Medical progress through technology
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Use of a closed rebreathing circuit for anesthesia delivery offers several advantages: conservation of anesthetic agent, natural heating and humidification of inspired gases, less pollution, and improved monitoring. However, the technique requires careful control of the fresh gas and anesthetic delivery. An anesthesia delivery system has been developed which automatically controls fresh gas delivery, anesthetic delivery, and ventilation in order to regulate circuit volume, oxygen concentration, end-tidal anesthetic concentration, and end-tidal PCO2. ⋯ No further tuning was required for any of the other patients or controllers. During abdominal surgery, the end-tidal bellows position measurement and end-tidal anesthetic concentration measurement increased in variability. The cause of the variability and its elimination are discussed in the article.