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At least 703 records · Page 39Linked to original sources
PubMed1987

[Measuring coronary circulation using an inert gas method--a comparison of common indicator gases].

Validation studies of inert gas techniques are limited in number and usually have not included circumstances with marked heterogeneity of flow. This study was intended to investigate the validity of the method in experimental animals under various hemodynamic conditions by parallel application of helium, argon, krypton and xenon as indicators and by comparison with direct flow measurements. Gases were applied by single breath inhalation. In order to avoid the limitations of conventional methods arising from the systemic recirculation of tracer and from shortened measuring periods we used continuous mass spectrometric recording and numeric deconvolution of the dilution curves in arterial and coronary venous blood. When the transit times are evaluated by "stochastic" analysis and commonly used tissue/blood partition-coefficients (lambda He = 0.95, lambda Ar = 1.1) the helium and argon values are found in reasonable agreement with reference flows. The effects of a shortening of measurements that are based on single integrated samples (Argon method) are shown under control conditions, adenosin infusion and elevated ventricular filling pressure. With xenon (lambda Xe = 0.7) coronary blood flow above 100 ml/min X 100 g is underestimated by the "stochastic" and by the "initial slope technique"; parallel measurements with argon suggest that in the initial slope technique a lambda Xe between 0.8 and 0.9 might be more adequate.

Animals↗
PubMed1977

[Analysis of lung function in workers exposed to irritants and gases].

Interview spirometric, and antrhopometric studies were carried out in 694 men exposed and non-exposed to the effect irritating gases and dusts at their work place, in some subjects symptoms of respiratory system disturbances were found. Results of FEV1 measurement were subjected to an analysis. Average values of FEV1 were considerably lower in persons suffering from dyspnoea and chronic bronchitis with complications. Occupational exposure, particularly to the action of dusts, ammonia, and nitric oxide, and, to a lesser degree, ammonia, only was connected with lowering of FEV1 value. No correlation was found between the exposure to phthalic acid and decreased ventilation efficiency of lungs. Smoking by itself was connected with decreased FeV1 value to the least degree. In the examined group there was joint action of smoking, occupational exposure, and the occurrence of symptoms in respiratory system, inducing a greater decrease in ventilation efficiency of lungs.

Air Pollutants, Occupational↗
PubMed1980

Mass spectrometry in anesthesia. Problems in using mass spectrometer for monitoring anesthetic gases and vapours.

The use of mass spectrometers for total gas monitoring during anesthesia presents a number of problems which stem from the Cracking Pattern of the gases present, inlet design, viscosity variations, water vapour and machine deterioration. Some of these have been adequately solved, by making mechanical modifications to the inlet system, and by using more complex electronic circuitry to process the signals obtained. Remaining problems, however, still limit accuracy and ease of operation. CO2 measurements are particularly prone to error, especially when sampling halothane-containing gas which leads to significant internal production CO2. A study of the principal sources of error remaining in the machine suggests that the only definitive solution is to develop a microprocessor system which could cope with complex Cracking Patterns and non-linearities, and which would allow complete automation of the calibration procedure.

Anesthetics↗
PubMed1982

[Neutral and basic compounds present in gases produced by Clostridium histolyticum, Clostridium hastiforme and Clostridium ghoni cultured under vacuum in sodium thioglycolate glucose broth].

The study of gases produced by Clostridium histolyticum, C. hastiforme and C. ghoni cultured under vacuum in sodium thioglycolate glucose broth makes it possible to detect compounds not described before for these Bacteria, and confirms the production of methane in anaerobic spore-forming Bacteria.

Chemical Phenomena↗
PubMed1982

[Neutral and basic compounds present in gases produced by Clostridium sporogenes, Plectridium putrificum and Plectridium glycolicum cultured under vacuum in sodium thioglycolate glucose broth].

The study of gases produced by Clostridium sporogenes, Plectridium putrificum et P. glycolicum cultured under vacuum in sodium thioglycolate glucose broth makes possible the detection of compounds not described before for these Bacteria, particularly methyl-2 butanal and methyl-3 butanal for P. glycolicum and thiacyclopropane in these 3 Bacteria. Thiacyclopropane is the result of the cyclization of mercapto-2 ethanol produced by the reduction of thioglycolic acid.

Chemical Phenomena↗
PubMed1981

Milk gases, mastitis and milking machines.

Recent studies both in the field and in research laboratories demonstrate that pressure changes within a milk machine system can cause bacteria-laden milk droplets to be introduced into the teat during milking. The injection of milk droplets into the teat cistern by pressure differentials across the teat orifice is dependent upon: dissolved gases in the milk, the level of vacuum, the time the teat is exposed to vacuum after the end point of milking, and the resistance of the teat wall to collapse in response to the internal vacuum space within the teat cistern after milking. Recent evidence using scanning electron microscopy, supported by field studies, demonstrates manufacturing problems of teat cup inflations as they relate to bacteriologic contamination in the environment of the teat. A new approach is needed in mastitis control research to include an independent agency for the evaluation of milking machines as they relate to tissue damage and microbial recontamination of the teat orifice.

Animals↗
PubMed1978

Inhalation lung imaging with radioactive aerosols and gases.

Krypton lung-imaging is considered the ventilation procedure of choice when it is available. Aerosol and krypton wash-in images both reveal regional abnormalities of ventilation, but the aerosol images also disclose evidence of major airways disease. Xenon wash-out images are probably the most sensitive indicators of regional abnormalities of ventilation and/or small airways obstruction, whereas xenon wash-in images are far less sensitive and may be frequently misinterpreted. The Tc-DTPA aerosol inhalation procedure is perferred over xenon and krypton ventilation imaging for routine use immediately after a perfusion examination in pulmonary embolism suspects. This combined method provides the referring physician with the necessary diagnostic information quickly and with around-the-clock availability. In our opinion, this new aerosol procedure deserves wider application in the diagnosis and management of pulmonary disease. Lung imaging procedures, performed after th inhalation of 99mTechnetium labeled aerosols, 133Xenon and and 81mKrypton gases, were used to visualize the sites of airway obstruction and regional abnormalities of ventilatory function in normal volunteers, patients with obstructive airway disease and pulmonary embolism suspects. This chapter presents intercomparisons of these three methods regarding their functional significance, diagnostic merits, and limitations. A new nebulizer-radioaerosol delivery system is described. Test agent kits are inexpensive and readily available for on site assembly. Currently, we consider radioaerosol imaging in multiple views as more informative and suitable for routine use than xenon methods to detect regional abnormalities of the airways and ventilatory function. The krypton procedure is preferred in pulmonary embolism suspects because it requires far less patient cooperation than the xenon and aerosol methods and the lung images disclose regional ventilatory impairment quickly and accurately. However, krypton gas is cyclotron-produced and not yet commercially available.

Adolescent↗
PubMed1995

An "occupational miliary" due to nitrous gases.

The authors report the case of a patient suffering from chemical pneumonia due to nitrous gases of occupational origin which was mistakenly taken for military tuberculosis. Anamnestic, clinical and anatomopathological aspects of this disease, which successively analysed, often make the diagnosis difficult due to their complexity and lack of specificity.

Adult↗
PubMed1994

Gases as biological messengers: nitric oxide and carbon monoxide in the brain.

In a remarkably brief period of time, NO and CO have been recognized as putative neurotransmitters. These two novel messenger molecules have greatly expanded the criteria for candidacy of a chemical for the status of neurotransmitter and our notions about how synaptic transmission takes place. The involvement of NO and CO in several important aspects of neuronal function suggests that agents affecting the synthesis, transactions, and disposition of these gases are bound to have clinical relevance.

Animals↗
PubMed1996

[Determination of concentration and emission of gases relevant to animal and environmental hygiene in different systems for fattening of pigs with the aid of multigas monitoring].

Multigasmonitoring is a method to measure continuously gases relevant from the view point of animal and environmental hygiene with high sampling rate and to calculate emission. The methodical procedure has been described by example from different deep litter systems with additives and slatted floor system with liquid manure storage for fattening pigs. It has been shown that the emission of ammonia from an obviously good working deep litter system can be lowered by approximately 30% in comparison with slatted floor. The mean concentration of nitrous oxide in deep litter system with additives was approximately 2 ppm, whereas in the liquid manure system the N2O concentration was less than the outdoor value.

Air Pollution↗
PubMed1996

A new method for measuring nitrogen and gases in blood.

The authors developed a new apparatus for extracting nitrogen or other inert gases from blood by flushing (sparging) the specimen with another gas. To investigate the utility of the new methodology, the apparatus was used in conjunction with a mass spectrometer to measure the blood N2 content of healthy normobaric, non-smoking, adult volunteers; the mean was found to be 11.7 microliters/ml +/- 0.9 microliter. This compares closely with values cited in the literature. The within-subject variation for repeat samples taken several weeks apart was significantly (P < 0.003) less than the variation between different subjects, suggesting that there may be true differences in N2 content between different individuals. These data must be considered preliminary, a larger study is needed to investigate population differences in detail. The advantages of the new method are discussed.

Adult↗
PubMed1997

Hyperpolarized gases--a new type of MR contrast agents?

The nuclear spin polarization of noble gases can be strongly enhanced by laser optical pumping followed by electron-nuclear polarization transfer. Direct optical pumping of metastable 3He atoms has been shown to produce enormous polarization in the order of 0.4-0.6. This is about 10(5) times greater than the polarization of water protons at thermal equilibrium used at conventional MR imaging. We demonstrate that hyperpolarized 3He gas can be applied to nuclear MR imaging of human organs with air-filled spaces. In vivo 3He MR experiments were performed in a whole-body MR scanner with a superconducting magnet ramped down to 0.8 T and at 1.5 T using a double resonant Helmholtz coil operating at 63.6 and 48.6 MHz for 1H and 3He, respectively. Anatomical details of the lungs of a volunteer were visualized with the FLASH technique demonstrating the potential of the method for fast imaging of airways in the human body and for pulmonary ventilation studies.

Contrast Media↗
PubMed1976

Infrared spectrophotometric analysis of medicinal gases for trace impurities.

The feasibility of examining medical gases for trace impurities, using an infrared spectrophotometer in conjunction with a 10 m gas cell, was investigated. Many of the impurities for which the USP includes limits were detected and measured at concentrations at or below those permitted by the USP; these include sulfur dioxide, carbon dioxide, carbon monoxide, and water. However, others (hydrogen sulfide, nitric oxide, and nitrogen dioxide) were not detected at these levels by this technique. Methane was found at low levels in some samples.

Carbon Dioxide↗
PubMed1991

The ocular effects of gases when injected into the anterior chamber of rabbit eyes.

We studied the toxic effects of sulfur hexafluoride and perfluoropropane in comparison with air, balanced salt solution, hyaluronate sodium, and aqueous humor in a rabbit model. Sixty normal pigmented rabbits were studied during a period of 4 weeks. The variables studied were slit-lamp biomicroscopic examination of the anterior segment, intraocular pressure as measured by pneumotonometry, corneal thickness and endothelial cell count as measured by specular microscopy, lens opacity by Scheimpflug photography, and light and transmission electron microscopy. All three gases were more toxic to the cornea and lens than were balanced salt solution, hyaluronate, and aqueous humor. However, 15% perfluoropropane and 50% sulfur hexafluoride were no more toxic to the eye than air was. Therefore, this study suggests that nonexpansile mixtures of perfluoropropane and sulfur hexafluoride may be beneficial and relatively safe in re-forming persistently flat anterior chambers in situations where the use of air is being considered.

Air↗
PubMed1993

Corneal surface morphology following excimer laser ablation with humidified gases.

OBJECTIVE: To compare the effects of blowing dry (nitrogen or helium) and humidified gases over the corneal surface during photorefractive keratectomy. METHODS: Excimer laser myopic ablations were performed on porcine eyes (10 per group) using humidified and dry nitrogen and helium gas under ambient conditions. Surface smoothness was quantified with light and electron microscopy. RESULTS: Corneas that were ablated using humidified gas were smooth and equivalent to those ablated under ambient conditions. Dry nitrogen and helium blowing resulted in increased surface irregularity evident on light and electron microscopy (P < .001). The pseudomembranes in the humidified gas and ambient air groups had fewer surface discontinuities than did those in the nonhumdified gas groups and appeared to have a thinner electron-dense surface layer. CONCLUSIONS: The blowing of humidified gas during excimer laser corneal ablation produces a smoother surface than does the blowing of dry gas and is comparable to that produced under ambient (no blowing) conditions. Maintaining corneal moisture is important in photorefractive keratectomy. If blowing gas is necessary to remove debris from the surface, the gas should be humidified.

Animals↗
PubMed2000

Influence of water vapour on selected ion flow tube mass spectrometric analyses of trace gases in humid air and breath.

Selected ion flow tube mass spectrometry (SIFT-MS) detects and quantifies in real time the trace gases, M, in air/breath samples introduced directly into a flow tube. Inevitably, relatively large partial pressures of water vapour are introduced with the sample and the water molecules become involved in the ion chemistry on which this analytical technique depends. When H(3)O(+) ions are used as the precursors for chemical ionisation and SIFT mass spectrometric analyses of M, they generally result in the formation of MH(+) ions. Also, when water vapour is present the H(3)O(+) ions are partially converted to hydrated hydronium ions, H(3)O(+).(H(2)O)(1,2,3). The latter may act as precursor ions and produce new product ions like MH(+).(H(2)O)(1,2,3) via ligand switching and association reactions. This ion chemistry and the product ions that result from it must be accounted for in accurate analyses by SIFT-MS. In this paper we describe the results of a detailed SIFT study of the reactions involved in the quantification of acetone, ethyl acetate, diethyl ether, methanol, ethanol, ammonia and methyl cyanide by SIFT-MS in the presence of water vapour. This study was undertaken to provide the essential data that allows more accurate analyses of moist air and breath by SIFT-MS to be achieved. It is shown using our standard analysis procedure that the error of SIFT-MS quantification caused by the presence of water vapour is typically 15%. An improved analysis procedure is then presented that is shown to reduce this error to typically 2%. Additionally, some fundamental data have been obtained on the association reactions of protonated organic molecules, MH(+) ions, with water molecules forming MH(+).H(2)O monohydrate ions. For some types of M, reaction sequences occur that lead to the formation of dihydrate and trihydrate ions.

Air↗
PubMed1992

Serum electrolytes and capillary blood gases in the management of hypertrophic pyloric stenosis.

The purpose of this study was to assess whether the concentration of serum chloride and other variables, namely serum sodium, potassium and bicarbonate, can be used to predict metabolic acid-base status in infants with hypertrophic pyloric stenosis (HPS) and to assess whether such a prediction is influenced by the state of hydration. One hundred and sixty-three infants with HPS who had at least one set of serum electrolyte and capillary blood gas estimations performed after admission were studied retrospectively. A further 25 infants who had their electrolyte and blood gases measured after at least 12 h of rehydration and correction of the serum sodium and chloride abnormalities were studied prospectively. Stepwise multiple regression analysis, using standard bicarbonate as the dependent variable, revealed serum chloride concentration to be the most powerful independent predictor of standard bicarbonate level (r = -0.69, P less than 0.0001). Other variables did not improve the correlation significantly. In the retrospective study of untreated patients, the calculation of a 90 per cent prediction interval for the model indicated that if the serum chloride level is less than 96 mmol/l, one could be 95 per cent confident (one tail) that the patient was alkalaemic. To be 95 per cent confident that the patient was not alkalaemic, the serum chloride level would have to be greater than 121 mmol/l. The prospective study found that following rehydration a serum chloride level greater than or equal to 106 mmol/l more accurately predicted absence of alkalaemia. We conclude that predictability of acid-base status from measurement of serum chloride depends on the state of hydration of the patient.

Acid-Base Imbalance↗