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PubMedDate not supplied

Does it make sense to heat gases higher than body temperature for the treatment of cold water near-drowning or hypothermia? A point of view paper.

There appears to be several areas of concern relating to the continued use of heating gases higher than body temperature for the treatment of cold water near-drowning. The use of heated gases as a primary means to rewarm a hypothermic patient does not seem to be any more effective than doing nothing at all. These low rewarming rates translate into some very long resuscitations. Even Dr. Nemiroff, who was a strong advocate of using heated humidified gases for treating cold water near-drowning, did not consider the use of warm inspired gases to be a primary rewarming technique. He referred to the use of heated humidified gases as a, "stabilization technique". However, does it make sense to use a technique that is several times slower than other methods of similar complexity? Does it make sense to use a protocol that may in fact lower a hypothermic patient's basal metabolic rate? There are some major patient safety issues raised by heating gases to high levels. However, there have not been many patients with documented airway damage. I have several hypothesis about why this is so. Few people seem to know how to significantly heat their patient's circuit. If they devise a system that gets to the therapeutic range they usually have second thoughts when the bag-valve-mask is too hot to hold, or the plastic wide bore tubing begins to melt, they will reduce the system temperature on that basis alone. Many of the hypothermic patients who are intubated simply do not have good survival rates, and so we may underestimate the degree of airway damage that occurs. Spontaneously breathing patients will tend to refuse to breathe hot gases which limits their potential for airway damage. However, is this a risk we need to run? Would it not make more sense to heat the inspired gases to close to body temperature and avoid the problem? I feel that the time has come for the Respiratory Therapy community to come together and work on this problem. The researchers have done their jobs in providing us with reasonable data on which to base a clinical decision. It would seem to me that if a Clinical Practice Guideline for cold water near-drowning or hypothermia were in place it might provide the other groups impetus for updating their guidelines. The bottom line is that patients deserve the best care that we know how to provide, and a clear set of guidelines is an essential first step.

Attitude of Health Personnel↗

PubMed1989

Biochemical effects of combined gases of nitrogen dioxide and ozone. III. Synergistic effects on lipid peroxidation and antioxidative protective systems in the lungs of rats and guinea pigs.

Rats and guinea pigs were exposed continuously to 0.4 ppm NO2, 0.4 ppm O3 or a combination of the two gases for 2 weeks. The concentration of lipid peroxides in lungs of rats and guinea pigs exposed to NO2 alone or O3 alone did not change. The lipid peroxide level of rats inhaling the combined gases also did not change. However, the level of lipid peroxides in guinea pigs exposed to a combination of the two gases was increased to 2.2 times of the control level, showing a synergistic interaction. No increases of antioxidative protective enzyme activities and of antioxidants (such as NPSH, VE, VC) in guinea pigs exposed to NO2, O3 or the combined gases were found. In rats, no changes in enzyme activities and of the antioxidant contents were observed after NO2 alone, but O3 exposure produced slight increases of NPSH, VC, and GPx-H2O2. On the other hand, in rats exposed to the combined gases, marked synergistic increased of many antioxidative factors such as NPSH, VC, G6PD, GPx-cum.OOH and GPx-H2O2 were found. The results show that those animals which are able to increase antioxidative protective factors in the lung following exposure to the combined gases do not respond with a significant increase in lipid peroxides. On the other hand, in animals with poor induction-ability of these factors lipid peroxides are formed. This might explain why guinea pigs were the most sensitive to the effects of the combined gases. Furthermore, it was shown that in guinea pigs the increased level of lipid peroxides and that in rats the increased activities of antioxidative enzymes and the increased contents of the antioxidants were synergistic following exposure to the combined gases.

Animals↗

PubMed1992

[Emission and control of gases and odorous substances from animal housing and manure depots].

Agricultural animal production in increasingly regarded as a source of gases which are both aggravating and ecologically harmful. An overview of the origin, number and quantity of trace gases emitted from animal housing and from manure stores is presented and possible means of preventing or reducing them are discussed. Of the 136 trace gases in the air of animal houses, odorous substances, ammonia and methane are most relevant to the environment. The role played by the remaining gases is largely unknown. Quantitative information is available for 23 gases. The gases are emitted principally from freshly deposited and stored faeces, from animal feed and from the animals themselves. Future work should determine sources and quantities of the gases emitted from animal housing more precisely and should aim to investigate the potential of these gases to cause damage in man, animals and environment. Odorous substances have an effect on the area immediately surrounding the animal housing. They can lead to considerable aggravation in humans. For years, VDI1 guidelines (3471/72), which prescribe distances between residential buildings and animal housing, have been valuable in preventing odour problems of this kind. Coverings are suitable for outside stores. The intensity of the odour from animal housing waste air increases from cattle through to hens and pigs; it is also further affected by the type of housing, the age of the animals and the purpose for which they are being kept. Methods of cleaning waste air (scrubbers/biofilters) are available for problematic cases. The need for guidelines to limit emissions from individual outside manure stores (lagoons) is recognised. Total ammonia emissions from animal production in the Federal Republic of Germany (up to 1989) are estimated at approximately 300,000 to 600,000 t/year. There is a shortage of satisfactory and precise research on the extent of emissions, in particular on those from naturally ventilated housing. It is calculated that between 12 and 21 kg/ha of nitrogen a year enter the soil via the air, the average of which is higher than the average "critical loads" for most natural habitats. Ammonia has a direct effect on the trees in the area surrounding animal housing and is transported long distances through the air causing eutrophication and acidification of water and vegetation. This frequently results in changes in plant sociology. Reduction measures must begin with the housing and manure removal systems and with feeding and management.(ABSTRACT TRUNCATED AT 400 WORDS)

Air Pollution↗

PubMed1999

Failure of activated charcoal to reduce the release of gases produced by the colonic flora.

OBJECTIVE: Activated charcoal is used to treat excessive volume or malodor of intestinal gas. Our previous studies demonstrated that activated charcoal failed to bind appreciable quantities of the volumetrically important gut gases. However, the odor of feces and flatus derives primarily from trace quantities of sulfur-containing gases, primarily H2S and methanethiol, which should avidly bind to activated charcoal. The goal of this study was to determine if ingestion of activated charcoal reduces the fecal release of sulfur gases. METHODS: Five healthy human volunteers ingested 0.52 g of activated charcoal four times daily for 1 wk and the fecal liberation of intestinal gases was measured before and after the activated charcoal treatment. In an effort to explain the in vivo results, additional in vitro studies were performed to compare the binding capacity of charcoal to the sulfur gas released by feces. RESULTS: Ingestion of activated charcoal produced no significant reduction in the fecal release of any of the sulfur-containing gases, nor was total fecal gas release or abdominal symptoms significantly influenced. In vitro studies suggested that the failure of ingested charcoal to reduce liberation of sulfur gases probably is explained by the saturation of charcoal binding sites during passage through the gut. CONCLUSION: Commonly employed doses of activated charcoal do not appreciably influence the liberation of fecal gases.

Adult↗

PubMed1974

Use of inert gases and carbon monoxide to study the possible influence of countercurrent exchange on passive absorption from the small bowel.

The purpose of the present study was to quantitate the influence of countercurrent exchange on passive absorption of highly diffusible substances from the small intestine of the rabbit. The absorption of carbon monoxide, which is tightly bound to hemoglobin and therefore cannot exchange, was compared to the absorption of four unbound gases (H(2), He, CH(4), and (133)Xe), which should exchange freely. The degree to which the observed absorption of the unbound gases falls below that predicted from CO absorption should provide a quantitative measure of countercurrent exchange.CO uptake at high luminal Pco is flow-limited and, assuming that villus and central hemoglobin concentrations are equal, the flow that equilibrates with CO (F(co)) was calculated to equal 7.24 ml/min/100 g. The observed absorption rate of the unbound gases was from two to four times greater than would have been predicted had their entire uptake been accounted for by equilibration with F(co). This is the opposite of what would occur if countercurrent exchange retarded absorption of the unbound gases. The unbound gases have both flow- and diffusion-limited components, and F(co) should account for only the fraction of absorption that is flow limited. A simple model of perfusion and diffusion made it possible to calculate the fraction of the total uptake of unbound gases that was flow limited. This fraction of the total observed absorption rate was still about 1.8 times greater than predicted by CO absorption. A possible explanation for this discrepancy is that plasma skimming reduces the hemoglobin of villus blood to about 60% of that of central blood. Thus, F(co) is actually about 1.7 times greater than initially calculated, and with this correction, there is close agreement between the predicted and observed rates of absorption of each of the unbound gases. We conclude that countercurrent exchange does not influence passive absorption under the conditions of this study.

Animals↗

PubMed2003

A three-stage system to remove mercury and dioxins in flue gases.

Mercury (Hg) from combustion of fossil fuels and waste is the dominant source of anthropogenic Hg emissions, globally amounting to more than 1500 t Hgyear(-1). These emissions must decrease substantially in order to counteract increasing environmental levels of Hg and reduce future toxic effects. Uppsala Energi AB, nowadays (May, 2002) Vattenfall Värme Uppsala AB, an energy company in Uppsala, Sweden, has invested in equipments for air and water pollution control of their three waste fired steam boilers. The flue gases are cleaned in three stages in series to meet the strict Swedish regulation. Electrostatic precipitators remove most dust in the first stage, wet scrubbers remove most water-soluble gases, and in the last stage a Filsorption unit removes most remaining impurities in particulate as well as gaseous form. The Filsorption process includes additives injection, sorption, and chemical reaction in a reactor and filtration with a fabric filter. The aim with this article is to evaluate the efficiency of the system to recover Hg in flue gases from boilers in routine operation. Flue gases, ashes, and water were sampled yearly for 21 years and analysed for Hg, dioxin, and other potential contaminants received at waste incineration. The results clearly demonstrate the decreasing use of Hg in society the last two decades as influenced by governmental policy regarding Hg. The results also indicate that the equipment efficiently removed Hg and dioxins from the flue gases to a final concentration of approximately 3.5 microg Hgm(-3) n and 0.01 ng dioxinsm(-3) n, corresponding to more than 97 and 99.9% reduction of Hg and dioxins, respectively, by cleaning in three stages. The electrostatic precipitators and Filsorption stages alone, with the scrubber in bypass, removed 90% of Hg in flue gases. Using the scrubber is motivated to remove acid components and additional Hg, but call for water separated after the condensers to be neutralised and cleaned, so that less than 5 microg l(-1) Hg and 0.02 ngl(-1) dioxins remained, before the water was discharged to a recipient. In conclusion, cleaning flue gases in two or three stages reduced Hg emissions well below Swedish regulations. The strict measures to prevent pollution from waste incineration and simultaneously make use of the energy produced are a good example of a local solution for a global problem.

Adsorption↗

PubMed2000

Blood gases at rest and during exercise in patients with alpha1-Pi deficiency.

Alpha1-protease inhibitor (Pi) deficiency is associated with a protease-anti-protease imbalance leading to premature destruction of lung tissue and early emphysema. Little is known about the blood gases of these patients in the various stages of the disease. The purpose of this study was to evaluate blood gases in patients with alpha1-Pi deficiency when patients were at rest and during exercise, and to correlate these with lung function measurements. A total of 369 patients with severe alpha1-Pi deficiency had pulmonary function test and blood gas analysis, 282 also had blood gases taken during steady state submaximal exercise testing. Only 21% of the patients had normal blood gases at rest; 71% had mild hypoxaemia; 8% had severe hypoxaemia. Surprisingly, 61% of the patients with mild lung disease and a FEV1 of more than 65% predicted were hypoxaemic. During exercise 65% of the patients had a drop in PO2 of more than 0.40 kPa. FEV1 was a significant predictor for the PO2 values at rest and during exercise. During exercise the arterial-alveolar gradient increased in about 50% and decreased in 25% of the patients. Many patients with alpha1-Pi have blood gas abnormalities. Impaired blood gases in early stages of the disease result in a discrepancy between lung function parameters and blood gases. FEV1 measurements inadequately capture the extent of lung disease in patients with alpha1-Pi deficiency, and both blood gases at rest and during exercise are needed in the assessment of all stages of the disease.

Adult↗

PubMed2006

Factors affecting the association between ambient concentrations and personal exposures to particles and gases.

Results from air pollution exposure assessment studies suggest that ambient fine particles [particulate matter with aerodynamic diameter<or=2.5 microg (PM2.5)], but not ambient gases, are strong proxies of corresponding personal exposures. For particles, the strength of the personal-ambient association can differ by particle component and level of home ventilation. For gases, however, such as ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2), the impact of home ventilation on personal-ambient associations is untested. We measured 24-hr personal exposures and corresponding ambient concentrations to PM2.5, sulfate (SO2-(4)), elemental carbon, O3, NO2, and SO2 for 10 nonsmoking older adults in Steubenville, Ohio. We found strong associations between ambient particle concentrations and corresponding personal exposures. In contrast, although significant, most associations between ambient gases and their corresponding exposures had low slopes and R2 values; the personal-ambient NO2 association in the fall season was moderate. For both particles and gases, personal-ambient associations were highest for individuals spending most of their time in high- compared with low-ventilated environments. Cross-pollutant models indicated that ambient particle concentrations were much better surrogates for exposure to particles than to gases. With the exception of ambient NO2 in the fall, which showed moderate associations with personal exposures, ambient gases were poor proxies for both gas and particle exposures. In combination, our results suggest that a) ventilation may be an important modifier of the magnitude of effect in time-series health studies, and b) results from time-series health studies based on 24-hr ambient concentrations are more readily interpretable for particles than for gases.

Aged↗

PubMed1981

Adult body temperature and heated humidification of anesthetic gases during general anesthesia.

To determine the effects on body temperature of heating and humidifying inspired anesthetic gases to 37 C and 100% relative humidity, 42 men who had major surgical procedures under general anesthesia were studied. Group 1 (control) consisted of 10 patients who inspired gases from a standard semicircle absorber system with no added humidity. The mean nasopharyngeal temperature decreased significantly from 36.2 +/- 0.1 C to 34.9 +/- 0.2 C. Ten other patients, group 2, inspired gases that were heated and humidified. Mean nasopharyngeal temperature was maintained at 36.4 +/- 0.2 C with no significant changes throughout the study. One patient in this group became hypothermic, but only transiently. Ten patients, group 3, were allowed to become hypothermic before gases were heated and humidified. The mean nasopharyngeal temperature increased significantly from 34.7 +/- 0.2 C to 36.0 +/- 0.3 C during 4 hours of heated humidification. For groups 4 and 5, six patients each, gases were heated and humidified on alternate hours. The responses of the two groups demonstrated a causal relationship between the heating and humidifying of inspired gases and an increased mean nasopharyngeal temperature. It is concluded that heating and humidifying gases to 37 C and 100% relative humidity effectively maintains normothermia and rewarms hypothermic adults during general anesthesia.

Anesthesia, Inhalation↗

PubMed1986

Determination of permeabilities for two gases from recording the partial pressure of one gas.

When a flexible diffusion layer separates two closed gas chambers containing different mixtures of several gases, the different permeabilities of the layer for these gases lead to differences in the total gas pressures of the two chambers resulting in bulging of the layer and consequent changes in the chamber volumes. Application of the gas laws to binary gas mixtures provides two equations relating the partial pressure changes of one gas in any of the two chambers to the partial pressure difference between the two chambers across the layer. This permits the calculation of the two unknown factors, permeability (or Krogh's diffusion coefficient) of the layer for the measured gas and the permeability ratio of the two gases. Thus the permeabilities of both gases can be determined from recording the partial pressure of one of the gases only. We filled the gas chambers with different mixtures of oxygen and a second gas (nitrogen or carbon dioxide) at atmospheric pressure, closed the chambers, and measured the diffusion of the gases across thin (12-500 microns) layers of various materials by recording the oxygen partial pressure in both chambers with polarographic oxygen electrodes. Permeabilities of these layers for oxygen and the other gas were determined for plastic layers (MEM213, Silastic, Teflon), as well as water and methemoglobin solutions either in a fluid layer or soaked in Millipore filters. The data agreed well with those obtained from other studies in most cases.

Gases↗

PubMed1998

MRI using hyperpolarized noble gases.

The aim of this study was to review the physical basis of MRI using hyperpolarized noble gases as well as the present status of preclinical and clinical applications. Non-radioactive noble gases with a nuclear spin 1/2 (He-3, Xe-129) can be hyperpolarized by optical pumping. Polarization is transferred from circularly polarized laser light to the noble-gas atoms via alkali-metal vapors (spin exchange) or metastable atoms (metastability exchange). Hyperpolarization results in a non-equilibrium polarization five orders of magnitude higher than the Boltzmann equilibrium compensating for the several 1000 times lower density of noble gases as compared with liquid state hydrogen concentrations in tissue and allows for short imaging times. Hyperpolarization can be stored sufficiently long (3 h to 6 days) to allow for transport and application. Magnetic resonance systems require a broadband radio-frequency system - which is generally available for MR spectroscopy - and dedicated coils. The hyperpolarized gases are administered as inhalative "contrast agents" allowing for imaging of the airways and airspaces. Besides the known anesthetic effect of xenon, no adverse effects are observed in volunteers or patients. Pulse sequences are optimized to effectively use the non-renewable hyperpolarization before it decays or is destroyed, using fast low-flip-angles strategies to allow for dynamic/breath-hold imaging of highly diffusible (He) or soluble (Xe) gases with in vivo T1-times well below 1 min. Since helium is not absorbed in considerable amounts, its application is restricted to the lung. Xe-129 is also under investigation for imaging of white matter disease and functional studies of cerebral perfusion. Magnetic resonance imaging using hyperpolarized gases is emerging as a technical challenge and opportunity for the MR community. Preliminary experience suggests potential for functional imaging of pulmonary ventilation and cerebral perfusion.

Adult↗

PubMed1987

Effects of exposure to single or multiple combinations of the predominant toxic gases and low oxygen atmospheres produced in fires.

The toxicity of single and multiple fire gases is studied to determine whether the toxic effects of the combustion products from materials can be explained by the toxicological interactions (as indicated by lethality) of the primary fire gases or if minor, more obscure gases need to be considered. LC50 values for Fischer-344 rats have been calculated for the individual gases, carbon monoxide (CO), hydrogen cyanide (HCN), or decreased oxygen (O2), for 30-min exposures plus relevant postexposure periods using the NBS Toxicity Test Method. Combination experiments with CO and HCN indicate that they act in an additive manner. Synergistic effects have been found when the animals are exposed to certain combinations of CO and carbon dioxide (CO2). Five percent CO2 raised the threshold for deaths due to hypoxia and decreased the LC50 of HCN. Decreasing the O2 concentration in the presence of various mixtures of the other major fire gases increased the toxicity even further. A comparison of the concentrations of the major combustion products generated from a number of polymeric materials at their LC50 (30-min exposure plus 14-day postexposure) values with the combined pure gas results indicates that, in most cases, the observed toxicity may be explained by the toxicological interactions of the examined primary toxic fire gases. These results provide necessary information for the computer model currently being developed at the Center for Fire Research to predict the toxic hazard that people will experience under various fire scenarios.

Air↗

PubMedDate not supplied

Mutagenicity of rubber vulcanization gases in Salmonella typhimurium.

Gases formed by rubber and rubber additives in the vulcanization process were collected with a laboratory-scale glass apparatus. Mutagenicity testing of the vulcanization gases by the Salmonella/microsome test was conducted with strains TA1535, TA1538, TA98, and TA100 in the absence and presence of a metabolizing system from rat liver homogenates. The mutagenicity of gases derived by heating chloroprene rubber and ethylene propylene rubber was established with both base substitution- and frameshift-sensitive strains and that of a styrene-butadiene rubber was established with the base substitution-sensitive stain TA100. Tests on pyrolysis gases from a butadiene acrylonitrile rubber revealed only toxic effects. Curing systems, additives, and filling materials from various sources were represented in the material. Gases were collected at temperature levels corresponding to both mixing and curing of these particular rubbers in the industrial operations. Attempts were made to correlate the mutagenicity of the gases to the presence of mutagenic components in the rubber mixtures.

Acrylonitrile↗

PubMed1997

Calibration of a portable tritium-in-air monitor for various radioactive gases.

A commercially available portable tritium-in-air monitor was calibrated for detecting the concentration of tritium-in-air, 14C-in-air, and various radioactive noble gases. Calibrations were performed both experimentally, using assayed quantities of the calibration gases, and theoretically, by simulating the monitor's response using Monte Carlo code. The experimental and theoretical calibrations agreed within +/- 10% for all gases tested with the exception of 41Ar-in-air where the agreement was approximately 20%. The results show that, although the monitor can be used to measure a wide range of radioactive gases, if more than one gas is present the monitor can not be used to accurately determine the concentration of, and hazard posed by, these gases. It is also shown that the monitor's ability to accurately assess tritium-in-air hazards would be seriously compromised by the presence of other radioactive gases.

Air Pollutants, Radioactive↗

PubMed2000

An abiotic origin for hydrocarbons in the Allan Hills 84001 martian meteorite through cooling of magmatic and impact-generated gases.

Thermodynamic calculations of metastable equilibria were used to evaluate the potential for abiotic synthesis of aliphatic and polycyclic aromatic hydrocarbons (PAHs) in the martian meteorite Allan Hills (ALH) 84001. The calculations show that PAHs and normal alkanes could form metastably from CO, CO2, and H2 below approximately 250-300 degrees C during rapid cooling of trapped magmatic or impact-generated gases. Depending on temperature, bulk composition, and oxidation-reduction conditions, PAHs and normal alkanes can form simultaneously or separately. Moreover, PAHs can form at lower H/C ratios, higher CO/CO2 ratios, and higher temperatures than normal alkanes. Dry conditions with H/C ratios less than approximately 0.01-0.001 together with high CO/CO2 ratios also favor the formation of unalkylated PAHs. The observed abundance of PAHs, their low alkylation, and a variable but high aromatic to aliphatic ratio in ALH 84001 all correspond to low H/C and high CO/CO2 ratios in magmatic and impact gases and can be used to deduce spatial variations of these ratios. Some hydrocarbons could have been formed from trapped magmatic gases, especially if the cooling was fast enough to prevent reequilibration. We propose that subsequent impact heating(s) in ALH 84001 could have led to dissociation of ferrous carbonates to yield fine-grain magnetite, formation of a CO-rich local gas phase, reduction of water vapor to H2, reequilibration of the trapped magmatic gases, aromatization of hydrocarbons formed previously, and overprinting of the synthesis from magmatic gases, if any. Rapid cooling and high-temperature quenching of CO-, H2-rich impact gases could have led to magnetite-catalyzed hydrocarbon synthesis.

Alkanes↗

PubMed1998

Identification of gases responsible for the odour of human flatus and evaluation of a device purported to reduce this odour.

BACKGROUND/AIMS: While the social significance of flatus derives mainly from its odour, previous studies have focused on the non-odoriferous components of rectal gas. The aims of the present study were to determine the role of sulphur-containing gases in flatus odour and test the efficacy of a device purported to reduce this odour. METHODS: Flatus was quantitatively collected via rectal tube from 16 healthy subjects who ingested pinto beans and lactulose to enhance flatus output. The concentrations of sulphur-containing gases in each passage were correlated with odour intensity assessed by two judges. Odour intensity was also determined after treatment of flatus samples with zinc acetate, which binds sulphydryl compounds (hydrogen sulphide and methanethiol), or activated charcoal. Utilising gastight Mylar pantaloons, the ability of a charcoal lined cushion to adsorb sulphur-containing gases instilled at the anus of eight subjects was assessed. RESULTS: The main sulphur-containing flatus component was hydrogen sulphide (1.06 (0.2) mumol/l), followed by methanethiol (0.21 (0.04) mumol/l) and dimethyl sulphide (0.08 (0.01) mumol/l) (means (SEM)). Malodour significantly correlated with hydrogen sulphide concentration (p < or = 0.001). Zinc acetate reduced sulphur gas content but did not totally eliminate odour, while activated charcoal removed virtually all odour. The cushion absorbed more than 90% of the sulphur gases. CONCLUSION: Sulphur-containing gases are the major, but not the only, malodorous components of human flatus. The charcoal lined cushion effectively limits the escape of these sulphur-containing gases into the environment.

Adolescent↗

PubMed1973

Use of inert gases to study the interaction of blood flow and diffusion during passive absorption from the gastrointestinal tract of the rat.

Measurement of the relative absorption rates of inert gases (H(2), He, CH(4), SF(6), and (133)Xe) was used to investigate the interaction between diffusion and blood flow during passive absorption from the stomach, small bowel, and colon of the rat. If uptake is blood flow limited, the gases should be absorbed in proportion to their solubilities in blood, but if diffusion limited, uptake should be proportional to the diffusion rate of the gases in mucosal tissues. The observed absorption data were fitted to a series of models of interaction between perfusion and diffusion. A simple model accurately predicted the absorption rates of the gases from all segments of bowel. In this model, gas is absorbed into two distinct blood flows: one which flows in proximity to the lumen and completely equilibrates with the lumen, and a second which is sufficiently rapid and distant from the lumen that its gas uptake is entirely diffusion limited. The fraction of the total absorption attributable to the equilibrating flow can be readily calculated and equalled 93%, 77%, and 33% for the small bowel, colon, and stomach, respectively. Thus the rate of passive absorption of gases from the small bowel is limited almost entirely by the blood flow to the mucosa, and absorption from the stomach is largely limited by the diffusion rate of the gases. The flow which equilibrates with the lumen can be quantitated, and this flow may provide a useful measure of "effective" mucosal blood flow.

Animals↗

PubMed2002

[Regulations on gases for medical use in France].

In 1989, a European directive extended the definition of proprietary medicinal products, and consequently the necessity to hold a marketing authorization (MA), for all industrially manufactured products, including medicinal gases. In France, the directive 89/341/CEE was transposed in the French law on December 8(th), 1992 and France was the first Member State to implement provisions for the obtention of MAs for gases for medical use. Since then, France has stayed at the forefront in this area. Following the inclusion of gases in the scope of pharmaceutical products, gases require on MA obtained following the same methods as for drugs and be manufactured and distributed in authorized sites. Moreover, the European directive has led the French authorities to classify gases according to their use. Gases for medical use are thus considered either as medicinal products or as medical devices.

Drug Compounding↗