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At least 811 records · Page 45Linked to original sources
PubMed1999

Changes in respiratory pattern and arterial blood gases during sedation with propofol or midazolam in spinal anesthesia.

STUDY OBJECTIVE: To investigate changes in respiratory pattern and arterial blood gases during sedation with propofol or midazolam in spinal anesthesia. DESIGN: Randomized, placebo-controlled study. SETTING: Operating room of a university-affiliated hospital. PATIENTS: 40 ASA physical status I and II patients who required spinal anesthesia. INTERVENTIONS: Spinal anesthesia with tetracaine and subsequent sedation with propofol (n = 15), midazolam (n = 15), or placebo (n = 10) was performed. MEASUREMENTS: Respiratory pattern [rib cage contribution to the tidal volume (%RC) and phase shift between rib cage and abdominal movements (PSrc-ab)] with a respiratory inductive plethysmograph (Respigraph) and arterial blood gas analysis (pH, pO2, and pCO2) were recorded. MAIN RESULTS: Spinal anesthesia per se increased %RC by 35% without changing PSrc-ab values (1.00). Sedation with propofol and midazolam decreased %RC by 60% and by 40%, respectively. PSrc-ab increased in both groups following sedation, and the increase in this parameter was higher in the propofol group (1.12) than in the midazolam group (1.04). In the placebo group, %RC decreased by 20% without any change in PSrc-ab. The decrease in pO2 was more significant in the propofol group (65.1 mmHg) than in the midazolam (74.2 mmHg) and placebo (83.1 mmHg) groups. CONCLUSION: Significant decreases in %RC and pO2 during propofol sedation seem to depend on paradoxical respiration due, in part, to upper airway obstruction; therefore, attention should be directed to the respiratory pattern during sedation, especially with propofol.

Adult↗
PubMed1996

The effect of a time delay on the measurement of capillary blood gases.

Patients using domiciliary nasal ventilation, or long-term oxygen, require regular assessment which could be carried out in the home. Blood gas analysis may be regarded as an essential part of the assessment. The present study investigated the effect of a 1-h time delay on the measurement of capillary blood gases. Four samples of arterialized earlobe blood were collected from 15 outpatients. One sample was analysed immediately, the other three were stored on crushed ice and analysed at intervals of 30, 45, and 60 min post-collection. In order to examine any range effect, a wide range of PaO2 values were examined. The delay, at all levels, resulted in minor changes in the measurement of PaO2, which would be unlikely to alter clinical management. The technique might be used for the reliable assessment of patients in the home.

Blood Gas Analysis↗
PubMed1998

Clinical factors that affect blood gases in non-smoking women with chronic liver disease.

Chronic liver disease is often accompanied by hypoxaemia. We investigated the clinical factors that were related to the arterial oxygen tension (PaO2) in 40 women, all non-smokers with chronic liver disease. They were positive for hepatitis C virus (HCV) antibody and had no evidence of cardiopulmonary disease. Arterial blood was collected from patients at rest (> 15 min) for analysis of blood gases. We determined the correlation between blood gas tension and the clinical variables, i.e. the presence or absence of skin manifestations such as cutaneous spider nevi and palmar erythema, the presence or absence of splenomegaly, vital capacity, forced expiratory volume in one second, V25/body height, serum alanine aminotransferase (AST), serum asparate aminotransferase (ALT), serum cholinesterase, serum gamma-globulin/total protein, excretion of indocyanine green at 15 min (15-min retention rate, ICG level), blood level of ammonia, blood level of endotoxin, plasma level of glucagon and the serum level of type IV collagen-7S. The mean level of PaO2 was 78 +/- 11 (range: 43-95) torr. The mean alveolar-arterial oxygen tension gradient (A-aDO2) was 19 +/- 13 (range: 2-60) torr. Multiple regression analysis used PaO2 and A-aDO2 as objective variables, and the clinical findings as explanatory variables. The explanatory variables that were significantly correlated with blood gas values were ICG level, blood level of endotoxin and presence of skin manifestations. The ICG level showed a high correlation with blood gas values; the ICG level increased, the PaO2 decreased (r = -0.69), while the A-aDO2 showed a high positive correlation (r = +0.78, P < 0.001). Findings suggest that a reduction in hepatic blood flow and hepatocellular function interfere with the inactivation of vasoactive substances such as endotoxin by the liver, leading to the development of skin manifestations, the dilatation of intrapulmonary capillaries and the induction of hypoxaemia.

Adult↗
PubMed2004

Removal of PCDD/F from flue gases in fixed or moving bed adsorbers.

Whereas the PCDD/F-abatement in MSWIs is mostly achieved through entrained-phase adsorption upon activated carbon, the other thermal processes are more bending towards fixed/moving bed adsorption or catalytic destruction. The treatment of entrained-phase adsorption has been previously dealt with. The present paper focuses upon fixed/moving bed adsorption as abatement alternative. The characteristics of granular carbonaceous adsorbents are reviewed and commented upon, and stress some advantages of the fixed/moving bed operation. The equilibrium adsorption characteristics are expressed in terms of the number of active sites of the adsorbent and its saturation capacity. The breakthrough calculations for a fixed/moving bed adsorber are based upon these adsorption characteristics and expressed in terms of the relevant operating parameters of the flue gases to be treated. Although detailed literature data on these adsorbers are scarce, application of the design equations predicts meaningful results, thus demonstrating the predictive capacity of the design method.

Adsorption↗
PubMed1995

Comparison of propofol with isoflurane for maintenance of anesthesia in patients with chronic obstructive pulmonary disease: use of pulmonary mechanics, peak flow rates, and blood gases.

Patients with chronic obstructive pulmonary disease (COPD) are usually anesthetized with an inhalation agent. After Institutional Review Board approval, informed consent was obtained from 60 patients with moderate to severe COPD according to a preoperative severity scoring system, which took into account history and objective findings. By using objective criteria, such patients were randomly assigned to receive propofol (group I) or isoflurane (group II) as primary maintenance agents. Preoperative and postoperative arterial blood gases, peak expiratory flow rates (PEFR), and chest X-rays were compared. Total dynamic compliance (CDYN) and V1 (% volume exhaled in first second) were measured using Pitot tube sidestream spirometry. A 1,000-mL super-syringe was used to measure total static compliance (CST). Measurements were recorded postintubation, midanesthesia, and pre-extubation. All patients received fentanyl, lidocaine, and propofol, 1.5 to 2.0 mg/kg, for induction. Succinylcholine, 1-1.5 mg/kg, was administered to facilitate intubation. Maintenance was with N2O-O2, vecuronium, and either propofol (n = 30) or isoflurane (n = 30). Both groups showed decreases in postoperative PaO2, SaO2, and PEFR (p < 0.05), but there were no differences between groups (p > 0.05). There were no significant chest X-ray differences. There were no differences between groups with respect to intraoperative pulmonary mechanics (p > 0.05). The only difference between groups was an increase in postoperative PaCO2 in group I and a decrease in group II (p < 0.05). Use of Pitot tube sidestream spirometry is a practical and noninvasive technique for monitoring pulmonary mechanics during anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed2002

Effects of anaesthesia on blood gases, acid-base status and ions in the toad Bufo marinus.

It is common practice to chronically implant catheters for subsequent blood sampling from conscious and undisturbed animals. This method reduces stress associated with blood sampling, but anaesthesia per se can also be a source of stress in animals. Therefore, it is imperative to evaluate the time required for physiological parameters (e.g. blood gases, acid-base status, plasma ions, heart rate and blood pressure) to stabilise following surgery. Here, we report physiological parameters during and after anaesthesia in the toad Bufo marinus. For anaesthesia, toads were immersed in benzocaine (1 g l(-1)) for 15 min or until the corneal reflex disappeared, and the femoral artery was cannulated. A 1-ml blood sample was taken immediately after surgery and subsequently after 2, 5, 24 and 48 h. Breathing ceased during anaesthesia, which resulted in arterial Po(2) values below 30 mmHg, and respiratory acidosis developed, with arterial Pco(2) levels reaching 19.5+/-2 mmHg and pH 7.64+/-0.04. The animals resumed pulmonary ventilation shortly after the operation, and oxygen levels increased to a constant level within 2 h. Acid--base status, however, did not stabilise until 24 h after anaesthesia. Haematocrit doubled immediately after cannulation (26+/-1%), but reached a constant level of 13% within 24 h. Blood pressure and heart rate were elevated for the first 5 h, but decreased after 24 h to a constant level of approximately 30 cm H2O and 35 beats min(-1), respectively. There were no changes following anaesthesia in mean cellular haemoglobin concentration, [K+], [Cl-], [Na+], [lactate] or osmolarity. Toads fully recovered from anaesthesia after 24 h.

Acid-Base Equilibrium↗
PubMed1998

Use of alkaline comet assay (single cell gel electrophoresis technique) to detect DNA damages in lymphocytes of operating room personnel occupationally exposed to anaesthetic gases.

Here, we report the possible in vivo induction DNA damage by exposure to various waste anaesthetic gases such as halothane, nitrous oxide and isoflurane. The alkaline comet assay (single cell gel electrophoresis technique) was carried out on 66 operating room personnel (anaesthetists [doctors]; anaesthesia nurses and anaesthesia unit technicians) currently employed at the Ankara Hospital in Turkey. A significant increase in the number of lymphocytes with DNA migration was observed in operating room personnel as compared to controls. Also, the extent of damage in exposed smokers were significantly higher than exposed nonsmokers. This study supports the existence of an association between DNA damage and occupational exposure to inhalation anaesthetics.

Adult↗
PubMed1991

Effect of enlarged adenoids on arterial blood gases in children.

The enlarged adenoid is a common disorder in children resulting in nasopharyngeal obstruction. Many authors suggest that increased nasal resistance to respiration may cause disturbances in the pulmonary ventilation and carry the risk of obstructive sleep apnoea and/or cardiopulmonary syndrome. This study comprised 30 children complaining of long-standing nasal obstruction due to enlarged adenoids. Adenoidectomy was performed and the arterial blood gases were measured before and one month after surgery. Twelve normal children were also included as controls. Statistical evaluation of the results showed that O2 saturation and arterial O2 tension (PaO2) were significantly low before the operation, and increased significantly after surgery. Arterial CO2 tension (PaCO2) was insignificantly low before operation, but decreased significantly after adenoidectomy. It was concluded that enlarged adenoid may be associated with ventilatory impairment which is reversible after adenoidectomy.

Adenoidectomy↗
PubMed1989

Ion mobility spectrometry of halothane, enflurane, and isoflurane anesthetics in air and respired gases.

Three common gaseous anesthetics, halothane, enflurane, and isoflurane, were characterized by using ion mobility spectrometry (IMS)/mass spectrometry, and the dependence of product ion distributions on temperature and concentration was evaluated. At 40 degrees C and 500 ppb, negative ion mobility spectra in air largely consisted of monomer or dimer adducts with Br- or Cl- formed through dissociative electron capture of molecular neutrals. With increased temperature or decreased vapor concentrations, declustering and dissociation of product ions became pronounced. Ion-molecule reactions in the drift region of the IMS were evident as distortions in peak shape in the mass-resolved mobility spectra and in variable reduced mobilities for the same ions. A portable hand-held IMS was used for convenient, real-time detection of enflurane in respired gases following a controlled inhalation episode.

Air↗
PubMed2003

A micromachined calorimetric gas sensor: an application of electrodeposited nanostructured palladium for the detection of combustible gases.

Palladium films with regular nanoarchitectures were electrochemically deposited from the hexagonal (H1) lyotropic liquid crystalline phase of the nonionic surfactant octaethyleneglycol monohexadecyl ether (C16EO8) onto micromachined silicon hotplate structures. The H1-e Pd films were shown to have high surface areas (approximately 28 m2 g(-1)) and to act as effective and stable catalysts for the detection of methane in air on heating to 500 degrees C. The response of the H1-e Pd-coated planar pellistors was found to be linearly proportional to the concentration of methane between 0 and 2.5% in air with a detection limit below 0.125%. Our results show that the electrochemical deposition of nanostructured metal films offers a promising approach to the fabrication of micromachined calorimetric gas sensors for combustible gases.

Journal Article↗
PubMed2006

Micro hot plate-based sensor array system for the detection of environmentally relevant gases.

A monolithic stand-alone gas sensor system is presented, which includes on a single chip an array of three metal oxide-coated micro hot plates with integrated MOS-transistor heaters, as well as a specifically designed digital system architecture. An octagonal-shaped micro hot plate design with MOS-transistor heaters has been adopted for the three gas sensors. The integrated circuitry includes a programmable digital temperature regulation, digital sensor readout units, and a standard serial interface. The programmable digital temperature controllers enable individual regulation of the micro hot plate temperatures in constant or dynamic mode. Nanocrystalline tin oxide thick films with different Pd dopings (undoped, 0.2 and 3 wt %) were used. Gas test measurements for environmentally relevant gases were carried out and evidenced detection limits of less than 1 ppm for carbon monoxide, or 100 ppm for methane, both at 40% relative humidity. Temperature modulation techniques were successfully applied for improved analyte discrimination.

Journal Article↗
PubMed2000

Catalyzed hydrolysis of nerve gases by metal chelate compounds and potentiometric detection of the byproducts.

A new method for detection of nerve gases, Sarin and Soman, was proposed on the basis of their catalyzed hydrolysis by metal chelate compounds and potentiometric detection of the byproduct, fluoride ion. Diisopropyl fluorophosphate (DFP) was used as a nerve gas mimic. The copper ion chelates shift the potential of the fluoride ion-selective electrode to more positive stable potential, which is beneficial for lowering the detection limit. In the presence of DFP, the electrode potential decreases rapidly with time due to the catalyzed hydrolysis of DFP and the production of fluoride ion. This method is sensitive, selective, and reproducible. The detection limit for DFP is 2 x 10(-6) M with a potential drop between 40 and 60 mV.

Catalysis↗
PubMedDate not supplied

Correlation of the solubilities of gases and vapors in methanol and ethanol with their molecular structures.

Two four-parameter quantitative structure-property relations, with R2 = 0.95 and R2 = 0.97, respectively, gave good correlations for the solubilities of 87 gases and vapors in methanol and 61 in ethanol. All the descriptors used are derived solely from the structures of the molecules, making it possible to predict solubilities for unavailable or unknown compounds.

Journal Article↗
PubMed2003

Sulfur dioxide treatment from flue gases using a biotrickling filter-bioreactor system.

Complete treatment of sulfur dioxide (SO2) from flue gases in a two-stage process consisting of a biotrickling filter followed by biological post-treatment unit was investigated. The biotrickling filter could remove 100% of influent SO2 from simulated flue gas at an empty bed residence time of 6 s for a concentration range of 300-1000 ppm(v). All the absorbed SO2 was recovered in the biotrickling filter liquid effluent as sulfite (a product of chemical reaction of SO2) and sulfate (product of biological oxidation of sulfite). The biotrickling filter liquid effluent was further processed biologically in a single post-treatment unit consisting of a combined anaerobic and microaerophilic reactor for the simultaneous reduction of sulfate and sulfite to sulfide and oxidation of sulfide to elemental sulfur. The post-treatment unit could effectively treat the biotrickling filter effluent and produce elemental sulfur. The sulfur production efficiency of the reactor reached about 80% of the SO2 treated. This new biological treatment system seems to be a promising alternative for flue gas desulfurization.

Air Pollutants↗
PubMed2003

Theoretically predicted rate constants for mercury oxidation by hydrogen chloride in coal combustion flue gases.

In this work, theoretical rate constants are estimated for mercury oxidation reactions by hydrogen chloride that may occur in the flue gases of coal combustion. Rate constants are calculated using transition state theory at the quadratic configuration interaction (QCI) level of theory with single and double excitations, and are compared to results obtained from density functional theory, both including high level pseudopotentials for mercury. Thermodynamic and kinetic data from the literature are used to assess the accuracy of the theoretical calculations when possible. Validation of the chosen methods and basis sets is based upon previous and current research on mercury reactions involving chlorine. The present research shows that the QCISD method with the 1992 Stevens et al. basis set leads to the most accurate kinetic and thermodynamic results for the oxidation of mercury via chlorine containing molecules. Also, a comparison of the heats of reaction data for a series of mercury oxidation reactions reveals that the density functional method, B3LYP, with the 1997 Stuttgart basis set provides reasonably accurate results for these large systems.

Air Pollutants↗
PubMed2004

Changes in the regional emissions of greenhouse gases and ozone-depleting compounds.

In the wake of the Kyoto and Montreal Protocols, there is a need to verify whether policies to reduce emissions are working. We present data showing that emissions of ozone-depleting compounds, such as the chlorofluorocarbons and methyl chloroform, are decreasing from some regions of the United States but emissions of the greenhouse gases do not appear to be declining.

Air Pollutants↗
PubMed2005

Evaluation of PCDD/F congener partition in vapor/solid phases of waste incinerator flue gases.

Activated carbon injection (ACI) is commonly used to control PCDD/F (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans) emissions from stationary sources. In this study, the characteristics of PCDD/Fs emitted from one municipal waste incinerator (MWI) and two industrial waste incinerators (IWI-1 and IWI-2) that apply activated carbon systems for controlling the emissions are investigated via intensive stack sampling. MWI and IWI-1 are equipped with ACI and bag filters (BF) while IWI-2 is equipped with a fixed activated carbon bed (FCB). Results indicate that most PCDD/Fs in flue gas downstream of ACI+BF exist in vapor phase (over 90%) while most PCDD/ Fs exist in solid phase (over 60%) downstream of FCB. For MWI and IWI-1, the removal efficiencies of vapor and solid-phase PCDD/Fs are 98.5-99.6% and 99.8-99.9%, respectively. In addition,the removal efficiencies of vapor- and solid-phase PCDD/Fs are 84.5% and -13.4% in IWI-2, respectively. The results also indicate that the partition of vapor/solid-phase PCDD/F is affected by the type of the air pollutant control devices (APCDs) applied upstream and the particulate matter concentration in flue gas. On the basis of the sampling results of waste incinerators, this study preliminarily establishes the equations for predicting vapor/solid-phase PCDD/F partition in flue gases downstream of various APCDs including cyclone (CY), electrostatic precipitator (EP), FCB, ACI+BF, and selective catalytic reduction system (SCR).

Air Pollutants↗
PubMed2005

Adsorption of super greenhouse gases on microporous carbons.

Grand canonical Monte Carlo simulations are reported for low molecular weight perfluorocarbons (C2F6 and CF4) and their dilute (10% molar) mixtures in N2 adsorbing unto slitlike graphite pores. Adsorption isotherms and selectivity plots are shown for various temperatures, pressures, and pore widths. It is shown how selectivities on the order of thousands may be obtained when appropriate pore widths and thermodynamic conditions are used. Selective entrapment of these super greenhouse gases onto carbon nanopores is shown to be a promising alternative in the remediation of air streams.

Adsorption↗