The pharmacokinetic properties of desflurane, resulting in especially low individual uptake, and the wide output range of the vaporizer facilitate the use of low-flow anesthetic techniques in routine clinical practice. Even in minimal-flow anesthesia, the duration of the initial high-flow phase can be shortened to min. If the flow is reduced to 1 l/min, the inspired desflurane concentration achieved in the initial high-flow phase can be maintained without any alteration of the vaporizer setting. In minimal-flow anesthesia, however, with flow reduction to 0.5 l/min, the fresh gas concentration has to be increased to a value 1%-2% higher than the inspired nominal value. Due to the wide dialing range of the desflurane vaporizer, the amount of vapour delivered into the breathing system can be increased to about 110 ml/min even at a flow of 0.5 l/min. The large amount of agent that can be delivered into the system even under low-flow conditions, together with the very low individual uptake, results in a time-constant that is sufficient short for the clinically required rapid increase in inspired desflurane concentrations. The short time-constant of low-flow desflurane anaesthesia improves the control of the anaesthetic concentration. If all measures are taken to safely avoid inadvertent drying out of the soda lime, there is no evidence that low-flow anaesthesia with desflurane is liable to increase the risk of accidental carbon monoxide poisoning. (ABSTRACT TRUNCATED)
An approach to generating 'intelligent alarms' is presented that aggregates many information items, i.e. measured vital signs, recent medications, etc., into state variables that more directly reflect the patient's physiological state. Based on these state variables the described decision support system AES-2 also provides therapy recommendations. The assessment of the state variables and the generation of therapeutic advice follow a knowledge-based approach. Aspects of uncertainty, e.g. a gradual transition between 'normal' and 'below normal', are considered applying a fuzzy set approach. Special emphasis is laid on the ergonomic design of the user interface, which is based on color graphics and finger touch input on the screen. Certain simulation techniques considerably support the design process of AES-2 as is demonstrated with a typical example from cardioanesthesia.
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