Design of an in-ear EEG device to detect consciousness levels and be used in monitoring anaesthesia levels of a patient in a medical setting

Wessels, Carel (2019-04)

Thesis (MEng)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: There is, as of yet, no feasible and real-time monitor that can accurately determine the level of conciousness experienced by a patient while under some form of general anaesthesia. Existing systems, such as the bispectral indexing (BIS) as well as expiratory vapour measurement techniques such as minimum alveolar concentration (MAC), are both limited in accuracy and in usability. The existing methods use empirical, statistical and historical means to derive at a consciousness indication, rather than a theoretical approach. A system that can accurately monitor levels of anaesthesia (or consciousness) is crucial for eliminating the health risks associated with the overdosing or underdosing of an anaesthetic. Auditory evoked potentials (AEPs) are the brain's electrical responses, measurable using an electroencephalography (EEG) set-up, to auditory stimulus. Such responses give an indication of the neurological pathway that an auditory signal takes from the eardrum to the processing thereof in the frontal cortex. It also provides an indication of the brains ability to process the information throughout the pathway. Changes in these responses, from a less-obtrusive in-ear electrode, could potentially be utilised to detect the brain's consciousness of the auditory signal and, therefore, the overall consciousness of the patient. In the clinical trials completed, a characteristic peak latency, namely Pa, of the AEPs was compared to existing measures of anaesthesia and was shown to remarkably outperform the BIS's ability to perceive consciousness. It also produced a more linear response than the commonly used expiratory values (being an indirect measure) and showed potential for better differentiating between all of the different levels of anaesthesia. The research completed could be instrumental in the development of a baseline consciousness monitor that would be beneficial to the health and safety of anaesthetised patients worldwide.

AFRIKAANSE OPSOMMING: Daar is nog nie 'n monitor ontwikkel wat die vlakke van bewustheid akkuraat en deurlopend kan bepaal wanneer 'n pasiënt 'n algemene narkose prosedure ondergaan nie. Bestaande stelsels, soos die bispektrale indeks (BIS) en ekspirasie dampmetingstegnieke, soos die minimum alveolêre konsentrasie (MAC), is beide beperk in akkuraatheid en bruikbaarheid. Bestaande metodes gebruik empiriese, statistiese en historiese hulpmiddels om 'n bewussynsindikasie te bepaal, eerder as om 'n teoretiese benadering te volg. 'n Stelsel wat akkuraat die vlakke van narkose (bewussyn) kan monitor, is noodsaaklik om die gesondheidsrisiko's wat betrokke is by die oordosering of onderdosering van narkose, uit te skakel. Ouditief-ontlokte potensiale (AEP's) is die brein se elektriese reaksie, meetbaar met behulp van 'n elektro-enfalografiese (EEG) opstelling, na 'n ouditiewe stimulus. Hierdie lesing gee 'n aanduiding van die neurologiese pad wat 'n ouditiewe sein volg vanaf die gestimuleerde oordrom tot waar dit in die frontale korteks van die brein verwerk word. Dit dui ook die brein se vermoë, asook moontlike onvermoë (vertragings), om hierdie inligting neurologies te verwerk aan. Geïnduseerde stimuli, deur gebruik te maak van 'n nieobstruktiewe in-oor-elektrode, kan potensieel aangewend word om die brein se bewussyn van die gehoorsein en dus die algehele bewussyn van die pasiënt te bepaal. In die kliniese proewe wat voltooi is, is 'n pieklatensie, naamlik (Pa), van die AEP's vergelyk met bestaande narkose-maatstawwe. Daar is bevind dat dit opvallend beter presteer as die BIS se vermoë om bewussynvlakke te bepaal. Dit het ook 'n meer lineêre lesing geproduseer as die algemeen gebruikte ekspirasie waardes (wat 'n indirekte maatstaf is) en het potensiaal getoon om al die vlakke van narkose beter te onderskei. Die voltooide navorsing kan instrumenteel wees in die ontwikkeling van 'n basislyn bewussyn monitor, wat voordelig aangewend kan word om die gesondheid en veiligheid van narkose pasiënte wêreldwyd te verseker.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105786
This item appears in the following collections: