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PubMed2000

Awareness due to disconnection from the fresh gas supply: why could ventilation be achieved in spite of disconnection from the fresh gas supply?

An anaesthesia ventilator of to-and-fro type incorporated into the anesthesia machine was used for mechanical ventilation in a patient undergoing plastic surgery under sevoflurane anaesthesia. During operation, elevation of blood pressure and tachycardia, which suggested inadequate anesthesia could not be managed by adjustment of sevoflurane to higher concentrations. However, the patient's lungs could be well ventilated without problems. Close to the end of anaesthesia, a disconnection at the mixed gas common outlet before the check valve of anaesthesia machine was detected. The patient could recall and recount all the happening during the operation signifying that he was not sufficiently anesthetized. In the case that the fresh gas supply line before the check valve is disconnected, the lungs can still be ventilated if a to-and-fro type of ventilator is used. Because there is no leakage of gas from the check valve every bit of the gas which drives the ventilator begins to work and deliver a flow of gas sufficiently to maintain a tidal volume. As a result, anaesthetic gas is replaced by a driving gas. A ventilator of to-and-fro type is still used in clinical anesthesia due to its simple design. The phenomenon reflects the pitfall in the design of a to-and-fro type anaesthesia ventilator.

Adult↗

PubMed2005

[Removal of CO2 from simulated flue gas of power plants by membrane-based gas absorption processes].

Three typical absorbents such as aqueous of aminoacetic acid potassium (AAAP), monoethanolamine (MEA) and methyldiethanolamine(MDEA) are selected to investigate the performance of CO2 separation from flue gas via membrane contactors made of hydrophobic hollow fiber polypropylene porous membrane. Impacts of absorbents, concentrations and flow rates of feeding gas and absorbent solution, cyclic loading of CO2 on the removal rate and the mass transfer velocity of CO2 are discussed. The results demonstrate that the mass transfer velocity was 7.1 mol x (m2 x s)(-1) for 1 mol x L(-1) MEA with flow rate of 0.1 m x s(-1) and flue gas with that of 0.211 m x s(-1). For 1 mol L(-1) AAAP with flow rate of 0.05 m x s(-1) and flue gas of 0.211 m x s(-1), CO2 removal rate (eta) was 93.2 % and eta was 98% for 4 mol x L(-1) AAAP under the same conditions. AAAP being absorbent, eta was higher than 90% in a wider range of concentrations of CO2. It indicates that membrane-based absorption process is a widely-applied and promising way of CO2 removal from flue gas of power plants, which not only appropriates for CO2 removal of flue gas of widely-used PF and NGCC, but also for that of flue gas of IGCC can be utilized widely in future.

Adsorption↗

PubMed1986

Excretion-retention data of steady state gas exchange in tidal breathing. I. Dependency on the blood-gas partition coefficient.

The aim of this study is to investigate the steady state gas transfer properties of the lungs. These properties can be derived from excretion-retention (E-R) data of inert tracer gases that are infused intravenously. E = PE/Pv and R = Pa/Pv, where PE, Pa and Pv represent the partial pressures of the tracer gases in mixed expired gas, arterial blood and mixed venous blood, respectively. In this paper, special attention is paid to the effects of tidal breathing on E-R data sets of tracer gases with different blood-gas partition coefficients. To that end, E-R data sets have been simulated with a lung model that takes into account tidal breathing, the morphometric geometry of the airways, diffusion limited gas mixing and gas dissolved in superficial lung tissue. The simulated E-R data sets are compared with E-R data sets obtained from anaesthetized dogs. Both the simulated E-R data sets and most of the in vivo determined E-R data sets are incompatible with a model description of pulmonary gas transfer with parallel placed compartments with different ventilation-perfusion ratios. Concerning the simulated E-R data sets, this incompatibility is due to the large buffering capacity of lung tissue for highly soluble gases in combination with the within-breath partial pressure oscillations in the airways.

Animals↗

PubMed2000

Response-time enhancement of a clinical gas analyzer facilitates measurement of breath-by-breath gas exchange.

Tidal ventilation gas-exchange models in respiratory physiology and medicine not only require solution of mass balance equations breath-by-breath but also may require within-breath measurements, which are instantaneous functions of time. This demands a degree of temporal resolution and fidelity of integration of gas flow and concentration signals that cannot be provided by most clinical gas analyzers because of their slow response times. We have characterized the step responses of the Datex Ultima (Datex Instrumentation, Helsinki, Finland) gas analyzer to oxygen, carbon dioxide, and nitrous oxide in terms of a Gompertz four-parameter sigmoidal function. By inversion of this function, we were able to reduce the rise times for all these gases almost fivefold, and, by its application to real on-line respiratory gas signals, it is possible to achieve a performance comparable to the fastest mass spectrometers. With the use of this technique, measurements required for non-steady-state and tidal gas-exchange models can be made easily and reliably in the clinical setting.

Algorithms↗

PubMed2000

Gas exchange parameters in radiotherapy patients during breathing of 2%, 3.5% and 5% carbogen gas mixtures.

The gas mixture carbogen may be breathed by patients to enhance the oxygenation level and therefore the radiosensitivity of tumours. However, owing to the high CO2 content, its inhalation is associated with patient intolerance. Our aim was to determine a suitable carbon dioxide and oxygen gas mixture with similar enhancement of arterial oxygenation to 5% carbogen and with improved patient tolerance. 14 patients entered the study; of those 14, 8 were able to tolerate 2%, 3.5% and 5% carbogen mixtures as well as a control gas for sufficient time to allow successful arterial blood gas sampling. Gas exchange parameters were measured using a carbon dioxide monitor and a blood gas analyser. Arterial carbon dioxide tension ranged from 2.9 kPa to 6.82 kPa whilst breathing the carbogen mixtures, and arterial oxygen tension increased at least three-fold from basal values. There were no significant changes in the respiratory rate, heart rate and blood pH. The results suggest that 2% CO2 in O2 enhances arterial oxygen levels to a similar extent as 3.5% and 5% CO2 and that it is well tolerated.

Aged↗

PubMed1993

Intrapulmonary gas mixing and pulmonary gas exchange in artificially ventilated dogs.

To investigate the effect of incomplete gas mixing between tidal air and residual gas on pulmonary gas exchange, anaesthetized dogs were ventilated artificially with breathing patterns with different durations of the post-inspiratory apnoea (ta = 0, 0.5, 1.0 and 2.0 s), where tidal volume, breathing frequency, inspiratory and expiratory flow patterns were kept constant. We determined the alveolar ventilations (VA) of He and SF6 from the product of end-expiratory lung volume (VL,E') and specific ventilation (VA/VL,E'). VL,E' was determined by the dilution technique and the specific ventilations of the two gases were obtained from their multiple-breath washout. Further, tracer amounts of acetone, ether and enflurane were infused continuously into a peripheral vein and a bolus of a gas mixture of krypton, Freon12 and SF6 was introduced into the peritoneal cavity. We determined the Excretion (E) and Retention (R) of these six gases according to the multiple-inert-gas-elimination technique (MIGET). VA increased with increasing ta, where VA,He was about 14% larger than VA,SF6. For both gases, however, the increase in VA relative to control (VA for ta = 0) was virtually the same: 9, 11 and 19% (mean values) for ta = 0.5, 1.0 and 2.0 s respectively. For all dogs the E/R curve shifted to larger E values with increasing ta. E for the most soluble tracer gas (acetone) increased by 11, 21 and 25% for ta = 0.5, 1.0 and 2.0 s respectively. VA, determined with MIGET from the ventilation/perfusion distribution, increased by almost the same percentages.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetone↗

PubMed1987

Gas chromatographic comparison of peptone yeast glucose and gas liquid chromatography growth media for anaerobic bacteria.

The growth media peptone yeast extract glucose broth and gas liquid chromatography broth were compared with respect to their suitability for anaerobic bacteria, using 63 strains belonging to 12 species. After incubation for 24 and 48 h the broth cultures were subjected to viable counts and gas chromatographic analysis of short-chain alcohols and fatty acids in head-space vapours and ether extracts. Head-space analysis was superior to the ether extraction method for detecting the rapidly eluting short-chain alcohols. The gas liquid chromatography medium provided superior growth and contained fewer compounds that interfered with the chromatographic analyses. Whereas incubation in gas liquid chromatography medium for 24 h gave characteristic chromatograms for all but one of the studied species, most species required 48 h of incubation in peptone yeast extract glucose medium. Gas liquid chromatography broth is the preferred substrate for use in gas chromatographic identification of anaerobic bacteria.

Alcohols↗

PubMed1985

Interregional gas mixing and gas transport during high frequency oscillations.

We investigated gas mixing between lung regions and its relationship to gas transport out of the lungs during high frequency oscillation (HFO) in eight, healthy male volunteers. Gas mixing within the lung during HFO was assessed by measuring changes in the regional concentration of 133Xenon with scintillation detectors positioned over the posterior chest, 5, 15 and 25 cm below each lung apex. Gas transport out of the lungs was assessed by measuring changes in 133Xenon concentration at the mouth during HFO. Mixing between topographic lung regions from the apex to base was increased by both the stroke volume (P less than 0.05) and the frequency (P less than 0.05) of HFO. This mixing correlated best with the product of f X SV1.5 (r = 0.99 P less than 0.001). Changes in regional gradient with HFO showed a strong positive correlation with changes in mouth concentration (r = 0.94, P less than 0.025). We conclude that gas mixing between lung regions in man is increased more by stroke volume than frequency during HFO. This mixing is closely related to gas transport out of the lungs.

Adult↗

PubMed1989

Carrier gas flow-rate and injection system in capillary gas chromatography of unconjugated and glycine-conjugated bile acids.

The first description of successful capillary gas chromatography of intact glycine-conjugated bile acid derivatives used an automatic solid injection system and required very high carrier gas flow-rates (approximately 20 ml/min) to obtain satisfactory peak shape. Peak heights of unconjugated bile acid derivatives using this injection system and the low flow-rates (1-2 ml/min) usually used for such gas chromatographic analyses were very susceptible to small changes in flow-rate. This system has been re-examined in an attempt to explain this anomalous behaviour. An alternative injection system, the all-glass dropping needle, was also investigated. No explanation for the very high carrier gas flow-rates required when using the automatic solid injection system was found. The dropping needle injection system, however, produced excellent separation of bile acids and their glycine conjugates as dimethylethylsilyl ethers-methyl esters on non-polar wall-coated capillary columns using normal carrier gas flow-rates of 1-2 ml/min. It is clear that the automatic solid injection system originally used has some problem associated with it which can only be overcome, in the case of bile acids and their glycine conjugates, by increasing the carrier gas flow-rate to very high levels.

Bile Acids and Salts↗

PubMed1997

Simple and rapid determination of enflurane in human tissues using gas chromatography and gas chromatography-mass spectrometry.

A simple, rapid and reliable method was devised to determine the levels of enflurane in human tissues, using gas chromatography and gas chromatography-mass spectrometry. 1,4-Dioxane was used as an internal standard (I.S.). Enflurane and the I.S. were extracted from 0.25 g of body tissues using an automatic headspace sampler and 1 ml of headspace gas was injected into the gas chromatograph. Enflurane was analyzed qualitatively by gas chromatography-mass spectrometry and quantitatively by gas chromatography with a flame-ionization detector. The calibration curves in all tissues examined were linear in the concentration range 1-100 microg/0.25 g. The lower limit of detection was 200-300 ng/0.25 g. The accuracy and precision of this method were evaluated at two different concentrations, 1 and 20 microg/0.25 g. The coefficient of variation ranged from 3.4-13.4%. We used this method to determine the presence of enflurane in tissues from an autopsied individual who died suddenly during extirpation of a malignant tumor.

Anesthetics, Inhalation↗

PubMed2004

Characterization of SnO2 ceramic gas sensor for exhaust gas monitoring of SVE process.

A Figaro-type gas sensor system was investigated for the monitoring of volatile organic contaminants (VOC) in the exhaust gas from a soil vapor extraction (SVE) process. Benzene, toluene, ethyl benzene and xylene (BTEX), and their mixtures, were tested as representative contaminants. Reasonably good correlation factors >0.98 were obtained between the GC analyses and the sensor responses for each component, and for the total gas concentrations. Although the composition of the exhaust gas from SVE process, as well as the amount of each component, change with time, the sensor can be used to estimate the residual amount of contaminants by measuring the total concentrations in the exhaust gas. The sensor can be utilized as a valuable tool for the monitoring of SVE process by indicating when the operation to remediate a contaminated site should be stopped. The proposed ceramic gas sensor system may be a good alternative to existing methods, because it can satisfy the essential monitoring necessities of SVE processes, and has many advantages over other fully equipped instrumentation, as a cost-effective device, with long-term monitoring stability.

Benzene↗

PubMed1999

Determination of Ni(CO)4, Fe(CO)5, Mo(CO)6, and W(CO)6 in sewage gas by using cryotrapping gas chromatography inductively coupled plasma mass spectrometry.

Evidence for the occurrence of Ni(CO)4 in addition to Mo(CO)6 and W(CO)6 in fermentation gases from a municipal sewage treatment plant is presented for the first time. The gases were sampled at the top of the sewage sludge digester using Tedlar bags, and were analysed using cryotrapping followed by gas chromatography coupled with inductively coupled mass spectrometry (GC-ICP-MS). The use of an ICP-MS as an element-specific detector gives sufficiently low detection limits for metals and was coupled to a packed column gas chromatograph. This method provides information about the speciation of volatile transition metals in contrast to previously used methods for the determination of Ni(CO)4 in gas samples. The element-specific detection of three different isotopes (m/z 58, 60, 62) and the correspondence of the samples' retention times with those of the standard provided convincing evidence that Ni(CO)4 is present in the fermentation gas. The concentrations found were in the sub-ppb level, which is at least one order of magnitude lower than the threshold level of 1 ppb (v/v). In addition, Mo(CO)6 and W(CO)6 were also measured in the sub-ppb range in contrast to the absence of Fe(CO)5. The stabilities of Ni(CO)4, Fe(CO)5, and Mo(CO)6 were tested in a carbon monoxide atmosphere. In the presence of distilled water, the following order of stability was found after 11 weeks: Fe(CO)5 < Ni(CO)4 < Mo(CO)6. In the presence of an aqueous solution containing nickel, molybdenum, tungsten and iron, however, only Fe(CO)5 was significantly decomposed (< 0.3% recovery); Ni(CO)4 and Mo(CO)6 were stable after 11 weeks. No W(CO)6 was formed. The low stability of Fe(CO)5 in the presence of water could be the reason why no volatile iron compound was found in sewage gas. This study showed that GC-ICP-MS can be employed to identify species-specific traces of metal carbonyls in process gases such as sewage gas.

Air Pollutants, Occupational↗

PubMed1989

Gas chromatographic determination of volatile anaesthetic agents in blood. Part 1. Preparation of standard gas mixtures of volatile anaesthetic agents.

A method for preparing standard gas mixtures of the volatile anaesthetics halothane, enflurane and isoflurane is described. Static mixtures of gases of known concentration can be prepared manometrically by measuring the required pressure of anaesthetic gas into a bulb and diluting to atmospheric pressure with air. Standard gas mixtures in the concentration range 0-4% V/V can be prepared with an accuracy of +/- 0.01% V/V, and the relative standard error of measurements of a single standard concentration is less than 0.8%. Significant adsorptive losses in the gas sampling valve were observed for gas standards prepared in the absence of any diluent gas. These losses were not detected for measurements of standards made up to atmospheric pressure in air. A comparison with calibration procedures currently in practice is presented.

Anesthetics↗

PubMed1997

[Effectiveness of anesthetic gas scavengers fulfilling EN 740 requirements with reference to equipment leakage and fresh gas flow].

PURPOSE: During inhalation anaesthesia, contaminations of the working environment be anaesthetic volatiles and nitrous oxide occur. The amount of leaking gases is influenced by leakages of the anaesthetic ventilator, by fresh-gas flows and by the effectivity of the scavenging system. Since 1st January 1996 new ventilators have to be equipped with scavenging devices according to the European standard EN 740. We measured the effectivity of this system with anaesthetic ventilators of a type that is now superseded (mean leakage rate 100 ml/min) and recent devices (mean leakage rate 5 ml/min) using high and low fresh-gas flows. MATERIAL AND METHODS: The anaesthetic ventilators were placed in a non-air-conditioned area. A test lung was ventilated with gas flows of 1 l/min, 3 l/min and 6 l/min (concentrations of nitrous oxide 70%, Enflurane 1%). The ventilation time in each case was 1 h. The minute volume was set to 8 l/min. At 2-minute intervals the concentrations of nitrous oxide and enflurane were measured by a multigas monitor Brüel & Kjaer 1302. The experiments were carried out with an old scavenging device according to DIN 13260 and a new device according to EN 740. RESULTS: Using the scavenging device according to DIN 13260, the concentrations of the pollutant gases were significantly dependent on the fresh-gas flows. No differences were found when using old or new anaesthetic ventilators. Medians of nitrous oxide (n2o) and Enflurane (e): 6 l/min: (n2o) 204 ppm (e) 4.3 ppm 3 l/min: (n2o) 115 ppm (e) 2.1 ppm 1 l/min: (n2o) 61 ppm (e) 0.97 ppm. Scavenging devices according to EN 740 significantly reduced the amount of emitted pollutants. No dependency on fresh-gas flows could be detected. 6 l/min: (n2o) 11.25 ppm (e) 0.05 ppm 3 l/min: (n2o) 10.12 ppm (e) 0.0 ppm 1 l/min: (n2o) 9.5 ppm (e) 0.0 ppm. CONCLUSIONS: The formerly reported dependence of the room air concentrations of anaesthetic volatiles and nitrous oxide from the fresh gas flow are caused by the spillage of pollutants through scavenging devices according to DIN 13260. The use of systems according to EN 740 is not only useful in new devices but must also be recommended for superseded models of anaesthetic ventilators.

Air Pollutants, Occupational↗

PubMed1986

Infections of the lower extremities due to gas-forming and non-gas-forming organisms.

From 1977 to 1984, 87 above- and below-knee amputations were done on 77 patients for ischemic ulcerations and gangrene of the lower extremities. The overall three-month mortality was 14% and was mainly related to generalized atherosclerosis. Patients having infections with gas formations were more likely to be diabetic (80% vs 15%, P less than .01), have clinical sepsis and a higher preoperative WBC (19,000 vs 12,600/cu mm, P less than .01), and have a higher mortality (40% vs 12%, P less than .05) than those with infections due to non-gas-forming organisms. Mixed bacterial flora were cultured from most wounds. We conclude that infections with gas formation may be due to either clostridial or nonclostridial organisms, mortality is higher if gas accumulates and if the patient is diabetic, gas is more likely to accumulate in infected extremities of diabetic patients, and the combination of gas formation and diabetes is highly lethal.

Aged↗

PubMed1979

Incorporating the gas analyzer response time in gas exchange computations.

A simple method for including the gas analyzer response time in the breath-by-breath computation of gas exchange rates is described. The method uses a difference equation form of a model for the gas analyzer in the computation of oxygen uptake and carbon dioxide production and avoids a numerical differentiation required to correct the gas fraction wave forms. The effect of not accounting for analyzer response time is shown to be a 20% underestimation in gas exchange rate. The present method accurately measures gas exchange rate, is relatively insensitive to measurement errors in the analyzer time constant, and does not significantly increase the computation time.

Carbon Dioxide↗

PubMed1979

Disopyramide determination by gas chromatography, liquid chromatography, and gas chromatography--mass spectrometry.

Disopyramide is determined in serum by gas chromatography with a nitrogen-selective detector, by liquid chromatography, and by gas chromatography--mass spectrometry. Comparable results are obtained with the three techniques, with a within-run and between-run precision of 5 to 10% (coefficient of variation). Least-squares analysis of data on patients' sera, analyzed first by gas chromatography (y) and then liquid chromatography (x), gave a slope of 1.12; y-intercept, -0.31; standard error of estimate, 0.46; and correlation coefficient, 0.94. Comparison of patients' sera by gas chromatography (y) and then by gas chromatography--mass spectrometry (x) gave a slope of 0.94; y-intercept, 0.42; standard error of estimate, 0.38; and correlation coefficient, 0.97. Interferences observed when using one technique--for example, gas chromatography--can be eliminated by analyzing the sample extract with one of the other techniques.

Chromatography, Gas↗

PubMed1995

Gas composition in Clostridium septicum gas gangrene.

Clostridial gas gangrene (myonecrosis) is a rare but catastrophic condition that usually occurs in patients with underlying diseases. This paper reports a fatal case of spontaneous clostridial gas gangrene in a 60-year-old female diabetic patient. The composition of gas samples from the patient's damaged muscle was analyzed. The results showed 5.9% hydrogen, 3.4% carbon dioxide, 74.5% nitrogen and 16.1% oxygen. This gas composition supports the belief that such gas production occurs via glucose fermentation. This is the first time such an analysis has been performed in a clinical case of spontaneous clostridial gas gangrene.

Clostridium↗