Ml Of Carbon Dioxide Research Articles

Decrease in the Adsorption Capacity of Adsorbents in the High-Temperature Carbonate Loop Process for CO2 Capture

In this study, the sorption capacity of limestone samples for CO2 was investigated to determine the conditions under which they can be used in the high-temperature carbonate loop process. For the work, limestone samples from the Czech Republic were used, which contained a high proportion of CaO (more than 97 wt.%). A total of 20 cycles of calcination (950 °C) and subsequent CO2 sorption–carbonation (650 °C) were performed for each limestone sample tested. The sorption capacity towards CO2 in the 20th cycle was less than 10% of the value determined in the first carbonation cycle of the samples and the most significant decrease was observed between the first and second cycles. The highest sorption capacity was determined for the Branžovy sample, which captured 268 mL of CO2/per 1 g of sorbent by chemisorption. Only 15 mL of carbon dioxide per 1 g of sorbent was bound by physisorption. However, in repeated use, the Vitošov limestone had the highest sorption capacity for CO2. For all samples, the amount of carbon dioxide bound by physisorption was in the range of 4 to 10% of the amount bound by chemisorption. Due to sintering of the material, the BET specific surface area decreased by 95 to 96%.

Carboxytherapy: Controls the inflammation and enhances the production of fibronectin on wound healing under venous insufficiency.

To examine the influence of carboxytherapy on wound healing under venous insufficiency, full-thickness excisional wounds were created on Wistar rats. We used three groups with 32 rats each: Group (I): daily cleaning with 0.9% saline solution; Group Sulfadiazine (II): 1% silver sulfadiazine; and Carboxytherapy (III): subcutaneous application of 0.3 mL of carbon dioxide. The predetermined periods of analysis were the 3rd, 7th, 14th, and 30th day. The slides were stained with haematoxylin and eosin and Picrosirius red and submitted for immunohistochemistry. Groups II and III presented a statistically significant decrease in relation to the presence of neutrophilic and lymphocytic infiltrates. The presence of collagen significant increased in groups II and III. However, group III presented better organisation. Only group I maintained the neovascularisation until the 30th day. The new epithelium statistically significantly increased in groups II and III. On immunohistochemistry, regarding fibronectin expression, only group III demonstrated a statistically significant increase since the beginning of the healing process. Thus, the use of carboxytherapy promotes the formation of a tissue better structured and that may be an important resource for the treatment of wounds under venous insufficiency, especially those of recurrent re-openings.

Portopulmonary venous anastomosis in balloon‐occluded retrograde transvenous obliteration for the treatment of gastric varices

Several reports have described portopulmonary venous anastomosis (PPVA). However, in balloon-occluded retrograde transvenous obliteration (BRTO), attention has not been paid to paradoxical embolism. The objective of this study was to investigate the existence of a right-left shunt due to PPVA when the drainage vein is occluded by a balloon during BRTO. The subjects were 19 patients who underwent BRTO. Whether PPVA was present was confirmed on balloon-occluded retrograde transvenous venography (BRTV). After BRTV, a retrograde bolus injection of 20 mL of carbon dioxide (CO2 ) via the balloon catheter was performed under balloon occlusion, and the flow of bubbles into both ventricles was observed with four-chamber view echocardiography. During the same balloon occlusion, bolus injection of CO2 into the inferior vena cava was performed, followed by echocardiography. PPVA was confirmed on BRTV in four patients (21.1%). On echocardiography with retrograde CO2 injection, bubbles were confirmed in the left ventricle in six patients (31.6%). On echocardiography with CO2 injection into the inferior vena cava, bubbles were not confirmed in the left ventricle in any cases. When the draining vein was occluded with a balloon and blood flow in a gastrorenal or gastrocaval shunt was stopped during BRTO, PPVA was confirmed in 21.1% of cases on retrograde angiography, and a right-left shunt was confirmed in 31.6% of cases on echocardiography.

Effect of pelvic floor muscle contraction on vesical and rectal function with identification of puborectalis-rectovesical inhibitory reflex and levator-rectovesical excitatory reflex

The effects of pelvic floor muscle contraction on rectal and vesical function were studied in 19 healthy volunteers with the aim of shedding light on some of the hitherto vague aspects of the mechanisms involved in micturition and defecation and their disorders. Rectal and vesical pressures were recorded during puborectalis (PR) and levator ani (LA) muscle stimulation with the rectum or urinary bladder empty and full. Muscle stimulation was effected by needle EMG electrode. The pressure responses to stimulation of the PR and LA muscles were also recorded with these muscles and the rectum and urinary bladder individually anesthetized in 12 of the 19 subjects. The test was repeated using saline instead of xylocaine. PR and LA muscle stimulation produced no pressure response in the empty rectum or bladder. Upon rectal balloon distension with a mean of 156.6+/-34.2 ml of carbon dioxide the mean rectal pressure was 64.6+/-18.7 cm H2O, the subject felt the urge to evacuate and the balloon was expelled to the exterior. On PR muscle stimulation at rectal distension with the above volume, the subject did not feel the urge to evacuate, the rectal pressure was 8.2+/-1.6 cm H2O and the balloon was not expelled. Upon LA stimulation at the same volume, the urge persisted, the rectal pressure was higher and the balloon was expelled. Vesical filling with a mean of 378.2+/-23.6 ml of saline initiated the urge to urinate and elevated the vesical pressure. PR muscle stimulation at this volume aborted the urge and pressure elevation, while LA stimulation caused more elevation of the vesical pressure and spontaneous micturition. Bladder filling with a mean of 423.6+/-38.2 ml produced high vesical pressure and spontaneous urination, both of which were prevented by PR muscle stimulation but not by LA muscle stimulation. Stimulation of the PR and LA muscles during individual anesthetization of the rectum, bladder or PR and LA muscles resulted in no significant rectal or vesical pressure changes. Repetition of the test using saline instead of xylocaine resulted in rectal and vesical pressure responses similar to those without the use of saline. In conclusion, the decline in rectal and vesical responses upon PR muscle contraction indicates a reflex relationship which we term 'puborectalis rectovesical inhibitory reflex'. This reflex is suggested to abort the urge to defecate or urinate. In contrast, LA muscle contraction produced rectal and vesical pressure elevation which is suggested to be mediated through the 'levator rectovesical excitatory reflex'. 'This reflex is probably evoked to promote rectal and vesical evacuation.

CO2 digital subtraction angiography for renal artery angioplasty in high-risk patients.

The efficacy of CO2 digital subtraction angiography for performing renal artery angioplasty in high-risk patients was evaluated. From January 1997 to July 1998, 21 high-risk patients underwent 29 renal artery angioplasties using carbon dioxide as the principal contrast agent. Six patients had a known allergy to iodinated contrast material and 15 had elevated levels of creatinine. Iodinated contrast material was used only if necessary. All periprocedural allergic reactions were recorded. Before and 24 hr after the procedure, serum creatinine levels were obtained. If the creatinine level had become significantly elevated (>0.5 mg/dl), the creatinine level was acquired a second time. Twenty-one patients (13 men and eight women) underwent 29 angioplasties (two were bilateral and six were repeated). Four kidney transplantation patients had ostial stenosis and the remaining 17 patients had nonostial stenosis. For all patients except one angioplasty initially was a technical success, as defined by a residual stenosis of less than 30%. Supplemental iodinated contrast material was used in only six patients (average dose, 8.5 ml). A range of 80-200 ml of carbon dioxide per procedure was used (average dose, 114.6 ml). One renal artery dissection occurred, which was unrelated to the carbon dioxide. There were no allergic reactions. The level of serum creatinine remained the same after 11 procedures, decreased after 12 procedures, and increased minimally after four procedures (<0.5 mg/dl). On the basis of our preliminary findings in a small group of patients, using carbon dioxide as an intravascular contrast agent to perform renal artery angioplasty in patients who have an allergy to iodinated contrast material or who suffer from renal insufficiency is safe and efficacious.

A Study of the Effect of Distension of the Rectosigmoid Junction on the Rectum and Anal Canal with Evidence of a Rectosigmoid-Rectal Reflex

Purpose.To elucidate the role of the rectosigmoid junction (RSJ) in the mechanism of defecation.Method.Fourteen healthy volunteers were enrolled in the study (10 men, 4 women; mean age 38.2 ± 10.6 years). The pressures in the rectum, anal canal, and RSJ as well as rectal balloon expulsion were recorded in response to balloon distension of the RSJ in increments of 10 ml of carbon dioxide (CO2) to 50 ml. The experiments were repeated after individual anesthetization of the RSJ, rectum, and anal canal. The expulsion of a 50-ml distended balloon located in the anesthetized rectum was tested.Results.RSJ distension with 10 ml of CO2produced no significant pressure changes in the RSJ, rectum, or anal canal. A 20-ml distension effected a significant pressure rise in the RSJ (P< 0.05) and the rectum (P< 0.01) and a decline in the anal canal (P< 0.05); the rectal balloon was expelled to the exterior. Similar pressure changes (P> 0.05) were recorded with a 30-, 40-, and 50-ml balloon distension. The mean latency for the RSJ response was 12.6 ± 2.2 ms and for the rectum 15.8 ± 2.6 ms. The balloon, distended with 50 ml of CO2and located in the rectum, was not expelled to the exterior. Balloon expulsion occurred only with distension with volumes of above 80 ml. Individual anesthetization of the RSJ, rectum, and anal canal followed by RSJ distension produced no significant pressure changes in RSJ, rectum, and anal canal as well as no rectal balloon expulsion.Conclusion.The rectal contraction upon RSJ distension affirms the hypothesis of the possible involvement of a reflex, which we term “rectosigmoid-rectal reflex.” This reflex relationship is evidenced by reproducibility and its absence on anesthetization of either the RSJ or the rectum, both presumably representing the two arms of the reflex arc. It is postulated that stools passing from the sigmoid colon to the rectum distend the RSJ and evoke the rectosigmoid-rectal reflex, which produces rectal contraction. The role of the reflex in defecation disorders needs to be studied.

Inflammatory pancreatic masses: differentiation from ductal carcinomas with contrast-enhanced sonography using carbon dioxide microbubbles.

The aim of this study was to evaluate the clinical efficacy of contrast-enhanced sonography using carbon dioxide microbubbles to differentiate inflammatory pancreatic masses from ductal carcinomas of the pancreas. Fifty-five patients, including 35 patients with ductal carcinomas and 20 with inflammatory pancreatic masses, underwent contrast-enhanced sonography, CT, and digital subtraction angiography (DSA). Carbon dioxide microbubbles were prepared by mixing 10 ml of carbon dioxide and the same amount of 25% soybean oil vigorously. Carbon dioxide microbubbles were injected through an angiographic catheter that was placed in the celiac axis. Vascularity of the tumors as determined by those three techniques was interpreted by three physicians who had no knowledge of the pathologic results. Contrast-enhanced sonography was best at revealing tumor vascularity among the three techniques. On contrast-enhanced sonography, 19 (95%) of the 20 inflammatory pancreatic masses were isovascular and 32 (91%) of the 35 ductal carcinomas were hypovascular. In contrast, the isovascularity of inflammatory masses was five (25%) on CT, and two (10%) on DSA, respectively. The sensitivity and accuracy rate of differentiating both diseases on contrast-enhanced sonography were 98% and 95%, respectively; on CT, they were both 73%; and on DSA they were both 67%. From our results, an isovascular mass is probably an inflammatory mass, whereas a hypovascular mass is most likely a ductal carcinoma on contrast-enhanced sonography. Contrast-enhanced sonography can help differentiate an inflammatory pancreatic mass from a ductal carcinoma.

Supercritical Fluid Extraction of Pesticide Residues from Strawberries

A supercritical fluid extraction (SFE) method for the determination in strawberries of a number of commonly used organochlorine insecticides, organophosphorus pesticides, and dichloroanilide fungicides is described. Gas chromatography was used to examine the extracts, with both electron-capture detection and either flame photometric or nitrogen phosphorus detection. Confirmation was performed by gas chromatography-mass spectrometry. The analytes were extracted with supercritical carbon dioxide at 4000 psi and 50 °C with a run time of 20 min, which corresponded to an extraction volume of 20-30 mL of carbon dioxide. In developing the method, the operating parameters of temperature, pressure, extraction time, collection solvent, and sample preparation were optimized. Recoveries ranged from 74 to 126% (with the exception of iprodione), and a method precision of ±3-18% was obtained for spiking levels of 0.08-3.7 mg/kg. The method was validated for the following organochlorine insecticides and organophosphorus pesticides: aldrin, dichloran, dieldrin, p,p'-DDE(TDE), p,p'-DDD, p,p'-DDT, α-endosulfan, β-endosulfan, endosulfan sulfate, diazinon, dichlorvos, ethion, malathion, methyl parathion, methyl pirimiphos, mevinphos E+Z, and parathion; and the following dichloroanilide fungicides: iprodione, procymidone, and vinclozolin. The SFE procedure was quicker, more environmentally friendly, and more cost effective than the traditional solvent extraction methods.

Effects of intracoronary carbon dioxide on left ventricular function in swine.

Carbon dioxide is currently used as an arterial and venous contrast agent; however, little is known of its effects on left ventricular function. This study was undertaken to investigate those effects. Ascending doses of 5, 10, and 20 ml of carbon dioxide were administered into the left main coronary artery of domestic swine with and without a continuous infusion of intravenous nitroglycerin (50 micrograms/min). Carbon dioxide had an immediate and profound depressant effect on both systolic and diastolic left ventricular function associated with ischemic electrocardiographic changes. Compared with controls (% change), ascending doses of carbon dioxide decreased systolic pressure by -35 +/- 7, -48 +/- 8, and -53 +/- 4 in the absence of nitroglycerin, and by -32 +/- 9, -50 +/- 9, and -60 +/- 9 in the presence of nitroglycerin. Peak+dP/dt decreased by -54 +/- 7, -61 +/- 11, and -64 +/- 3 in the absence of nitroglycerin, and by -36 +/- 13, -55 +/- 11, and -65 +/- 11 in the presence of nitroglycerin. Minimum -dP/dt increased by 65 +/- 8,71 +/- 8, and 77 +/- 3 in the absence of nitroglycerin, and by 63 +/- 7,71 +/- 8, and 78 +/- 7 in the presence of nitroglycerin. No significant changes in heart rate were observed; however, widespread ST-segment elevation was observed in all animals. Coronary angiography following carbon dioxide injection revealed a marked decrease in coronary flow velocity until the gas was cleared from the microcirculation. This was also documented by direct measurement of flow velocity using a Doppler catheter in an additional animal. Left ventriculography demonstrated immediate global dilation and depression of systolic function. In the swine model, relatively small doses of intracoronary carbon dioxide cause profound yet reversible global left ventricular dysfunction which appears to be ischemic in origin.

Importance of Adequate Gas-mixing in Contrast Echocardiography

Microbubble formation has been accepted as the mechanism producing contrast echoes. Comparisons of the contrast effects of various agents have been studied extensively, but the importance of gas-mixing has been less appreciated. To test the hypothesis that good gas-mixing, by facilitating microbubble formation, would enhance contrast effect, this study compared the contrast echocardiograms of ten adult patients before and after mixing carbon dioxide with various contrast agents. Contrast agents tested included a 5 percent glucose in water, vitamin B complex, vitamin C, and Cardiogreen solutions. First, we recorded echocardiograms by injecting each diluted contrast solution alone, then repeated the examinations using 10 ml of each diluted solution with 1 ml of carbon dioxide (CO2), mixed by means of a four-way stopcock. Satisfactory or excellent results were obtained in seven of ten, ten of ten, ten of ten, and ten of ten tests, respectively, after thorough gas-mixing, vs one of ten, seven of ten, eight of ten, and six of ten, respectively, before gas-mixing. We conclude that the addition of sufficient amounts of gas, followed by thorough mixing, is of great importance in contrast echocardiography. Consistently good results can be achieved with vitamin C, vitamin B or Cardiogreen solutions by this simple and safe method.

Response of two African simuliids to silhouettes and carbon dioxide.

Simulium adersi Pomeroy and a species close to S. impukane de Meillon were attracted to and landed on silhouettes at ground level when 100–200 ml of carbon dioxide per min. were released beside them. More flies landed on the lee and shady portions of the silhouettes than on the windward and sunny sides. No flies landed on the silhouettes without the carbon dioxide.

Carbon Dioxide Elimination from Circle Systems

Ten various circle systems were studied in model experiments. All the experiments were performed using a Waters cannister containing 675–685 g of Durasorbr̀. 300 ml of carbon dioxide were supplied to the system per min. The efficacy of these systems was expressed as the time taken to demonstrate a concentration of 0.6% carbon dioxide in the gas mixture supplied to the patient connection during each respiratory cycle. The carbon dioxide elimination was studied at a gas flow of 2, 4 and 6 1 per min. All the systems showed an effective carbon dioxide elimination for 6 h or more at a flow of 2 1. An increasing efficacy was found with increasing flow, but to a varying extent.A circle system where all the components, including the cannister and directional valves, can be replaced after use is recommended owing to the risk of cross contamination. A soda‐lime charge of 600–700 g is advantageous. For anesthetic procedures of less than 1 h, other techniques should be employed as they are more economical.

Gas consumption and growth rate of Hydrogenomonas eutropha in continuous culture.

The bacterium Hydrogenomonas eutropha is under consideration for use in a regenerative life-support system for manned space missions of long duration. A 4-liter continuous culture unit containing the organism was operated for a period of 272 days under autotrophic environmental conditions. The best steady-state run achieved with this unit was observed over a 22-day time interval after 181 days of operation. During this time, the culture consumed an average of 22.9 +/- 2.0 ml of carbon dioxide per min, 38.1 +/- 3.3 ml of oxygen per min, and 128.5 +/- 10.6 ml of hydrogen per min. It required 18.7 +/- 1.2 liters of fresh nutrient medium per 24 hr to maintain a constant, preestablished cell population of 1.65 g (dry weight) per liter. The ratio of consumption of carbon dioxide, oxygen, and hydrogen varied from 1:1.2:4.5 to 1:1.9:6.6, with an average of 1:1.7:5.7. Based on these values, approximately 60 liters of the culture would be necessary to balance the gas exchange of one man.

Gas Consumption and Growth Rate of Hydrogenomonas eutropha in Continuous Culture

The bacterium Hydrogenomonas eutropha is under consideration for use in a regenerative life-support system for manned space missions of long duration. A 4-liter continuous culture unit containing the organism was operated for a period of 272 days under autotrophic environmental conditions. The best steady-state run achieved with this unit was observed over a 22-day time interval after 181 days of operation. During this time, the culture consumed an average of 22.9 +/- 2.0 ml of carbon dioxide per min, 38.1 +/- 3.3 ml of oxygen per min, and 128.5 +/- 10.6 ml of hydrogen per min. It required 18.7 +/- 1.2 liters of fresh nutrient medium per 24 hr to maintain a constant, preestablished cell population of 1.65 g (dry weight) per liter. The ratio of consumption of carbon dioxide, oxygen, and hydrogen varied from 1:1.2:4.5 to 1:1.9:6.6, with an average of 1:1.7:5.7. Based on these values, approximately 60 liters of the culture would be necessary to balance the gas exchange of one man.