急性呼吸窘迫综合征-英文课件.ppt

急性呼吸窘迫综合征-英文课件Childrens Hospital of MichiganA.K.A.l Adult Respiratory Distress Syndromel Da Nang Lungl Transfusion Lungl Post Perfusion Lungl Shock Lungl Traumatic Wet LungChildrens Hospital of MichiganHISTORICAL PERSPECTIVESlDescribed by William Osler in the 1800slAshbaugh,Bigelow and Petty,Lancet 1967n12 patientsnpathology similar to hyaline membrane disease in neonateslARDS is also observed in childrenlNew criteria and definitionChildrens Hospital of MichiganORIGINAL DEFINITIONlAcute respiratory distresslCyanosis refractory to oxygen therapylDecreased lung compliancelDiffuse infiltrates on chest radiographlDifficulties:nlacks specific criteriancontroversy over incidence and mortalityChildrens Hospital of MichiganREVISION OF DEFINITIONSl1988:four-point lung injury scorenLevel of PEEPnPaO2/FiO2 rationStatic lung compliancenDegree of chest infiltratesl1994:consensus conference simplified the definitionChildrens Hospital of Michigan1994 CONSENSUSlAcute onsetnmay follow catastrophic eventlBilateral infiltrates on chest radiographlPAWP 18 mm HglTwo categories:nAcute Lung Injury-PaO2/FiO2 ratio 300nARDS-PaO2/FiO2 ratio 200Childrens Hospital of MichiganEPIDEMIOLOGYlEarlier numbers inadequate(vague definition)lUsing 1994 criteria:n17.9/100,000 for acute lung injuryn13.5/100,000 for ARDSnCurrent epidemiologic study underwaylIn children:approximately 1%of all PICU admissionsChildrens Hospital of MichiganINCITING FACTORSlShocklAspiration of gastric contentslTraumalInfectionslInhalation of toxic gases and fumeslDrugs and poisonslMiscellaneousChildrens Hospital of MichiganSTAGESlAcute,exudative phasenrapid onset of respiratory failure after triggerndiffuse alveolar damage with inflammatory cell infiltrationnhyaline membrane formationncapillary injurynprotein-rich edema fluid in alveolindisruption of alveolar epitheliumChildrens Hospital of MichiganSTAGESlSubacute,Proliferative phase:npersistent hypoxemiandevelopment of hypercarbianfibrosing alveolitisnfurther decrease in pulmonary compliancenpulmonary hypertension Childrens Hospital of MichiganSTAGESlChronic phasenobliteration of alveolar and bronchiolar spaces and pulmonary capillarieslRecovery phasengradual resolution of hypoxemianimproved lung compliancenresolution of radiographic abnormalitiesChildrens Hospital of MichiganMORTALITYl40-60%lDeaths due to:nmulti-organ failurensepsislMortality may be decreasing in recent yearsnbetter ventilatory strategiesnearlier diagnosis and treatmentChildrens Hospital of MichiganPATHOGENESISlInciting eventlInflammatory mediatorsnDamage to microvascular endotheliumnDamage to alveolar epitheliumnIncreased alveolar permeability results in alveolar edema fluid accumulationChildrens Hospital of MichiganNORMAL ALVEOLUSType I cellEndothelialCellRBCsCapillaryAlveolarmacrophageType IIcellChildrens Hospital of MichiganACUTE PHASE OF ARDSType I cellEndothelialCellRBCsCapillaryAlveolarmacrophageType IIcellNeutrophilsChildrens Hospital of MichiganPATHOGENESISlTarget organ injury from hosts inflammatory response and uncontrolled liberation of inflammatory mediatorslLocalized manifestation of SIRSlNeutrophils and macrophages play major roleslComplement activationlCytokines:TNF-a,IL-1b,IL-6lPlatelet activation factorlEicosanoids:prostacyclin,leukotrienes,thromboxanelFree radicalslNitric oxideChildrens Hospital of MichiganPATHOPHYSIOLOGYlAbnormalities of gas exchangelOxygen delivery and consumptionlCardiopulmonary interactionslMultiple organ involvementChildrens Hospital of MichiganABNORMALITIES OF GAS EXCHANGElHypoxemia:HALLMARK of ARDSnIncreased capillary permeabilitynInterstitial and alveolar exudatenSurfactant damagenDecreased FRCnDiffusion defect and right to left shuntChildrens Hospital of MichiganOXYGEN EXTRACTIONVO2=Q x Hb X 13.4 X(SaO2 -SvO2)ArterialInflow(Q)capillaryO2O2O2O2O2O2O2VenousOutflow (Q)CellO2(Adapted from the ICU Book by P.Marino)Childrens Hospital of MichiganOXYGEN DELIVERYDO2=Q X CaO2DO2=Q X(1.34 X Hb X SaO2)X 10Q=cardiac outputCaO2=arterial oxygen contentNormal DO2:520-570 ml/min/m2Oxygen extraction ratio=(SaO2-SvO2/SaO2)X 100Normal O2ER=20-30%Childrens Hospital of MichiganHEMODYNAMIC SUPPORTMax O2extractionCritical DO2VO2=DO2 X O2ERDO2VO2NormalMax O2extractionCritical DO2Abnormal Flow DependencyDO2VO2Septic Shock/ARDSChildrens Hospital of MichiganOXYGEN DELIVERY&CONSUMPTIONlPathologic flow dependencynUncoupling of oxidative dependencynOxygen utilization by non-ATP producing oxidase systemsnIncreased diffusion distance for O2 between capillary and alveolusChildrens Hospital of MichiganCARDIOPULMONARY INTERACTIONSlA=Pulmonary hypertension resulting in increased RV afterloadlB=Application of high PEEP resulting in decreased preloadlA+B=Decreased cardiac outputChildrens Hospital of MichiganRESPIRATORY SUPPORTlConventional mechanical ventilationlNewer modalities:nHigh frequency ventilationnECMOlInnovative strategiesnNitric oxidenLiquid ventilationnExogenous surfactantChildrens Hospital of MichiganMANAGEMENTlMonitoring:nRespiratorynHemodynamicnMetabolicnInfectionsnFluids/electrolytesChildrens Hospital of MichiganMANAGEMENTlOptimize VO2/DO2 relationshiplDO2nhemoglobinnmechanical ventilationnoxygen/PEEPlVO2npreloadnafterloadncontractilityChildrens Hospital of MichiganCONVENTIONAL VENTILATIONlOxygenlPEEPlInverse I:E ratiolLower tidal volumelVentilation in prone positionChildrens Hospital of MichiganRESPIRATORY SUPPORTlGoal:maintain sufficient oxygenation and ventilation,minimize complications of ventilatory managementnImprove oxygenation:PEEP,MAP,Ti,O2nImprove ventilation:change in pressureChildrens Hospital of MichiganMechanical Ventilation GuidelineslAmerican College of Chest Physicians Consensus Conference 1993nGuidelines for Mechanical Ventilation in ARDSnWhen possible,plateau pressures 20 and failure to decrease OI by 20%at six hours predicted death with 88%(7/8)sensitivity and 83%(19/23)specificity,with an odds ratio of 33(p=.0036,95%confidence interval 3-365)Childrens Hospital of MichiganSTUDY CONCLUSIONSlIn patients with potentially reversible underlying diseases resulting in severe acute respiratory failure that is unresponsive to conventional ventilation,high frequency ventilation improves gas exchange in a rapid and sustained fashion.lThe magnitude of impaired oxygenation and its improvement after high frequency ventilation can predict outcome within 6 hours.Childrens Hospital of MichiganHigh Frequency Oscillating Ventilation(HFOV)Pediatric ARDSlArnold JH et al.Crit Care Med 1994;22:1530-1539.nProspective,randomized clinical study with crossover of 70 patientsnHFOV had fewer patients requiring O2 at 30 daysnHFOV patients had increase survivornSurvivors had less chronic lung diseaseChildrens Hospital of MichiganNew England Journal of Medicine 2000;342:1301-8Childrens Hospital of MichiganSTUDY CONCLUSIONlIn patients with acute lung injury and the acute respiratory distress syndrome,mechanical ventilation with a lower tidal volume than is traditionally used results in decreased mortality and increases the number of days without ventilator useChildrens Hospital of MichiganProne PositionlImproved gas exchangelMore uniform alveolar ventilationlRecruitment of atelectasis in dorsal regionslImproved postural drainagelRedistribution of perfusion away from edematous,dependent regionsChildrens Hospital of MichiganProne PositionlNakos G et al.Am J Respir Crit Care Med 2000;161:360-68nObservational study of 39 patients with ARDS in different stagesn Improved oxygenation in prone(PaO2/FiO2 18934 prone vs.8314 supine)after 6 hoursnNo improvement in patients with late ARDS or pulmonary fibrosisChildrens Hospital of MichiganProne PositionlNEJM 2001;345:568-73nProne-Supine Study GroupnMulticenter randomized clinical trialn304 adult patients prospectively randomized to 10 days of supine vs.prone ventilation 6 hours/daynImproved oxygenation in prone positionnNo improvement in survivalChildrens Hospital of MichiganExogenous SurfactantlSuccess with infants with neonatal RDSlExosurf ARDS Sepsis Study.Anzueto et al.NEJM 1996;334:1417-21nRandomized control trialnMulticenter study of 725 patients with sepsis induced ARDSnNo significant difference in oxygenation,duration of mechanical ventilation,hospital stay,or survivalChildrens Hospital of MichiganExogenous SurfactantlAerosol delivery system only 4.5%of radiolabeled surfactant reached lungslOnly reaches well ventilated,less severe areaslNew approaches to delivery are under study,including tracheal instillation and bronchoalveolar lavageChildrens Hospital of MichiganInhaled Nitric Oxide(iNO)lPulmonary vasodilatorlSelectively improves perfusion of ventilated areaslReduces intrapulmonary shuntinglImproves arterial oxygenationlT1/2 111 to 130 mseclNo systemic hemodynamic effectsChildrens Hospital of MichiganInhaled Nitric Oxide(iNO)lInhaled Nitric Oxide Study Group lDellinger RP et al.Crit Care Med 1998;26:15-23nProspective,randomized,placebo controlled,double blinded,multi-center studyn177 adults with ARDSnImprovement in oxygenation indexnNo significant differences in mortality or days off ventilatorChildrens Hospital of MichiganInhaled Aerosolized Prostacyclin(IAP)lPotent selective pulmonary vasodilatorlEffective for pulmonary hypertensionlShort half-life(2-3 min)with rapid clearancelLittle or no hemodynamic effectlRandomized clinical trials have not been doneChildrens Hospital of MichiganCorticosteroidsAcute Phase TrialslBernard GR et al.NEJM 1987;317:1565-70n99 patients prospectively randomizednMethylprednisolone(30mg/kg q6h x 4)vs.placebo nNo differences in oxygenation,chest radiograph,infectious complications,or mortalityChildrens Hospital of MichiganCorticosteroidsFibroproliferative StagelMeduri GU et al.JAMA 1998;280:159-65n24 patients with severe ARDS and failure to improve by day 7 of treatmentnPlacebo vs.methylprednisolone 2mg/kg/day for 32 daysnSteroid group showed improvement in lung injury score,improved oxygenation,reduced mortalitynNo significant difference in infection rateChildrens Hospital of MichiganPROGNOSISlUnderlying medical conditionlPresence of multiorgan failurelSeverity of illnessChildrens Hospital of MichiganWe are constantly misledby the ease with which ourminds fall into the ruts ofone or two experiences.Sir William Osler