波形分析在机械通气的应用-1

环路分析在机械通气中的应用武警医学院附属医院呼吸科刘阳CriticalinassessingtheMechanicallyVentilatedPatient机械通气目的提供足够的肺泡通气量（VA）在安全的供氧浓度下达到适宜的动脉氧分压胸腔压升高的情况下避免发生气压病人舒适合适的呼吸肌负担良好的人机同步进行波形分析的必要性Patient–ventilatordyssynchronyimposesanadditionalburdenontherespiratorysystemandmayincreasethemorbidityofcriticallyillpatients.ThilleAW,RodriguezP,CabelloB,etal.IntensiveCareMed,2006.32(10):p.1515-22.Ignoranceoftheseissuesmaypreventtheventilatorfromachievingitsgoalsandmaycausepatientharm.GeorgopoulosD,PrinianakisG,andKondiliE.IntensiveCareMed,2006.32(1):p.34-47.Inspectionofpressure,flowandvolumewaveformsrepresentsavaluabletoolforthephysiciantorecognizeandtaketheappropriateactiontoimprovepatient–ventilatorsynchronyEumorfiaKondili,NektariaXirouchakiandDimitrisGeorgopoulos.CurrOpinCritCare13:84–89.NilsestuenJOandHargettKD.RespirCare,2005.50(2):p.202-34;discussion232-4.PressureversusTimeInspirationExpirationPaw(cmH2O)Time(sec)}TIPeakInspiratoryPressurePIPPEEPTEPressure-VolumeLoopControlledAssistedSpontaneousVol(ml)Paw(cmH2O)I:InspirationE:ExpirationIEEEIIFlow-VolumeLoopVolume(ml)PEFRFRCInspirationExpirationPIFRVTMechanicalMonitoringComponentsofInflationPressureComponentsofInflationPressureBeginExpirationPaw(cmH2O)Time(sec)BeginInspirationPIPPIPPplateau(Palveolar)TransairwayPressure(PTA)}}ExhalationValveOpensExpirationExpirationInspiratoryPauseAirwayPressuresStaticorPlateauPressure静态顺应性和平台压Separatesresistancefromelasticrecoil吸气末测量Shouldbekept35cmH2OtoavoidvolutraumaAllowscomputationofstaticcompliance,whichdecreasesasthelungsbecomestiffPEEPPplatVtStaticcompliance=静态顺应性PEEPPplatVtStaticcompliance=定容模式下压力、流速、容量-时间曲线简图NormalCrsisapproximately100mL/cmH2Ointherangeofusualoperationallungvolume.通气模式为定容thepressureintheventilatorcircuit(inspiratoryplateaupressure)equalstheamountofpressureneededtodistendthelungsandchestwallbytheamountoftidalvolumejustdelivered因此静态顺应性可以表示为Crs=潮气量/(气道平台压-PEEPi).PEEPPplatVtStaticcompliance=StaticcomplianceCrs,st=PEEPPplatVt肺纤维化的P-V曲线阻力R=P/flowPinPoutflowRPinPoutflowPIPPplat阻力OppositiontoairflowbynonelasticforcesNormally2-5cmH2O/L/sec气道分泌物增多或者气道痉挛时会显著增加对于评价支气管扩张剂的效果十分有用flowPplatPpeakRaw=Paw(cmH2O)NormalNormalPPlat(NormalCompliance)IncreasedPIP}IncreasedPTA(increasedAirwayResistance)NormalPIPPPlatHighRawPIPPPlatIncreasedAirwayResistanceMeasuredVolumesTidalVolume潮气量5-7mL/kgIBWVT=VA+VDVD=1mL/lbIBWMechanicaltidalvolumevarieswithdiseaseprocess定容量模式下设定VT与呼出VT的差值为漏气量leak:ETTcuffleakPneumothoraxTubingdisconnection随着气道顺应性的下降，在PCV模式下，VT将出现显著下降MeasuredVolumesMinuteVentilation(VE)分钟通气量VTxf4-8L/minuteVEof6L/minassociatedwithaPaCO2of40mmHgHighPaCO2withahighVEindicatesincreaseddeadspaceorincreasedmetabolism自主呼吸时（T-管实验）VE10L/min常常提示撤机失败VE,VA,andPaCO2800)VAVCO2(PCO2VDVTfVDVEVA222PaCOPECOPaCOVTVDFlowversusTimeTheflow-timecurvecanbeusedtodetect:WaveformshapeTypeofbreathingPresenceofAuto-PEEP(IntrinsicPEEP)Patient’sresponsetobronchodilatorsAdequacyofinspiratorytimeinpressurecontrolventilationPresenceandrateofcontinuousairleaks判断流速波形Inspiratoryflowpatternscanvarybasedontheflowwaveformsettingorthesetbreathtypeasillustrated减速波呼气流速波形在下一个吸气相开始之前呼气流速突然回到0,这是由于小气道在呼气时过早地关闭,使部分气体阻滞在肺泡内而引起Auto-PEEP(PEEPi)存在不同类型呼吸下，五种类型的流速-时间曲线评估支气管扩张剂的反应effectofinspiratorytimeinpressurecontrolonflowdeliverytothepatient.maybedesirableinsomecases患者对支气管扩张剂的反应性BeforeTime(sec)Flow(L/min)PEFRAfterLongTEHigherPEFRShorterTE漏气对吸呼切换的影响：漏气会导致吸气流速下降缓慢，达不到预设的切换标准（setterminationthreshold）吸气峰流量Tinsp45%15%Thresholdcannotbereachedtheperiodofmechanicalinflationmustmatchtheperiodofneuralinspiratorytime(thedurationofinspiratoryeffort),andtheperiodofmechanicalinactivitymustmatchtheneuralexpiratorytimeWhiletheventilatorwasstillpumpinggasintothepatient,hisexpiratorymuscleswererecruited,causingabumpintheairway-pressurecurve.Thattheflowneverreturnedtozerothroughoutexpirationreflectedthepresenceofauto–positiveend-expiratorypressure.AutoPEEP吸呼切换延迟Delayedterminationpresent患者呼气肌开始活动时，呼吸机的吸气过程还未完成，因此发生亚临床的人机对抗。Notethereisalsoasmallairwaypressurespikeneartheendofmechanicalinflation,whichcoincideswiththepatient’sneuralexpiratoryactivity.切换延迟CycleCriteria?吸气预置流速不足Flow(L/min)Time(sec)NormalAbnormalActiveInspirationorAsynchronyPatient’seffort吸气预置流速不足或者患者主动吸气(SIMV)/volume-limited/pressuresupportapproach“doublebreathing”assistvolumecontrol恒定流速患者持续吸气，气道压力下降，在呼气阀打开时，发生doublebreathingAirTrappingInspirationExpirationNormalPatientTime(sec)Flow(L/min)AirTrappingAuto-PEEP}PRESSURE-TIMECURVESBreathtypedeliveredtothepatientWorkrequiredtotriggerthebreathBreathtiming(inspirationvsexhalation)PressurewaveformshapeAdequacyofinspirationAdequacyofinspiratoryplateauAdequacyofinspiratoryflowResultsandadequacyofastaticmechanicsmaneuverAdequacyoftheRiseTimesettingBreathtypedeliveredtothepatientBreathtypedeliveredtothepatientCMV,withauto-flowonMeasuringStaticMechanicsillustratesastablestaticpressureplateaumeasurementthatdifferentiatesthepressurecausedbyflowthroughthebreathingcircuitandthepressuresrequiredtoinflatethelungs.Thepressure-timecurvecanbeusedtoverifythestabilityoftheplateauwhencalcu