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At least 235 records · Page 13Linked to original sources
PubMed1986

Rapid mechanical ventilation effects on tracheal airway pressure, lung volume, and blood gases of rabbits.

The purpose of this study was to demonstrate that ventilation of rabbit lungs (whose mechanics are similar to those of human infants) at rapid rates will lead to large alterations in tracheal airway pressures, tidal volume, and functional residual capacity (FRC) with only minor changes in arterial blood gases. Thirteen rabbits were ventilated at rates of 30, 60, 90, and 120 breaths per minutes (BPM) with pressures of 17/2 cm H2O. Tracheal peak inspiratory pressure (PIP) was always lower than ventilator PIP and decreased to 11 +/- 1 cm H2O at 120 BPM. Positive end-expiratory pressure (PEEP) in the trachea was always greater than 2 cm H2O and increased with rate (3.5 cm H2O at 120 BPM). Tidal volume decreased as rates were increased such that rates above 60 BPM resulted in insignificant changes in minute ventilation and arterial blood gases. However, the FRC increased from 16 (30 BPM) to 25 ml/kg (120 BPM), a 56% increase, suggesting large increases in end-expiratory alveolar pressure. We conclude that rapid-rate ventilation (greater than 60 BPM) of healthy rabbits results in significant increases in both tracheal PEEP and FRC without significantly affecting arterial blood gases. The increased tracheal PEEP and FRC are manifestations of inadvertent PEEP. The increased FRC without concomitant increase in PaO2 implicates alveolar overdistention. We speculate that rapid-rate ventilation of human infants having lung mechanics similar to rabbits, will also result in inadvertent PEEP and alveolar overdistention.

Animals↗
PubMed2004

Vibrational energy relaxation of naphthalene in the S(1) state in various gases.

Time-resolved fluorescence spectra of naphthalene in the S(1) state have been measured in various gases below 10(2) kPa. The band shape of the fluorescence changed in an earlier time region after the photoexcitation when an excess energy (3300 cm(-1)) above the 0-0 transition energy was given. The excitation energy dependence of the fluorescence band shape of an isolated naphthalene molecule was measured separately, and the time dependence of the fluorescence band shape in gases was found to be due to the vibrational energy relaxation in the S(1) state. We have succeeded in determining the transient excess vibrational energy by comparing the time-resolved fluorescence band shape with the excitation energy dependence of the fluorescence band shape. The excess vibrational energy decayed almost exponentially. From the slope of the decay rate against the buffer gas pressure, we have determined the collisional decay rate of the excess vibrational energy in various gases. The dependence of the vibrational energy relaxation rate on the buffer gas species was similar to the case of azulene. The comparisons with the results in the low temperature argon and the energy relaxation rate in the S(0) state in nitrogen were also discussed.

Journal Article↗
PubMed2004

Health hazards from volcanic gases: a systematic literature review.

Millions of people are potentially exposed to volcanic gases worldwide, and exposures may differ from those in anthropogenic air pollution. A systematic literature review found few primary studies relating to health hazards of volcanic gases. SO2 and acid aerosols from eruptions and degassing events were associated with respiratory morbidity and mortality but not childhood asthma prevalence or lung function decrements. Accumulations of H2S and CO2 from volcanic and geothermal sources have caused fatalities from asphyxiation. Chronic exposure to H2S in geothermal areas was associated with increases in nervous system and respiratory diseases. Some impacts were on a large scale, affecting several countries (e.g., Laki fissure eruption in Iceland in 1783-4). No studies on health effects of volcanic releases of halogen gases or metal vapors were located. More high quality collaborative studies involving volcanologists and epidemiologists are recommended.

Acid Rain↗
PubMed1992

The use of tracer gases to determine dust dispersion patterns and ventilation parameters in a mineral processing plant.

A study was conducted in a fluorspar milling plant to assess the effectiveness of tracer gases as a reliable supplement to conventional air-monitoring and ventilation measurements. In the course of this study, a tracer gas was used as a surrogate substance to analyze the direction and the rate of spread of contaminants from various potential dust production points in the plant. Time-weighted average and continuous mineral dust concentrations were measured in several areas of the plant; these results were compared and correlated with steady-state tracer gas concentrations in the mill. Time-weighted average dust concentrations varied between 0.18 and 0.57 mg/m3 for total dust and 0.04 and 0.20 mg/m3 for quartz respirable dust, depending on the location. Correlation of these values with steady-state tracer gas concentrations yielded linear relationships with correlation coefficients (R2) of 0.95 and 0.87, respectively, for total and quartz dust. Results from this study, therefore, indicate that tracer gases may help model the spread of airborne respirable dust from point sources. These tracer gas releases also allowed the simultaneous quantitative determination of air residence times and contaminant clearance times from the building. Hence, tracer gases will help industrial hygienists obtain useful data with respect to building ventilation.

Air Pollutants, Occupational↗
PubMed2006

Evaluation of genetic damage in operating room personnel exposed to anaesthetic gases.

Information on potential genetic damage in humans after exposure to waste anaesthetic gases in Indian hospitals is scarce. To evaluate the possible genotoxic effects of waste anaesthetic gases, the chromosomal aberrations analysis and comet assay were studied in peripheral blood lymphocytes in 45 operating room personnel currently employed at a hospital in South India. In addition, the micronucleus test on buccal epithelial cells was also carried out in the same subjects. The exposed group was compared with a group of 45 non-exposed group, matched by age, sex, alcohol consumption and smoking habits. The results showed a statistically significant increase in DNA damage by the comet assay in the exposed group. Chromosome aberrations and micronucleus frequencies also increased significantly in the study subjects in comparison to the controls. Analysis of variance showed that smoking had a significant effect on DNA mean tail length, whereas alcohol consumption, duration of exposure to anaesthetic agents, age and gender had no significant effect. All the confounding factors had significant effect by the micronucleus test. However, smoking, alcohol consumption, age, gender and years of exposure showed no significant effect by the chromosome aberrations test. The results of our study suggest that exposure to waste anaesthetic gases has the potential to cause changes in the human genome.

Adult↗
PubMed1996

Rebreathing of exhaled gases: importance as a mechanism for the causal association between prone sleep and sudden infant death syndrome.

Twenty to 52% of sudden infant death syndrome (SIDS) victims are found dead with their noses and mouths turned into underlying bedding. Several items of bedding have been shown to increase the risk for SIDS in case-control studies or to be associated with many SIDS deaths in case series. These items of bedding are after limit CO2 dispersal more, and cause more rebreathing of exhaled gases than bedding infrequently associated with SIDS. Rebreathing of exhaled gases may explain some prone deaths, and avoiding rebreathing of these gases is one possible mechanism for the reduction in SIDS when infants avoid prone sleep. Results supporting these statements are reviewed and discussed.

Carbon Dioxide↗
PubMed1985

Arterial blood gases fail to reflect acid-base status during cardiopulmonary resuscitation: a preliminary report.

The American Heart Association's current standards for CPR indicate that acid-base therapy should be guided by measurements of arterial blood gases. However, we have discovered a striking discrepancy between arterial and venous blood gases during CPR: severe venous hypercarbia and acidosis may coexist with simultaneous arterial alkalosis. Arterial blood gases during CPR, therefore, may not accurately reflect the acid-base status of mixed venous blood and thus may fail to indicate systemic acid-base status.

Acid-Base Equilibrium↗
PubMed1987

Prediction of arterial blood gases by transcutaneous O2 and CO2 in critically ill hyperdynamic trauma patients.

The management of severe adult respiratory distress syndrome in critically injured patients requires the frequent measurement of arterial blood gases for adjustment of cardiovascular and ventilatory support. Since these require blood withdrawal and laboratory determinations, a noninvasive method of assessment of arterial gas tensions would permit more frequent assessment of the patient as well as permitting rapid changes in the patient's ventilatory status to be detected earlier in the clinical course. The role of transcutaneous O2 and CO2 tension in providing these measurements was evaluated in 92 studies in 38 critically ill patients with ARDS due to trauma and/or sepsis. All patients were normodynamic or hyperdynamic at the time of study (cardiac index 2.5 to 7.6 L/min/m2) and were intubated and on increased inspired oxygen fractions (FIO2 = 30 to 100%) delivered by mechanical ventilation, had a range of body temperature from 35.0 to 39.5 degrees C and pH from 7.29 to 7.57 The data from a transcutaneous O2 and CO2 sensor applied to the skin of the anterior thorax were analyzed by multiple regression analysis of variances. Prediction of the arterial oxygen tension (PaO2) from 52 to 253 torr was possible from regression-corrected measurements of the transcutaneous O2 (TcO2): [PaO2 = 1.1 (TcO2) - 0.28 (FIO2) + 45.5]. The arterial carbon dioxide tension (PaCO2) from 26 to 57 torr was predicted from the transcutaneous CO2 (TcCO2):[PaCO2 = 0.76 (TcCO2) + 0.06 (FIO2) + 0.035 (TcO2) + 4.1]. With these corrections, a noninvasive Respiratory Index was computed for assessing ARDS severity, and dynamic changes in arterial gases could be followed in response to postural changes, ventilatory alterations, or cardiovascular perturbations. These data suggest that a reasonable estimate of the arterial blood gases can be obtained from a regression-corrected measurement of the transcutaneous O2 and CO2 tensions in critically injured normodynamic or hyperdynamic ARDS patients.

Adult↗
PubMed1986

Why obtain arterial blood gases, chest x-rays, and clotting studies in injured children? Experience in a regional trauma center.

We conducted a retrospective study to determine the frequency with which arterial blood gases, chest x-rays, and blood clotting studies are obtained while caring for pediatric trauma victims in a regional trauma center, and if the clinician can predict which studies may be abnormal. Arterial blood gases were obtained in 35% of pediatric trauma victims, chest x-rays in 48%, and clotting studies in 56%. We found that abnormalities in arterial blood gases were correlated with closed head injury, intubation in the field, and sex of the patient, while abnormalities on chest x-ray correlated with closed head trauma and intubation in the field. Abnormalities in clotting studies correlated only with intubation in the field. Obtaining a chest x-ray on a pediatric trauma victim with an Injury Severity Score of less than 10 will yield little information. The utility of routine laboratory tests in pediatric trauma victims may vary significantly from that of laboratory tests in adult trauma victims.

Adolescent↗
PubMed2004

Impact of a correct breathing stereotype on pulmonary minute ventilation, blood gases and acid-base balance in post-myocardial infarction patients.

STUDY OBJECTIVE: The aim of the study was to evaluate the impact of a long-term (6-month) correct breathing stereotype on minute ventilation, capillary blood gases and acid-base balance in post-myocardial infarction patients. METHODS: Fifty-five men (age 57.2 +/- 12.5) were examined 2 months later after myocardial infarction. Spirometry and assessment of acid-base balance and capillary blood gases were performed at rest and repeated after 10 days and 6 months. Breathing correction was taught over 5 days. A session for the control and maintenance of the correct breathing skills was hosted once a month (during the 6-month period). RESULTS: Changes of minute ventilation, capillary blood gases and acid-base balance were revealed in 55% of patients 2 months later after myocardial infarction. Twenty patients (group I) were randomly selected for breathing correction while 10 patients made up the control group (group II). After breathing correction minute ventilation significantly decreased (18.5 +/- 5.5 versus 9.8 +/- 2.5 l/min), oxygen ventilatory equivalent decreased (39.8 +/- 5.2 versus 22.5 +/- 3.8), partial pressure of blood carbon dioxide increased (33.2 +/- 1.7 versus 44.2 +/- 2.5 mmHg), plasma bicarbonate concentration augmented (19.1 +/- 2.2 versus 24.5 +/- 1.8 mmol/l), base excess normalized (-2.90 +/- 2.5 versus +1.3 +/- 2.1 mmol/l), and pH shifted to more alkaline value (7.36 +/- 0.01 versus 7.43 +/- 0.02). CONCLUSIONS: A long-term correct breathing stereotype improved respiratory function and could be an additional measure in rehabilitation programmes for post-myocardial infarction patients.

Acid-Base Equilibrium↗
PubMed1999

Kinetic approach to granular gases.

We address the problem of the so-called "granular gases," i.e., gases of massive particles in rapid movement undergoing inelastic collisions. We introduce a class of models of driven granular gases for which the stationary state is the result of the balance between the dissipation and the random forces which inject energies. These models exhibit a genuine thermodynamic limit, i.e., at fixed density the mean values of kinetic energy and dissipated energy per particle are independent of the number N of particles, for large values of N. One has two regimes: when the typical relaxation time tau of the driving Brownian process is small compared with the mean collision time tau(c) the spatial density is nearly homogeneous and the velocity probability distribution is Gaussian. In the opposite limit tau>>tau(c) one has strong spatial clustering, with a fractal distribution of particles, and the velocity probability distribution strongly deviates from the Gaussian one. Simulations performed in one and two dimensions under the Stosszahlansatz Boltzmann approximation confirm the scenario. Furthermore, we analyze the instabilities bringing to the spatial and the velocity clusterization. Firstly, in the framework of a mean-field model, we explain how the existence of the inelasticity can lead to a spatial clusterization; on the other hand, we discuss, in the framework of a Langevin dynamics treating the collisions in a mean-field way, how a non-Gaussian distribution of velocity can arise. The comparison between the numerical and the analytical results exhibits an excellent agreement.

Journal Article↗
PubMed1999

Relativistic quantum thermodynamics of ideal gases in two dimensions.

In this work we study the behavior of relativistic ideal Bose and Fermi gases in two space dimensions. Making use of polylogarithm functions we derive a closed and unified expression for their densities. It is shown that both type of gases are essentially inequivalent, and only in the non-relativistic limit the spinless and equal mass Bose and Fermi gases are equivalent as known in the literature.

Journal Article↗
PubMed2002

Phase fluctuations in atomic Bose gases.

We improve on the Popov theory for partially Bose-Einstein condensed atomic gases by treating the phase fluctuations exactly. As a result, the theory becomes valid in arbitrary dimensions and is able to describe the low-temperature crossover between three-, two-, and one-dimensional Bose gases, which is currently being explored experimentally. We consider both homogeneous and trapped Bose gases.

Journal Article↗
PubMed2005

Ground-state properties of Fermi gases in the strongly interacting regime.

The ground-state energies and pairing gaps in dilute superfluid Fermi gases have now been calculated with the quantum Monte Carlo method without detailed knowledge of their wave functions. However, such knowledge is essential to predict other properties of these gases such as density matrices and pair distribution functions. We present a new and simple method to optimize the wave functions of quantum fluids using the Green's function Monte Carlo method. It is used to calculate the pair distribution functions and potential energies of Fermi gases over the entire regime from atomic Bardeen-Cooper-Schrieffer superfluid to molecular Bose-Einstein condensation, spanned as the interaction strength is varied.

Journal Article↗
PubMed2005

Ultracold two-component fermionic gases with a magnetic field gradient near a feshbach resonance.

We study theoretically the ultracold two-component fermionic gases when a gradient magnetic field is used to tune the scattering length between atoms. For 6Li at the narrow resonance B0=543.25 G, it is shown that the gases would be in a coexistence of the regimes of BCS, Bose-Einstein condensation (BEC), and unitarity limit with the present experimental technique. In the case of thermal and chemical equilibrium, we investigate the density distribution of the gases and show that a double peak of the density distribution can give us a clear evidence for the coexistence of BCS, BEC, and unitarity limit.

Journal Article↗
PubMed1986

The double mask--a new local scavenging system for anaesthetic gases and volatile agents.

The double mask, a new concept for local scavenging of anaesthetic gases escaping around face masks and from endotracheal tubes, is described. The system consists of a flexible silicone mask into which the anaesthetic gas mixture is led through a flow distributor which is necessary for adequate scavenging. A rigid transparent polysulphone shell surrounds the inner mask, and escaping gas is evacuated via the 3-4 mm slot between the two masks by a fan, centrally located outside the operating-room. With this system, the anaesthetist's exposure to nitrous oxide during mask anaesthesia was reduced from 145 +/- 29 to 15 +/- 3 ppm (mean +/- s.e. mean, P less than 0.001) and to halothane from 2.9 +/- 1.1 to 0.5 +/- 0.1 ppm (mean +/- s.e. mean, P less than 0.05), as measured in 32 patients aged 1-74 years. The double-mask system provided safe and adequate mask anaesthesia, as judged from inspired concentrations of anaesthetic and fresh gases and transcutaneous and blood gases in 24 patients. The noise level was low with a mean value under regular operating-room conditions around 45 dB(A) in the low frequency range. It is concluded that using the scavenging conditions provided by the system, the Swedish limits for anaesthesiologists' gas exposure could be reduced to the levels recommended by the US National Institute of Occupational Safety and Health (25 ppm for nitrous oxide and 0.5 ppm for halothane).

Adolescent↗
PubMed1988

Elimination of waste anaesthetic gases from operating theatres.

At present, waste anaesthetic gases in the operating theatre are eliminated by room ventilation and by additional measures such as scavenging by a double-mask system and a local exhaust system. A simple technique is proposed for measuring the capture efficiency (E) of different scavenging systems. E is the ratio of the waste anaesthetic gases captured by a system to the total quantity of waste anaesthetic gases produced. In a field study on existing unmodified system, E from a phantom pollutant source was measured using a portable measuring unit designed for displaying test results on location. The pollutant source was a leaking double-mask system. When scavenging from the double-mask system, E was 98% at an exhausted airflow of 28-33 m3/h. Using a local exhaust system at an airflow of 30 m3/h, E ranged from 20 to 96%, depending on the distance between the mask and the nozzle of the exhaust system.

Air Pollutants, Occupational↗
PubMed1996

Influence of age on circulation and arterial blood gases in man.

BACKGROUND: Modern data on the influence of age on hemodynamic and blood gas data in healthy subjects are sparse, especially in middle aged or older subjects. Most measurements have been done in patients during major surgery or in intensive care when the patients have one or more failing organ systems. This study reports on hemodynamics, blood gases and blood volume in healthy patients prior to anesthesia and elective surgery. METHODS: A total of 116 subjects (92 males, 24 females) were investigated prior to anesthesia and elective surgery. No one had received any premedication or was taking regular medication. All subjects were in good physical condition, except for their surgical disease, and clinical examination and history did not reveal any sign of cardiopulmonary disease. Measurements were made of systemic and pulmonary vascular pressures, cardiac output, arterial blood gases and blood volume by 131I-Albumin distribution. RESULTS: Cardiac output, stroke volume, and blood volume correlated to body surface. Relating these variables to body size eliminated almost all differences between the male and female groups. These variables, as well as both systemic and pulmonary artery systolic vascular pressures, were affected by increasing age. Pulmonary capillary wedge and right atrial pressures were not influenced by age. PaO2 decreased with age from 14.0 kPa at 20 years to 11.3 kPa at 80, whereas PaCO2 was unaltered. No effect of light smoking was found on pulmonary circulation or arterial blood gases. Significant correlations were found between blood volume on the one hand and body size and age on the other hand, but not in regard to sex.

Adult↗