Articles: closed-circuit-anesthesia.
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Anaesth Intensive Care · Jun 1995
Comparative StudyComparison in spontaneous ventilation of the Maxima with the Humphrey ADE breathing system and between four methods for detecting rebreathing.
An enclosed efferent, afferent reservoir breathing system (Maxima, Life Air Pty Ltd), being valveless, was compared to a simple afferent reservoir system (Humphrey ADE, A mode), having a valve, by assessing fresh gas flow (VF) requirements, with respect to ventilation (VE), that prevents rebreathing in volunteers, awake and breathing spontaneously. The results are recorded in terms of the quotient VF/VE associated with the onset of rebreathing. ⋯ Our findings showed that the method of sampling carbon dioxide (CO2) at the outflow of the efferent limb of the patient connector (eliminated CO2 method) in both afferent reservoir systems provided the highest flow rate and most reliable indication for detecting potential or actual rebreathing, when attempting to minimize VF. It provides no additional deadspace or resistance to gas flow, and has the advantage of being the only qualitative method that is reliable for the purpose of detecting the onset of rebreathing.
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Anaesth Intensive Care · Jun 1995
Comparative StudyMaxima and Bain breathing systems compared in controlled ventilation.
The Maxima is a new universal breathing system, which, despite its being valveless, functions with near maximal efficiency in spontaneous and controlled ventilation. It was compared to the Bain system in controlled ventilation by adjusting fresh gas flows (VF) to achieve an end-tidal CO2 of 5% in 40 patients aged from one to seventy-six years. They received a combined regional and general anaesthetic technique. ⋯ The mean VF requirement for the Bain system was greater by 45%. Of these forty patients, the results from the twenty-four adult patients weighing 50 kg or more gave the respective VF requirements for the Maxima and Bain systems of 52 and 71 ml.min-1.kg-1. In a separate study using twenty-nine patients, the fractional utilization of fresh gas (FU) (or VAe/VF where VAe = effective alveolar ventilation) in the Maxima and Bain systems was shown to be 0.94 and 0.71 respectively.
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Anasthesiol Intensivmed Notfallmed Schmerzther · Feb 1995
Biography Historical Article[John Snow (1813-1858): experimental studies on rebreathing of anesthetic gases in exhaled air].
As early as in 1850 (only 4 years after the first clinical performance of ether anaesthesia by W. T. G. ⋯ Even in the fundamental articles by D. Jackson and R. Waters, both being the respected protagonists of the rebreathing technique in anaesthesia, the Snow papers remained uncited.
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Comparative Study
[Measurements of ventilatory parameters during closed circuit anesthesia--comparisons with semiclosed circuit, high-flow anesthesia].
Since induction of anesthesia using a closed-circuit technique is difficult with most modern anesthesia machines, it is a common clinical practice to convert semiclosed, high-flow anesthesia (SCA) to closed circuit anesthesia (CCA) during the maintenance phase by decreasing the fresh gas flow. The purpose of the current studies was to determine if such changes in the fresh gas flow influence parameters of ventilatory dynamics. The tidal volume, airway pressure, and a ratio of expiratory volume in one second to a tidal volume (EV1.0/VT) were measured in six patients and in a lung simulator during CCA with a fresh gas flow of 200 ml.min-1 and SCA with a flow of 6 l.min-1. ⋯ It was also suggested that these differences were secondary to differences in the fresh gas flow and not to the circuit situation (closed vs. semiclosed) per se. The results emphasize that the fresh gas flow should be taken into consideration in interpreting the data of ventilatory dynamics during anesthesia. This is especially so during CCA because CCA employs a minimum fresh gas flow.
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Appl Cardiopulm Pathophysiol · Jan 1995
Experiences with the new inhalational agents in low-flow anesthesia and closed-circuit technique. Monitoring and technical equipment.
During recent years interest has focused on two completely fluorinated ethers, desflurane and sevoflurane, which promise a shorter induction of and emergence from anesthesia. Their physicochemical properties differ from isoflurane, enflurane and halothane, thus requiring new technical equipment and leading to a change in anesthesiological procedures. Low-flow anesthesia with desflurane can be performed, the technical equipment is available, especially vaporizers and gas analyzers. ⋯ Isoflurane, desflurane or sevoflurane needed the same time for wash-in. Wash-out was slower with isoflurane; however, the technical equipment should be adapted to increase the elimination of the new agents. The consumption of desflurane and sevoflurane is effectively reduced by low-flow and closed circuit anesthesia.