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At least 163 records · Page 9Linked to original sources
PubMed1994

Humidity of anaesthetic gases with respect to low flow anaesthesia.

It has been demonstrated in an experimental study in swine using the scanning electron microscope that a rebreathing technique utilising minimal fresh gas flowrates significantly improves climatization of anaesthetic gases. Consequently, effects of various anaesthetic techniques on airway climate must be assessed, which covers the need for suitable measuring devices. Basic principles and methods of humidity measurement in flowing anaesthetic gases include gravimetric hygrometry, dew point hygrometry, wet-dry bulb psychrometry, mass spectrometry, spectroscopic hygrometry and electrical hygrometry. A custom-made apparatus for continuous measurement of humidity and temperature in the inspired and expired gas mixtures of a breathing circuit (separated by a valve system, integrated between the endotracheal tube and the Y-piece) is described. Comparative evaluation of this apparatus and the psychrometer was carried out. It could be demonstrated that the apparatus, measuring with capacitive humidity sensors, is more suitable for prolonged use under clinical conditions than the psychrometer. In the second part of the study, climatization of anaesthetic gases under clinical conditions was investigated using fresh gas flowrates of 0.6, 1.5, 3.0 and 6.0 l/min. In the inspiratory limb of the circuit an absolute humidity of 21.3 mg H2O/l and a temperature of 31.5 degrees C were obtained after 120 minutes of minimal flow. Humidity and temperature of inspired air obtained with fresh gas flowrates of 6.0 and 3.0 l/min were found to be inadequate for prolonged anaesthesia. Reducing the fresh gas flow to 1.5 l/min increases heat and moisture content in the respired gases, but conditions are still inadequate for prolonged anaesthesia. Sufficient moisture (> or 20 mg H2O/l) and temperature are obtained under minimal flow conditions after one hour.

Absorption↗
PubMedDate not supplied

[Occupational exposure to anesthetic gases at several hospitals].

We considered data of samples collected in the period 1994-2001 in 83 operating rooms of 13 different public and private hospitals in Veneto Region. The anaestetic gases more used in operating rooms were nitrous oxide, isoflurane and, more recently, sevflurane. The mostly polluted positions were those in proximity of anaesthesiologic devices; the gases average concentrations were low in all hospitals examined, although some operating rooms demonstrated concentrations of anasthetic gases exceeding limit values. Lastly, the professional figures had different exposure to the various anaesthetic gases.

Air Pollution, Indoor↗
PubMed2004

A local scavenging system to remove waste anesthetic gases during general anesthesia.

BACKGROUND: A local scavenging system was constructed and tested in both the operating room and the laboratory to remove the waste anesthetic gases so as to lower the exposure risk of the anesthetic personnel. METHODS: A local scavenging system was developed to suck away the waste anesthetic gases (e.g., N2O and sevoflurane) escaping from the mouth and nostrils of a patient. The local scavenging system used was composed of an inlet funnel (with a diameter of 20 cm), a flexible connecting tubing, a high efficiency particulate air (HEPA) filter and a vacuum pump. To help evaluate the performance of the local scavenging system, a tracer gas (SF6) of a fixed concentration (= 200 ppm) and flow rate (= 5 l/min) was introduced around the nostrils of the patient during anesthesia. The concentrations of the gases (SF6, N2O and SEV) drawn away by the scavenging system were then determined by an extractive Fourier transform infrared (FTIR) spectrometer and those spreading around the breathing zone of the anesthesiologist were obtained by the other FTIR. In the laboratory tests, the relationship between the scavenging efficiency and the inlet funnel position was obtained using the aforementioned SF6-FTIR techniques. RESULTS: With the application of this local scavenging system, during three surgical operations, the average personnel exposure concentrations of N2O and sevoflurane (SEV) as measured were 8.7 and 0.06 ppm, respectively. Both measured concentrations were lower than the TWA values recommended by the US-NIOSH for N2O (= 25 ppm) and SEV (= 2 ppm). Based on the tracer gas (SF6) results, it was found that the average scavenging efficiency was equal to 87%, which was lower than the laboratory testing results of 95%. The (scavenging) efficiency difference between the laboratory and on-site tests could be due to the movement and action of the anesthesiologist during anesthesia. To optimize the performance of the local scavenging device, the inlet (funnel) should be placed close to the breathing region (e.g., noses and mouth) of the patient in the front direction. CONCLUSIONS: The application of the local scavenging system was found to greatly reduce the concentrations of the waste anesthetic gases (e.g., N2O and SEV) to the levels lower than those recommended by the US-NIOSH. With this scavenging device, the exposure health risk of the anesthesiologists could be greatly reduced.

Adolescent↗
PubMed1989

Trace anesthetic gases during xenon arc photocoagulation for retinoblastoma.

In pediatric ocular examinations, administration of continuous-flow anesthetic gases containing nitrous oxide, halothane, and oxygen enables the physician to do safe, controlled, reproducible examinations. We did a study in which the levels of waste anesthetic gases were measured during xenon arc photocoagulation procedures used for retinoblastoma. Waste nitrous oxide and halothane gases measured during these procedures significantly exceeded the levels recommended by the National Institute of Safety and Health. These high levels are of particular importance because of the physician's proximity to the patient during the procedure. The high levels of waste gases may have immediate deleterious effects on the physician's functioning capacity and may also pose long-term health hazards for the physician and operating room personnel.

Air Pollutants, Occupational↗
PubMed1986

[Antibacterial and antifungal activity of isoflurane and common anesthetic gases].

An in vitro analysis was conducted to investigate the hypothetical antibacterial and antimycotic activity of the common anesthetic gases (halothane, enflurane, isoflurane, methoxyflurane) in view of the clinical absence of bronchopulmonary pathology after inhalation narcosis despite the many risk factors involved. For this purpose scalar dilutions of the four gases were prepared on cultures of Klebsiella pneumoniae and Candida albicans and the antibacterial action of the gases was tested in vitro. Even with the weaker concentrations used, halothane and methoxyflurane totally inhibited both microorganisms. Enflurane had less effect on Klebsiella p. and almost none on Candida. Isoflurane, a new halogen ether anesthetic was found to have an excellent inhibitory effect. In conclusion it is hypothesised that the anesthetic gases considered might have an in vivo antibacterial activity considering the experimental results obtained in vitro.

Anesthetics↗
PubMed1979

[On the problem of optimal warming and moistening of the inspired gases in controlled and assisted artificial ventilation (author's transl)].

The physiological significance of adequate temperature and humidity of respiratory gases and the problems of technical realization are demonstrated. Humidifying and warming of gases by the principle of bubbling through a heated waterbath are believed to be best. The problems with these techniques e.g. dependence of temperature and relative humidity of the gases delivered to the patient on respiratory minute volume, material of the tubing and room temperature are shown. A simple solution to these problems without the need of electrical heated tubing is offered. A new electronically controlled humidifier (H.R.P.-Humidifier 2000) with special developed tubing is presented. Optimal temperature and relative humidity of the respiratory gases is guaranteed by the high efficiency humidifier, and additional measurement and regulation of temperature close to the patients tracheal tube. The problem of increased amounts of condensed water in the tubing is solved by the H.R.P. special tracheal tube adapter with an automatic water exhaust. In addition the hygienic problems of artificial respiration can be solved optimally in combination with the complete H.R.P.-System 2000.

Electronics, Medical↗
PubMed2004

Occupational exposures to acid mists and gases and ulcerative lesions of the oral mucosa.

BACKGROUND: This study examines the hypothesis that acid mist or mixtures of acid mists and acid gases are associated with ulcerative lesions of the oral mucosa. METHODS: All 665 active male workers of a metal processing factory were the study population. Semi-quantitative measures of exposure were estimated from a job exposure matrix constructed with industrial hygienist scoring and job titles. Ulcerative lesions of the oral mucosa were identified with standardized clinical dental exams. RESULTS: Past exposure to acid mists were positively associated with ulcerative lesions of the oral mucosa but only among workers without lip sealing (age- and alcohol consumption-adjusted prevalence ratio (PR), PR(adjusted) = 3.40; 90% CI: 1.48-7.85). Also in this worker group, the mixture of acid mists and acid gases was associated with ulcerative lesions of the oral mucosa limited to exposure in the past (PR(adjusted) = 2.83; 90% CI: 1.12-7.17). CONCLUSIONS: There is a positive association between acid mist or mixtures of acid mists and acid gases and ulcerative lesions of the oral mucosa only in the absence of lip sealing. The evidence of a chronic rather than acute irritative process suggests a possible step on the etiology of oral malignancies, which needs investigation.

Adolescent↗
PubMed2005

Towards supramolecular fixation of NOX gases: encapsulated reagents for nitrosation.

The use of simple calix[4]arenes for chemical conversion of NO2/N2O4 gases is demonstrated in solution and in the solid state. Upon reacting with these gases, calixarenes 1 encapsulate nitrosonium (NO+) cations within their cavities with the formation of stable calixarene-NO+ complexes 2. These complexes act as encapsulated nitrosating reagents; cavity effects control their reactivity and selectivity. Complexes 2 were effectively used for nitrosation of secondary amides 5, including chiral derivatives. Unique size-shape selectivity was observed, allowing for exclusive nitrosation of less crowded N-Me amides 5 a-e (up to 95 % yields). Bulkier N-Alk (Alk>Me) substrates 5 did not react due to the hindered approach to the encapsulated NO+ reagents. Robust, silica gel based calixarene material 3 was prepared, which reversibly traps NO2/N2O4 with the formation of NO+-storing silica gel 4. With material 4, similar size-shape selectivity was observed for nitrosation. The N-Me-N-nitroso derivatives 6 d,e were obtained with approximately 30 % yields, while bulkier amides were nitrosated with much lower yields (<8 %). Enantiomerically pure encapsulating reagent 2 d was tested for nitrosation of racemic amide 5 t, showing modest but reproducible stereoselectivity and approximately 15 % ee. Given high affinity to NO+ species, which can be generated by a number of NOX gases, these supramolecular reagents and materials may be useful for NOX entrapment and separation in the environment and biomedical areas.

Amides↗
PubMed1993

Pressure changes in the eye due to an injection of inert gases: a theoretical model.

In the repair of retinal tears and detachments, the vitreous humor is often completely replaced with a temporary mixture of gases, one of which is not normally found in the bloodstream. The resulting bubble can then support the healing retina. There is diffusion of gases, however, from the bubble into the bloodstream and vice versa. This alters the intraocular pressure, with possible adverse consequences, as the intraocular pressure must be maintained within a certain range for the procedure to be successful. A simple model has been developed to predict the evolution of intraocular pressure over time, given a certain initial mixture of injected gases. This model could be useful in determining what mixture to use to support effectively and safely a healing retina.

Capillaries↗
PubMed1987

A numerical study of the nonsteady transport of gases in the pulmonary capillaries.

A mathematical model is formulated for simulating the unsteady transport of gases in the blood flowing through the pulmonary capillaries. The formulation takes into account the transport mechanisms of molecular diffusion, convection and facilitated diffusion of the species due to haemoglobin. A time dependent situation is created by allowing to vary suddenly the partial pressures of the gases either in the venous blood or in the alveolar air. A numerical technique is described to solve the resulting time-dependent system of nonlinear coupled partial differential equations with the physiologically relevant boundary, entrance and initial conditions. The time required by the gases to achieve equilibrium is computed. It is shown that the dissolved oxygen takes longest in reaching equilibration whereas the carbon dioxide is the fastest. The various physiologically relevant unsteady situations have been examined.

Capillaries↗
PubMed1989

The excretion of highly soluble gases by the lung in man.

The excretion (E) of inert gases by the lung depends on, among other things, their blood-gas partition coefficients (lambda). According to conventional gas exchange models, E should increase with increasing lambda. However, recent models that take into account the tidal character of breathing and the buffering capacity of lung tissue predict that E will show a minimum in the range of large lambda values (lambda greater than 10). Further, this local minimum should shift to larger lambda values in exercise conditions as compared to rest conditions. The aim of this study is to verify this predicted behaviour of E. The experiments were carried out with seven healthy subjects at rest and at three work loads (50 W, 100 W and 150 W) on a bicycle ergometer. The behaviour of E was determined from the results of a simultaneous washin of four tracer gases: ethyl acetate (lambda approximately 75), acetone (lambda approximately 330), ethanol (lambda approximately 2000) and acetic acid (lambda approximately 20000). The washin lasted 4 min, and E was calculated from E = 1 - PE-/PI, where PI and PE- are the partial pressures of the tracer gas in inspired and mixed expired gas determined from the recordings obtained during the last minute of washin. PI and PE- were measured with a mass spectrometer. Comparison of the E values of the four gases shows that at rest a minimum value for E is found for acetone. In exercise conditions, however, the smallest E value is found for the more soluble ethanol or acetic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1975

Diffusivity of various inert gases in rat skeletal muscle.

Krogh's diffusion constant (K) was determined for various inert gases in isolated rat abdominal muscle at 37 degrees C by measuring the amount of gas diffusing per unit time and partial pressure difference through a portion of the muscle of known surface area and thickness. The following mean values for K, in 10(-9) mmol-min-1-cm-1-torr-1, were obtained: C2H2, 42.2; N2O, 20.0; CHClF2, 18.8; H2, 1.67; He, 1.42; CH4, 1.27; SF6, 0.081. From Krogh's diffusion constant, the diffusion coefficient (D) was calculated using the solubility coefficient determined previously in the same preparation. The D values thus obtained were found to be about half the D values in water at 37 degrees C. Model calculations show that for gases with high lipid/water partition coefficient, D in tissues containing lipid is underestimated by this method. Graham's law (inverse proportionality between D and square root of molecular mass) was found to represent a useful approximation for these gases. A better correlation, however, was obtained between D and the molecular diameter.

Abdominal Muscles↗
PubMed1985

Series dead space for inert gases in healthy subjects.

In ten normal subjects, series dead space was determined for six intravenously infused inert gases (SF6, ethane, cyclopropane, fluothane, ether, acetone) from their expired and alveolar concentrations. The method for sampling alveolar gas was based on the criterion of identity of mean alveolar and expired gas exchange ratios. Inert gases were analysed chromatographically. Acetone, the most soluble gas, yielded the lowest dead space, the difference to the other gases being about 4.5%. This is probably due to the non-infinite value of the series dead space ventilation-perfusion ratio (VA/Q) which was estimated at about 2,000. The diffusivity, inversely related to the molecular weight, also played a role, the heaviest gas (fluothane) having a greater dead space than the lightest (ethane). The underestimation of the dead space from acetone is expected to be greater in subjects with low tidal volume and high bronchial blood flow, i. e. in some patients with respiratory disease.

Humans↗
PubMed1994

Standard gases used to calibrate anesthetic vapor analyzers: are they stable?

OBJECTIVE: Gas cylinders containing volatile anesthetic vapors often are used to calibrate anesthetic agent analyzers. Differences seen between manufacturers in device calibration may be the result of error in the preparation of these calibration standards or drift in their concentration. METHODS: We measured the stability of 29 calibration gases in 2-L aluminum cylinders over a 15-month period. We also measured the stability of 18 gases in 1-L aluminum mini bottles. RESULTS: We found an average change of less than 0.02 vol% in the concentration of volatile anesthetic vapors for the 2-L aluminum cylinders containing 1.0 vol%. The maximum change was 0.04 vol%. For the 2-L cylinders, the manufacturer's certified concentration was 0.03 to 0.09 vol% higher than the concentration we measured on receipt. For the mini bottles, we found an average change of less than 0.04 vol% during a 6-month period; the maximum change was 0.06 vol%. The maximum change in 12 months was 0.14 vol%. CONCLUSIONS: Our results indicate that calibration gases containing volatile anesthetic vapors appear to be stable when stored in suitable cylinders. Aluminum cylinders sealed with a stop-cock seem to be suitable. In contrast, mini bottles seem to be less stable, probably due to the sealing construction. The difference of up to 0.09 vol% between our measurement of vapor concentration and the manufacturer's certified concentration may result from adsorption on surfaces in the cylinders after preparation or may reflect differences in calibration technique.

Anesthetics↗
PubMed1990

Doppler measurements of fetal and uteroplacental circulations: relationship with umbilical venous blood gases measured at cordocentesis.

A pulsed Doppler study of the fetal and uteroplacental circulations was performed on 41 pregnant women with small-for-gestational-age and 10 women with appropriate-for-gestational-age fetuses at 19 to 37 weeks' gestation. Blood gases and pH, measured in umbilical venous samples obtained by cordocentesis within 1 hour of the Doppler studies, were correlated individually and as an "asphyxia" index, to the Doppler and ultrasonographic biometric measurements. Although there were significant correlations between the majority of the ultrasonographic biometric and Doppler measurements with the blood gas results, better correlations were found with the ratio of common carotid artery to descending thoracic aorta mean velocity and pulsatility index. The best predictor of asphyxia was an index comprising aortic mean velocity and the common carotid artery pulsatility index. When this index was abnormal, 89% of fetuses had an asphyxia index 1 SD above the mean and 60% 2 SDs above the mean. A normal index was always associated with normal blood gases. The indices representing the inverse relationship of impedance and velocity in the two major vessels that supply the brain and the abdominal viscera provide the best prediction of the fetal condition because they reflect the hemodynamic response to changes in the partial pressure of respiratory gases.

Aorta, Thoracic↗
PubMed2004

Water-soluble gases as partitioning tracers to investigate the pore volume-transmissivity correlation in a fracture.

Hydraulically equivalent fractures may show striking differences when a gas-migration experiment is performed because of the different correlations between transmissivity, pore volume and entry pressure. We numerically simulate gas migration between injection and extraction boreholes in a parallel plate fracture with a heterogeneous fault gouge, in a rough-walled fracture filled with homogeneous material, and in a rough-walled empty fracture. The parallel plate model and the empty model clearly show the existence of preferential paths; for high variance of the transmissivity field, gas flow takes place only in few discrete channels separated by water-saturated regions. In contrast, in the fracture filled with homogeneous fault gouge, the gas saturation is continuous and more uniformly distributed. It appears a fundamental issue to be able to discriminate in situ among conceptual models that can yield such a different gas-saturation distribution. As in practice, the saturation distribution cannot be directly observed, tracer experiments are performed to characterize a fracture. For these reasons, we simulate the transport of tracers, which are added to the gas phase as soon as quasi-steady saturation distribution and extraction rate are achieved, and we compare the breakthrough curves obtained assuming different models. Our numerical simulations suggest that discrimination among the models on the basis of single-tracer tests is unlikely. A better tool to investigate fracture properties is provided by a gas-tracer test, in which a cocktail of gases with different water solubility is employed. These gases behave as partitioning tracers and allow us to estimate the gas saturation in the fracture. Indeed, by comparison of the residence-time distributions of different gases, we are able to compute a streamline effective saturation, which is an excellent estimate of fracture saturation. In addition, the streamline effective saturation curve contains information that is useful to identify the conceptual model that more likely applies to the fracture.

Environmental Monitoring↗
PubMed2005

Comparative field study on precipitation, throughfall, stemflow, fog water, and atmospheric aerosol and gases at urban and rural sites in Japan.

Precipitation collected by a wet-only sampler (WP), precipitation collected by a filtering-type bulk sampler (BP), throughfall (TF), stemflow (SF), fog water (FW), and atmospheric aerosol and gases were collected at two sites with different site classifications: an urban site (Mt. Rokko) and a rural site (Mt. Awaga) to investigate canopy-atmosphere interactions and to study the chemistry of precipitation in forested areas located in different atmospheric conditions. Compared to those at the rural site, the monthly volume-weighted pH values at the urban site were not significantly (p>0.05) different for WP, higher (p<0.05) for BP, not significantly (p> 0.05) different for TF, lower (p<0.01) for SF, and lower (p<0.01) for FW. The order of mean pH values at the urban site was FW<SF<WP<TF<BP. In contrast, the order at the rural site was FW<SF<BP<WP<TF. Concentrations of chemical species at the urban site were higher than those at the rural site in all samples and all chemical species. In particular, higher NO(3)(-) concentrations at the urban site were observed in all samples. The amount of dry deposition on leaves at the urban site was approximately 1.17 times larger than that at the rural site. The monthly net TF (=TF-BP) in autumn seemed to be larger than that in summer; this trend was remarkable in K(+). The monthly NO(3)(-) deposition in the net TF was larger at the urban site than at other parameters and at the rural site. The concentrations of chemical species in aerosol and gases that were measured near the central part of Kobe City were ca. 3.4 times higher than those in the rural area. Mt. Rokko borders the central part of the city, which caused the concentrations at Mt. Rokko to be higher than those at Mt. Awaga. The deposition amounts at Mt. Rokko were larger than those at Mt. Awaga, which probably can be attributed to the higher concentrations of chemical species in atmospheric aerosol and gases.

Aerosols↗
PubMed2001

Sites and mechanisms for uptake of gases and vapors in the respiratory tract.

Inhalation is a common route by which individuals are exposed to toxicants. The air contains a multitude of gases and vapors that are brought into the respiratory tract with each breath. Depending upon the physical and chemical characteristics of the toxicant, the respiratory tract can be considered as a target organ in addition to a portal of entry. Sufficient information is not always available on the fate or effects of an inhaled gas or vapor. Two physiochemical principles, water solubility and reactivity, can be used to predict the site of uptake of gases and vapors in the respiratory tract and potential mechanisms for reaction with respiratory tract tissue and absorption into the blood. Four model compounds, formaldehyde, ozone, dibasic esters, and butadiene are discussed as examples of how knowledge of aqueous solubility and chemical reactivity can help toxicologists predict sites and mechanisms by which inhaled gases and vapors interact with respiratory tract tissues.

Absorption↗