醫(yī)學(xué)-呼氣末二氧化碳在急診的臨床應(yīng)用

北京協(xié)和醫(yī)院急診科談定玉呼氣末二氧化碳監(jiān)測(cè)在急診的臨床應(yīng)用

第六生命體征

概述呼氣末二氧化碳（

end-tidalcarbondioxide，ETCO2)是指呼氣終末期呼出的混合肺泡氣含有的二氧化碳分壓（PETCO2)或濃度（CETCO2)值無(wú)創(chuàng)、連續(xù)、實(shí)時(shí)、簡(jiǎn)便、重要體內(nèi)CO2產(chǎn)量(VCO2)和肺通氣量(VA)決定PACO2PACO2=VCO2×0.863/VA,0.863為氣體容量轉(zhuǎn)換為壓力的系數(shù)正常人PETCO2≈PACO2≈PaCO2（正常通氣血流比例），PETCO2略低于PaCO2

，差值小于5mmHgPETCO2和PaCO2受到

CO2產(chǎn)量、肺泡通氣量和肺血流灌注量影響PETCO2監(jiān)測(cè)的方法質(zhì)譜儀法：反應(yīng)快，能連續(xù)監(jiān)測(cè)，但儀器價(jià)格昂貴，難以在臨床廣泛應(yīng)用比色法：簡(jiǎn)便有用，但精確性欠佳紅外線監(jiān)測(cè)法：

CO2僅對(duì)波長(zhǎng)4.26微米的紅外線才有強(qiáng)烈的吸收作用。流經(jīng)的CO2吸收掉一部分紅外線能量，吸收的多少與CO2濃度成比例關(guān)系。經(jīng)過(guò)微電腦處理獲得PETCO2

。主流型旁流型主流和旁流區(qū)別PETCO2與PaCO2的一致性EbrahimRazi,et.ArchTraumaRes.2012;1(2):58-62.McSwainSD,etal.RespirCare.2010;55(3):288–293.旁流Nonintubatedpatientswithdyspnea(≥18years)inanED38%hadadifferenceof10mmHgormore.ThemeandifferencebetweenthePaCO2andETCO2levelswas8mmHgDelermeS,etal.AmJEmergMed.

2010;28(6):711-4.

正常ETCO2波形正常人的ETCO2

值范圍32-43Ⅰ相：吸氣基線，處于零點(diǎn)，是呼氣的開始部分Ⅱ相：呼氣上升支，為肺泡和無(wú)效腔的混合氣Ⅲ相：呼氣平臺(tái)，呈水平形，是混合肺泡氣Ⅳ相：呼氣下降支，迅速而陡直下降至基線，新鮮氣體進(jìn)入氣道ETCO2觀察指標(biāo)基線：代表吸入CO2濃度高度：代表呼出CO2的濃度形態(tài)：正常CO2波形與不正常波形頻率：反映呼吸頻率節(jié)律：反映呼吸中樞或呼吸機(jī)的設(shè)置影響ETCO2因素機(jī)體因素：影響CO2產(chǎn)生：體溫、代謝、藥物等影響CO2運(yùn)輸：心輸出、肺灌注影響通氣：阻塞性及限制性肺疾病，呼吸頻率通氣血流比例變化設(shè)備因素：呼吸機(jī)設(shè)置、故障，管道脫落、阻塞及漏氣取樣管堵塞，取樣部位及速率ETCO2常見(jiàn)異常波形ETCO2急診應(yīng)用—常見(jiàn)異常波形代謝：體溫降低循環(huán)：全身或肺灌注降低（PE、shock，嚴(yán)重時(shí)會(huì)突然降低）通氣：分鐘通氣量增大，過(guò)度通氣儀器：漏氣、取樣管故障等代謝：體溫升高，寒顫，抽搐循環(huán)：心輸出量增加，輸入碳酸氫鈉，缺血肢體血供恢復(fù)通氣：分鐘通氣量降低，通氣不足儀器：呼吸機(jī)活瓣故障Loss

of

Waveform呼吸驟停窒息人工氣道脫落或阻塞CO2儀器故障采樣管堵塞扭曲HoweTA,etal.JEmergMed.

2011;41(6):581-9.Loss

of

Alveolar

Plateau

支氣管痙攣哮喘AECOPD氣道阻塞痰液呼吸回路的呼氣段阻塞氣管插管或螺紋管部分阻塞或打折sharkfinningElevated

Baseline不完全吸氣或呼氣回路內(nèi)部分重吸入哮喘或者COPD的病人氣體受阻呼氣時(shí)間不足球囊通氣呼氣期或呼吸機(jī)出現(xiàn)故障校準(zhǔn)有誤延長(zhǎng)呼氣時(shí)間EtCO2decreasesasexhalationcontinues,CO2isnotreachingthedetector.

氣囊漏氣tubethatistoosmall自主呼吸恢復(fù)肌松作用消失肺泡死腔增大吸氣流速降低ETCO2急診臨床應(yīng)用ETCO2急診應(yīng)用—心肺復(fù)蘇提示心跳驟停指導(dǎo)復(fù)蘇—按壓質(zhì)量提示ROSC預(yù)后意義按壓深度與ETCO2SheakKR.etal.Resuscitation.

2015;89:149-54.PETCO2突然大于40mmHg提示ROSCETCO2與ROSC2010指南：PETCO2<10mmHg設(shè)法改進(jìn)CPR質(zhì)量復(fù)蘇成功者PETCO2明顯高于復(fù)蘇失敗者PETCO2持續(xù)<10mmHg病死率近100%10mmHg足夠嗎？EtCO2levels>16mmHgweresigni?cantlyassociatedwithsurvivalfromemergencydepartmentresuscitation.Nopatientsurvivedwithalevel<16mmHgHartmannSM,etal.JIntensiveCareMed.2014Apr22.[Epubaheadofprint]ETCO2與預(yù)后Retrospectiveobservationalstudy16542cardiacarrestpatientsadmittedto125AustraliaandNewZealandICUsbetween2000and2011PaCO2<35mmHgwasassociatedwithanincreaseincombinedmortalityandfailuretobedischargedhomeandalowerlikelihoodofdischargehomeforsurvivorsSchneiderAG.Resuscitation.2013;84(7):927-34.

高ETCO2意味著BreathingproblemsbeforearrestBettercompressionsHigherchanceofshockworkingIncreasedchanceofsurvivalReturnofpulsesETCO2急診應(yīng)用—圍插管期監(jiān)測(cè)—插管前及時(shí)識(shí)別呼吸功能異常短時(shí)間內(nèi)準(zhǔn)確判斷呼吸頻率實(shí)時(shí)預(yù)警二氧化碳潴留SeizurepatientswithrespiratoryfailureEtCO2roseto70–99despitemaintainingSPO2>97%on2-4L/minofoxygen.MoresensitivethanpulseoximetryinpredictingatrendtowardrespiratoryfailureAbramoTJ.CritCareMed1997;25:1242–6.提前預(yù)警缺氧132adultsunderwentsedationwithpropofolintheED.Allpatientsreceivedsupplementaloxygenat3L/min.Capnographygaveadvancedwarningforallhypoxicevents(SpO2<93%for15s).Amediantimeof60sdemonstratedcapnographicevidenceofrespiratorydepressionbeforehypoxia.AnnEmergMed.2010;55:258-264.旁流型ETCO2急診應(yīng)用--圍插管期監(jiān)測(cè)—插管時(shí)Esophageal

IntubationETCO2急診應(yīng)用--圍插管期監(jiān)測(cè)—插管后通氣功能監(jiān)測(cè)指導(dǎo)呼吸機(jī)設(shè)置間接反映循環(huán)功能：及時(shí)識(shí)別插管后低血壓等在撤機(jī)中的應(yīng)用Pellis(2005)JTraumaETCO2急診應(yīng)用—休克ETCO2急診應(yīng)用—休克Hypovolemic29.64±11.49Cardiogenic28.60±9.87Septicshock27.81±7.39ETCO2onEDarrivalispositivelycorrelatedwithsystolicanddiastolicBP,MAP,bicarbonate,baseexcessandlactate.AllpatientswhohadETCO2≤12mmHgdiedintheED.Kheng.InternationalJournalofEmergencyMedicine20125:31.ETCO2急診應(yīng)用—容量反應(yīng)性Instableventilatoryandmetabolicconditions,withoutspontaneousbreathingAPLR-inducedincreaseinEtCO2

＞5%predicteda?uid-inducedincreaseinCI＞15%withsensitivityof71%(95%con?denceinterval:48–89%)andspeci?cityof100(82–100)%.IntensiveCareMed(2013)39:93–100ETCO2急診應(yīng)用—肺栓塞ETCO2decreasessecondarytoincreaseindead-spaceventilation.ETCO2≥36mmHghadanoptimalsensitivityandspeci?cityof87.2%and53%,respectively,foridentifyingpatientswithoutPE.Anegativepredicativevalueof96.6%(95%con?denceinterval[CI]92.3-98.5)demonstratesthevalueofthistechnique.Thisincreasedto97.6%(99%CI93.299.2)whencombinedwithaWellsscore≤4HemnesAR,etal.EurRespirJ2010;35:735–41.AVDSf(mmHg)=(PaCO2-PETCO2)/PaCO2ETCO2急診應(yīng)用—肺栓塞TheAVDSfvaluewiththehighestsensitivityandspecificity,whichwasatthesametimestatisticallysignificant,was0.09.TheuseofAVDSfincombinationwithanyoftheseveralscoringsystemsthatevaluateclinicallikelihoodofPEandD-dimerlevelsresultedinhighersensitivityandspecificityratesforthediagnosisofPE.KurtOK,etal.AmJEmergMed.2010;28(4):460-5.

ETCO2急診應(yīng)用—酮癥ETCO2可以持續(xù)實(shí)時(shí)準(zhǔn)確反映PCO2,間接反應(yīng)代謝InitialpHvalueswere7.08,RRwas35breaths/min,EtCO218.6,andvenousPCO220.pHhadimprovedto7.29,RRto22breaths/min,EtCO2to35,andthevenousPCO2to36