呼吸衰竭RespiratoryFailure英文

呼吸衰竭RespiratoryFailure英文第1頁/共39頁RESPIRATORYFAILURE“inabilityofthelungtomeetthemetabolicdemandsofthebody.Thiscanbefromfailureoftissueoxygenationand/orfailureofCO2homeostasis.”第2頁/共39頁RESPIRATORYFAILUREDefinitionRespirationisgasexchangebetweentheorganismanditsenvironment.FunctionofrespiratorysystemistotransferO2fromatmospheretobloodandremoveCO2fromblood.ClinicallyRespiratoryfailureisdefinedasPaO2<60mmHgwhilebreathingair,oraPaCO2>50mmHg.第3頁/共39頁Respiratorysystemincludes:

CNS(medulla)Peripheralnervoussystem(phrenicnerve)RespiratorymusclesChestwallLungUpperairwayBronchialtreeAlveoliPulmonaryvasculature第4頁/共39頁PotentialcausesofRespiratoryFailure第5頁/共39頁HYPOXEMICRESPIRATORYFAILURE(TYPE1)PaO2<60mmHgwithnormalorlowPaCO2

normalorhighpHMostcommonformofrespiratoryfailureLungdiseaseisseveretointerferewithpulmonaryO2exchange,butoverallventilationismaintainedPhysiologiccauses:V/Qmismatchandshunt第6頁/共39頁HYPOXEMICRESPIRATORYFAILURECAUSESOFARTERIALHYPOXEMIA

1. FiO2 2. Hypoventilation(PaCO2)Hypercapnic3. V/Qmismatch Respiratoryfailure (eg.COPD) 4. Diffusionlimitation? 5. Intrapulmonaryshunt -pneumonia -Atelectasis -CHF(highpressurepulmonaryedema) -ARDS(lowpressurepulmonaryedema)

第7頁/共39頁CausesofHypoxemicRespiratoryfailureCausedbyadisorderofheart,lungorblood.EtiologyeasiertoassessbyCXRabnormality: -NormalChestx-ray Cardiacshunt(righttoleft) Asthma,COPD Pulmonaryembolism

第8頁/共39頁HyperinflatedLungs:COPD第9頁/共39頁CausesofHypoxemicRespiratoryfailure(cont’d.)FocalinfiltratesonCXR Atelectasis Pneumonia第10頁/共39頁Anexampleofintrapulmonaryshunt第11頁/共39頁CausesofHypoxemicRespiratoryFailure(cont’d.)DiffuseinfiltratesonCXRCardiogenicPulmonaryEdemaNoncardiogenicpulmonaryedema(ARDS)InterstitialpneumonitisorfibrosisInfections第12頁/共39頁Diffusepulmonaryinfiltrates第13頁/共39頁HypercapnicRespiratoryFailure

(TypeII)PaCO2>50mmHgHypoxemiaisalwayspresentpHdependsonlevelofHCO3HCO3dependsondurationofhypercapniaRenalresponseoccursoverdaystoweeks第14頁/共39頁AcuteHypercapnicRespiratoryFailure(TypeII)AcuteArterialpHislowCauses -sedativedrugoverdose -acutemuscleweaknesssuchasmyastheniagravis -severelungdisease: alveolarventilationcannotbemaintained(i.e.Asthmaorpneumonia)Acuteonchronic:ThisoccursinpatientswithchronicCO2retentionwhoworsenandhaverisingCO2andlowpH.Mechanism:respiratorymusclefatigue第15頁/共39頁CausesofHypercapnicRespiratoryfailureRespiratorycentre(medulla)dysfunctionDrugoverdose,CVA,tumor,hypothyroidism,centralhypoventilationNeuromusculardisease Guillain-Barre,MyastheniaGravis,polio,spinalinjuriesChestwall/Pleuraldiseases kyphoscoliosis,pneumothorax,massivepleuraleffusionUpperairwaysobstruction tumor,foreignbody,laryngealedemaPeripheralairwaydisorder asthma,COPD第16頁/共39頁ClinicalandLaboratoryManifestation

(non-specificandunreliable)Cyanosis-bluishcolorofmucousmembranes/skinindicatehypoxemia-unoxygenatedhemoglobin50mg/L-notasensitiveindicatorDyspnea-secondarytohypercapniaandhypoxemiaParadoxicalbreathingConfusion,somnolenceandcomaConvulsions第17頁/共39頁ASSESSMENTOFPATIENTCarefulhistoryPhysicalExaminationABGanalysis-classifyRFandhelpwithcause 1)PaCO2=VCO2x0.863

VA 2)P(A-a)02=(PiO2-PaCO2)–PaO2

RLungfunction OVPvsRVPvsNVPChestRadiographEKG第18頁/共39頁Clinical&LaboratoryManifestationsCirculatorychanges -tachycardia,hypertension,hypotensionPolycythemia-chronichypoxemia-erythropoietinsynthesisPulmonaryhypertensionCor-pulmonaleorrightventricularfailure第19頁/共39頁ManagementofRespiratoryFailurePrinciplesHypoxemiamaycausedeathinRFPrimaryobjectiveistoreverseandpreventhypoxemiaSecondaryobjectiveistocontrolPaCO2andrespiratoryacidosisTreatmentofunderlyingdiseasePatient’sCNSandCVSmustbemonitoredandtreated

第20頁/共39頁OxygenTherapySupplementalO2therapyessentialtitrationbasedonSaO2,PaO2levelsandPaCO2GoalistopreventtissuehypoxiaTissuehypoxiaoccurs(normalHb&C.O.) -venousPaO2<20mmHgorSaO2<40% -arterialPaO2<38mmHgorSaO2<70%IncreasearterialPaO2>60mmHg(SaO2>90%)orvenousSaO2>60%O2doseeitherflowrate(L/min)orFiO2(%)第21頁/共39頁RisksofOxygenTherapyO2toxicity:-veryhighlevels(>1000mmHg)CNStoxicityand seizures-lowerlevels(FiO2>60%)andlongerexposure:- capillarydamage,leakandpulmonaryfibrosis-PaO2>150cancauseretrolentalfibroplasia-FiO235to40%canbesafelytoleratedindefinitelyCO2narcosis:-PaCO2mayincreaseseverelytocauserespiratory acidosis,somnolenceandcoma-PaCO2increasesecondarytocombinationof a)abolitionofhypoxicdrivetobreathe b)increaseindeadspace第22頁/共39頁第23頁/共39頁第24頁/共39頁MECHANICALVENTILATIONNoninvasivewithamaskInvasivewithanendobronchialtubeMVcanbevolumeorpressurecycledForhypercapnia:-MVincreasesalveolarventilationandlowers PaCO2,correctspH -restsfatiguesrespiratorymusclesForhypoxemia:-O2therapyalonedoesnotcorrecthypoxemia causedbyshunt -Mostcommoncauseofshuntisfluidfilledor collapsedalveoli(Pulmonaryedema)第25頁/共39頁第26頁/共39頁第27頁/共39頁POSITIVEENDEXPIRATORYPRESSURE(PEEP)PEEPincreasestheendexpiratorylungvolume(FRC)PEEPrecruitscollapsedalveoliandpreventsrecollapseFRCincreases,thereforelungbecomesmorecompliantReversalofatelectasisdiminishesintrapulmonaryshuntExcessivePEEPhasadverseeffects-decreasedcardiacoutput-barotrauma(pneumothorax,pneumomediastinum)-increasedphysiologicdeadspace-increasedworkofbreathing第28頁/共39頁第29頁/共39頁PULMONARYEDEMAPulmonaryedemaisanincreaseinextravascularlungwaterInterstitialedemadoesnotimpairfunctionAlveolaredemacauseseveralgasexchangeabnormalitiesMovementoffluidisgovernedbyStarling’sequation QF=KF[(PIV-PIS)+(IS-IV)

QF=rateoffluidmovementKF=membranepermeabilityPIV&PISareintravascularandinterstitialhydrostaticpressuresISandIVareinterstitialandintravascularoncoticpressures reflectioncoefficientLungedemaisclearedbylymphatics第30頁/共39頁AdultRespiratorydistressSyndrome(ARDS)VarietyofunrelatedmassiveinsultsinjuregasexchangingsurfaceofLungsFirstdescribedasclinicalsyndromein1967byAshbaugh&PettyClinicaltermssynonymouswithARDS Acuterespiratoryfailure Capillaryleaksyndrome DaNangLung ShockLung TraumaticwetLung Adulthyalinemembranedisease第31頁/共39頁RiskFactorsinARDS

Sepsis3.8%Cardiopulmonarybypass1.7%Transfusion5.0%Severepneumonia12.0%Burn2.3%Aspiration35.6%Fracture5.3%Intravascularcoagulopathy12.5%Twoormoreoftheabove24.6%第32頁/共39頁PATHOPHYSIOLOGYANDPATHOGENESISDiffusedamagetogas-exchangingsurfaceeitheralveolarorcapillarysideofmembraneIncreasedvascularpermeabilitycausespulmonaryedemaPathology:fluidandRBCininterstitialspace,hyalinemembranesLossofsurfactant:alveolarcollapse第33頁/共39頁CRITERIAFORDIAGNOSISOFARDSClinicalhistoryofcatastrophicevent PulmonaryorNonpulmonary(shock,multisystem trauma) Exclude chronicpulmonarydiseases leftventricularfailureMusthaverespiratorydistress