Oxygen Measurements Research Articles

Focal brain oxygen, blood flow, and intracranial pressure measurements in relation to optimal cerebral perfusion pressure.

Different paradigms for neurocritical care of traumatic brain injury (TBI) have emerged in conjunction with advanced neuromonitoring technologies and derived metrics. The priority for optimizing these metrics is not currently clear. The goal of this study was to determine whether achieving cerebral perfusion pressure (CPPopt) also improves other metrics like brain oxygenation and brain blood flow. The authors performed a retrospective analysis of high-frequency data from patients with TBI who were treated at a single center and who had partial pressure of brain oxygen (PbtO2) measurements and/or brain blood flow measurements, while also undergoing intracranial pressure (ICP) monitoring. CPPopt was not calculated or targeted during patient care, but was retrospectively computed, as was the difference between the observed CPP and CPPopt. A total of 22 patients with ICP, PbtO2, and/or brain blood flow monitoring were included in the analysis, and 245.7 days of measurements obtained every second were analyzed including 6,748,866 PbtO2 measurements, 3,296,405 blood flow measurements, and 10,264,770 ICP measurements. The data obtained every second were averaged by minute for analysis. In summative data, PbtO2 measurements peaked near CPPopt and were not improved above CPPopt. Blood flow measurements remained stable near CPPopt, decreased below it, and increased when CPP exceeded CPPopt. ICP decreased linearly with CPP without a specific relationship with CPPopt. In an inverse analysis, the percentage of CPP values at CPPopt, although significantly higher on the favorable side of contemporary treatment thresholds of PbtO2, ICP, and blood flow, was not found to be strongly correlated with the mean values of the physiological measurements obtained every minute (r = 0.27, r = 0.11, and r = 0.47 for ICP, PbtO2, and blood flow, respectively; p < 0.0001). Although CPPopt was not targeted in the patients in this study, CPPopt was a physiologically significant value based on concurrent measurements of PbtO2 and blood flow. In summative data, achievement of CPPopt was associated with optimized PbtO2 and blood flow. Conversely, the correlation between achievement of CPPopt and the mean measurement value was not strong, strengthening the significance of CPPopt. In individual patients, achieving CPPopt is not always associated with optimal PbtO2 or blood flow. Further research should explore these relationships in treatment paradigms that specifically target CPPopt. These data do not support the premise that targeting and achieving CPPopt obviates the need for concurrent PbtO2 and blood flow monitoring. Although these data suggest that targeting CPPopt may be an appropriate initial treatment strategy, they do not provide evidence that CPPopt should be targeted with highest priority.

Age and Handgrip Strength Induce Differences in Micro- and Macro-Vascular Responses

Purpose: Handgrip (HG) strength is a potent predictor of cardiovascular disease (CVD) and all-cause mortality. Advances in technology have provided novel assessments of peripheral microvascular and macrovascular health and function. These advances include measurements of skeletal muscle tissue oxygenation (StO2, %) with near-infrared spectroscopy (NIRS) during vascular occlusion tests (VOT) as well as carotid-femoral pulse-wave velocity (cfPWV), which is the current gold-standard to measure aortic stiffness. Although NIRS-VOT and cfPWV have been shown to change across the lifespan, it is unknown if these variables are sensitive to group differences as defined by HG strength. Therefore, our purpose was to examine mean differences in NIRS-VOT parameters and cfPWV between groups of low and high HG strength. We hypothesized that individuals with lower HG strength would exhibit lower vascular function. Methods: 67 adults were separated into age groups: young (19 – 40 yr), midlife (41 – 64 yr), and older (≥65 yr). Groups were divided into low and high strength at the median for HG strength, and quasi-balanced based on biological sex. This resulted in six participant groups (e.g., midlife low strength). The VOT included 3 min of rest, 5 min of ischemia, and 3 min of reperfusion to determine indices of reactive hyperemia. Indices included the initial (i.e., first 10 s) rate of re-saturation (upslope) and the maximal StO2 (StO2max) percent following ischemia. Aortic stiffness was defined as cfPWV using the time difference between the appearance of the carotid and femoral pulses. Separate 2×3 between factor (HG by Age Group) ANOVAs were conducted for each outcome. A p≤0.05 was considered significant, and data were presented as mean ± SD. Results: For upslope, there was a significant interaction (p=0.042, ηp2=0.078), and follow-up analyses revealed for young and midlife adults the high HG group exhibited greater upslopes than the low strength group (young: 2.24±0.9 vs. 1.64±0.7 and midlife: 2.21±0.9 vs. 1.59±0.7%∙s−1). There was no significant interaction (p=0.360) for StO2max, but there was a significant main effect (p&lt;0.001) of Age such that it progressively decreased across the lifespan (83.9 ± 2.0 &gt; 80.7 ± 2.3 &gt; 77.3 ± 2.8%). Similarly, cfPWV exhibited a significant main effect (p&lt;0.001; ηp2 =0.429) of Age indicating aortic stiffness worsened with age, independent of HG strength. Conclusions: These results indicated that upslope was sensitive to group differences in HG strength, but only in the young and midlife age groups. For StO2max and cfPWV, age differences appeared to elicit a stronger effect than HG strength. The current findings suggested that HG strength may be most reflective of a specific portion of the vascular tree, while the initial rate of re-saturation and StO2max may be influenced by different mechanisms associated with reactive hyperemia. Notably, the participants in this study were relatively healthy based on being free of any chronic disease. Future work is necessary to determine the predictive power of NIRS-VOT parameters for future onset of CVD. We would like to thank the American Physiology Society for support and the University of South Alabama for allowing us to use its facilities. We would also like to thank all of the participants who agreed to adhere to the protocol and procedures of this study. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

EFFECTS OF PROTEINURIA ON MUSCLE OXYGENATION AND MICROVASCULAR REACTIVITY IN PATIENTS WITH PRE-DIALYSIS CKD: A POST-HOC ANALYSIS

Objective: Vascular dysfunction is a hallmark of CKD. Previous studies showed an impaired microvascular reactivity in the skeletal muscles, which deteriorates in advanced CKD stages. This analysis aims to examine the impact of proteinuria on skeletal muscle oxygenation and microvascular reactivity at rest, during an occlusion-reperfusion maneuver, and during exercise in patients with pre-dialysis CKD. Design and method: 66 patients with CKD stage 2-4 were included in this post-hoc analysis; 24-h urine samples were used for evaluation of proteinuria. Continuous measurement of muscle oxygenation [tissue saturation index (TSI%)] via near-infrared-spectroscopy at rest, during occlusion-reperfusion and during a 3-min handgrip exercise (at 35% of maximal-voluntary-contraction). Results: The study groups were similar in terms of age (proteinuric vs nonproteinuric: 68.4±10.6 vs 67.2±10.8; p=0.676), eGFR (41.3±18.9 vs 46.3±14.8; p=0.248) and BMI (28.4±4.9 vs 28.1±4.8; p=0.803). Resting muscle oxygenation did not differ between study groups (proteinuric vs nonproteinuric: 63,35±4,09 vs 62,34±3,21; p=0.280). During occlusion, proteinuric CKD patients had marginally lower TSI occlusion magnitude (25,77±7,87 vs 29,95±10,34; p=0.074) but no difference in occlusion slope (-0,09±.,03 vs -,10±.,04; p=0.134). During reperfusion, the TSI reperfusion slopes were significantly lower in proteinuric CKD (slope to max 1,03±.,45 vs 1,39±.0,69; p=0.035 and 10-sec slope: 1,34±.,63 vs 1,92±.,75; p=0.002); hyperemic response was numerically lower in proteinuric CKD (7,13±.4,27 vs 8,89±.4,68; p=0.131). Finally, during exercise no differences were detected in the average muscle oxygenation between-group (10,76±6,05 vs 10,65±5,39; p=0.943). Conclusions: Although no differences in resting muscle oxygenation were detected, CKD patients with proteinuria showed more impaired skeletal muscle oxidative capacity (as suggested by lower TSI magnidute during occlusion), and miscrovascular reactivity during reperfusion.

Effects of Oxygen Therapy on Patients with a Chronic Wound: A Systematic Review and Meta-analysis.

To synthesize the effects of oxygen-based therapy on patients with a chronic wound. The authors searched PubMed, EMBASE, and Cochrane Central Register of Controlled Trials for relevant randomized controlled trials from database inception. Investigators measured risk of bias using the Cochrane Collaboration's Risk of Bias tool. The included randomized controlled trials focused on the effects (short- or long-term wound healing, amputation rate, percentage of reduction in ulcer size, and poststudy transcutaneous oxygen measurement [TcPO2]) of oxygen-based therapy (including hyperbaric oxygen therapy, topical oxygen therapy, and continuous diffusion of oxygen) on patients with a chronic wound. Researchers extracted information regarding participant characteristics and primary and secondary outcomes from the included studies. Pooled effects of 31 included studies showed that patients treated with oxygen had better short-term wound healing (risk ratio [RR], 1.544; 95% CI, 1.199 to 1.987), a higher percentage reduction in the ulcer area (standardized mean difference [SMD], 0.999; 95% CI, 0.439 to 1. 599), lower amputation rates (RR, 0.529; 95% CI, 0.325 to 0.862), shorter wound healing time (SMD, -0.705; 95% CI, -0.908 to -0.501), and higher poststudy TcPO2 (SMD, 2.128; 95% CI, 0.978 to 3.278) than those in the control group. For long-term wound healing, there was no statistically significant difference (RR, 1.227; 95% CI, 0.976 to 1.542). Oxygen-based therapy improves short-term parameters of wound healing in patients with chronic wounds.

Live Microscopy of Multicellular Spheroids with the Multimodal Near-Infrared Nanoparticles Reveals Differences in Oxygenation Gradients.

Assessment of hypoxia, nutrients, metabolite gradients, and other hallmarks of the tumor microenvironment within 3D multicellular spheroid and organoid models represents a challenging analytical task. Here, we report red/near-infrared (NIR) emitting cell staining with O2-sensitive nanoparticles, which enable measurements of spheroid oxygenation on a conventional fluorescence microscope. Nanosensor probes, termed "MMIR" (multimodal infrared), incorporate an NIR O2-sensitive metalloporphyrin (PtTPTBPF) and deep red aza-BODIPY reference dyes within a biocompatible polymer shell, allowing for oxygen gradient quantification via fluorescence ratio and phosphorescence lifetime readouts. We optimized staining techniques and evaluated the nanosensor probe characteristics and cytotoxicity. Subsequently, we applied nanosensors to the live spheroid models based on HCT116, DPSCs, and SKOV3 cells, at rest, and treated with drugs affecting cell respiration. We found that the growth medium viscosity, spheroid size, and formation method influenced spheroid oxygenation. Some spheroids produced from HCT116 and dental pulp stem cells exhibited "inverted" oxygenation gradients, with higher core oxygen levels than the periphery. This contrasted with the frequently encountered "normal" gradient of hypoxia toward the core caused by diffusion. Further microscopy analysis of spheroids with an "inverted" gradient demonstrated metabolic stratification of cells within spheroids: thus, autofluorescence FLIM of NAD(P)H indicated the formation of a glycolytic core and localization of OxPhos-active cells at the periphery. Collectively, we demonstrate a strong potential of NIR-emitting ratiometric nanosensors for advanced microscopy studies targeting live and quantitative real-time monitoring of cell metabolism and hypoxia in complex 3D tissue models.

A New Methodology for the Oxygen Measurement in Lung Tissue of an Aged Ferret Model Proves Hypoxia During COVID-19.

Oxygen as a key element has a high impact on cellular processes. Infection with a pathogen such as SARS-CoV-2 and following inflammation may lead to hypoxic conditions in tissue that impact cellular responses. To develop optimized translational in vitro models for a better understanding of physiologic and pathophysiologic oxygen conditions, it is a prerequisite to determine oxygen levels generated in vivo. Our study objective was the establishment of an invasive method for oxygen measurements using a luminescence-based microsensor to determine the dissolved oxygen in the lung tissue of ferrets as animal models for SARS-CoV-2 research. In analogy to humans, aged ferrets are more likely to show clinical signs after SARS-CoV-2 infection compared to young animals. To investigate oxygen levels during a respiratory viral infection, we intratracheally infected nine aged (3-year-old) ferrets with SARS-CoV-2. The aged SARS-CoV-2 infected ferrets showed mild to moderate clinical signs associated with prolonged viral RNA shedding until 14 days post infection (dpi). SARS-CoV-2 infected ferrets showed histopathologic lung lesion scores that significantly negatively correlated with oxygen levels in lung tissue. At 4 dpi, oxygen levels in lung tissue were significantly lower (mean %O2 of 3.89 ≙ ≈ 27.78 mmHg) compared to the negative control group (mean %O2 of 8.65 ≙ ≈ 61.4 mmHg). In summary, we succeeded in determining the pathophysiologic oxygen conditions in the lung tissue of aged SARS-CoV-2-infected ferrets. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/). .

Near-Infrared Spectroscopy (NIRS) in the Assessment of Cerebral Tissue Oxygenation (rSO2): Methodological Issues and Dilemmas

Introduction: Monitoring cerebral perfusion in patients with brain injury is a major clinical challenge. Monitoring cerebral oxygenation (rSO2) via NIRS was introduced in the early 1980s, and many clinicians believed it to be a valuable method for assessing cerebral perfusion and subsequent measures to optimize cerebral flow. The main problem with the use of NIRS is the presence of intermediate structures—the skin, skull, meninges, cerebrospinal fluid—and their influence on the test result. Therefore, it seems that NIRS assessment performed on a patient during brain death can give an idea of the magnitude of the influence of these intermediate structures on the monitoring result. Case presentation: We present a case study of cerebral oxygenation measurements in a patient undergoing a brain death diagnostic procedure. A clinical situation in which cerebral blood flow is stopped can give an idea of the specificity of this method, in particular of the influence of intermediate structures on the monitoring result. In this case, the result obtained using NIRS is increased by the patient’s oxygenation before the apnea test. The influence of chromophores in the tissues surrounding the CNS and reflections and scattering of the light wave spectrum have a very significant effect on the final result of cerebral saturation measurement. Discussion: The majority of observations in existing research describing changes in cerebral perfusion or its optimization may be burdened by the problem described here, i.e., by the significant influence of measured intermediate structure oxygenation. The specificity of NIRS in assessing cerebral perfusion requires careful analysis. The therapeutic implications of monitoring cerebral oxygenation with NIRS are of great importance, and based on the example presented and the literature provided, this method should be used with caution. It has been shown that in a patient with brain death, the result of NIRS oxygenation measurements depends on the structures surrounding the brain.

Data-Driven Modeling for the Prediction of Stack Gas Concentration in a Coal-Fired Power Plant in Türkiye

In this research, deep learning and machine learning methods were employed to forecast the levels of stack gas concentrations in a coal-fired power plant situated in Türkiye. Real-time data collected from continuous emission monitoring systems (CEMS) serves as the basis for the predictions. The dataset includes measurements of carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxides (NOx), oxygen (O2), and dust levels, along with temperatures recorded. For this analysis, deep learning methods such as multi-layer perceptron network (MLP) and long short-term memory (LSTM) models were used, while machine learning techniques included light gradient boosted machine (LightGBM) and stochastic gradient descent (SGD) models were applied. The accuracy of the models was determined by analysing their performance using mean absolute error (MAE), root means square error (RMSE), and R-squared values. Based on the results, LightGBM achieved the highest R-squared (0.85) for O2 predictions, highlighting its variance-capturing ability. LSTM excelled in NOx (R-squared 0.87) and SO2 (R-squared 0.85) prediction, while showing the top R-squared (0.67) for CO. Both LSTM and LGBM achieved R-squared values of 0.78 for dust levels, indicating strong variance explanation. Conclusively, our findings highlight LSTM as the most effective approach for stack gas concentration forecasting, closely followed by the good performance of LightGBM. The importance of these results lies in their potential to effectively manage emissions in coal-fired power plants, thereby improving both environmental and operational aspects.Graphical

Multimodal imaging device to comprehensively assess infection, oxygenation, and wound analytics-A pilot study.

Wound analytics, infection detection, and oxygenation measurement are the three critical prerequisites for appropriate wound care. Although devices that rapidly detect the above-mentioned parameters independently exist, there is no single point-of-care device that is enabled with all the three functionalities. Through this study, we are introducing and evaluating the performance of Illuminate Pro Max-a novel, rapid, hand-held non-contact, point-of-care multimodal imaging device that is equipped to measure the three wound assessment parameters. Here, a total of 60 diabetic foot ulcer patients were imaged using Illuminate Pro Max to detect bioburden and measure StO2 levels and wound dimensions (size and depth). The results were further evaluated against the current gold standard technique for each parameter, that is, culture test to detect bioburden, a transcutaneous oxygen pressure (TcPO2) measuring device-Perimed Periflux 5000 to measure oxygenation, and paper ruler to measure wound size. Culture tests reported 42 samples as infection-positive and 18 samples as infection-negative. On comparing with the culture report, the device showed 88% sensitivity and 86% PPV in detecting the bioburden. Wound dimensions (length and width) were comparable with the paper scale measurements. Wound depth was also reported by the device. The StO2 map generated by the device depicted the tissue oxygenation levels in various regions of the wound. In conclusion, this novel, comprehensive point-of-care multispectral imaging device can be an effective tool for rapid wound assessment which can help in prompt treatment.

Maximizing the Reliability and Precision of Measures of Prefrontal Cortical Oxygenation Using Frequency-Domain Near-Infrared Spectroscopy.

Frequency-domain near-infrared spectroscopy (FD-NIRS) has been used for non-invasive assessment of cortical oxygenation since the late 1990s. However, there is limited research demonstrating clinical validity and general reproducibility. To address this limitation, recording duration for adequate validity and within- and between-day reproducibility of prefrontal cortical oxygenation was evaluated. To assess validity, a reverse analysis of 10-min-long measurements (n = 52) at different recording durations (1-10-min) was quantified via coefficients of variation and Bland-Altman plots. To assess within- and between-day within-subject reproducibility, participants (n = 15) completed 2-min measurements twice a day (morning/afternoon) for five consecutive days. While 1-min recordings demonstrated sufficient validity for the assessment of oxygen saturation (StO2) and total hemoglobin concentration (THb), recordings ≥4 min revealed greater clinical utility for oxy- (HbO) and deoxyhemoglobin (HHb) concentration. Females had lower StO2, THb, HbO, and HHb values than males, but variability was approximately equal between sexes. Intraclass correlation coefficients ranged from 0.50-0.96. The minimal detectable change for StO2 was 1.15% (95% CI: 0.336-1.96%) and 3.12 µM for THb (95% CI: 0.915-5.33 µM) for females and 2.75% (95%CI: 0.807-4.70%) for StO2 and 5.51 µM (95%CI: 1.62-9.42 µM) for THb in males. Overall, FD-NIRS demonstrated good levels of between-day reliability. These findings support the application of FD-NIRS in field-based settings and indicate a recording duration of 1 min allows for valid measures; however, data recordings of ≥4 min are recommended when feasible.

In Situ Performance Monitoring of Electrochemical Oxygen and Hydrogen Peroxide Sensors in an Additively Manufactured Modular Microreactor.

Miniaturized and microstructured reactors in process engineering are essential for a more decentralized, flexible, sustainable, and resilient chemical production. Modern, additive manufacturing methods for metals enable complex reactor-geometries, increased functionality, and faster design iterations, a clear advantage over classical subtractive machining and polymer-based approaches. Integrated microsensors allow online, in situ process monitoring to optimize processes like the direct synthesis of hydrogen peroxide. We developed a modular tube-in-tube membrane reactor fabricated from stainless steel via 3D printing by laser powder bed fusion of metals (PBF-LB/M). The reactor concept enables the spatially separated dosage and resaturation of two gaseous reactants across a membrane into a liquid process medium. Uniquely, we integrated platinum-based electrochemical sensors for the online detection of analytes to reveal the dynamics inside the reactor. An advanced chronoamperometric protocol combined the simultaneous concentration measurement of hydrogen peroxide and oxygen with monitoring of the sensor performance and self-calibration in long-term use. We demonstrated the highly linear and sensitive monitoring of hydrogen peroxide and dissolved oxygen entering the liquid phase through the membrane. Our measurements delivered important real-time insights into the dynamics of the concentrations in the reactor, highlighting the power of electrochemical sensors applied in process engineering. We demonstrated the stable continuous measurement over 1 week and estimated the sensor lifetime for months in the acidic process medium. Our approach combines electrochemical sensors for process monitoring with advanced, additively manufactured stainless steel membrane microreactors, supporting the power of sensor-equipped microreactors as contributors to the paradigm change in process engineering and toward a greener chemistry.

Atmospheric oxygen as a tracer for fossil fuel carbon dioxide: a sensitivity study in the UK

Abstract. We investigate the use of atmospheric oxygen (O2) and carbon dioxide (CO2) measurements for the estimation of the fossil fuel component of atmospheric CO2 in the UK. Atmospheric potential oxygen (APO) – a tracer that combines O2 and CO2, minimizing the influence of terrestrial biosphere fluxes – is simulated at three sites in the UK, two of which make APO measurements. We present a set of model experiments that estimate the sensitivity of APO simulations to key inputs: fluxes from the ocean, fossil fuel flux magnitude and distribution, the APO baseline, and the exchange ratio of O2 to CO2 fluxes from fossil fuel combustion and the terrestrial biosphere. To estimate the influence of uncertainties in ocean fluxes, we compare three ocean O2 flux estimates from the NEMO–ERSEM, the ECCO–Darwin ocean model, and the Jena CarboScope (JC) APO inversion. The sensitivity of APO to fossil fuel emission magnitudes and to terrestrial biosphere and fossil fuel exchange ratios is investigated through Monte Carlo sampling within literature uncertainty ranges and by comparing different inventory estimates. We focus our model–data analysis on the year 2015 as ocean fluxes are not available for later years. As APO measurements are only available for one UK site at this time, our analysis focuses on the Weybourne station. Model–data comparisons for two additional UK sites (Heathfield and Ridge Hill) in 2021, using ocean flux climatologies, are presented in the Supplement. Of the factors that could potentially compromise simulated APO-derived fossil fuel CO2 (ffCO2) estimates, we find that the ocean O2 flux estimate has the largest overall influence at the three sites in the UK. At times, this influence is comparable in magnitude to the contribution of simulated fossil fuel CO2 to simulated APO. We find that simulations using different ocean fluxes differ from each other substantially. No single model estimate, or a model estimate that assumed zero ocean flux, provided a significantly closer fit than any other. Furthermore, the uncertainty in the ocean contribution to APO could lead to uncertainty in defining an appropriate regional background from the data. Our findings suggest that the contribution of non-terrestrial sources needs to be better accounted for in model simulations of APO in the UK to reduce the potential influence on inferred fossil fuel CO2 using APO.

Tuberculosis miliar en paciente inmunocompetente: Reporte de caso

Milar Tuberculosis (TB) is a presentation with a fatal outcome if it is not diagnosed or treated on time; although certain conditions are required to develop this presentation. In this In this article, the case of a 48-year-old man with no pathological history is studied, who started the disease with a time of six months with an initial diffuse gastrointestinal pain and later one month before admission presented progressive respiratory symptoms; he was admitted for emergencies where bilateral diffuse miliary compromise was evident in the chest computed tomography; upon admission, he was administered oxygen and support measures, an HIV test was obtained which was negative, and positive results were obtained in the sputum smear microscopy. His clinical evolution was stationary until the administration of antituberculosis therapy, observing slight clinical improvement, likewise, low doses of corticosteroids were administered after which a favorable evolution was demonstrated and he was discharged.

Sensing and Imaging Molecular Oxygen in Mammals with Spin Lattice Relaxation Electron Paramagnetic Resonance.

Molecular oxygen and its thermodynamic transformation drive nearly all life processes. Quantitative measurement and imaging of oxygen in living systems is of fundamental importance for the study of life processes and their aberrations-disease- many of which are affected by hypoxia, or low levels of oxygen. Cancer is among the disease processes profoundly affected by hypoxia. Electron paramagnetic resonance has been shown to provide remarkably accurate images of normal and cancerous tissue. In this review, we emphasize the reactivity of molecular oxygen particularly highlighting the metabolic processes of living systems to store free energy in the reactants. The history of hypoxic resistance of living systems to cytotoxic therapy, particularly radiation therapy is also reviewed. The measurement and imaging of molecular oxygen with pulse spin lattice relaxation (SLR) electron paramagnetic resonance (EPR) is reviewed briefly. This emphasizes the advantages of the spin lattice relaxation based measurement paradigm to reduce the sensitivity of the measurement to the presence of the oxygen sensing probe itself. The involvement of a novel small mammal external beam radiation delivery system is described. This enables an experimental paradigm based on control by radiation of the last resistant clonogen. This is much more specific for tumor cure than growth delay assays which primarily reflects control of tumor cells most sensitive to therapy.

Vessel-specific quantification of cerebral venous oxygenation with velocity-encoding preparation and rapid acquisition.

Non-invasive measurement of cerebral venous oxygenation (Yv) is of critical importance in brain diseases. The present work proposed a fast method to quantify regional Yv map for both large and small veins. A new sequence was developed, referred to as TRU-VERA (T2 relaxation under velocity encoding and rapid acquisition, which isolates blood spins from static tissue with velocity-encoding preparation, modulates the T2 weighting of venous signal with T2-preparation and utilizes a bSSFP readout to achieve fast acquisition with high resolution. The sequence was first optimized to achieve best sensitivity for both large and small veins, and then validated with TRUST (T2 relaxation under spin tagging), TRUPC (T2 relaxation under phase contrast), and accelerated TRUPC MRI. Regional difference of Yv was evaluated, and test-retest reproducibility was examined. Optimal Venc was determined to be 3 cm/s, while recovery time and balanced SSFP flip angle within reasonable range had minimal effect on SNR efficiency. Venous T2 measured with TRU-VERA was highly correlated with T2 from TRUST (R2 = 0.90), and a conversion equation was established for further calibration to Yv. TRU-VERA sequences showed consistent Yv estimation with TRUPC (R2 = 0.64) and accelerated TRUPC (R2 = 0.79). Coefficient of variation was 0.84% for large veins and 2.49% for small veins, suggesting an excellent test-retest reproducibility. The proposed TRU-VERA sequence is a promising method for vessel-specific oxygenation assessment.

Transcutaneous oximetry of angiosomes of maxillary and facial arteries

Aim. To qualitatively predict and control the quality of periodontal diseases treatment, to determine changes in the transcutaneous pressure of oxygen and carbon dioxide in angiosomes of maxillary and facial arteries in healthy adults. Materials and methods. 17 healthy people participated in this study. There were 10 (58 %) men aged 24 (22–27), weight 66 (62–80) kg and height 175 (169–182) cm and 7 (42 %) women, whose average age was 23 (20–26) years old, weight 58 (47–72) kg, height 165 (160–178) cm. Results. The highest values of tissue perfusion with oxygen were observed in the angiosomes of the upper jaw compared to the angiosomes of the lower jaw, where this indicator ranged from 105 to 153 mm Hg. On the lower jaw, the maximum value of the regional perfusion index (RPI) of 1.70 ± 0.04 was observed at the point of measurement where a. mentalis exits through the homonymous chin orifice, anastomosing with the branches of a. facialis. The highest values of tissue perfusion with carbon dioxide were observed in angiosomes of the lower jaw (28–36 mm Hg). In general, non-invasive measurements of oxygen and carbon dioxide pressure in tissues allow more accurate and direct visualization and control of microcirculation in the tissues of the corresponding angiosomes. Conclusions. The index of regional perfusion on the upper jaw is normally in the range of 2.2 to 2.6 (р &lt; 0.0001). In the angiosome of the lower jaw, the RPI value is within 1.3–1.7, respectively (p &lt; 0.0001). The tension of carbon dioxide in the tissues of the upper and lower jaw averages 31–34 mm Hg (р &lt; 0.05), reaches its maximum in the zones of the lowest oxygen perfusion.

Wearable fiber-free optical sensor for continuous monitoring of neonatal cerebral blood flow and oxygenation.

Unstable cerebral hemodynamics places preterm infants at high risk of brain injury. We adapted an innovative, fiber-free, wearable diffuse speckle contrast flow-oximetry (DSCFO) device for continuous monitoring of both cerebral blood flow (CBF) and oxygenation in neonatal piglets and preterm infants. DSCFO uses two small laser diodes as focused-point and a tiny CMOS camera as a high-density two-dimensional detector to detect spontaneous spatial fluctuation of diffuse laser speckles for CBF measurement, and light intensity attenuations for cerebral oxygenation measurement. The DSCFO was first validated against the established diffuse correlation spectroscopy (DCS) in neonatal piglets and then utilized for continuous CBF and oxygenation monitoring in preterm infants during intermittent hypoxemia (IH) events. Significant correlations between the DSCFO and DCS measurements of CBF variations in neonatal piglets were observed. IH events induced fluctuations in CBF, cerebral oxygenation, and peripheral cardiorespiratory vitals in preterm infants. However, no consistent correlation patterns were observed among peripheral and cerebral monitoring parameters. This pilot study demonstrated the feasibility of DSCFO technology to serve as a low-cost wearable sensor for continuous monitoring of multiple cerebral hemodynamic parameters. The results suggested the importance of multi-parameter measurements for understanding deep insights of peripheral and cerebral regulations. The innovative DSCFO technology may serve as a low-cost wearable sensor for continuous bedside monitoring of multiple cerebral hemodynamic parameters in neonatal intensive care units. Concurrent DSCFO and DCS measurements of CBF variations in neonatal piglet models generated consistent results. No consistent correlation patterns were observed among peripheral and cerebral monitoring parameters in preterm neonates, suggesting the importance of multi-parameter measurements for understanding deep insights of peripheral and cerebral regulations during IH events. Integrating and correlating multiple cerebral functional parameters with clinical outcomes may identify biomarkers for prediction and management of IH associated brain injury.

Time to anoxia: Observations and predictions of oxygen drawdown following coastal flood events

The coastal terrestrial-aquatic interface (TAI) is a highly dynamic system characterized by strong physical, chemical, and biological gradients. In particular, shifting soil redox conditions and consumption of terminal electron acceptors, due in part to dynamic hydrologic conditions, is a strong driver of carbon availability and transformations across TAIs. However, while redox dynamics are well described, our ability to quantitatively forecast rates ofoxic to anoxic shifts in soils with different characteristics and inundation regimes is limited. We integrated field measurements, laboratory incubations, and model simulations to improve mechanistic understanding of oxygen consumption dynamics in coastal soils. Continuous in situ monitoring unexpectedly revealed that flooding caused temporary spikes in subsurface dissolved oxygen followed by rapid consumption in the wetlands. To further investigate these mechanisms in a controlled setting, we performed laboratory incubations using surface and subsurface soils from a TAI gradient (defined here as upland forest to transitional forest to wetland) in Western Lake Erie to measure oxygen consumption rates in TAI soils during flood events. In our experiments, wetland soils reached anoxia the fastest, in ∼ 9 h on average, whereas upland soils turned anoxic in ∼ 18 h. Subsurface upland soils did not turn anoxic even after two weeks of saturation in the lab, and their oxygen consumption patterns suggested carbon and/or nutrient limitation. These results are consistent with in-situ groundwater redox and oxygen measurements in the field, where wetland soils exhibited the highest rates of oxygen consumption along the TAI. Model simulations of oxygen consumption suggested that oxygen consumption had stronger abiotic controls in wetland soils but stronger biotic controls in upland soils, providing a useful framework for future incubation experiments. Microbial activity is a strong driver of oxygen consumption in TAI soils, although it is constrained by the availability of dissolved carbon in subsurface soils.

Anesthetic Oxygen Use and Sex Are Critical Factors in the FLASH Sparing Effect

IntroductionUltra-high dose-rate (UHDR) radiation has been reported to spare normal tissue compared to conventional dose-rate (CDR) radiation. However, important work remains to be done to improve the reproducibility of the FLASH effect. A better understanding of the biological factors that modulate the FLASH effect may shed light on the mechanism of FLASH sparing. Here, we evaluate whether sex and/or use of 100% oxygen as carrier gas during irradiation contribute to the variability of the FLASH effect. MethodsC57BL/6 mice (24 male, 24 female) were anesthetized using isoflurane mixed with either room air or 100% oxygen. Subsequently, the mice received 27 Gy of either 9 MeV electron UHDR or CDR to a 1.6 cm2 diameter area of the right leg skin using the Mobetron linear accelerator. The primary post-radiation endpoint was time to full thickness skin ulceration. In a separate cohort of mice (4 male, 4 female) skin oxygenation was measured using PdG4 Oxyphor under identical anesthesia conditions. ResultsIn the UHDR group, time to ulceration was significantly shorter in mice that received 100% oxygen compared to room air, and amongst them female mice ulcerated sooner compared to males. However, no significant difference was observed between male and female UHDR mice that received room air. Oxygen measurements showed significantly higher tissue oxygenation using 100% oxygen as the anesthesia carrier gas compared to room air, and female mice showed higher levels of tissue oxygenation compared to males under 100% oxygen. ConclusionThe FLASH sparing effect is significantly reduced using oxygen during anesthesia compared to room air. The FLASH sparing was significantly lower in female mice compared to males. Both tissue oxygenation and sex are likely sources of variability in UHDR studies. These results suggest an oxygen-based mechanism for FLASH, as well as a key role for sex in the FLASH skin sparing effect.

Characteristics of Phytoplankton Productivity in Three Typical Lake Zones of Taihu, China

In lake aquatic ecosystems, which form the material and energy base of lakes, primary production is critical. The present study addresses the characteristics of primary phytoplankton productivity and its relationship with environmental physicochemical factors in three typical zones (algae-type, transition, and grass-type) of the eutrophic Lake Taihu. Seasonal sampling was conducted, and black–white bottle oxygen measurement was used to determine the primary productivity in different water layers in the lake. The results show obvious temporal and spatial differences in the physicochemical factors and phytoplankton productivity in Lake Taihu. The water column productivity and respiration conformed to the following seasonal descending order, summer &gt; fall &gt; spring &gt; winter, and the following regional descending order, algae-type zone &gt; transition zone &gt; grass-type zone. The seasonal proportions of primary productivity were approximately 40% in the summer, 25% in the fall, 20% in the spring, and less than 15% in the winter. The highest values of water layer productivity and respiration were mainly at a depth of 0.2 m and decreased with the water depth. The percentage of productivity at different water layers was 23% (0 m), 31% (0.2 m), 23% (0.4 m), 11% (0.6 m), 7% (0.8 m), and 5% (1 m). The optical compensation depth for Lake Taihu was about 0.8 times the transparency (SD). Spearman correlation indicated that the temperature (T) and water depth (D) had an obvious impact on productivity in all three lake zones. Multiple stepwise regression suggested that T, D, SD, and chlorophyll-a (Chl-a) can be used to estimate productivity in different seasons/regions. The main influencing factors on phytoplankton productivity are T, D, Chl-a, and SD in the algae-type and transition zones and T, D, and total suspended solids (TSSs) in the grass-type zone.