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PubMed1997

Vesicle-Specific Noble Gas Analyses of "Popping Rock": Implications for Primordial Noble Gases in Earth

Gases trapped in individual vesicles in the volatile-rich basaltic glass "popping rock" were found to have the same carbon dioxide, helium-4, and argon-40 composition, but a variable 40Ar/36Ar ratio ( approximately 4000 to >/=40,000). The argon-36 is probably surface-adsorbed atmospheric argon; any mantle argon-36 trapped in the vesicles cannot be distinguished from an atmospheric contaminant. Consequently the 40Ar/36Ar ratios and 3He/36Ar ratios (1.45) determined are minimum estimates of the upper mantle composition. Heavy noble gas relative abundances in the mantle resemble solar noble gas abundance patterns, and a solar origin may be common to all primordial mantle noble gases.

Journal Article↗
PubMed1997

Emission of Climate-Relevant Trace Gases and Succession of Microbial Communities during Open-Windrow Composting.

Determination of different indicators of microbial biomass, community structure, and bioactivity by the fumigation extraction method, as well as determination of phospholipid fatty acids (PLFAs) and their subfractions and the measurement of trace gases, respectively, provides valuable information about microbial succession in composting processes. The emission rates of carbon dioxide (CO(inf2)), methane (CH(inf4)), and nitrous oxide (N(inf2)O) increased successively during compost maturation: initially in the presence of easily degradable nutrients, during high temperature, and after the temperature had cooled down, respectively. The emission rate patterns of these trace gases corresponded to the concentrations of PLFAs and their particular subfractions. (i) Similar to the CO(inf2) emission rates, microbial biomass estimations by fumigation extraction and by determination of the amount of total PLFAs showed a discontinuous decrease during the composting process, with a slight increase at the end of the observation period. (ii) An increase in ether lipids, indicating the enhanced presence of archaean methanogens, and an elevated CH(inf4) emission were observed at the same time. (iii) The period of enhanced N(inf2)O emission corresponded to the increase in beta and omega hydroxy fatty acids derived from the outer membrane. Additionally, the continuous increase in branched-chain fatty acids suggested an increase in gram-positive bacteria and actinomycetes, and the decrease in polyunsaturated fatty acids indicated a decrease in eukaryotic cells during the composting.

Journal Article↗
PubMed1985

Spontaneous abortions and malformations in the offspring of nurses exposed to anaesthetic gases, cytostatic drugs, and other potential hazards in hospitals, based on registered information of outcome.

Nurses working in selected departments of general hospitals in Finland were collected from a central register on health personnel in Finland. Using the Hospital Discharge Register and the Register of Congenital Malformations, case nurses were selected who had had a spontaneous abortion (N = 217) or a malformed child (N = 46) between the years 1973 and 1979. Controls consisted of three nurses who had had a normal birth; the control nurses were matched for age and hospital of employment. Information on exposure in the first trimester of pregnancy was sought through the head nurses of the hospitals. No significant increase in risk of spontaneous abortion or of malformation was observed after exposure to anaesthetic gases (odds ratio for spontaneous abortion 1.2), sterilising gases and soaps, or x-rays. Handling of cytostatic drugs did not affect the frequency of spontaneous abortion but was associated with malformations in the offspring. The odds ratio, based on eight cases, was 4.7 (p = 0.02) when the logistic model was adopted. The results suggest that the exposures investigated, other than cytostatic drugs, do not cause a strong reproductive risk. Further studies are needed, particularly on cytostatic drugs.

Abnormalities, Drug-Induced↗
PubMed1990

Health effects associated with exposure to anaesthetic gases in Ontario hospital personnel.

In a retrospective study (by questionnaire) of 8032 personnel exposed to anaesthetic gases in operating and recovery rooms in Ontario hospitals, and 2525 non-exposed hospital staff, the response was 78.8% for the exposed and 87.2% for the unexposed personnel during the period 1981-5. Logistic regression analysis, with age and smoking standardised, showed that women in the exposed group had significantly increased frequencies of spontaneous abortion and their children had significantly more congenital abnormalities (p less than 0.05). No chronic disease was significantly associated with the exposed group. These findings, together with similar ones from other studies, suggest that it is prudent to minimise exposure to waste anaesthetic gases.

Abortion, Habitual↗
PubMed1989

Effect of acute, multiple-dose ethanol on maternal and fetal blood gases and acid-base balance in the near-term pregnant ewe.

The effect of ethanol on maternal and fetal blood gases and acid-base balance was determined in six conscious instrumented near-term pregnant ewes for maternal intravenous infusion of 3 g ethanol/kg total body weight administered as six doses of 0.5 g ethanol/kg total body weight over 8 h. Maternal and fetal blood ethanol concentrations, determined in two animals, were maximal at 8 h (3.74 and 3.82 mg/mL, respectively) and were virtually identical during the 24-h study. Maternal and fetal blood gases and acid-base balance were not significantly altered during and after ethanol administration compared with preinfusion values. The data demonstrate that, during near-term ovine pregnancy, the equivalent of a binge-type drinking episode does not produce fetal hypoxia or acidosis. Furthermore, these data do not support the postulated involvement of ethanol-induced fetal hypoxia in the mechanism of ethanol teratogenesis.

Acid-Base Equilibrium↗
PubMed2006

Connecting chemical dynamics in gases and liquids.

Modern ultrafast spectroscopic techniques provide new opportunities to study chemical reaction dynamics in liquids and hold the possibility of obtaining much of the same detailed information available in gases. Vibrational energy transfer studies are the most advanced of the investigations and demonstrate that it is possible to observe state-specific pathways of energy flow within a vibrationally excited molecule (intramolecular vibrational relaxation) and into the surrounding solvent molecules (intermolecular energy transfer). Energy transfer in liquids and gases share many common aspects, but the presence of the solvent also alters the relaxation in both obvious and subtle ways. Photodissociation is amenable to similarly detailed study in liquids, and there are informative new measurements. Bimolecular reactions have received the least attention in state-resolved measurements in liquids, but the means to carry them much further now exist. Studying photodissociation and bimolecular reaction of molecules prepared with initial vibrational excitation in liquids is a realistic, but challenging, goal.

Journal Article↗
PubMed1990

Transport of inert gases in mammalian myocardium: comparison with a convection-diffusion model.

Because tracer techniques are gaining an increasing importance for imaging flow (and metabolism) in the heart, experimental evidence is needed on the role of convection and diffusion in the transcoronary transport of solutes. In the present work, the transport of four different inert gases through the coronary system is studied in five closed-chest dog experiments and is compared with a digital multicapillary convection-diffusion model. Transport may be defined as flow dependent, as judged by the gross similarity of shape of the time-normalized dilution curves. However, the results show that the transcoronary transport of helium and xenon is more dispersed than that of argon and krypton, probably because of differences in diffusibility and solubility. A comparison of the animal and model experiments emphasizes the importance of diffusive transport of the gases. It is suggested that there is a diffusion shunt that is mainly located within the capillary network itself rather than between conduit vessels. Only for helium (which has the highest diffusivity) was a small arteriovenous shunt fraction seen that is thought to bypass the capillary exchange region. The conclusion is that although there is evidence of diffusional shunting at a capillary level, the inert gas kinetics in the heart are compatible with a basically flow-limited transport.

Animals↗
PubMed1992

Fetal cardiac bypass alters regional blood flows, arterial blood gases, and hemodynamics in sheep.

Successful fetal cardiac bypass might allow prenatal correction of some congenital heart defects. However, previous studies have shown that fetal cardiac bypass may result in impaired fetal gas exchange after bypass. To investigate the etiology of this impairment, we determined whether fetal cardiac bypass causes a redistribution of fetal regional blood flows and, if so, whether a vasodilator (sodium nitroprusside) can prevent this redistribution. We also determined the effects of fetal cardiac bypass with and without nitroprusside on fetal arterial blood gases and hemodynamics. Eighteen fetal sheep were studied in utero under general anesthesia. Seven fetuses underwent bypass without nitroprusside, six underwent bypass with nitroprusside, and five were no-bypass controls. Blood flows were determined using radionuclide-labeled microspheres. After bypass without nitroprusside, placental blood flow decreased by 25-60%, whereas cardiac output increased by 15-25%. Flow to all other fetal organs increased or remained unchanged. Decreased placental blood flow after bypass was accompanied by a fall in PO2 and a rise in PCO2. Nitroprusside improved placental blood flow, cardiac output, and arterial blood gases after bypass. Thus fetal cardiac bypass causes a redistribution of regional blood flow away from the placenta and toward the other fetal organs. Nitroprusside partially prevents this redistribution. Methods of improving placental blood flow in the postbypass period may prove critical to the success of fetal cardiac bypass.

Animals↗
PubMed1992

Prolonged stable hypothermia: effect on blood gases and pH in rats and ground squirrels.

Richardson's ground squirrels [body temperature (Tb) 7 degrees C] survive prolonged stable hypothermia for three times as long as do rats (Tb 19 degrees C) (72 vs. 24 h). We have examined the changes in blood gases and acid-base state to assess whether these contribute to this difference in survival time. None of the variables (measured at ambient temperature of 25 degrees C) differed significantly between rats and ground squirrels before hypothermic induction. During cooling, neither hematocrit nor plasma lactate changed significantly, but arterial and venous PO2 and PCO2 increased and arterial and venous pH decreased in both groups. During prolonged hypothermia, hematocrit increased significantly in rats (58.8 +/- 1.7% at 24 h) but not in ground squirrels (39.1 +/- 1.0% at 72 h). Both species maintained stable arterial blood gases but showed decreased venous PO2; arterial and venous pH decreased significantly with time in both species in conjunction with increased plasma lactate. These patterns of decreased venous PO2 and increased plasma lactate suggest that reduced tissue oxygenation occurs during hypothermia. This happens earlier in rats at a Tb of 19 degrees C than in ground squirrels at a Tb of 7 degrees C, possibly as a result of increased hematocrit in hypothermic rats. Remedial measures directed at improving tissue O2 delivery may therefore prolong the hypothermic survival of rats.

Animals↗
PubMed1985

Longitudinal dispersion of gases measured in a model of the bronchial airways.

We investigated the longitudinal dispersion of helium (He), methane, acetylene, butane, sulfur hexafluoride, and octafluorocyclobutane (C4F8) in a clear plastic model of the human bronchial airways. The dimensions of the seven airway generations (0-6) of the model were chosen to be equal to those given by Weibel's model A (Morphometry of the Human Lung; New York: Academic, 1963). Total volume of the model amounts to 52 ml. A small bolus of each of the tracer gases was injected within 1 ms into a constant airflow at the inlet of the model, and the bolus dispersion curve was measured at the outlet by means of a mass spectrometer. Both inspirations and expirations were simulated; the four selected values of the flow rate (V) for each simulation were 0.25, 0.5, 1, and 2 1/s, respectively. The measured bolus dispersion curves were corrected for the response characteristics of the mass spectrometer. In this way, the basal shape of the dispersion curve could be shown to be Gaussian. No significant changes in the standard deviation (sigma v) (Ultman et al., J. Appl. Physiol. 44: 297-303, 1978) of each tracer gas are found for the V values applied. sigma v increases significantly (approximately 50%), however, between the lightest (He) and the heaviest (C4F8) tracer gas used. The mean sigma v values of the 24 results (4 V values and 6 tracer gases) obtained for inspirations and expirations are 15.3 and 13.6 ml, respectively.

Acetylene↗
PubMed1986

Effects of subanesthetic doses of inert gases on behavioral thermoregulation in mice.

Mice exposed to subanesthetic partial pressures of N2O (0.25 to 0.75 atm) or N2 (5.7 or 11.33 atm) and allowed to choose between a warm and a cool environment showed a marked preference for the cooler environment. This behavior was associated with the onset of hypothermia, with deep body temperature falling by up to about 3 degrees C, usually to a new, steady level. Both the length of time spent in the cooler environment and the degree of the hypothermia produced increased with the partial pressure of N2O or N2 used. The effects of N2O on behavioral thermoregulation and body temperature were reversible. There was a correlation between anesthetic potency and the ability of both gases to alter thermoregulation, suggesting that the effect of these agents on thermoregulation was caused by the same molecular interactions as those which underlie anesthesia. Since both gases elicited changes in behavioral thermoregulation promoting rather than opposing the onset of hypothermia, it is concluded that they may have acted to lower the level at which deep body temperature was being regulated.

Anesthetics↗
PubMed1988

Breath holding during intense exercise: arterial blood gases, pH, and lactate.

Seven healthy endurance-trained [maximal O2 uptake (VO2max) = 57.1 +/- 4.1 ml.kg-1.min-1)] female volunteers (mean age 24.4 +/- 3.6 yr) served as subjects in an experiment measuring arterial blood gases, acid-base status, and lactate changes while breath holding (BH) during intense intermittent exercise. By the use of a counterbalance design, each subject repeated five intervals of a 15-s on:30-s off treadmill run at 125% VO2max while BH and while breathing freely (NBH). Arterial blood for pH, PO2, PCO2, O2 saturation (SO2) HCO3, and lactate was sampled from a radial arterial catheter at the end of each work and rest interval and throughout recovery, and the results were analyzed using repeated-measures analysis of variance. Significant reductions in pHa (delta mean = 0.07, P less than 0.01), arterial PO2 (delta mean = 24.2 Torr, P less than 0.01), and O2 saturation (delta mean = 4.6%, P less than 0.01) and elevations in arterial PCO2 (delta mean = 8.2 Torr, P less than 0.01) and arterial HCO3 (delta mean = 1.3 meq/l, P = 0.05) were found at the end of each exercise interval in the BH condition. All of the observed changes in arterial blood gases and acid-base status induced by BH were reversed during the rest intervals. During recovery, significantly (P less than 0.025) greater levels of arterial lactate were found in the BH condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis, Respiratory↗
PubMed1989

Lung weight in vivo measured with computed tomography and rebreathing of soluble gases.

In nine anesthetized dogs, accuracy of noninvasive measurements of lung weight (W) and gas volume in vivo was determined from volume and density determined by computed tomography (CT) and by rebreathing helium and the soluble gases dimethyl ether (WDME) and acetylene (WC2H2). Reference standards were obtained from the postmortem scale weight of the frozen lungs (Wscale) and compared with the CT lung weights measured in the living dog (WCT-38) and the frozen carcass (WCT-cold). WCT-cold did not significantly differ from Wscale [-2 +/- 9% (SD), P = 0.7]. WCT-cold was 10% greater than WCT-38 (0.10 greater than P greater than 0.05), suggesting an increase in lung weight despite immediately commencing freezing after death. WDME measured 64 +/- 6% and WC2H2 56 +/- 12% of WCT-38. Serial multiple measurements in three dogs over 14 wk showed a coefficient of variation (CV) of 10 +/- 2% for WDME, 18 +/- 2% for WC2H2, 4.1 +/- 0.9% for WCT, 2.6 +/- 0.8% for CT density, and 3.5 +/- 1.6% for functional residual capacity (FRC) by CT. FRC calculated from CT consistently underestimated FRC measured by rebreathing helium by 18 +/- 8% (P less than 0.005). This error, despite good agreement between WCT and Wscale, was explained by underestimation of CT total lung volume and overestimation of lung density by factors known to affect CT readings, such as partial volume effects, beam hardening, and limited number of input signals. These data show that CT scanning can provide serial measurement of the mass, density, and volume of the lungs with a CV in the order of 5%, but the rebreathing of soluble gases gives more than double this variability. Measurements of WDME performed on the same day had a CV of 3 +/- 1%, so that WDME provides a precise noninvasive means to measure lung weight in acute studies.

Acetylene↗
PubMed2006

[Arterial blood gases study in patients with stable chronic obstructive pulmonary disease in accordance with spirometric values].

BACKGROUND AND OBJECTIVE: The aim of this study was to evaluate the need to assess arterial blood gases in patients with stable chronic obstructive pulmonary disease (COPD) in accordance with spirometric values. PATIENTS AND METHOD: Transverse study in stable COPD patients with spirometry and pulse oximetry assessment. Specific exclusion criteria were: diagnosis of asthma, sleep apnea syndrome or respiratory failure not due to COPD. Diagnostic of respiratory failure was established when pulse oximetry saturation was < or = 92%; we evaluated the best predicted FEV1 cut-off value. RESULTS: 467 patients (age = 64 [8] yr) were evaluated. FEV1 was 44 (14) % predicted. Two patients (1.5%) with FEV1 > 50 % and 29 patients (23.6%) with FEV1 between 41 and 50% had respiratory failure. Sensitivity (0.98) and rate of false-negative (0.98) at a cut-off of 50% predicted value FEV1 was superior to sensitivity (0.75%) and rate of false-negative (0.87) at a cut-off of 40% predicted value FEV1. CONCLUSIONS: In stable COPD patients, the rate of respiratory failure increases when the predicted value FEV1 is below 50%. Therefore, we recommend this spirometric cut-off to evaluate arterial blood gases.

Aged↗
PubMed1999

Effect of hyperoxia and hypoxia on subcutaneous tissue gases and pH. An experimental study in pigs.

The effect of different fractions of inspired oxygen on subcutaneous oxygen tension, carbon dioxide tension and pH in relation to arterial and mixed venous blood gases and pH and hemodynamic variables was evaluated in 13 domestic pigs. Subcutaneous, arterial and mixed venous oxygen tensions were closely correlated (r = 0.94). A minor significant increase in subcutaneous carbon dioxide tension was noted during hyperoxia (p < 0.05). A major increase (33%) was noted during the last step of hypoxia, when arterial and mixed venous carbon dioxide tensions increased only 12 and 17%, respectively. A minor decrease in subcutaneous pH was noted during hyperoxia (p < 0.05) and a major decrease during hypoxia (p < 0.05). Measurements of subcutaneous tissue gases and pH are indicators of oxygen utilization during hyper- and hypoxia.

Animals↗
PubMed1987

Gas exchange during constant flow ventilation with different gases.

To investigate the mechanisms of CO2 transport during constant flow ventilation, we measured arterial blood gases using air, 80% He-20% O2 (He) or 80% SF6-20% O2 (SF6) as the insufflating gas. At any given flow rate (0.2 to 1.0 L/s), PaCO2 was greatest with He and lowest with SF6. Data for all gases could be described by the equation PaCO2/Pb = 0.044 V-0.64 v0.23, where Pb = barometric pressure, PaCO2 is in mm Hg, V = insufflated flow in L/s, and v = kinematic viscosity (cm2/s). At any given flow rate, the AaPO2 was greater using SF6 than using He. These results are consistent with a 2-zone model of gas transport in which the enhancement of gas transport as V increases may be due to an increase in the turbulent diffusivity in zone I (the region affected by the jet). The decreased gas transport with He compared to air and SF6 at any V may be due to either the decreased penetration depth of zone I caused by the greater kinematic viscosity of He, or the decreased rate of gas transport in the region affected by cardiogenic oscillations (zone II) secondary to the higher molecular diffusivity of He.

Animals↗
PubMed1988

Weekly cuirass ventilation improves blood gases and inspiratory muscle strength in patients with chronic air-flow limitation and hypercarbia.

We studied the effects of an 8-h, once-a-week schedule of cuirass ventilation (CV) in 5 patients with advanced chronic air-flow limitation and chronic hypercarbia (PaCO2, 58.6 +/- 10.1 mm Hg; mean +/- SD). Repeated measurements of arterial blood gases, maximal inspiratory mouth pressure (P1max), 12-min walking distance, and respiratory cycle were performed during a 1-month run-in period. Quality of life and transdiaphragmatic pressure were measured once. All patients completed the planned 4-month study. Four of them were ventilated for longer periods because CV could not be discontinued at the end of the study. PaCO2 showed a significant fall starting during the first month; PaO2 significantly increased from the second month, whereas P1max significantly rose from the third month on. Maximal transdiaphragmatic pressure increased in the 2 patients with abnormal baseline values. The fall in PaCO2 was associated with an increase in tidal volume because of a longer inspiratory time. Significant improvements in quality of life and in the 12-min walking distance were observed. We conclude that weekly CV improves blood gases, inspiratory muscle strength, and clinical conditions of patients with chronic air-flow limitation and chronic hypercarbia, probably because of correction of chronic inspiratory muscle fatigue.

Blood Gas Analysis↗
PubMed2001

Spontaneous fluctuations in the concentrations of oral sulfur-containing gases.

Breath hydrogen sulfide (H2S) and methyl-mercaptan (CH3SH) concentrations are used as quantitative indicators of halitosis. However, measurements of these gases in duplicate oral samplings often show poor reproducibility. To determine if this poor reproducibility is an artifact of the collection/analytical procedure or a true biological phenomenon, we used a standardized technique to collect from 20 to 30 oral gas samples at two-minute intervals from 11 healthy subjects. The samples were analyzed for sulfur gases and CO2. Sizable variations in H2S and CH3SH concentrations were not associated with alterations in CO2, indicating that the variations did not reflect variable contamination with atmospheric or pulmonary gas. In addition, fluctuations in H2S and CH3SH were not identical and often were not random. We conclude that minute-to-minute variability in oral sulfur gas concentrations is a true biological phenomenon. This fluctuation complicates experimental studies designed to show that interventions alter halitosis.

Adult↗