Low blood oxygen saturation quantification in human arterial and venous circulation

Schoevers, Jacobus Engelbertus (2008-03)

Thesis (MScIng)--Stellenbosch University, 2008.

Thesis

ENGLISH ABSTRACT: Conventional pulse oximetry has limited accuracy in measuring blood oxygen saturation in low saturation and perfusion scenarios. This limits the application of pulse oximetry in patients su ering from peripheral vascular a ictions. A novel pulse oximetry system is presented in this study which proposes solutions to these low saturation and perfusion issues. The presented system was designed to overcome the low perfusion issues by inducing an arti cial pulse in the detected photoplethysmograph. A novel arterio-venous hypothesis was formulated to extract arterial and venous saturation data from this arti cial photoplethysmograph using arterial-to-venous compliance ratios. Sensor wavelengths were selected to provide high and low saturation accuracy, followed by an in vitro sensor calibration procedure. System performance was validated by means of in vivo human studies. In vivo results indicate good accuracy for high saturation, with limited accuracy in low saturation scenarios. The arterio-venous hypothesis was validated, indicating that venous saturation information can be extracted from the arti cial PPG. Although inconclusive, results indicate that the proposed system might be able to accurately monitor arterial and venous saturation in severe hypoperfusion scenarios with recommended hardware and calibration modi cations. It is recommended that further studies into the presented system's performance are conducted.

AFRIKAANSE OPSOMMING: Konvensionele 'pulse oximetry' sisteme het beperkte akkuraatheid tydens die meting van bloed suurstof saturasie in lae saturasie en perfusie gevalle. Dit beperk die bruikbaarheid van 'pulse oximetry' in pasiënte wat ly aan perifere vaskulêre siektes. 'n Nuwe 'pulse oximetry' sisteem, wat oplossings vir hierdie lae saturasie en perfusie beperkings voorstel, word in hierdie studie aangebied. Die voorgestelde sisteem is ontwerp om die lae perfusie beperkings te oorkom deur 'n kunsmatige polsslag in die 'photoplethysmograph' te induseer. 'n Nuwe arterio-veneuse hipotese is geformuleer om arteriële en veneuse saturasie inligting uit hierdie kunsmatige polsslag te onttrek deur middel van 'n arteriële-teenoor-veneuse styfheids verhouding. Die gol engtes wat gebruik is in die sensors, is spesi ek gekies om hoë en lae saturasie akkuraatheid te verskaf. 'n In vitro kalibrasie prosedure is gevolg om die sensors vir hoë en lae saturasie te kalibreer, waarna die werkverrigting van die sisteem getoets is deur middel van 'n in vivo validasie prosedure. Die in vivo resultate toon goeie akkuraatheid vir hoë saturasie, met beperkte akkuraatheid vir lae saturasie. Die arterio-veneuse hipotese is gevalideer, wat aandui dat veneuse saturasie wel uit die kunsmatige 'photoplethysmograph' onttrek kan word. Alhoewel die resultate wat in hierdie studie aangebied word nie omvattend of beslissend is nie, dui dit egter aan dat die voorgestelde sisteem dalk in staat kan wees om arteriële en veneuse saturasie in uiters lae perfusie gevalle te meet. Verbeteringe sal egter aan die sisteem aangebring moet word in terme van hardeware en kalibrasie, om 'n meer gestandardiseerde metings metode te verseker. Verdere navorsing oor die werkverrigting van die voorgestelde sisteem word ook voorgestel.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/21460
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