Articles: closed-circuit-anesthesia.
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Randomized Controlled Trial Clinical Trial
The effect of a heat and moisture exchanger on humidity in a low-flow anaesthesia system.
The heat and humidity in a low-flow breathing system was measured in order to study the inherent humidifying properties of the system at low fresh gas flows (< 1 and 21.min-1) and whether a heat and moisture exchanger could compensate for the loss of heat and humidification occurring at higher fresh gas flows (51.min-1) in these systems. Sixty patients were randomly divided into three groups (< 1, 2 and 51.min-1 fresh gas flows) with a heat and moisture exchanger and three groups without a heat and moisture exchanger in the breathing system. ⋯ Three more measurements were performed at 10, 30 and 60 min after control. At low fresh gas flows the humidifying properties of the low-flow breathing system are adequate (i.e. provide an absolute humidity > 20 mg.l-1) but at a fresh gas flow of 51.min-1 there is a need for a heat and moisture exchanger for adequate humidification of the inspired gas.
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We have sought to define a way in which nitrous oxide can be safely and universally used at minimal to low flows by utilising a circle system with a controlled leak provided by a standard gas analyser sampling line and a fresh gas supply of 50% nitrous oxide in oxygen, entering from a trunk interposed between the ventilator and the circle system. Although preliminary calculations suggested that this arrangement was likely to work, it was found that 13 of 23 patients studied prospectively developed an inspired oxygen fraction below 0.3. We conclude that, although this arrangement provides a new means of introducing nitrous oxide into the circle breathing system, it does not appear inherently safer or more convenient than the conventional route.
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Xenon is an inert gas with a practical anesthetic potency (1 MAC = 71%). Because it is very expensive, the use of closed circuit anesthesia technique is ideal for the conduction of xenon anesthesia. Here we describe our methods of starting closed circuit anesthesia without excessive waste of xenon gas. ⋯ To prime the circuit, we push xenon using a large syringe into a circuit, which was prefilled with oxygen. Oxygen inside the circuit is pushed out before it is mixed with xenon, and xenon waste will thus be minimized. In this way, we can achieve close to 1 MAC from the beginning of xenon anesthesia, and thereby minimize the risk of light anesthesia and awareness during transition from denitrogenation to closed-circuit xenon anesthesia.
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Ann Fr Anesth Reanim · Jan 1997
[PhysioFlex: a target-controlled self-regulating closed-circuit inhalation anesthesia regulator].
Physi Flex is the first commercially available apparatus capable for quantitative, or self-regulating target controlled inhalational anaesthesia, with a totally closed circuit, in adults and children. The fresh gas supply to the circuit is intermittent, automatically regulated by continuous monitoring of the volume and composition of the gas mixture in the breathing circuit. The circle system includes, instead of the two conventional one way valves, a blower creating a continuous unidirectional flow at 70 L.min-1. ⋯ The O2-flow and consumption, the N2O flow and uptake, FICO2 and FETCO2, FI and FET of the volatile anaesthetic, all other important data are displayed in a numerical and graphical form on a color screen and registered for a delayed analysis. The end tidal concentration of the volatile anaesthetic drives a stepmotor with a syringe containing the selected volatile anaesthetic agent with is directly injected into the breathing circuit where it is vaporized. Therefore the concentration of the anaesthetic vapour can be instantaneously increased with this injector at induction and lowered at end of anaesthesia with the carbon absorber, and the fresh gas consumption is significantly decreased.
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J. Tongji Med. Univ. · Jan 1997
Randomized Controlled Trial Clinical TrialMultiple respiratory gas monitoring causes changes of inspired oxygen concentration in closed anesthesia system.
Effect of multiple respiratory gas monitoring (MRGM) on inspired concentration of oxygen in circuit system during closed anesthesia was studied in 51 adult patients scheduled for abdominal surgery. Required flow rate of fresh oxygen (OFR), inspired oxygen concentration (FiO2) and oxygen saturation of pulse oximeter (SpO2) were measured continuously. Patients were equally divided into three groups at random, group C (no MRGN used), group M1 (using MRGM with its tail gas returned to circuit system), group M2 (using MRGM without tail gas returned). ⋯ In group M1, FiO2 decreased by 16% at 60 min and 34% at 180 min and the decrease was significantly greater than that in group C (P < 0.01). In group M2, FiO2 remained constant during closed anesthesia, which was much higher than those in group C and M1. The tail gas of Capnomac Ultima MRGM contained less oxygen than its sample gas drawn from circuit system simultaneously.