Commercial testing of a physiologically based theory of oscillatory brain electrical activity in anaesthesia monitoring

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While the mechanisms of local anaesthesia are comparatively well known, the mechanisms whereby anaesthetics impair consciousness remain unresolved. This lack of understanding has implications in our ability to monitor the level of anaesthesia while anaesthetic consumption and side effects are minimized. Despite this a number of devices have been developed that attempt to monitor the depth of anaesthesia by quantifying the brains electrical activity. All monitors analyse the activity using a set of criteria that have been developed by trial and error. The research of Dr David Liley and his team, at Swinburne University of Technology, has resulted in a detailed understanding of the physiological mechanisms that generate brain electrical activity. The outcome is a practical means to carry out a System Based Analysis of Brain Electrical Response (SABER). In 2004, Dr Liley began working with Cortical Dynamics, a company involved in the commercialisation of medical devices. This collaboration incorporated the SABER system into a new prototype device called the Brain Anaesthesia Response (BAR) monitor. In 2004 Dr Liley and Associate Professor Kate Leslie collaborated in a trial, at the Royal Melbourne Hospital to test the sensitivity of the SABER system in quantifying the effect that various levels of nitrous oxide have on measures of anaesthetic depth. The Australian and New Zealand College of Anaesthetists supported this study. Initial results obtained with sevoflurane and 3 levels of nitrous oxide showed the ability to differentiate between conscious and unconscious states of patients based on two physiological characterizations of higher brain dynamic state. The next step requires commercial product validation (ie scale up) and further clinical efficacy in testing beta stage depth of anaesthesia BAR units. Completion of this will help the technology move away from a low volume prototype system into a commercially applicable device.