波形分析在機(jī)械通氣的應(yīng)用

環(huán)路分析在機(jī)械通氣中的應(yīng)用武警醫(yī)學(xué)院附屬醫(yī)院呼吸科劉陽CriticalinassessingtheMechanicallyVentilatedPatient機(jī)械通氣目的提供足夠的肺泡通氣量（VA）在安全的供氧濃度下達(dá)到適宜的動脈氧分壓胸腔壓升高的情況下避免發(fā)生氣壓病人舒適合適的呼吸肌負(fù)擔(dān)良好的人機(jī)同步

進(jìn)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–ventilatorsynchrony

Eumorfia

Kondili,Nektaria

XirouchakiandDimitris

Georgopoulos.Curr

Opin

Crit Care13:84–89.NilsestuenJOandHargettKD.RespirCare,2005.50(2):p.202-34;discussion232-4. PressureversusTimeInspirationExpirationPaw(cmH2O)Time(sec)}TIPeakInspiratoryPressurePIPPEEPTE Pressure-VolumeLoopControlledAssistedSpontaneousVol(ml)Paw(cmH2O)I:InspirationE:ExpirationIEEEIIFlow-VolumeLoopVolume(ml)PEFRFRCInspirationExpirationFlow(L/min)PIFRVTMechanicalMonitoringAirwayPressuresStaticorPlateauPressure靜態(tài)順應(yīng)性和平臺壓Separatesresistancefromelasticrecoil吸氣末測量Shouldbekept<35cmH2OtoavoidvolutraumaAllowscomputationofstaticcompliance,whichdecreasesasthelungsbecomestiffStaticcompliance=靜態(tài)順應(yīng)性Staticcompliance=定容模式下壓力、流速、容量-時間曲線簡圖NormalCrsisapproximately100mL/cmH2Ointherangeofusualoperationallungvolume.通氣模式為定容thepressureintheventilatorcircuit("inspiratoryplateaupressure")equalstheamountofpressureneededtodistendthelungsandchestwallbytheamountoftidalvolumejustdelivered因此靜態(tài)順應(yīng)性可以表示為Crs=潮氣量/(氣道平臺壓-PEEPi).Staticcompliance=StaticcomplianceCrs,st=肺纖維化的P-V曲線阻力R=P/flowPinPoutflowRPinPoutflowPIPPplat阻力OppositiontoairflowbynonelasticforcesNormally2-5cmH2O/L/sec氣道分泌物增多或者氣道痙攣時會顯著增加對于評價支氣管擴(kuò)張劑的效果十分有用Raw=

Paw(cmH2O)NormalNormalPPlat(NormalCompliance)IncreasedPIP}IncreasedPTA(increasedAirwayResistance)NormalPIPPPlatHighRawPIPPPlatIncreasedAirwayResistanceMeasuredVolumesTidalVolume潮氣量5-7mL/kgIBWVT=VA+VDVD=1mL/lbIBWMechanicaltidalvolumevarieswithdiseaseprocess定容量模式下設(shè)定VT與呼出VT的差值為漏氣量leak:ETTcuffleak PneumothoraxTubingdisconnection 隨著氣道順應(yīng)性的下降，在PCV模式下，VT將出現(xiàn)顯著下降MeasuredVolumesMinuteVentilation(VE)分鐘通氣量VTxf4-8L/minuteVEof6L/minassociatedwithaPaCO2of40mmHgHighPaCO2withahighVEindicatesincreaseddeadspaceorincreasedmetabolism自主呼吸時（T-管實驗）VE>10L/min常常提示撤機(jī)失敗VE,VA,andPaCO2

FlowversusTimeTheflow-timecurvecanbeusedtodetect:WaveformshapeTypeofbreathingPresenceofAuto-PEEP(IntrinsicPEEP)Patient’sresponsetobronchodilatorsAdequacyofinspiratorytimeinpressurecontrolventilationPresenceandrateofcontinuousairleaks判斷流速波形Inspiratoryflowpatternscanvarybasedontheflowwaveformsettingorthesetbreathtypeasillustrated減速波呼氣流速波形在下一個吸氣相開始之前呼氣流速突然回到0,這是由于小氣道在呼氣時過早地關(guān)閉,使部分氣體阻滯在肺泡內(nèi)而引起Auto-PEEP(PEEPi)存在不同類型呼吸下，五種類型的流速-時間曲線評估支氣管擴(kuò)張劑的反應(yīng)effectofinspiratorytimeinpressurecontrolonflowdeliverytothepatient.maybedesirableinsomecases患者對支氣管擴(kuò)張劑的反應(yīng)性BeforeTime(sec)Flow(L/min)PEFRAfterLongTEHigherPEFRShorterTE漏氣對吸呼切換的影響：漏氣會導(dǎo)致吸氣流速下降緩慢，達(dá)不到預(yù)設(shè)的切換標(biāo)準(zhǔn)（setterminationthreshold）吸氣峰流量Tinsp45%15%Thresholdcannotbereachedtheperiodofmechanicalinflationmustmatchtheperiodofneuralinspiratorytime(thedurationofinspiratoryeffort),andtheperiodofmechanicalinactivitymustmatchtheneuralexpiratorytimeWhiletheventilatorwasstillpumpinggasintothepatient,hisexpiratorymuscleswererecruited,causingabumpintheairway-pressurecurve.Thattheflowneverreturnedtozerothroughoutexpirationreflectedthepresenceofauto–positiveend-expiratorypressure.AutoPEEP吸呼切換延遲Delayedterminationpresent患者呼氣肌開始活動時，呼吸機(jī)的吸氣過程還未完成，因此發(fā)生亞臨床的人機(jī)對抗。Notethereisalsoasmallairwaypressurespikeneartheendofmechanicalinflation,whichcoincideswiththepatient’sneuralexpiratoryactivity.切換延遲CycleCriteria?吸氣預(yù)置流速不足Flow

(L/min)Time(sec)NormalAbnormalActiveInspirationorAsynchronyPatient’seffort吸氣預(yù)置流速不足或者患者主動吸氣(SIMV)/volume-limited/pressuresupportapproach“doublebreathing”assistvolumecontrol恒定流速患者持續(xù)吸氣，氣道壓力下降，在呼氣閥打開時，發(fā)生doublebreathingAirTrappingInspirationExpirationNormalPatientTime(sec)Flow(L/min)AirTrappingAuto-PEEP}PRESSURE-TIMECURVESBreathtypedeliveredtothepatientWorkrequiredtotriggerthebreathBreathtiming(inspirationvsexhalation)PressurewaveformshapeAdequacyofinspirationAdequacyofinspiratoryplateauAdequacyofinspiratoryflowResultsandadequacyofastaticmechanicsmaneuverAdequacyoftheRiseTimesettingBreathtypedeliveredtothepatientBreathtypedeliveredtothepatientCMV,withauto-flowonMeasuringStaticMechanics

illustratesastablestaticpressureplateaumeasurementthatdifferentiatesthepressurecausedbyflowthroughthebreathingcircuitandthepressuresrequiredtoinflatethelungs.Thepressure-timecurvecanbeusedtoverifythestabilityoftheplateauwhencalculatingstaticcomplianceandresistance.C代表不穩(wěn)定的氣道平臺壓力，常見原因為漏氣或者患者出現(xiàn)自主吸氣AssessingRiseTime吸氣斜率ChiumelloD,PelosiP,CrociM,etal.,Eur.Respir.J.,2001.18(1):p.107-114.Atherisetopressuremaybetooslow.Bidealwaveform恰當(dāng)?shù)男甭试O(shè)置CArisetimethatistoofast流速不足AdequateFlowInadequateFlowPaw

(cmH2O)Time(sec)InadequateFlow預(yù)置流速不足Thedished-outappearanceoftheairwaypressurewaveformillustratesthechangesfromthepassivebreathwhenflowdoesnotmeetpatientdemand.Progressiveincreasesinpatienteffortduringbreaths2and3werecreatedbymanuallyliftingthetestlungTriggeringdifficultyandunnecessarypatientwork觸發(fā)困難第三次為患者觸發(fā)的通氣，雖然患者觸發(fā)了呼吸機(jī)，但是P-T曲線呈下凹型，顯示了預(yù)制流速不足

第一次呼吸患者未達(dá)到觸發(fā)閾值，但是啟動了按需閥，為時間觸發(fā)；Thesensitivitysettingis–4cmH2O.第二次患者仍打開了按需閥，啟動了自主呼吸，自主呼吸末，時間觸發(fā)了一次同步間歇指令通氣吸氣時的作功大小吸氣做功主要由吸氣負(fù)壓大小和持續(xù)時間長短決定，吸氣負(fù)壓越大和持續(xù)時間越長，吸氣功越大，反之亦然

人機(jī)不同步HewasbeingmechanicallyventilatedandarterialbloodgaseswereacceptableonventilatorsettingsofSIMV12/min,VT850ml,PEEP5cmH2OandFiO20.40.Hethenbecamecombative,requiringsedationandrestraints.TheendtidalCO2hadincreasedfrom42mmHgto48mmHgandarterialoxygensaturationhaddecreasedfrom98%to94%.Hisheartrateincreasedfrom80to110andhisbloodpressureincreasedfrom140/80to180/100.Thephysicianincreasedtheinspiratoryflowrateandventilatorsensitivity.Thepatientimmediatelybecamecalmerandallvitalsignsreturnedtobaselinevalues.無效觸發(fā)Further,ifthepeakflowrateoftheventilatorisinadequate,thentheinspiratoryflowwillbe"scooped"inwards,andthepatientappearstobefightingtheventilator.Ifthenumberoftriggeringepisodesisgreaterthanthenumberofbreaths,thepatientisasynchronouswiththeventilator.Loops–agoodthingallroundP-VloopF-Vloop肺通氣功能測定

一、肺容積(lungvolume)

（一）基本肺容積(basallungvolume)

1.潮氣量(TidalVolume,VT)

2.補吸氣量(InspiratoryReserveVolume,IRV)

3.補呼氣量(ExpiratoryReserveVolume,ERV)

4.殘氣量(ResidualVolumeRV)（二）基本肺容量(basallungcapacity)

1.深吸氣量(InspiratoryCapacityIC)

2.功能殘氣量(FunctionResidualCapacityFRC)

3.肺活量(VitalCapacityVC)

4.肺總量(TotalLungCapacityTLC)靜態(tài)P-V環(huán)橫軸為壓力有正壓(機(jī)械通氣)、負(fù)壓(自主呼吸)之分,縱軸是容積(潮氣量Vt),此環(huán)說明壓力與容積的關(guān)系.一般分為靜態(tài)P-V、動態(tài)P-V曲線，上圖為靜態(tài)P-V環(huán)，因為P-V主要反映呼吸系統(tǒng)順應(yīng)性情況，因此需要去除阻力的影響，而靜態(tài)靜態(tài)P-V曲線是在流速為0的時候測量的，可以滿足此要求。但是在臨床中，這是無法達(dá)到的，因此可以盡量模仿理想狀態(tài)的靜態(tài)環(huán)，一般認(rèn)為流速<9L/min，可以消除呼吸系統(tǒng)由于阻力成分造成的壓力變化，稱之為”quasi-static”[10].HarrisRS.RespirCare,2005.50(1):p.78-98;discussion98-9動態(tài)PV環(huán)ForthisreasonthePVloopdoesnotgiveanaccuratepictureofthecourseofcompliance.Thegreatertheinspiratorybreathinggasflowthegreatertheadditionalpressuregradientandthusthedegreeofinaccuracy.DynamicPVloops的局限性隨著流速的增加，PVloop顯著右移，而且流速越大，由阻力帶來的壓力變化越大，因此越不可信，因此臨床上常規(guī)描記的動態(tài)P-V環(huán)可信性較差、臨床指導(dǎo)意義不大通氣區(qū)間Volume(ml)Pressure(cmH2O)WithlittleornochangeinVTPawrisesNormalAbnormal臨床應(yīng)用中，潮氣量通常根據(jù)理想體重來設(shè)置，以保證通氣量及使VT＞VTD。利用機(jī)控呼吸下的壓力-容量環(huán)可以有助于選擇一個合適的肌控呼吸潮氣量。事實機(jī)上，因為早期流速、環(huán)路順應(yīng)性、漏氣等原因還需要一些額外的容量，新型呼吸機(jī)對于這些因素有一定補償功能。Pressure-VolumeLoopsHighResistance阻力升高

容量控制通氣時，容量恒定，壓力依據(jù)阻力和順應(yīng)性而變化當(dāng)阻力增加時，PIP上升（A-B），PVloops變寬。該種PVloop，稱為滯后steepnessofloopremainsunchangedPressure-VolumeLoops3、HighandLowCompliance——順應(yīng)性容量控制通氣時，順應(yīng)性增加，輸出lowerPIP；順應(yīng)性降低，輸出higherPIPYellowforHighComplianceDecreasedcompliance正常人和ARDS患者PV曲線P-VloopsinARDSaregionoflowcomplianceatlowlungvolume—alowerinflectionpointaregionwithasteeperslopeshowinghighercompliancearegionwithaflatterslope(poorlycompliant)PEEPandPVloopHypotheticalrespiratorysystempressure-volumecurvesforapatientwithARDSshowingaflatterthannormalrelationship(decreasedrespiratorysystemcompliance,Crs=VT/ΔP1).WithadditionofPEEP,ashifttoamorecompliantcurvemayoccursuchthatCrs=VT/(ΔP2-PEEP)increases.ThechangeincompliancemayrepresentrecruitmentofpoorlyventilatedornonventilatedlungunitswithapplicationofPEEPandmaybecorrelatedwithimprovedoxygenationandgasexchange.AirTrappingInspirationExpirationVolume(ml)Flow(L/min)流速未回到基線NormalAbnormalIncreasedRawPressure(cmH2O)HigherPTANormalSlopeVol(mL)LowerSlope氣道阻力升高InspirationExpirationVolume(ml)Flow(L/min)DecreasedPEFRNormalAbnormal“Scoopedout”patternP-Vloop“Scoopedout”pattern呼吸功

A:ResistiveWork

B:ElasticWorkPressure(cmH2O)Volume(ml)BA觸發(fā)靈敏度的設(shè)置不當(dāng)Volume(mL)Paw(cmH2O)IncreasedWOB預(yù)置吸氣流速不足Paw(cmH2O)V