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PubMed1986

[Determination of the distribution of ventilation-perfusion ratios: technic of elimination of multiple inert gases].

The multiple inert gas elimination technique (MIGT) facilitates the estimation of the distributions of ventilation-perfusion (VA/Q) ratios in the experimental and clinical setting. The most relevant technical aspects and equipment and operational requirements needed to measure a mixture of inert gases in both the gas phase and the blood phase using gas chromatography are overviewed with detail. Results obtained in 3 dogs and 4 syringe-homogeneous lung models were entirely consistent with data formerly reported in the literature. Particular attention is paid to the linearity of the gas chromatograph detectors, reproducibility of inert gases sampling, and analysis of brands of heparin to detect acetone content. The errors of measurement (coefficients of variation) in blood were: 1.4 for sulfur hexafluoride; 1.8% for ethane; 2% for cyclopropane and halothane, each; 2.4% for diethyl ether; and, 3.6% for acetone. Important practical points are also emphasized in order to draw attention to potential problems and issues that should be concentrated upon to minimize the error in the measurements. It is concluded that the setting up of the MIGT is well established and validated.

Animals↗
PubMed1987

Turning the mass-spectrometer into an easy to handle clinical instrument for routine multipatient surveillance of respiratory and anesthetic gases during anesthesia.

Although most authors use it as the reference instrument for respiratory gases measurement, the use of mass-spectrometer in clinical routine in ICU and in anesthesia remains quite limited. We developed a fully automatically controlled system, carrying on a twinned goal: The ACS-2000 (Automatic Calibration System) turns the Airspec MGA-2000 mass-spectrometer into a true clinical instrument, as easy to use as any routine monitoring instrument, and lets the clinician and the anesthetist benefit from its uncomparable metrological performances. PAMS-M, multibed monitoring system, shares the mass-spectrometer time among 4 to 8 rooms, providing each anesthetist with full composition of inspired and end tidal gases composition, trend evolution of those data, as with the display of capnogram. Each room is equipped with an IBM PC compatible intelligent terminal, abling the user to select the nature of the displayed information and enter into an easy menu driven dialog with the system. As a subproduct, the informatic infrastructure on which the system is based allowed, beyond the standard monitoring function, to set the bases of a computerized patient's anesthesia or respiratory monitoring report.

Anesthetics↗
PubMed1980

[Classification of harmful gases].

The classification of harmful gases may be envisaged in various ways according to the criteria considered. The two aspects adopted here concern chemical and toxicological classifications. Chemical classification is in general based upon the nature of the elements constituting the gases, e.g. carbon, nitrogen, sulphur, phosphorus, halogen compounds and halogenated compounds, etc. Toxicological classification is envisaged on the basis of the concepts of toxicity itself. It may then be used to establish the scale of its degree based upon two principal factors: concentration and duration of exposure. However, certain observations suggest complex intoxication phenomena related to an overall number of factors which are generally considered in isolation.

Animals↗
PubMed1984

Technical conception for an anesthesia system with electronic metering of gases and vapors.

The technical conception for an anesthesia system will be presented, which is designed to measure and to meter anesthetic gases and anesthetic vapor under computer control. By these means the oxygen supply and anesthetic vapor supply to the patient can be automated, which should allow to improve the patient's safety during anesthesia. In order to meet these objectives novel systems for measurement and metering of gases and anesthetic vapors have to be developed. Prototypes of these components will be described and a first design proposal for the anesthesia system will be presented.

Anesthesia, Inhalation↗
PubMed1985

Arterialized capillary blood gases and acid-base studies in normal individuals from 29 days to 24 years of age.

Studies of arterialized capillary blood gases and acid-base values were performed on 712 normal persons who were between the ages of 29 days and 24 years. The results were divided for clinical use into six groups by age; linear regression lines were constructed for better understanding of the development of blood gas levels and the acid-base balance. The blood pH essentially remained unchanged throughout the study period. The oxygen and carbon dioxide pressures, base excess of extracellular fluid, and buffer base and bicarbonate levels are lower in infants than in children and adults; adult values are reached at approximately 7 to 12 years of age. The probable explanation for the lower values in infants is discussed. The effects of crying on the composition of blood gases are mentioned.

Acid-Base Equilibrium↗
PubMed2000

Ionization of ozone/chlorofluorocarbon mixtures in atmospheric gases: formation and remarkable dissociation of

The reactions occurring upon ionization of mixtures containing ozone and CHX2Y (X = H, Cl, F; Y = Cl, F) halocarbons diluted in atmospheric gases (O2, N2) have been investigated in detail by mass spectrometric and theoretical methods. In all systems investigated the reactivity pattern is characterized by the preliminary formation of [CHXY x O3+] adducts which undergo unimolecular dissociation into HXYO2+ and CO. This remarkable dissociation which requires extensive molecular reorganization is exceptional for hydrogenated halocarbons. The work represents the first systematic study of the ionic chemistry in systems containing both ozone and halocarbons diluted in atmospheric gases.

Journal Article↗
PubMed1991

Responses of the L5178Y mouse lymphoma forward mutation assay: V. Gases and vapors.

A new protocol for testing vapors and gases in the L5178Y mouse lymphoma assay is presented. Four chemicals, propylene, 1,2-propylene oxide, 1,3-butadiene, and vinylidene chloride, were tested for their mutagenic potential. Cultures were exposed to the chemicals, which were delivered as vapors or gases, for 4 hr, then cultured for 2 days before plating in soft agar with or without trifluorothymidine (TFT), 3 microgram/ml. Each chemical was tested at least twice. Significant responses were obtained with 1,2-propylene oxide and vinylidene chloride, but neither cytotoxicity nor mutagenicity was induced by 1,3-butadiene; propylene could not be classified as either mutagenic or non-mutagenic in the assay. Rat liver S9 mix was not a requirement for the mutagenic activity of 1,2-propylene oxide, whereas the liver preparation markedly enhanced both the cytotoxicity and mutagenicity of vinylidene chloride.

Air Pollutants↗
PubMed1990

Effect of different target gases on low-energy collision-activated dissociation of peptides.

Experimental variables affecting the daughter-ion spectra of a series of protonated peptides [MH]+, produced by fast-atom bombardment ionization, using a low energy (0-450 eV) quadrupole collision cell are investigated. The parameters studied include target gas pressure, collision energy, cross-sectional area and acidity of the target gas. The results show that low-mass immonium ions are preferentially formed both at high collision energies (greater than 200 eV) and at target gas pressures greater than 10(-6) mBar (where multiple collisions occur in the gas cell). Positive fragment ion abundance is maximized when acidic gases are used as the target gases, and this is rationalized on the basis of a proton-transfer reaction from the target gas to the amide nitrogen of the peptide bond promoting fragmentation.

Enkephalin, Leucine↗
PubMed2004

Middle cerebral artery Doppler indices at different sites: prediction of umbilical cord gases in prolonged pregnancies.

OBJECTIVES: To assess the value of middle cerebral artery Doppler indices obtained from different sampling sites in predicting umbilical cord gases at delivery in prolonged pregnancies. METHODS: This was a prospective study of consecutive pregnant women referred for prolonged-pregnancy surveillance. The predictive value of distal and proximal middle cerebral artery Doppler indices for cord blood gases was evaluated in women who delivered within 48 h of their last antenatal test using stepwise multiple regression. RESULTS: There was a significant linear correlation between proximal and distal middle cerebral artery pulsatility indices (R = 0.777; P < 0.0001), the mean values being 1.49 (SD, 0.45) and 1.56 (SD, 0.47), respectively. There was also a linear correlation between proximal and distal cerebroplacental ratios (R = 0.68; P < 0.0001), the mean values being 1.85 (SD, 1.96) and 1.92 (SD, 1.89), respectively. The stepwise multiple regression analysis for umbilical artery pH showed that once the distal middle cerebral artery pulsatility index was introduced into the model, the addition of any variable did not result in a significant improvement of the predictive capacity. The model showed a coefficient of determination (R(2)) of 0.079. There was a significant correlation between umbilical artery pO(2) and both proximal middle cerebral artery pulsatility index (positive) and the occurrence of elective Cesarean section (negative). This model accounted for 21% of the variance (R(2) = 0.21). No other variables added any significant prediction for pO(2). CONCLUSIONS: In post-term pregnancies the proximal middle cerebral artery pulsatility index significantly predicts umbilical artery pO(2) at delivery but does not predict pH. There is a weak association between distal middle cerebral artery pulsatility index and pH but, as this only explains 8% of the variance, it is of little clinical value.

Adult↗
PubMed1999

Effects of vaginal birth versus caesarean section birth with general anesthesia on blood gases and brain energy metabolism in neonatal rats.

Using a rat model, several laboratories have demonstrated long-term effects of Caesarean section (C-section) birth or of global hypoxia during C-section birth on a variety of central nervous system (CNS) parameters. These studies used C-section delivery from rapidly decapitated dams, to avoid confounding anesthetic effects, or from dams anesthetized with halothane or ether under unspecified conditions. Systemic oxygenation or cerebral energy metabolites in the pups at birth have not been systematically measured in this model. To develop and characterize a C-section model with relevance to the human situation, the present study measured arterial/venous blood gases and pH and brain ATP and lactate, a widely accepted measure of CNS hypoxia, in pups born either vaginally, by C-section from decapitated dams, or by C-section from dams anesthetized with nitrous oxide (N2O) and increasing concentrations of isoflurane under well-defined conditions. Immediately after birth, pups born vaginally, by C-section with maternal decapitation, or by C-section with 2.5% isoflurane showed no group differences in systemic pO2 or pH or brain ATP levels, but pCO2 was elevated in the C-section/2.5% isoflurane group. Pups born by C-section with 3.0, 3.5, or 4.0% isoflurane, showed progressive reductions in blood pO2 and increases in pCO2 and blood pH was reduced with 3.5% isoflurane. Relative to vaginal birth, brain lactate levels were unchanged in pups born by C-section with any concentration (2.5-4.0%) of isoflurane, but reduced in pups born by C-section from decapitated dams. At 1 h (and 4 h) after birth, in both vaginally born controls and the 2.5% isoflurane group, brain lactate fell while blood pO2 and brain ATP remained stable. In the 3.0, 3.5, or 4.0% isoflurane groups, blood gases and pH and brain lactate also normalized to control values. In conclusion, rat neonates show minimal signs of systemic or CNS hypoxia following C-section birth under 2.5% isoflurane with N2O. However, there is a rather narrow window of isoflurane concentrations which produces effective maternal anesthesia without producing respiratory compromise in the neonate. Thus the results indicate that the level of maternal anesthesia employed is an important factor influencing neonatal systemic and CNS oxygenation during C-section birth.

Adenosine Triphosphate↗
PubMed1987

Continuous monitoring of alveolar and inspiratory concentrations of anesthetic and respiratory gases is difficult and potentially unsafe.

One essayist suggests that continuous monitoring of alveolar and inspiratory concentrations of anesthetic and respiratory gases has little or no positive effect on patient outcome and may even be detrimental to patients. Such monitoring, he says, tends to remove anesthesiologists from personal contact with their patients. He recommends careful monitoring of fresh gas concentrations leaving the anesthetic machine, careful monitoring of inspired gas in a circle absorption breathing system, and improved training of anesthesiologists to prevent human error. Another essayist suggests that continuous monitoring of alveolar and inspiratory concentrations of anesthetic and respiratory gases is cost-effective and relatively simple. He says that such monitoring, without being a source of legal problems for its users, improves the quality of patient care.

Anesthesiology↗
PubMed1989

Effects of diagnostic procedures during fiberoptic bronchoscopy on heart rate, blood pressure, and blood gases.

To investigate the effects of several endoscopic procedures like introduction of the bronchoscope, removal of the instrument, catheter suction, bronchoalveolar lavage and transbronchial biopsy on heart rate, systemic blood pressure, and transcutaneously measured blood gases 77 consecutive patients (age, 20-83 years) were studied. All patients received 101 O2/min via face mask during bronchoscopy. Sedation was performed with midazolam or diazepam. The different characteristics of each patient, e.g. age, sex, smoking habits, baseline values of heart rate and systemic blood pressure, underlying pulmonary disease and kind of premedication were examined separately to analyse their special effects on the course of bronchoscopy. During the fiberoptic bronchoscopy neither a slight decrease in transcutaneous pO2 nor a small increase in transcutaneous pCO2 led to a critical situation. Nevertheless it should be stressed that the time after removal of the instrument and finishing supplemental oxygen may be critical regarding hypoxia and hypercapnia especially in older patients with hypoxia being already present before starting the endoscopy. The hemodynamic indices did not change significantly. There was no difference between midazolam or diazepam concerning the parameters under study. If supplemental oxygen is given and adequate premedication is performed, monitoring of hemodynamics and blood gases during fiberoptic bronchoscopy is not necessary in patients without cardiovascular or respiratory risk.

Adult↗
PubMed1984

The effect of ether, pentobarbitone sodium and fentanyl on blood gases, acid-base balance and hematological parameters in the rat.

Blood gases, acid-base balance and hematological parameters (RBC, PCV and Hb) were measured in adult rats of both sexes. The use of ether and fentanyl had a very little effect on the blood gases and acid-base balance. The induction of pentobarbitone anesthesia, however, was followed by a significant increase in PCO2 and TCO2, while the pH value decreased.

Acid-Base Equilibrium↗
PubMed1992

Mathematical model for the exchange of gases in the lungs with special reference to carbon monoxide.

A mathematical model has been formulated for the simultaneous exchange of gases O2, CO2, CO and N2 in the lungs. The model takes into account the physiological parameters, such as ventilation rate, diffusing capacity of the lungs, cardiac output, total volume of blood in the body and the interaction of gases in the blood. The nonlinear functions for representing O2, CO2 and CO dissociation curves have been used. The results predicted from the model are in good agreement with those based on the ventilation/perfusion relationships. The COHb build-up in the blood, computed from the model as a function of exposure time, is in good agreement with the experimental values. The consideration of capillary blood pO2 as a constant value, instead of an independent variable, is shown to introduce a maximum error of 0.25 per cent in the blood COHb. The model is applied to analyse the COHb levels at high altitude.

Carbon Monoxide↗
PubMed1995

[Effect of halothane on ventilation and arterial blood gases in rats with and without diaphragmatic paralysis].

Some patients with diaphragmatic paralysis or dysfunction maintain ventilation by use of other muscles. Anaesthesia, in modifying the performance of these muscles, presents a potential risk to such patients. To evaluate this risk, the effects of halothane on ventilation and arterial blood gases were studied on a model of bilateral diaphragmatic paralysis, the phrenectomized rat. The study was performed on 43 rats. Success of phrenectomy was confirmed at laparotomy, which did not result in blood gas changes. Laparotomy was performed in 23 rats and a carotid artery was catheterized. In 11 control rats, phrenic nerves were exposed but not sectioned, and in 12 other rats, the phrenic nerves were sectioned. Ventilation was measured by plethysmography in awake rats before and after surgery and in the same rats anaesthetized with halothane 1.1%. In the 23 rats, a decrease in weight and core temperature was observed after operation and this was more marked in phrenectomized than in control rats. In the 11 control rats, ventilation increased postoperatively without change in blood gases. In these rats, halothane caused a decrease in minute ventilation and PaO2 and an increase in PaCO2. Phrenectomy in awake rats led to an increase in minute ventilation, hypoxaemia and hypercapnia. In these rats, halothane led to death in three and a decrease in minute ventilation, with hypercapnia and hypoxaemia in the nine other rats. Blood gas changes were greater than in anaesthetized controls. In the intact rat, halothane leads to blood gas changes comparable to those observed in other species and humans. The present study confirms the effects of halothane on respiratory muscles other than the diaphragm and demonstrates the severe respiratory risk of anaesthesia in patients whose ventilation is maintained by these muscles.

Anesthesia, Inhalation↗
PubMed1996

Respiratory mechanics and arterial blood gases during and after laparoscopic cholecystectomy.

PURPOSE: The purpose of this study was to assess the effects of increased intra-abdominal pressure due to CO2 insufflation on the mechanical characteristics of the respiratory system and arterial blood gases during and after laparoscopic cholecystectomy. METHODS: Respiratory mechanics and arterial blood gases were examined in 12 patients undergoing laparoscopic cholecystectomy with CO2 insufflation. Respiratory mechanics were continuously monitored with in-line spirometry. In the recovery room, PaCO2 was measured in this group at 30 min and compared with PaCO2s in 23 patients who had undergone open cholecystectomy retrospectively, to evaluate the effects of insufflation on CO2 elimination. RESULTS: Minute ventilation was decreased by about 500 ml.min-1 during abdominal insufflation. Dynamic lung compliance decreased from 49.6 +/- 4.7 to 30.7 +/- 2.3 (mean +/- SEM) ml.cmH2O-1 with abdominal insufflation (P < 0.005), and returned to 45.1 +/- 3.1 after the release of pneumoperitoneum. Peak inspiratory pressure increased from 15.9 +/- 0.9 to 18.9 +/- 1.0 cmH2O with abdominal insufflation (P < 0.05). Arterial blood gas determinations indicated a decrease in arterial pH, with CO2 retention during insufflation and in the recovery room (P < 0.05). PaCO2 of the laparoscopic patients was higher than that of the open patients in the recovery room. CONCLUSION: The results indicate that respiratory acidosis was caused during CO2 insufflation for laparoscopic cholecystectomy, that was due to (1) decreased compliance, (2) increased CO2 load and (3) insufficient ventilation. Accumulated CO2 during laparoscopic cholecystectomy increased PaCO2 level in the recovery room.

Adult↗
PubMed1996

[Exposure of operating room personnel to anesthetic gases during ENT interventions].

During ENT surgical procedures under general anesthesia contamination of the operating room air through waste anesthetic gases seems unavoidable. A resulting chronic low-level exposure to anesthetic gases in subanesthetic concentrations (m1/m3 = ppm) may cause various negative health effects. The aim of this study was to quantify possible side effects on operating room personnel. By using a highly sensitive, direct reading instrument for determining contamination leakage from a patient's mouth and resulting concentrations in the breathing zone of the surgeon and anesthetist, levels of isoflurane and nitrous oxide were measured at 2-min intervals during 20 ENT surgical procedures performed under usual workplace conditions. Despite high concentrations of anesthetic at the mouth of each patient, personnel-related mean values remained under recommended threshold values (TLV) of 10 ppm isoflurane. A TLV of 100 ppm nitrous oxide was exceeded in 20% of the operations. Furthermore, a safe TLV for pregnant staff was 25 ppm nitrous oxide. This value was exceeded during nearly all operations (93%) for the group "surgeon". High leakages at the patient's mouth led to an undesirably high contamination of operating room personnel by nitrous oxide. Although threshold values were mostly not exceeded in available working conditions (i.e., adequate air conditioning and intubation cuff pressure control), present health and safety regulations concerning pregnant women showed that the values of nitrous oxide were still too high to allow such women to work safely in operating rooms during surgery. However, exposure to isoflurane was too slight to classify.

Adult↗
PubMed2005

Effects of body temperature on blood gases.

BACKGROUND: Changes in body temperature have important impact on measurements of blood gases. In blood gas analyzers the samples are always kept constant at a temperature of exactly 37 degrees C during the measurements, and therefore results are not correct if body temperature differs from 37 degrees C. OBJECTIVE: Lack of knowledge of the effects of body temperature on results of blood gas monitoring may lead to wrong and potentially harmful interpretations and decisions in the clinical setting. The following article elucidates alterations in monitoring of blood gases and oxyhemoglobin saturation (SO(2)) that occur during changes in body temperature.

Blood Gas Monitoring, Transcutaneous↗