = 0.353-0.725, p < 0.0001), a higher CAR (OR = 0.547, 95% CI = 0.316-0.945, p = 0.031) and a higher norepinephrine application rate (OR = 0.000, 95% CI 0.000-0.090, p = 0.016) were identified as independent predictors of IHM. ROC analysis showed an association between IHM and a CAR cut-off value of >0.38 (Youden index 0.073, sensitivity: 27.9, specificity: 64.8, p = 0.044). We could identify a CAR > 0.38 as a new independent predictor for IHM in patients with iTBI.

Identifying risk factors for hypoxemia during emergence from anesthesia in patients undergoing robot-assisted laparoscopic radical prostatectomy.

Robot-assisted laparoscopic radical prostatectomy (RALP) has emerged as an effective treatment for prostate cancer with obvious advantages. This study aims to identify risk factors related to hypoxemia during the emergence from anesthesia in patients undergoing RALP. A cohort of 316 patients undergoing RALP was divided into two groups: the hypoxemia group (N = 134) and the non-hypoxemia group (N = 182), based on their postoperative oxygen fraction. Comprehensive data were collected from the hospital information system, including preoperative baseline parameters, intraoperative data, and postoperative recovery profiles. Risk factors were examined using multiple logistic regression analysis. The study showed that 38.9% of patients had low preoperative partial pressure of oxygen (PaO2) levels. Several clinical parameters showed significant differences between the hypoxemia group and the non-hypoxemia group, including weight (P < 0.0001), BMI (P < 0.0001), diabetes mellitus (P = 0.044), history of emphysema and pulmonary alveoli (P < 0.0001), low preoperative PaO2 (P < 0.0001), preoperative white blood cell count (P = 0.012), preoperative albumin (P = 0.048), intraoperative bleeding (P = 0.043), intraoperative CO2 accumulation (P = 0.001), duration of surgery (P = 0.046), postoperative hemoglobin level (P = 0.002), postoperative hypoxemia (P = 0.002), and early postoperative fever (P = 0.006). Multiple logistic regression analysis revealed BMI (adjusted odds ratio = 0.696, 95% confidence interval 0.612-0.719), low preoperative PaO2 (adjusted odds ratio = 9.119, 95% confidence interval 4.834-17.203), and history of emphysema and pulmonary alveoli (adjusted odds ratio = 2.804, 95% confidence interval 1.432-5.491) as independent factors significantly associated with hypoxemia on emergence from anesthesia in patients undergoing RALP. Our results demonstrate that BMI, lower preoperative PaO2, and a history of emphysema and pulmonary alveolar disease are independent risk factors associated with hypoxemia on emergence from anesthesia in patients undergoing RALP. These findings provide a theoretical framework for surgeons and anesthesiologists to facilitate strategies to mitigate postoperative hypoxemia in this unique patient population.

The impact and validity of the Berlin criteria on burn-induced ARDS: Examining mortality rates, and inhalation injury influences. A single center observational cohort study

BackgroundAs several recent studies have shown low mortality rates in burn injury induced ARDS early (≤7 days) after the burn, the Berlin criteria for the ARDS diagnosis in this setting may be disputed. Related to this issue, the present study investigated the incidence, trajectory and risk factors of early Acute Respiratory Distress Syndrome (ARDS) and outcome in burn patients, as per the Berlin criteria, along with the concurrent prevalence and influence of inhalation injury, and ventilator-acquired pneumonia (VAP). MethodsOver a 2.5-year period, burn patients with Total Burn Surface Area (TBSA) exceeding 10% admitted to a national burn center were included. The subgroup of interest comprised patients with more than 48 h of ventilatory support. This group was assessed for ARDS, inhalation injury, and VAP. ResultsOut of 292 admissions, 62 sustained burns > 10% TBSA. Of these, 28 (45%) underwent ventilatory support for over 48 h, almost all, 24 out of 28, meeting the criteria for ARDS early, within 7 days post-injury and with a PaO2/FiO2 (PF) ratio nadir at day 5. The mortality rate for this early ARDS group was under 10%, regardless of PF ratios (mean TBSA% 34,8%). Patients with concurrent inhalation injury and early ARDS showed significantly lower PF ratios (p < 0.001), and higher SOFA scores (p = 0.004) but without impact on mortality. Organ failure, indicated by SOFA scores, peaked early (day 3) and declined in the first week, mirroring PF ratio trends (p < 0.001). ConclusionsThe low mortality associated with early ARDS in burn patients in this study challenges the Berlin criteria’s for the early ARDS diagnosis, which for its validity relies on that higher mortality is linked to worsening PF ratios. The finding suggests alternative mechanisms, leading to the early ARDS diagnosis, such as the significant impact of inhalation injury on early PF ratios and organ failure, as seen in this study. The concurrence of early organ failure with declining PF ratios, supports, as expected, the hypothesis of trauma-induced inflammation/multi-organ failure mechanisms contributing to early ARDS. The study highlights the complexity in differentiating between the contributions of inhalation injury to early ARDS and the related organ dysfunction early in the burn care trajectory. The Berlin criteria for the ARDS diagnosis may not be fully applicable in the burn care setting, where the low mortality significantly deviates from that described in the original Berlin ARDS criteria publication but is as expected when considering the actual not very extensive burn injury sizes/Baux scores as in the present study.

Flow, combustion and species fields of premixed CH4/H2/CO syngas oxy-flames on a swirl burner: Effects of syngas composition

Addressing burning characteristics of syngas under oxy-combustion conditions in substantially CO2-diluted combustion environment for gas turbine combustion applications has rarely been reported. A detailed modeling study was performed over a broad range of syngas compositions at fixed inlet flow velocity of 6 m/s, fixed equivalence ratio of 0.42, and fixed oxygen fraction (OF) of 60% (by vol.). For validating the numerical model, the calculated results were compared against experimental results recorded from the same physical combustion setup. The effects of syngas composition on flow field, laminar flame speed (LFS), flame thickness, adiabatic flame temperature (AFT), combustor power density (PD), thermal power (TP), and species distributions were investigated. Adiabatic flame temperature increased from 2312 to 2388 K, LFS increased from 0.53 to 1.32 m/s, PD reduced from 2854 to 2672 kW/m3, and TP decreased from 4.0 to 3.7 kW when the hydrogen fraction (HF) was changed from 0 to 80%.When the HF was reduced from 90% to 10%, with excluding CH4, the AFT increased from 2447 to 2560 K, the LFS decreased from 2.01 to 0.46 m/s, the TP increased from 3.64 to 4.1 kW, and the PD increased from 2620 to 2923 kw/m3.

Oxygenation management during veno-arterial ECMO support for cardiogenic shock: a multicentric retrospective cohort study.

Hyperoxemia is common and associated with poor outcome during veno-arterial extracorporeal membrane oxygenation (VA ECMO) support for cardiogenic shock. However, little is known about practical daily management of oxygenation. Then, we aim to describe sweep gas oxygen fraction (FSO2), postoxygenator oxygen partial pressure (PPOSTO2), inspired oxygen fraction (FIO2), and right radial arterial oxygen partial pressure (PaO2) between day 1 and day 7 of peripheral VA ECMO support. We also aim to evaluate the association between oxygenation parameters and outcome. In this retrospective multicentric study, each participating center had to report data on the last 10 eligible patients for whom the ICU stay was terminated. Patients with extracorporeal cardiopulmonary resuscitation were excluded. Primary endpoint was individual mean FSO2 during the seven first days of ECMO support (FSO2mean (day 1-7)). Between August 2019 and March 2022, 139 patients were enrolled in 14 ECMO centers in France, and one in Switzerland. Among them, the median value for FSO2mean (day 1-7) was 70 [57; 79] % but varied according to center case volume. Compared to high volume centers, centers with less than 30 VA-ECMO runs per year were more likely to maintain FSO2 ≥ 70% (OR 5.04, CI 95% [1.39; 20.4], p = 0.017). Median value for right radial PaO2mean (day 1-7) was 114 [92; 145] mmHg, and decreased from 125 [86; 207] mmHg at day 1, to 97 [81; 133] mmHg at day 3 (p < 0.01). Severe hyperoxemia (i.e. right radial PaO2 ≥ 300 mmHg) occurred in 16 patients (12%). PPOSTO2, a surrogate of the lower body oxygenation, was measured in only 39 patients (28%) among four centers. The median value of PPOSTO2mean (day 1-7) value was 198 [169; 231] mmHg. By multivariate analysis, age (OR 1.07, CI95% [1.03-1.11], p < 0.001), FSO2mean (day 1-3)(OR 1.03 [1.00-1.06], p = 0.039), and right radial PaO2mean (day 1-3) (OR 1.03, CI95% [1.00-1.02], p = 0.023) were associated with in-ICU mortality. In a multicentric cohort of cardiogenic shock supported by VA ECMO, the median value for FSO2mean (day 1-7) was 70 [57; 79] %. PPOSTO2 monitoring was infrequent and revealed significant hyperoxemia. Higher FSO2mean (day 1-3) and right radial PaO2mean (day 1-3) were independently associated with in-ICU mortality.

Association between arterial oxygen and mortality across critically ill patients with hematologic malignancies: results from an international collaborative network.

Patients with hematological malignancies are at high risk for life-threatening complications. To date, little attention has been paid to the impact of hyperoxemia and excess oxygen use on mortality. The aim of this study was to investigate the association between partial pressure of arterial oxygen (PaO2) and 28-day mortality in critically ill patients with hematologic malignancies. Data from three international cohorts (Europe, Canada, Oceania) of patients who received respiratory support (noninvasive ventilation, high-flow nasal cannula, invasive mechanical ventilation) were obtained. We used mixed-effect Cox models to investigate the association between day one PaO2 or excess oxygen use (inspired fraction of oxygen ≥ 0.6 with PaO2 > 100mmHg) on day-28 mortality. 11,249 patients were included. On day one, 5716 patients (50.8%) had normoxemia (60 ≤ PaO2 ≤ 100mmHg), 1454 (12.9%) hypoxemia (PaO2 < 60mmHg), and 4079 patients (36.3%) hyperoxemia (PaO2 > 100mmHg). Excess oxygen was used in 2201 patients (20%). Crude day-28 mortality rate was 40.6%. There was a significant association between PaO2 and day-28 mortality with a U-shaped relationship (p < 0.001). Higher PaO2 levels (> 100mmHg) were associated with day-28 mortality with a dose-effect relationship. Subgroup analyses showed an association between hyperoxemia and mortality in patients admitted with neurological disorders; however, the opposite relationship was seen across those admitted with sepsis and neutropenia. Excess oxygen use was also associated with subsequent day-28 mortality (adjusted hazard ratio (aHR) [95% confidence interval (CI)]: 1.11[1.04-1.19]). This result persisted after propensity score analysis (matched HR associated with excess oxygen:1.31 [1.20-1.1.44]). In critically-ill patients with hematological malignancies, exposure to hyperoxemia and excess oxygen use were associated with increased mortality, with variable magnitude across subgroups. This might be a modifiable factor to improve mortality.

Wavelength-dependent activity screening of reduced titania for photocatalytic degradation of imidacloprid in batch and flow-mode

Water reuse is an emerging solution to decrease pressure on freshwater supplies and meet the increasing demand. This study explores the use of semiconductor photocatalysis for pesticide removal, focusing on extending TiO2 absorption to visible light and accelerating the screening of its wavelength-dependent photocatalytic activity. Grey to black TiO2 photocatalysts with lower direct and indirect band gap energies, up to 1.56 eV and 2.16 eV, respectively, were prepared by the chemical reduction of titania P25. The XPS analysis showed considerable oxygen vacancies, especially at the highest reduction temperature of 400 °C. The fraction of oxygen in the TiO2 lattice decreased from 90 % in the case of P25 to 53% for the photocatalyst obtained at 400 °C. The wavelength-dependent photocatalytic activity for the degradation of imidacloprid was screened in a batch photoreactor. TiO2 P25 presented higher photocatalytic activity than the reduced materials at 400 and 413 nm. At 443 nm, the material reduced at 400 °C exhibited the highest degradation efficiency of 16.8 % compared to 4.2 % as found for P25. Selected photocatalysts were then immobilized as thin films and tested in a 3D-printed flow photoreactor. Wavelength and photocatalyst’s impact on imidacloprid degradation in flow mode aligned with batch mode observations. The film activity remained stable after multiple reaction conditions and at least 150 min of operation. The proposed in-flow screening strategy is a promising approach to rapidly identify visible-light active catalysts, while minimizing the consumption of photocatalytic material and water contaminated with model pollutants.

Optimizing the economic viability of proton exchange membrane fuel cells operated with oxygen-enriched cathode air for residential hydrogen energy storage systems

The recovery and utilization of oxygen in residential hydrogen energy storage systems significantly impact economic factors. This study introduces an algorithm tailored to optimize oxygen concentration (fraction) across varied operational conditions, encompassing considerations for both efficiency (positive aspect) and lifetime (negative aspect). Initially, an enhanced air supply system (ASS), functioning with oxygen-enriched cathode air, is devised following the forefront scheme. Moreover, a dynamic model is formulated based on MATLAB/Simulink® software for the proton exchange membrane fuel cell (PEMFC) system. The model enables quantitative assessment of system gains in relation to various current densities and oxygen fractions, and its accuracy is partially validated through experimental data. Further, a model correlating stack lifetime to oxygen concentration (fraction) is established using experimental data obtained from other researchers. Finally, the optimal oxygen fractions are determined and managed, with a comparison of the effects before and after optimization. The optimized results indicate a 13% improvement in stack net power at rated operating conditions and a 24% improvement at peak operating conditions, and the system efficiency is improved by 24% and 43% at rated and peak operating conditions, respectively. In addition, the minimum value of system efficiency is observed to be 54%, and there is a notable attenuation of the concentration polarization phenomenon. This approach contributes to mitigating the challenge of lower system efficiency in normal PEMFCs for residential hydrogen energy storage systems (RHESSs) attributed to inadequate gas supply pressure.

Comparative effects of variable versus conventional volume-controlled one-lung ventilation on gas exchange and respiratory system mechanics in thoracic surgery patients: A randomized controlled clinical trial

BackgroundMechanical ventilation with variable tidal volumes (V-VCV) has the potential to improve lung function during general anesthesia. We tested the hypothesis that V-VCV compared to conventional volume-controlled ventilation (C-VCV) would improve intraoperative arterial oxygenation and respiratory system mechanics in patients undergoing thoracic surgery under one-lung ventilation (OLV). MethodsPatients were randomized to V-VCV (n = 39) or C-VCV (n = 39). During OLV tidal volume of 5 mL/kg predicted body weight (PBW) was used. Both groups were ventilated with a positive end-expiratory pressure (PEEP) of 5 cm H2O, inspiration to expiration ratio (I:E) of 1:1 (during OLV) and 1:2 during two-lung ventilation, the respiratory rate (RR) titrated to arterial pH, inspiratory peak-pressure ≤ 40 cm H2O and an inspiratory oxygen fraction of 1.0. ResultsSeventy-five out of 78 Patients completed the trial and were analyzed (dropouts were excluded). The partial pressure of arterial oxygen (PaO2) 20 min after the start of OLV did not differ among groups (V-VCV: 25.8 ± 14.6 kPa vs C-VCV: 27.2 ± 15.3 kPa; mean difference [95% CI]: 1.3 [−8.2, 5.5], P = 0.700). Furthermore, intraoperative gas exchange, intraoperative adverse events, need for rescue maneuvers due to desaturation and hypercapnia, incidence of postoperative pulmonary and extra-pulmonary complications, and hospital free days at day 30 after surgery did not differ between groups. ConclusionsIn thoracic surgery patients under OLV, V-VCV did not improve oxygenation or respiratory system mechanics compared to C-VCV.Ethical Committee: EK 420092019.Trial registration: at the German Clinical Trials Register: DRKS00022202 (16.06.2020).

Effects of Hypoxia Severity on Muscle Oxygenation Kinetics Using Statistical Parametric Mapping During Repeated Treadmill Sprints.

We examined the effects of increasing hypoxia severity on oxygenation kinetics in the vastus lateralis muscle during repeated treadmill sprints, using statistical parametric mapping (SPM). Ten physically active males completed 8 sprints of 5seconds each(recovery = 25s) on a motorized sprint treadmill in normoxia (sea level; inspired oxygen fraction = 0.21), moderate hypoxia (inspired oxygen fraction = 0.17), and severe hypoxia (SH; inspired oxygen fraction = 0.13). Continuous assessment of tissue saturation index (TSI) in the vastus lateralis muscle was conducted using near-infrared spectroscopy. Subsequently, TSI data were averaged for the sprint-recovery cycle of all sprints and compared between conditions. The SPM analysis revealed no discernible difference in TSI signal amplitude between conditions during the actual 5-second sprint phase. However, during the latter portion of the 25-second recovery phase, TSI values were lower in SH compared with both sea level (from 22 to 30s; P = .003) and moderate hypoxia (from 16 to 30s; P = .001). The mean distance covered at sea level (22.9 [1.0]m) was greater than for both moderate hypoxia (22.5 [1.2]m; P = .045) and SH (22.3 [1.4]m; P = .043). The application of SPM demonstrated that only SH reduced muscle oxygenation levels during the late portion of the passive (recovery) phase and not the active (sprint) phase during repeated treadmill sprints. These findings underscore the usefulness of SPM for assessing muscle oxygenation differences due to hypoxic exposure and the importance of the duration of the between-sprints recovery period.

High-flow nasal oxygen in infants and children for early respiratory management of pneumonia-induced acute hypoxemic respiratory failure: the CENTURI randomized clinical trial

ObjectiveTo compare the effectiveness of early high-flow nasal cannula (HFNC) and low-flow oxygen support (LFOS) in children under 5 years with acute hypoxemic respiratory failure (AHRF) due to severe community-acquired pneumonia in low-middle-income countries.MethodsAn open-label randomized clinical trial enrolled children aged 2–59 months with AHRF due to severe community-acquired pneumonia and randomized into HFNC and LFOS. In the LFOS group, the patient received cold wall oxygen humidified by bubbling through sterile water administered through simple nasal prongs at a fixed flow rate of 2 L/min. In the HFNC group, the patient received humidified, heated (37 °C), high-flow oxygen at a flow rate assigned based on weight range, with a titratable oxygen fraction. The primary outcome was treatment failure in 72 h (escalating the respiratory support method using any modality other than primary intervention).ResultsData was analyzed intention-to-treat (HFNC = 124; LFOS = 120). Median (IQR) age was 12 (6–20) and 11 (6–27) months, respectively. Treatment failure occurred in a significantly lower proportion in the HFNC group (7.3%, n = 9/124) as compared to the LFOS group (20%, n = 24/120) (relative risk = 0.36, 95% CI 0.18 to 0.75; p = 0.004; adjusted hazard ratio 0.34, 95% CI 0.16 to 0.73; p = 0.006). The intubation rate was significantly lower in the HFNC group (7.3%, n = 9/124 vs. 16.7%, n = 20/120; relative risk = 0.44, 95% CI 0.21 to 0.92, p = 0.023). There were no significant differences noted in other secondary outcomes. No mortality occurred.ConclusionHigh-flow nasal cannula oxygen therapy used as early respiratory support in children under 5 years with acute hypoxemic respiratory failure due to severe community-acquired pneumonia was associated with significantly lower treatment failure compared with standard low-flow oxygen support.Trial registration CTRI/2016/04/006788. Registered 01 April 2016, https://ctri.nic.in/Clinicaltrials/advsearch.php.

Anesthesia Management in Blalock-Taussig Shunt Procedure

Background: The systemic to pulmonary artery shunts are done as palliative procedures for complex cyanotic congenital heart diseases. Blalock-Taussig shunt (BT shunt) provide regulated blood flow to the lungs allowing growth of pulmonary arteries until the patient reaches proper age and body weight suitable for definitive corrective repair. BT shunts are first line management in patients with critical cyanotic conditions.Case: A 12-month-old boy diagnosed with PA-VSD subaortic, L-R shunt PDA and critical PDA stenosis experienced a recurrent spell condition with the lowest oxygen saturation 40%, underwent urgent BT shunt surgery. Oxygen saturation increases to 80-85% after shunt procedure.Discussion: Anesthesia management includes optimizing preoperative condition and patient hydration state, providing balance anesthesia during surgery, maintaining balance of pulmonary and systemic blood flow. High oxygen fraction can be given to maintain oxygen saturation before BT shunt anastomosis. Mechanical ventilation, heart rate with sinus rhythm, preload and contractility is maintained to obtain normal cardiac output. After BT shunt anastomosis, the oxygen fraction is reduced with a saturation target of 70–85%. Postoperative management includes anticoagulant administration and monitoring postoperative complications. The patient developed complications of increased pulmonary blood flow postoperatively and was admitted to the PICU for 3 days. The patient was discharged in good condition from ward on day 7.Conclusion: Understanding the physiology of heart defects and perioperative management determine the success of BT shunt surgery, reducing patient morbidity and mortality. Optimizing intraoperative and postoperative oxygen delivery with oxygenation targets PaO2 40-45 mmHg and saturation 70-80% reflects the balance of pulmonary blood flow and systemic blood flow (Qp:Qs=0.7-1.5:1).

Formulation of an Ideal Solid Oxide Fuel Cell

Principles of transport phenomena and chemical/ electrochemical reaction kinetics were employed to develop the formulation for the prediction of fuel (e.g., ) and oxidant (e.g., ) mole fraction profiles in the porous anode and cathode electrodes of an ideal solid oxide fuel cell (SOFC). The ideal SOFC is composed of the porous anode, , which is the cermet of metallic nickel and yttria-stabilized zirconia and the porous cathode, , which is the strontium-doped lanthanum manganite. A thin film of the yttria-stabilized zirconia is the solid electrolyte separating the cell electrodes. The cell anode-side fuel and cathode-side oxidant supply compartments are continuously stirred to maintain constant concentrations of fuel and oxidant in them. The relevant analytical formulation as well as the numerical data computed is presented. The current calculated data show a non-linear decrease, associated with the coupled effect of diffusion and consumption, in the mole fractions of hydrogen and oxygen in the porous electrodes with an increase in the distance from the reactant supply compartments towards the cell electrolyte separator.

Fitness Level- and Sex-Related Differences in Pulmonary Limitations to Maximal Exercise in Normoxia and Hypoxia.

Both maximal-intensity exercise and altitude exposure challenge the pulmonary system that may reach its maximal capacities. Expiratory flow limitation (EFL) and exercise-induced hypoxemia (EIH) are common in endurance-trained athletes. Furthermore, because of their smaller airways and lung size, women, independently of their fitness level, may be more prone to pulmonary limitations during maximal-intensity exercise, particularly when performed in hypoxic conditions. The objective of this study was to investigate the impact of sex and fitness level on pulmonary limitations during maximal exercise in normoxia and their consequences in acute hypoxia. Fifty-one participants were distributed across four different groups according to sex and fitness level. Participants visited the laboratory on three occasions to perform maximal incremental cycling tests in normoxia and hypoxia (inspired oxygen fraction = 0.14) and two hypoxic chemosensitivity tests. Pulmonary function and ventilatory capacities were evaluated at each visit. EIH was more prevalent (62.5% vs 22.2%, P = 0.004) and EFL less common (37.5% vs 70.4%, P = 0.019) in women than men. EIH prevalence was different ( P = 0.004) between groups of trained men (41.7%), control men (6.7%), trained women (50.0%), and control women (75.0%). All EIH men but only 40% of EIH women exhibited EFL. EFL individuals had higher slope ratio ( P = 0.029), higher ventilation (V̇ E ) ( P < 0.001), larger ΔVO 2max ( P = 0.019), and lower hypoxia-related V̇ E increase ( P < 0.001). Women reported a higher EIH prevalence than men, regardless of their fitness level, despite a lower EFL prevalence. EFL seems mainly due to the imbalance between ventilatory demands and capacities. It restricts ventilation, leading to a larger performance impairment during maximal exercise in hypoxic conditions.

Hypoxia in the pulmonary vein increases pulmonary vascular resistance independently of oxygen in the pulmonary artery.

Hypoxic pulmonary vasoconstriction (HPV) can be a challenging clinical problem. It is not fully elucidated where in the circulation the regulation of resistance takes place. It is often referred to as if it is in the arteries, but we hypothesized that it is in the venous side of the pulmonary circulation. In an open thorax model, pigs were treated with a veno-venous extra corporeal membrane oxygenator to either oxygenate or deoxygenate blood passing through the pulmonary vessels. At the same time the lungs were ventilated with extreme variations of inspired air from 5% to 100% oxygen, making it possible to make combinations of high and low oxygen content through the pulmonary circulation. A flow probe was inserted around the main pulmonary artery and catheters in the pulmonary artery and in the left atrium were used for pressure monitoring and blood tests. Under different combinations of oxygenation, pulmonary vascular resistance (PVR) was calculated. With unchanged level of oxygen in the pulmonary artery and reduced inspired oxygen fraction lowering oxygen tension from 29 to 6.7 kPa in the pulmonary vein, PVR was doubled. With more extreme hypoxia PVR suddenly decreased. Combinations with low oxygenation in the pulmonary artery did not systematic influence PVR if there was enough oxygen in the inspired air and in the pulmonary veins. The impact of hypoxia occurs from the alveolar level and forward with the blood flow. The experiments indicated that the regulation of PVR is mediated from the venous side.

Comparison of SpO2- with PaO2-Based Indices of Oxygenation in Children with Respiratory Failure

AbstractGiven the widespread availability of pulse oximetry and its potential to replace partial pressure of arterial oxygen (PaO2)-based indices of oxygenation, we aimed to study the correlation between pulse oximetry-based oxygen saturation (SpO2)- and PaO2-based indices of oxygenation namely, SpO2/FiO2 (SF) ratio with PaO2/FiO2 (PF) ratio and oxygen saturation index (OSI) with oxygenation index (OI) under varying physiological conditions, along with accuracy measures for SpO2-based indices. Inclusion criteria included children (1 month to 18 years) admitted to pediatric intensive care unit needing invasive ventilation for hypoxemic respiratory failure with SpO2 ≥ 80% and having an indwelling arterial catheter. A total of 1,237 sets of simultaneous PaO2, SpO2 readings, and ventilator parameters were recorded. There was a moderate correlation between SF and PF ratios (r s = 0.68, p &lt; 0.001) and strong correlation between OSI and OI (r s = 0.89, p &lt; 0.001). We obtained SF ratios of 271, 235, and 200 corresponding to PF ratios of 300, 200, and 100, respectively. SF ratio showed a good discrimination ability to identify moderate (area under the receiver operating characteristic curve [AUROC] = 0.901) and severe acute respiratory distress syndrome (ARDS; AUROC = 0.889) and fair discrimination ability for mild ARDS (AUROC = 0.770). OSI of 4.1, 6.4, and 11.1 corresponded to OI of 4, 8, and 16, respectively. OSI demonstrated an excellent discrimination ability for diagnosing mild (AUROC = 0.928), moderate (AUROC = 0.961), and severe ARDS (AUROC = 0.965). The correlation between SF/PF ratio and OSI/OI was the strongest in the lowest SpO2 range studied. SpO2-based indices of oxygenation could replace PaO2-based indices with reasonable accuracy for patients with SpO2 values ≥ 80%.

Inspired oxygen fraction thresholds to accurately predict surfactant administration in neonatal RDS is gestational age strata: A pragmatic, multi‐center study

AbstractObjectiveCurrent international guidelines on neonatal respiratory distress syndrome (RDS) recommend continuous positive airway pressure (CPAP) stabilization as primary treatment. Some guidelines recommend surfactant replacement for babies requiring FiO2 &gt; 0.3 regardless of gestational age (GA). We explore the accuracy of alternative inspired oxygen fraction (FiO2) thresholds as early predictors of surfactant replacement in babies stratified by GA.Study DesignPragmatic, observational study in 12 Italian and Spanish neonatal intensive care units. This is a secondary analysis of data from two cohorts of preterm babies with RDS, stratified by GA (25°− 276; 28°−306; 31°−336) and stabilized on CPAP. FiO2 was collected soon after stabilization and its accuracy to predict subsequent surfactant administration by a rigorously masked physician was assessed.ResultsWe enrolled 412 preterm infants. FiO2 was collected within 2 h of life of life. A cut off of FiO2 &gt; 0.30 failed to identify 50.3% of infants who were later given surfactant by a masked physician. A FiO2 = 0.29 threshold improved sensitivity values to 0.85, 0.79, and 0.61 for the three GA ranges while maintaining specificity of ≥85%. A FiO2 = 0.26 threshold gave sensitivity = 0.83 specificity = 0.79 with GA dependent differences (250−276 sensitivity = 0.90 specificity = 0.80; 280−306 sensitivity = 0.84 specificity = 0.78; 310−336 sensitivity = 0.73 specificity = 0.80).ConclusionsFiO2 is a GA dependent predictor of early surfactant administration. Its accuracy increases when used at lower levels than currently recommended by international guidelines (236 words).

Hypoxia matters: comparison of external and internal training load markers during an 8-week resistance training program in normoxia, normobaric hypoxia and hypobaric hypoxia

PurposeTo compare external and internal training load markers during resistance training (RT) in normoxia (N), intermittent hypobaric hypoxia (HH), and intermittent normobaric hypoxia (NH).MethodsThirty-three volunteers were assigned an 8-week RT program in either N (690 m, n = 10), HH (2320 m, n = 10), or NH (inspired fraction of oxygen = 15.9%; ~ 2320 m, n = 13). The RT program (3x/week) consisted of six exercises, with three sets of six to 12 repetitions at ~ 70% of one repetition maximum (1RM) with the first session of each week used for analysis. 1RM in back squat and bench press was used to evaluate muscle strength before and after the program. External load was assessed by the volume load relative to body mass (RVL, kg·kg−1). Internal load was assessed by the ratings of perceived exertion (RPE) and heart rate (HR).ResultsSmaller relative improvements were found for the back squat in the N group (11.5 ± 8.8%) when compared to the NH group (22.2 ± 8.2%, P = 0.01) and the HH group (22 ± 8.1%, P = 0.02). All groups showed similar RVL, HR responses and RPE across the program (P˃0.05). However, reduced HR recovery values, calculated as the difference between the highest HR value (HRpeak) and the resting heart rate after a two min rest, were seen in the N and NH groups across the program (P<\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$<$$\\end{document} 0.05).ConclusionIt seems that 8 weeks of intermittent RT in hypoxic environments could maximize time-efficiency when aiming to improve strength levels in back squat without evoking higher levels of physiological stress. Performing RT at hypobaric hypoxia may improve the cardiorespiratory response, which in turn could speed recovery.

Characterization of Peat Water Electrocoagulation Flocs from Sarawak Southern Region

Sarawak located in Borneo is endowed with the vast availability of peat water sources, particularly for the state southern region. Several investigations have shown that electrocoagulation treatment with aluminium electrodes is feasible to treat peat water in which the quality is comparable to the National Water Quality Standard (NWQS). Even though electrocoagulation treatment is feasible to treat peat water, the characteristics of peat water electrocoagulation flocs have not been reported. As such, this study aims to investigate the characteristics of the electrocoagulation flocs from peat water derived from the Sarawak southern region by using batch electrocoagulation treatment. The objectives of this study are to conduct an experimental study analysis of and identify the minerals on the electrocoagulation flocs along with operating energy cost analysis of peat water batch electrocoagulation treatment. Consequently, this study has found that reaction time and current density affect the production of flocs in which the amount of flocs increases with the increasing reaction time and current density. The flocs produced are found to consist of a large fraction of oxygen (O), carbon (C), iron (Fe), and aluminium (Al) along with a small fraction of potassium (K), magnesium (Mg), calcium (Ca) and Silicon (Si). The presence of Al observed in the flocs is due to the aluminium hydroxide generated during the electrocoagulation process. The total operating cost for peat electrocoagulation with a current density of 5A and reaction time of 20 minutes is about RM0.31 per m3. As a result, the electrocoagulation of peat water process is able to treat peat water as well as produce flocs in which earth elements and heavy metals could be recovered.