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PubMed1995

International Federation of Clinical Chemistry (IFCC), Committee on pH, Blood Gases and Electrolytes: approved IFCC recommendation on definitions of quantities and conventions related to blood gases and pH.

Terminology in blood pH and gas analysis can be confusing, both because more than one name has been used for the same quantity, and because the same name has been used for more than one quantity. In addition, several calculated quantities are commonly used, but in some cases many different algorithms have been published for a single quantity. This document contains definitions of the most useful quantities in blood pH and gas analysis, and presents algorithms for the most useful calculated quantities. Use of these should lessen confusion among users and should also result in data that are more comparable among laboratories.

Algorithms↗
PubMed2006

Intestinal gases and flatulence: possible causes of occurrence.

All gases entrapped in closed body cavities are destined to be partially or completely absorbed. Intestinal gases often accumulate and cause flatulence. This paper proposes a simple concept of intestinal gas occurrence based on our knowledge on gas resorption in other body cavities. Compliance of intestinal and abdominal walls makes pressure in the liquid chyme bubbles near 760 mmHg. Intestinal gases are from three sources. Air can be swallowed, CO2 come from the gastric acid neutralisation and from intestinal bacterial colonies that also produce hydrogen and methane. In continuously mixed liquid chyme, the total pressure of blood gases is similar or lower than in the venous blood ( or=760 mmHg). Some local production of bacterial gases with partial pressure of more than 90 mmHg is required, so the resulting small bowel bubbles would contain less than 20% of bacterial gases. If peristaltic mixing of chyme is prevented by an obstacle, local pressures of bacterial gases build up, form bubbles that fuse and finally make X-ray visible aeroliquid levels. Bacterial gases make almost 3/4 of the flatulence. Formation of bubbles destined to become flatulence might depend on altered rheological condition of the large bowel content, with local abundant production of bacterial gases near bacterial colonies. Gases are unable to diffuse rapidly through the dense liquid content and local accumulation allows formation of bubbles mainly of bacterial gases. Their pressure can be higher 760 mmHg, since they are stretching the thick content. Poor diffusion of gases keeps them almost free of blood gases and their entrance makes them bigger. As the content moves along the colon, the content is becoming more solid and gases are becoming entrapped in large bubbles. Some blood and bacterial gases are absorbed and exhaled, but the remaining quantity has no other escape except flatulence. Flatulence rich in bacterial gases might be the price for the large bowel water reabsorption. It seems that beside the peroral use of antibiotics active in the colon, little can be done to reduce flatulence.

Bacteria↗
PubMed1989

The sloping alveolar plateau of tracer gases washed out from mixed venous blood in man.

We have investigated the slope of the alveolar plateau for inert tracer gases that were washed out from mixed venous blood. Two pairs of tracer gases were used (He, SF6) and (C2H2, Freon 22). The gases of each pair share almost the same blood-gas partition coefficient but they have different diffusive properties in the gas phase. The experiments were performed in healthy subjects at rest and at three levels of exercise (75, 150, 225 W). Each experiment started with the alveolar washin of the tracer gases by adding these gases to inspired air. This washin was continued for several minutes in order to dissolve sufficient amounts of the tracer gases in the body tissues. Subsequently, the tracer gases were washed out. In this paper, the slopes of the alveolar plateaus are defined as the relative increase of the concentration per second. Steeper slopes were found for the heavier gases (SF6 and Freon 22) in comparison with those for the lighter gases of the two pairs (He and C2H2). This finding may be ascribed to the contribution of diffusion-limited gas mixing in the lung to the slope of the alveolar plateau. For each gas, the slope for the first expiration during washout (alveolar washout) was considerably smaller than that for the later part of washout (mixed venous washout), and the difference amounts to about 56% and 76% of the slope during mixed venous washout at rest and at the highest level of exercise, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylene↗
PubMed1990

Special considerations for conducting permeation testing of protective clothing materials with gases and chemical vapors.

Testing the permeation resistance of protective clothing materials against chemical gases and vapors requires attention to additional factors over conventional material permeation testing with liquids. Permeation testing factors relevant to gas and vapor challenges are described, and results for testing various material-gas combinations are reported. Challenging protective clothing materials with gases presents a series of special problems including gas delivery, cell integrity, sufficient analytical detection, and disposal. The concentration and other properties of gases and vapors are very sensitive to small changes in temperature and pressure. The method of delivering gases or vapors to the test cell must provide for careful regulation of these variables and maintain homogeneous contact of the chemical with the material over the test period. While many organic vapors are easily and directly detectable by gas chromatographic methods, several gases require special collection media and analytical procedures to achieve detection limits below 1 ppm. Handling of exhaust gas from the challenge chamber of the test cell must reflect safe laboratory practices without creating unnecessary chemical waste. Recommended procedures and results are presented for the six new gases added to ASTM Standard Guide F1001, Selection of Chemical Liquids and Gases to Evaluate Protective Clothing Materials, as well as for other difficult test gases used in evaluating protective clothing materials.

Air Pollutants↗
PubMed1998

A molecular description of how noble gases and nitrogen bind to a model site of anesthetic action.

UNLABELLED: How some noble and diatomic gases produce anesthesia remains unknown. Although these gases have apparently minimal capacities to interact with a putative anesthetic site, xenon is a clinical anesthetic, and argon, krypton, and nitrogen produce anesthesia at hyperbaric pressures. In contrast, neon, helium, and hydrogen do not cause anesthesia at partial pressures up to their convulsant thresholds. We propose that anesthetic sites influenced by noble or diatomic gases produce binding energies composed of London dispersion and charge-induced dipole energies that are sufficient to overcome the concurrent unfavorable decrease in entropy that occurs when a gas molecule occupies the site. To test this hypothesis, we used the x-ray diffraction model of the binding site for Xe in metmyoglobin. This site offers a positively charged moiety of histidine 93 that is 3.8 A from Xe. We simulated placement of He, Ne, Ar, Kr, Xe, H2, and N2 sequentially at this binding site and calculated the binding energies, as well as the repulsive entropy contribution. We used free energies obtained from tonometry experiments to validate the calculated binding energies. We used partial pressures of gases that prevent response to a noxious stimulus (minimum alveolar anesthetic concentration [MAC]) as the anesthetic endpoint. The calculated binding energies correlated with binding energies derived from the in vivo (ln) data (RTln[MAC], where R is the gas constant and T is absolute temperature) with a slope near 1.0, indicating a parallel between the Xe binding site in metmyoglobin and the anesthetic site of action of noble and diatomic gases. Nonimmobilizing gases (Ne, He, and H2) could be distinguished by an unfavorable balance between binding energies and the repulsive entropy contribution. These gases also differed in their inability to displace water from the cavity. IMPLICATIONS: The Xe binding site in metmyoglobin is a good model for the anesthetic sites of action of noble and diatomic gases. The additional binding energy provided by induction of a dipole in the gas by a charge at the binding site enhanced binding.

Anesthetics↗