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PubMed2005

Physiologically precise simulation of multiple lung gas exchange during anaesthesia by simultaneous gas infusion and extraction.

UNLABELLED: A lung gas exchange simulator was tested which produces simultaneous uptake and/or elimination of multiple gases by an artificial test lung with physiologically realistic gas expired and exhaust gas flows, using a combination of infusion of diluting/enriching gases into the lung with lung gas extraction. A deterministic algorithm is incorporated which calculates required gas infusion and extraction flow rates for any set of possible target gas exchange values with any given set of fresh gas flows and concentrations. Six different scenarios were simulated, comprising a range of gas exchange values for each gas species which lie within a physiologically realistic range for anaesthetized patients. For each of these experiments the system was tested for 15 consecutive measurements over 25 min by measurement of gas exchange in the system using the Haldane transformation. RESULTS: the mean bias and standard error of the mean bias (SE, in parentheses) relative to the target value was: +0.001 (0.002) l min(-1) for O(2) uptake, -0.002 (0.005) l min(-1) for CO(2) production, -0.001 (0.002) l min(-1) for uptake of nitrous oxide and +0.3 (0.1) ml min(-1) for uptake of a volatile anaesthetic agent (isoflurane). The confidence limits of the mean bias were within 5% of the target value for all gases and scenarios with the exception of those where a low uptake of anaesthetic gas was specified. The confidence limits of the mean bias for the lower uptakes of isoflurane were within 10% of the target value for these scenarios and within 15% for the low uptake of N(2)O. Good accuracy and precision of this approach to lung gas exchange simulation were demonstrated, resulting in a versatile simulator.

Algorithms↗
PubMed1995

Effect of tracheal gas insufflation on gas exchange in canine oleic acid-induced lung injury.

OBJECTIVE: To determine the effect of tracheal gas insufflation on gas exchange in oleic acid-induced lung injury in dogs. DESIGN: Prospective, longitudinal study. SETTING: University research laboratory. SUBJECTS: Five mongrel dogs. INTERVENTIONS: The dogs were anesthetized, paralyzed, and mechanically ventilated. Lung injury was induced by infusing 0.09 mL/kg of oleic acid and pulmonary artery occlusion (wedge) pressure (PAOP) was increased to 15 mm Hg by infusing fluids to enhance pulmonary edema formation. After 60 mins, PAOP was allowed to decrease to 5 mm Hg and was maintained at 5 mm Hg for 60 mins to stabilize the pulmonary edema. We studied the effect of tracheal gas insufflation on gas exchange at low and high end-expiratory lung volumes achieved by a positive end-expiratory pressure of 5 and 12 cm H2O, respectively. The FIO2 values of the ventilator and catheter were equivalent (0.6). Each tracheal gas insufflation stage at low and high end-expiratory lung volume was preceded and followed by conventional mechanical ventilation stages without tracheal gas insufflation. During transitions between conventional mechanical ventilation and tracheal gas insufflation, end-expiratory lung volume was maintained constant by adjusting positive end-expiratory pressure while monitoring esophageal pressure and inductive plethysmography. Tidal volume was maintained constant throughout the protocol (0.40 L). MEASUREMENTS AND MAIN RESULTS. At end stage, we measured PaCO2, PaO2, total physiologic deadspace fraction, and venous admixture, which were 43 +/- 4 torr (5.7 +/- 0.5 kPa), 325 +/- 6 torr (43.3 +/- 0.8 kPa), 53 +/- 3%, and 4.0 +/- 0.3% before oleic acid lung injury, respectively. After oleic acid injury at low end-expiratory lung volume, these variables were 55 +/- 4 torr (7.3 +/- 0.5 kPa), 73 +/- 13 torr (9.7 +/- 1.7 kPa), 61 +/- 4%, and 50 +/- 7%, respectively. During tracheal gas insufflation at low end-expiratory lung volume conditions, PaCO2 and the total physiologic deadspace fraction decreased significantly (p < .05) to 45 +/- 4 torr (6.0 +/- 0.5 kPa) and 50 +/- 5%, respectively. Under high end-expiratory lung volume conditions, PaCO2 and the total physiologic deadspace fraction were 55 +/- 7 torr (7.3 +/- 0.9 kPa) and 61 +/- 6%, respectively; during tracheal gas insufflation, these variables decreased to 43 +/- 4 torr (5.7 +/- 0.5 kPa) and 52 +/- 5%, respectively (p < .05). Increasing end-expiratory lung volume improved both PaO2 and venous admixture (p < .05) but tracheal gas insufflation had no significant effect on oxygenation efficiency when end-expiratory lung volume was held constant. CONCLUSIONS: Tracheal gas insufflation augmented alveolar ventilation effectively in the setting of oleic acid-induced lung injury in dogs. When end-expiratory lung volume and tidal volume were kept constant, tracheal gas insufflation did not affect oxygenation.

Animals↗
PubMed2005

Technical pitfalls in middle ear gas studies: errors introduced by the gas permeability of tubing and additional dead space.

CONCLUSIONS: We demonstrated errors introduced by the gas permeability of the tubing and additional dead space. Materials with practically no permeability, such as glass, must be used to overcome the loss or gain of gas through the walls of tubes used for studying ME gas variations. Experiments conducted at a constant volume (variable pressure) require the smallest possible tubing volume in order to obtain good sensitivity and improve the accuracy of the results. OBJECTIVES: Experimental studies that investigate middle ear (ME) gas exchanges, using either pressure measurements or volume changes, are conducted using various tubing connections between the ME and a measuring device. The aims of this study were to highlight experimental problems due to the errors introduced by (i) the gas permeability of the tubing used and (ii) additional dead space in experiments conducted at constant volume. MATERIAL AND METHODS: The problem of the gas permeability of the tubing was addressed by comparing three types of tube (silicone, polyethylene, PVC) with a glass tube. Horizontally placed tubes were connected to a syringe filled with pure CO2 via a gas-tight valve. The end of each tube tested was plunged into colored water (5% Coomassie Brilliant Blue R-250). The tube was washed out with CO2 until gas bubbles were seen leaving it. The valve was then closed and the movement of water in the tube was observed. The same experiments were repeated for pure O2. The problem of the error introduced by the additional dead space volume was addressed at a theoretical level using the well-known gas laws. Two conditions were studied: condition A, in which the experiment was conducted at constant pressure and the volume was measured; and condition B, in which the experiment was conducted at constant volume and the pressure was measured. The main outcome measure of each condition was the calculated variation in the final number of moles of gas involved. RESULTS: No water movement was observed in glass tubes. In contrast, plastic tubes exhibited significant gas permeability effects for both CO2 and O2. The colored solution advanced at a faster rate with CO2 than O2 but differently for each type of tubing. For condition A, gas transfer was independent of the volume of the external tubing and was accurately measured by the displacement of the droplet in the lumen. In contrast, for condition B, the pressure variations were influenced by the volume of the tubing.

Acoustics↗
PubMed1995

The comparison of clinical course and results of treatment between gas-forming and non-gas-forming pyogenic liver abscess.

OBJECTIVES: To study and review the clinical manifestations, courses, and results of treatment in 83 cases of verified gas-forming pyogenic liver abscess. DESIGN: Case series. SETTING: Both primary and referral hospital care. PATIENTS: Four hundred twenty-four patients with clinical diagnosis of pyogenic liver abscess were enrolled in the study. Eighty-three patients had gas-forming abscesses and 341 had non-gas-forming abscesses. The clinical manifestations, duration of symptoms, incidence of septic shock, laboratory findings, concurrent diabetes mellitus, cause of abscess, size of abscess, and results of treatment were recorded. MAIN OUTCOME MEASURES: A chi 2 test for qualitative data and Student's test for quantitative data. RESULTS: Duration of symptoms were shorter (mean +/- SD, 5.2 +/- 5.3 vs 7.6 +/- 10 days) (P < .005) and the incidence of septic shock was higher in the gas-forming than in the non-gas-forming group (32.5% vs 11.7%) (P < .01). Laboratory findings revealed high levels of blood glucose, aspartate aminotransferase, alkaline phosphatase, and serum urea nitrogen in the gas-forming group. The size of abscess was usually bigger (> 5 cm) in this group. In the gas-forming group, 71 patients (85.5%) had diabetes mellitus and 65 patients (78.3%) had conditions of cryptogenic origin. Klebsiella pneumoniae was the main bacteria, in blood culture and liver aspirates, especially in gas-forming liver abscess. Medical treatment and/or aspiration carried a high mortality rate (44.4%) in the gas-forming group; also, the overall mortality rate was higher in this group than in the non-gas-forming group (27.7% vs 14.4%) (P < .01). CONCLUSIONS: The gas-forming liver abscess may be a disease of wide spectrum of severity and may run a fulminating course. Strong antibiotics with early adequate drainage are mandatory. Surgery should not be delayed if necessary.

Adult↗
PubMed1977

Effects of pulmonary gas embolism on circulation and respiration in the dog. III. Excretion of venous gas bubbles by the lung.

Intravenous injection of gas (10-60 ml) causes acute pulmonary embolism, which disappears completely within 10-20 min. Intravenous infusion of gas (1-5 ml min-1) can be continued for a long time. During these infusions a steady state is reached in which pulmonary arterial pressure is increased and cardiac output remains unaltered. This indicates that the degree of embolization has reached a constant level despite the continuous gas infusion. These findings can be explained by a gradual disappearance of the bubbles from the pulmonary circulation. The purpose of this study was to measure the possible excretion of gas from the intravascular gas bubbles into the alveolar air after venous administration. Neon was used as a test gas since its fractional concentration in ambient air is low (0.00018) and it can be detected by gas chromatography with sufficient accuracy. It could be demonstrated that after injection neon was present in the expiration gas. During the steady state of infusion the rate of excretion in the expiration gas appeared to be equal to the rate of infusion. Changes in the pulmonary arterial pressure curve were reflected in the neon wash-out curve. It may be concluded that during pulmonary gas embolism the administered gas is excreted into the alveolar air and that the excretion rate largely depends on the increased pulmonary arterial pressure due to the obstructing bubbles themselves.

Animals↗
PubMed1997

[Defective gas mixers, a cause of retro-pollution of medical gas distribution pipelines].

A defective Air/O2 mixer of a ventilator located downstream of the gas outlets of two pipelines is a potential cause of retropollution. Retropollution of O2 with Air or vice versa carries a risk of either a) a hypoxic gas mixture delivery during anaesthesia, including O2-N2O administration, when the O2 pipeline supplies Air instead of O2, or b) a hyperoxic gas mixture delivery in the intensive therapy unit for neonates during administration of a O2-Air mixture, when the Air pipeline supplies O2 instead of Air. A defective O2/N2O flowmeter-mixer of an anaesthesia machine, with N2O flow control by O2 through a differential pressure manometer, can cause retropollution of O2 supply pipeline with N2O or vice versa. The prerequisite for retropollution is the association of three events: build-up of a pressure difference between the two gas lines; defective or absent back-flow check value in the circuit of the gas at a lower pressure; one of the following defects: a) the pressure equilibrating valves of the mixer cannot amend the pressure difference and allow a gas reflow at the gas mixture outlet; b) leak in the diaphragm of a pressure equilibrating valve; c) defective bypass supply valve. The optimal means for the recognition of a pipeline contamination by another gas is the O2 analyzer, especially in anaesthetic areas where the presence of N2O and Air carries the risk of a hypoxic gas mixture delivery. The mixer or flowmeter-mixer responsible for retropollution can be recognized in plunging successively the various quick couplers underwater into a glass, while the others remain connected to their outlets and the mixer set at a O2 concentration of 50 vol% or the flowmeters set at a similar flow. In case of retropollution, the gas reflow produces bubbles. It is recommended: a) in anaesthetic areas to set the O2 pressure at about 0.2 bar above that of Air and the latter at a pressure of about 0.2 bar above that of N2O; b) in intensive therapy units for neonates, to set the Air pressure at about 0.2 bar above that of O2; c) in all areas to disconnect from the gas outlets the devices equipped with a mixer or a flowmeter-mixer when not in use.

Anesthesia, Inhalation↗
PubMed1996

The relation of passage of gas an abdominal bloating to colonic gas production.

OBJECTIVE: To determine the relation of gas passage and abdominal bloating to the production of gas in the colon. DESIGN: Randomized, double-blind, crossover study of gaseous symptoms during a 1-week period. SETTING: A Veterans Affairs medical center. PARTICIPANTS: 25 healthy medical center employees. INTERVENTION: Participants' diets were supplemented with either a placebo (10 g of lactulose, a nonabsorbable sugar), psyllium (a fermentable fiber), or methylcellulose (a nonfermentable fiber). MEASUREMENTS: All participants were polled for gaseous symptoms (including number of gas passages, impression of increased rectal gas, and abdominal bloating), and five were examined for breath hydrogen excretion. RESULTS: Participants passed gas 10 +/- 5.0 times per day (mean +/- SD) during the placebo period. A significant increase in gas passages (to 19 +/- 12 times per day) and a subjective impression of increased rectal gas were reported with lactulose but not with either of the two fiber preparations. Breath hydrogen excretion, an indicator of hydrogen production in the colon, did not increase after ingestion of either of the fibers. However, a statistically significant (P < 0.05) increase in feelings of abdominal bloating (which the participants perceived as excessive gas in the bowel) was reported with both fiber preparations and with lactulose. CONCLUSIONS: The physician should distinguish between excessive gas (which indicates excessive gas production) and feelings of bloating (which are usually unrelated to excessive gas production). Treatment of the former consists of limiting the supply of fermentable material to the colonic bacteria. Symptoms of bloating usually indicate the irritable bowel syndrome, and therapy should be directed accordingly.

Adult↗
PubMed1989

[Studies on the method of sterilization with ethylene oxide gas. 2. Residual EO gas on sterilized objects].

Ethylene oxide gas (EO gas) adsorbed onto sterilized objects was quantitated in an effort to take a safety measure against residual EO gas following its use in sterilization. We measured residual amounts of EO gas adsorbed onto laboratory wares, small medical tools and appliances just after post-sterilization airation to examine whether they were rendered entirely free from EO gas by the process. The results led us to arrive at the following conclusions: 1. EO gas was recognized to remain on sterilized objects even after allowing them to stand for about 16 hours following airation. 2. The amount of residual EO gas was smaller on metallic products and larger on rubber products (notably rubber gloves). An exceedingly high concentration of EO gas was noted to remain on a tooth-brush, among other plastic materials. These facts seem to indicate that the amount of residual EO gas is closely related to the texture and shape of materials to be sterilized. 3. As regards the potential toxicity of residual EO gas. However, their sensitivity was proved to be questionable, judgment on a result being subject to considerable individual variations. 4. Nevertheless, it is incontestable that these devices can at least provide a rough estimate of unavailing since monitoring by direct measurement of residual EO gas is virtually infeasible from a practical point of view.

Dental Instruments↗
PubMed1999

Hemodilution during venous gas embolization improves gas exchange, without altering V(A)/Q or pulmonary blood flow distributions.

BACKGROUND: Isovolemic anemia results in improved gas exchange in rabbits with normal lungs but in relatively poorer gas exchange in rabbits with whole-lung atelectasis. In the current study, the authors characterized the effects of hemodilution on gas exchange in a distinct model of diffuse lung injury: venous gas embolization. METHODS: Twelve anesthetized rabbits were mechanically ventilated at a fixed rate and volume. Gas embolization was induced by continuous infusion of nitrogen via an internal jugular venous catheter. Serial hemodilution was performed in six rabbits by simultaneous withdrawal of blood and infusion of an equal volume of 6% hetastarch; six rabbits were followed as controls over time. Measurements included hemodynamic parameters and blood gases, ventilation-perfusion (V(A)/Q) distribution (multiple inert gas elimination technique), pulmonary blood flow distribution (fluorescent microspheres), and expired nitric oxide (NO; chemoluminescence). RESULTS: Venous gas embolization resulted in a decrease in partial pressure of arterial oxygen (PaO2) and an increase in partial pressure of arterial carbon dioxide (PaCO2), with markedly abnormal overall V(A)/Q distribution and a predominance of high V(A)/Q areas. Pulmonary blood flow distribution was markedly left-skewed, with low-flow areas predominating. Hematocrit decreased from 30+/-1% to 11+/-1% (mean +/- SE) with hemodilution. The alveolar-arterial PO2 (A-aPO2) difference decreased from 375+/-61 mmHg at 30% hematocrit to 218+/-12.8 mmHg at 15% hematocrit, but increased again (301+/-33 mmHg) at 11% hematocrit. In contrast, the A-aPO2 difference increased over time in the control group (P < 0.05 between groups over time). Changes in PaO2 in both groups could be explained in large part by variations in intrapulmonary shunt and mixed venous oxygen saturation (SvO2); however, the improvement in gas exchange with hemodilution was not fully explained by significant changes in V(A)/Q or pulmonary blood flow distributions, as quantitated by the coefficient of variation (CV), fractal dimension, and spatial correlation of blood flow. Expired NO increased with with gas embolization but did not change significantly with time or hemodilution. CONCLUSIONS: Isovolemic hemodilution results in improved oxygen exchange in rabbits with lung injury induced by gas embolization. The mechanism for this improvement is not clear.

Animals↗
PubMed1983

Effects of gas density on pulmonary gas exchange of normal man at rest and during exercise.

Changes in the physical properties of inspired gas might be expected to influence the distribution of ventilation in the lungs as well as the diffusive and convective (cardiogenic) mixing of inspired gas with lung residual gas, thus possibly affecting pulmonary gas exchange for O2 and CO2. The purpose of our work was to assess to what extent this occurs in practise in human subjects, who could compensate for the changes directly brought about by altering the physical characteristics of the inhaled gas by changing their breathing pattern. Six healthy, non-smoking men breathed, at rest and during moderate exercise, gas mixtures containing 21% oxygen completed either by 79% nitrogen (air), helium (O2-He) or sulphur hexafluoride (O2-SF6). We observed that the inhalation of these three different gas mixtures whilst at rest did not affect arterial partial pressures of O2 or CO2, the physiological dead space to tidal volume ratio, or the alveolo-aADCO2). During exercise, AaDO2 was slightly (2-3 mm Hg) but significantly higher with both O2-He and O2-SF6 than with air. Although minute ventilation did not change, breathing frequency was slightly but significantly affected by the type of gas mixture breathed, being lower with O2-SF6 and higher with O2-He. We conclude that, within the range studied, the physical properties of the inhaled gas do not affect pulmonary gas exchange in healthy man, either because the changes affected are minimal or because they compensate for each other.

Adult↗
PubMed2003

Carrier gas as a new factor influencing the selectivity of the gas-stationary liquid phase chromatographic system.

This paper generalizes studies on the influence of carrier gas on relative and absolute retention values. This line of research is also of importance due to the fact that, in the opinion of many chromatographers, the role of the carrier gas is limited only to transporting analyzed compounds along the column. However, even under conditions of the conventional capillary gas-liquid chromatography (i.e. at column pressures under 5 atm) carrier gas (its nature and pressure) significantly influences retention and separation of the analyzed compounds. First, carrier gas (N2 and CO2, for example) dramatically affects relative retention values. For this reason, one should use limit values of alpha(ij) (0) = lim alpha(ij)(P(av)) and I(i)(0) = lim Ii(Pav) I(0) = limI(i) (Pav) with Pav-->0 as chromatographic constants, rather than traditional relative retention values alpha(ij)(P(av)) and I(i)(P(av)). Second, the average pressure Pav of the carrier gas in a column and the nature of the carrier gas influence the selectivity of the gas-stationary liquid phase chromatographic system. Third, wishing to maximize the role of the carrier gas as a factor that improves separation of analyzed compounds, we should design a special gas chromatograph that would allow work with pressures in the column up to 30-50 atm.

Chromatography, Gas↗
PubMed2004

A new method for measurement of gas exchange during anaesthesia using an extractable marker gas.

A new method for the measurement of pulmonary gas exchange during inhalational anaesthesia is described which measures fresh gas and exhaust gas flows using carbon dioxide as an extractable marker gas. The theoretical precision of the method was compared by Monte Carlo modelling with other approaches which use marker gas dilution. A system was constructed for automated measurement of uptake of oxygen, nitrous oxide, volatile anaesthetic agent and elimination of carbon dioxide by an anaesthetized patient. The accuracy and precision of the method was tested in vitro on a lung gas exchange simulator, by comparison with simultaneous measurements made using nitrogen as marker gas and the Haldane transformation. Good agreement was obtained for measurement of simulated uptake or elimination of all gases studied over a physiologically realistic range of values. Mean bias for oxygen and nitrous oxide uptake was 0.003 l min(-1), for isoflurane 0.0001 l min(-1) and for carbon dioxide 0.001 l min(-1). Limits of agreement lay within 10% of the mean uptake rate for nitrous oxide, within 5% for oxygen and isoflurane and within 1% for carbon dioxide. The extractable marker gas method allows accurate and continuous measurement of gas exchange in an anaesthetic breathing system with any inspired gas mixture.

Anesthesia, Inhalation↗
PubMed2004

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.

Administration, Inhalation↗
PubMed2006

Growth mechanism of a gas clathrate hydrate from a dilute aqueous gas solution: a molecular dynamics simulation of a three-phase system.

A molecular dynamics simulation of a three-phase system including a gas clathrate, liquid water, and a gas was carried out at 298 K and high pressure in order to investigate the growth mechanism of the clathrate from a dilute aqueous gas solution. The simulation indicated that the clathrate grew on interfaces between the clathrate and the liquid water, after transfer of the gas molecules from the gas phase to the interfaces. The results suggest a two-step process for growth: first, gas molecules are arranged at cage sites, and second, H(2)O molecules are ordered near the gas molecules. The results also suggest that only the H(2)O molecules, which are surrounded or sandwiched by the gas molecules, form the stable polygons that constitute the cages of the clathrate. In addition, the growth of the clathrate from a concentrated aqueous gas solution was also simulated, and the results suggested a growth mechanism in which many H(2)O and gas molecules correctively form the structure of the clathrate. The clathrate grown from the concentrated solution contained some empty cages, whereas the formation of empty cages was not observed during the growth from the dilute solution. The results obtained by both simulations are compared with the results of an experimental study, and the growth mechanism of the clathrate in a real system is discussed.

Journal Article↗
PubMed2005

Effect of corona discharge on the gas composition of the sample flow in a Gas Particle Partitioner.

A Gas Particle Partitioner (GPP) that allows highly efficient separation of gas and particles with no effect on the thermodynamic conditions and substantially no change of the gas composition has been developed. The GPP is a coaxial arrangement with inner and outer electrodes and utilizes a corona discharge to electrically charge the particles and a strong electric field to remove them from the sample flow. Several measures were taken to avoid an influence of the corona discharge on the gas composition. The GPP can be applied for various applications. This paper focuses on the use of the GPP as a pre-filter for gas analyzers, where zero pressure drop and a minimization of the influence of the corona discharge on the gas composition are the main objective. Due to its design, the GPP introduces no changes to the thermodynamic conditions. However, corona discharge is known to produce significant amounts of ozone and oxides of nitrogen. The effect of the corona on the gas composition of the sample flow was determined under various conditions. The gas concentrations strongly depended on several aspects, such as material and diameter of the corona wire and polarity of the corona voltage. Due to the measures taken to minimize an effect on the gas composition, the concentrations of these gases could effectively be reduced. Along with the maximum gas-particle separation efficiency of near 100%, the additional O3 concentration was 42 ppbV and the additional NO2 concentration 15 ppbV. If an efficiency of 95% is acceptable, the added concentrations can be as low as 2.5 ppbV (O3) and 0.5 ppbV (NO2), respectively.

Air Pollutants↗
PubMed2005

Group A streptococcus (GAS) carbohydrate as an immunogen for protection against GAS infection.

Previous studies have shown that human serum containing anti-group A streptococcus carbohydrate (GAS CHO) antibodies were opsonic for different M protein-carrying serotypes. To investigate the role that anti-GAS CHO antibodies play in passive and active protection, mice were immunized subcutaneously or intranasally with GAS CHO conjugated to tetanus toxoid, and mortality and oral colonization were monitored after challenge with live GAS. Compared with control mice, immunized mice were significantly protected against systemic or nasal challenge with GAS. Furthermore, studies of serum samples and throat cultures from Mexican children revealed an inverse relationship between high serum titers of anti-GAS CHO antibodies and the presence of GAS in the throat. Anti-GAS CHO antibodies were also tested for cross-reactivity with human tissues and cytoskeletal proteins. No cross-reactivity was observed in either assay. The present study demonstrates that GAS CHO is both immunogenic and protective against GAS infections.

Adolescent↗
PubMed1981

Gas flow measurements with a gas dilution technique.

A new method for gas flow measurements, based on a gas dilution technique, is described. A known amount of fresh room air is injected as a tracer gas into a carrier gas stream. The downstream concentration profile of the tracer gas is recorded with a portable mass-spectrometer. The flow rate of the carrier gas is calculated from the area under the tracer gas curve as electronically integrated. The method was tested against precision spirometers, one of the rolling seal type and one of the fluidistor type. It was shown that any rapid gas analyser might be used for the analyses, either of the tracer gas or of the carrier gas. The applicability of this method during general anaesthesia and in other clinical situations is discussed.

Anesthetics↗
PubMed1996

Evaluation of an on-demand, ex vivo bedside blood gas monitor on pulmonary artery blood gas determinations.

Critically ill patients often have cardiopulmonary perturbations that require rapid and frequent assessment for optimal care, including cardiac output determinations, measurement of cardiac filling pressures, and arterial and mixed venous blood gas determinations. We evaluated the performance of a rapid, on-demand bedside blood gas monitor to determine arterial and mixed venous blood gas values. The blood gas monitor uses fluorescent optode technology to directly measure Po2, Pco2, and pH. This measurement is accomplished by aspirating blood from the artery or vein into a sampling chamber where it interfaces with the fluorescent optode. After approximately 90 s of equilibration, the blood gas values are reported. Since the blood is drawn into the sampling chamber, it can be returned to the patient, thus eliminating the need for phlebotomy. We studied 15 critically ill patients requiring systemic and pulmonary arterial catheterization. Conventional blood gas analysis was performed simultaneously. The results obtained from the blood gas monitor were compared with those obtained via traditional blood gas analysis using Bland-Altman plots and examination of bias and precision. The results were well within the expected clinical variance. During the study period, there was no interference with patient care or adverse events related to the use of the monitoring system. In conclusion, the blood gas monitor can provide rapid, accurate determinations of arterial and mixed venous blood gases allowing optimal therapeutic interventions in critically ill patients.

Adult↗