Less Oxygen, Later Intubation and Reduced Respiratory Pressures for ELBW Infants from 1997 to 2011.

INTRODUCTION Evidence concerning delivery room management in extremely low birth weight infants (ELBW) has grown substantially within the last 20 years, leading to several guidelines and recommendations. However, it is unknown in which extent local treatment strategies have changed and if they reflect current recommendations. METHODS A detailed questionnaire about treatment strategies for ELBW infants was sent to all German neonatal intensive care units (NICUs) treating ELBW infants in 1997. A follow-up survey was conducted in 2011 and sent to all NICUs in Germany, Austria and Switzerland. RESULTS on delivery room management were compared to the first survey. RESULTS In 1997 and 2011, 63.6 and 66.2% of the approached hospitals responded. In 2011 similar results were observed between university and non-university hospitals as well as NICUs of different size. Differences between Germany, Austria and Switzerland were minimal. Changes over time were a lower initially applied fraction of inspired oxygen (FiO2) and peak inspiratory pressure (PiP) in 2011 compared to 1997. A longer time of apnea was tolerated before tracheal intubation is performed; the time of apnea was less frequently a sole criterion for intubation and surfactant was applied at lower FiO2 in 2011. The time of no thorax excursions and transport of the infant were considered an indication for intubation in 30.2 and 22.5%, and did not change in the observation period. CONCLUSION Treatment strategies for delivery room management in ELBW infants changed significantly between 1997 and 2011 and largely reflect current recommendations.

Inhalation anesthesia of rats: influence of the fraction of inspired oxygen on limb ischemia/reperfusion injury

Inhalation anesthesia with isoflurane is a well-established and safe method used in small laboratory animals. In most cases oxygen is used as a carrier gas for isoflurane, but room air or mixtures of oxygen with air or nitrous oxide are also being used. Anesthesia is therefore administered using different fractions of inspired oxygen (FiO2), and this may have consequences for the outcome of experiments. The aim of the present study was to investigate the influence of FiO2 on rat hind limb ischemia/reperfusion injury and to refine the used inhalation anesthesia. Male Wistar rats were subjected to 3.5 h of ischemia and 2 h of reperfusion, and divided into three groups according to FiO2 in the O2/air/isoflurane anesthesia gas mixture: 40%, 60%, and 100% O2. Normal, healthy rats were used as controls. Muscle edema and creatine kinase MM, a marker for myocyte necrosis, were significantly increased with 40% FiO2 as compared with 100% FiO2 (P<0.05). Partial pressure of oxygen, oxygen saturation, and oxyhemoglobin were significantly higher in the 100% O2 group as compared with 40% O2. No significant differences were detected for other parameters, such as the oxidative stress markers malondialdehyde and superoxide dismutase. We conclude that a refined inhalation anesthesia setting using 40% FiO2, reflecting more or less the clinical situation, leads to a more severe and more physiologically relevant reperfusion injury than higher FiO2. Oxidative stress did not correlate with FiO2 and seemed to have no influence on reperfusion injury.

Oxygen isotopes of lake marl at Gerzensee and Leysin (Switzerland), covering the Younger Dryas and two minor oscillations, and their correlation to the GRIP ice core

The ratio of oxygen isotopes is a temperature proxy both in precipitation and in the calcite of lacustrine sediments. The very similar oxygen-isotope records from Greenland ice cores and European lake sediments during the Last Glacial Termination suggest that the drastic climatic changes occurred quasi-simultaneously on an extra-regional, probably hemispheric scale. In order to study temporal relations of the different parameters recorded in lake sediments, for example biotic response times to rapid climatic changes, a precise chronology is required. In unlaminated lake sediments there is not yet available a method to provide a high-resolution chronology, especially for periods with radiocarbon plateaux. Alternatively, an indirect time scale can be constructed by linking the lake stratigraphy with other well-dated climate records. New oxygen-isotope records from Gerzensee and Leysin, with an estimated sampling resolution of between 15 and 40 years, match the Greenlandic isotope record in many details. Under the assumption that the main variations in temperature and thus in oxygen isotopes occurred about simultaneously in Greenland and Switzerland, we have assigned a time scale to the lake sediments of Gerzensee and Leysin by wiggle-matching their stable-isotope records with those of Greenland ice cores, which are among the best dated climatic archives. We estimate a precision of 20 to 100 years during the Last Glacial Termination.

Dating prograde fluid pulses during subduction by in situ U–Pb and oxygen isotope analysis

Keywords High-pressure fluids · Whiteschists · U–Pb dating · Oxygen isotopes · Ion microprobe · Metasomatism Introduction The subduction of crustal material to mantle depths and its chemical modification during burial and exhumation contribute to element recycling in the mantle and the formation of new crust through arc magmatism. Crustal rocks that Abstract The Dora-Maira whiteschists derive from metasomatically altered granites that experienced ultrahighpressure metamorphism at ~750 °C and 40 kbar during the Alpine orogeny. In order to investigate the P–T–time– fluid evolution of the whiteschists, we obtained U–Pb ages from zircon and monazite and combined those with trace element composition and oxygen isotopes of the accessory minerals and coexisting garnet. Zircon cores are the only remnants of the granitic protolith and still preserve a Permian age, magmatic trace element compositions and δ18O of ~10 ‰. Thermodynamic modelling of Si-rich and Si-poor whiteschist compositions shows that there are two main fluid pulses during prograde subduction between 20 and 40 kbar. In Si-poor samples, the breakdown of chlorite to garnet + fluid occurs at ~22 kbar. A first zircon rim directly overgrowing the cores has inclusions of prograde phlogopite and HREE-enriched patterns indicating zircon growth at the onset of garnet formation. A second main fluid pulse is documented close to peak metamorphic conditions in both Si-rich and Si-poor whiteschist when talc + kyanite react to garnet + coesite + fluid. A second metamorphic overgrowth on zircon with HREE depletion was observed in the Si-poor whiteschists, whereas a single metamorphic overgrowth capturing phengite and talc inclusions was observed in the Si-rich whiteschists. Garnet rims, zircon rims and monazite are in chemical and isotopic equilibrium for oxygen, demonstrating that they all formed at peak metamorphism at 35 Ma as constrained by the age of monazite (34.7 ± 0.4 Ma) and zircon rims (35.1 ± 0.8 Ma). The prograde zircon rim in Si-poor whiteschists has an age that is within error indistinguishable from the age of peak metamorphic conditions, consistent with a minimum rate of subduction of 2 cm/year for the Dora-Maira unit. Oxygen isotope values for zircon rims, monazite and garnet are equal within error at 6.4 ± 0.4 ‰, which is in line with closed-system equilibrium fractionation during prograde to peak temperatures. The resulting equilibrium Δ18Ozircon-monazite at 700 ± 20 °C is 0.1 ± 0.7 ‰. The in situ oxygen isotope data argue against an externally derived input of fluids into the whiteschists. Instead, fluidassisted zircon and monazite recrystallisation can be linked to internal dehydration reactions during prograde subduction. We propose that the major metasomatic event affecting the granite protolith was related to hydrothermal seafloor alteration post-dating Jurassic rifting, well before the onset of Alpine subduction.

Can IBEX detect interstellar neutral helium or oxygen from anti-ram directions?

To better constrain the parameters of the interstellar neutral flow, we searched the Interstellar Boundary EXplorer (IBEX)-Lo database for helium and oxygen from the interstellar medium in the anti-ram direction in the three years (2009-2011) with the lowest background rates. We found that IBEX-Lo cannot observe interstellar helium from the anti-ram direction because the helium energy is too low for indirect detection by sputtering off the IBEX-Lo conversion surface. Our results show that this sputtering process has a low energy threshold between 25 and 30 eV, whereas the energy of the incident helium is only 10 eV for these observations. Interstellar oxygen, on the other hand, could in principle be detected in the anti-ram hemisphere, but the expected magnitude of the signal is close to the detection limit imposed by counting statistics and by the magnetospheric foreground.

Stable carbon and oxygen isotopes in tree rings show physiological responses of Pericopsis elata to precipitation in the Congo Basin

In equatorial regions, where tree rings are less distinct or even absent, the response of forests to high-frequency climate variability is poorly understood. We measured stable carbon and oxygen isotopes in anatomically distinct, annual growth rings of four Pericopsis elata trees from a plantation in the Congo Basin, to assess their sensitivity to recorded changes in precipitation over the last 50 y. Our results suggest that oxygen isotopes have high common signal strength (EPS = 0.74), and respond to multi-annual precipitation variability at the regional scale, with low δ18O values (28–29‰) during wetter conditions (1960–1970). Conversely, δ13C are mostly related to growth variation, which in a light-demanding species are driven by competition for light. Differences in δ13C values between fast- and slow-growing trees (c. 2‰), result in low common signal strength (EPS = 0.37) and are driven by micro-site conditions rather than by climate. This study highlights the potential for understanding the causes of growth variation in P. elata as well as past hydroclimatic changes, in a climatically complex region characterized by a bimodal distribution in precipitation.

Impact of reactive oxygen species (ROS) on the control of parasite loads and inflammation in Leishmania amazonensis infection

Background: Reactive oxygen species (ROS) protect the host against a large number of pathogenic microorganisms. ROS have different effects on parasites of the genus Leishmania: some parasites are susceptible to their action, while others seem to be resistant. The role of ROS in L. amazonensis infection in vivo has not been addressed to date. Methods: In this study, C57BL/6 wild-type mice (WT) and mice genetically deficient in ROS production by phagocytes (gp91phox−/− ) were infected with metacyclic promastigotes of L. amazonensis to address the effect of ROS in parasite control. Inflammatory cytokines, parasite loads and myeloperoxidase (MPO) activity were evaluated. In parallel, in vitro infection of peritoneal macrophages was assessed to determine parasite killing, cytokine, NO and ROS production. Results: In vitro results show induction of ROS production by infected peritoneal macrophages, but no effect in parasite killing. Also, ROS do not seem to be important to parasite killing in vivo, but they control lesion sizes at early stages of infection. IFN-γ, TNF-α and IL-10 production did not differ among mouse strains. Myeloperoxidase assay showed augmented neutrophils influx 6 h and 72 h post - infection in gp91phox−/− mice, indicating a larger inflammatory response in gp91phox−/− even at early time points. At later time points, neutrophil numbers in lesions correlated with lesion size: larger lesions in gp91phox−/− at earlier times of infection corresponded to larger neutrophil infiltrates, while larger lesions in WT mice at the later points of infection also displayed larger numbers of neutrophils. Conclusion: ROS do not seem to be important in L. amazonensis killing, but they regulate the inflammatory response probably by controlling neutrophils numbers in lesions.

A study of oxygen isotopic fractionation during bio-induced calcite precipitation in eutrophic Baldeggersee, Switzerland

In order to better understand environmental factors controlling oxygen isotope shifts in autochthonous lacustrine carbonate sequences, we undertook an extensive one-year study (March, 1995 to February, 1996) of water-column chemistry and daily sediment trap material from a small lake in Central Switzerland. Comparisons between calculated equilibrium isotope values, using the fractionation equation of Friedman and O’Neil, (1977) and measured oxygen isotope ratios of calcite in the sediment-traps reveal that oxygen isotopic values of autochthonous calcite (δ18O) are in isotopic equilibrium with ambient water during most of the spring and summer, when the majority of the calcite precipitates. In contrast, small amounts of calcite precipitated in early-spring and again in late-autumn are isotopically depleted in 18O relative to the calculated equilibrium values, by as much as 0.8‰. This seasonally occurring apparent isotopic nonequilibrium is associated with times of high phosphorous concentrations, elevated pH (∼8.6) and increased [CO32−] (∼50 μmol/l) in the surface waters. The resulting weighted average δ18O value for the studied period is −9.6‰, compared with a calculated equilibrium δ18O value of −9.4‰. These data convincingly demonstrate that δ18O of calcite are, for the most part, a very reliable proxy for temperature and δ18O of the water.

Oxygen Production and Carbon Sequestration in an Upwelling Coastal Margin

We examined high-resolution cross-shelf distributions of particulate organic carbon (POC) and dissolved O(2) during the upwelling season off the Oregon coast. Oxygen concentrations were supersaturated in surface waters, and hypoxic in near-bottom waters, with greatly expanded hypoxic conditions late in the season. Simplified time-dependent mass balances on cross-shelf integrated concentrations of these two parameters, found the following: ( 1) The average net rate of photosynthesis generated 2.1 mmol O(2) m(-3) d(-1) and ( 2) essentially none of the corresponding net carbon fixation of 1.4 mmol m(-3) d(-1) could be accounted for in the observed standing stocks of POC. After examining other possible sinks for carbon, we conclude that most of the net production is being exported to the adjacent deep ocean. A simplified POC budget suggests that about a quarter of the export is via alongshore advection, and the remainder is due to some other process. We propose a simplistic conceptual model of across-shelf transport in which POC sinks to the bottom boundary layer where it comes into contact with mineral ballast material but is kept in suspension by high turbulence. When upwelling conditions ease, the BBL waters move seaward, carrying the suspended, ballasted POC with it where it sinks rapidly into the deep ocean at the shelf break. This suggests a mechanism whereby the duration and frequency of upwelling events and relaxations can determine the extent to which new carbon produced by photosynthesis in the coastal ocean is exported to depth rather than being respired on the shelf.

Prediction of Benthic Impact for Salmon Net-Pens Based on the Balance of Benthic Oxygen Supply and Demand

The ratio between oxygen supply and oxygen demand was examined as a predictor of benthic response to organic enrichment caused by salmon net-pen aquaculture. Oxygen supply to the benthos was calculated based on Fickian diffusion and near-bottom flow velocities. A strong linear correlation was found between measured carbon sedimentation rates and rates of benthic metabolism. This relationship allowed an estimation of oxygen demand based on sedimentation rates. Comparison of several production sites in Maine (USA) coastal waters showed that for sites where oxygen demand exceeded supply benthic impacts were high and for sites where oxygen supply exceeded demand benthic impacts were low. These findings were summarized in the form of a predictive model that should be useful in siting salmon production facilities.

Kinetics and Mechanism of Oxygen Delignification

Considerable research has been conducted into the kinetics and selectivity of the oxygen delignification process to overcome limitation in its use. However most studies were performed in a batch reactor whereby the hydroxide and dissolved oxygen concentrations are changing during the reaction time in an effort to simulate tower performance in pulp mills. This makes it difficult to determine the reaction order of the different reactants in the rate expressions. Also the lignin content and cellulose degradation of the pulp are only established at the end of the experiment when the sample is removed from the batch reactor. To overcome these deficiencies, we have adopted a differential reactor system used frequently for fluid-solid rate studies (so-called Berty reactor) for measurement of oxygen delignification kinetics. In this reactor, the dissolved oxygen concentration and the alkali concentration in the feed are kept constant, and the rate of lignin removal is determined from the dissolved lignin content in the outflow stream measured by UV absorption. The mass of lignin removed is verified by analyzing the pulp at several time intervals. Experiments were performed at different temperatures, oxygen pressures and caustic concentrations. The delignification rate was found to be first order in HexA-free residual lignin content. The delignification rate reaction order in caustic concentration and oxygen pressure were determined to be 0.42 and 0.44 respectively. The activation energy was found to be 53kJ/mol. The carbohydrate degradation during oxygen delignification can be described by two contributions: one due to radicals produced by phenolic delignification, and a much smaller contribution due to alkaline hydrolysis. From the first order of the reaction and the pKa of the active lignin site, a new oxygen delignification mechanism is proposed. The number 3 carbon atom in the aromatic ring with the attached methoxyl group forms the lignin active site for oxygen adsorption and subsequent electrophic reaction to form a hydroperoxide with a pKa value similar to that of the present delignification kinetics. The uniform presence of the aromatic methoxyl groups in residual lignin further support the first order in lignin kinetics.

Oxygen Supplementing, Biocompatible Outer Membranes for Enhanced Performance of Implantable Glucose Sensors

Lack of linearity and sensitivity, oxygen dependence, biofouling and tissue inflammation hinder the development of implantable biosensors for continuous monitoring of glucose. Herein, we report the development of stacked outer membranes based on LBL/PVA hydrogels that improve sensor sensitivity, linearity, oxygen independence and counter biofouling and inflammation. While the inner LBL membrane affords tunable diffusivity, the outer PVA is capable of releasing anti-inflammatory drugs/tissue response modifying agents to counter acute and chronic inflammation, and to induce neo-angiogenesis at the implant site. Sensors were fabricated by immobilizing GOx enzyme on top of 50 μm platinum wires, followed by deposition of stacked LBL/PVA hydrogel membranes. The response of the sensors at 0.7V to various glucose concentrations was studied. Michelis-Menten analysis was performed to quantify sensor performance in terms of linearity and oxygen dependence. The interplay between sensor performance and inward glucose diffusivity was elucidated using (i) various LBL membranes and (ii) various freeze-thaw (FT) cycles of PVA. Incorporation of LBL/PVA stacked membranes resulted in an 8 fold increase in sensor linearity and a 9 fold decrease in oxygen dependence compared to controls. The enhancement in the sensor performance is attributed to (i) the oxygen storing capability of PVA hydrogel due to the formation of hydrophobic domains during its freezing/ thawing employed for its physical crosslinking and (ii) regulation of glucose flux by the inner LBL membrane. Such membranes offer significant advantages over presently available outer membranes in lieu of (i) their ability to control inflammation, (ii) their modulus that closely matches that of subcutaneous human tissue, (iii) non-necessity of reactive chemical crosslinking agents, (iv) tunable sensitivity and (v) supplemental storage of oxygen.

Effects of exercise with oxygen prebreathe for decompression risk reduction

Astronauts performing extravehicular activities (EVA) are at risk for occupational hazards due to a hypobaric environment, in particular Decompression Sickness (DCS). DCS results from nitrogen gas bubble formation in body tissues and venous blood. Denitrogenation achieved through lengthy staged decompression protocols has been the mainstay of prevention of DCS in space. Due to the greater number and duration of EVAs scheduled for construction and maintenance of the International Space Station, more efficient alternatives to accomplish missions without compromising astronaut safety are desirable. ^ This multi-center, multi-phase study (NASA-Prebreathe Reduction Protocol study, or PRP) was designed to identify a shorter denitrogenation protocol that can be implemented before an EVA, based on the combination of adynamia and exercise enhanced oxygen prebreathe. Human volunteers recruited at three sites (Texas, North Carolina and Canada) underwent three different combinations (“PRP phases”) of intense and light exercise prior to decompression in an altitude chamber. The outcome variables were detection of venous gas embolism (VGE) by precordial Doppler ultrasound, and clinical manifestations of DCS. Independent variables included age, gender, body mass index, oxygen consumption peak, peak heart rate, and PRP phase. Data analysis was performed both by pooling results from all study sites, and by examining each site separately. ^ Ten percent of the subjects developed DCS and 20% showed evidence of high grade VGE. No cases of DCS occurred in one particular PRP phase with use of the combination of dual-cycle ergometry (10 minutes at 75% of VO2 peak) plus 24 minutes of light EVA exercise (p = 0.04). No significant effects were found for the remaining independent variables on the occurrence of DCS. High grade VGE showed a strong correlation with subsequent development of DCS (sensitivity, 88.2%; specificity, 87.2%). In the presence of high grade VGE, the relative risk for DCS ranged from 7.52 to 35.0. ^ In summary, a good safety level can be achieved with exercise-enhanced oxygen denitrogenation that can be generalized to the astronaut population. Exercise is beneficial in preventing DCS if a specific schedule is followed, with an individualized VO2 prescription that provides a safety level that can then be applied to space operations. Furthermore, VGE Doppler detection is a useful clinical tool for prediction of altitude DCS. Because of the small number of high grade VGE episodes, the identification of a high probability DCS situation based on the presence of high grade VGE seems justified in astronauts. ^

Blood-oxygen-level-dependent (BOLD) signal changes in total cortex and subcortex, pain, reward, and vigilance regions during mechanical pressure pain after morphine administration

Morphine is the most common clinical choice in the management of severe pain. Although the molecular mechanisms of morphine have already been characterized, the cerebral circuits by which it attenuates the sensation of pain have not yet been studied in humans. The objective of this two-arm (morphine versus placebo), between-subjects study was to examine whether morphine affects pain via pain-related cortical circuits, but also via reward regions that relate to the motivational state, as well as prefrontal regions that relate to vigilance as a result of morphine's sedative effects. Cortical activity was measured by the blood-oxygen-level-dependent (BOLD) signal changes using functional magnetic resonance imaging (fMRI). ^ The novelty of this study is at three levels: (i) to develop a methodology that will assess the average BOLD signal across subjects for the pain, reward, and vigilance cortical systems; (ii) to examine whether the reward and/or sedative effects of morphine are contributing factors to cortical regions associated with the motivational state and vigilance; and (iii) to propose a neuroanatomical model related to the opioid-sensitive effects of reward and sedation as a function of cortical activity related to pain in an effort to assess future analgesics. ^ Consistent with our hypotheses, our findings showed that the decrease in total pain-related volume activated between the post- and the pre-treatment morphine group was about 78%, while the post-treatment placebo group displayed only a 5% decrease when compared to pre-treatment levels of activation. The volume increase in reward regions was 451% in the post-treatment compared to the pre-treatment morphine condition. Finally, the volumetric decrease in vigilance regions was 63% in the posttreatment compared to the pre-treatment morphine condition. ^ These findings imply that changes in the blood flow of the reward and vigilance regions may be contributing factors in producing the analgesic effect under morphine administration. Future studies need to replicate this study in a higher resolution fMRI environment and to assess the proposed neuroanatomical model in patient populations. The necessity of pain research is apparent, since pain cuts across different diseases especially chronic ones, and thus, is recognized as a vital public health developing area. ^