Measurement Of Partial Pressure Research Articles

Oxygen solubility measured in aqueous or oily media by a method using a non-invasive sensor

The amount of dissolved oxygen (O2) in oils is one of the major factors that affect the extent of oil oxidation reactions. The aim of this work was to develop an experimental method to determine the Henry's law constant in oils, using a portable optical device for easy and non-intrusive O2 partial pressure measurement. The principle is based on the effect of quenching of luminescence by oxygen using a sensor probe glued inside a transparent glass flask. The method uses a mass conservation equation written for oxygen in both liquid and gaseous phases inside a closed flask. It was validated on water in the range of 5–50 °C, and then applied to non-polar media (dodecane, vegetable oil and Miglyol). The results show that oxygen is 5 times more soluble in sunflower oil than in water. This method is easy-to-implement and makes it possible to measure the Henry's constant for O2 in various types of vegetable oils.

Extending helium partial pressure measurement technology to JET DTE2 and ITER.

The detection limit for helium (He) partial pressure monitoring via the Penning discharge optical emission diagnostic, mainly used for tokamak divertor effluent gas analysis, is shown here to be possible for He concentrations down to 0.1% in predominantly deuterium effluents. This result from a dedicated laboratory study means that the technique can now be extended to intrinsically (non-injected) He produced as fusion reaction ash in deuterium-tritium experiments. The paper also examines threshold ionization mass spectroscopy as a potential backup to the optical technique, but finds that further development is needed to attain with plasma pulse-relevant response times. Both these studies are presented in the context of continuing development of plasma pulse-resolving, residual gas analysis for the upcoming JET deuterium-tritium campaign (DTE2) and for ITER.

Impact of Left Heart Bypass on Arterial Oxygenation During One-Lung Ventilation for Thoracic Aortic Surgery

The aim of this study was to reveal the mechanism of improved arterial oxygenation by measuring the changes in oxygenation before and after initiation of left heart bypass (LHB) during one-lung ventilation (OLV) for thoracic aortic surgery. Prospective, observational study. Single-institution, private hospital. The study comprised 50 patients who underwent aortic surgery via a left thoracotomy approach with LHB circulatory support. Patients were ventilated using pure oxygen during OLV, and the ventilator setting was left unchanged during the measurement period. The measurement of partial pressure of arterial oxygen (PaO2) was made at the following 4 time points: 2 minutes after heparin infusion (point 1 [P1]), 2 minutes after inflow cannula insertion through the left pulmonary vein (P2), immediately before LHB initiation (P3), and 10 minutes after LHB initiation (P4). The mean±standard deviation (mmHg) of PaO2 measurements at the P1, P2, P3, and P4 time points were 244±121, 250±123, 419±122, and 430±109, respectively, with significant increases between P1 and P3, P1 and P4, P2 and P3, and P2 and P4 (p<0.0001, respectively). No significant increase in PaO2 was seen between P1 and P2 or between P3 and P4. The improved arterial oxygenation during OLV in patients who underwent thoracic aortic surgery using LHB can be attributed to the insertion of an inflow cannula via the left pulmonary vein into the left atrium before LHB.

Heterogeneous kinetics of H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O, HNO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; and HCl on HNO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; hydrates (&amp;lt;i&amp;gt;α&amp;lt;/i&amp;gt;-NAT, &amp;lt;i&amp;gt;β&amp;lt;/i&amp;gt;-NAT, NAD) in the range 175–200 K

Abstract. Experiments on the title compounds have been performed using a multidiagnostic stirred-flow reactor (SFR) in which the gas phase as well as the condensed phase has been simultaneously investigated under stratospheric temperatures in the range 175–200 K. Wall interactions of the title compounds have been taken into account using Langmuir adsorption isotherms in order to close the mass balance between deposited and desorbed (recovered) compounds. Thin solid films at 1 µm typical thickness have been used as a proxy for atmospheric ice particles and have been deposited on a Si window of the cryostat, with the optical element being the only cold point in the deposition chamber. Fourier transform infrared (FTIR) absorption spectroscopy in transmission as well as partial and total pressure measurement using residual gas mass spectrometry (MS) and sensitive pressure gauges have been employed in order to monitor growth and evaporation processes as a function of temperature using both pulsed and continuous gas admission and monitoring under SFR conditions. Thin solid H2O ice films were used as the starting point throughout, with the initial spontaneous formation of α-NAT (nitric acid trihydrate) followed by the gradual transformation of α- to β-NAT at T &gt; 185 K. Nitric acid dihydrate (NAD) was spontaneously formed at somewhat larger partial pressures of HNO3 deposited on pure H2O ice. In contrast to published reports, the formation of α-NAT proceeded without prior formation of an amorphous HNO3 ∕ H2O layer and always resulted in β-NAT. For α- and β-NAT, the temperature-dependent accommodation coefficient α(H2O) and α(HNO3), the evaporation flux Jev(H2O) and Jev(HNO3) and the resulting saturation vapor pressure Peq(H2O) and Peq(HNO3) were measured and compared to binary phase diagrams of HNO3 ∕ H2O in order to afford a thermochemical check of the kinetic parameters. The resulting kinetic and thermodynamic parameters of activation energies for evaporation (Eev) and standard heats of evaporation ΔHev0 of H2O and HNO3 for α- and β-NAT, respectively, led to an estimate for the relative standard enthalpy difference between α- and β-NAT of −6.0 ± 20 kJ mol−1 in favor of β-NAT, as expected, despite a significantly larger value of Eev for HNO3 in α-NAT. This in turn implies a substantial activation energy for HNO3 accommodation in α- compared to β-NAT where Eacc(HNO3) is essentially zero. The kinetic (α(HCl), Jev(HCl)) and thermodynamic (Peq(HCl)) parameters of HCl-doped α- and β-NAT have been determined under the assumption that HCl adsorption did not significantly affect α(H2O) and α(HNO3) as well as the evaporation flux Jev(H2O). Jev(HCl) and Peq(HCl) on both α- and β-NAT are larger than the corresponding values for HNO3 across the investigated temperature range but significantly smaller than the values for pure H2O ice at T &lt; 200 K.

The annual and seasonal variability of the carbonate system in the Bay of Brest (Northwest Atlantic Shelf, 2008–2014)

From 2008 to 2014, the MAREL-Iroise buoy, located in the Bay of Brest, collected high-frequency measurements of partial pressure of CO2 (pCO2) and ancillary hydrographic parameters, in conjunction with a comprehensive sampling regime of two additional carbonate system variables total alkalinity (AT), and dissolved inorganic carbon (DIC). Biological processes drive variations in AT and DIC throughout the year, except in winter, when primary production is negligible and large freshwater inputs occur. Annually, the Bay of Brest generally behaves as a source of CO2 to the atmosphere (0.14±0.20molCm−2yr−1), showing inter-annual variability significantly linked to annual net community production (NCP). The presence of a large community of benthic filter feeders leads to high levels of particulate organic matter (POM) and opal deposition during the spring diatom bloom. Over the following few months, benthic POM remineralisation reduces the spring CO2 deficit relative to the atmosphere, and remineralisation of biogenic silica supplies further late spring primary production. The result is an inverse spring NCP – air-sea CO2 flux relationship, whereby greater NCP in early spring results in lower fluxes of CO2 into the Bay in late spring. This recycling mechanism, or silicic acid pump, also links the spring and summer NCP values, which are both determined by the peak wintertime nutrient concentrations. The carbonate system is further affected by the benthic community in winter, when CaCO3 dissolution is evident from notable deviations in the ΔAT:ΔDIC ratio. This study highlights the necessity of individual study of coastal, temperate ecosystems and contributes to a better understanding of what determines coastal areas as sinks or sources of CO2 to the atmosphere.

Diagnostic Analysis of the Oxygen Fraction at the Boundary Between Cathode Flowfield and Gas Diffusion Layer in the PEMFC

Enhancement of the fuel cell performance at higher current densities is important to improve the power density and reduce the cost of proton exchange membrane fuel cell (PEMFC) system. Mass transport overpotential is the major barrier to achieving high performance at high current density. The overpotential at the cathode is significantly large and the oxygen partial pressure in the oxygen reduction reaction (ORR) area is vital. Condensed water in the flowfield and the gas diffusion layer (GDL) reduces oxygen transport to the ORR area. Direct investigation of oxygen transport has been limited by an inability to resolve water saturation dependent properties. A novel diagnostic method to analyze the boundary between flowfield and GDL surface is required. A measurement of the oxygen partial pressure in the flowfield while the fuel cell is operating was introduced [1-3]. This method uses oxygen sensitive fluorophore materials whose fluorescent luminescence is a function of oxygen quenching as described by the Stern-Volmer equation. In the previous work, the oxygen quenching rate was modified in order to enable in-situ oxygen partial pressure measurement on the surface of the cathode GDL with typical operating conditions of an automotive PEMFC [3]. In this work, a computational fluid dynamic (CFD) based two-phase fuel cell model was newly developed to be validated with measured oxygen fractions. Figure 1 shows the geometric configuration of this tested single cell. Figure 2 shows that simulation of oxygen partial pressure distribution shows similarity to the previous experimental data. Figure 3 shows measured oxygen partial pressure on the cathode GDL surface along with fraction of flowfield channel length. This oxygen fraction is deviated from the average stoichiometric line. The spatial variability of current density, which is proportion to the oxygen consumption rate, is considered to be a large contributor. Combined empirical and modeling approaches enable to gain the mechanistic understanding of two-phase fluid flow in the flowfield and the surface of GDL, including water condensation and implication with the fuel cell operating conditions. Further analysis will be discussed.

Thermodynamics of gaseous barium cerate studied by Knudsen effusion mass spectrometry

BaCeO3 species, which are known to be excellent proton conductors, are potential candidates as electrolytes in hydrogen concentrators and fuel cells. Oxides of barium and cerium, with their reactivity can, in turn, form gaseous associates - complex molecules with two different types of atoms (not including oxygen). To predict the possibility of the existence of gaseous associates formed by barium and cerium oxides it is important to know their thermodynamic characteristics. Until the present investigation, gaseous cerates were unknown. High-temperature Knudsen effusion mass spectrometry was used to determine the partial pressures of vapor species over the BaO-CeO2 system, and the formation enthalpies of gaseous CeO2 and BaCeO3 were derived. Measurements of partial pressures and reaction enthalpies were performed with a MS-1301 mass spectrometer. Vaporization was carried out using molybdenum and tungsten effusion cells containing the samples under study and pure gold as a reference substance. A theoretical study of gaseous cerium dioxide and barium cerate was performed by several quantum chemical methods: DFT M06, DFT PBE0 and MP2. In the temperature range 1900-2120K, CeO and CeO2 were found to be the main vapor species over the solid CeO2 . Ba, BaO, CeO, CeO2 and BaCeO3 species were found in the vapor over the BaO-CeO2 mixture. On the basis of the equilibrium constant of the gaseous reaction BaO+CeO2 =BaCeO3 , the standard formation enthalpy of gaseous BaCeO3 (-1065±25kJ/mol) at 298K was determined. Energetically favorable structures of gaseous CeO2 and BaCeO3 were found and vibrational frequencies were evaluated in the harmonic approximation. The stability of BaCeO3 gaseous species was confirmed by high-temperature mass spectrometry. Gas-phase reactions involving gaseous barium and cerium oxides with gaseous barium cerate were studied. The enthalpies of the formation reactions of gaseous barium cerate from gaseous BaO and CeO2 were evaluated theoretically and the obtained values were in agreement with the experimental ones. Copyright © 2016 John Wiley & Sons, Ltd.

The Carbonate Chemistry of the “Fattening Line,” Willapa Bay, 2011–2014

Willapa Bay has received a great deal of attention in the context of rising atmospheric CO2 and the concomitant effects of changes in bay carbonate chemistry, referred to as ocean acidification, and the potential effects on the bay’s naturalized Pacific oyster (Crassostrea gigas) population and iconic oyster farming industry. Competing environmental stressors, historical variability in the oyster settlement record, and the absence of adequate historical observations of bay-water carbonate chemistry all conspire to cast confusion regarding ocean acidification as the culprit for recent failures in oyster larval settlement. We present the first measurements of the aqueous CO2 partial pressure (PCO2) and the total dissolved carbonic acid (TCO2) at the “fattening line,” a location in the bay that has been previously identified as optimal for both larval oyster retention and growth, and collocated with a long historical time series of larval settlement. Samples were collected from early 2011 through late 2014. These measurements allow the first rigorous characterization of Willapa Bay aragonite mineral saturation state (Ωar), which has been shown to be of leading importance in determining the initial shell formation and growth of larval Crassostrea gigas. Observations show that the bay is usually below Ωar levels that have been associated with poor oyster hatchery production and with chronic effects noted in experimental work. Bay water only briefly rises to favorable Ωar levels and does so out of phase with optimal thermal conditions for spawning. Thermal and carbonate conditions are thus coincidentally favorable for early larval development for only a few weeks at a time each year. The limited concurrent exceedance of thermal and Ωar thresholds suggests the likelihood of high variability in settlement success, as seen in the historical record; however, estimates of the impact of elevated atmospheric CO2 suggest that pre-industrial Ωar conditions were more persistently favorable for larval development and more broadly coincident with thermal optima.

The Effect of Norepinephrine and Dopamine on Radial Forearm Flap Partial Tissue Oxygen Pressure and Microdialysate Metabolite Measurements: A Randomized Controlled Trial.

Patients undergoing ablative and reconstructive head and neck surgery with a microvascular flap have multiple factors that potentially decrease postoperative mean arterial pressure, which may endanger flap survival. The safety of vasopressor use has long been a topic of discussion. The authors analyzed the effect of vasopressors on microvascular flap perfusion after head and neck cancer reconstruction. A total of 27 patients were enrolled in a randomized, controlled, clinical trial. A microvascular radial forearm flap was used for reconstruction. Patients were allocated into one of three groups: dopamine, norepinephrine, and control. The intervention groups received the vasoactive drug, aiming to maintain the mean arterial pressure between 80 and 90 mmHg. Normovolemia was maintained according to central venous pressure. Flap perfusion was monitored with continuous tissue partial pressure of oxygen and microdialysate metabolite (lactate-to-pyruvate ratio) measurements. No adverse effects were observed, and postoperative recovery was free of complications in all groups. Neither the lactate-to-pyruvate ratio nor continuous tissue partial pressure of oxygen values differed significantly between groups during the first 24 hours of the vasoactive drug infusion period or during the 72-hour follow-up. Norepinephrine and dopamine are safe and effective vasopressors for use during the postoperative period following head and neck cancer surgery with microvascular reconstruction. Dopamine should be used with caution, however, because of the risk of side effects. Therapeutic, II.

Hydrogen concentration measurement in high temperature applications using hydrogen permeation

With the increasing use of hydrogen in energy process engineering and as chemical reactant, the importance of hydrogen sensors is rising. However, there are few established methods to measure the hydrogen concentration of a gas-mixture at high temperatures. Also the in situ measurement at these temperatures in chemical reactors is challenging. A sensor, which is based on hydrogen permeation, could be a cheap and practical solution for the in situ measurement at high temperatures.A permeation hydrogen sensor for the measurement of the hydrogen partial pressure was developed and built. The concept of the sensor is a small, hermetically sealed nickel tube working as a hydrogen permeable membrane filled with pure hydrogen. It is in contact with the measurement gas and connected to a pressure sensor. Under stationary conditions a equilibrium between the hydrogen partial pressure of the tube and the measurement gas will be established. Since the tube is filled only with hydrogen, the pressure sensor connected with the nickel-tube measures the hydrogen partial pressure of the measurement gas.Such a sensor was modeled, developed, built and characterized. The most important calculations, the general design of the sensor as well as the most important results of the experiments are presented in this paper. The sensor worked with a good accuracy and showed a response time of about 1000 s at 60 °C and 200 s at 900 °C. A response time lower than 200 s for temperatures above 600 °C is possible with an improved sensor design. Also, an in-situ measurement of the steam content inside a shift reactor was conducted, the results matched the calculated steam contents from a reactor balance very precisely.

In situ metrology to characterize water vapor delivery during atomic layer deposition

Water is often employed as the oxygen source in metal oxide atomic layer deposition (ALD) processes. It has been reported that variations in the amount of water delivered during metal oxide ALD can impact the oxide film properties. Hence, one contribution to optimizing metal oxide ALD processes would be to identify methods to better control water dose. The development of rapid, quantitative techniques for in situ water vapor measurements during ALD processes would be beneficial to achieve this goal. In this report, the performance of an in situ tunable diode laser absorption spectroscopy (TDLAS) scheme for performing rapid, quantitative water partial pressure measurements in a representative quarter-inch ALD delivery line is described. This implementation of TDLAS, which utilizes a near-infrared distributed-feedback diode laser and wavelength modulation spectroscopy, provides measurements of water partial pressure on a timescale comparable to or shorter than the timescale of the gas dynamics in typical ALD systems. Depending on the degree of signal averaging, this TDLAS system was capable of measuring the water partial pressure with a detection limit in the range of ∼0.80 to ∼0.08 Pa. The utility of this TDLAS scheme was demonstrated by using it to identify characteristics of a representative water delivery system that otherwise would have been difficult to predict. Those characteristics include (1) the magnitude and time dependence of the pressure transient that can occur during water injection, and (2) the dependence of the steady-state water partial pressure on the carrier gas flow rate and the setting of the water ampoule flow restriction.

Imaging how and where we breathe oxygen: another Big Short?

The Big Short (1) tells the story of a small group of skeptics who profited from the financial crisis in 2007 by betting against collateralized (mortgage) debt obligations (CDO). Importantly, the novel paints a clear picture of the eccentric nature of contrarians who think divergently and against the grain or bet against an accepted truth or “sure” thing. In a similar manner, Ishii and co-workers’ recent work (2) describes their team’s development of a pulmonary imaging technology that provides divergent and disruptive in vivo lung measurements of oxygen partial pressure in the context of the prevailing and longstanding consensus around FEV1 as the definitive diagnostic of chronic lung disease.

Mass separation of deuterium and helium with conventional quadrupole mass spectrometer by using varied ionization energy.

Deuterium pressure in deuterium-helium mixture gas is successfully measured by a common quadrupole mass spectrometer (model: RGA200) with a resolution of ∼0.5 atomic mass unit (AMU), by using varied ionization energy together with new developed software and dedicated calibration for RGA200. The new software is developed by using MATLAB with the new functions: electron energy (EE) scanning, deuterium partial pressure measurement, and automatic data saving. RGA200 with new software is calibrated in pure deuterium and pure helium 1.0 × 10(-6)-5.0 × 10(-2) Pa, and the relation between pressure and ion current of AMU4 under EE = 25 eV and EE = 70 eV is obtained. From the calibration result and RGA200 scanning with varied ionization energy in deuterium and helium mixture gas, both deuterium partial pressures (P(D2)) and helium partial pressure (P(He)) could be obtained. The result shows that deuterium partial pressure could be measured if P(D2) > 10(-6) Pa (limited by ultimate pressure of calibration vessel), and helium pressure could be measured only if P(He)/P(D2) > 0.45, and the measurement error is evaluated as 15%. This method is successfully employed in EAST 2015 summer campaign to monitor deuterium outgassing/desorption during helium discharge cleaning.

Measurement of the oxygen partial pressure and thermodynamic modeling of the U–Nd–O system

Fission products greatly impact the properties of fuel necessitating a thorough understanding of the thermochemical properties of oxide fuels with fission products. However, thermochemical data for the U–Nd–O system is insufficient even though neodymium is a major fission product. As neodymium will likely be present as a solute in UO2, this research focuses on the study of (U1−yNdy)O2±x. Experimental measurements and analyses of the oxygen partial pressure (pO2)-temperature-oxygen to metal ratio (O/M ratio) relationships were performed using a thermogravimetric analyzer (TGA) and an oxygen analyzer. Thermodynamic computational modeling was performed using the CALPHAD (CALculation of PHAse Diagrams) method with the FactSage software. The Gibbs energy of the (U1−yNdy)O2±x solid solution was described by the compound energy formalism (CEF), which is based on earlier thermodynamic modeling data of the binary U–O system from Guéneau et al.. The thermodynamic and phase diagram data of the U–Nd–O system produced in this work show good agreement with the experimental data.

Factors associated with blood oxygen partial pressure and carbon dioxide partial pressure regulation during respiratory extracorporeal membrane oxygenation support: data from a swine model.

ObjectiveThe aim of this study was to explore the factors associated with blood oxygen partial pressure and carbon dioxide partial pressure.MethodsThe factors associated with oxygen - and carbon dioxide regulation were investigated in an apneic pig model under veno-venous extracorporeal membrane oxygenation support. A predefined sequence of blood and sweep flows was tested.ResultsOxygenation was mainly associated with extracorporeal membrane oxygenation blood flow (beta coefficient = 0.036mmHg/mL/min), cardiac output (beta coefficient = -11.970mmHg/L/min) and pulmonary shunting (beta coefficient = -0.232mmHg/%). Furthermore, the initial oxygen partial pressure and carbon dioxide partial pressure measurements were also associated with oxygenation, with beta coefficients of 0.160 and 0.442mmHg/mmHg, respectively. Carbon dioxide partial pressure was associated with cardiac output (beta coefficient = 3.578mmHg/L/min), sweep gas flow (beta coefficient = -2.635mmHg/L/min), temperature (beta coefficient = 4.514mmHg/ºC), initial pH (beta coefficient = -66.065mmHg/0.01 unit) and hemoglobin (beta coefficient = 6.635mmHg/g/dL).ConclusionIn conclusion, elevations in blood and sweep gas flows in an apneic veno-venous extracorporeal membrane oxygenation model resulted in an increase in oxygen partial pressure and a reduction in carbon dioxide partial pressure 2, respectively. Furthermore, without the possibility of causal inference, oxygen partial pressure was negatively associated with pulmonary shunting and cardiac output, and carbon dioxide partial pressure was positively associated with cardiac output, core temperature and initial hemoglobin.

Data-based estimates of the ocean carbon sink variability – first results of the Surface Ocean &amp;lt;i&amp;gt;p&amp;lt;/i&amp;gt;CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Mapping intercomparison (SOCOM)

Abstract. Using measurements of the surface-ocean CO2 partial pressure (pCO2) and 14 different pCO2 mapping methods recently collated by the Surface Ocean pCO2 Mapping intercomparison (SOCOM) initiative, variations in regional and global sea–air CO2 fluxes are investigated. Though the available mapping methods use widely different approaches, we find relatively consistent estimates of regional pCO2 seasonality, in line with previous estimates. In terms of interannual variability (IAV), all mapping methods estimate the largest variations to occur in the eastern equatorial Pacific. Despite considerable spread in the detailed variations, mapping methods that fit the data more closely also tend to agree more closely with each other in regional averages. Encouragingly, this includes mapping methods belonging to complementary types – taking variability either directly from the pCO2 data or indirectly from driver data via regression. From a weighted ensemble average, we find an IAV amplitude of the global sea–air CO2 flux of 0.31 PgC yr−1 (standard deviation over 1992–2009), which is larger than simulated by biogeochemical process models. From a decadal perspective, the global ocean CO2 uptake is estimated to have gradually increased since about 2000, with little decadal change prior to that. The weighted mean net global ocean CO2 sink estimated by the SOCOM ensemble is −1.75 PgC yr−1 (1992–2009), consistent within uncertainties with estimates from ocean-interior carbon data or atmospheric oxygen trends.

Partial pressure measurement standard for characterizing partial pressure analyzers and measuring outgassing rates

In this work, a measurement standard was established for partial pressures in high and ultrahigh vacuum conditions. Three (or more, with higher uncertainty) different gases with known partial pressures from 10−8 to 10−2 Pa can be generated in a calibration chamber of an ultrahigh vacuum system by a continuous expansion method. The ratio between two partial pressures can range from 10−6 to 1. The readings of partial pressure analyzers can be calibrated by comparing them to known partial pressures. The calibration chamber is connected to a sample chamber, where outgassing samples can be inserted via a load lock. With an in situ calibrated partial pressure analyzer, the outgassing rate from the samples can be measured in a traceable way to the international systems of units.

Noninvasive Measurement of Carbon Dioxide during One-Lung Ventilation with Low Tidal Volume for Two Hours: End-Tidal versus Transcutaneous Techniques.

BackgroundThere may be significant difference between measurement of end-tidal carbon dioxide partial pressure (PetCO2) and arterial carbon dioxide partial pressure (PaCO2) during one-lung ventilation with low tidal volume for thoracic surgeries. Transcutaneous carbon dioxide partial pressure (PtcCO2) monitoring can be used continuously to evaluate PaCO2 in a noninvasive fashion. In this study, we compared the accuracy between PetCO2 and PtcCO2 in predicting PaCO2 during prolonged one-lung ventilation with low tidal volume for thoracic surgeries.MethodsEighteen adult patients who underwent thoracic surgeries with one-lung ventilation longer than two hours were included in this study. Their PetCO2, PtcCO2, and PaCO2 values were collected at five time points before and during one-lung ventilation. Agreement among measures was evaluated by Bland-Altman analysis.ResultsNinety sample sets were obtained. The bias and precision when PtcCO2 and PaCO2 were compared were 4.1 ± 6.5 mmHg during two-lung ventilation and 2.9 ± 6.1 mmHg during one-lung ventilation. Those when PetCO2 and PaCO2 were compared were -11.8 ± 6.4 mmHg during two-lung ventilation and -11.8 ± 4.9 mmHg during one-lung ventilation. The differences between PtcCO2 and PaCO2 were significantly lower than those between PetCO2 and PaCO2 at all five time-points (p < 0.05).ConclusionsPtcCO2 monitoring was more accurate for predicting PaCO2 levels during prolonged one-lung ventilation with low tidal volume for patients undergoing thoracic surgeries.

Impact of Corneal Endothelial Dysfunctions on Intraocular Oxygen Levels in Human Eyes.

We studied the implications of corneal endothelial dysfunctions on oxidative stress in the anterior segment via in vivo measurements of oxygen partial pressure (pO2) in the anterior chamber (AC) of human eyes. We recruited 51 patients undergoing cataract surgery and/or endothelial keratoplasty (EK). Endothelial cell density (ECD; n = 33) and central corneal thickness (CCT; n = 41) were measured on patients with relatively clear corneas. Before surgery, an oxygen sensor was introduced into the AC via a peripheral corneal paracentesis. In all patients, seven measurements of pO2 were obtained by positioning the flexible tip near the endothelium at the central cornea, at four cardinal subendothelial locations near the midperipheral cornea, and in the mid-AC and AC angle. In patients with pseudophakia or eyes undergoing cataract surgery, pO2 also was measured near the lens surface and in the posterior chamber. Consistent with our previous reports, a steep oxygen gradient was noted in the anterior segment of normal controls (n = 24). In patients with endothelial dysfunctions (n = 27), there was a significant increase of pO2 at all five subendothelial locations without a significant increase of pO2 in the AC angle. By regression analyses, subendothelial pO2 correlated inversely with ECD and positively with CCT in patients with endothelial dysfunctions. This study demonstrates an even steeper intraocular oxygen gradient in eyes with corneal endothelial dysfunctions. It suggests that the reduced oxygen consumption in corneal endothelial cells may increase oxidative stress in the AC and the existence of an alternative aqueous inflow pathway that maintains a relatively low and constant pO2 at the AC angle.

In-Situ Measurement of Oxygen Particial Pressure on the Surface of a Cathode GDL with Automotive Compatible Operating Conditions

Cathode oxygen concentration is vital for fuel cell performance. In-situ measurement of oxygen partial pressure provides a method to determine the local oxygen concentration in the cathode. A novel method that uses oxygen sensitive fluorophore materials has been developed to directly measure the oxygen partial pressure in the cathode flow field during fuel cell operation. Fluorescent luminescence is sensitive to oxygen quenching as described by the Stern-Volmer equation. The oxygen quenching rate was modified to meet a desired range of oxygen partial pressure measurement. In a previous study, a fluorophore ink material with a platinum porphyrin based fluorophore dispersed in the FIB polymer was developed. This fluorophore ink material showed a sufficient level of intensity of fluorescent luminescence to cover the typical operating condition of an automotive proton exchange membrane fuel cell (PEMFC). However, this fluorophore ink material was too viscous for the surface of the gas diffusion layer (GDL) where ink material clogged the pores of the GLD and lowered the fuel cell performance. In this study, the fluorophore ink material was modified. A newly developed less viscous fluorophore ink material was confirmed that the fuel cell performance was not affected by the sprayed ink materials. Concurrently, it was confirmed that the oxygen quenching rate of this fluorophore materials were retained. The Stern-Volmer calibration enabled accurate in-situ oxygen partial pressure measurements on the surface of the cathode GDL to cover the typical operating conditions of an automotive PEMFC.