Effect of Pressure Support vs T-Piece Ventilation Strategies ...

Conclusions and Relevance Among patients receiving mechanical ventilation, a spontaneous breathing trial consisting of 30 minutes of pressure ... EffectofPressureSupportvsT-PieceVentilationStrategiesDuringSpontaneousBreathingTrialsonSuccessfulExtubationAmongPatientsReceivingMechanicalVentilation:ARandomizedClinicalTrial|CriticalCareMedicine|JAMA|JAMANetwork Ourwebsiteusescookiestoenhanceyourexperience.Bycontinuingtouseoursite,orclicking"Continue,"youareagreeingtoourCookiePolicy | Continue [SkiptoNavigation] fulltexticon FullText contentsicon Contents figureicon Figures/Tables multimediaicon Multimedia attachicon SupplementalContent referencesicon References relatedicon Related commentsicon Comments DownloadPDF TopofArticle KeyPoints Abstract Introduction Methods Results Discussion Conclusions ArticleInformation References VisualAbstract. PressureSupportComparedWithT-PieceVentilationStrategiesDuringSpontaneousBreathingTrialsViewLargeDownloadFigure1. FlowofParticipantsinaTrialofPressureSupportvsT-PieceVentilationStrategiesforSBTsViewLargeDownloadSBTindicatesspontaneousbreathingtrial.Figure2. ProbabilityofSuccessfulExtubationAfterFirstSBTinEachGroupViewLargeDownloadPSVindicatespressuresupportventilation;SBT,spontaneousbreathingtrial.Successfulextubationwasdefinedasremainingfreeofmechanicalventilationfor72hoursafterfirstSBT.Figure3. UnadjustedRiskRatiosforSuccessfulExtubationAfterFirstSBTinPredefinedSubgroupsViewLargeDownloadPSVindicatespressuresupportventilation;SBT,spontaneousbreathingtrial;APACHE,AcutePhysiologyandChronicHealthEvaluation;COPD,chronicobstructivepulmonarydisease.Successfulextubationwasdefinedasremainingfreeofmechanicalventilationfor72hoursafterfirstSBT. Table1. BaselineParticipantCharacteristicsaViewLargeDownloadTable2. Primary,Secondary,Exploratory,andPostHocOutcomesofPatientsWhoUnderwenta2-HourT-PieceSBTora30-MinutePSVSBTaViewLargeDownloadTable3. ExploratoryOutcomes:ReasonsforReintubationViewLargeDownload Supplement1.TrialProtocol Supplement2.eTable1.Primary,Secondary,ExploratoryandPostHocOutcomesinPatientsExtubatedAftertheFirstSpontaneousBreathingTrialeFigure1.Probabilityof90-DayMortalityAccordingtoGroupAllocationeTable2.Primary,Secondary,ExploratoryandPostHocOutcomesofPatientsWhoUnderwentaPlannedExtubationvsanExtubationOut-of-ProtocolAccordingtoGroupAllocationeAppendix.Primary,Secondary,ExploratoryandPostHocOutcomes,Per-ProtocolAnalysiseTable3.Primary,Secondary,ExploratoryandPostHocOutcomes,Per-ProtocolAnalysiseFigure2.UnadjustedRiskRatios(95%)forPatientsExtubatedAfterFirstSBTinPredefinedSubgroupseFigure3.UnadjustedRiskRatios(95%)forReintubationinPredefinedSubgroupseTable4.Patients’ConfidenceinTheirAbilitytoBreatheWithouttheVentilatorAmongPatientsExtubatedAftertheFirstSpontaneousBreathingTrialeTable5.BorgDyspneaScaleattheEndoftheSpontaneousBreathingTrialeTable6.ArterialBloodAnalysisAfterSuccessfulSpontaneousBreathingTrial Supplement3.DataSharingStatement 1.Esteban  A,Frutos  F,Tobin  MJ,  etal;SpanishLungFailureCollaborativeGroup. Acomparisonoffourmethodsofweaningpatientsfrommechanicalventilation.  NEnglJMed.1995;332(6):345-350.doi:10.1056/NEJM199502093320601PubMedGoogleScholarCrossref2.Ely  EW,Baker  AM,Dunagan  DP,  etal. Effectonthedurationofmechanicalventilationofidentifyingpatientscapableofbreathingspontaneously.  NEnglJMed.1996;335(25):1864-1869.doi:10.1056/NEJM199612193352502PubMedGoogleScholarCrossref3.Thille  AW,Cortés-Puch  I,Esteban  A. WeaningfromtheventilatorandextubationinICU.  CurrOpinCritCare.2013;19(1):57-64.doi:10.1097/MCC.0b013e32835c5095PubMedGoogleScholarCrossref4.Jaber  S,Quintard  H,Cinotti  R,  etal. Riskfactorsandoutcomesforairwayfailureversusnon-airwayfailureintheintensivecareunit:amulticenterobservationalstudyof1514extubationprocedures.  CritCare.2018;22(1):236.doi:10.1186/s13054-018-2150-6PubMedGoogleScholarCrossref5.Esteban  A,Anzueto  A,Frutos  F,  etal;MechanicalVentilationInternationalStudyGroup. Characteristicsandoutcomesinadultpatientsreceivingmechanicalventilation:a28-dayinternationalstudy.  JAMA.2002;287(3):345-355.doi:10.1001/jama.287.3.345PubMedGoogleScholarCrossref6.Peñuelas  O,Frutos-Vivar  F,Fernández  C,  etal;VENTILAGroup. Characteristicsandoutcomesofventilatedpatientsaccordingtotimetoliberationfrommechanicalventilation.  AmJRespirCritCareMed.2011;184(4):430-437.doi:10.1164/rccm.201011-1887OCPubMedGoogleScholarCrossref7.Esteban  A,Ferguson  ND,Meade  MO,  etal;VENTILAGroup. Evolutionofmechanicalventilationinresponsetoclinicalresearch.  AmJRespirCritCareMed.2008;177(2):170-177.doi:10.1164/rccm.200706-893OCPubMedGoogleScholarCrossref8.Esteban  A,Alía  I,Gordo  F,  etal;SpanishLungFailureCollaborativeGroup. ExtubationoutcomeafterspontaneousbreathingtrialswithT-tubeorpressuresupportventilation.  AmJRespirCritCareMed.1997;156(2,pt1):459-465.doi:10.1164/ajrccm.156.2.9610109PubMedGoogleScholarCrossref9.Esteban  A,Alía  I,Tobin  MJ,  etal;SpanishLungFailureCollaborativeGroup. Effectofspontaneousbreathingtrialdurationonoutcomeofattemptstodiscontinuemechanicalventilation.  AmJRespirCritCareMed.1999;159(2):512-518.doi:10.1164/ajrccm.159.2.9803106PubMedGoogleScholarCrossref10.Perren  A,Domenighetti  G,Mauri  S,Genini  F,Vizzardi  N. Protocol-directedweaningfrommechanicalventilation:clinicaloutcomeinpatientsrandomizedfora30-minor120-mintrialwithpressuresupportventilation.  IntensiveCareMed.2002;28(8):1058-1063.doi:10.1007/s00134-002-1353-zPubMedGoogleScholarCrossref11.Ezingeard  E,Diconne  E,Guyomarc’h  S,  etal. WeaningfrommechanicalventilationwithpressuresupportinpatientsfailingaT-tubetrialofspontaneousbreathing.  IntensiveCareMed.2006;32(1):165-169.doi:10.1007/s00134-005-2852-5PubMedGoogleScholarCrossref12.Sklar  MC,Burns  K,Rittayamai  N,  etal. Efforttobreathewithvariousspontaneousbreathingtrialtechniques:aphysiologicmeta-analysis.  AmJRespirCritCareMed.2017;195(11):1477-1485.doi:10.1164/rccm.201607-1338OCPubMedGoogleScholarCrossref13.Burns  KEA,Soliman  I,Adhikari  NKJ,  etal. Trialsdirectlycomparingalternativespontaneousbreathingtrialtechniques:asystematicreviewandmeta-analysis.  CritCare.2017;21(1):127.doi:10.1186/s13054-017-1698-xPubMedGoogleScholarCrossref14.Schmidt  GA,Girard  TD,Kress  JP,  etal. Liberationfrommechanicalventilationincriticallyilladults:executivesummaryofanofficialAmericanCollegeofChestPhysicians/AmericanThoracicSocietyclinicalpracticeguideline.  Chest.2017;151(1):160-165.doi:10.1016/j.chest.2016.10.037PubMedGoogleScholarCrossref15.Tobin  MJ. Extubationandthemythof“minimalventilatorsettings”.  AmJRespirCritCareMed.2012;185(4):349-350.doi:10.1164/rccm.201201-0050EDPubMedGoogleScholarCrossref16.Vallverdú  I,Calaf  N,Subirana  M,Net  A,Benito  S,Mancebo  J. Clinicalcharacteristics,respiratoryfunctionalparameters,andoutcomeofatwo-hourT-piecetrialinpatientsweaningfrommechanicalventilation.  AmJRespirCritCareMed.1998;158(6):1855-1862.doi:10.1164/ajrccm.158.6.9712135PubMedGoogleScholarCrossref17.Liang  G,Liu  T,Zeng  Y,  etal. Characteristicsofsubjectswhofaileda120-minutespontaneousbreathingtrial.  RespirCare.2018;63(4):388-394.doi:10.4187/respcare.05820PubMedGoogleScholarCrossref18.Matić  I,Majerić-Kogler  V. ComparisonofpressuresupportandT-tubeweaningfrommechanicalventilation:randomizedprospectivestudy.  CroatMedJ.2004;45(2):162-166.PubMedGoogleScholar RevisitingLiberationFromMechanicalVentilation Editorial June11,2019 TimothyD. Girard, MD,MSCI;KarenE.A. Burns, MD,FRCPC,MSc NumbersofPatientsTransposedinText Correction August20,2019 SpontaneousBreathingTrialsandSuccessfulExtubation Comment&Response November5,2019 JanO. Friedrich, MD,DPhil;KarenE.A. Burns, MD,MSc SpontaneousBreathingTrialsandSuccessfulExtubation Comment&Response November5,2019 Jordi Mancebo, MD;Ewan Goligher, MD;Laurent Brochard, MD SpontaneousBreathingTrialsandSuccessfulExtubation—Reply Comment&Response November5,2019 Carles Subirà, MD,PhD;Rafael Fernández, MD,PhD SeeMoreAbout CriticalCareMedicinePulmonaryMedicineRespiratoryFailureandVentilation SelectYourInterests SelectYourInterests CustomizeyourJAMANetworkexperiencebyselectingoneormoretopicsfromthelistbelow. 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SubiràC,HernándezG,VázquezA,etal.EffectofPressureSupportvsT-PieceVentilationStrategiesDuringSpontaneousBreathingTrialsonSuccessfulExtubationAmongPatientsReceivingMechanicalVentilation:ARandomizedClinicalTrial.JAMA.2019;321(22):2175–2182.doi:10.1001/jama.2019.7234 Downloadcitationfile: Ris(Zotero) EndNote BibTex Medlars ProCite RefWorks ReferenceManager Mendeley ©2021 Permissions OriginalInvestigation CaringfortheCriticallyIllPatient June 11,2019 EffectofPressureSupportvsT-PieceVentilationStrategiesDuringSpontaneousBreathingTrialsonSuccessfulExtubationAmongPatientsReceivingMechanicalVentilation:ARandomizedClinicalTrial Carles Subirà, MD1;Gonzalo Hernández, MD,PhD2;Antònia Vázquez, MD,PhD3;etal Raquel Rodríguez-García, MD4;Alejandro González-Castro, MD5;Carolina García, MD6;Olga Rubio, MD,PhD1,7;Lara Ventura, MD1;Alexandra López, MD8;Maria-Carmen delaTorre, MD,PhD9;Elena Keough, MD10;Vanesa Arauzo, MD11;Cecilia Hermosa, MD12;Carmen Sánchez, MD13;Ana Tizón, MD14;Eva Tenza, MD,PhD15;César Laborda, MD16;Sara Cabañes, MD17;Victoria Lacueva, MD18;Maria delMarFernández, MD,PhD19;Anna Arnau, MSc,PhD1;Rafael Fernández, RMD,PhD1,7,20 AuthorAffiliations ArticleInformation 1AlthaiaXarxaAssistencialUniversitàriadeManresa,Manresa,Spain 2HospitalVirgendelaSalud,Toledo,Spain 3HospitaldelMar,Barcelona,Spain 4HospitalU,CentraldeAsturias,Oviedo,Spain 5HospitalMarquésdeValdecilla,Santander,Spain 6HospitalUniversitariodeCanarias,SantaCruzdeTenerife,Spain 7UniversitatInternacionaldeCatalunya,Barcelona,Spain 8HospitalGeneraldeGranollers,Granollers,Spain 9HospitaldeMataró,Mataró,Spain 10HospitalGregorioMarañón,Madrid,Spain 11ConsorciSanitarideTerrassa,Terrassa,Spain 12HospitaldelHenares,Coslada,Spain 13ComplejoHospitalarioUniversitariodeCáceres,Cáceres,Spain 14ComplexoHospitalarioUniversitariodeOurense,Ourense,Spain 15Hospitald’Elx,Elche,Alicante,Spain 16HospitalValld’Hebron,Barcelona,Spain 17HospitalUniversitariodeAraba,Araba,Spain 18HospitaldeSagunt,Sagunt,Spain 19HospitalMútuaTerrassa,Terrassa,Spain 20CIBEREnfermedadesRespiratorias,InstitutodeSaludCarlosIII,Madrid,Spain JAMA.2019;321(22):2175-2182.doi:10.1001/jama.2019.7234 visualabstracticon VisualAbstract editorialcommenticon EditorialComment relatedarticlesicon RelatedArticles authorinterviewicon Interviews multimediaicon Multimedia VisualAbstract. PressureSupportComparedWithT-PieceVentilationStrategiesDuringSpontaneousBreathingTrialsViewLargeDownload Editorial RevisitingLiberationFromMechanicalVentilation TimothyD. Girard, MD,MSCI;KarenE.A. Burns, MD,FRCPC,MSc Correction NumbersofPatientsTransposedinText Comment&Response SpontaneousBreathingTrialsandSuccessfulExtubation JanO. Friedrich, MD,DPhil;KarenE.A. Burns, MD,MSc Comment&Response SpontaneousBreathingTrialsandSuccessfulExtubation Jordi Mancebo, MD;Ewan Goligher, MD;Laurent Brochard, MD Comment&Response SpontaneousBreathingTrialsandSuccessfulExtubation—Reply Carles Subirà, MD,PhD;Rafael Fernández, MD,PhD KeyPointsQuestion  Whatistheeffectofalessdemanding(30minutesofpressuresupportventilation)vsamoredemanding(2hoursofT-pieceventilation)spontaneousbreathingtrialonratesofsuccessfulextubation?Findings  Inthisrandomizedclinicaltrialthatincluded1153adultsreceivingmechanicalventilation,theproportionofpatientssuccessfullyextubatedwas82.3%amongthosewhoreceived30minutesofpressuresupportventilationcomparedwith74%amongthosewhoreceived2hoursofT-pieceventilation,adifferencethatwasstatisticallysignificant.Meaning  Thesefindingssupporttheuseofashorter,lessdemandingstrategyof30minutesofpressuresupportventilationforspontaneousbreathingtrials. Abstract Importance  Dailyspontaneousbreathingtrials(SBTs)arethebestapproachtodeterminewhetherpatientsarereadyfordisconnectionfrommechanicalventilation,butmodeanddurationofSBTremaincontroversial.Objective  ToevaluatetheeffectofanSBTconsistingof30minutesofpressuresupportventilation(anapproachthatislessdemandingforpatients)vsanSBTconsistingof2hoursofT-pieceventilation(anapproachthatismoredemandingforpatients)onratesofsuccessfulextubation.Design,Setting,andParticipants  RandomizedclinicaltrialconductedfromJanuary2016toApril2017among1153adultsdeemedreadyforweaningafteratleast24hoursofmechanicalventilationat18intensivecareunitsinSpain.Follow-upendedinJuly2017.Interventions  Patientswererandomizedtoundergoa2-hourT-pieceSBT(n = 578)ora30-minuteSBTwith8-cmH2Opressuresupportventilation(n = 557).MainOutcomeandMeasures  Theprimaryoutcomewassuccessfulextubation(remainingfreeofmechanicalventilation72hoursafterfirstSBT).SecondaryoutcomeswerereintubationamongpatientsextubatedafterSBT;intensivecareunitandhospitallengthsofstay;andhospitaland90-daymortality.Results  Among1153patientswhowererandomized(meanage,62.2[SD,15.7]years;428[37.1%]women),1018(88.3%)completedthetrial.Successfulextubationoccurredin473patients(82.3%)inthepressuresupportventilationgroupand428patients(74.0%)intheT-piecegroup(difference,8.2%;95%CI,3.4%-13.0%;P = .001).Amongsecondaryoutcomes,forthepressuresupportventilationgroupvstheT-piecegroup,respectively,reintubationwas11.1%vs11.9%(difference,−0.8%;95%CI,−4.8%to3.1%;P = .63),medianintensivecareunitlengthofstaywas9daysvs10days(meandifference,−0.3days;95%CI,−1.7to1.1days;P = .69),medianhospitallengthofstaywas24daysvs24days(meandifference,1.3days;95%CI,−2.2to4.9days;P = .45),hospitalmortalitywas10.4%vs14.9%(difference,−4.4%;95%CI,−8.3%to−0.6%;P = .02),and90-daymortalitywas13.2%vs17.3%(difference,−4.1%[95%CI,−8.2%to0.01%;P = .04];hazardratio,0.74[95%CI,0.55-0.99]).ConclusionsandRelevance  Amongpatientsreceivingmechanicalventilation,aspontaneousbreathingtrialconsistingof30minutesofpressuresupportventilation,comparedwith2hoursofT-pieceventilation,ledtosignificantlyhigherratesofsuccessfulextubation.Thesefindingssupporttheuseofashorter,lessdemandingventilationstrategyforspontaneousbreathingtrials.TrialRegistration  ClinicalTrials.govIdentifier:NCT02620358 Introduction Amongpatientsreceivingmechanicalventilation,readinessforextubationandliberationfromventilatorysupportisevaluatedwithaspontaneousbreathingtrial(SBT).1DailyscreeningofrespiratoryfunctionbySBTisassociatedwithashorterdurationofmechanicalventilation.2AfterasuccessfulSBTandextubation,10%to25%ofpatientsrequirereintubation,andreintubationisassociatedwithhighermortality.3,4 ThemostcommonmodesofSBTareT-pieceventilationandpressuresupportventilation(PSV),lastingbetween30minutesand2hours.5-7Therearenodifferencesintherateofsuccessfulextubationbetween2-hourPSVand2-hourT-pieceventilation,8betweenT-pieceventilationfor30minutesvs2hours,9orbetweenPSVfor30minutesvs2hours.10AlthoughshorterSBTsarebettertolerated,thereisnoevidencethattheyresultinhighersuccessfulextubationrates.9,10SomepatientsinwhomaT-pieceSBTfailedmighthavebeensuccessfullyextubatedafteraPSVSBT.11 Arecentmeta-analysissuggestedthatT-pieceSBTsaretheoptimalmethodforevaluatingweaningreadiness.12Nevertheless,anothermeta-analysisfoundthatPSVresultedinhigherratesofsuccessfulextubationthanT-pieceSBTs.13Moreover,thelatestAmericanThoracicSocietyguidelinesforweaningrecommendPSVSBTswithmoderate-qualityevidence.14Thus,furtherinvestigationisneededtodeterminethebestapproachforSBTs. ThisstudyhypothesizedthatlessdemandingSBTscouldresultinahigherrateofsuccessfulextubationwithoutincreasingthereintubationrate.Totestthishypothesis,2weaningstrategieswerecompared:anapproachthatismoredemandingforpatients(T-pieceSBTfor2hours)vsanapproachthatislessdemandingforpatients(8-cmH2OPSVfor30minutes). Methods FromJanuary2016throughApril2017,amulticenterrandomizedclinicaltrialwasconductedin18Spanishintensivecareunits.Theethicscommitteeofeachhospitalapprovedthestudy,andallpatientsortheirrelativesprovidedwritteninformedconsent.ThestudyprotocolisavailableinSupplement1. Patientsaged18yearsorolderundergoingmechanicalventilationforatleast24hourswhofulfilledtheweaningcriteriawereeligible.Theweaningcriteriawere(1)theresolutionorimprovementoftheconditionleadingtointubation;(2)hemodynamicstability,definedassystolicbloodpressurebetween90and160mmHgandheartratelessthan140/minwithoutvasopressorsorwithlowdosesofvasopressors;(3)GlasgowComaScalescoreof13orgreater;(4)respiratorystability(oxygensaturation>90%withfractionofinspiredoxygen[Fio2]≤0.4,respiratoryrate<35/min,spontaneoustidalvolume>5mL/kg,ratioofrespiratoryratetotidalvolume<100/minperliter,andmaximalinspiratorypressure>15cmH2O);and(5)noncopioussecretions(<3aspirationsinthelast8hours).Patientswithtracheostomiesordo-not-reintubateorderswereexcluded. Randomization Patientswererandomizedina1:1ratiotooneofthetwoweaningstrategiesbymeansoftablesofcomputer-generatedrandomnumbersinblindedblocksof4patientsforeachcenter.Acentraladministratorwhowasnotinvolvedintheanalysesusedanopaqueenvelopetoallocatepatientstoreceiveoneofthetwotreatments.Theinterventionwasnotblindedfortheinvestigatorsorattendingphysicians. Interventions PatientsrandomizedtoundergoahighlydemandingSBTunderwenta2-hourT-pieceSBT;patientsrandomizedtoundergoalessdemandingSBTunderwenta30-minuteSBTwith8-cmH2OPSVandzeropositiveend-expiratorypressure;Fio2remainedunchangedfromthemechanicalventilationperiodleadinguptotheSBT. Beforerandomization,attendingphysicianshadtodecideontheextubationstrategy(whethertoreconnectthepatienttotheventilatorfor1hourbeforeextubationandwhethertoadministernoninvasiveventilationorhigh-flownasalcannulaafterextubation). PatientswhosuccessfullycompletedtheSBTwereextubated.Arterialbloodgasanalysiswasnotrequired,butwhenitwasdone,theresultswererecorded.PhysicianswerealsorecommendedtorecorddyspneausingtheBorgDyspneaScale(scorerange,0-10;0indicatesnodyspneaand10indicatesmaximaldyspnea)atthebeginningandattheendofSBTsandtoaskpatientsabouttheirconfidenceintheirabilitytosustainbreathingwithoutaventilator. PatientswhodidnottoleratetheSBTwerereconnectedtoaventilator.CriteriaforfailuretotoleratetheSBTwereagitation,anxiety,lowlevelofconsciousness(GlasgowComaScalescore<13),respiratoryratehigherthan35/minand/oruseofaccessorymuscles,oxygensaturationbypulseoximetrylessthan90%withFio2higherthan0.5,heartratehigherthan140/minorgreaterthana20%increasefrombaseline,systolicbloodpressurelowerthan90mmHg,ordevelopmentofarrhythmia.AdditionalSBTswerenotprotocolized,andmodeanddurationwerelefttothediscretionofattendingteams. Respiratoryfailurewithin72hoursofextubationwasdefinedastheoccurrenceofatleast1ofthefollowing:respiratoryacidosiswithpHlowerthan7.32andPaco2higherthan45mmHg,oxygensaturationlessthan90%withFio2higherthan0.5,respiratoryratehigherthan35/min,lowlevelofconsciousness(GlasgowComaScalescore<13),severeagitation,orclinicalsignsofrespiratoryfatigue.Treatmentofpostextubationrespiratoryfailurewasnotprotocolized.Whennoninvasiveventilationwasused,duration,maximuminspiratoryandexpiratorypressures,andmaximumFio2wererecorded.Whenrespiratoryfailurewastreatedwithahigh-flownasalcannula,duration,maximumflow,andmaximumFio2wererecorded. Patientsneedingreintubationwithin72hourswerenotrandomizedagainforweaning,buttheneedfortracheostomyandthedateoffinalliberationfrommechanicalventilationwereregistered. Outcomes Theprimaryoutcomewassuccessfulextubation,definedasremainingfreeofinvasivemechanicalventilation72hoursafterthefirstSBT. SecondaryoutcomeswererateofreintubationamongpatientswhowereextubatedaftertheSBT;intensivecareunitandhospitallengthsofstay;andhospitaland90-daymortality. Exploratoryoutcomesweretimetoreintubationandreasonsforreintubation,incidenceoftracheostomy,anduseofnoninvasiveventilationandhigh-flownasalcannulaasprophylaxisagainstpostextubationrespiratoryfailureandtotreatit. Posthocoutcomeswereintensivecareunitmortality,BorgDyspneaScalescoreattheendoftheSBT,patients’confidenceintheirabilitytobreathewithouttheventilator,andarterialbloodanalysisaftersuccessfulSBT. StatisticalAnalysis Basedonpreviousstudies,8,9asuccessfulextubationrateof75%andanabsoluteincreaseinsuccessfulextubationof7%wereexpected.Thus,therequiredsampleforanα=.05andapowerof80%wasestimatedtobe540patientsineachgroup. Aprespecifiedinterimanalysiswasperformedwhen500patientswereenrolled.Theresultsshowedanonsignificantdifferenceinprimaryoutcomebetweengroups.Forthisreason,theinvestigatorsdecidedtocompletetheestimatedsampleenrollment. Allpatientswereanalyzedinthegrouptowhichtheywererandomizedusingtheintention-to-treatprinciple,withnoexclusionafterrandomization.PatientsextubatedoutsideofprotocolwereanalyzedashavingafailedSBT.Noparticipantswereexcludedfrommainorsecondaryanalysesbecauseofmissingorincompletedata.Reintubationwasrecordedonlyamongpatientswhocompletedthetrial. Categoricalvariablesarepresentedasabsoluteandrelativefrequencies.Continuousvariablesaresummarizedasmediansandinterquartileranges(IQRs)fornonnormaldistributions.TheMann-WhitneyUwasusedfornonparametriccontinuousvariables.Tocomparecategoricalvariables,theχ2testwasused,exceptwhenexpectedfrequenciesincontingencytableswerelessthan5,inwhichcasetheFisherexacttestortheMonteCarlomethodwasused. Time-to-eventoutcomeswereanalyzedwithKaplan-Meiercurvesandcomparedbylog-ranktest.Forthetime-to-eventoutcomeof72-hoursuccessfulextubation,deathsoccurringbefore72hourswereintroducedinthesurvivalanalysisascensoreddata.Eventorcensoredtimesforallpatientswerecalculatedfromthetimeofrandomization.Crudehazardratiosand95%confidenceintervalswerecalculatedusingaunivariableCoxproportionalregressionmodeltoestimatetheeffectsizeofrandomizationgroup.ProportionalityofhazardswasverifiedbyexaminingSchoenfeldresidualplots. Aposthocrandom-effectsmultilevellogisticregressionmodelwasusedtodeterminevariablesassociatedwith72-hoursuccessfulextubation,takingintoaccounttheeffectofhospital.Patientcharacteristicsthatwereassociatedwith72-hoursuccessfulextubationinthebivariableanalysiswereintroducedintherandom-effectsmultilevellogisticregressionmodelasfirst-levelvariablesandhospitalasasecond-levelvariable(randomeffect).Oddsratios(ORs)andmedianORswith95%confidenceintervalswereusedtomeasuretheassociationbetweeneachcovariateand72-hoursuccessfulextubation.ThemedianORisameasureofthevariationbetweenratesof72-hoursuccessfulextubationatdifferenthospitalsthatisunexplainedbythemodeledriskfactors;itisdefinedasthemedianofthesetofORsthatcouldbeobtainedbycomparing2patientswithidenticalpatient-levelcharacteristicsfrom2randomlychosenhospitals.Covariateswereintroducedintherandom-effectsmultilevellogisticregressionmodelusingaresearcher-controlledbackwardexclusionstrategy. Posthocanalyseswereperformedforprimary,secondary,exploratory,andposthocoutcomesamongthefollowingpopulations:patientsextubatedafterthefirstSBT,patientsextubatedoutsideofprotocol,patientstreatedperprotocol,andseveralsubgroupsdefinedbybaselinedemographiccharacteristics.Effectsizeswereevaluatedbycomputingabsoluteriskdifferenceswith95%confidenceintervalsforbinaryoutcomesanddifferencesinmeanswith95%confidenceintervalsforcontinuousoutcomes.Figureswereplottedforunadjustedriskratiosand95%confidenceintervalsinthesubgroupanalysisbyage;daysofmechanicalventilation;AcutePhysiologyandChronicHealthEvaluation(APACHE)IIscore;chronicobstructivepulmonarydisease(COPD);andmedical,surgical,ortraumaadmission.Notestsforinteractionwereconductedforthesubgroupanalyses. A2-sidedα=.05wasconsideredstatisticallysignificant.DatawereanalyzedusingSPSSversion22(IBMCorp)andStataversion14(StataCorp).SubgroupanalysisgraphsweregeneratedusingRversion3.5.2(RFoundationforStatisticalComputing).Therewasnoadjustmentformultiplecomparisons.Therefore,theresultsofthesubgroupanalysesandtheanalysesforsecondaryandexploratoryoutcomesshouldbeinterpretedasexploratory. Results StudyParticipants Figure1showsparticipantflowthroughthetrial.Duringthestudyperiod,2649patientsreceivedmechanicalventilationforatleast24hoursintheparticipatingintensivecareunits;1501ofthesefulfilledtheinclusioncriteria,and1153wereincludedinthestudy;578patientswererandomizedtoundergoa2-hourT-pieceSBTand575patientswererandomizedtoundergoa30-minuteSBTwith8-cmH2OPSV).The2groupsweresimilarinage,sex,APACHEIIscoreonadmission,reasonforintensivecareunitadmission,andlengthofmechanicalventilationbeforetheSBT(Table1).Nopatientswerelosttofollow-up. PrimaryOutcome Successfulextubation,definedasremainingfreeofmechanicalventilation72hoursaftertheSBT,occurredin473patients(82.3%)inthePSVgroupand428patients(74%)intheT-piecegroup(difference,8.2%;95%CI,3.4%-13%)(Table2). TheKaplan-Meiercurvesshowasignificantdifference,withahighersuccessfulextubationrateinthePSVgroup(hazardratio,1.54;95%CI,1.19-1.97;P