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At least 127 records · Page 7Linked to original sources
PubMed2004

Three cases of sudden death due to butane or propane gas inhalation: analysis of tissues for gas components.

We report three cases of sudden death due to inhalation of portable cooking stove fuel (case 1), cigarette lighter fuel (case 2), and liquefied petroleum gas (LPG) (case 3). Specimens of blood, urine, stomach contents, brain, heart, lung, liver, kidney, and fat were collected and analyzed for propylene, propane, isobutane, and n-butane by headspace gas chromatography. n-Butane was the major substance among the volatiles found in the tissues of cases 1 and 2, and propane was the major substance in case 3. A combination of the autopsy findings and the gas analysis results revealed that the cause of death was ventricular fibrillation induced by hard muscle exercise after gas inhalation in cases 1 and 2, and that the cause of death in case 3 might be hypoxia. It is possible that the victim in case 3 was under anesthetic toxicity of accumulated isobutane which is a minor component of liquefied petroleum gas.

Adipose Tissue↗
PubMed2001

Effect of efficiency improvement by injecting a sample at a lower carrier gas velocity in isothermal gas-liquid chromatography.

The effect of efficiency improvement of chromatographic system by injecting a sample at a lower carrier gas velocity (in comparison with the carrier gas velocity at subsequent separation) was studied experimentally and theoretically in isothermal gas-liquid chromatography. The suggested technique is based on sample introduction in the programmed carrier gas velocity operation mode: the injection is realized at low carrier gas velocity, then the velocity is increased rapidly up to the operation value. The technique can be applied in chromatographic practice.

Chromatography, Gas↗
PubMed2006

Analysis of the gas phase of cigarette smoke by gas chromatography coupled with UV-diode array detection.

A gas chromatography method, coupled with diode array photometric spectral detection in the ultraviolet region (167-330 nm), was developed for the analysis of the gas phase of cigarette smoke. The method enabled us to identify more than 20 volatiles present in the vapor phase of cigarette smoke. In that way, all major volatile organic compounds (including aldehydes, conjugated dienes, ketones, sulfides, furans, and single-ring aromatics), as well as nitric oxide (NO) and hydrogen sulfide (H(2)S), can be analyzed in a straightforward manner through a single chromatographic run of <50-min duration. The method can easily be applied by the introduction of a small volume of the gas-phase stream into the GC injection loop directly through the smoking apparatus exhaust circuit, thus providing an excellent alternative to available methods, which usually require extraction or concentration steps prior to any chromatographic analysis. Furthermore, all problems concerning aging of the gas phase are eliminated. Twelve compounds (including NO) were chosen for quantification through the use of appropriate calibration standards. Comparison of the vapor phase yields of these compounds for the reference cigarette Kentucky 1R4F with already reported data indicates that this method is very reliable as far as accuracy and reproducibility of the results are concerned. Finally, the proposed methodology was used to compare the concentration of these cigarette smoke gas-phase constituents among individual puffs.

Chromatography, Gas↗
PubMed1990

Analysis of 1,3-butadiene and other selected gas-phase components in cigarette mainstream and sidestream smoke by gas chromatography-mass selective detection.

An analytical procedure was developed for the analysis of 1,3-butadiene, acrolein, isoprene, benzene and toluene in the gas phase of cigarette smoke and environmental tobacco smoke (ETS) utilizing cryogenic gas chromatography-mass selective detection (GC-MSD). The MSD was operated in the selective ion monitoring (SIM) mode. The compounds of interest eluted in less than 15 min. The gas phase of freshly generated mainstream smoke was introduced into the GC-MSD via a 10-port gas sampling valve on a puff-by-puff basis. This method minimizes the ageing of tobacco smoke. The levels of 1,3-butadiene in the mainstream smoke ranged from 16 to 75 micrograms/cigarette. The gas phase of sidestream smoke was trapped in methanol using three midget impingers at -78 degrees C. The amount of 1,3-butadiene in the sidestream smoke ranged from 205-361 micrograms/cigarette. The concentration of 1,3-butadiene in ETS in a smoke-filled bar amounted to 2.7-4.5 micrograms/m3.

Acrolein↗
PubMed1997

A non-rebreathing coaxial anaesthesia system: dependence of end-tidal gas concentrations on fresh gas flow and tidal volume.

A non-rebreathing adaptation of the Bain coaxial anaesthesia circuit was developed in Nepal as a simple and economical anaesthetic system for underdeveloped countries. It was made by inserting a coaxial (Bain) tubing between an Ambu-E valve and an Ambu self-inflating bag. The present study examined the dependence of end-tidal gas concentrations on fresh gas flow and tidal volume during halothane/oxygen/air inhalation anaesthesia. Four levels of fresh gas flow with normocapnia (0.2-3 l.min-1) and three levels of tidal volume at a constant respiratory rate of 15 breath.min-1 (to achieve end-tidal carbon dioxide values of 4 +/- 0.5%, 5 +/- 0.5% and 6 +/- 0.5%) were introduced in random order. Twelve ASA class 1 and 2 adult patients having intra-abdominal or pelvic surgery were studied. With increasing fresh gas flow rates, there were proportionate increases in the end-tidal concentrations of oxygen and halothane; with decreasing tidal volume and therefore less air dilution, there were proportionate increases in the end-tidal concentrations of carbon dioxide, oxygen and halothane. Both effects were statistically and clinically significant. Thus, when this system is used as described, the end-tidal concentrations of oxygen and halothane are highly dependent upon both the fresh gas flow and the tidal volume.

Adult↗
PubMed1975

A new gas lesion syndrome in man, induced by "isobaric gas counterdiffusion".

Normal men have been found to develop pruritus and gas bubble lesions in the skin, and disruption of vestibular function, when breathing nitrogen or neon with oxygen while surrounded by helium at increased ambient pressure. This phenomenon, which occurs at stable ambient pressures, at 1 or many ATA, has been designated the "isobaric gas counterdiffusion syndrome." In a series of analyses and experiments in vivo and in vitro the cause of the syndrome has been established as due to gas accumulation and development of gas bubbles in tissues as a result of differences in selective diffusivities, for various respired and ambient gases, in the tissue substances between capillary blood and the surrounding atmosphere. The phenomenon here described in man is an initial stage of a process shown later in animals to progress to continuous, massive, lethal, intravascular gas embolization.

Atmosphere Exposure Chambers↗
PubMed2002

Distal projection of insufflated gas during tracheal gas insufflation.

Tracheal gas insufflation (TGI) flushes expired gas from the ventilator circuitry and central airways, augmenting CO2 clearance. Whereas a significant portion of this washout effect may occur distal to the injection orifice, the penetration and mixing behavior of TGI gas has not been studied experimentally. We examined the behavior of 100% oxygen TGI injected at set flow rates of 1-20 l/min into a simulated trachea consisting of a smooth-walled, 14-mm-diameter tube. Models incorporating a separate coaxial TGI injector, a rough-walled trachea, and a bifurcated trachea were also studied. One-hundred percent nitrogen, representing expiratory flow, passed in the direction opposite to TGI at set flow rates of 1-25 l/min. Oxygen concentration within the "trachea" was mapped as a function of axial and radial position. Three consistent findings were observed: 1) mixing of expiratory and TGI gases occurred close to the TGI orifice; 2) the oxygenated domain extended several centimeters beyond the endotracheal tube, even at high-expiratory flows, but had a defined distal limit; and 3) more distally from the site of gas injection, the TGI gas tended to propagate along the tracheal wall, rather than as a central projection. We conclude that forward-directed TGI penetrates a substantial distance into the central airways, extending the compartment susceptible to CO2 washout.

Carbon Dioxide↗
PubMed1993

Modes of tracheal gas insufflation. Comparison of continuous and phase-specific gas injection in normal dogs.

Tracheal gas insufflation (TGI) improves the efficiency of CO2 elimination accomplished by conventional mechanical ventilation, primarily by reducing the anatomic (series) dead space volume. Dead space proximal to the catheter tip can be reduced by two methods. Fresh gas introduced at the carinal level during inspiration may effectively "bypass" the upper airway. Alternatively, proximal dead space can be "washed out" with fresh gas during expiration to reduce CO2 rebreathing. We examined these two modes of TGI-aided dead space reduction in nine paralyzed normal dogs receiving conventional mechanical ventilation and compared these results to those obtained with a catheter that delivered fresh gas continuously at the same flow rate, thereby accomplishing both bypass and washout. Total inspired tidal volume and cycling frequency were held constant. Differences in CO2 elimination efficiency among the TGI modes were flow dependent. Continuous catheter flow at 5 or 10 L/min reduced PaCO2 and physiologic dead space fraction (VD/VT) more than either proximal bypass or end-expiratory washout (p < 0.001). At the same catheter flow settings expiratory washout tended to improve VD/VT more than did inspiratory bypass. Under the conditions tested, constant tracheal insufflation of fresh gas improves alveolar ventilation by mechanisms that include, but are not limited to, a functional reduction in the dead space proximal to the catheter tip.

Analysis of Variance↗
PubMed2006

The effect of tracheal gas insufflation on gas exchange efficiency.

Transtracheal gas insufflation (TGI) improves gas exchange efficiency, but is associated with hyperinflation, and usually requires ventilator adjustment to compensate for the increased gas flow. Although bidirectional TGI (Bi-TGI) minimizes hyperinflation, it does not preclude the need to reduce tidal volumes to prevent hyperinflation. A flow-compensation system was developed by Respironics (Murrysville, PA) to match TGI flows; however, neither that nor the efficacy of Bi-TGI have been tested in vivo. We tested the hypotheses that flow compensation allows for a constant minute ventilation; Bi-TGI produces less hyperinflation than does unidirectional TGI (Uni-TGI), and endotracheal tube size influences the degree of hyperinflation during TGI. Seven anesthetized intact dogs were studied during positive-pressure ventilation using the Respironics flow compensation system. Measurements were made during steady-state conditions at constant and measured levels of CO(2) production. Gas exchange efficiency (assessed by expired gas analysis for dead space) and hyperinflation (measured as an increase in pleural pressure) were compared during Bi- and Uni-TGI and for endotracheal tube sizes varying from 7 to 10F. Bi- and Uni-TGI could be delivered at constant minute ventilation without adjusting ventilatory setting when the flow compensation circuit was present. Uni-TGI produced more hyperinflation than did Bi-TGI with all sizes of endotracheal tube, and hyperinflation was universally present as tube size decreased to 7.5F. We conclude that this new flow compensation system allows for the delivery of TGI without the need for adjustments to the ventilator settings, and that Bi-TGI produces less hyperinflation than does Uni-TGI, even with small diameter endotracheal tubes.

Animals↗
PubMedDate not supplied

Gas chromatographic analysis and storage of gas samples from the middle ear.

Methods for storage and analysis of gas samples were studied prior to measuring the composition of gas in the human middle ear cavity. Storage and analysis of gas samples are beset with several pitfalls. The dead space of the sampling syringe must be considered and the gas sample can equilibrate with the surrounding atmosphere, especially if the analysis cannot be done immediately. In this study the equilibration rate was found to fit an exponential function with a time constant of 0.004 min-1. The time constant was reduced by more than a factor of ten when butyl rubber stoppers were used to seal the syringes. Silicone rubber stoppers were less efficient. Disposable plastic syringes were found just as efficient as 'gas-tight' syringes.

Chromatography, Gas↗
PubMed1981

Blood-gas analyzer calibration and quality control using a precision gas-mixing instrument.

We describe a new instrument that performs on-site mixing of oxygen (O2), carbon dioxide (CO2), and nitrogen (N2) to create compositions that can replace gases from standard premixed cylinders. This instrument yields accurate and predictable gas mixtures that can be used for two-point gas calibration of blood gas/pH analyzers or for liquid tonometry of either an aqueous buffer or blood used as quality-control material on blood-gas electrodes. The desired mixture of O2, CO2, and N2 is produced by microprocessor control of the sequential open-times on three solenoid valves that meter these pure gases through a common small-bore orifice. Any combination of O2 and CO2 can be chosen by dialing the front panel thumbwheels and pressing a button. Gas chromatographic evaluation of this gas-mixing instrument demonstrates its accuracy and precision to be better than +/- 0.1% absolute full scale for O2, CO2, and N2, making this instrument calibration and tonometry.

Blood Gas Analysis↗
PubMed1997

Considerations about the Adsorption of Organic Molecules from the Gas Phase to Surfaces: Implications for Inverse Gas Chromatography and the Prediction of Adsorption Coefficients

Whether surfaces are characterized from experimental gas-phase adsorption coefficients of probe molecules with known properties (as is done in inverse gas chromatography (IGC)) or whether adsorption coefficients are to be predicted from known properties of the adsorbate and the adsorbent (as is desirable in environmental chemistry) in both cases a correct quantitative description of the van der Waals and acid-base interactions of organic molecules at surfaces is necessary. The model used to date in IGC for the van der Waals interactions tacitly assumes that the interactions of a dilute gas with a surface can be treated like the interactions between two condensed phases. This only works if the contact area of the adsorbed molecule is treated as an adjusted parameter which makes up for the occurring discrepancies. In this paper an improved equation for the van der Waals interactions will be suggested which works without adjusted parameters. For describing acid-base interactions of dilute gases at surfaces Gutmann's donor and acceptor numbers have found wide use in the IGC literature. However, these parameters are related to the heats of the acid-base interactions rather than the free energies. Thus this approach has the disadvantage of putting the acid-base characterization of surfaces in IGC on a different basis than the van der Waals characterization, and it also does not allow the prediction of gas-phase adsorption coefficients. Here, a different approach will be discussed that was originally introduced by van Oss and coworkers for the acid-base interactions between condensed phases (1). This approach uses acceptor and donor parameters that are free energy related. Validation with experimental data from the literature shows a good performance of the equations introduced in this paper for IGC purposes as well as for the prediction of gas-phase adsorption coefficients.

Journal Article↗
PubMed1991

The effects of composition of subarachnoid gas space and anesthetic gas mixture on cerebrospinal fluid pressure changes during cisternography for transsphenoidal craniectomy.

The effects of gas composition in the subarachnoid space (injection of air or N(2)O) and in an anesthetic gas mixture (inhalation with or without N(2)O) on cerebrospinal fluid pressure were studied in 22 patients with pneumocisternography for transsphenoidal craniectomy. N(2)O (66%) anesthesia for 10 min increased cerebrospinal fluid pressure by up to 150% in 7 patients who were intrathecally injected with air. Withdrawal of N(2)O from the anesthetic gas mixture for sixty minutes reduced cerebrospinal fluid pressure to the initial pressure. A second N(2)O administration to the anesthetic gas mixture did not elevate cerebrospinal fluid pressure by as much as the first N(2)O administration. In 7 patients receiving subarachnoid air injection, replacing 66% N(2)O with 66% nitrogen prevented the change in cerebrospinal fluid pressure throughout the operation. In 8 patients N(2)O anesthesia and N(2)O intrathecal injection failed to eliminate the rise in cerebrospinal fluid pressure in 8 patients. Withdrawal of N(2)O from the anesthetic gas mixture for 60 min is recommended to prevent an extreme increase in cerebrospinal fluid pressure during pneumocisternography.

Journal Article↗
PubMed2004

Effect of 1.7 MHz ultrasound on a gas-vacuolate cyanobacterium and a gas-vacuole negative cyanobacterium.

Ultrasonic signals propagated through medium were directly applied to unicellular cyanobacterium cell surfaces to investigate the biological effects induced by ultrasound. The gas-vacuolate cyanobacterium Microcystis aeruginosa and the gas-vacuole negative cyanobacterium Synechococcus PCC 7942 responded differently to ultrasound. When M. aeruginosa was irradiated by 1.7 MHz ultrasound at 0.6 W cm(-2) every day, it showed a decrease of nearly 65% in biomass increment, and this group's generation time increased twice as much as the control. While Synechococcus culture irradiated every day still grew as fast as the control, and its final biomass was as much as the control. The value of the electric conductivity change (Deltasigma) sharply increased in Microcystis suspension during the exposure process, which revealed more ultrasonic cavitation yield in liquid related to the gas-vacuolate cyanobacteria. The relative malondialdehyde (MDA) content, a quantitative indicator of lipid peroxidation, increased by 65% in Microcystis cells and 9% in Synechoccus cells after ultrasonic irradiation. Moreover, the membrane permeability, quantified by measuring the relative amount of electrolyte leaking out of cells, increased to more than 60% in the Microcystis cells. The results indicated that Microcystis cells were susceptible to ultrasonic stress. According to Rayleigh-Plesset's bubble activation theory, 1.7 MHz ultrasound approached the eigenfrequency of gas-vacuolate cells. The present investigation suggested the importance of the cavitational effect relative to intracellular gas-vacuoles in the loss of cell viability. In summary, 1.7 MHz ultrasonic irradiation was effective in preventing water-bloom forming cyanobacteria from growing rapidly due to changes in the functioning and integrity of cellular and subcellular structures.

Biomass↗
PubMed1997

Incineration of biomass and utilization of product gas as a CO2 source for crop production in closed systems: gas quality and phytotoxicity.

This study addressed the recycle of carbon from inedible biomass to CO2 for utilization in crop production. Earlier work identified incineration as an attractive approach to resource recovery from solid wastes because the products are well segregated. Given the effective separation of carbon into the gaseous product stream from the incinerator in the form of CO2 we captured the gaseous stream produced during incineration of wheat inedible biomass and utilized it as the CO2 source for crop production. Injection rate was based on maintenance of CO2 concentration in the growing environment. The crop grown in the closed system was lettuce. Carbon was primarily in the form of CO2 in the incinerator product gas with less than 8% of carbon compounds appearing as CO. Nitrogen oxides and organic compounds such as toluene, xylene, and benzene were present in the product gas at lower concentrations (< 4 micromol mol-1); sulfur containing compounds were below the detection limits. Direct utilization of the gaseous product of the incinerator as the CO2 source was toxic to lettuce grown in a closed chamber. Net photosynthetic rates of the crop was suppressed more than 50% and visual injury symptoms were visible within 3 days of the introduction of the incinerator gas. Even the removal of the incinerator gas alter two days of crop exposure and replacement with pure CO2 did not eliminate the toxic effects. Both organic and inorganic components of the incinerator gas are candidates for the toxin.

Air Pollutants↗
PubMed2000

Local overall volumetric gas-liquid mass transfer coefficients in gas-liquid-solid reversed flow jet loop bioreactor with a non-Newtonian fluid.

The local overall volumetric gas-liquid mass transfer coefficients at the specified point in a gas-liquid-solid three-phase reversed flow jet loop bioreactor (JLB) with a non-Newtonian fluid was experimentally investigated by a transient gassing-in method. The effects of liquid jet flow rate, gas jet flow rate, particle density, particle diameter, solids loading, nozzle diameter and CMC concentration on the local overall volumetric gas-liquid mass transfer coefficient (K(L)a) profiles were discussed. It was observed that local overall K(L)a profiles in the three-phase reversed flow JLB with non-Newtonian fluid increased with the increase of gas jet flow rate, liquid jet flow rate, particle density and particle diameter, but decreased with the increase of the nozzle diameter and CMC concentration. The presence of solids at a low concentration increased the local overall K(L)a profiles, and the optimum of solids loading for a maximum profile of the local overall K(L)a was found to be 0.18x10(-3)m(3) corresponding to a solids volume fraction, varepsilon(S)=2.8%.

Journal Article↗
PubMed2005

Gas transport below artificial recharge ponds: insights from dissolved noble gases and a dual gas (SF6 and 3He) tracer experiment.

A dual gas tracer experiment using sulfur hexafluoride (SF6) and an isotope of helium (3He) and measurements of dissolved noble gases was performed at the El Rio spreading grounds to examine gas transport and trapped air below an artificial recharge pond with a very high recharge rate (approximately 4 m day(-1)). Noble gas concentrations in the groundwater were greater than in surface water due to excess air formation showing that trapped air exists below the pond. Breakthrough curves of SF6 and 3He at two nearby production wells were very similar and suggest that nonequilibrium gas transfer was occurring between the percolating water and the trapped air. At one well screened between 50 and 90 m below ground, both tracers were detected after 5 days and reached a maximum at approximately 24 days. Despite the potential dilution caused by mixing within the production well, the maximum concentration was approximately 25% of the mean pond concentration. More than 50% of the SF6 recharged was recovered by the production wells during the 18 month long experiment. Our results demonstrate that at artificial recharge sites with high infiltration rates and moderately deep water tables, transport times between recharge locations and wells determined with gas tracer experiments are reliable.

Environmental Monitoring↗
PubMed2002

A direct comparison of amperometric gas sensors with gas-diffusion and ion-exchange membrane based electrodes.

The effect of the nature of the working electrode used in amperometric gas sensors on the performance criteria of sensitivity, detection limit, gas flow rate and humidity dependence was evaluated. The arrangement based on metallized ion-exchange membranes (Nafion) was compared with gas-diffusion electrodes based on porous poly(tetrafluoroethylene) (PTFE) with metallic electrodes deposited on the rear side. Two representative analyte gases were chosen: SO2, which has fast reaction kinetics, and NO, which has slow reaction kinetics. It was found that both types of electrodes showed a similar performance. A dependence on the flow rate of the sample gas was found in both cases. The sensitivities were higher for the ion-exchange membrane-backed electrodes; however, the 3sigma detection limits were all in the lower ppb range and for NO were significantly lower on the Nafion membrane than on the PTFE membrane. The Nafion electrode was found to show a dependence on the relative humidity of the gas stream, but not the PTFE-based electrode.

Journal Article↗