Articles: closed-circuit-anesthesia.
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Cahiers d'anesthésiologie · Jan 1992
Randomized Controlled Trial Comparative Study Clinical Trial[A comparative study of the cost of open-circuit as opposed to closed-circuit ventilation].
The authors compared two open randomized groups of patients undergoing surgery through general anaesthesia. Group 1 consisted of 54 patients ventilated by a Siemens 900 B ventilator in open circuit, and group 2, 56 patients ventilated by an ELSA de Gambro ventilator in a closed circuit. Comparative hour cost for nitrous oxide (N2O), oxygen (O2) and halogen gas, Enflurane, Isoflurane, was noted. ⋯ In order to improve the effective cost of close circuit, the authors proposed: the use of closed circuit ventilation for more than 3 hours surgery, gas saturation in closed circuit after denitrogenation--which demands the use of halogen infjectors, and lime in containers cheaper than disposable cartridges. Respecting the above criteria, the total hour cost in close circuit fell to 4.90 FF, gain of 63% against open circuit. For O2 et N2O, the hour cost goes from 1.34 FF in close circuit to 13.28 FF in open circuit, 90% economy.(ABSTRACT TRUNCATED AT 250 WORDS)
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A clinical incident involving an undetected disconnection occurred during the use of a CPRAM coaxial breathing circuit. The flow resistance of this circuit was evaluated and compared with that of a Bain circuit to determine the factors involved. A differential pressure transducer was used to monitor the pressure drop across each circuit during simulation of controlled ventilation with a fresh gas flow of 6 L.min-1. ⋯ Since the ventilator low pressure alarm was preset to 9.2 cm H2O, the alarm provided a warning with the Bain but not the CPRAM. The elevated flow resistance of the CPRAM circuit was attributed to a restriction in the flow area at the patient end of the circuit. Capnographs or adjustable low-pressure alarms provide more reliable monitoring for breathing circuit disconnects.
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The fresh gas utilization (FGU) of a semi-closed breathing system is defined as the ratio of the amount of gas reaching the patient's lungs to the total amount of fresh gas flowing into the breathing system. It indicates to what extent a breathing system conserves anaesthetic gases and provides inspired gas concentrations as close as possible to those in the fresh gas, even at low fresh gas flows (FGF). ⋯ None of the systems tested showed the characteristics of an ideal system which would reach 100% FGU with an FGF less than minute volume. At FGF 3 litre min-1, FGU was: Gambro Engström Elsa 97.8%, Siemens Servo Ventilator 900 D with circle system 96.1%, Dräger Cicero 93.4%, Ohmeda Modulus II Plus 93.1%, Dräger 8 ISO 92.3%, Dräger AV1 87.6%, Megamed 700A 77.0% and Siemens Ventilator 710 74.1%.
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We describe an enclosed afferent reservoir (EAR) breathing system developed by Ohmeda and designed to operate efficiently in spontaneous and controlled ventilation. The efficiency of the system was evaluated by calculating the fractional utilization of fresh gas in 10 ASA I-III patients during anaesthesia with controlled ventilation. Maximum efficiency occurred when the minute ventilation to fresh gas flow ratio was greater than 1.5. ⋯ The minimum fresh gas flow for use during controlled ventilation was determined in another eight ASA I-III patients when the minute volume to fresh gas ratio was greater than 1.5. In view of an increased arterial to end-tidal carbon dioxide partial pressure difference in patients in the first part of the study (1.03 kPa), normocapnia was defined as an end-tidal carbon dioxide partial pressure of 4.3 kPa. Normocapnia was achieved with a mean fresh gas flow of 66 ml kg(-1) min(-1), while 70 ml kg(-1) min(-1) produced mild hypocapnia.
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To determine the impact of a low fresh gas flow rate on the duration of carbon dioxide (CO2) absorption by soda lime. ⋯ Because soda lime color indicators are unreliable, when a semiclosed breathing circle is used at a low rate of fresh gas flow without CO2 monitoring, the CO2 absorbent must be replaced more frequently.