Continuous measurement of gas uptake and elimination in anesthetized patients using an extractable marker gas.

Measurement of pulmonary gas uptake and elimination is often performed, using nitrogen as marker gas to measure gas flow, by applying the Haldane transformation. Because of the inability to measure nitrogen with conventional equipment, measurement is difficult during inhalational anesthesia. A new method is described, which is compatible with any inspired gas mixture, in which fresh gas and exhaust gas flows are measured using carbon dioxide as an extractable marker gas. A system was tested in eight patients undergoing colonic surgery for automated measurement of uptake of oxygen, nitrous oxide, isoflurane, and elimination of carbon dioxide with this method. Its accuracy and precision were compared with simultaneous measurements made with the Haldane transformation and corrected for predicted nitrogen excretion by the lungs. Good agreement was obtained for measurement of uptake or elimination of all gases studied. Mean bias was -0.003 l/min for both oxygen and nitrous oxide uptake, -0.0002 l/min for isoflurane uptake, and 0.003 l/min for carbon dioxide elimination. Limits of agreement lay within 30% of the mean uptake rate for nitrous oxide, within 15% for oxygen, within 10% for isoflurane, and within 5% for carbon dioxide. The extractable marker gas method allows accurate and continuous measurement of gas uptake and elimination in an anesthetic breathing system with any inspired gas mixture.     

Oxygen as a driving gas for nebulisers: safe or dangerous?

Changes in blood gas tensions occurring when 100% oxygen or air was used as the driving gas for nebulised salbutamol were studied in 23 patients with severe airways obstruction. The patients fell into three groups: nine had chronic bronchitis and emphysema with carbon dioxide retention, seven had emphysema and chronic bronchitis without carbon dioxide retention, and seven had severe asthma (no carbon dioxide retention). When oxygen was used as the driving gas patients who retained carbon dioxide showed a mean rise of 1.03 kPa (7.7 mm Hg) in their pressure of carbon dioxide (Pco2) after 15 minutes (p less than 0.001) but the Pco2 returned to baseline values within 20 minutes of stopping the nebuliser. The other two groups showed no rise in Pco2 with oxygen. When air was used as the driving gas none of the groups became significantly more hypoxic. Although it is safe to use oxygen as the driving gas for nebulisers in patients with obstructive airways disease with normal Pco2, caution should be exercised in those who already have carbon dioxide retention.     

Production of methanol from methane by methanotrophic bacteria

Methanotrophs can oxidize methane to carbon dioxide through sequential reactions catalyzed by a series of enzymes including methane monooxygenase, methanol dehydrogenase, formaldehyde dehydrogenase, and formate dehydrogenase. When suspensions of methanotrophic bacteria of Methylosinus trichosporium IMV 3011 were incubated at 32°C with methane and oxygen, there was an extracellular accumulation of methanol from methane oxidation in response to carbon dioxide addition. Maximal accumulation of methanol was achieved with 40% carbon dioxide in the mixed reaction gases. A continuous experiment was performed in a continuous ultrafiltration reactor. The optimum gas mixture containing 20% (v v^?1) methane, 20% oxygen, 20% nitrogen and 40% carbon dioxide was used to provide substrates and to maintain the transmembrane pressure. The product (methanol) was removed in the eluate buffer. The initial methanol concentration in the eluate buffer was 8.22 μmol L^?1. The bioreactor was operated continuously for 198 h without obvious loss of productivity.     

Production of methanol from methane by methanotrophic bacteria

Methanotrophs can oxidize methane to carbon dioxide through sequential reactions catalyzed by a series of enzymes including methane monooxygenase, methanol dehydrogenase, formaldehyde dehydrogenase, and formate dehydrogenase. When suspensions of methanotrophic bacteria of Methylosinus trichosporium IMV 3011 were incubated at 32°C with methane and oxygen, there was an extracellular accumulation of methanol from methane oxidation in response to carbon dioxide addition. Maximal accumulation of methanol was achieved with 40% carbon dioxide in the mixed reaction gases. A continuous experiment was performed in a continuous ultrafiltration reactor. The optimum gas mixture containing 20% (v v^-1) methane, 20% oxygen, 20% nitrogen and 40% carbon dioxide was used to provide substrates and to maintain the transmembrane pressure. The product (methanol) was removed in the eluate buffer. The initial methanol concentration in the eluate buffer was 8.22 μmol L^-1. The bioreactor was operated continuously for 198 h without obvious loss of productivity.     

Extension of the Functional Range of Respiratory and Gas Exchange Responses in Repetitive Hypoxia

External respiration and gas exchange were studied in healthy volunteers during a session of intermittent normobaric hypoxia (INH) consisting of three cycles of breathing alternately a hypoxic mixture (10.7% O₂) for 5 min and normal air for 5 min. The ventilatory response increased in the successive cycles of hypoxia and gradually decreased during the normoxic intervals. These changes were accompanied by an increase in carbon dioxide in lung air, which was not eliminated by the increased pulmonary ventilation during the hypoxic intervals. However, the mean oxygen consumption did not change during the INH session because the ventilatory reactivity and breathing depth, as well as the efficiency of oxygen utilization, increased from cycle to cycle.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 3, 2005, pp. 100–107.Original Russian Text Copyright © 2005 by Krivoshchekov, G. Divert, V. Divert.     

Gas phase composition effects on suspension cultures of Taxus cuspidata

The effect of different concentrations and combinations of oxygen, carbon dioxide, and ethylene on cell growth and taxol production in suspension cultures of Taxus cuspidata was investigated using several factorial design experiments. Low head space oxygen concentration (10% v/v) promoted early production oftaxol. High carbon dioxide concentration (10% v/v) inhibited taxol production. The most effective gas mixture composition in terms of taxol production was 10% (v/v) oxygen, 0.5% (v/v) carbon dioxide, and 5 ppm ethylene. Cultures grown underambient concentration of oxygen had a delayed uptake of glucose and fructose compared to cultures grown under 10% (v/v) oxygen. Average calcium uptake rates into the cultured cells decreased and average phosphate uptake rates increased as ethylene was increased from 0 to 10 ppm. These results may indicate that gas composition alters partitioning of nutrients, which in turn affects secondary metabolite production. (c) 1995 John Wiley & Sons, Inc.     

Gas Exchange of Algae: II. Effects of Oxygen, Helium, and Argon on the Photosynthesis of Chlorella pyrenoidosa

Changes in the oxygen partial pressure of air over the range of 8 to 258 mm of Hg did not adversely affect the photosynthetic capacity of Chlorella pyrenoidosa. Gas exchange and growth measurements remained constant for 3-week periods and were similar to air controls (oxygen pressure of 160 mm of Hg). Oxygen partial pressures of 532 and 745 mm of Hg had an adverse effect on algal metabolism. Carbon dioxide consumption was 24% lower in the gas mixture containing oxygen at a pressure 532 mm of Hg than in the air control, and the growth rate was slightly reduced. Oxygen at a partial pressure of 745 mm of Hg decreased the photosynthetic rate 39% and the growth rate 37% over the corresponding rates in air. The lowered metabolic rates remained constant during 14 days of measurements, and the effect was reversible after this time. Substitution of helium or argon for the nitrogen in air had no effect on oxygen production, carbon dioxide consumption, or growth rate for 3-week periods. All measurements were made at a total pressure of 760 mm of Hg, and all gas mixtures were enriched with 2% carbon dioxide. Thus, the physiological functioning and reliability of a photosynthetic gas exchanger should not be adversely affected by: (i) oxygen partial pressures ranging from 8 to 258 mm of Hg; (ii) the use of pure oxygen at reduced total pressure (155 to 258 mm of Hg) unless pressure per se affects photosynthesis, or (iii) the inclusion of helium or argon in the gas environment (up to a partial pressure of 595 mm of Hg).     

The role of prostaglandins in the production of erythropoietin (ESF) by the kidney. II. Effects of indomethacin on erythropoietin production following hypoxia in dogs

In order to determine the sequence of events leading to the increase in ESF production following renal hypoxia, the possible role of prostaglandins in the generation of ESF by the kidney was assessed. ESF production following exposure to hypoxia and indomethacin (I) treatment were studied in dogs. Plasma ESF titers were measured in carotid artery blood before the hypoxic stimulus, and after 1, 3 and 5 hours exposure. It was found that plasma ESF levels were significantly elevated in 6 dogs exposed to an hypoxic stimulus while anesthetized with pentobarbital by breathing an atmosphere of reduced oxygen (8% oxygen, 5% carbon dioxide and 87% nitrogen) for 3 and 5 hours. On the other hand, 6 dogs exposed to this hypoxic stimulus and pretreated with indomethacin (5 mg/kg orally 2 x), a drug which inhibits prostaglandins synthesis, did not show a significant increase in plasma ESF levels after exposure to hypoxia as compared to controls. These results indicate that renal prostaglandins play a role in ESF production after an hypoxic stimulus.     

Effect of respiratory gases on compliance of intrapulmonary arteries and veins

A method was developed that permitted changes in the pressure-volume characteristics of large intrapulmonary vessels occurring with changes in the composition of alveolar gas to be studied in excised lungs. The capillary bed was emptied by keeping intravascular pressure well below alveolar pressure, and the relationship between changes in the volume of the pulmonary arteries or veins with changes in transpulmonary pressure was measured. The volume of the arteries and veins always decreased with a decrease in transpulmonary pressure, but when the alveoli contained carbon dioxide, the decrease in vascular volume was less, for the same decrease in transpulmonary pressure, than when the alveoli contained oxygen or nitrogen without carbon dioxide. This change with carbon dioxide was probably due to a decrease in the compliance of the larger intrapulmonary arteries and veins. Since there was no pathway for carbon dioxide to enter these vessels except by diffusion from the alveoli, it is concluded that carbon dioxide can act directly on the intrapulmonary arteries and veins to reduce their compliance, but it is not known whether this effect has physiological significance. No effect on the large pulmonary vessels was found with variations in alveolar concentrations of oxygen. blood vesselsblood volumecarbon dioxidediffusionlungspulmonary circulation     

The effect of hypoxia on performance during 30 s or 45 s of supramaximal exercise

The purpose of this study was to evaluate the effect of hypoxia (10.8 +/- 0.6% oxygen) on performance of 30 s and 45 s of supramaximal dynamic exercise. Twelve males were randomly allocated to perform either a 30 s or 45 s Wingate test (WT) on two occasions (hypoxia and room air) with a minimum of 1 week between tests. After a 5-min warm-up at 120 W subjects breathed the appropriate gas mixture from a wet spirometer during a 5-min rest period. Resting blood oxygen saturation was monitored with an ear oximeter and averaged 97.8 +/- 1.5% and 83.2 +/- 1.9% for the air (normoxic) and hypoxic conditions, respectively, immediately prior to the WT. Following all WT trials, subjects breathed room air for a 10-min passive recovery period. Muscle biopsies from the vastus lateralis were taken prior to and immediately following WT. Arterialized blood samples, for lactate and blood gases, were taken before and after both the warm-up and the performance of WT, and throughout the recovery period. Open-circuit spirometry was used to calculate the total oxygen consumption (VO2), carbon dioxide production and expired ventilation during WT. Hypoxia did not impair the performance of the 30-s or 45-s WT. VO2 was reduced during the 45-s hypoxic WT (1.71 +/- 0.21 l) compared with the normoxic trial (2.16 +/- 0.26 l), but there was no change during the 30-s test (1.22 +/- 0.11 vs 1.04 +/- 0.17 l for the normoxic and hypoxic conditions, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

In vitro cultivation of Dipetalonema viteae third-stage larvae: effect of the gas phase

The effect of the gas phase on the in vitro growth and development of Dipetalonema viteae (Nematoda: Filarioidea) third-stage larvae obtained from the tick vector and 3 day infections of jirds was examined. Measurements of the oxygen (pO2) and carbon dioxide (pCO2) tensions and the pH in the medium were made for each gas phase. In cultures gassed with 5% carbon dioxide in nitrogen the pO2 was between 32 and 50 mm Hg, the pCO2 ranged from 25 to 40 mm Hg and the pH was between 7.2 and 7.4. This gas phase resulted in the best growth and development of third-stage larvae to the fourth-stage. Survival and development of larvae were decreased in cultures with oxygen tensions less than 20 mm Hg and greater than 50 mm Hg.     

Anaerobic mineralization of cholesterol by a novel type of denitrifying bacterium

A novel denitrifying bacterium, strain 72Chol, was enriched and isolated under strictly anoxic conditions on cholesterol as sole electron donor and carbon source. Strain 72Chol grew on cholesterol with oxygen or nitrate as electron acceptor. Strictly anaerobic growth in the absence of oxygen was demonstrated using chemically reduced culture media. During anaerobic growth, nitrate was initially reduced to nitrite. At low nitrate concentrations, nitrite was further reduced to nitrogen gas. Ammonia was assimilated. The degradation balance measured in cholesterol-limited cultures and the amounts of carbon dioxide, nitrite, and nitrogen gas formed during the microbial process indicated a complete oxidation of cholesterol to carbon dioxide. A phylogenetic comparison based on total 16S rDNA sequence analysis indicated that the isolated micro-organism, strain 72Chol, belongs to the β2-subgroup in the Proteobacteria and is related to Rhodocyclus, Thauera, and Azoarcus species. Received: 16 July 1996 / Accepted: 5 December 1996     

Immunohistochemically demonstrated increase of prostaglandin F2-alpha in neurons after reoxygenation in anoxic rats

Immunohistochemical staining for prostaglandin F2-alpha (PG F2 alpha) was conducted to identify PG F2 alpha synthesizing or binding sites in anoxic rat brains. Anoxia was produced in 22 rats to lower the arterial oxygen tension (PaO2) to 21 +/- 4 mmHg by ventilation with a 95% nitrogen and 5% carbon dioxide gas mixture. In 8 animals anoxia was continued for 30 sec, and in 14 rats for 3 min. Prior to decapitation, 5 animals in the 30-sec anoxia group and 8 rats in the 3-min anoxia group were reoxygenated for 5 min, while the remaining 9 were not. Five-min reoxygenation returned the PaO2 to 106 +/- 7. Three non-reoxygenated and 3 reoxygenated rats, all pretreated with indomethacin, and 5 normal rats served as controls. The brains were snap-frozen. The cryosections were stained by the indirect immunofluorescence method. PG F2 alpha was noted mainly in pial vessels in all normal rats. All reoxygenated rats showed a positive reaction not only in blood vessels, but also in neurons, particularly hippocampal neurons and Purkinje cells. The staining of the above neurons was noted to be less in non-reoxygenated rats. The stronger staining was observed in rats reoxygenated after 3-min anoxia than 30-sec anoxia. The indomethacin-pretreated rats showed almost no increase in staining intensity. The above results indicate that reoxygenation after anoxia results in an increase of PG F2 alpha in neurons of both cerebrum and cerebellum.     

Effects of oxygen,carbon dioxide,and nitrogen on hatching behavior and hatching time in the katydid,Eobiana engelhardti subtropica Bey-Bienko (Orthoptera: Tettigoniidae)

The trigger for the hatching behavior and determination of hatching time of the katydids, Eobiana engelhardti subtropica (Orthoptera: Tettigoniidae) have been shown to be influenced by light–dark signals or temperature. In this study, I investigated the effects of oxygen, carbon dioxide, and nitrogen on the hatching behavior and hatching time of the katydid. Eggs rarely hatched under a constant temperature of 25°C and hatched sporadically at a constant temperature of 15°C under continuous light in the air. However, when eggs were exposed to 100% oxygen or a mixture of oxygen and nitrogen (2:1 or 1:1), hatching occurred within a few seconds. Hatching behavior was directly triggered by high concentrations of oxygen. It was inhibited by exposure to 100% carbon dioxide, 100% nitrogen, or a mixture of oxygen and nitrogen (1:2). The hatching time, determined by the temperature fall (transfer from 25°C to 15°C), was delayed by these gases, and was reset by the transfer back of eggs to the air. This suggests the existence of a time-measuring mechanism that is triggered by the transfer of eggs to the air. These results, indicating that hatching behavior was directly triggered by high concentrations of oxygen and that hatching time was set by the transfer from carbon dioxide or nitrogen to the air, are new findings to the best of my knowledge.     

Arterial Blood Gas Tensions and pH in Acute Asthma in Childhood

Studies of the arterial blood gas tensions and pH in 21 children during 24 acute attacks of asthma showed that all were hypoxic on admission to hospital, and in 10 there was evidence of carbon dioxide retention. Cyanosis, invariably present when the So₂ was below 85%, and restlessness in patients breathing air were the most reliable indices of the severity of hypoxia. There were no reliable clinical guides to the Pco₂ level. Conventional oxygen therapy in tents (25–40%) did not always relieve hypoxia, and in three cases the administration of oxygen at a concentration of 40% or over failed to produce a normal arterial oxygen tension. Uncontrolled oxygen therapy may aggravate respiratory acidosis, and three of our patients developed carbon dioxide narcosis while breathing oxygen. The necessity for blood gas measurements in the management of severe acute asthma in childhood is emphasized.     

Effect of oxygen and carbon dioxide on germination and growth ofRhizopus oligosporus on model media and soya beans

 The microcolony technique enables the effects of several atmospheric conditions on fungal growth to be studied by measuring the radius of the colony, while excluding effects of those conditions on germination of the sporangiospores. Various concentrations of oxygen and carbon dioxide in the gas environment were found to influence growth of Rhizopus oligosporus on malt extract/soya peptone/agar. The maximum radial growth rate was 1.48 mm/h and the maximum specific growth rate was 0.109 h^-1 at 30 °C. Oxygen became limiting below 1% (v/v), but growth remained possible at levels of 0.001% oxygen. Carbon dioxide stimulated growth at limiting oxygen levels. The specific growth rate increased from 0.043 h^-1 at 0.5% (v/v) oxygen and 0% (v/v) carbon dioxide to 0.096 h^-1 at 0.5% (v/v) oxygen and 5% (v/v) carbon dioxide. A mixture of 0.5% (v/v) oxygen and 35% (v/v) carbon dioxide inhibited growth. Delay of sporangiospore germination due to low (less than 0.001%) amounts of oxygen was not observed with the techniques used. Fungal activity in a rotating drum fermentor was more strongly affected by low levels of oxygen than was biomass formation on model media. High concentrations of carbon dioxide inhibited growth in the rotating drum fermentor at non-limiting levels of oxygen. It is concluded that aeration and heat removal are both essential aspects of optimization of large-scale solid-substrate bioreactors with Rh. oligosporus. Received: 5 August 1994/Received revision: 14 November 1994/Accepted: 5 December 1994     

Fermentation of methane

From soil and from the plant Elodea, we have isolated an organism which has not, yet been identified; it is a comparatively large Bacillus, which thriven in a medium of mineral salts saturated with a gaseous mixture of 40%, methane (or natural gas), 40% oxygen, 15% nitrogen, and 5% carbon dioxide. The isolated cells have amino acid and vitamin contents comparable to, or, in some cases greater than, those found in such nutrients as yeast, fish meal, or milk solids.     

Breathing hypoxic gas affects the physiology as well as the diving behaviour of tufted ducks

We measured the effects of exposure to hypoxia (15% and 11% oxygen) and hypercapnia (up to 4.5% carbon dioxide) on rates of respiratory gas exchange both between and during dives in tufted ducks, Aythya fuligula, to investigate to what extent these may explain changes in diving behaviour. As found in previous studies, the ducks decreased dive duration (t(d)) and increased surface duration when diving from a hypoxic or hypercapnic gas mix. In the hypercapnic conditions, oxygen consumption during the dive cycle was not affected. Oxygen uptake between dives was reduced by only 17% when breathing a hypoxic gas mix of 11% oxygen. However, estimates of the rate of oxygen metabolism during the foraging periods of dives decreased nearly threefold in 11% oxygen. Given that tufted ducks normally dive well within their aerobic dive limits and that they significantly reduced their t(d) during hypoxia, it is not at all clear why they make this physiological adjustment.     

The Effect of Storage in Various Gaseous Atmospheres on the Microflora of Lamb Chops Held at—1°C

The effect of different gaseous atmospheres on the development of the bacterial flora on lamb chops stored at –1°C was examined. The atmospheres were air, nitrogen, hydrogen, and mixtures of air + carbon dioxide, oxygen + nitrogen, oxygen + carbon dioxide, nitrogen + carbon dioxide and hydrogen + carbon dioxide (gas ratio = 80:20, v/v). Storage life of chops ranged from two weeks in air to eight weeks in oxygen-free atmospheres. At the end of storage life Microbacterium thermosphactum was present as a major constituent of the bacterial flora in all atmospheres. In oxygen + carbon dioxide it was the predominant organism. In all other oxygen containing atmospheres, Pseudomonas spp. made up a large proportion of the flora. Strains of Enterobacteriaceae occurred in low-oxygen and oxygen-free atmospheres, and Lactobacillus spp. occurred in oxygen-free atmospheres.     

Methanogenesis from volatile fatty acids in downflow stationary fixed-film reactor

Methanogenesis was studied in downflow stationary fixed-film bioreactors. The support materials in this study included ceramic Raschig rings, hardwood chips, and sized charcoal. The performances of these support materials have been compared using both synthetic acid mixture and acid products obtained from paper mill sludge. Woodchips appeared to be the most promising support material: The maximum methane productivity of 3.56 L/L day at a nominal retention time of 0.78 day was obtained using initial total acid concentrations of 9.125 g/L. Higher productivity was achieved at the cost of efficiency of the process in terms of conversion of acids. From nitrogen balances, it was deduced that ammonia supplemented methane generation by supplying hydrogen for there duction of carbon dioxide.An ionic balance was developed to ascertain the relationship between the composition and the pH of the liquid and the mole fraction of carbon dioxide in the gas phase. From these ionic balance equations, it was possible to predict the gas phase composition at various retention times. The maximum error between the computed and the experimental values was less than 13%.