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PubMedDate not supplied

A physiologically based pharmacokinetic model for chloropentafluorobenzene in primates to be used in the evaluation of protective equipment against toxic gases.

Chloropentafluorobenzene (CPFB) has been proposed as an innocuous simulant for the uptake of toxic gases. Exposure to CPFB in a training exercise could be inferred afterwards from a measurement of CPFB in expired breath. To understand the relationship between exposure and measurement, we have developed a physiologically-based pharmacokinetic (PB-PK) model for CPFB in primates. To test the model, inhalation exposures were conducted on anesthetized rhesus monkeys. CPFB concentration in expired breath was measured during and after exposure. Simulations of CPFB uptake and clearance agreed with experimental measurements in seven of eight monkeys. A human version of the model was used to simulate exposures consisting of a single breath or a few breaths. By showing a measurable CPFB concentration in expired breath after several hours of clearance, simulations with the human model indicated the suitability of CPFB as a simulant for toxic gases.

Animals↗
PubMed2002

Effect of medroxyprogesterone on arterial blood gases, leptin and neuropeptide Y in postmenopausal females.

Natural progesterone, a potent respiratory stimulant, stimulates leptin production in premenopausal females. Leptin and its counterpart neuropeptide Y (NPY) have recently been linked with respiration. The effect of medroxyprogesterone acetate (MPA) on arterial blood gases, serum leptin and NPY was evaluated in this study. Fourteen postmenopausal females with respiratory impairment, due mostly to chronic obstructive pulmonary disease, were recruited for a randomised, double-blind, placebo-controlled crossover trial. Arterial blood gases, serum leptin and NPY concentrations were measured at baseline and after 14 days of treatment with placebo and MPA, separated by a 6-week washout period. Thirteen patients completed the trial. The mean+/-SD carbon dioxide tension in arterial blood (Pa,CO2) was 5.4+/-0.6 kPa at baseline, and decreased by 0.8+/-0.3 kPa during treatment with MPA. The oxygen tension in arterial blood (Pa,O2) and pH did not change. At baseline, the mean base excess was 0.6+/-1.9 mmol x L(-1) and the mean bicarbonate (HCO3-) concentration was 25.1+/-1.6 mmol x L(-1). With MPA, base excess decreased by 2.2+/-1.2 mmol x L(-1) and HCO3- by 1.9+/-1.0 mmol x L(-1) from baseline. The mean concentrations of serum leptin (19.8+/-9.9 microg x L(-1) at baseline, 19.7+/-9.8 microg x L(-1) with MPA) or NPY (94.0+/-18.3 pmol x L(-1) at baseline, 85.1+/-41.2 pmol x L(-1) with MPA) did not change. However, the reduction in Pa,CO2 correlated with the reduction of serum leptin concentration. Medroxyprogesterone acetate effectively decreased the carbon dioxide tension in postmenopausal females with chronic respiratory impairment. The results suggest that a decrease in the carbon dioxide tension of > or = 0.9 kPa is necessary for a reduction in serum leptin concentration.

Aged↗
PubMed1997

Effects of inspiratory flow waveforms on arterial blood gases and respiratory mechanics after open heart surgery.

The clinical usefulness of inspiratory flow pattern manipulation during mechanical ventilation remains unclear. The aim of this study was to investigate the effects of different inspiratory flow waveforms, i.e. constant, sinusoidal and decelerating, on arterial blood gases and respiratory mechanics, in mechanically ventilated patients. Eight patients recovering after open heart surgery for valvular replacement and/or coronary bypass were studied. The ventilator inspiratory flow waveform was changed according to a randomized sequence, keeping constant the other variables of the ventilator settings. We measured arterial blood gases, flow, volume and pressure at the proximal (airway opening pressure (Pao)) and distal (Ptr) ends of the endotracheal tubes before and after 30 min of mechanical ventilation with each inspiratory flow waveform. We computed breathing pattern, respiratory mechanics (pressures and dynamic elastance) and inspiratory work, which was then partitioned into its elastic and resistive components. We found that: 1) arterial oxygen tension (Pa,O2) and arterial carbon dioxide tension (Pa,CO2) were not affected by changes in the inspiratory flow waveform; and 2) peak Pao and Ptr were highest with sinusoidal inspiratory flow, whilst mean Pao and Ptr and total work of breathing were least with constant inspiratory flow, mainly because of a concomitant decrease in resistive work during constant flow inflation. The effects of the inspiratory flow profile on Pao, Ptr and total inspiratory work performed by the ventilator were mainly due to the resistive properties of the endotracheal tubes. We conclude that the ventilator inspiratory flow waveform can influence patients' respiratory mechanics, but has no impact on arterial oxygen and arterial carbon dioxide tension.

Adult↗
PubMed2005

Oxidative stress in operating room personnel: occupational exposure to anesthetic gases.

Health professionals exposed to anesthetic gases are at higher risk of reproductive, neurological, hematological, immunological, hepatic and renal system diseases. We investigated if oxidative stress induced by chronic exposure to anesthetic gases has any association with this matter. Plasma lipid peroxidation, total antioxidant capacity and total thiol molecule levels were measured in 66 operating room staff in comparison with 66 controls. The exposed group had a significantly higher level of lipid peroxidation with decreased thiol groups compared to control subjects. Total antioxidant capacity of the body was no different among exposed and not exposed subjects. Increased lipid peroxidation in the blood of exposed subjects warns that oxygen free radicals have increased in the body and thus might attack cells, which, in the long-term, results in multi-organ damage. The remaining blood total antioxidant capacity at normal values is promising and means that other non-thiol antioxidants, such as uric acid, transferrin, ceruloplasmin, albumin, and vitamin antioxidants, such as alpha-tocopherol and ascorbic acid, have been stimulated to maintain the total anti-oxidant power of the body at normal state.

Air Pollutants, Occupational↗
PubMed2002

Reflective light modulator based on epsilon-GaSe crystal.

We report the results of investigating a low-voltage, polarization-insensitive, reflective-type modulator based on an epsilon-GaSe crystal and operated at the 1.960-eV line of a He-Ne laser. We demonstrate that the modulation in an Al-epsilon-GaSe-Cu device results mainly from the Franz-Keldysh effect. Relatively high speed and low operating voltage could make these modulators with Schottky-barrier contacts attractive devices in the red range of the spectrum.

Journal Article↗
PubMed2002

Path-radiance correction by polarization observation of Sun glint glitter for remote measurements of tropospheric greenhouse gases.

High-accuracy remote measurement of greenhouse gases is hampered by contamination of the field of view by the path radiance of solar radiation scattered from clouds and aerosols. A method is proposed for eliminating the effect of path radiance by differentiating two components of polarized light. The polarization of path radiance is measured directly at the wave-number region of strong water-vapor absorption. Using this measurement, we eliminate the components of path radiance involved in other bands, which are used for greenhouse gas measurements, by differentiating two components of the polarized light. It is shown that the effect of path radiance on retrieving the column amount of gases potentially can be reduced to below 0.1%.

Journal Article↗
PubMed2004

Ground-based imaging differential optical absorption spectroscopy of atmospheric gases.

We describe a compact remote-sensing instrument that permits spatially resolved mapping of atmospheric trace gases by passive differential optical absorption spectroscopy (DOAS) and present our first applications of imaging of the nitrogen dioxide contents of the exhaust plumes of two industrial emitters. DOAS permits the identification and quantification of various gases, e.g., NO2, SO2, and CH2O, from their specific narrowband (differential) absorption structures with high selectivity and sensitivity. With scattered sunlight as the light source, DOAS is used with an imaging spectrometer that is simultaneously acquiring spectral information on the incident light in one spatial dimension (column). The second spatial dimension is scanned by a moving mirror.

Journal Article↗
PubMed2005

Refractive-index measurement of gases with a phase-shift keyed interferometer.

The presented new type of interferometer combines the principle of two-beam interferometry and the technique of phase-shift keying of holographic gratings. On the basis of the phase-shift keying technique, the interferometer employs two different geometries for the recording and the readout process. Two holographic Bragg gratings are recorded in transmission geometry and simultaneously read out in reflection geometry using a tunable IR laser. Both gratings have the same grating period but a relative phase shift. The wavelength of the readout beam is fitted to the Bragg condition for the gratings. Using a tunable IR laser for the readout process, we can measure the spectral transfer function of both combined gratings. The shape of the measured transfer function is extremely sensitive to the phase shift between the two gratings. We demonstrate an application of this method by the measurement of refractive-index variations of gases due to pressure changes of the gases. The achieved resolution with respect to the measurement of phase shifts is approximately 1/40 pi. We present experimental investigations on two kinds of gas (an inert gas and a gas composition) as well as an efficient numerical approach to simulate the transfer function for Bragg gratings with a phase shift. Furthermore, we present a method to increase the resolution based on the controlled manipulation of the transfer function.

Journal Article↗
PubMed1993

Carbicarb, sodium bicarbonate, and sodium chloride in hypoxic lactic acidosis. Effect on arterial blood gases, lactate concentrations, hemodynamic variables, and myocardial intracellular pH.

The effects of Carbicarb, sodium bicarbonate, and sodium chloride on arterial blood gases, lactate concentrations, hemodynamics, and myocardial intracellular pH were compared in hypoxic lactic acidosis with controlled carbon dioxide elimination. Twenty-one young mongrel dogs were anesthetized, mechanically ventilated, and randomly allocated into one of three treatment groups. After hypoxic lactic acidosis was induced and maintained, 2.5 mEq/kg of one of the agents was infused over 30 min. Arterial blood gases, pH, lactate concentrations, and hemodynamic variables were measured immediately prior to the infusion of the agent and 30 min after the infusion was completed. With sodium bicarbonate administration, there was a significant increase in arterial PCO2 as compared to both Carbicarb or sodium chloride administration. With Carbicarb administration, there was a significant increase in arterial pH, base excess, and cardiac index, without a significant increase in arterial lactate concentration as compared to sodium bicarbonate or sodium chloride administration. Stroke volume index was also increased significantly with decreased heart rate. The data suggest that Carbicarb administration in hypoxic lactic acidosis improved hemodynamics compared with sodium bicarbonate or sodium chloride administration. The increased stroke volume and cardiac contractility appear to be due to improved myocardial intracellular pH.

Acidosis, Lactic↗
PubMed1975

[The effect of nasal obstruction on the susceptibility of mice to noxious gases (author's transl)].

The effect of nasal obstruction on mice--the maice were forced to breathe through the mouth--was studied when the animals were exposed to noxious gases. It was noted that the forced mouth breathing made the mice less vulnerable to hydrogen sulfide, carbon monoxide and toluen vapor when expressed by the time interval before they lost righting reflex or showed respiratory arrest. The levels of the gases which could induce these sings within 5-10 minutes were significantly elevated with the "mouth breathing" mice. Possible mechanisms for this phenomenon and its application for men were discussed.

Animals↗
PubMed1984

Gas-chromatographic determination of environmental gases with the application of thermal desorption from charcoal disk.

Direct measurement of the gases adsorbed on charcoal disk was examined by the gas-chromatograph with thermal desorption devices to improve the inadequacies of the common passive monitor. Since the most satisfactory values were obtained by a preliminary experiment with toluene vapor, the experiments were done with concentrations of 20, 40 and 80 ppm, respectively to get a linear relationship between the mean adsorption per piece and the concentration of toluene. Adsorption on the charcoal disk, and its extraction by carbon disulfide without degeneration, are the necessary conditions for the measurement of gas concentration. Methanol was selected as typical from among the gases for which the common passive monitor is inapplicable. The experiment on methanol was carried out in a manner similar to that done on toluene. In conclusion, our method was found to be satisfactory for the analysis of toluene, and, if the conditions are appropriate, for methanol.

Adsorption↗
PubMed2001

The effect of arterial blood sampling sites on blood gases and acid-base balance parameters in calves.

In 21 healthy calves, 1-6 months old, the interrelationship and comparability of acid-base balance variables (pH, HCO3-, BE) and blood gases (pCO2, pO2, and sat-O2) were evaluated in arterial blood collected from a larger, centrally localised (the a. axillaris) and a smaller peripheral artery (the a. auricularis caudalis). Sampling was done by direct puncture of the vessels without local anaesthesia. Except for blood pH, significant differences were observed in the average values of pCO2, pO2, HCO3-, sat-O2 (P < 0.001), and BE (P < 0.05). Analyses of blood from the a. axillaris showed higher pH, pO2, and sat-O2 values, and lower pCO2, HCO3-, and BE values compared with that from the a. auricularis caudalis. Despite statistically significant differences between some variables, in all indices high and significant correlation relationships were recorded (R = 0.928-0.961; P < 0.001). Therefore, from the biological and clinical point of view, these differences are unimportant and the presented method of peripheral arterial blood sampling can be considered suitable for evaluating blood gases and acid-base status.

Acid-Base Equilibrium↗
PubMed2002

Renewable energies in electricity generation for reduction of greenhouse gases in Mexico 2025.

This study presents 4 scenarios relating to the environmental futures of electricity generation in Mexico up to the year 2025. The first scenario emphasizes the use of oil products, particularly fuel oil, and represents the historic path of Mexico's energy policy. The second scenario prioritizes the use of natural gas, reflecting the energy consumption pattern that arose in the mid-1990s as a result of reforms in the energy sector. In the third scenario, the high participation of renewable sources of energy is considered feasible from a technical and economic point of view. The fourth scenario takes into account the present- and medium-term use of natural-gas technologies that the energy reform has produced, but after 2007 a high and feasible participation of renewable sources of energy is considered. The 4 scenarios are evaluated up to the year 2025 in terms of greenhouse gases (GHG) and acid rain precursor gases (ARPG).

Acid Rain↗
PubMed1978

Arterial blood gases in Pranayama practice.

Pranayama is a Yogic breathing practice which is known experientially to produce a profound calming effect on the mind. In an experiment designed to determine whether the mental effects of this practice were accompanied by changes in the arterial blood gases, arterial blood was drawn from 10 trained individuals prior to and immediately after Pranayama practice. No significance changes in arterial blood gases were noted after Pranayama. A neural mechanism for the mental effects of this practice is proposed.

Adult↗
PubMed1987

The metabolism of low molecular weight hydrocarbon gases in man.

The metabolism of ethane and pentane in man is demonstrated to occur from the uptake of an enriched atmosphere of these gases in a rebreathe spirometer circuit. Dithiocarb, an inhibitor of alkane metabolism, reduced uptake and increased the respiratory excretion of these gases. This effect was least marked for the slowly metabolised ethane. Therefore the endogenous production of ethane as measured by respiratory excretion is less affected. However pentane is rapidly metabolised and this limits the use of simple respiratory excretion of pentane as a measure of in vivo lipid peroxidation.

Disulfiram↗
PubMed2001

Hyperpolarised gases in magnetic resonance: a new tool for functional imaging of the lung.

In magnetic resonance imaging (MRI), nuclear spins are the source of the image signal. In the lung, low-proton spin density in alveolar gas and abundant gas-tissue interfaces substantially impair conventional native 1H-MRI. Spin polarisation can be increased in two non-radioactive noble gas isotopes, 3He and 129Xe, by exposure to polarised laser light. When inhaled, such "magnetized" gases provide high-intensity MR images of the pulmonary airspaces. Thus, hyperpolarised gas (HPG) MRI opens up new routes to a) morphologic imaging of airways and alveolar spaces, and b) analysis of the intrapulmonary distribution of inhaled aliquots of these tracer gases; c) diffusion-sensitive MRI-techniques allow mapping of the "apparent diffusion coefficient" (ADC) of 3He within lung airspaces, where ADC is physically related to local bronchoalveolar dimensions; d) also, 3He magnetisation decays in an oxygen-containing atmosphere at a rate proportional to ambient PO2. This property allows image-based determination of regional broncho-alveolar PO2 and its decrease during a breathhold. Currently, these modalities of functional lung imaging are being assessed by several European and American research groups in animal models, human volunteers and patients. First results show good imaging quality with excellent spatial and unprecedented temporal resolution, and attest to the reproducibility, feasibility and safety of the technique. Regionally impaired ventilation of both structural and functional origin is detected with high sensitivity, e.g. in smokers, asthmatics, patients with COPD or after lung transplantation. Studies into regional ADC and PO2 measurement demonstrate good agreement with reference methods and physiological predictions. The present limitations of HPG-MRI include the HPG production rate and the US and EU health authorities' still pending final approval for clinical use.

Adult↗
PubMed2003

Venous blood gases and lactates of wild loggerhead sea turtles (Caretta caretta) following two capture techniques.

During summer of 2001, venous blood gases were determined in loggerhead sea turtles (Caretta caretta) captured by trawl (n = 16) in coastal waters of South Carolina and Georgia (USA) as part of a sea turtle census program and captured in pound nets (n = 6) in coastal North Carolina (USA) during a study of sea turtle population biology. Trawls were towed for 30 min, so turtles captured were forcibly submerged for < or = 30 min. Pound nets are passive gear in which fish and sea turtles are funneled into a concentrated area and removed periodically. Sea turtles in pound nets are free to surface and to feed at will. Blood was obtained from the dorsal cervical sinus as quickly as possible after landing on the boat (range 2-10 min trawl, 1-2 min pound net) and at 30 min after landing just prior to release. Blood gases including pH, partial pressures of O2 and CO2 (pO2, pCO2), and lactate were measured within 10 min. Instrument measurements for pH, pO2, and pCO2 made at 37 C were corrected to cloacal temperature and HCO3- was calculated from temperature-corrected pH and pCO2. Venous blood pH and bicarbonate were higher, and pO2 and lactate were lower from pound net-captured turtles compared to trawl captured turtles at the initial sampling time. In pound net turtles, pH and bicarbonate declined and lactate increased during 30 min on deck. In trawled sea turtles, venous blood pH increased and pCO2 and pO2 decreased during the 30 min on deck. Both capture systems caused perturbations in blood gas, acid-base, and lactate status, though alterations were greater in trawl captured turtles.

Acid-Base Imbalance↗
PubMed1976

Scavenging of dental anesthetic gases.

Results of recent surveys suggest that there are significant health hazards involved with chronic exposure to waste anesthetic gases. While results of these surveys were significant, they did not prove a cause-effect relationship. Considerable evidence in experimental animals suggests such a relationship; it is reasonable to assume that this applies to the clinical situation. An anesthetic technique that uses a circle-system absorber with a scavenging trap and non-recirculating exhaust duct has been described. This system was combined with use of a closed-cell rubber sponge for an oropharyngeal pack that was impermeable to air or anesthetic gases. In addition, a tight-fitting nasal mask or sealed nasopharyngeal tube was used. Ventilation of room air also was improved. These changes produced a 93.3% reduction in halothane and 91.2% reduction in nitrous oxide in the dental operating room.

Air Pollution↗