IMPLEMENTATION OF A PULSE OXIMETER ADAPTED TO SHORT-TIME MEASUREMENTS

V diplomskem delu predstavljamo izvedbo pulznega oksimetra z možnostjo kratkotrajnih meritev arterijske oksigenacije. V uvodnih poglavjih predstavljamo pulzno oksimetrijo in njeno zgodovino. Podamo tudi zahteve za nemoteče in kratkotrajne meritve pulzne oksimetrije. Osrednji del diplomskega dela je posvečen opisu lastnih rešitev in eksperimentom, ki smo jih opravili. Strojni del pulznih oksimetrov smo rešili modularno s pomočjo dveh fotopletizmografskih (PPG) tipal ter modula s svetili treh različnih valovnih dolžin, ki ga je mogoče uporabiti z obema tipaloma. Tipali se razlikujeta predvsem v obliki, in sicer je eno točkovno, drugo tipalo pa je linijsko. Oksigenacijo smo računali s pomočjo konvencionalnega algoritma, ki temelji na Beer-Lambertovem zakonu, ki podaja povezavo med absorpcijo svetlobe ter lastnostmi snovi, skozi katero svetloba potuje. Opisujemo tudi algoritem DST, ki za računanje oksigenacije uporablja drugačni model, kot ga opisuje Beer-Lambertov zakon. Opravili smo različne eksperimente. S prvo skupino eksperimentov smo ugotavljali primernost razvite strojne opreme za zajem PPG-signalov. Z drugo skupino eksperimentov smo pridobili množico PPG-signalov, ki smo jih zajeli s pomočjo petih oseb. S temi signali smo izvedli študijo kratkotrajnih meritev, katere izsledke podajamo v zadnjih poglavjih diplomskega dela.In this thesis we present an implementation of a pulse oximeter adapted to short-time measurements of arterial oxygenation. Pulse oxymetry and its history is explained and introduced in initial chapters. Requirements for undisturbed and short-time measurements of pulse oximetry are also given. The central part of our thesis is dedicated to a description of our own methods and experiments done. The hardware of pulse oximeters is made in a modular way using two photoplethymographic (PPG) sensors and an illumination module with light sources of three different wavelengths which can be used with both PPG sensors. PPG sensors differ mostly in shape: one is a spot sensor while another is linear. Oxygenation was calculated using a conventional algorithm based on the Beer-Lambert law which relates the absorption of light to the properties of the material through which the light travels. Also explained is a DST algorithm which uses a model to calculate oxygenation that is different to a model described with the Beer-Lambert law. Different experiments were conducted. The first set of experiments was done to assess the suitability of the developed hardware for use in pulse oximetry. The second set of experiments was done to gain a number of PPG signals captured with the help of five volunteers. The captured signals were used to study the effects of short-time measurements. Results of this study are given in final chapters of the thesis