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Development of a vital signs monitoring ear probe.

Bestbier, Andre (2017-12)

Thesis (MEng)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: The need exists for a mobile and unobtrusive way to continuously monitor vital signs in everyday life. Wearable devices are rapidly advancing in terms of technology,functionality,andsize,with more real-time applications becoming available everyday. This thesis investigates the external ear as a novel location for a wearable device. The ear allows for the monitoring of multiple vital signs from one location, making the device an ideal mobile solution for non-clinical applications, without compromising the quality of life of the wearer. An application example is the monitoring off infants at home for sudden infant death syndrome risk factors. The main purpose of the device is to measure vital signs ,including core temperature ,heart rate, respiratory rate and blood oxygen saturation (SpO2). The device transmits collected data through a wireless connection to a computer for analyses and storage. A proof of concept, called the Ear-monitor, was designed and built. It consists of a silicone ear probe with embedded sensors connected to aheadband containing a micro controller, battery, and Bluetooth modem. A trial was conducted in which the Ear-Monitor was tested on a group of 16 participants. Measurements were compared to benchmark measurements recorded by commercially available devices. The following results were obtained :core temperature was measured with a mean error of 0.02 ± 0:52 °C through an infrared sensor pointed at the tympanic membrane. Heart rate was determined through an infrared photoplethysmogram measured from the ear canal wall. A beat detection algorithm identifies heart beats and heart rate was calculated with a mean error of 0.03 ± 0.72 beats per minute. Respiratory rate was determined through analysing respiratory sinus arrhythmia. The respiratory rate was measured with a mean error of-0.56 ±1.41 breathsperminute. Finally,SpO2 was measured through pulse oximetry conducted against the ear canal wall. The different absorption spectra of oxygenated and deoxygenated blood were used to calculate the percentage oxygen saturation of blood in peripheral blood vessels with a mean error of-0.22 ±1.50%. All measurements showed statistically significant correlation with the irrespective benchmark measurements (p<0.05), except for SpO2. The latter is due to the absence of measurable SpO2 variations in healthy individuals during the trial. It is concluded that the external ear is a suitable location for measuring core temperature, heart rate, and respiratory rate. Further testing is needed to evaluate the SpO2 measurement capabilities of the device. This thesis produced valuable insights into the feasibility of measuring multiplevital signs through the external ear and lays the foundation towards a commercial version of the Ear-Monitor.

AFRIKAANSE OPSOMMING: Daar is ’n konstante behoefte na ’n mobiele en onopvallende manier om vitale parameters in die alledaagse lewe te monitor. Draagbare toestelle ontwikkel teen ’n hoë tempo interme van tegnologie, funksionaliteit en grootte,met meer intydse toepassings elke dag. Hierdie tesis ondersoek die eksterne oor as ’n alternatiewe ligging vir ’n draagbare toestel. Die ligging maak dit moontlik om verskeie vitale parameters vanaf een posisie te meet. Verder dien dit ook as ideale mobiele oplossing in nie-kliniese situasies, sonder om die lewensgehalte van die draer in gedrang te bring. ’n Voorbeeld van toepassing is die monitering van babas by die huis vir skielike infantiedood sindroom risiko faktore. Die hoofdoel van hierdie toestel is om vitale parameters,i nsluitend kerntem-peratuur, hartklop, respiratoriese tempo en bloed suurstofversadiging (SpO2) te meet. Die toestel stuur versamelde data deur ’n draadlose verbinding na ’n rekenaar vir analiese en berging. ’n Bewys van konsep,genaamd die Ear-Monitor, was ontwerp en gebou. Dit bestaan uit ’n silikoon oorprop met ingeboude sensors wat aan ’n kopband gekoppel is. Die kopband bevat ’n mikrokontrolleerder, battery en Bluetooth- modem. ’n Eksperiment is uitgevoer waarin die Ear-Monitor op ’ngroepvan 16 individue getoets was. Metings is vergelyk met maatstafmetings, wat deur kommersiële toestelle opgeneem is. Die volgende resultate was verkry: kerntemperatuur was gemeet met ’n gemiddelde foutsyfer van 0.02 ±0:52 °C deur ’ninfrarooi sensor wat op die tympaniese membraan gerig is. Hart tempo was bepaal deur ’n infrarooi fo-toplethysmogram gemeet vanaf die oorkanaalmuu . ’ n Klopdeteksie-algoritme identifiseer hartkloppe en die hart tempo was bereken met ’n gemiddelde fout-syfer van 0.03 ±0.72 slae per minuut. Respiratoriese tempo was bepaal deur die ontleding van respiratoriese sinus-aritmie. Respiratoriese tempo was ge-meet met ’n gemiddelde foutsyfer van-0.56 ± 1.41 asemhalings per minuut. Laastens, was SpO2 gemeet deur middel van polsoksimetrie wat teen die oor-kanaalmuur uitgevoer word. Die verskillende absorpsiespektra van geoksige- neerde en gedeoksigeneerde bloed word gebruik om die persentasie suurstof- versadiging van bloed in perifere bloedvate te bereken. Dit het gelei tot ’n gemiddelde foutsyfer van-0.22 ±1.50%. Die statistiese ontleding van die resultate dui aan dat ’n definitiewe korre-lasie gevind is tussen die mates (p<0.05), behalwe vir SpO2. Laasgenoemde is as gevolg van die afwesigheid van meetbare SpO2-variasies in gesonde in-dividue tydens die eksperiment. Die huidige bewyse ondersteun die gebruik van die eksterne oor om kerntemperatuur, hartklop en respiratoriese tempo te meet. Addisionele toetsing is nodig om die SpO2 metingsvermoë van die toestel te evalueer. Hierdie tesis het waardevolle insig gelewer in die lewens-vatbaarheid van die meet van verskeie vitale parameters in die eksterne oor en lê die grondslag vir’n kommersiële weergawe van die Ear-Monitor.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/102943
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