Post on 20-Sep-2020
transcript
Earlyapplicationofairwaypressurereleaseventilationmayreducethedurationofmechanicalventilationin
acuterespiratorydistresssyndromeIntensiveCareMedicine201743:1648-1659
Introduction
• MVisessentialinpatientswithARDSbutcancauselunginjuryduetoregionalalveolarstretchandorrepetitivealveolarcollapsewithshearing• Ideallyshouldmaintainlungunitsopenthroughoutventilatory cycle• Difficultwhenlungisheterogenous
• InconventionalMV,selectionof“optimum”PEEPtobalancerecruitmentagainstoverdistensionisstillanunresolvedproblem• Mortalityremainshighamongthosereceivingmechanicalventilation
Introduction
• AirwayPressureReleaseVentilation(APRV)deliverscontinuouspositiveairwaypressurewithbriefintermittentreleasephase• Allowsonlypartialreleaseoflungvolumeandspontaneousbreathingthroughouthighlevel• InanimalswithARDS,APRV:• Improvedalveolarrecruitmentandgasexchange• Increasedhomogeneity• Reducedlunginjury
• DataonAPRVinARDSlimitedandusuallysourcedfromsmalltrialswithoutdatedsettings
Hypothesis
• InpatientswithARDS,earlyapplicationofupdatedAPRVmethodologywouldbetterimproveoxygenationandrespiratorysystemcomplianceandreducethedurationofmechanicalventilationcomparedtoconventionalLTV
MaterialsandMethods
• CriticalCareDepartmentofWestChinaHospitalofSichuanUniversity,SichuanProvince• Enrollment May2015-Oct2016• Appropriateethicssought• Allocationappropriatelyrandomised
InclusionCriteria
• DiagnosticcriteriaforARDS(Berlin)• PF<250• Intubatedandventilated<48hrspriortoinclusion
ExclusionCriteria
• Pregnancy• Anticipatedventilation<48hrs• Intracranialhypertension(incl suspected)• Neuromusculardisorders• SevereCOPD• Pre-existingconditionswith6/12mortality>50%• Documentedbarotrauma• TreatmentwithECMO• Refractoryshock• Lackofcommitmenttolifesupport• Age<18or>85
VentilatorSettings- Initial
• VCV(PuritanBennet840)• Pplat<30cmH20• PaO2 7.3-13.3kPa• pH>7.30
VentilatorSettings- LTV
• Vt 6ml/kgPBW(?)• PEEPlevelsadjustedbyPEEP-FiO2 table• Vt andRRregulatedtoachievepHandPplat accordingtoARDSnetprotocol• Inhypotension/ptx,PEEPcouldbefurthertitrated• IfPF<150withFiO2 >0.6,PEEPcouldbefurtheroptimised• IfsevereacidosispH<7.15,RRincreasedto35/min• Ifsevererespiratoryacidosispersisted,NAHCO3 couldbegiven
VentilatorSettings- APRV
• Phigh=Pplat• Plow=5cmH2O• Tlow 1-1.5*expiratorytimeconstantthenadjustedtoachievePEFRof>50%PEFR• Releasefrequency10-14/min• Thigh indirect• AimedforMVspont tobe30%MVtotal
ProcedureBothGroups
• Supportivetherapies(recruitment,proning,NMB,iNO)inbothgroupsasrequired• Rescuemeasures(incl ECMOandHFOV)atcliniciandiscretion• Usualcare• InLTV,dailysedationholdsandSBT• InAPRV,initiallyreducedPhigh by2cmH2Oandreducedreleaserateby2/mintwicedaily• ThenonceonPhigh 20cmH20andFiO2 0.4,sameweaning
• ExtubatedwhenSBTsuccessful
Endpoints
• Primary– Ventilatorfreedaysatday28• Secondaryendpoints• Oxygenation• Pplat,MAP,compliance• Clinicaloutcomes
StatisticalAnalysis
• Meanventilatorfreedays14.5+-10.4• ReportedthatAPRVcouldshortendurationby6days• Conservativeestimateofsamplesize=110
Results
Discussion
• ComparedwithLTVgroup,theAPRVgrouphad:• Shorterdurationofventilation• Improvedoxygenation• Improvedcompliance• Decreasedplateaupressure• Reducedsedation• ShorterlengthofICUstay*• Higherrateofsuccessfulextubation*• Lowertracheostomyrate*
• *Non-significant
Discussion
• Nodifferencein:• Hospitallengthofstay• ICUmortality• Incidenceofpneumothorax
Discussion
• Accordingtorecentexperimentalfindings,setPhigh nottoexceed30cmH20andTlow tobe>50%PEFR,thesesettingswerecombinedwithAPRVsettingsandsedationtitrationtoachievespontaneousbreathtargetlevel• CollateralchannelsofventilationsuchastheporesofKohnwhichmightbeadditionalpathwaystofacilitaterecruitmentandredistributealveolarvolumethroughoutthelungovertime• Otherstudiesindicatethattheprocessofrecruitmentandderecruitmentoflungunitsshouldbedeterminednotonlybypressurebutalsobytime.• APRVfavouredhaemodynamicimprovementandreducedsedativeandparalysisused
Discussion
• APRVgroupassociatedwithmoredayswithoutmechanicalventilationatD28andashorterICUstaythantheLTVgroup• Possibleexplanations:• EarlyuseofAPRVimprovespulmonaryfunctionsuchasgasexchangeandrespiratorycompliance• RecentexperimentshavealsodocumentedthatearlypreventativeuseofAPRVcanmoreeffectivelyblockARDSdevelopmentthanLTV• APRVallowsmoderatespontaneousventilation,reducessedationandparalysisrequirement,anddecreasesdurationofmechanicalventilation• Inthestudy,respiratorytherapiststitratedAPRVsettingsanddosagesofsedativesetc.• Theyalsoguidedweaning
Limitations(Author)
• Studynotblinded• Samplesizesmall• Possibilityofknowledgebias(althoughtheydidasmallertrialfirstandfoundalltherapistswelltrainedandskillfully usedstudyprotocol• MorepatientswithcoexistingchronicdiseasesintheLTVgroup• Studydidnotmeasurepatient-ventilatorsynchrony
Conclusion
• ComparedwithconventionalLTV,theearlyapplicationofAPRVinpatientswithARDSwasassociatedwithbetteroxygenationandrespiratorysystemcompliance,lowerplateauairwaypressure,lesssedationrequirement,moreventilator-freedaysatday28,andashorterdura- tion ofICUstay.
MyThoughts
• Thisissinglecentrewithapopulationunlikeours(young,thin)• TheyareclearlyAPRVenthusiasts,ifanythingtheyareuncertainwhattheyaredoingwithLTV!!(sedation,tracheostomyrate)• TheyuseVCVnotPCV• I’munclearthatyoucanmeasurerespiratoryphysiologyinthesamewaywithAPRV• AmovetoAPRVwouldbeaparadigmshiftoftheorderofnegativepressure->positivepressureventilation• Wouldneedcompletebuy-in• Berlinguidance?