SEARCH · Search PubMed

Results for “GASES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources

PubMedDate not supplied

Effects of normobaric and hypobaric hypoxia on ventilation and arterial blood gases in ducks.

We measured ventilation (V1) and arterial blood gases in awake Pekin ducks exposed to normoxia at sea level, normobaric hypoxia achieved by lowering FIO2 at normal barometric pressure (NORMO), and hypobaric hypoxia achieved with a low pressure chamber and 21% O2 (HYPO). Average normoxic values were: V1 = 0.46 L . (kg.min)-1, PaO2 = 99.7 Torr, PaCO2 = 30.1 Torr. At PIO2 = 90 Torr, NORMO and HYPO measurements were not significantly different (P greater than 0.05). At PO2 = 46 Torr, NORMO V1 was less than HYPO V1 but blood gases were not significantly different: VI = 1.00 vs 1.45 L . (kg.min)-1; PaO2 = 31.3 vs 33.0 Torr; PaCO2 = 11.5 vs 10.6 Torr. Although both tidal volume (VT) and respiratory frequency (fR) were greater in HYPO, similar blood gases with NORMO and HYPO suggest similar parabronchial ventilation. The results suggest increased physiologic dead space, caused by reduced efficacy of aerodynamic valving, with reduced gas density in hypobaria.

Air Pressure↗

PubMed1995

Evaluating the effects of elevated levels of atmospheric trace gases on herbs and shrubs: a prototype dual array field exposure system.

In the context of global climate change, an understanding of the long-term effects of increasing concentrations of atmospheric trace gases (carbon dioxide, CO(2), ozone, O(3), oxides of nitrogen, NO(x) etc.) on both cultivated and native vegetation is of utmost importance. Over the years, under field conditions, various trace gas-vegetation exposure methodologies with differing advantages and disadvantages have been used. Because of these variable criteria, with elevated O(3) or CO(2) levels, at the present time the approach of free-air experimental-release of the gas into study plots is attracting much attention. However, in the case of CO(2), this approach (using 15 m diameter study plot with a single circular array of vent pipes) has proven to be cost prohibitive (about 59000-98000 dollars/year/replicate) due to the consumption of significant quantities of the gas to perform the experiment (CO(2) level elevated to 400 ppm above the ambient). Therefore, in this paper, we present a new approach consisting of a dual, concentric exposure array of vertical risers or vent pipes. The purpose of the outer array (17 m diameter) is to vent ambient air outward and toward the incoming wind, thus providing an air curtain to reduce the velocity of that incoming wind to simulate the mode or the most frequently occurring wind speed at the study site. The inner array (15 m diameter) vents the required elevated levels of trace gases (CO(2), O(3), etc.) into the study plot. This dual array system is designed to provide spatial homogeneity (shown through diffusion modeling) of the desired trace-gas levels within the study plot and to also reduce its consumption. As an example, while in the single-array free-air CO(2)-release system the consumption of CO(2) to elevate its ambient concentration by 400 ppm is calculated to be about 980 tons/year/replicate, it is estimated that in the dual array system it would be approximately 590 tons/year/replicate. Thus, the dual array system may provide substantial cost savings (24000-39000 dollars/year/replicate) in the CO(2) consumption (60-100 dollars/ton of CO(2)) alone. Similarly, benefits in the requirements of other trace gases (O(3), NO(x), etc.) are expected, in future multivariate studies on global climate change.

Journal Article↗

PubMed1982

Effects of small nonpolar molecules on membrane compressibility and permeability. A theoretical study of the effects of anesthetic gases.

We explore from a theoretical perspective the effects of small nonpolar molecules, such as anesthetic gases, on membrane compressibility and permeability. As a model system we expand a previously proposed generalization of Nagle's model for biomembrane phase transitions. In this model anesthetic gases alter membrane compressibility, causing profound changes in membrane permeability. Anesthetics either increase or decrease membrane permeability, depending on whether the membrane lipid is originally in the solid or melted state, or in a two-phase region. These changes are reversed by high pressure, in agreement with experimental results. Anesthetic-induced changes in compressibility are predicted to inhibit fusion of phospholipid vesicles to each other and to planar bilayers, and thus might be expected to inhibit the fusion of presynaptic vesicles with the presynaptic nerve membrane. This work provides a detailed molecular theory for many of the effects of anesthetic gases on both synapse and axon, and provides a coherent framework for understanding diverse experimental results.

Anesthesia↗

PubMed1995

High frequency oscillation, respiratory activity and changes in blood gases.

Spontaneous respiratory activity during high frequency oscillation (HFO) and its relationship to changes in blood gases on transfer to HFO has been assessed. Eighteen infants were studied, median gestational age 27 weeks and postnatal age 1 day. Simultaneous measurements of changes in oesophageal and airway pressure, flow and volume were made during a period of conventional ventilation and then during HFO. From these recordings, the infants' spontaneous respiratory rate during the two ventilatory techniques were calculated. Arterial blood gases were measured immediately before and after a 30-min period of HFO. All the infants were breathing during conventional ventilation (median rate of 55 breaths/min). On transfer to HFO, the respiratory rate of the whole group decreased to a median of 23 breaths/min (P < 0.001), but only five infants became apnoeic. The changes in respiratory rate did not relate significantly to changes in PaCO2. Oxygenation deteriorated in four of the five apnoeic infants and in the two infants who became agitated during HFO. In the remaining 11 infants, whose median respiratory rate was 28 breaths/min (range 15-77) during HFO, oxygenation improved by a median of 12 mmHg (range 4-42). We conclude that, in the majority of infants, spontaneous respiratory activity during HFO is compatible with improvements in blood gases.

Carbon Dioxide↗

PubMed1989

The effect of ventilation on aortic blood gases during left ventricular ejection before separation from cardiopulmonary bypass.

The time to begin ventilating a cardiac surgical patient recovering from hyperkalemic arrest is controversial. Those who advocate ventilating as soon as the left ventricle begins to eject believe that blood ejected from the left ventricle is likely to be hypoxic since it perfuses collapsed, nonventilated alveoli and that this may be the major blood supply perfusing the coronary arteries. The present study attempts to answer this question by sampling blood gases from the aorta in proximity to the coronary ostia in patients both before and after ventilation. Ten patients undergoing coronary artery bypass grafting using the left internal mammary artery were studied. Each patient served as his own control. Distal anastomoses were placed under hyperkalemic, hypothermic cardiac arrest. The aorta was unclamped, and an intrinsic or paced heart rate of 70 beats per minute was achieved. The heart was allowed to eject to a pulse pressure of 20 to 40 mmHg. Rectal temperatures were between 32 degrees C and 34 degrees C. Blood gases were drawn simultaneously from the proximal aortic root, radial artery, pulmonary artery, and the venous circuit of the cardiopulmonary bypass (CPB) machine. The lungs were then twice inflated with a sustained positive pressure of 30 cm H2O, and the patient was ventilated (10 mL/kg tidal volume, FIO2 1.0, 10 breaths per minute) for two minutes. Another set of blood gases was then obtained. Filling pressures, aortic systolic and diastolic pressures, and CPB flows were kept constant for both sets of samples. There was no significant difference in aortic root PaO2 attributable to ventilation. PCO2 was significantly lower, and pH was significantly higher in the ventilated group.(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta↗

PubMed2004

[Changes in blood gases with temperature: implications for clinical practice].

OBJECTIVE: To understand changes in blood gases results with core temperature. METHODS: Analysis from two case reports. RESULTS: Hypothermia induces a decrease in PaCO(2) with a related increase in pH, thus a physiologic alkalosis. Decrease in PaCO(2) is due to an increase of gas solubility and a decrease of peripheral consumption that can be estimated from comparison between corrected and non-corrected for temperature blood gases. For O(2), variations of temperature induce variations of solubility but also of haemoglobin affinity for O(2). During hyperthermia, haemoglobin affinity for O(2) is decreased with a decreased SvO(2) for a same PvO(2). SvO(2) ischemic or therapeutic thresholds are thus modified with core temperature. CONCLUSION: Blood gases cannot be understood without patient core temperature. Physiologic variations of PaCO(2) and pH must probably be tolerated. Ischemic threshold should be estimated on PvO(2), not only on PvO(2).

Aged↗

PubMed2006

Destruction of PCDD/Fs by SCR from flue gases of municipal waste incinerator and metal smelting plant.

Partitioning of PCDD/F congeners between vapor/solid phases and removal and destruction efficiencies achieved with selective catalytic reduction (SCR) system for PCDD/Fs at an existing municipal waste incinerator (MWI) and metal smelting plant (MSP) in Taiwan are evaluated via stack sampling and analysis. The MWI investigated is equipped with electrostatic precipitators (EP, operating temperature: 230 degrees C), wet scrubbers (WS, operating temperature: 70 degrees C) and SCR (operating temperature: 220 degrees C) as major air pollution control devices (APCDs). PCDD/F concentration measured at stack gas of the MWI investigated is 0.728 ng-TEQ/Nm(3). The removal efficiency of WS+SCR system for PCDD/Fs reaches 93% in the MWI investigated. The MSP investigated is equipped with EP (operating temperature: 240 degrees C) and SCR (operating temperature: 290 degrees C) as APCDs. The flue gas sampling results also indicate that PCDD/F concentration treated with SCR is 1.35 ng-TEQ/Nm(3). The SCR system adopted in MSP can remove 52.3% PCDD/Fs from flue gases (SCR operating temperature: 290 degrees C, Gas flow rate: 660 kN m(3)/h). In addition, the distributions of PCDD/F congeners observed in the flue gases of the MWI and MSP investigated are significantly different. This study also indicates that the PCDD/F congeners measured in the flue gases of those two facilities are mostly distributed in vapor phase prior to the SCR system and shift to solid phase (vapor-phase PCDD/Fs are effectively decomposed) after being treated with catalyst. Besides, the results also indicate that with SCR highly chlorinated PCDD/F congeners can be transformed to lowly chlorinated PCDD/F congeners probably by dechlorination, while the removal efficiencies of vapor-phase PCDD/Fs increase with increasing chlorination.

Air Pollution↗

PubMed2005

Chronic exposure to anesthetic gases affects balance control in operating room personnel.

Exposure to anesthetic gases is known to alter certain structures and functions of the central nervous system. As the effects of long-term exposure on balance control mechanisms have been the subject of few investigations, these were evaluated in 53 operating room personnel exposed to anesthetic gases and in 53 non-exposed individuals. Balance control was assessed by static and dynamic posturography. Exposed workers had the worst static and dynamic postural performances, particularly in the eyes closed condition, suggesting increased dependency on vision and decreased use of proprioception. This poorer ability to modify the weight and to switch the different cues controlling balance suggests central information processing disorders. By impairing information and its central integration, exposure to anesthetics gases leads to inappropriate organization of sensorimotor stabilization strategies.

Adult↗

PubMed2001

Effects of chronic exposure to anaesthetic gases on some immune parameters.

A cross-sectional survey was carried out to evaluate the relation between occupational exposure to low levels of anaesthetic gases (nitrous oxide and isoflurane) and immune parameters. Fifty-one anaesthetists were recruited among different Services of Anaesthesiology and Reanimation. The control group consisted of non-exposed physicians, similar for gender, age, and job grade. Total number of lymphocytes, lymphocyte subpopulations and the natural killer (NK) cytotoxic activity were measured. Information on personal and professional characteristics and on short- and long-term exposure was collected. Percentages of T cells (CD3) decreased significantly in anaesthetists compared to controls, whereas numbers of NK cells (CD16+ CD3-) increased. After correction for confounders, short-term (last 2 weeks) exposure was associated with a decrease in percentages of total T and T helper (CD4) cells. Furthermore, T helper percentages were significantly reduced with increasing individual exposure score evaluated on the basis of working days and levels of anaesthetic gases in operating rooms. A significant X-ray-associated increase of numbers and percentages of NK cells was lastly observed. Despite limited present exposure to anaesthetic gases, a specific derangement in lymphocyte subpopulations, with T lymphocytes more affected than B, has been observed.

Adult↗

PubMed1985

Perfluorocarbon gases in vitreous surgery.

Fifty-six patients with complicated retinal detachments were managed with vitreous surgery and one of two perfluorocarbon gases. These gases are capable of greater expansion and greater longevity compared to sulfur hexafluoride. Forty-five patients received perfluoropropane (C3F8), eleven received perfluoroethane (C2F6). The retinas of 31 patients (55.4%) were attached at six months after the disappearance of the gas. In many instances, operations performed with air-sulfur hexafluoride mixtures had failed and the retina was subsequently reattached with the use of the perfluorocarbon gases. The major complications were increased intraocular pressure, which was usually transient, and gas-induced lens opacities.

Fluorocarbons↗

PubMed2002

Field measurement of acid gases and soluble anions in atmospheric particulate matter using a parallel plate wet denuder and an alternating filter-based automated analysis system.

We present a new fully automated instrument for the measurement of acid gases and soluble anionic constituents of atmospheric particulate matter. The instrument operates in two independent parallel channels. In one channel, a wet denuder collects soluble acid gases; these are analyzed by anion chromatography (IC). In a second channel, a cyclone removes large particles and the aerosol stream is then processed by another wet denuder to remove potentially interfering gases. The particles are then collected by one of two glass fiber filters which are alternately sampled, washed, and dried. The washings are preconcentrated and analyzed by IC. Detection limits of low to subnanogram per cubic meter concentrations of most gaseous and particulate constituents can be readily attained. The instrument has been extensively field-tested; some field data are presented. Results of attempts to decipher the total anionic constitution of urban ambient aerosol by IC-MS analysis are also presented.

Journal Article↗

PubMed2002

Dissolved gases as partitioning tracers for determination of hydrogeological parameters.

In this study, dissolved Kr and SF6 gases were used to determine various hydrogeological parameters of laboratory columns under water-saturated and partially saturated conditions as a function of the flow velocity. The dissolved gases behaved conservatively in saturated columns but were significantly retarded in unsaturated conditions as a direct function of the Henry's law constant (KH) and the ratio of column pore spaces filled with air and water (Vg/Vw). Lower aqueous diffusion coefficients for SF6 compared to that for Kr also resulted in significant rate-limited mass transport across gas-water interface. This effect was exacerbated at higher flow velocities as was indicated by the asymmetric shape of breakthrough curves, more so in the case of SF6. A nonequilibrium advective-dispersive transport model accurately described tracer breakthrough and was used to estimate parameters such as final Vg/Vw under partially saturated conditions and partitioning rates. Internally consistent model results were obtained for both dissolved gases despite the wide range in physical properties (e.g., KH and aqueous diffusion coefficients), suggesting that dissolved Kr and SF6 may be used in conjunction to delineate and validate aquifer characteristics simultaneously from a single pulse injection of the tracer.

Geological Phenomena↗

PubMed2001

History of trace gases in presolar diamonds inferred from ion-implantation experiments.

Diamond grains are the most abundant presolar grains found in primitive meteorites. They formed before the Solar System, and therefore provide a record of nuclear and chemical processes in stars and in the interstellar medium. Their origins are inferred from the unusual isotopic compositions of trace elements-mainly xenon-which suggest that they came from supernovae. But the exact nature of the sources has been enigmatic, as has the method by which noble gases were incorporated into the grains. One observation is that different isotopic components are released at different temperatures when the grains are heated, and it has been suggested that these components have different origins. Here we report results of a laboratory study that shows that ion implantation (previously suggested on other grounds) is a viable mechanism for trapping noble gases. Moreover, we find that ion implantation of a single isotopic composition can produce both low- and high-temperature release peaks from the same grains. We conclude that both isotopically normal and anomalous gases may have been implanted by multiple events separated in space and/or time, with thermal processing producing an apparent enrichment of the anomalous component in the high-temperature release peak. The previous assumption that the low- and high-temperature components were not correlated may therefore have led to an overestimate of the abundance of anomalous argon and krypton, while obscuring an enhancement of the light-in addition to the heavy-krypton isotopes.

Journal Article↗

PubMed2002

Bose-Einstein condensation of atomic gases.

The early experiments on Bose-Einstein condensation in dilute atomic gases accomplished three long-standing goals. First, cooling of neutral atoms into their motional ground state, thus subjecting them to ultimate control, limited only by Heisenberg's uncertainty relation. Second, creation of a coherent sample of atoms, in which all occupy the same quantum state, and the realization of atom lasers - devices that output coherent matter waves. And third, creation of a gaseous quantum fluid, with properties that are different from the quantum liquids helium-3 and helium-4. The field of Bose-Einstein condensation of atomic gases has continued to progress rapidly, driven by the combination of new experimental techniques and theoretical advances. The family of quantum-degenerate gases has grown, and now includes metastable and fermionic atoms. Condensates have become an ultralow-temperature laboratory for atom optics, collisional physics and many-body physics, encompassing phonons, superfluidity, quantized vortices, Josephson junctions and quantum phase transitions.

Journal Article↗

PubMed2006

Direct observation of the superfluid phase transition in ultracold Fermi gases.

Phase transitions are dramatic phenomena: water freezes into ice, atomic spins spontaneously align in a magnet, and liquid helium becomes superfluid. Sometimes, such a drastic change in behaviour is accompanied by a visible change in appearance. The hallmark of Bose-Einstein condensation and superfluidity in trapped, weakly interacting Bose gases is the sudden formation of a dense central core inside a thermal cloud. However, in strongly interacting gases--such as the recently observed fermionic superfluids--there is no longer a clear separation between the superfluid and the normal parts of the cloud. The detection of fermion pair condensates has required magnetic field sweeps into the weakly interacting regime, and the quantitative description of these sweeps presents a major theoretical challenge. Here we report the direct observation of the superfluid phase transition in a strongly interacting gas of 6Li fermions, through sudden changes in the shape of the clouds--in complete analogy to the case of weakly interacting Bose gases. By preparing unequal mixtures of the two spin components involved in the pairing, we greatly enhance the contrast between the superfluid core and the normal component. Furthermore, the distribution of non-interacting excess atoms serves as a direct and reliable thermometer. Even in the normal state, strong interactions significantly deform the density profile of the majority spin component. We show that it is these interactions that drive the normal-to-superfluid transition at the critical population imbalance of 70 +/- 5 per cent (ref. 12).

Journal Article↗

PubMed1999

Fetal erythropoietin levels in growth-restricted and appropriately grown neonates with and without abnormal fetal heart rate tracings: a comparison with cord blood gases and Apgar scores.

OBJECTIVE: To determine if umbilical cord plasma erythropoietin (EPO) levels in combination with cord blood gases and Apgar scores can distinguish between subacute and chronic uteroplacental insufficiency. METHODS: A total of 184 neonates delivered between 1993 and 1997 at Tampa General Hospital were studied. Cord plasma EPO levels, cord blood gases, and Apgar scores were determined prospectively and compared in four subgroups that were defined based on the presence or absence of fetal growth restriction (FGR; chronic fetal hypoxia), abnormal fetal heart rate tracings during labor (FHR; subacute/acute fetal hypoxia), or both. RESULTS: Both growth-restricted and appropriately grown newborns with abnormal intrapartum FHR tracing had elevated umbilical cord plasma EPO (183.5 and 135.2 mIU/ml, respectively; normal = 20.7 mIU/ml) and base deficit, whereas pH, Po2, and 1-minute and 5-minute Apgar scores were significantly lower, compared with appropriately grown newborns with a normal intrapartum course. Among newborns with normal heart rate tracings and FGR, the mean plasma EPO levels were elevated (89.5 mIU/ml), whereas the other parameters were not different from normal. CONCLUSION: Our findings suggest that, although cord blood gases and Apgar scores may reflect subacute and acute events, they are not good predictors of chronic uteroplacental insufficiency. The supplemental use of umbilical cord plasma EPO levels may improve our ability to identify chronic uteroplacental insufficiency.

Apgar Score↗

PubMed2002

Tumour implantation following laparoscopy using different insufflation gases.

BACKGROUND: Because of the possibility of intraperitoneal seeding and port-site recurrences following laparoscopic surgery, the role of laparoscopy in cancer surgery remains controversial. Previous experimental studies have suggested that chemical, metabolic and immunological changes following carbon dioxide (CO2) insufflation may be responsible for this phenomenon. Earlier experimental studies done by the University of Adelaide Department of Surgery have also shown that helium insufflation is associated with none of the adverse changes brought about by CO2 insufflation. Helium insufflation is also associated with lower rates of intra-abdominal tumour spread. The aim of this study was to determine whether these identified benefits apply to inert gases in general. METHODS: Twenty-four Dark Agouti rats were randomized to undergo laparoscopy with 40 min insufflation using one of the following four gases (six rats in each group); CO2, helium, argon and nitrogen. A tumour cell suspension was injected into the abdominal cavity at the beginning of laparoscopy. The rats were killed 7 days after surgery, and the peritoneal cavity and port sites were examined for the presence of tumour. RESULTS: Rats undergoing helium insufflation, had the least number of port-site recurrences and the least amount of intraperitoneal tumour spread. Argon and nitrogen pneumoperitoneum were associated with a large number of port-site recurrences and widespread tumour seeding. The effect of CO2 insufflation was intermediate. CONCLUSION: The choice of insufflation gas influences the incidence of port-site metastases and the degree of intraperitoneal tumour spread following laparoscopic cancer surgery. The reduced port-site recurrences and intraperitoneal spread that followed helium pneumoperitoneum is likely to be a unique property of this gas rather than a property of inert gases in general.

Adenocarcinoma↗

PubMed1992

Comparison of the effects of dry and liquid heparin on neonatal arterial blood gases.

We compared the effects of liquid and vaporized dry heparin on neonatal arterial blood gases. A total of 35 paired simultaneously drawn neonatal arterial blood samples were collected. In one of every paired sample, 0.05 cc of liquid heparin was used and in the other sample vaporized heparin syringes were used. Blood was drawn into every syringe to a total volume of 0.2 ml, pH, arterial oxygen tension (PaO2), and arterial carbon dioxide tension (PaCO2) of the paired samples were analyzed using the paired Student t method. There was no statistical difference in pH and PaO2 but the PaCO2 was statistically lower (p less than 0.0005) with liquid heparin. We conclude that the effects of heparin on neonatal arterial blood gases is dilutional in nature and that they are due to mixing heparin with its very low PaCO2 with the blood sample. If by mistake more heparin than necessary is used, the effects can be dramatic. We therefore suggest using syringes with vaporized heparin in obtaining neonatal arterial blood gases to obtain reliable and consistent results.

Acidosis↗