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Can you hear me?

You may have heard stories of people waking up during operations and not being able to speak. Well, apparently people wake up during operations rather more frequently than we would wish to know. Three years ago, Dr Bill Fitzgerald in the Signal Processing Group was contacted by Professor J Gareth Jones, the University’s first Professor of Anaesthesia, for help with this particular problem. What is required is some consistent measure of awareness so that anaesthetists can take appropriate action. Some work has already been carried out looking at evoked responses in the brain. For instance, it has been found that, if an audio signal such as a click is played to the patient under anaesthetic, the brain’s response to that signal will vary depending on the level of consciousness. A method of extracting this signal response from the background noise has already been established and preliminary trials on volunteers (usually anaesthetists) indicate that a consistent measure of awareness exists. Further clinical trials are now under way to evaluate data obtained from actual patients in the operating theatre.

This machine has finally proved what we always suspected – ten pints of lager and he has the same brain activity as an anaesthetised white mouse.

There are indications that an evoked response from an audio signal is not necessarily required and that changes in conventional EEG readings (the voltage waveforms measured from electrodes to the scalp) may themselves be sufficient to monitor awareness. A more sophisticated technique based on these changes is currently being developed. Such a technique would prove attractive since taking measurements from the scalp is logistically straightforward and totally passive. Watch out for further news as this work progresses.

For further information, please contact Dr Bill Fitzgerald, on (01223) 332719.

number 5, summer '96 back | contents | previous | next