REVIEW ARTICLE Optimizing Emergent Surgical Cricothyrotomy for use in Austere Environments - PDF document

Asurgicalcricothyrotomyisalmostalwaysaprocedureoflastresortbecauseofitsinvasivenessandprovidercomfortorlackthereof.Mostpatientswhorequirecricothyrotomyintheemergencydepartment(ED)havefailedmultipleETintubationattemptsandarepossi-blycriticallyhypoxic,requiringfurtherintervention.Intheprehospitalsetting,mostcricothyrotomycandidateshaveeithercardiacarrestorblunttraumaandfailedETintuba-tionattempts.Survivorsfrequentlyhavepoorneurologicaloutcomeandhighmortalityrates.Inausteresettings,theuseofETintubationandsupraglotticdevicesmaynotbepossibleorappropriatebecauseoftacticalorsituationalconstraints,evenwhenappropriateforthepatient.Thus,cricothyrotomyisevenmorerelevantintheseenviron-9Ð12Althoughcricothyrotomyisbecominglesscommonasotheralternativeairwaydevicesareintroduced,suchasthelaryngealmaskairway,KingLT-D(KingSystemsCorp,Noblesville,IN),andothersupraglotticdevices,thereis,andlikelyalwayswillbe,aroleforcricothy-rotomyinasubsectionofpatientswithdifÞcultairways,especiallyinenvironmentsinwhichsuchdevicesareunlikelytobeavailable.Acommonemergencymedicineaphorismis:ÒIfyoudoonecricothyrotomy,youÕreahero;ifyoudotwo,workonyourairwayskills.ÓTrueperhapsinahospital,butinanaustereenvironmentmanyfactorsbesidesfailedETintubationleadtoearlycricothyrotomy.Wildernessprovidersmustbenotonlytechnicallyskilled,butalsoadequatelytrainedtorecog-nizethekeyindicationsandsituationaldecisiontriggersforcricothyrotomythatdifferfromin-hospitalpractice.Researchoncricothyrotomyvariesintermsofthepro-ceduresandtoolsevaluated.Additionally,outcomessuchasproceduretime,successrates,andcomplications,aswellasothervariables(eg,trainingmodels,researchenvironments,providerlevelandspecialty,andpatient-relatedfactors)arenotuniformacrossstudies.Furthermore,cricothyrotomyis,atmost,aninfrequentlyperformedprocedure,andresearchontraumaandemergentpatientsisexceedinglydifÞcult.Casestudiesandretrospectiveanalysesabound,buttherearefewprospective,randomized,controlled,crossoverstudies.Thisreviewwillfocusonsurgicalcricothyrotomyoutsidethehospitalsetting,butdrawfromhospital-basedstudieswhenrelevanttotheperformanceofthisprocedureinaustereenvironments.Soundanatomicknowledgeandagoodtechniquearesynonymous.Thelandmarksareobvious,butthissimpleprocedurebecomesanadventurewhenthelandmarksareS.D.Eyer,MDTobesuccessful,anintimatefamiliarityoftheunder-lyinglaryngealanatomyisessential.Tubemisplacementisthemainreasonforcricothyrotomyfailure.rectidentiÞcationoflandmarksisevenmoredifÞcultinaustereenvironmentsowingtolimitationsofsensoryperception,poorlighting,lackofequipment,andaddedenvironmentalstressors.Boonandothersstatethatsolidknowledgeoftheanatomyisimperativetolessencom-plications,andisakeycomponentinreducinganxietyamongproviders.Anatomicallandmarksforcricothyrotomyarelocatedintheanteriormidlineoftheneck.Fromsuperiortoinferiortheyareasfollows:1)hyoidbone;2)thyrohyoidmem-brane(alsoknownasthethyroidmembrane);3)thyroidnotch;4)thyroidcartilage;5)cricothyroidmembrane;and6)cricothyroidcartilageandsternalnotch(Figure1Inmostpatients,itisfairlyeasytopalpatethethyroidcartilage,particularlyinmales,whileslidingdownthemidlinewiththeindexÞngerfromthethyroidnotch(locatedonthesuperiorborderofthethyroidcartilage).Thecricothyroidmembraneislocatedjustinferiortothelargethyroidcartilageandsuperiortothecricothyroidcartilage.Theonlycompletecartilageringinthelarynxandtracheaisthecricothyroidcartilage,whichisimpor-tantforairwaypatencybeforeandparticularlyafteracricothyrotomy.Theselandmarksareeasiesttoidentifywhentheneckisextended. Figure1.Anatomyofthelarynx.HessertandBennett Elliotetalstudied18anesthesiologiststodeterminewhethertheycouldcorrectlylocatethecricothyroidmembraneon6adulthumanswithina10-secondperiod,simulatinganurgentcricothyrotomy.Theanesthesiolo-gistscorrectlyidentiÞedthecricothyroidmembraneonly30%ofthetime.TheseauthorsandotherssuggestthatultrasoundmayelucidatedifÞcultanatomyandensurecorrectcutaneouspointofentryoverlyingthecricothy-roidmembrane.UltrasoundÕsavailabilityforuseinaustereenvironmentsisincreasinginspeciÞcsettings,eg,disastermedicine,highaltitudeclinics,andmilitaryforwardaidstations,butnormallywouldnotbeavail-able.Itisimportanttonotethattheuseofultrasoundtoidentifyanatomicallandmarksforcricothyrotomyhasnotbeenvalidatedclinicallytoimprovesuccessrateanddecreasecomplications.Owingtosofttissueswellingfromtrauma,traditionalanatomicallandmarkscanbeverychallengingtofeel,whichmaydelayanemergentcricothyrotomy.forusewhenlandmarkscannotbepalpatedbecauseoftraumaorobesityarethatthecricothyroidmembranecanbefound1)approximately1to1.5Þngerbreadthsbelowthelaryngealprominence(thyroidcartilage)intheneckmidline;and2)4Þngerwidths(index,middle,ringÞnger,pinky)abovethesuperiorborderofthesternalThegenerallocationofthecricothyroidmembranecanalsobeapproximatedusingtheangleofthemandibleandhyoidbone.CRICOTHYROIDMEMBRANEThecricothyroidmembraneisadense,trapezoidalÞbro-elasticmembranebetweentheinferiorborderofthethyroidcartilageandthesuperiorborderofthecricothy-roidcartilage.Thecricothyroidmusclesborderthecri-cothyroidmembranelaterally.Theaveragedimensionsare8.2mmwideand10.4mmhigh,withwomenhavingconsistentlysmallercricothyroidmembranedimensionsthanmen.BasedonthissizethecricothyrotomytubeÕsoutermeasurementshouldnotexceed8mm.commercialkitsnowusea6-mmtube,smallenoughforeasyinsertionandreducedriskofcartilagefracture,whilestilllargeenoughforadequateventilation.Averticalmidlineincisionwillavoidallmajorvesselsoftheneck.Boonetalreportednomajorarteries,veins,ornervesinthecricothyroidmembraneregion,yetDo-veretalreportedextensivecollateralanastomosesinthearea.Interestingly,thecricothyroidarterytransversestheupperthirdofthecricothyroidmembranein93%of15cadavers.EventhoughthecricothyroidarteryisnotconsideredclinicallysigniÞcant,atransversestabthroughthelowerportionofthecricothyroidmembraneadjacenttothecricothyroidcartilageisrecommendedtoavoidthissmallartery.Thelocationofthecricothyroidarterymayaccountforthefactthatsomesurgicalcricothyrotomiesarebloodywhereasothersarenot.VOCALCORDSThevocalcordsareattachedtothethyroidcartilageandareatleast1cmsuperiortotheincisionthroughthecricothyroidmembrane.Tubeinsertionshouldbeaimedcaudallytoavoidinjuringthevocalcordsviaretrogradeintubation.Othercomplicationsrelatingtoanatomicalconsiderationsandthetechniquestoavoidthemarediscussedbelow.Incidence,Indications,andContraindicationsCricothyrotomyusagehasdecreasedduringthepast2decadesprimarilyintheED,inlargepartbecauseoflessinvasiveadjunctssuchasthelaryngealmaskairway,Combitube(Kendall-SheridanCatheterCorp,Argyle,NY),andKingLT.ThesesupraglotticdeviceshavereducedthenumberofpatientsintheÒcanÕtintubate,canÕtventilateÓ(CICV)category.Furthermore,theincreaseduseofneuromuscularblockingagentsforrapidsequenceinductionhasincreasedthesuccessofnonop-erativeairwaymanagement.Wallsetalreported8937intubationsacross31EDsbasedonamulticentertraumaregistryfromSeptember1997toJune2002.Ofthese,theneedforsurgicalcricothyrotomyoccurred17times(0.19%).ThislowincidenceofEDcricothyrotomyislessthanotherstudiesreporting1.7%to2.7%ofallattemptedintubations,and2.1%to14.9%ofattemptedintubationsintheprehospitalsetting.Acompromisedairwayisthethirdpotentiallypre-ventablecauseofdeathonthebattleÞeldandresultsin1%to2%ofallcombatfatalitiesinmodernmilitaryMabryandFrankfortstatethatthesurgicalcricothyrotomyprocedureincombatcasualtieshasamuchhigherincidencerateandisnearlydoublethatreportedforcivilians(0.32%vs0.62%oftraumaadmissions,respectively).Furthermore,theseauthorsstatethatairwaydeathsarelowcomparedwithhemor-rhageonthebattleÞeld.However,theimpactofairway-relatedinjuriesfrominadequateoxygenationandventi-lationisnotknown.Todate,therehasbeenonlyonecasereportofasurgicalcricothyrotomyperformedinthewildernessset-ting.WhartonandBennettreportedusingasurgicalEmergentSurgicalCricothyrotomy cricothyrotomyona31-year-oldrockclimberwhofell24.4m(80feet).Endotrachealintubationwasimpossibleowingtooropharyngealbleedingandfacialfractures,whichcreatedanunstableairwayespeciallywhenplacedinasupinepositionduringprolongedlitterevacuation.Mostlikelythereareothercasesinwhichasurgicalcricothyrotomyhasbeenimprovisedinawildernessset-ting,buttheyhavenotbeenreported.Commonindicationsforsurgicalairwayinterventioninanysituationareoropharyngealhemorrhage,edemaoftheglottis(asseenwithanaphylaxisorinhalationinju-ries),facialtrauma,anatomicabnormalities,trismus,orotherCICVscenarios.Traumaisbyfarthemostfrequentindication,reportedin82.4%to100%ofcricothy-rotomypatients.Fortuneetalretrospectivelyexamined15686traumacasesoverthecourseof5yearsinwhich376patientsrequiredprehospitaladvancedairwayintervention.Withinthisgroup,56patients(14.9%)re-ceivedaprehospitalcricothyrotomy,anunusuallyhighÞgurereportedforuseintheprehospitalsetting.The5leadingindicationsforcricothyrotomywerefacialfrac-tures(32%),bloodintheairway(30%),failedintubationattempt(11%),clenchedteeth(9%),andtraumaticair-wayobstruction(7%).McIntoshetalreportedsimilarÞndingsforuseofcricothyrotomybyemergencymedi-calservice(EMS)ßightcrews.Theneedforthisproce-dureexistsinthebackcountryforheadandfacialtrauma,airwayswellingforanaphylaxis,oranyotherincidentresultinginaCICVscenario.InastudybyAdamsetalfromOperationIraqiFreedom,5.8%ofthe293casualtiesneedingadvancedairwaysreceivedacricothyrotomy,andthevastmajority(97%)ofthosewhoneededairwayinterventionweretraumapatients.OtherdatabyMabryetalindicatethat18of982battleÞeldcasualtieshadairwaycompromiseasthemostlikelyprimarycauseofdeath.Ofthese18cases,allhadtraumaticinjurytothefaceandneck.Ninecasualtieshadmultipleinjuriestomajorvascularstruc-tureswithsigniÞcanthemorrhage.In5of9casesasurgicalcricothyrotomywasnotedatautopsy.Thechallengesofcombatandotherwildernesssitua-tions,suchaslongermedicalproceduretime,lightcon-orcomplicatedpositioningorextrication,maynecessitatecricothyrotomyvsconventionalairwaymanagement.Thus,theindicationsforcricothyrotomyinthesesettingsarebroaderthantheindicationswhenthisprocedureisusedinthehospital.Additionalpatient-relatedfactorsthatmayrequirecricothyrotomyintheaustereenvironmentincludesuspectedcervicalspinetraumaandaÒcrashingÓpatientwithoutintravenousac-cessalongwithoneormorephysiologicalindices(eg,Glasgowcomascore8,oxygensaturationsystolicbloodpressure80mmHg).Since1996,theTacticalCombatCasualtyCareguide-linesrecommendairwaymanagementwitheithermanualairwaymaneuvers,nasopharyngealairway,orcasualtyrecoveryposition.Whentheseeffortsareunsuccessful,asurgicalairwayshouldbeconsidered,butonlyafterallowingaconsciouspatienttomaintainhisownairwaybysittingandleaningforwardsoblooddrainsoutofhisApositionofcomfortshouldtakeprecedenceassupinepositioningmaycreateapreventableairwayemergency.Thissameapproachtoairwaymanagementhasbeenadoptedbythecivilianlawenforcementfortacticalemergencymedicalsupportandseemsappropriatetomostwildernesssettingsaswell.Thelossofairwaypatencyisnotcompatiblewithlife;thusitisgenerallystatedthattherearenoabsolutecontraindicationstocricothyrotomy.Theonlyabsolutecontraindicationtocricothyrotomyistheabilitytosecureanairwaywithlessinvasivemeans,butthisisnotalwaysanoptioninaustereenvironments.traumathatrenderscricothyrotomyahopelessproce-dure,suchastrachealtransectioninwhichthedistalendretractsintothemediastinumorasigniÞcantcricoidcartilageorlaryngealfracture,canalsobeabsolutecon-Relativecontraindicationstosurgicalcricothyrotomyincludemassiveswellingorobesitywithlossoflandmarks.Ageyoungerthan10to12yearsisacontraindicationbecauseanatomicalconsiderationsmakesurgicalcricothyrotomyextremelydifÞcult,chil-drenarepronetolaryngealtrauma,andtheyhaveahigherincidenceofpostoperativecomplicationsfromsurgicalcricothyrotomythanadults.Therefore,childrenshouldundergoneedlecricothyrotomyifnootherairwaycanbeobtained.CricothyrotomyProceduresandEquipmentTherearenumerousvariationsofcricothyrotomyequip-includingseveralcommerciallyavailablesetsforneedlepercutaneousandopensurgicalprocedures.Manyoftheseproceduresarehospital-basedtech-niquesandarebeyondthescopeofthisreview.Someoftheseprocedureshavemoretools,andthereforeadditionalstepstocompletetheprocedure,andarelesspracticalasdescribedforuseinaustereenviron-Table1providesalistingof12surgicalcrico-thyrotomyprocedures.13,20,32,37Ð45HessertandBennett Table1.Cricothyrotomyprocedures Surgicalprocedure1)Makealongitudinalmidlineincisionoverthecricoidmembrane;2)Identifythecricothyroidmembraneviabluntdissection;3)Makeashorttransversestabincisioninthelowerpartofthemembrane;4)Stabilizethelarynxwithatrachealhookattheinferioraspectofthethyroidcartilage;5)Dilatetheostomywithcurvedhemostats;6)PlaceTrousseaudilatorintheincisionandfurtherdilatetheostomy;7)Placetubeinthetrachea.Lefthandsecurestrachea;1)Makealongitudinalmidlineincisionoverthyroidandcricoidcartilagesfollowedbyatransversestabincisionthroughcricothyroidmembrane;2)Inserthandleintocricothyroidmembraneopeningandrotate90¡;3)Insert5.0-to6.0-mmtube,inßatecuffandsecure.Three-steptechniquewithgumbougie1)MakeamidlinelongitudinalincisionwithNo.20bladeovercricothyroidmembraneandusenondominantindexÞngertopalpatemembrane;2)Makea5-mmtransverseincisionthroughmembraneandinsertagumelasticbougieintotrachea;3)Placecuffed6.0-mmETtubeoverbougieandslideintotrachea;onceinplaceremovebougieandsecureETtube.Rapidfour-step1)Identifylandmarks;2)Maketransverseincisionthroughskinandcricothyroidmembraneintotrachea;3)Usetrachealhookwithtractiononcricoidcartilage;4)Inserttrachealtube,removehook,andsecuretube.Blindtechnique1)MakelongitudinalmidlineskinincisionoverthecricothyroidmembranewithaNo.11blade;2)GuidethescalpelcarefullyalongtheindexÞngerandmakeatransversestabthroughtheinferiorportionofthemembrane.3)IntroducethetracheotomytubeandstyletassemblybyslidingtheextendedstyletalongthevolarsurfaceoftheindexÞngerandinsertitintothesurgicaloswithoutremovaloftheÞnger;4)AdvancethetracheotomytubeastheÞngerisremoved;5)Removethestylet;6)Inßatecuff,ventilatelungs,ensurepropertubeplacement,andsecurethetube.ModiÞedsurgical1)StartonthepatientÕsrightside;2)StabilizethelarynxwithyourleftthumbandmiddleÞnger,anduseyourindexÞngertopalpatethethyroidcartilage.MoveyourindexÞngerinferiorlyuntilyoupalpatethecricoidcartilageandcricothyroidmembrane;3)Makealongitudinalmidlineincision;4)Usethecurvedhemostatforbluntdissectionthroughthesubcutaneoustissue;5)Makeatransverseincisionthroughthemembrane;6)Extendtheincisionlaterally;7)Insertatrachealhookandpullupwardonthedistalportionoftheincision,elevatingthelarynx;8)InsertaTrousseaudilator,theninsertthetracheostomytube;9)Removetheobturator,attachtheadapter,andinßatethecuff.WarSurgeryinAfghanistanand1)Identifythecricothyroidmembrane;2)Prepareskin;3)Graspandholdthetrachea;4)Makealongitudinalmidlineincision(No.10or11blade);5)Bluntlydissecttoexposethemembrane;6)Makeatransversemembraneincision;7)Openthemembranewithforceps;8)InsertacuffedETtube6.0Ð7.0mmandinßatecuff;9)Securetube.Emergencywarsurgerycourse1)Identifycricothyroidmembrane;2)Prepareskin;3)Graspandholdtracheauntilairwaycompletelyinplace;4)Makealongitudinalmidlineincisiontothelevelofthemembrane(No.10or11blade);5)Bluntlydissecttissuestoexposethemembrane;6)Makeatransversemembraneincision;7)Openthemembranewithforcepsorthescalpelhandle;8)Inserta6-to7-mmcuffedETtubetojustabovetheballoon;9)ConÞrmtrachealintubation;10)SuturetheETtubeinplaceandsecure.Paramedicprotocol1)Prepareskin;2)Locateanatomicallandmarks;3)Maketransverseincisionatcricothyroidmembrane;4)Openincisionatcricothyroidmembranewithscalpelhandleandrotatescalpel90¡;5)Insertcuffed6-to7-mmETtubeortracheostomytubeandsecure;6)Ventilate.AdvancedTraumaLifeSupportDescribestheuseofRapidfour-steptechniqueintheskillssection.DifÞcultAirwayDescribestheRapidfour-steptechniqueasstatedabove.TacticalCombatCasualtyCare1)Assembleandtestallnecessaryequipment;2)Identifythecricothyroidmembrane;3)Makealongitudinalmidlineincisionthroughskindirectlyoverthecricothyroidmembrane(atransverseincisionisanacceptablealternative);4)Usethescalpelorahemostattocutorpokethroughthecricothyroidmembrane;5)Insertthehemostatthroughandopenittodilatetheos(acrichookmayalsobeusedforthispurpose);6)InserttheETtubebetweentheendsofthehemostat;thetubeshouldbeinthetracheaanddirectedcaudally;9)Inßatethecuffandsecuretube.ET,endotracheal.EmergentSurgicalCricothyrotomy Initialsurgicalcricothyrotomyincisionsareeitherver-tical(longitudinal)orhorizontal(transverse)basedontheselectedprocedures.Techniqueisaproviderprefer-encebasedontraining,anatomicalknowledge,laryngealtrauma,andwhetherthereisalossofanatomicalland-marks.TheverticalmidlineincisionisnowthepreferredsurgicalcricothyrotomytechniqueonthebattleÞeld,aslossofanatomicallandmarksiscommon.Wangetalfoundthatreportscomparingthespeedofdifferenttechniqueswereinconclusive.However,when12studieswerecompared,mosttraditionalsurgicalcri-cothyrotomyproceduresorothersurgicalvariationswerefasterthan,orasfastas,percutaneoustechniques,withtheaveragespeed8344seconds(range,28Ð149Thesestudieswerenotstandardizedforproviderlevel,airwayexperience,procedure,ormodel.Werecommendthe3-stepprocedureasfast,simple,andeasytoperformwithbasictoolseveninremoteorausterelocations.ImprovisedCricothyrotomyTheequipmentinvariouscommercialcricothyrotomykitscanbecomplicated.andprovidersmayprefermorefamiliarbasictools.Moreover,awildernessproviderisunlikelytohaveaÒcricothyrotomykitÓandmorelikelytohaveassembledhisorherownmultipurposeequip-ment.Austereenvironmentsnecessitateingenuityandcreativitytoovercomelackofresourcesorenvironmen-talchallenges.AdamsandWhitlockemphasizeuseofequipmentthatoptimizesÒergonomics,simplicity,andreliability,Óespeciallyinacombatscenario;thisequipmentmayincludeitemsnottraditionallyusedformedicalprocedures.TheCommitteeonTacticalCombatCasualtyCarepublishedalistofpreferredcricothy-rotomykitfeaturesthatmaybeapplicabletoprovidersinotheraustereenvironments.Smallcommercialkits(NorthAmericanRescue,TacticalMedicalSolutions,andH&HAssociates)targetedformilitaryandlawen-forcementpersonnelareidealforanyaustereenviron-mentmedicalprovider.Publishedcasesindicatethatmanyeverydayobjectscanbeusedforcricothyrotomy.InthewordsofDrNancyShannon,ÒaÞeldexpedienttubeorobjectmaybeReportedobjectsincludeasportbottledrinkamodiÞednasalspeculum,acutoffsyringebarrel(3mLwith7.0ETtubeadapter),intravenoustubingchamberwithspike,ETtubes,specializedkeychains,andothers.TheLifestatkeychain(FrenchPocketAirway,Inc,NewOrleans,LA)isaspeciallydesigneddevicewithbuilt-introchar,can-nula,andadapterpiecesforÞeld-expedientcricothy-rotomy.Thisdevicecanbeusedforpediatricpatientsaswellasadults.Inasmallretrospectivereview,itwasplacedcorrectlyin17of17patientswithnocomplica-Prolongeduseofballpointpensmaybeusedsuccess-fullyforcricothyrotomytubedeviceifthelumenisgreaterthan4mm.Owensetaltested8commonlyavailablepensforairwayresistanceatvariousairßowratesandspeedofdisassemblyforfashioninganairwaytube.The2pensultimatelydeemedacceptableweretheBaronretractableballpointpenandtheBicSoftFeelJumbo.Althoughurbanlegendandtheaforementionedstudyindicatethatonecanperformacricothyrotomywithaballpointpenbarrel,therehavenotbeenanypublishedcasereportstodate.Alsocommerciallyavail-ableareconvenientpenlikedevicesspeciÞcallydesignedforcricothyrotomy,WadhwaEmergencyAirwayDevice(CookCriticalCare,Bloomington,IN).Similarly,recentworkbyMichalek-Saubereretalexamineddifferentcricothyrotomydevicesinacontrolledlungmodelforcomplianceandresistanceofairwaydevicediameters.Theyreportedthataspikeanddripchamberdeviceforanimprovisedairway,previouslydocumentedbyHu-doesnotprovideeffectiveventilation.ThedeviceÕsinnerdiameterneedstobeatleast4mm,conÞrm-ingtheresultsofOwensetal.Theyalsofoundthatcuffedcricothyrotomydevices,whichpreventairleak-agearoundthetube,areessentialforbestventilation.BecauseairßowresistanceisinverselyproportionaltothelumenÕsradiustakentothefourthpower(PoiseuilleÕslaw[R],whereRisresistance,lislength,isviscosity,andrisradius),adecreasinglumensizedecreasesventilationexponentially.Thus,smalleritemscanonlybeusedasabridgetodeÞnitiveairwayman-agement,astheyprovideoxygenationbutnotventila-tion.Theintravenoustubingchamberwithspike,de-scribedabove,hasbeendocumentedinacaseserieswithgoodresultswhencombinedwithajetventilator.personcanbreathspontaneouslythroughasmallcatheterafterpercutaneousneedlecricothyrotomy.Oncethemajorgoalofopeningtheairwayisaccomplished,manydifferenttoolscanbeusedtoprovidevaryingdegreesofoxygenationandventilation.Ontheotherhand,ScraseandWoollarddocumentedtheinadequacyofneedlecricothyrotomywithlow-pressureventilationaswouldtypicallybethecaseinwildernesssituations.However,needlecricothyrotomycanbequicklyandeasilycon-vertedtosurgicalcricothyrotomy.Inoneseries,11of17needlecricothyrotomiesrequiredconversiontosurgicalSeveralauthorshavedevisedcricothyrotomytech-niquestoovercomemassiveswelling,morbidobesity,orcompletedarkness.IntheÒblindtechnique,ÓtheprovidermakesaverticalmidlineincisionanddissectsuntilHessertandBennett thelandmarksarepalpable,andthenmakesahorizontalstabthroughthecricothyroidmembrane.Abent14-gaugeneedletipcanbeusedasacricothyrotomyhook,andahemostatcanbeusedtodilatethemembraneopening.Othertechniquesforrapid,reliableplacementinthesettingofobscuredanatomyareinsertionofaßexibleETtubestyletintothetracheawithatubeÒrailroadedÓoverit,oruseofacutdown6.0-mmETtubewithapreloadedstyletsecuredjustbeyondthetip,whichisinsertedasaunitbeforeremovingthestylet.Morrisetandothers50,69Ð71havedescribedthebougieasasimilarcricothyrotomyintroducerwithgoodresult.Thebougiemayevenassistcricothyrotomywhenwearingnight-visiongoggles,althoughcloserangevisualacuitywithnight-visiongogglesposeschallengesonitsown.Awildernessprovidermaybeabletoimproviseoneofthesetechniqueswiththetoolsonhand.SuccessRatesInthecivilianprehospitalenvironment,surgicalcrico-thyrotomyisrelativelyfast,safe,andhighlysuccess-especiallyconsideringthatitisinfrequentlyperformed,invasive,emergent,andoftenperformedinsuboptimalconditionswithverybasicequipment.presentcricothyrotomysuccessratesfor13EMSßightcrewsstudies31,72Ð83and11EMSground2,4,6Ð8,12,33,68,84Ð86Ameta-analysisbyHubbleetalindicatesa90.5%successrateinaprehospitalcricothyrotomyseriesof485patientsacross18studies.Groundandaeromedicalteamsperformedsimilarly(90.8%and90.9%successrates,respectively).Interestingly,needlecricothyrotomyinprehospitalstudieshadamuchlowerpooledsuccessratethansurgicalcricothyrotomy(65.8%;range,25.0%Ð76.9%vs.90.5%;range,83.3%Ð97.1%)despitebeinglessinvasive.Table2a.Successratesforßightemergencymedicalservicecricothyrotomystudies StudyProviderNo.ofsurgicalcricothyrotomiesSuccessfulMcIntoshetal,2008Flightnurseor1717(100%)Boyleetal,Flightnurse6968(98.5%)Salvinoetal,Flightnurse1010(100%)Nugentetal,Flightnurse5553(96%)Bairetal,Flightnurse2222(100%)etal,1111(100%)Robinsonetal,2001Flightnurseor85(63%)Miklusetal,Physicianor2019(91%)Germannetal,2009Flightnurse,66(100%)BrownandFlightnurse,22(100%)Cooketal,Flightmedics6867(99%)Thomasetal,1999Flightnurse,87(87.5%)Brownetal,Flightcrew296287(97%)Table2b.SuccessratesforÞeldemergencymedicalservicecricothyrotomystudies StudyProviderNo.ofsurgicalcricothyrotomiesSuccessfulLeibovicietal,Physicians2926(90%)Warner,20091110(90%)4needle1(25%)Spaiteand1614(88%)Morrisetal,22(100%)Adamsetal,Medic,PA,1713(77%)Jacobsenetal,Paramedics5047(94%)Leibovicietal,IDFmilitary2623(88.4%)PriceandPhysicians9393(100%)Metzgeretal,11(100%)Fortuneetal,Paramedic5648(89%)Oliveretal,Paramedic10082(85%)Total405360(89)%ALS,advancedlifesupport;CRNA,CertiÞedRegisteredNurseAnesthetist;IDF,IsraelDefenseForces;PA,physicianassistant;TEMS,TacticalEmergencyMedicalSupport.EmergentSurgicalCricothyrotomy relates2majorproblemswhenperforminganemergentcricothyrotomythatcanaffectsuccessrates:1)thestressoftheoperatorowingtothelife-threateningnatureofthesituation;and2)anatomicaldistortionscausedbyinjury.ThedeÞnitionofasuccessfulcricothy-rotomyisatubethattransversesthecricothyroidmem-branewiththedistalendinthetrachea.Positivepatientoutcomeisnotarequirementforproceduralsuccess,asalargenumberofthesepatientswilldiedespiteprompt,properairwaycontrol.MabryandFrankfurtreportedtheÞrstretrospectiveanalysisoftheJointTheaterTraumaRegistry,whichrevealed72cricothyrotomiesperformedonthebattle-Þeld(45)oratbattalionaidstations(27)duringa22-monthperiodduringOperationEnduringFreedom(Afghanistan)andOperationIraqiFreedom(Iraq).Theyfoundthatprehospitalcricothyrotomybymedics(per-sonneltrainedtoanEmergencyMedicalTechnician-Basiclevel)wassuccessfulin62%ofthecases,although33%wereincorrectlyplaced.Thisfailurerateis3-to5-foldhighercomparedwithcivilianprehospitalstudies(personneltrainedtoanEmergencyMedicalTechnician-Paramediclevel).Additionaldatarevealeda77%suc-cessand15%failureratesbyjuniorphysiciansandphysicianassistantsworkingatbattalionaidstations.Theseauthorsconcludethatadditionalsolutionsareneededtomasterthisprocedure.Complicationsarereportedtooccurin18%ofcricothy-ProceduresintheÞeldaremorepronetocomplicationsthanin-hospitalproceduresowingtoin-clementweather,poorlighting,inabilitytomaintainasterileÞeld,positioningofpatientandrescuer,tacticalenvironment,andlackofequipment.Bairetalcomplicationsin14%and54%ofallhospitalandÞeldcricothyrotomies,respectively.Inthisstudy,thehighrateofÞeldcomplicationscouldbeattributedtoattemptstakingmorethan2minutes.Complicationscanbegroupedbyimmediatevs.de-layedandmajorvs.minor.Emergencycareprovidersaremostconcernedwithimmediatecomplicationsbecausetheyhavetobehandledstraightaway.Notableimmediatecomplicationsincludemisplacedincision(leadingcom-plicationinmilitaryandciviliandata)withincorrectplacementthroughthethyrohyoid(thyroid)mem-iatrogenicinjurytothethyroidorcricothyroidcartilagewhenusingacricothyrotomyhook,aspi-rationofbloodorvomitus,tubeocclusionwithfalsepassage,retrogradeintubation,stemintubation,excessiveedema,hemorrhageorhematomaformation,posteriortracheallaceration,inadvertentextubation,andothers.Thereareseveralstrategiestoremedyormitigatethesecomplications.Thoroughanatomicalknowledgeanduseofultrasoundhelpidentifylandmarks.Ifanincisionismisplaced,provideditislongitudinalmidline,itcanbeextendedsuperiorlyorinferiorly.Toavoidcausinginjurytothevocalcords,useasmallcricothy-rotomyhookandpullinferiorlyonthecricothyroid,orpullsuperiorlyonthelargerthyroidcartilage.Bothcar-tilageswillfractureiftoomuchforceisappliedwitheitherahookoranoversizeETtube.NostudieshaveconÞrmedthepotentialproblemoftearingtheETtubecuffwithahook.HemorrhagecanbeminimizedwithasuperÞcialskinincisionandbluntdissectiontothecricothyroidmem-brane.Ahorizontalstabmadethroughtheinferiorcri-cothyroidmembraneavoidsthenearbycricothyroidar-Ifhemorrhageoccurs,usedirectpressuretostopit.Avertposteriortracheallacerationusingextracaution,anangledscalpelpositionwhenstabbingthecricothy-roidmembrane,andadepthnogreaterthan13mm.PreventionofETtubemainstemintubationcanbeavoidedbyadvancingthetubenofartherthanlossofsightoftheballoon.Maintainmanualcontrolofthetubeuntilsecuredwithagirthhitcharoundthetubeatthemidpointofapproximately30inchesofrollergauze.UsethelongtailstowrapbehindthepatientÕsneckandtieÞrmlybackontheETtube.Ifmainstemintubationhasoccurred,retractthetubeuntilbilateralchestmovementandbreathsoundsareappreciated,thenresecure.TominimizefalsepassagealwayskeepaninstrumentorÞngerinthetracheaoncepercutaneousaccesshasbeenachieved.Watchthetubepassthroughthetrachealring.Whenavailable,abougieorstyletintroducercanalsopreventfalsepassage.Therareretrogradecricothyrotomyhasonlybeenreportedbutcareshouldbetakentoanglethetubeinferiorlyoninsertion.Ifedemarendersthestandard2-to3-inchtracheos-tomytubetooshorttoreachthetrachea,ordislodgesitasswellingincreases,anETtubemaybeused.delayedswellingoccurs,swapthetracheostomytubeoverabougieandreplacewithanETtube.Useofsuction,ifavailable,mayreducetheriskofaspiration.AbougiecanbeusedtodislodgeclotsfromETtubesoccludedbybloodwhensuctionisnotavailable.CricothyrotomyTrainingInfrequentproceduresneedfrequenttraining.—S.D.Eyer,HessertandBennett Elliottetalstateoneofthemainreasonsforcricothyrotomyfailureisthelackofclinicalexperience.Therefore,cricothyrotomyrequiresregularrefreshertrainingforskillmaintenance.Mostcricothyrotomytrainingusessimulation,self-madetrainers,mannequins,cadavers,oranimalmodels.Eachtrainingmodalityhasstrengthsandlimitations;acommonproblemisthatlow-stressandlow-tomedium-Þdelitycricothy-rotomysimulationonlypreparesprovidersforthestep-by-stepprocedure,andnottheemergent,high-stressapplicationofthisskillwhenneeded.Thus,themosteffectivemethodofcricothyrotomytrainingisunknown.Commonquestionsaskedarewhatistheminimumtrain-ingfrequencyneededandwhichtrainingmodelprovidesthebestskillpreparation?Alimitednumberofqualitystudieshaveaddressedthesequestions.Wongetalrecommendatleast5cricothyrotomyattemptsoraconsistentproceduretimeof40secondsorless.Minimumtrainingof5attemptswasalsoreportedbyGreifetal.Recently,Siuetalreportedthatdespitestandardizedtraining,providerageandyearsfromresidencywereassociatedwithdecreasedBennettetalconductedabottom-upreviewofsurgicalcricothyrotomytrainingaspartofatacticalcombatcasualtycare4-daycourse.ThisstudywasinitiatedbasedonbattleÞeldlessonslearned,whichindicatedasigniÞcant26%overallfailurerateacrossallprovidersattemptingemergentcricothyrotomy.Thisstudyindicated5deÞciencies:1)limitedgrossanatomyreview;2)lackofÒhands-onÓhumanlaryngealanatomypractice;3)nonstandardizedcricothyrotomyequipmentandproce-dures;4)inferiormannequinsforlaryngealanatomy;and5)lackofrefreshertrainingfrequency.TheseauthorsTable3.Recommendationsforsurgicalcricothyrotomyprinciples,procedures,andtraining Minimallevelprovidersshouldbemilitarymedicsandcivilianparamedics.Protocolsalreadyexistattheseproviderlevelsformilitaryandcivilianprehospitalproviders.TeachcriticalairwayanatomicalAnessentialpartofcricothyrotomytrainingisthekeyanatomicallandmarksÑuse3Danimationvideosand3Dlaryngealairwaymodel.Usewashablemarkerstoidentifythecriticalanatomicallandmarks.Palpateall6criticalanatomicalUseextensivehands-onpalpationusingrole-playingpatientsinvaryingagegroupsandgendersinvariousbodypositionswithandwithouttheuseofvisualaids.Selectthe3-stepprocedurewith6.0-mmETtube,No.20scalpel,ÒcricÓhook,andagumbougieorstyletinducerFigure2A3-stepprocedurewithabougieorstyletinducerusesminimalstepsandtools.Itisafastandeffectivetechniquetogainaccessintothetrachea.ANo.20scalpelisthewidthofa6.0-mmtube.UseanatomicallycorrectairwaymannequinsandprogresstocadaverswithÞnalevaluationusinglive-tissueTheprogressionofcricothyrotomytrainingmodelsfrommannequinstolive-tissuemodelsisrecommended.Thissupportsinitialskilldevelopmentbeforetransitiontomoreclinicalrealismwithcadaverandlive-tissuetraining.Feedbackfrommilitarymedicssupportsthisprogressionoftrainingasessentialforsuccessowingtolackofclinicaltrainingopportunities.Use5Ð10trainingsessions,ensuringallcriticalstepsareperformedsuccessfully60seconds.The2studiessupporttheuseof10cricothyrotomytrainingsessionsorfewerifskillperformancelevelsoff.Thesestudiesjustifythenumberoftrainingsessions.Createahigh-Þdelitysimulationenvironment(indoor/outdoors)speciÞctofutureproviderroles,eg,marine,aviation,battleÞeld,wilderness,tacticalEMS,etc.Thebestwaytotrainforsuccessistodevelopoperationalmedicalscenariosclosesttotherelevantaustereenvironmentthatonewillbeexposedto.Progresswithsinglecricothyrotomyprocedureinamedicalscenario,thentransitiontomultipleinjuriesandmultiplepatients.Thistrainingwillimproveskillprogressionanddecisionmakinginamedicalscenarioowingtomultipletaskloading.Seekthesamesuccessrateandperformancetimeachievedinthelaboratory.Refreshertrainingatleastevery6months.Variousstudiessupporttheneedofrefreshertrainingatleastevery6monthsorassituationalrequirementsdemandtomaintainhighskillretentionandproÞciency.EmergentSurgicalCricothyrotomy alsoprovidednovelstep-by-stepcricothyrotomytrainingLimitationstotheuseofmannequincricothyrotomytrainersincludesynthetictissuetexture;poorlydevel-opedlaryngealanatomy,particularlyincorrectdimen-sions;andnoreplicationofcomplications.Forthesereasons,aswellasthelackofcricothyrotomyskillapplicationintheclinicalsetting,manyhaveusedlive-tissueanimalmodels.57,95,98Ð101Live-tissueanimalmodelsprovidereal-timeandrealisticfeedbackincludinghypoxia,irregularrespirations,andbleed-ing.Alternatively,theuseoffreshorpreservedhumancadavermodelsmoreaccuratelyreßectscorrectair-wayanatomyandsometissuecharacteristics.Nonani-malsimulationcurrentlydoesnotprovidetherealismorphysiologicalresponsesinsufÞcientÞdelitytore-placelive-tissuetraining.Theuseoflive-tissuetrain-ingfordevelopingenhancedcognitiveÞtnessandpsy-chologicalresiliencefromexposuretotraumaticeventsisalsoveryimportant.Afollow-upquestionaboutcricothyrotomytrainingishowtomaintainaskillthatisrarelyused.Wongetfoundthata1-monthrefresherintervalwassuperiortoa3-monthintervalforskillmaintenance.Apaneldiscussionconveyedastrongconsensusthatsurgicalcricothyrotomyprovidersshouldhaverefreshertrainingevery6monthsattheminimum.Morerecently,Kudavillietalevaluatedcricothyrotomyskillsevaluationatbaseline,6to8weeks,and6to8monthsandconcludedthatsimulation-basedcricothyrotomytrainingoname-dium-Þdelitysimulatorenhancedperformanceatweeks6to8,butnotbeyond,andrecommendedrefreshertrainingatleastevery6months.Table3providesrecommendationsandsupportingjus-tiÞcationforsurgicalcricothyrotomyprinciples,proce-dures,andtrainingintheaustereenvironment.Therec-ommendedfastandsimplecricothyrotomy3-stepprocedurealgorithmisoutlinedinFigure2,andisde-velopedbasedonthestudiesbyMacIntyreetal,Giacomoetal,andothers.50,69Ð71Rigorousattentionto Place casualty supine with neck in neutral position and start at right side of patient for right hand dominant provider Casualty Assessment Indications for surgical cricothyroidotomy Assemble equipment and prep the skin.Palpate the thyroid notch, thyroid and cricoidcartilages, cricoid membrane With the nondominanthand stabilize the trachea and keep the skin taut over the thyroid cartilage With right hand make a 1.0-inchvertical (longitudinal) incision midline through tissueswith No. 20scalpel blade Place 6.0-mmcuffed tube over the bougie and down into the trachea; remove bougie Inflate tube, assess air movement,and secure with roller gauze using a girth hitch, tape,or a commercial device Ongoing casualty monitoring Insert gum bougie inducer into trachea and use side of scalpel blade as guide into trachea. Remove scalpel while holding bougie firmly Make a horizontal (transverse)stab roid membranewith No.20 blade Figure2.Recommended3-stepcricothyrotomyalgorithm.HessertandBennett theserecommendationswilloptimizesuccessandmini-mizecomplicationsinaustereenvironments.Cricothyrotomyintheaustereenvironmentmayseemlikeaformidablechallengeanditis;yet,itcanbeachievedwiththerightpreparation.Emergencymedicalprovidersmusthaveastrategyreadyforuseatamo-mentÕsnoticewhenfacedwithacriticalpatientwhohasanunsecuredairwayandmeetstheindicationsorphys-iologictriggersforcricothyrotomy.Afastandsimple3-stepsurgicalcricothyrotomyprocedurewithmultipur-posetoolsisappropriateintheaustereenvironmentfortrainedmedicalproviderswithsoundanatomicalknowl-edge(Table1Figure2).Trainingshouldprogressfromlaboratory-basedskillspracticetoamorestressful,high-Þdelityscenario-basedtrainerwithsemiannualrefreshertraining.Acombinationofanatomicalknowledge,famil-iaritywithproceduresandequipment,andtheconÞdencetomakethedecisiontoperformcricothyrotomywithtroubleshootingandimprovisationasnecessarywillim-proveprovidercomfort,optimizecricothyrotomysuc-cess,andultimatelysavelives.1.McSwainN.Thescienceandartofprehospitalcare:principles,preferencesandcriticalthinking.In:SalomoneJ,PonsP,McSwainN,eds.PrehospitalTraumaLifeSupportManual.7thed.St.Louis,MO:Elsevier;2011;34Ð35.2.JacobsenLE,GomezGA,SobierayRJ,RodmanGH,SolotkinKC,MisinskiME.Surgicalcricothyroidotomyintraumapatients:analysisofitsusebyparamedicsintheJTrauma.1996;41:15Ð20.3.OrebaughSL.DifÞcultairwaymanagementintheemer-gencydepartment.JEmergMed.2002;22:31Ð48.4.WarnerKJ,ShararSR,CopassMK,BulgerEM.Prehos-pitalmanagementofadifÞcultairway:aprospectivecohortstudy.JEmergMed.2009;36:257Ð265.5.WallsRM.Cricothyroidotomy.EmergMedClinNorth.1988;6:725Ð736.6.FortuneJB,JudkinsDG,ScanzaroliD,McLeodKB,JohnsonSB.EfÞcacyofprehospitalsurgicalcricothy-rotomyintraumapatients.JTrauma.1997;42:835.7.SpaiteDW,JosephM.Prehospitalcricothyrotomy:aninvestigationofindications,technique,complications,andpatientoutcome.AnnEmergMed.1990;19:279Ð285.8.AdamsBD,CuniowskiPA,MuckA,DeLorenzoRA.Registryofemergencyairwaysarrivingatcombathospi-JTrauma.2008;64:1548Ð1554.9.MabryRL,EdensJWPearseL,KellyJF,HarkeH.FatalairwayinjuriesduringOperationEnduringFreedomandOperationIraqiFreedom.PrehospEmergCare10.ButlerFKJr,HagmannJ,ButlerEG.Tacticalcombatcasualtycareinspecialoperations.MilMed.1996;11.CommitteeonTacticalCombatCasualtyCare.MilitaryMedicine.In:ButlerFK,GiebnerS,eds.PrehospitalTraumaLifeSupportManual.7thed.(MilitaryVersion),St.Louis,MO:Elsevier;2011:591Ð750.12.MetzgerJC,EastmanAL,BenitezFL,PepePE.Thelifesavingpotentialofspecializedon-scenemedicalsup-portforurbantacticaloperations.PrehospEmergCare2009;13:528Ð531.13.ElliottDSJ,BakerPA,ScottMR,BirchCW,ThompsonJMD.AccuracyofsurfacelandmarkidentiÞcationforcannulacricothyroidotomy..2010;65:889Ð894.14.BennettBL,Cailteux-ZevallosB,KotoraJ.Cricothyroid-otomybottomÐuptrainingreview:battleÞeldlessonsMilMed.2011;176:1311Ð1319.15.BoonJM,AbrahamsPH,MeiringJH,WelchT.Cricothyroidotomy:aclinicalanatomyreview.ClinAnat2004;17:478Ð486.16.DoverK,HowdieshellTR,ColbornGL.Thedimensionsandvascularanatomyofthecricothyroidmembrane:rel-evancetoemergentsurgicalairwayaccess.ClinAnat17.HelmM,GriesA,MutzbauerT.SurgicalapproachindifÞcultairwaymanagement.BestPractResClinAnaes-.2005;19:623Ð640.18.NichollsSE,SweeneyTW,FerreRM,StroutTD.Bed-sidesonographybyemergencyphysiciansfortherapididentiÞcationoflandmarksrelevanttocricothyrotomy.AmJEmergMed.2008;26:852Ð856.19.ArchanS,PrauseG,GumpertR,SeibertFJ,KŸglerB.CricothyroidotomyonthesceneinapatientwithseverefacialtraumaanddifÞcultneckanatomy.AmJEmerg.2009;27:133.e1Ð4.20.Emergencysurgicalairwaymanagement.In:NessenSC,LounsburyDE,HetzSP,eds.WarSurgeryinAfghanistanandIraq,ASeriesofCases,2003–2007.Washington,D.C.:OfÞceoftheSurgeonGeneral,UnitedStatesArmy,BordenInstitute,2008:24Ð27.21.SimonRR,BrennerBE.Emergencycricothyroidotomyinthepatientwithmassiveneckswelling:part1:anatomicalCritCareMed.1983;11:114Ð118.22.Theclinicalanatomyofseveralinvasiveprocedu-res.AmericanAssociationofClinicalAnatomists,EducationalAffairsCommittee.ClinAnat.1999;12:23.ChangRS,HamiltonRJ,CarterWA.Decliningrateofcricothyrotomyintraumapatientswithanemergencymedicineresidency:implicationsforskillstraining.EmergMed.1998;5:247Ð251.24.BerkowLC,GreenbergRS,KanKH,etal.NeedforemergencysurgicalairwayreducedbyacomprehensiveEmergentSurgicalCricothyrotomy 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REVIEWARTICLEOptimizingEmergentSurgicalCricothyrotomyforuseinAustereEnvironmentsM.JosephineHessert,DO,MPH;BradL.Bennett,PhD,MA,EMT-PFromtheDepartmentofEmergencyMedicine,NavalMedicalCenterPortsmouth,Portsmouth,VA(DrHessert);andtheDepartmentofMilitaryandEmergencyMedicine,F.EdwardHébertSchoolofMedicine,UniformedServicesUniversityoftheHealthSciences,Bethesda,MD(DrBennett). Asurgicalcricothyrotomyisalmostalwaysaprocedureoflastresortbecauseofitsinvasivenessandprovidercomfortorlackthereof.Mostpatientswhorequirecricothyrotomyintheemergencydepartment(ED)havefailedmultipleETintubationattemptsandarepossi-blycriticallyhypoxic,requiringfurtherintervention.Intheprehospitalsetting,mostcricothyrotomycandidateshaveeithercardiacarrestorblunttraumaandfailedETintuba-tionattempts.Survivorsfrequentlyhavepoorneurologicaloutcomeandhighmortalityrates.Inausteresettings,theuseofETintubationandsupraglotticdevicesmaynotbepossibleorappropriatebecauseoftacticalorsituationalconstraints,evenwhenappropriateforthepatient.Thus,cricothyrotomyisevenmorerelevantintheseenviron-9Ð12Althoughcricothyrotomyisbecominglesscommonasotheralternativeairwaydevicesareintroduced,suchasthelaryngealmaskairway,KingLT-D(KingSystemsCorp,Noblesville,IN),andothersupraglotticdevices,thereis,andlikelyalwayswillbe,aroleforcricothy-rotomyinasubsectionofpatientswithdifÞcultairways,especiallyinenvironmentsinwhichsuchdevicesareunlikelytobeavailable.Acommonemergencymedicineaphorismis:ÒIfyoudoonecricothyrotomy,youÕreahero;ifyoudotwo,workonyourairwayskills.ÓTrueperhapsinahospital,butinanaustereenvironmentmanyfactorsbesidesfailedETintubationleadtoearlycricothyrotomy.Wildernessprovidersmustbenotonlytechnicallyskilled,butalsoadequatelytrainedtorecog-nizethekeyindicationsandsituationaldecisiontriggersforcricothyrotomythatdifferfromin-hospitalpractice.Researchoncricothyrotomyvariesintermsofthepro-ceduresandtoolsevaluated.Additionally,outcomessuchasproceduretime,successrates,andcomplications,aswellasothervariables(eg,trainingmodels,researchenvironments,providerlevelandspecialty,andpatient-relatedfactors)arenotuniformacrossstudies.Furthermore,cricothyrotomyis,atmost,aninfrequentlyperformedprocedure,andresearchontraumaandemergentpatientsisexceedinglydifÞcult.Casestudiesandretrospectiveanalysesabound,buttherearefewprospective,randomized,controlled,crossoverstudies.Thisreviewwillfocusonsurgicalcricothyrotomyoutsidethehospitalsetting,butdrawfromhospital-basedstudieswhenrelevanttotheperformanceofthisprocedureinaustereenvironments.Soundanatomicknowledgeandagoodtechniquearesynonymous.Thelandmarksareobvious,butthissimpleprocedurebecomesanadventurewhenthelandmarksareS.D.Eyer,MDTobesuccessful,anintimatefamiliarityoftheunder-lyinglaryngealanatomyisessential.Tubemisplacementisthemainreasonforcricothyrotomyfailure.rectidentiÞcationoflandmarksisevenmoredifÞcultinaustereenvironmentsowingtolimitationsofsensoryperception,poorlighting,lackofequipment,andaddedenvironmentalstressors.Boonandothersstatethatsolidknowledgeoftheanatomyisimperativetolessencom-plications,andisakeycomponentinreducinganxietyamongproviders.Anatomicallandmarksforcricothyrotomyarelocatedintheanteriormidlineoftheneck.Fromsuperiortoinferiortheyareasfollows:1)hyoidbone;2)thyrohyoidmem-brane(alsoknownasthethyroidmembrane);3)thyroidnotch;4)thyroidcartilage;5)cricothyroidmembrane;and6)cricothyroidcartilageandsternalnotch(Figure1Inmostpatients,itisfairlyeasytopalpatethethyroidcartilage,particularlyinmales,whileslidingdownthemidlinewiththeindexÞngerfromthethyroidnotch(locatedonthesuperiorborderofthethyroidcartilage).Thecricothyroidmembraneislocatedjustinferiortothelargethyroidcartilageandsuperiortothecricothyroidcartilage.Theonlycompletecartilageringinthelarynxandtracheaisthecricothyroidcartilage,whichisimpor-tantforairwaypatencybeforeandparticularlyafteracricothyrotomy.Theselandmarksareeasiesttoidentifywhentheneckisextended. Figure1.Anatomyofthelarynx.HessertandBennett Table1.Cricothyrotomyprocedures Surgicalprocedure1)Makealongitudinalmidlineincisionoverthecricoidmembrane;2)Identifythecricothyroidmembraneviabluntdissection;3)Makeashorttransversestabincisioninthelowerpartofthemembrane;4)Stabilizethelarynxwithatrachealhookattheinferioraspectofthethyroidcartilage;5)Dilatetheostomywithcurvedhemostats;6)PlaceTrousseaudilatorintheincisionandfurtherdilatetheostomy;7)Placetubeinthetrachea.Lefthandsecurestrachea;1)Makealongitudinalmidlineincisionoverthyroidandcricoidcartilagesfollowedbyatransversestabincisionthroughcricothyroidmembrane;2)Inserthandleintocricothyroidmembraneopeningandrotate90¡;3)Insert5.0-to6.0-mmtube,inßatecuffandsecure.Three-steptechniquewithgumbougie1)MakeamidlinelongitudinalincisionwithNo.20bladeovercricothyroidmembraneandusenondominantindexÞngertopalpatemembrane;2)Makea5-mmtransverseincisionthroughmembraneandinsertagumelasticbougieintotrachea;3)Placecuffed6.0-mmETtubeoverbougieandslideintotrachea;onceinplaceremovebougieandsecureETtube.Rapidfour-step1)Identifylandmarks;2)Maketransverseincisionthroughskinandcricothyroidmembraneintotrachea;3)Usetrachealhookwithtractiononcricoidcartilage;4)Inserttrachealtube,removehook,andsecuretube.Blindtechnique1)MakelongitudinalmidlineskinincisionoverthecricothyroidmembranewithaNo.11blade;2)GuidethescalpelcarefullyalongtheindexÞngerandmakeatransversestabthroughtheinferiorportionofthemembrane.3)IntroducethetracheotomytubeandstyletassemblybyslidingtheextendedstyletalongthevolarsurfaceoftheindexÞngerandinsertitintothesurgicaloswithoutremovaloftheÞnger;4)AdvancethetracheotomytubeastheÞngerisremoved;5)Removethestylet;6)Inßatecuff,ventilatelungs,ensurepropertubeplacement,andsecurethetube.ModiÞedsurgical1)StartonthepatientÕsrightside;2)StabilizethelarynxwithyourleftthumbandmiddleÞnger,anduseyourindexÞngertopalpatethethyroidcartilage.MoveyourindexÞngerinferiorlyuntilyoupalpatethecricoidcartilageandcricothyroidmembrane;3)Makealongitudinalmidlineincision;4)Usethecurvedhemostatforbluntdissectionthroughthesubcutaneoustissue;5)Makeatransverseincisionthroughthemembrane;6)Extendtheincisionlaterally;7)Insertatrachealhookandpullupwardonthedistalportionoftheincision,elevatingthelarynx;8)InsertaTrousseaudilator,theninsertthetracheostomytube;9)Removetheobturator,attachtheadapter,andinßatethecuff.WarSurgeryinAfghanistanand1)Identifythecricothyroidmembrane;2)Prepareskin;3)Graspandholdthetrachea;4)Makealongitudinalmidlineincision(No.10or11blade);5)Bluntlydissecttoexposethemembrane;6)Makeatransversemembraneincision;7)Openthemembranewithforceps;8)InsertacuffedETtube6.0Ð7.0mmandinßatecuff;9)Securetube.Emergencywarsurgerycourse1)Identifycricothyroidmembrane;2)Prepareskin;3)Graspandholdtracheauntilairwaycompletelyinplace;4)Makealongitudinalmidlineincisiontothelevelofthemembrane(No.10or11blade);5)Bluntlydissecttissuestoexposethemembrane;6)Makeatransversemembraneincision;7)Openthemembranewithforcepsorthescalpelhandle;8)Inserta6-to7-mmcuffedETtubetojustabovetheballoon;9)ConÞrmtrachealintubation;10)SuturetheETtubeinplaceandsecure.Paramedicprotocol1)Prepareskin;2)Locateanatomicallandmarks;3)Maketransverseincisionatcricothyroidmembrane;4)Openincisionatcricothyroidmembranewithscalpelhandleandrotatescalpel90¡;5)Insertcuffed6-to7-mmETtubeortracheostomytubeandsecure;6)Ventilate.AdvancedTraumaLifeSupportDescribestheuseofRapidfour-steptechniqueintheskillssection.DifÞcultAirwayDescribestheRapidfour-steptechniqueasstatedabove.TacticalCombatCasualtyCare1)Assembleandtestallnecessaryequipment;2)Identifythecricothyroidmembrane;3)Makealongitudinalmidlineincisionthroughskindirectlyoverthecricothyroidmembrane(atransverseincisionisanacceptablealternative);4)Usethescalpelorahemostattocutorpokethroughthecricothyroidmembrane;5)Insertthehemostatthroughandopenittodilatetheos(acrichookmayalsobeusedforthispurpose);6)InserttheETtubebetweentheendsofthehemostat;thetubeshouldbeinthetracheaanddirectedcaudally;9)Inßatethecuffandsecuretube.ET,endotracheal.EmergentSurgicalCricothyrotomy Initialsurgicalcricothyrotomyincisionsareeitherver-tical(longitudinal)orhorizontal(transverse)basedontheselectedprocedures.Techniqueisaproviderprefer-encebasedontraining,anatomicalknowledge,laryngealtrauma,andwhetherthereisalossofanatomicalland-marks.TheverticalmidlineincisionisnowthepreferredsurgicalcricothyrotomytechniqueonthebattleÞeld,aslossofanatomicallandmarksiscommon.Wangetalfoundthatreportscomparingthespeedofdifferenttechniqueswereinconclusive.However,when12studieswerecompared,mosttraditionalsurgicalcri-cothyrotomyproceduresorothersurgicalvariationswerefasterthan,orasfastas,percutaneoustechniques,withtheaveragespeed8344seconds(range,28Ð149Thesestudieswerenotstandardizedforproviderlevel,airwayexperience,procedure,ormodel.Werecommendthe3-stepprocedureasfast,simple,andeasytoperformwithbasictoolseveninremoteorausterelocations.ImprovisedCricothyrotomyTheequipmentinvariouscommercialcricothyrotomykitscanbecomplicated.andprovidersmayprefermorefamiliarbasictools.Moreover,awildernessproviderisunlikelytohaveaÒcricothyrotomykitÓandmorelikelytohaveassembledhisorherownmultipurposeequip-ment.Austereenvironmentsnecessitateingenuityandcreativitytoovercomelackofresourcesorenvironmen-talchallenges.AdamsandWhitlockemphasizeuseofequipmentthatoptimizesÒergonomics,simplicity,andreliability,Óespeciallyinacombatscenario;thisequipmentmayincludeitemsnottraditionallyusedformedicalprocedures.TheCommitteeonTacticalCombatCasualtyCarepublishedalistofpreferredcricothy-rotomykitfeaturesthatmaybeapplicabletoprovidersinotheraustereenvironments.Smallcommercialkits(NorthAmericanRescue,TacticalMedicalSolutions,andH&HAssociates)targetedformilitaryandlawen-forcementpersonnelareidealforanyaustereenviron-mentmedicalprovider.Publishedcasesindicatethatmanyeverydayobjectscanbeusedforcricothyrotomy.InthewordsofDrNancyShannon,ÒaÞeldexpedienttubeorobjectmaybeReportedobjectsincludeasportbottledrinkamodiÞednasalspeculum,acutoffsyringebarrel(3mLwith7.0ETtubeadapter),intravenoustubingchamberwithspike,ETtubes,specializedkeychains,andothers.TheLifestatkeychain(FrenchPocketAirway,Inc,NewOrleans,LA)isaspeciallydesigneddevicewithbuilt-introchar,can-nula,andadapterpiecesforÞeld-expedientcricothy-rotomy.Thisdevicecanbeusedforpediatricpatientsaswellasadults.Inasmallretrospectivereview,itwasplacedcorrectlyin17of17patientswithnocomplica-Prolongeduseofballpointpensmaybeusedsuccess-fullyforcricothyrotomytubedeviceifthelumenisgreaterthan4mm.Owensetaltested8commonlyavailablepensforairwayresistanceatvariousairßowratesandspeedofdisassemblyforfashioninganairwaytube.The2pensultimatelydeemedacceptableweretheBaronretractableballpointpenandtheBicSoftFeelJumbo.Althoughurbanlegendandtheaforementionedstudyindicatethatonecanperformacricothyrotomywithaballpointpenbarrel,therehavenotbeenanypublishedcasereportstodate.Alsocommerciallyavail-ableareconvenientpenlikedevicesspeciÞcallydesignedforcricothyrotomy,WadhwaEmergencyAirwayDevice(CookCriticalCare,Bloomington,IN).Similarly,recentworkbyMichalek-Saubereretalexamineddifferentcricothyrotomydevicesinacontrolledlungmodelforcomplianceandresistanceofairwaydevicediameters.Theyreportedthataspikeanddripchamberdeviceforanimprovisedairway,previouslydocumentedbyHu-doesnotprovideeffectiveventilation.ThedeviceÕsinnerdiameterneedstobeatleast4mm,conÞrm-ingtheresultsofOwensetal.Theyalsofoundthatcuffedcricothyrotomydevices,whichpreventairleak-agearoundthetube,areessentialforbestventilation.BecauseairßowresistanceisinverselyproportionaltothelumenÕsradiustakentothefourthpower(PoiseuilleÕslaw[R],whereRisresistance,lislength,isviscosity,andrisradius),adecreasinglumensizedecreasesventilationexponentially.Thus,smalleritemscanonlybeusedasabridgetodeÞnitiveairwayman-agement,astheyprovideoxygenationbutnotventila-tion.Theintravenoustubingchamberwithspike,de-scribedabove,hasbeendocumentedinacaseserieswithgoodresultswhencombinedwithajetventilator.personcanbreathspontaneouslythroughasmallcatheterafterpercutaneousneedlecricothyrotomy.Oncethemajorgoalofopeningtheairwayisaccomplished,manydifferenttoolscanbeusedtoprovidevaryingdegreesofoxygenationandventilation.Ontheotherhand,ScraseandWoollarddocumentedtheinadequacyofneedlecricothyrotomywithlow-pressureventilationaswouldtypicallybethecaseinwildernesssituations.However,needlecricothyrotomycanbequicklyandeasilycon-vertedtosurgicalcricothyrotomy.Inoneseries,11of17needlecricothyrotomiesrequiredconversiontosurgicalSeveralauthorshavedevisedcricothyrotomytech-niquestoovercomemassiveswelling,morbidobesity,orcompletedarkness.IntheÒblindtechnique,ÓtheprovidermakesaverticalmidlineincisionanddissectsuntilHessertandBennett thelandmarksarepalpable,andthenmakesahorizontalstabthroughthecricothyroidmembrane.Abent14-gaugeneedletipcanbeusedasacricothyrotomyhook,andahemostatcanbeusedtodilatethemembraneopening.Othertechniquesforrapid,reliableplacementinthesettingofobscuredanatomyareinsertionofaßexibleETtubestyletintothetracheawithatubeÒrailroadedÓoverit,oruseofacutdown6.0-mmETtubewithapreloadedstyletsecuredjustbeyondthetip,whichisinsertedasaunitbeforeremovingthestylet.Morrisetandothers50,69Ð71havedescribedthebougieasasimilarcricothyrotomyintroducerwithgoodresult.Thebougiemayevenassistcricothyrotomywhenwearingnight-visiongoggles,althoughcloserangevisualacuitywithnight-visiongogglesposeschallengesonitsown.Awildernessprovidermaybeabletoimproviseoneofthesetechniqueswiththetoolsonhand.SuccessRatesInthecivilianprehospitalenvironment,surgicalcrico-thyrotomyisrelativelyfast,safe,andhighlysuccess-especiallyconsideringthatitisinfrequentlyperformed,invasive,emergent,andoftenperformedinsuboptimalconditionswithverybasicequipment.presentcricothyrotomysuccessratesfor13EMSßightcrewsstudies31,72Ð83and11EMSground2,4,6Ð8,12,33,68,84Ð86Ameta-analysisbyHubbleetalindicatesa90.5%successrateinaprehospitalcricothyrotomyseriesof485patientsacross18studies.Groundandaeromedicalteamsperformedsimilarly(90.8%and90.9%successrates,respectively).Interestingly,needlecricothyrotomyinprehospitalstudieshadamuchlowerpooledsuccessratethansurgicalcricothyrotomy(65.8%;range,25.0%Ð76.9%vs.90.5%;range,83.3%Ð97.1%)despitebeinglessinvasive.Table2a.Successratesforßightemergencymedicalservicecricothyrotomystudies StudyProviderNo.ofsurgicalcricothyrotomiesSuccessfulMcIntoshetal,2008Flightnurseor1717(100%)Boyleetal,Flightnurse6968(98.5%)Salvinoetal,Flightnurse1010(100%)Nugentetal,Flightnurse5553(96%)Bairetal,Flightnurse2222(100%)etal,1111(100%)Robinsonetal,2001Flightnurseor85(63%)Miklusetal,Physicianor2019(91%)Germannetal,2009Flightnurse,66(100%)BrownandFlightnurse,22(100%)Cooketal,Flightmedics6867(99%)Thomasetal,1999Flightnurse,87(87.5%)Brownetal,Flightcrew296287(97%)Table2b.SuccessratesforÞeldemergencymedicalservicecricothyrotomystudies StudyProviderNo.ofsurgicalcricothyrotomiesSuccessfulLeibovicietal,Physicians2926(90%)Warner,20091110(90%)4needle1(25%)Spaiteand1614(88%)Morrisetal,22(100%)Adamsetal,Medic,PA,1713(77%)Jacobsenetal,Paramedics5047(94%)Leibovicietal,IDFmilitary2623(88.4%)PriceandPhysicians9393(100%)Metzgeretal,11(100%)Fortuneetal,Paramedic5648(89%)Oliveretal,Paramedic10082(85%)Total405360(89)%ALS,advancedlifesupport;CRNA,CertiÞedRegisteredNurseAnesthetist;IDF,IsraelDefenseForces;PA,physicianassistant;TEMS,TacticalEmergencyMedicalSupport.EmergentSurgicalCricothyrotomy relates2majorproblemswhenperforminganemergentcricothyrotomythatcanaffectsuccessrates:1)thestressoftheoperatorowingtothelife-threateningnatureofthesituation;and2)anatomicaldistortionscausedbyinjury.ThedeÞnitionofasuccessfulcricothy-rotomyisatubethattransversesthecricothyroidmem-branewiththedistalendinthetrachea.Positivepatientoutcomeisnotarequirementforproceduralsuccess,asalargenumberofthesepatientswilldiedespiteprompt,properairwaycontrol.MabryandFrankfurtreportedtheÞrstretrospectiveanalysisoftheJointTheaterTraumaRegistry,whichrevealed72cricothyrotomiesperformedonthebattle-Þeld(45)oratbattalionaidstations(27)duringa22-monthperiodduringOperationEnduringFreedom(Afghanistan)andOperationIraqiFreedom(Iraq).Theyfoundthatprehospitalcricothyrotomybymedics(per-sonneltrainedtoanEmergencyMedicalTechnician-Basiclevel)wassuccessfulin62%ofthecases,although33%wereincorrectlyplaced.Thisfailurerateis3-to5-foldhighercomparedwithcivilianprehospitalstudies(personneltrainedtoanEmergencyMedicalTechnician-Paramediclevel).Additionaldatarevealeda77%suc-cessand15%failureratesbyjuniorphysiciansandphysicianassistantsworkingatbattalionaidstations.Theseauthorsconcludethatadditionalsolutionsareneededtomasterthisprocedure.Complicationsarereportedtooccurin18%ofcricothy-ProceduresintheÞeldaremorepronetocomplicationsthanin-hospitalproceduresowingtoin-clementweather,poorlighting,inabilitytomaintainasterileÞeld,positioningofpatientandrescuer,tacticalenvironment,andlackofequipment.Bairetalcomplicationsin14%and54%ofallhospitalandÞeldcricothyrotomies,respectively.Inthisstudy,thehighrateofÞeldcomplicationscouldbeattributedtoattemptstakingmorethan2minutes.Complicationscanbegroupedbyimmediatevs.de-layedandmajorvs.minor.Emergencycareprovidersaremostconcernedwithimmediatecomplicationsbecausetheyhavetobehandledstraightaway.Notableimmediatecomplicationsincludemisplacedincision(leadingcom-plicationinmilitaryandciviliandata)withincorrectplacementthroughthethyrohyoid(thyroid)mem-iatrogenicinjurytothethyroidorcricothyroidcartilagewhenusingacricothyrotomyhook,aspi-rationofbloodorvomitus,tubeocclusionwithfalsepassage,retrogradeintubation,stemintubation,excessiveedema,hemorrhageorhematomaformation,posteriortracheallaceration,inadvertentextubation,andothers.Thereareseveralstrategiestoremedyormitigatethesecomplications.Thoroughanatomicalknowledgeanduseofultrasoundhelpidentifylandmarks.Ifanincisionismisplaced,provideditislongitudinalmidline,itcanbeextendedsuperiorlyorinferiorly.Toavoidcausinginjurytothevocalcords,useasmallcricothy-rotomyhookandpullinferiorlyonthecricothyroid,orpullsuperiorlyonthelargerthyroidcartilage.Bothcar-tilageswillfractureiftoomuchforceisappliedwitheitherahookoranoversizeETtube.NostudieshaveconÞrmedthepotentialproblemoftearingtheETtubecuffwithahook.HemorrhagecanbeminimizedwithasuperÞcialskinincisionandbluntdissectiontothecricothyroidmem-brane.Ahorizontalstabmadethroughtheinferiorcri-cothyroidmembraneavoidsthenearbycricothyroidar-Ifhemorrhageoccurs,usedirectpressuretostopit.Avertposteriortracheallacerationusingextracaution,anangledscalpelpositionwhenstabbingthecricothy-roidmembrane,andadepthnogreaterthan13mm.PreventionofETtubemainstemintubationcanbeavoidedbyadvancingthetubenofartherthanlossofsightoftheballoon.Maintainmanualcontrolofthetubeuntilsecuredwithagirthhitcharoundthetubeatthemidpointofapproximately30inchesofrollergauze.UsethelongtailstowrapbehindthepatientÕsneckandtieÞrmlybackontheETtube.Ifmainstemintubationhasoccurred,retractthetubeuntilbilateralchestmovementandbreathsoundsareappreciated,thenresecure.TominimizefalsepassagealwayskeepaninstrumentorÞngerinthetracheaoncepercutaneousaccesshasbeenachieved.Watchthetubepassthroughthetrachealring.Whenavailable,abougieorstyletintroducercanalsopreventfalsepassage.Therareretrogradecricothyrotomyhasonlybeenreportedbutcareshouldbetakentoanglethetubeinferiorlyoninsertion.Ifedemarendersthestandard2-to3-inchtracheos-tomytubetooshorttoreachthetrachea,ordislodgesitasswellingincreases,anETtubemaybeused.delayedswellingoccurs,swapthetracheostomytubeoverabougieandreplacewithanETtube.Useofsuction,ifavailable,mayreducetheriskofaspiration.AbougiecanbeusedtodislodgeclotsfromETtubesoccludedbybloodwhensuctionisnotavailable.CricothyrotomyTrainingInfrequentproceduresneedfrequenttraining.—S.D.Eyer,HessertandBennett Elliottetalstateoneofthemainreasonsforcricothyrotomyfailureisthelackofclinicalexperience.Therefore,cricothyrotomyrequiresregularrefreshertrainingforskillmaintenance.Mostcricothyrotomytrainingusessimulation,self-madetrainers,mannequins,cadavers,oranimalmodels.Eachtrainingmodalityhasstrengthsandlimitations;acommonproblemisthatlow-stressandlow-tomedium-Þdelitycricothy-rotomysimulationonlypreparesprovidersforthestep-by-stepprocedure,andnottheemergent,high-stressapplicationofthisskillwhenneeded.Thus,themosteffectivemethodofcricothyrotomytrainingisunknown.Commonquestionsaskedarewhatistheminimumtrain-ingfrequencyneededandwhichtrainingmodelprovidesthebestskillpreparation?Alimitednumberofqualitystudieshaveaddressedthesequestions.Wongetalrecommendatleast5cricothyrotomyattemptsoraconsistentproceduretimeof40secondsorless.Minimumtrainingof5attemptswasalsoreportedbyGreifetal.Recently,Siuetalreportedthatdespitestandardizedtraining,providerageandyearsfromresidencywereassociatedwithdecreasedBennettetalconductedabottom-upreviewofsurgicalcricothyrotomytrainingaspartofatacticalcombatcasualtycare4-daycourse.ThisstudywasinitiatedbasedonbattleÞeldlessonslearned,whichindicatedasigniÞcant26%overallfailurerateacrossallprovidersattemptingemergentcricothyrotomy.Thisstudyindicated5deÞciencies:1)limitedgrossanatomyreview;2)lackofÒhands-onÓhumanlaryngealanatomypractice;3)nonstandardizedcricothyrotomyequipmentandproce-dures;4)inferiormannequinsforlaryngealanatomy;and5)lackofrefreshertrainingfrequency.TheseauthorsTable3.Recommendationsforsurgicalcricothyrotomyprinciples,procedures,andtraining Minimallevelprovidersshouldbemilitarymedicsandcivilianparamedics.Protocolsalreadyexistattheseproviderlevelsformilitaryandcivilianprehospitalproviders.TeachcriticalairwayanatomicalAnessentialpartofcricothyrotomytrainingisthekeyanatomicallandmarksÑuse3Danimationvideosand3Dlaryngealairwaymodel.Usewashablemarkerstoidentifythecriticalanatomicallandmarks.Palpateall6criticalanatomicalUseextensivehands-onpalpationusingrole-playingpatientsinvaryingagegroupsandgendersinvariousbodypositionswithandwithouttheuseofvisualaids.Selectthe3-stepprocedurewith6.0-mmETtube,No.20scalpel,ÒcricÓhook,andagumbougieorstyletinducerFigure2A3-stepprocedurewithabougieorstyletinducerusesminimalstepsandtools.Itisafastandeffectivetechniquetogainaccessintothetrachea.ANo.20scalpelisthewidthofa6.0-mmtube.UseanatomicallycorrectairwaymannequinsandprogresstocadaverswithÞnalevaluationusinglive-tissueTheprogressionofcricothyrotomytrainingmodelsfrommannequinstolive-tissuemodelsisrecommended.Thissupportsinitialskilldevelopmentbeforetransitiontomoreclinicalrealismwithcadaverandlive-tissuetraining.Feedbackfrommilitarymedicssupportsthisprogressionoftrainingasessentialforsuccessowingtolackofclinicaltrainingopportunities.Use5Ð10trainingsessions,ensuringallcriticalstepsareperformedsuccessfully60seconds.The2studiessupporttheuseof10cricothyrotomytrainingsessionsorfewerifskillperformancelevelsoff.Thesestudiesjustifythenumberoftrainingsessions.Createahigh-Þdelitysimulationenvironment(indoor/outdoors)speciÞctofutureproviderroles,eg,marine,aviation,battleÞeld,wilderness,tacticalEMS,etc.Thebestwaytotrainforsuccessistodevelopoperationalmedicalscenariosclosesttotherelevantaustereenvironmentthatonewillbeexposedto.Progresswithsinglecricothyrotomyprocedureinamedicalscenario,thentransitiontomultipleinjuriesandmultiplepatients.Thistrainingwillimproveskillprogressionanddecisionmakinginamedicalscenarioowingtomultipletaskloading.Seekthesamesuccessrateandperformancetimeachievedinthelaboratory.Refreshertrainingatleastevery6months.Variousstudiessupporttheneedofrefreshertrainingatleastevery6monthsorassituationalrequirementsdemandtomaintainhighskillretentionandproÞciency.EmergentSurgicalCricothyrotomy alsoprovidednovelstep-by-stepcricothyrotomytrainingLimitationstotheuseofmannequincricothyrotomytrainersincludesynthetictissuetexture;poorlydevel-opedlaryngealanatomy,particularlyincorrectdimen-sions;andnoreplicationofcomplications.Forthesereasons,aswellasthelackofcricothyrotomyskillapplicationintheclinicalsetting,manyhaveusedlive-tissueanimalmodels.57,95,98Ð101Live-tissueanimalmodelsprovidereal-timeandrealisticfeedbackincludinghypoxia,irregularrespirations,andbleed-ing.Alternatively,theuseoffreshorpreservedhumancadavermodelsmoreaccuratelyreßectscorrectair-wayanatomyandsometissuecharacteristics.Nonani-malsimulationcurrentlydoesnotprovidetherealismorphysiologicalresponsesinsufÞcientÞdelitytore-placelive-tissuetraining.Theuseoflive-tissuetrain-ingfordevelopingenhancedcognitiveÞtnessandpsy-chologicalresiliencefromexposuretotraumaticeventsisalsoveryimportant.Afollow-upquestionaboutcricothyrotomytrainingishowtomaintainaskillthatisrarelyused.Wongetfoundthata1-monthrefresherintervalwassuperiortoa3-monthintervalforskillmaintenance.Apaneldiscussionconveyedastrongconsensusthatsurgicalcricothyrotomyprovidersshouldhaverefreshertrainingevery6monthsattheminimum.Morerecently,Kudavillietalevaluatedcricothyrotomyskillsevaluationatbaseline,6to8weeks,and6to8monthsandconcludedthatsimulation-basedcricothyrotomytrainingoname-dium-Þdelitysimulatorenhancedperformanceatweeks6to8,butnotbeyond,andrecommendedrefreshertrainingatleastevery6months.Table3providesrecommendationsandsupportingjus-tiÞcationforsurgicalcricothyrotomyprinciples,proce-dures,andtrainingintheaustereenvironment.Therec-ommendedfastandsimplecricothyrotomy3-stepprocedurealgorithmisoutlinedinFigure2,andisde-velopedbasedonthestudiesbyMacIntyreetal,Giacomoetal,andothers.50,69Ð71Rigorousattentionto Place casualty supine with neck in neutral position and start at right side of patient for right hand dominant provider Casualty Assessment Indications for surgical cricothyroidotomy Assemble equipment and prep the skin.Palpate the thyroid notch, thyroid and cricoidcartilages, cricoid membrane With the nondominanthand stabilize the trachea and keep the skin taut over the thyroid cartilage With right hand make a 1.0-inchvertical (longitudinal) incision midline through tissueswith No. 20scalpel blade Place 6.0-mmcuffed tube over the bougie and down into the trachea; remove bougie Inflate tube, assess air movement,and secure with roller gauze using a girth hitch, tape,or a commercial device Ongoing casualty monitoring Insert gum bougie inducer into trachea and use side of scalpel blade as guide into trachea. Remove scalpel while holding bougie firmly Make a horizontal (transverse)stab roid membranewith No.20 blade Figure2.Recommended3-stepcricothyrotomyalgorithm.HessertandBennett theserecommendationswilloptimizesuccessandmini-mizecomplicationsinaustereenvironments.Cricothyrotomyintheaustereenvironmentmayseemlikeaformidablechallengeanditis;yet,itcanbeachievedwiththerightpreparation.Emergencymedicalprovidersmusthaveastrategyreadyforuseatamo-mentÕsnoticewhenfacedwithacriticalpatientwhohasanunsecuredairwayandmeetstheindicationsorphys-iologictriggersforcricothyrotomy.Afastandsimple3-stepsurgicalcricothyrotomyprocedurewithmultipur-posetoolsisappropriateintheaustereenvironmentfortrainedmedicalproviderswithsoundanatomicalknowl-edge(Table1Figure2).Trainingshouldprogressfromlaboratory-basedskillspracticetoamorestressful,high-Þdelityscenario-basedtrainerwithsemiannualrefreshertraining.Acombinationofanatomicalknowledge,famil-iaritywithproceduresandequipment,andtheconÞdencetomakethedecisiontoperformcricothyrotomywithtroubleshootingandimprovisationasnecessarywillim-proveprovidercomfort,optimizecricothyrotomysuc-cess,andultimatelysavelives.1.McSwainN.Thescienceandartofprehospitalcare:principles,preferencesandcriticalthinking.In:SalomoneJ,PonsP,McSwainN,eds.PrehospitalTraumaLifeSupportManual.7thed.St.Louis,MO:Elsevier;2011;34Ð35.2.JacobsenLE,GomezGA,SobierayRJ,RodmanGH,SolotkinKC,MisinskiME.Surgicalcricothyroidotomyintraumapatients:analysisofitsusebyparamedicsintheJTrauma.1996;41:15Ð20.3.OrebaughSL.DifÞcultairwaymanagementintheemer-gencydepartment.JEmergMed.2002;22:31Ð48.4.WarnerKJ,ShararSR,CopassMK,BulgerEM.Prehos-pitalmanagementofadifÞcultairway:aprospectivecohortstudy.JEmergMed.2009;36:257Ð265.5.WallsRM.Cricothyroidotomy.EmergMedClinNorth.1988;6:725Ð736.6.FortuneJB,JudkinsDG,ScanzaroliD,McLeodKB,JohnsonSB.EfÞcacyofprehospitalsurgicalcricothy-rotomyintraumapatients.JTrauma.1997;42:835.7.SpaiteDW,JosephM.Prehospitalcricothyrotomy:aninvestigationofindications,technique,complications,andpatientoutcome.AnnEmergMed.1990;19:279Ð285.8.AdamsBD,CuniowskiPA,MuckA,DeLorenzoRA.Registryofemergencyairwaysarrivingatcombathospi-JTrauma.2008;64:1548Ð1554.9.MabryRL,EdensJWPearseL,KellyJF,HarkeH.FatalairwayinjuriesduringOperationEnduringFreedomandOperationIraqiFreedom.PrehospEmergCare10.ButlerFKJr,HagmannJ,ButlerEG.Tacticalcombatcasualtycareinspecialoperations.MilMed.1996;11.CommitteeonTacticalCombatCasualtyCare.MilitaryMedicine.In:ButlerFK,GiebnerS,eds.PrehospitalTraumaLifeSupportManual.7thed.(MilitaryVersion),St.Louis,MO:Elsevier;2011:591Ð750.12.MetzgerJC,EastmanAL,BenitezFL,PepePE.Thelifesavingpotentialofspecializedon-scenemedicalsup-portforurbantacticaloperations.PrehospEmergCare2009;13:528Ð531.13.ElliottDSJ,BakerPA,ScottMR,BirchCW,ThompsonJMD.AccuracyofsurfacelandmarkidentiÞcationforcannulacricothyroidotomy..2010;65:889Ð894.14.BennettBL,Cailteux-ZevallosB,KotoraJ.Cricothyroid-otomybottomÐuptrainingreview:battleÞeldlessonsMilMed.2011;176:1311Ð1319.15.BoonJM,AbrahamsPH,MeiringJH,WelchT.Cricothyroidotomy:aclinicalanatomyreview.ClinAnat2004;17:478Ð486.16.DoverK,HowdieshellTR,ColbornGL.Thedimensionsandvascularanatomyofthecricothyroidmembrane:rel-evancetoemergentsurgicalairwayaccess.ClinAnat17.HelmM,GriesA,MutzbauerT.SurgicalapproachindifÞcultairwaymanagement.BestPractResClinAnaes-.2005;19:623Ð640.18.NichollsSE,SweeneyTW,FerreRM,StroutTD.Bed-sidesonographybyemergencyphysiciansfortherapididentiÞcationoflandmarksrelevanttocricothyrotomy.AmJEmergMed.2008;26:852Ð856.19.ArchanS,PrauseG,GumpertR,SeibertFJ,KŸglerB.CricothyroidotomyonthesceneinapatientwithseverefacialtraumaanddifÞcultneckanatomy.AmJEmerg.2009;27:133.e1Ð4.20.Emergencysurgicalairwaymanagement.In:NessenSC,LounsburyDE,HetzSP,eds.WarSurgeryinAfghanistanandIraq,ASeriesofCases,2003–2007.Washington,D.C.:OfÞceoftheSurgeonGeneral,UnitedStatesArmy,BordenInstitute,2008:24Ð27.21.SimonRR,BrennerBE.Emergencycricothyroidotomyinthepatientwithmassiveneckswelling:part1:anatomicalCritCareMed.1983;11:114Ð118.22.Theclinicalanatomyofseveralinvasiveprocedu-res.AmericanAssociationofClinicalAnatomists,EducationalAffairsCommittee.ClinAnat.1999;12:23.ChangRS,HamiltonRJ,CarterWA.Decliningrateofcricothyrotomyintraumapatientswithanemergencymedicineresidency:implicationsforskillstraining.EmergMed.1998;5:247Ð251.24.BerkowLC,GreenbergRS,KanKH,etal.NeedforemergencysurgicalairwayreducedbyacomprehensiveEmergentSurgicalCricothyrotomy 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93.SiuLW,BoetS,BorgesBC,etal.High-Þdelitysimula-tiondemonstratestheinßuenceofanesthesiologistsÕageandyearsfromresidencyonemergencycricothyroid-otomyskills.AnesthAnalg.2010;111:955Ð960.94.VaradaySS,YentisSM,ClarkeS.Ahomemademodelfortrainingincricothyrotomy..2004;59:95.CustalowCB,KlineJA,MarxJA,BaylorMR.Emer-gencydepartmentresuscitativeprocedures:animallabo-ratorytrainingimprovesproceduralcompetencyandAcadEmergMed.2002;9:575Ð586.96.WongDT,PrabhuAJ,ColomaM,ImasogieN,ChungFF.Whatistheminimumtrainingrequiredforsuccessfulcricothyroidotomy?:astudyinmannequins..2003;98:349Ð353.97.GreifR,EggerL,BascianiRM,LockeyA,VogtA.EmergencyskilltrainingÑarandomizedcontrolledstudyontheeffectivenessofthe4-stageapproachcomparedtotraditionalclinicalteaching..2010;81:98.EatonBD,MessentDO,HaywoodIR.Animalcadavericmodelsforadvancedtraumalifesupporttraining.AnnRCollSurgEngl.1990;72:135Ð139.99.McCarthyMC,RanzingerMR,NolanDJ,LambertCS,CastilloMH.Accuracyofcricothyroidotomyperformedincanineandhumancadavermodelsduringsurgicalskillstraining.JAmCollSurg.2002;195:627Ð629.100.SohnVY,MillerJP,KoellerCA,etal.Fromthecombatmedictotheforwardsurgicalteam:theMadiganmodelforimprovingtraumareadinessofbrigadecombatteamsÞghtingtheGlobalWaronTerror.JSurgRes.2007;138:101.GerhardtRT,HermstadEL,OakesM,WiegertRS,OliverJ.Anexperimentalpredeploymenttrainingprogramim-provesself-reportedpatienttreatmentconÞdenceandpre-parednessofArmycombatmedics.PrehospEmergCare2008;12:359Ð365.102.KudavalliPM,JervisA,TigheSQM,RobinNM.Unan-ticipateddifÞcultairwaymanagementinanesthetizedpatients:aprospectivestudyoftheeffectofmannequintrainingonmanagementstrategiesandskillretention..2008;63:64Ð69.103.PrabhuAJ,CorreaR,WongDT,McGuireG,ChungF.Whatistheoptimaltrainingintervalforacricothyroid-otomy?[abstract].CanJAnesth.2001;48:A59.HessertandBennett cricothyrotomyona31-year-oldrockclimberwhofell24.4m(80feet).Endotrachealintubationwasimpossibleowingtooropharyngealbleedingandfacialfractures,whichcreatedanunstableairwayespeciallywhenplacedinasupinepositionduringprolongedlitterevacuation.Mostlikelythereareothercasesinwhichasurgicalcricothyrotomyhasbeenimprovisedinawildernessset-ting,buttheyhavenotbeenreported.Commonindicationsforsurgicalairwayinterventioninanysituationareoropharyngealhemorrhage,edemaoftheglottis(asseenwithanaphylaxisorinhalationinju-ries),facialtrauma,anatomicabnormalities,trismus,orotherCICVscenarios.Traumaisbyfarthemostfrequentindication,reportedin82.4%to100%ofcricothy-rotomypatients.Fortuneetalretrospectivelyexamined15686traumacasesoverthecourseof5yearsinwhich376patientsrequiredprehospitaladvancedairwayintervention.Withinthisgroup,56patients(14.9%)re-ceivedaprehospitalcricothyrotomy,anunusuallyhighÞgurereportedforuseintheprehospitalsetting.The5leadingindicationsforcricothyrotomywerefacialfrac-tures(32%),bloodintheairway(30%),failedintubationattempt(11%),clenchedteeth(9%),andtraumaticair-wayobstruction(7%).McIntoshetalreportedsimilarÞndingsforuseofcricothyrotomybyemergencymedi-calservice(EMS)ßightcrews.Theneedforthisproce-dureexistsinthebackcountryforheadandfacialtrauma,airwayswellingforanaphylaxis,oranyotherincidentresultinginaCICVscenario.InastudybyAdamsetalfromOperationIraqiFreedom,5.8%ofthe293casualtiesneedingadvancedairwaysreceivedacricothyrotomy,andthevastmajority(97%)ofthosewhoneededairwayinterventionweretraumapatients.OtherdatabyMabryetalindicatethat18of982battleÞeldcasualtieshadairwaycompromiseasthemostlikelyprimarycauseofdeath.Ofthese18cases,allhadtraumaticinjurytothefaceandneck.Ninecasualtieshadmultipleinjuriestomajorvascularstruc-tureswithsigniÞcanthemorrhage.In5of9casesasurgicalcricothyrotomywasnotedatautopsy.Thechallengesofcombatandotherwildernesssitua-tions,suchaslongermedicalproceduretime,lightcon-orcomplicatedpositioningorextrication,maynecessitatecricothyrotomyvsconventionalairwaymanagement.Thus,theindicationsforcricothyrotomyinthesesettingsarebroaderthantheindicationswhenthisprocedureisusedinthehospital.Additionalpatient-relatedfactorsthatmayrequirecricothyrotomyintheaustereenvironmentincludesuspectedcervicalspinetraumaandaÒcrashingÓpatientwithoutintravenousac-cessalongwithoneormorephysiologicalindices(eg,Glasgowcomascore8,oxygensaturationsystolicbloodpressure80mmHg).Since1996,theTacticalCombatCasualtyCareguide-linesrecommendairwaymanagementwitheithermanualairwaymaneuvers,nasopharyngealairway,orcasualtyrecoveryposition.Whentheseeffortsareunsuccessful,asurgicalairwayshouldbeconsidered,butonlyafterallowingaconsciouspatienttomaintainhisownairwaybysittingandleaningforwardsoblooddrainsoutofhisApositionofcomfortshouldtakeprecedenceassupinepositioningmaycreateapreventableairwayemergency.Thissameapproachtoairwaymanagementhasbeenadoptedbythecivilianlawenforcementfortacticalemergencymedicalsupportandseemsappropriatetomostwildernesssettingsaswell.Thelossofairwaypatencyisnotcompatiblewithlife;thusitisgenerallystatedthattherearenoabsolutecontraindicationstocricothyrotomy.Theonlyabsolutecontraindicationtocricothyrotomyistheabilitytosecureanairwaywithlessinvasivemeans,butthisisnotalwaysanoptioninaustereenvironments.traumathatrenderscricothyrotomyahopelessproce-dure,suchastrachealtransectioninwhichthedistalendretractsintothemediastinumorasigniÞcantcricoidcartilageorlaryngealfracture,canalsobeabsolutecon-Relativecontraindicationstosurgicalcricothyrotomyincludemassiveswellingorobesitywithlossoflandmarks.Ageyoungerthan10to12yearsisacontraindicationbecauseanatomicalconsiderationsmakesurgicalcricothyrotomyextremelydifÞcult,chil-drenarepronetolaryngealtrauma,andtheyhaveahigherincidenceofpostoperativecomplicationsfromsurgicalcricothyrotomythanadults.Therefore,childrenshouldundergoneedlecricothyrotomyifnootherairwaycanbeobtained.CricothyrotomyProceduresandEquipmentTherearenumerousvariationsofcricothyrotomyequip-includingseveralcommerciallyavailablesetsforneedlepercutaneousandopensurgicalprocedures.Manyoftheseproceduresarehospital-basedtech-niquesandarebeyondthescopeofthisreview.Someoftheseprocedureshavemoretools,andthereforeadditionalstepstocompletetheprocedure,andarelesspracticalasdescribedforuseinaustereenviron-Table1providesalistingof12surgicalcrico-thyrotomyprocedures.13,20,32,37Ð45HessertandBennett Elliotetalstudied18anesthesiologiststodeterminewhethertheycouldcorrectlylocatethecricothyroidmembraneon6adulthumanswithina10-secondperiod,simulatinganurgentcricothyrotomy.Theanesthesiolo-gistscorrectlyidentiÞedthecricothyroidmembraneonly30%ofthetime.TheseauthorsandotherssuggestthatultrasoundmayelucidatedifÞcultanatomyandensurecorrectcutaneouspointofentryoverlyingthecricothy-roidmembrane.UltrasoundÕsavailabilityforuseinaustereenvironmentsisincreasinginspeciÞcsettings,eg,disastermedicine,highaltitudeclinics,andmilitaryforwardaidstations,butnormallywouldnotbeavail-able.Itisimportanttonotethattheuseofultrasoundtoidentifyanatomicallandmarksforcricothyrotomyhasnotbeenvalidatedclinicallytoimprovesuccessrateanddecreasecomplications.Owingtosofttissueswellingfromtrauma,traditionalanatomicallandmarkscanbeverychallengingtofeel,whichmaydelayanemergentcricothyrotomy.forusewhenlandmarkscannotbepalpatedbecauseoftraumaorobesityarethatthecricothyroidmembranecanbefound1)approximately1to1.5Þngerbreadthsbelowthelaryngealprominence(thyroidcartilage)intheneckmidline;and2)4Þngerwidths(index,middle,ringÞnger,pinky)abovethesuperiorborderofthesternalThegenerallocationofthecricothyroidmembranecanalsobeapproximatedusingtheangleofthemandibleandhyoidbone.CRICOTHYROIDMEMBRANEThecricothyroidmembraneisadense,trapezoidalÞbro-elasticmembranebetweentheinferiorborderofthethyroidcartilageandthesuperiorborderofthecricothy-roidcartilage.Thecricothyroidmusclesborderthecri-cothyroidmembranelaterally.Theaveragedimensionsare8.2mmwideand10.4mmhigh,withwomenhavingconsistentlysmallercricothyroidmembranedimensionsthanmen.BasedonthissizethecricothyrotomytubeÕsoutermeasurementshouldnotexceed8mm.commercialkitsnowusea6-mmtube,smallenoughforeasyinsertionandreducedriskofcartilagefracture,whilestilllargeenoughforadequateventilation.Averticalmidlineincisionwillavoidallmajorvesselsoftheneck.Boonetalreportednomajorarteries,veins,ornervesinthecricothyroidmembraneregion,yetDo-veretalreportedextensivecollateralanastomosesinthearea.Interestingly,thecricothyroidarterytransversestheupperthirdofthecricothyroidmembranein93%of15cadavers.EventhoughthecricothyroidarteryisnotconsideredclinicallysigniÞcant,atransversestabthroughthelowerportionofthecricothyroidmembraneadjacenttothecricothyroidcartilageisrecommendedtoavoidthissmallartery.Thelocationofthecricothyroidarterymayaccountforthefactthatsomesurgicalcricothyrotomiesarebloodywhereasothersarenot.VOCALCORDSThevocalcordsareattachedtothethyroidcartilageandareatleast1cmsuperiortotheincisionthroughthecricothyroidmembrane.Tubeinsertionshouldbeaimedcaudallytoavoidinjuringthevocalcordsviaretrogradeintubation.Othercomplicationsrelatingtoanatomicalconsiderationsandthetechniquestoavoidthemarediscussedbelow.Incidence,Indications,andContraindicationsCricothyrotomyusagehasdecreasedduringthepast2decadesprimarilyintheED,inlargepartbecauseoflessinvasiveadjunctssuchasthelaryngealmaskairway,Combitube(Kendall-SheridanCatheterCorp,Argyle,NY),andKingLT.ThesesupraglotticdeviceshavereducedthenumberofpatientsintheÒcanÕtintubate,canÕtventilateÓ(CICV)category.Furthermore,theincreaseduseofneuromuscularblockingagentsforrapidsequenceinductionhasincreasedthesuccessofnonop-erativeairwaymanagement.Wallsetalreported8937intubationsacross31EDsbasedonamulticentertraumaregistryfromSeptember1997toJune2002.Ofthese,theneedforsurgicalcricothyrotomyoccurred17times(0.19%).ThislowincidenceofEDcricothyrotomyislessthanotherstudiesreporting1.7%to2.7%ofallattemptedintubations,and2.1%to14.9%ofattemptedintubationsintheprehospitalsetting.Acompromisedairwayisthethirdpotentiallypre-ventablecauseofdeathonthebattleÞeldandresultsin1%to2%ofallcombatfatalitiesinmodernmilitaryMabryandFrankfortstatethatthesurgicalcricothyrotomyprocedureincombatcasualtieshasamuchhigherincidencerateandisnearlydoublethatreportedforcivilians(0.32%vs0.62%oftraumaadmissions,respectively).Furthermore,theseauthorsstatethatairwaydeathsarelowcomparedwithhemor-rhageonthebattleÞeld.However,theimpactofairway-relatedinjuriesfrominadequateoxygenationandventi-lationisnotknown.Todate,therehasbeenonlyonecasereportofasurgicalcricothyrotomyperformedinthewildernessset-ting.WhartonandBennettreportedusingasurgicalEmergentSurgicalCricothyrotomy REVIEWARTICLEOptimizingEmergentSurgicalCricothyrotomyforuseinAustereEnvironmentsM.JosephineHessert,DO,MPH;BradL.Bennett,PhD,MA,EMT-PFromtheDepartmentofEmergencyMedicine,NavalMedicalCenterPortsmouth,Portsmouth,VA(DrHessert);andtheDepartmentofMilitaryandEmergencyMedicine,F.EdwardHébertSchoolofMedicine,UniformedServicesUniversityoftheHealthSciences,Bethesda,MD(DrBennett).