Quantitative Anaesthesia with the Help of Closed-Loop Control

  • D. R. Westenskow
  • P. J. Loughlin
Part of the Anaesthesiologie und Intensivmedizin / Anaesthesiology and Intensive Care Medicine book series (A+I, volume 204)

Abstract

Closed-loop control systems have been used since the time of the Babylonians, when irrigation systems were opened and closed in closed-loop control mode [1]. Closed-loop control in anaesthesia began in 1950 when Bickford used the EEG signal to control the infusion of thiopental [2]. A syringe with thiopental was attached to a stepper motor. Each time the EEG crossed zero, a bolus of thiopental was given. As the patient became anaesthesized the infusion rate slowed because the frequency of the EEG decreased. Closed-loop control has adjusted ventilation during anaesthesia by comparing the difference between the desired and a measured end-tidal carbon dioxide concentration [3]. If the CO2 was high, the inspiratory airway pressure was incremented in 0.1-mm steps. When the end-tidal reached the desired level, the airway pressure was held constant. The most common application of closed-loop control is the maintenance of arterial blood pressure by the infusion of sodium nitroprusside [4]. Experience has shown that a desired end-tidal anaesthetic orblood pressure is maintained more consistently andmore accurately under closed-loop control than is done manually [5]. Closed-loop control can perform some very usedful and helpful tasks when it is made available in the anaesthesia machine design.

Keywords

Dioxide Dopamine Respiration Syringe Hull 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1989

Authors and Affiliations

  • D. R. Westenskow
  • P. J. Loughlin

There are no affiliations available

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