978-1-4244-6497-5/10/$26.00©2010IEEE137620103rdInternationalConferenceonBiomedicalEngineeringandInformatics(BMEI2010)ADesignofNoninvasiveTesterofHumanArterialOxygenSaturationWangYongqing，ZhangZhipeng，WangHongrui，LiuXiuling,SunRongxia(CollegeofElectronic&InformationalEngineering,HebeiUniversity,HebeiBaoding,071002)Abstract-Thetestingcircuitofbodynoninvasivearterialoxygensaturationisdesignedaccordingtothecharacteristicsthatthelightabsorptionofarterialbloodvarieswithpulse.Thedrivingcircuitoftestingsourceandanti-RossicircuitofcompoundsignalarecontrolledbyDSPsequencesignal,andthesendingofthetestingsignalissynchronouswiththeseparation-receivingsignal.Thehighfrequencyinterferenceofthestraylightisattenuatedadoptingsecond-orderlowpassfilterofvoltagecontrolsource.Theconstantsegmentandpulsatingquantityisextractedrespectivelyfromthecompoundsignalsbytheanti-Rossicircuitofcompoundsignal,second-orderhighpassfilterandsecondarylow-passfilter.ThereversephasecircuitandACsignalamplifyingcircuitisusedrespectivelyforbenefitingADsamplingandraisingthetestingprecision.AwaytoemploymovingaveragemethodtoeliminatenoiseoftheoxyhemoglobinACsignalisproposed,whichhasraisedthetestingaccuracy.Keywords-arterialoxygensaturation;noninvasive;testing;oxygensaturationcompoundsignal;movingaveragemethodI.INTRODUCTIONThearterialoxygensaturationisaimportantindexwhichestimateswhetherhumanbodycirculatorysystemandtherespiratorysystemappearshandicap[1].Thebloodflowsthroughthelungsintheperiodicdiastoleandsystole.Acertainamountofreducedhemoglobininbloodiscombinedwithoxygeninthealveolus,thusbecominghematoglobulin.Theoxygeniscarriedintocapillaryvessel,andthentheoxygenisreleasedforprovidingmetabolismofthecelltissuewithenergy.Atpresent,themeasurementmethodofarterialoxygensaturationisdividedintoinvasivemeasureandnoninvasivemeasure.Becauseintheinvasivemeasurethetestingresultlackstimeliness,causingsufferingtopatienteasily,andtheoperationmethodistoocomplicated.Sothenoninvasivemeasure,whichcharacterizedbycontinuityorreal-timeorsafety,graduallyreplacestheinvasivemeasure.II.MeasuringPrincipleofArterialOxygenSaturationThenoninvasivetesterofarterialoxygensaturationisdesignedaccordingtothecharacteristicsthatthelightabsorptionofarterialbloodvarieswithpulse.Becausethearterialpulseswaspresentperiodically.Thelightabsorptionspectrumofarterialbloodisapulsatingchange,whichiscalledpulsecomponent(namelyACsignal△I).Whenthesystoleispresented,themostbloodvolumeispresented,andtheminimummeasuringlightintensityisshown.Whenthediastoleispresented,theminimumbloodvolumeispresented,andthemostmeasuringlightintensityisshown.Butthelightabsorptionintensityisregardedasaconstantcomponent(namelyDCsignalI)byotherhumantissue,suchasvenousbloodormuscleorcutis.Asshowninfigure1.Figure1.AbsorptionCurveoftheRaybyHumanTissueThearterialoxygensaturationmeansthepercentofthecontentofthehematoglobulininthecontentofallincorporableoxygenintheblood[2],namely:%10022×+=HbHbOHbOCCCS（1）Whenthelightofspecialwavelengthsirradiatesthetestingbodypart,accordingtotheLambert-Beerlaw,andthelightabsorptionintensityismainlyrelatedtothecontentofhaemoglobinintheblood[3],theintensityofthetransmittedthemeasuringlightintensityIDCImaxIminIAC1377lightthroughthetestingbodypartisLCLCLCDCHbHbHbOHbOeeeIIεεε−−−••=22000(2)Amongwhich,TheincidentlightintensityisI0.Thetotalabsorptioncoeffici...
