Closed-loop control of anaesthesia

Rights statement
Awarding institution
  • University of Strathclyde
Date of award
  • 1996
Thesis identifier
  • T8819
Qualification Level
Qualification Name
Department, School or Faculty
  • One of the most challenging problems in modern Anaesthesia is measuring anaesthetic depth. Before the advent of muscle relaxant drugs, anaesthetists relied on respiratory patterns and movement in response to painful stimuli to titrate anaesthetic concentrations and ensure that their patients were adequately anaesthetised. The introduction of muscle relaxation rendered traditional signs of anaesthetic depth unusable and, as a result, a small percentage of the general surgical population experience conscIous awareness with or without pain under general anaesthesia. Several attempts have been made to develop an objective monitor that would work with all anaesthetic agents and be adequately reliable and robust for use in the operating theatre environment. Most of these attempts failed, the main reason being that no satisfactory measuring parameter could be identified. The most promising area of research has been centred around Auditory Evoked Potentials in determining anaesthetic depth. This thesis describes the development of a novel technique, using Auditory Evoked Potentials to extract a single numerical index which unequivocally measures depth of anaesthesia. In order to prove this index, it has been used as an input signal to a closed-loop control system. This system has been successfully employed to deliver an intravenous anaesthetic to a large number of patients completely automatically. Further refinements to both software and hardware and additional clinical studies, using various anaesthetic agents, are required. It is proposed that this technique will lead to the development of a commercial depth of anaesthesia monitor.
Resource Type