Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “GAS”

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.

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

At least 361 records · Page 20Linked to original sources
PubMed1985

Evaluation of phase correction and low gas density to improve thoracic gas volume measurement.

We investigated two methods of decreasing the error on plethysmographic determinations of thoracic gas volume (TGV) related to cheeks movements during panting maneuvers: lowering gas density in the airways with an 80% He-20% O2 mixture and computing TGV from the in-phase component of the plethysmographic signal (TGVr). The methods were tested by measuring how TGV estimates varied when panting frequency was raised from 0.8 to 2.5 Hz during the same occlusion. The measurements were performed in 6 normal subjects and 12 patients with chronic bronchitis with and without cheeks support and when the airway was connected to an external device simulating an increased cheeks compliance. A small negative frequency dependence of TGV (delta TGV/delta f = -1.2 +/- 0.8%/Hz with cheeks support), most probably unrelated to upper airway walls, was found in normal subjects. Delta TGV/delta f was positive and algebraically larger in patients than in normals, reaching 2.2 +/- 3.4%/Hz without cheeks support and 11.8 +/- 8.0%/Hz with the additional cheeks. The latter value was only 20% smaller when computed on the basis of TGVr, demonstrating the limited usefulness of the phase-based correction. In contrast, breathing He-O2 decreased delta TGV/delta f to approximately 50% of its air value (P less than 0.01) and appears as an effective way to diminish the error in obstructive patients.

Adult↗
PubMed2001

Cyclohexane as an alternative vapor of carbon tetrachloride for the assessment of gas removing capacities of gas masks.

An alternative vapor was explored to replace carbon tetrachloride (CCl4) for testing breakthrough times of cartridges and canisters of gas masks in the National Approval Test of Respirators. Cyclohexane was single out as a candidate for the alternative vapor out of six vapors: trichloroethylene, n-pentane, n-hexane, n-heptane, toluene and cyclohexane from the viewpoints of similarity of vapor pressure and water-solubility to CCl4, lower toxicity than CCl4, and technical feasibility in generating an airflow of 30 L/min containing the vapor ranging from 300 to 5000 ppm. Breakthrough times of cartridges and canisters were examined by generating cyclohexane vapor in a test airflow of 30 L/min in comparison with CCl4 vapor under various test conditions with different vapor concentrations and relative humidities (RH). As the results, the breakthrough times of the cartridges and canisters for cyclohexane were found to almost coincide with those for CCl4 under all examined range of concentrations and RH. By an increase of humidity from 50% RH to 80% RH, the cartridges showed significant shortening of breakthrough times for both of CCl4 and cyclohexane, but the susceptibility of the breakthrough time of cyclohexane to humidity was also similar to that of CCl4. It was, therefore, concluded that cyclohexane can be recommended as the alternative vapor of CCl4 for testing the breakthrough times of gas mask cartridges and canisters in the National Approval Test.

Air Pollutants, Occupational↗
PubMed2001

Medical gas safety. Read the labels! They're the only sure identifier of gas cylinder contents.

Mixing up different types of medical and device gases can have damaging and even deadly consequences. Therefore, it's vital that hospital staff members understand that only the label on a gas cylinder is a reliable indicator of its contents. Any other indicators--such as the type of connector on the cylinder, or the color the cylinder is painted--could be misleading, since the standards covering these indicators sometimes overlap and may be poorly understood. This article discusses how and why the wrong indicators might lead an unsuspecting staff member to use an inappropriate type of gas, and how hospitals can minimize the odds of this happening.

Accident Prevention↗
PubMed1999

[Determination of C1-C5 composition of liquefied petroleum gas by capillary gas chromatography].

In this paper, thirteen C1-C5 hydrocarbons in liquefied petroleum gas were separated and determined by using capillary gas chromatography. The cloumn used was 50 m x 0.53 mm i.d. HP PLOT-Al2O3. A standard mixture of known composition was used for the determination of correction factots and the corrected area mormalization was used for quantification. The relative standard deviations (n = 5) were 0.39%-5.4%. Ethane, ethylene and butene were separated to baseline.

English Abstract↗
PubMed2002

[Determination of natural gas by gas chromatography with external standard-area normalization method].

A GC method for determination of natural gas by external standard-normalization has been established. O2, N2, CH4, CO2, and C2H4 were separated by 13X molecular sieves (1 m x 3 mm i.d., 50 degrees C) connected with PORAPAK T columns (2 m x 3 mm i.d.) in series and detected by TCD and the hydrocarbons of C3 and higher were separated by an SE-30 column (50 m x 0.32 mm i.d.) at 50 degrees C and detected by FID at first. Then O2 + N2 + CH4, CO2 and C2-C5 hydrocarbons were separated on a column (6 m x 3 mm i.d.) with mixed phases of beta, beta'-oxydipropionitrile and dibutyl phthalate at ambient temperature, and detected by TCD. Peak areas from SE-30 column and mixed phase column were correlated with C5, and area normalization was used for quantitative analysis; then normalization correction factors of each component in sample on 13X molecular sieves, PORAPAK T and SE-30 columns were calculated. In analysis, only the first step, area normalization was used for quantitative analysis. The method achieved calibration by SP-6000 Natural Gas Analyzer itself. It is economic, convenient, rapid and accurate.

English Abstract↗
PubMed1990

[The effect of fresh gas flow on the minute volume of anesthesia ventilators with a gas reservoir].

The tidal volume (TV) delivered by conventional anesthesia ventilators is dependent on fresh gas flow rate (FGF). When FGF is reduced, the TV declines; this must be corrected by increasing the ventilator bellows excursion. In addition, the falling bellows produce a negative pressure during the expiratory phase, which may result in positive negative pressure ventilation (PNPV). We have measured the performance of three ventilators: AV 1 (Dräger), VIVOLEC (Hoyer), and ELSA (Engström) that are equipped with a reservoir bag supplied with fresh gas and from which the bellows is filled. METHOD. Two breathing bags with a corrugated tube of 1 m length were connected to a Y-piece to simulate clinical conditions. Starting from 10 l/min, FGF was decreased by 1 l at a time down to 1.0 l/min. Measurements were made at each level of FGF and also at 0.5, 0.3, and 0.2 l/min using a constant inspiration: expiration ratio of 1:2, displacement of the bellows of 700 ml/breath, and a rate of 10/min. Measurements of peak pressure, positive end-expiratory pressure (PEEP), and delivered TV were made at each FGF setting. RESULTS. The course of TV-dependence on FGF is shown in Fig. 1, that of peak inflation pressure and PEEP in Table 1. Reducing FGF had no effect on TV and inflation pressure with ELSA. VIVOLEC lost 17% of the initial TV when FGF was reduced to 0.2 l/min. By closing the relief valve, the loss of TV could be reduced to 4.5%. AV 1 lost about 10% of the initial TV when FGF was reduced to 0.5 l/min. Peak pressure and PEEP were lower with minimal flow. The reservoir bag collapsed when the plateau pressure exceeded 18-20 mbar. CONCLUSIONS. The TV delivered by the ventilators studied was found to reflect closely what had been preset on the bellows displacement scale, within a range of less than or equal to 17%, irrespective of FGF. Hence, the problem of FGF-dependence of TV is largely negated in anesthesia ventilators equipped with a reservoir bag. With ELSA, there was no loss of TV even under minimal flow conditions. VI-VOLEC (with the relief valve closed) and AV 1 had a loss of less than 10% of the initial TV. Adding a reservoir bag to anesthesia ventilators is an effective method of guaranteeing a TV independent of FGF. The three ventilators tested here proved suitable for minimal-flow anesthesia.

Anesthesiology↗
PubMed1977

Gas exchange and arterial blood gas tensions to terbutaline sulfate in older patients with reversible airway obstruction.

Ten patients 55 years and older, known to have chronic obstructive airway disease with reversible component and who had required daily sympathomimetics for many years, were studied. At a clinically stable state in a sitting position, spirometry, ventilation, gas exchange, diffusion and arterial blood gas determinations were performed before and 10, 30, 60 and 120 minutes after administration of 0.5 mg of terbutaline sulfate by inhalation. Although changes were small, significant improvement in FEV1 remained even two hours after inhaling terbutaline. Increase of conducting airways reflected an increase of dead space for 120 minutes. Early rise of alveolar-arterial oxygen tension (PAO2-PaO2) with decreased arterial oxygen tension was observed. This was a transient phenomenon and not severe enough to warrant immediate therapy. No significant EKG or blood pressure changes were noted throughout the study. It appears that terbutaline, an effective long acting bronchodilator, can be safely administered to older patients with bronchospasms.

Aged↗
PubMed1991

Quantitative high-performance liquid chromatographic, gas chromatographic, and gas chromatographic-mass spectrometric analysis of ticlopidine in baboon plasma after solid-phase extraction.

High-performance liquid chromatography with UV detection (HPLC-UV) and gas chromatography with either nitrogen phosphorus (GC-NPD) or mass spectrometry (GC-MS) detection were used for the determination of ticlopidine in plasma. Solid-phase extraction of ticlopidine from plasma was performed using Extrelut columns without pH adjustment, and using hexane as the solvent of elution. With HPLC, a mobile phase of 0.01 M pH 7.8 phosphate buffer:acetonitrile (70:30) was passed through a mu Bondapack C-18 column at a rate of 1.3 mL/min. Ultraviolet detection at 235 nm was sensitive to plasma ticlopidine concentrations of 0.05 micrograms/mL. The GC-NPD and GC-MS were performed on a DB-17 fused-silica column using on-column injection. For GC-NPD and GC-MS, limits of quantification were found to be 0.020 and 0.005 micrograms/mL, respectively. Compared with HPLC-UV, the GC methods were found to be more reproducible, sensitive, and specific and therefore more suitable for pharmacokinetic applications.

Animals↗
PubMed1991

Determination of felodipine and its metabolites in plasma using capillary gas chromatography with electron-capture detection and their identification by gas chromatography-mass spectrometry.

A novel method for the determination of felodipine and its metabolites in plasma by capillary gas chromatography (GC) with electron capture detection was developed. Felodipine and its oxidized metabolite were assayed by capillary GC after solid-phase extraction with the aid of a cool on-column injection technique. Acid metabolites, methyl monoacid and ethyl monoacid and diacid, were extracted with diethyl ether and propylated with 1-n-propyl-3-p-tolyltriazene before being submitted to capillary GC. These methods were very sensitive and useful for the pharmacokinetic study of felodipine. Felodipine and its metabolites were identified by GC-mass spectrometry. The mass spectral patterns of the peaks of extracts from human plasma samples after oral administration of felodipine were in good agreement with those of reference compounds.

Chromatography, Gas↗
PubMed2006

A comparison of a gas chromatographic with electron-capture detection and a gas chromatographic with mass spectrometric detection screening methods for the analysis of famoxadone in grapes and wines.

Famoxadone is a recent oxazolidinedione fungicide widely used in viticulture and in Integrated Pest Management strategies. In this work, after a simple and fast liquid-liquid extraction (LLE), two new gas chromatographic methods were developed to analyze famoxadone residues in grapes and wines, one with electron-capture detection (GC-ECD) and the other with mass spectrometry (GC-MS). Global uncertainties for validation parameters of both methods were compared. Limits of detection (LODs) were 0.06 and 0.02 mg/L, precision was not above 11.7 and 6.8% and recoveries were, on average, 103%+/-12 and 96%+/-12, respectively, for the GC-ECD and GC-MS methods. Similar expanded uncertainties in the range from 0.25 to 1.00 mg/L were below 35%, with increasing values for lower levels of famoxadone. GC-MS method had a lower LOD and a lower uncertainty if compared with the GC-ECD method.

Chromatography, Gas↗
PubMed2000

Gas chromatographic determination of organomercury following aqueous derivatization with sodium tetraethylborate and sodium tetraphenylborate. Comparative study of gas chromatography coupled with atomic fluorescence spectrometry, atomic emission spectrometry and mass spectrometry.

Several hyphenated analytical techniques, including gas chromatography (GC) coupled with atomic fluorescence spectrometry (AFS), microwave-induced plasma atomic emission spectrometry (AES), and mass spectrometry (MS), have been evaluated for methylmercury and ethylmercury analysis following aqueous derivatization with both sodium tetraethylborate and sodium tetraphenylborate. Both GC-AFS and GC-AES were shown to be excellent techniques with detection limits in the range of sub-picogram levels (0.02-0.04 pg as Hg). Both techniques have wide linear ranges, although setting of the AFS sensitivity has to be selected manually based on the concentration of mercury in the sample. Phenylation seems to be more favorable in this study because of its capability of distinguishing between ethylmercury and inorganic mercury, and low cost compared to ethylation. Although sensitivity of GC-MS is poor with detection limits ranging from 30 to 50 pg as Hg, it is an essential technique for confirmation of the derivatization products.

Borates↗
PubMed2000

Comparison of comprehensive two-dimensional gas chromatography and gas chromatography--mass spectrometry for the characterization of complex hydrocarbon mixtures.

In this paper, we compare the current separation power of comprehensive two-dimensional gas chromatography (GCxGC) with the potential separation power of GC-mass spectrometry (GC-MS) systems. Using simulated data, we may envisage a GC-MS contour plot, that can be compared with a GCxGC chromatogram. Real examples are used to demonstrate the current potential of the two techniques in the field of hydrocarbon analysis. As a separation technique for complex hydrocarbon mixtures, GCxGC is currently about as powerful as GC-MS is potentially powerful. GC-MS has not reached its potential separation power in this area, because a universal, soft ionization method does not exist. The greatest advantage of GCxGC is, however, its potential for quantitative analysis. Because flame-ionisation detection can be used, quantitative analysis by GCxGC is much more robust, reliable and reproducible.

Chromatography, Gas↗
PubMed2002

Trace level determination of organochlorine, organophosphorus and pyrethroid pesticides in lanolin using gel permeation chromatography followed by dual gas chromatography and gas chromatography-negative chemical ionization mass spectrometric confirmation.

A methodology for multi-class pesticide determination at trace level in lanolin is presented. Gel permeation chromatography on a Bio-Beads SX-3 column followed by a dual GC chromatographic determination has been developed. The effluent of the analytical column (50% diphenyl-methyl- or 14% cyanopropyl-phenylpolysiloxane) was split into an electron-capture and a nitrogen-phosphorus detection system. The chromatographic system was optimised for 28 pesticides commonly used to control sheep pests and corresponding to organochlorine, organophosphorus and pyretroid classes. Identification has been carried out by gas chromatography coupled to negative chemical ionization mass spectrometry. Recoveries ranged from 72 to 94% and the detection limits from 20 to 97 ng/g depending on the pesticide class, the RSDs were below 10%. Finally, the developed analytical methodology has been successfully applied to the determination of pesticides in several lanolin samples.

Chromatography, Gas↗
PubMed2002

Characterisation of lavender essential oils by using gas chromatography-mass spectrometry with correlation of linear retention indices and comparison with comprehensive two-dimensional gas chromatography.

Nine samples of lavender essential oil were analysed by GC-MS using low-polarity and polar capillary columns. Linear retention indices (LRI) were calculated for each component detected. Characterisation of the individual components making up the oils was performed with the use of an mass spectrometry (MS) library developed in-house. The MS library was designed to incorporate the chromatographic data in the form of linear retention indices. The MS search routine used linear retention indices as a post-search filter and identification of the "unknowns" was made more reliable as this approach provided two independent parameters on which the identification was based. Around 70% of the total number of components in each sample were reliably characterised. A total of 85 components were identified. Semi-quantitative analysis of the same nine samples was performed by gas chromatography (GC) with flame ionisation detection (FID). The identified components accounted for more than 95% of each oil. By comparing the GC-MS results with the results from the GCxGC-FID analysis of a lavender essential oil, many more components could be found within the two-dimensional separation space.

Chromatography, Gas↗
PubMed1996

Application of porous carbon for solid-phase extraction of dicarboxyimide fungicide residues from wines in combination with high-resolution capillary gas chromatography and gas chromatography-mass spectrometry.

Solid-phase extraction with a novel porous carbon sorbent CARB GR was used for the clean-up step of dicarboxyimide fungicides residues from variety of Slovak grape wines with subsequent capillary gas chromatography-flame ionization detection, -electron-capture detection (ECD) and -mass spectrometry-ion-trap detection (MS-ITD) analysis. Recovery was tested at various concentration levels of vinclozolin and iprodione in standard solutions (R = 80-97%, R.S.D. < or = 5). The value of recovery in spiked wines is dependent on concentration level (studied in the range of 5.9 micrograms/1-1.96 mg/l) and on the variety of wine (R = 80-96%; R.S.D. = 3-5%). Limits of quantitation (for sample volume 50 ml) were determined to be with GC-ECD for both fungicides in ppt range and with GC-MS-ITD in the multiple ion detection mode monitoring in ptt range for vinclozolin and ppb range for iprodione. Concentration levels of vinclozolin residues were determined in treated wines (with 0.1% Ronilan 50 WP) as well as iprodione residues (with 0.15% Rovral 50 WP) and a strong dependence on the protective term before the harvest is shown.

Aminoimidazole Carboxamide↗
PubMed1999

Clinical applications of gas chromatography and gas chromatography-mass spectrometry of steroids.

This review article underlines the importance of gas chromatography-mass spectrometry (GC-MS) for determination of steroids in man. The use of steroids labelled with stable isotopes as internal standard and subsequent analysis by GC-MS yields up to now the only reliable measurement of steroids in serum. Isotope dilution GC-MS is the reference method for evaluation of routine analysis of serum steroid hormones. GC-MS is an important tool for detection of steroid hormone doping and combined with a combustion furnace and an isotope ratio mass spectrometer the misuse of testosterone by athletes can be discovered. Finally the so called urinary steroid profile by GC and GC-MS is the method of choice for detection of steroid metabolites in health and disease.

Anabolic Agents↗