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Fresh Gas (fresh + gas)
Terms modified by Fresh Gas Selected AbstractsLarger tidal volume increases sevoflurane uptake in blood: a randomized clinical studyACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2010B. ENEKVIST Background: The rate of uptake of volatile anesthetics is dependent on alveolar concentration and ventilation, blood solubility and cardiac output. We wanted to determine whether increased tidal volume (VT), with unchanged end-tidal carbon dioxide partial pressure (PETCO2), could affect the arterial concentration of sevoflurane. Methods: Prospective, randomized, clinical study. ASA physical status 2 and II patients scheduled for elective surgery of the lower abdomen were randomly assigned to one of the two groups with 10 patients in each: one group with normal VT (NVT) and one group with increased VT (IVT) achieved by increasing the inspired plateau pressure 0.04 cmH2O/kg above the initial plateau pressure. A corrugated tube added extra apparatus dead space to maintain PETCO2 at 4.5 kPa. The respiratory rate was set at 15 min,1, and sevoflurane was delivered to the fresh gas by a vaporizer set at 3%. Arterial sevoflurane tensions (Pasevo), Fisevo, PETsevo, PETCO2, PaCO2, VT and airway pressure were measured. Results: The two groups of patients were similar with regard to gender, age, weight, height and body mass index. The mean PETsevo did not differ between the groups. Throughout the observation time, arterial sevoflurane tension (mean±SE) was significantly higher in the IVT group compared with the NVT group, e.g. 1.9±0.23 vs. 1.6±0.25 kPa after 60 min of anesthesia (P<0.05). Conclusion: Ventilation with larger tidal volumes with isocapnia maintained with added dead-space volume increases the tension of sevoflurane in arterial blood. [source] Low-flow anaesthesia at a fixed flow rateACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 10 2009A. CHERIAN Aims and Objectives: This study attempts to assess the safety of low-flow anaesthesia (LFA) at fixed flow rates with particular reference to the incidence of a decline in FiO2 below safe levels of 0.3 and to determine whether LFA can be used safely in the absence of an FiO2 monitor. Methods: A total of 100 patients undergoing procedures under general anaesthesia at fresh gas flows of 300 ml/min of O2 and 300 ml/min of N2O were monitored while maintaining the dial setting of isoflurane at 1.5% for 2 h. The changes in gas composition were analysed and even a single recording of FiO2 of <0.3 was considered sufficient to render the technique unsafe in the absence of gas monitors. Results: The lowest recorded value of FiO2 was 31% (v/v%). There was no incidence of adverse events necessitating the conversion from low flows to conventional flows. Conclusions: We conclude that low flows of 300 ml/min of N2O and 300 ml/min of oxygen can be used safely for a period of 2 h without the use of monitors for gas analysis of oxygen and agent in adult patients weighing between 40 and 75 kgs. [source] Increase in the use of rebreathing gas flow systems and in the utilization of low fresh gas flows in Finnish anaesthetic practice from 1995 to 2002ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 3 2005H. Tohmo Background:, The use of rebreathing systems together with low fresh gas flows saves anaesthetic gases, reduces the costs of anaesthesia, causes less environmental and ergonomic adverse effects, i.e. less air contamination in the operating room, and has favourable physiological effects. We assessed whether the use of non-rebreathing vs. rebreathing gas flow systems and high vs. lower fresh gas flows has changed during recent years. Methods:, The use of rebreathing and non-rebreathing systems and the utilization of fresh gas flows were evaluated by sending a questionnaire to the heads of anaesthesia departments at all public health care hospitals in Finland in 1996 and 2003. The data was gathered from the previous years 1995 and 2002, respectively. Results:, The use of rebreathing systems increased from 62% to 83% of all instances of general anaesthesia (P < 0.001). In rebreathing gas flow systems, there was a significant shift from high fresh gas flows (3 l min,1 and more) towards lower fresh gas flows (between 1 to 2 l min,1 and even below 1 l min,1) (P < 0.001). Conclusions:, The benefits of low fresh gas flows have now been achieved in most instances of rebreathing system anaesthesia, which was not the case in 1995. [source] The effect of heat and moisture exchanger on humidity and body temperature in a low-flow anaesthesia systemACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 5 2003A. Johansson Background: Artificial humidification of dry inspired gases seems to reduce the drop in body temperature during surgery. The aim of this study was to evaluate the humidity and temperature of anaesthetic gases with heat and moisture exchangers (HMEs). The secondary aim was to evaluate if HMEs in combination with low-flow anaesthesia could prevent a decrease in the body temperature during general anaesthesia. Methods: Ninety patients scheduled for general surgery were randomised to receive a fresh gas flow of 1.0, 3.0 or 6.0 l min,1 with or without HMEs in a circle anaesthesia system. Relative humidity, absolute humidity, temperature of inspired gases and body temperatures were measured during 120 min of anaesthesia. Results: The inspiratory absolute humidity levels with HMEs were 32.7 ± 3.1, 32.1 ± 1.1 and 29.2 ± 1.9 mg H2O l,1 and 26.6 ± 2.3, 22.6 ± 3.0 and 13.0 ± 2.6 mg H2O l,1 without HMEs after 120 min of anaesthesia with 1.0, 3.0, or 6.0 l min,1 fresh gas flows (P < 0.05, between with and without HME). The relative humidity levels with HMEs were 93.8 ± 3.3, 92.7 ± 2.2 and 90.7 ± 3.5%, and without the HMEs 95.2 ± 4.5, 86.8 ± 8.0 and 52.8 ± 9.8% (P < 0.05, between with and without HMEs in the 3.0 and 6.0 l min,1 groups). The inspiratory gas temperatures with HMEs were 32.5 ± 2.0, 32.4 ± 0.5 and 31.0 ± 1.9°C, and 28.4 ± 1.5, 27.1 ± 0.8 and 26.1 ± 0.6°C without HMEs after 120 min of anaesthesia (P < 0.05, between with and without HME). The tympanic membrane temperatures at 120 min of anaesthesia were 35.8 ± 0.6, 35.5 ± 0.6 and 35.4 ± 0.8°C in the groups with HMEs, and 35.8 ± 0.6, 35.3 ± 0.7 and 35.3 ± 0.9°C in the groups without the HMEs (NS). Conclusions: The HMEs improved the inspiratory absolute humidity, relative humidity and temperature of the anaesthetic gases during different fresh gas flows. However, the HMEs were not able to prevent a body temperature drop during low-flow anaesthesia. [source] CO2 elimination at varying inspiratory pause in acute lung injuryCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 1 2007J. Aboab Summary Previous studies have indicated that, during mechanical ventilation, an inspiratory pause enhances gas exchange. This has been attributed to prolonged time during which fresh gas of the tidal volume is present in the respiratory zone and is available for distribution in the lung periphery. The mean distribution time of inspired gas (MDT) is the mean time during which fractions of fresh gas are present in the respiratory zone. All ventilators allow setting of pause time, TP, which is a determinant of MDT. The objective of the present study was to test in patients the hypothesis that the volume of CO2 eliminated per breath, VTCO2, is correlated to the logarithm of MDT as previously found in animal models. Eleven patients with acute lung injury were studied. When TP increased from 0% to 30%, MDT increased fourfold. A change of TP from 10% to 0% reduced VTCO2 by 14%, while a change to 30% increased VTCO2 by 19%. The relationship between VTCO2 and MDT was in accordance with the logarithmic hypothesis. The change in VTCO2 reflected to equal extent changes in airway dead space and alveolar PCO2 read from the alveolar plateau of the single breath test for CO2. By varying TP, effects are observed on VTCO2, airway dead space and alveolar PCO2. These effects depend on perfusion, gas distribution and diffusion in the lung periphery, which need to be further elucidated. [source] | ||||||||||