医学-呼气末二氧化碳在急诊的临床应用

北京协和医院急诊科谈定玉呼气末二氧化碳监测在急诊的临床应用

第六生命体征

概述呼气末二氧化碳（

end-tidalcarbondioxide，ETCO2)是指呼气终末期呼出的混合肺泡气含有的二氧化碳分压（PETCO2)或浓度（CETCO2)值无创、连续、实时、简便、重要体内CO2产量(VCO2)和肺通气量(VA)决定PACO2PACO2=VCO2×0.863/VA,0.863为气体容量转换为压力的系数正常人PETCO2≈PACO2≈PaCO2（正常通气血流比例），PETCO2略低于PaCO2

，差值小于5mmHgPETCO2和PaCO2受到

CO2产量、肺泡通气量和肺血流灌注量影响PETCO2监测的方法质谱仪法：反应快，能连续监测，但仪器价格昂贵，难以在临床广泛应用比色法：简便有用，但精确性欠佳红外线监测法：

CO2仅对波长4.26微米的红外线才有强烈的吸收作用。流经的CO2吸收掉一部分红外线能量，吸收的多少与CO2浓度成比例关系。经过微电脑处理获得PETCO2

。主流型旁流型主流和旁流区别PETCO2与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

值范围32-43Ⅰ相：吸气基线，处于零点，是呼气的开始部分Ⅱ相：呼气上升支，为肺泡和无效腔的混合气Ⅲ相：呼气平台，呈水平形，是混合肺泡气Ⅳ相：呼气下降支，迅速而陡直下降至基线，新鲜气体进入气道ETCO2观察指标基线：代表吸入CO2浓度高度：代表呼出CO2的浓度形态：正常CO2波形与不正常波形频率：反映呼吸频率节律：反映呼吸中枢或呼吸机的设置影响ETCO2因素机体因素：影响CO2产生：体温、代谢、药物等影响CO2运输：心输出、肺灌注影响通气：阻塞性及限制性肺疾病，呼吸频率通气血流比例变化设备因素：呼吸机设置、故障，管道脱落、阻塞及漏气取样管堵塞，取样部位及速率ETCO2常见异常波形ETCO2急诊应用—常见异常波形代谢：体温降低循环：全身或肺灌注降低（PE、shock，严重时会突然降低）通气：分钟通气量增大，过度通气仪器：漏气、取样管故障等代谢：体温升高，寒颤，抽搐循环：心输出量增加，输入碳酸氢钠，缺血肢体血供恢复通气：分钟通气量降低，通气不足仪器：呼吸机活瓣故障Loss

of

Waveform呼吸骤停窒息人工气道脱落或阻塞CO2仪器故障采样管堵塞扭曲HoweTA,etal.JEmergMed.

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

of

Alveolar

Plateau

支气管痉挛哮喘AECOPD气道阻塞痰液呼吸回路的呼气段阻塞气管插管或螺纹管部分阻塞或打折sharkfinningElevated

Baseline不完全吸气或呼气回路内部分重吸入哮喘或者COPD的病人气体受阻呼气时间不足球囊通气呼气期或呼吸机出现故障校准有误延长呼气时间EtCO2decreasesasexhalationcontinues,CO2isnotreachingthedetector.

气囊漏气tubethatistoosmall自主呼吸恢复肌松作用消失肺泡死腔增大吸气流速降低ETCO2急诊临床应用ETCO2急诊应用—心肺复苏提示心跳骤停指导复苏—按压质量提示ROSC预后意义按压深度与ETCO2SheakKR.etal.Resuscitation.

2015;89:149-54.PETCO2突然大于40mmHg提示ROSCETCO2与ROSC2010指南：PETCO2<10mmHg设法改进CPR质量复苏成功者PETCO2明显高于复苏失败者PETCO2持续<10mmHg病死率近100%10mmHg足够吗？EtCO2levels>16mmHgweresignificantlyassociatedwithsurvivalfromemergencydepartmentresuscitation.Nopatientsurvivedwithalevel<16mmHgHartmannSM,etal.JIntensiveCareMed.2014Apr22.[Epubaheadofprint]ETCO2与预后Retrospectiveobservationalstudy16542cardiacarrestpatientsadmittedto125AustraliaandNewZealandICUsbetween2000and2011PaCO2<35mmHgwasassociatedwithanincreaseincombinedmortalityandfailuretobedischargedhomeandalowerlikelihoodofdischargehomeforsurvivorsSchneiderAG.Resuscitation.2013;84(7):927-34.

高ETCO2意味着BreathingproblemsbeforearrestBettercompressionsHigherchanceofshockworkingIncreasedchanceofsurvivalReturnofpulsesETCO2急诊应用—围插管期监测—插管前及时识别呼吸功能异常短时间内准确判断呼吸频率实时预警二氧化碳潴留SeizurepatientswithrespiratoryfailureEtCO2roseto70–99despitemaintainingSPO2>97%on2-4L/minofoxygen.MoresensitivethanpulseoximetryinpredictingatrendtowardrespiratoryfailureAbramoTJ.CritCareMed1997;25:1242–6.提前预警缺氧132adultsunderwentsedationwithpropofolintheED.Allpatientsreceivedsupplementaloxygenat3L/min.Capnographygaveadvancedwarningforallhypoxicevents(SpO2<93%for15s).Amediantimeof60sdemonstratedcapnographicevidenceofrespiratorydepressionbeforehypoxia.AnnEmergMed.2010;55:258-264.旁流型ETCO2急诊应用--围插管期监测—插管时Esophageal

IntubationETCO2急诊应用--围插管期监测—插管后通气功能监测指导呼吸机设置间接反映循环功能：及时识别插管后低血压等在撤机中的应用Pellis(2005)JTraumaETCO2急诊应用—休克ETCO2急诊应用—休克Hypovolemic29.64±11.49Cardiogenic28.60±9.87Septicshock27.81±7.39ETCO2onEDarrivalispositivelycorrelatedwithsystolicanddiastolicBP,MAP,bicarbonate,baseexcessandlactate.AllpatientswhohadETCO2≤12mmHgdiedintheED.Kheng.InternationalJournalofEmergencyMedicine20125:31.ETCO2急诊应用—容量反应性Instableventilatoryandmetabolicconditions,withoutspontaneousbreathingAPLR-inducedincreaseinEtCO2

＞5%predictedafluid-inducedincreaseinCI＞15%withsensitivityof71%(95%confidenceinterval:48–89%)andspecificityof100(82–100)%.IntensiveCareMed(2013)39:93–100ETCO2急诊应用—肺栓塞ETCO2decreasessecondarytoincreaseindead-spaceventilation.ETCO2≥36mmHghadanoptimalsensitivityandspecificityof87.2%and53%,respectively,foridentifyingpatientswithoutPE.Anegativepredicativevalueof96.6%(95%confidenceinterval[CI]92.3-98.5)demonstratesthevalueofthistechnique.Thisincreasedto97.6%(99%CI93.299.2)whencombinedwithaWellsscore≤4HemnesAR,etal.EurRespirJ2010;35:735–41.AVDSf(mmHg)=(PaCO2-PETCO2)/PaCO2ETCO2急诊应用—肺栓塞TheAVDSfvaluewiththehighestsensitivityandspecificity,whichwasatthesametimestatisticallysignificant,was0.09.TheuseofAVDSfincombinationwithanyoftheseveralscoringsystemsthatevaluateclinicallikelihoodofPEandD-dimerlevelsresultedinhighersensitivityandspecificityratesforthediagnosisofPE.KurtOK,etal.AmJEmergMed.2010;28(4):460-5.

ETCO2急诊应用—酮症ETCO2可以持续实时准确反映PCO2,间接反应代谢InitialpHvalueswere7.08,RRwas35breaths/min,EtCO218.6,andvenousPCO220.pHhadimprovedto7.29,RRto22breaths/min,EtCO2to35,andthevenousPCO2to36