COMPARISON OF THREE DIFFERENT OT TABLE HEIGHT FOR INTUBATION IN TRAINEES— AN ERGONOMICS VIEW

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*DrKinnaGShah,DrVidhiDKantesariya

ABSTRACT

Background:Specificposturesandpractitionerergonomicsarenotuniversallydefinedwithinintubationtraining.Noparticularlandmarkistherethatindicateat whatlevelpatient'sheadshouldbeduringintubation.TheaimwastoevaluatetheeffectofdifferentOTtableheightonintubationtime,successrate,andlaryngeal viewgradingandposturediscomfort.Wedecidedtounderstandphysicalergonomicsofsuccessfullaryngoscopypostureandtoimprovetrainees'learningcurve.

Methods:Seventyfivepatientsdividedintothreegroupsaccordingtopatient'sforeheadatthelevelofintubator'snippleline(groupN),xiphisternum(groupX)and umbilicus(groupU).Anobservationforintubationtime,successrate,discomfortinventilation&intubationandposturewasmade. Fromleftsidedphotographsneck&kneeflexionangle,distancefromintubator'seyetoheelofscope(cm)wasnoted.

Results:Tableheightatnipplelevelmakesintubationlesstimeconsuming(p=0.001)andwithergonomicallyerectpostureandbetterlaryngealview Distancefrom trainee'seyestoheelofscopewasmoreingroupN(pvalue<0.001).Traineestendedtocrouchtowardspatient'smouthwithbendedpostureingroupUandgroupX thangroupN.

Conclusion:HigherOTtableheightcanprovidemuchbetterlaryngealviewinerectposturewithlessdiscomfortandlesstimeconsumingintubation.Traineesmust betaughtandprefertosetOTtableheightatnipplelevelmakingthemerectandcomfortableinposture.

INTRODUCTION:

Acquiringanewskillrequireslearningofcorrectposturee.g.Pianoteachersfirst 1 teachhowtositandskiinginstructorsareequallyfirmonhowweshouldstand? Incricket,eachperfectshotrequireparticularpostureaswellasaction.Surgeon insiststohaveOTtableheightclosertotheirhands,headandnecksurgeonkeeps their eyes on patient positioning before starting procedure. Then how do we standbehindinteachingthecorrectpostureduringlaryngoscopy?Asananaesthetist, we must insist for perfect patient position and OT table height for intubation. Because of the inherently chaotic environment of induction situations, personnel proficiency in performing intubation procedures can range widely There are many studies related to instruments or methods explored to findsuccessinintubationwhereastherearefewstudiesforOTtableheightorpos2 ture in laryngoscopy in relation to success Standard textbooks of anaesthesiology stated that the patient's face should be at a level between the 3 xiphisternumandumbilicusoftheanaesthetistduringlaryngoscopy Andthat theintubator'seyesshouldbeplacedatonefeetabovepatient'sfacetoprovide 4 properanglesanddistancesforlaryngoscopy Wenoticedwidevariationinadoptionofthisguidance.Anaesthetistswithaverageheightdonothavemuchproblembutwithheightmorethan170cm,morecompensationhastobemadewith lowerbodypostureduringintubation.Wedecidedtoevaluatetheeffectofthree different OT table heights on duration and success rate of intubation, posture 3 adoptedandperceptionofdifficultytointubator

Ergonomicsreferstodesigningofequipment,machinesandsystemstoaccommodate behaviours, characteristics and expectations of human beings who use them in everyday working and living environment. Awkward postures during dailyanaesthesiaworksuchasintubation,vascularaccess,neuraxialanaesthesia etc.,theseergonomicrisksareknownfordevelopingspinaldiseasessuchasherniated discs and lumbar muscle contractions. Heath highlighted the benefits of usinganadjustableoperatingtableandtheergonomicallyattractivebenefitsof differentheights-highduringcannulationtopreventbackdiscomfort,abitlower 3 forairwaymanagementandevenlowerforshorttrainees.

Aim of our study is to evaluate the effect of three different OTtable height on durationandsuccessrateofintubation,postureadopted,perceptionofdifficulty tointubator

MATERIALSANDMETHODS:

The study was approved by institutional ethical review committee. 25 trainees (residentshavingexperienceofmorethan7months,14malesand11females)as performer and 75 patients ofAge between 18--60 year andASAgrade I and II postedforelectivesurgeryundergeneralanaesthesiawereincludedinthestudy Thefollowingpatientswereexcludedfromthestudy: ASAIIIandIVpatients, Obese(BMI>30),patientsofobviousdifficultintubationsuchaspatientswith MPGIIIandIV,previousoralornecksurgery,thyromentaldistancelessthan6.5 cm, loose teeth or edentulous jaws and patients at risk of aspiration. Airway assessmentwasdonedaybeforesurgeryforeachpatient.

Patientsweregroupedrandomlyinthreegroups(25patientsineach)onthebasis ofOTtableheightaspt.'sforeheadatlevelofintubator'sbodylandmarksas1) Group N: level of Nipples, 2) Group X: level of Xiphisternum, 3) Group U: levelofUmbilicus.Eachperformerreceivedabriefoverviewofairwayanatomy, standard terms of intubation procedures and each performer do one laryngoscopyineachpatient.

Allpatientswerefastedfor10hrs.Theywereplacedsupinewithoutkeepingpillow Routinemonitoringsuchasnon-invasivebloodpressure,SpO,ECGwere 2 used After Preoxygenation for 5 min, anaesthesia was given as Inj Glycopyrrolate0.02mg,Inj.Fentanyl2ug/kg,Inj.Thiopentone6mg/kgandInj. Succinylcholine2mg/kg.IntubationwasperformedwithMacintoshno.4blade with appropriatesizedETtube.Duringmaskventilation,perceptionofdiscomfort to ventilate was noted. During intubation, trainee inserted the blade into patient's mouth and evaluated the grade of laryngeal view using Cormack LehaneGrade.Aftercompletionofinduction,subjectiveassessmentofdifficulty or discomfort in insertion of blade (1-no discomfort, 2-mild discomfort, 3moderate discomfort, 4-severe discomfort), Cormack Lehane grade, success rate,averagetimeofintubationwerenotedineachgroup.Morethan2intubation trialwasconsideredasfailure.Photographs,atthetimeofintubation,weretaken 2metersawayfromleftsidewith13MPmobilecamera.Fromleftsidedphotographs, degree of arm elevation and neck/lower back/knee flexion during trachealintubationweremeasuredbyusinganglemeasurementmobileapplication named 'Protractor'. Upper body spine movement angle was measured between linesdrawnfromupperbodyspineandT vertebraeatumbilicallevelofopera- 12 tor

Anglebetweenlineofsightandhorizontal(A),anglebetweenhandleofscope and horizontal (B), angle between line of sight and handle of laryngoscope(C) were noted in each group. Distance from eye of performer to heel of laryngoscope(D)wasmeasured.(Figure-1)

Staticallyanalysis:Continuousvariablesareexpressedasmean(standard deviation)whereascategoricalvariablesareexpressedasabsolutevalues.Variables werecomparedusingTtestviawww.graphpad.com.Ap-valueof<0.05wasstatisticallysignificant.

RESULTS:

25traineesand75patientstookpartinthestudy Twoofourtraineehavingheight 185cmand182cmcouldnotbeincludedtodolaryngoscopyingroupN.

Demographicdataoftraineesarebeingcomparableinbothgroups.

TrachealintubationsweresuccessfulinfirstattemptingroupNandXbutsecond attemptwastakenforfivepatients(20%patients)ingroupU.QualityoflaryngealviewasperCormackLehanegradewasbetteringroupNthanatlowerOT tableheights.(Figure1)

KEYWORDS:Intubation,OTtableheight,Ergonomics,Posture. Copyright©2022,IERJ.Thisopen-accessarticleispublishedunderthetermsoftheCreativeCommonsAttribution-NonCommercial4.0InternationalLicensewhichpermitsShare(copyandredistributethematerialinany

1DepartmentofAnaesthesia,GCRIHospital,Ahmedabad,Gujarat,India.(*CorrespondingAuthor)

Figure1:Qualityoflaryngealviewineachgroup

GraphshowingbetterlaryngealviewathigherOTtableheightingroupNandX

Moderatetoseverediscomfortininsertionoflaryngoscopeblade(6patientsout of25patients,25%)andseverediscomfortinmaskventilation(2patientsoutof 25)werehigheringroupN(Table1).FivepatientsingroupNneededtoetipping for insertion of laryngoscope blade into mouth. Narrower upper spine flexion anglewasnotedingroupUandXduetoforwardbodybending.

IntubationtimewassignificantlylessingroupN(8.06±2.1sec)thaningroupX andU(p<0.001)(Table-1).

Duringintubation,discomfortscorewashigherinlowerOT tableheight(32% and16%patientsingroupUandXrespectively)thanathigherposition(Table1).

Duringintubation,lessneckforwardbendingasindicatedbyhigherneckflexion anglewassignificantlyhigheringroupNthaninothergroups(p=0.001)(Table2).

Thedegreeofkneeflexionwashigheratlowerheight(GroupU)thanathigher height(p<0.0001)(Table-1).

Distance from eye of performer to heel of laryngoscope, that was significantly more in group N (27.7±4.84 cm) (p=0.001) (Table-2 indicates that trainees tended to crouch on table with their face closer to patient's mouth during intubationingroupUandgroupX.

DISCUSSION:

Specificposturesandpractitionerergonomicsarenotuniversallydefinedwithin intubation training, and instruction typically follows the model of “see one, do 2 one,teachone”withinavarietyofmedicalfields.Atraineeinanaesthesiamust learn proper body posture and OTtable height setup for decreasing ergonomic risksandimprovingintubationskills.

Moreerectposturewastakenduringintubationatoperatingtableheightatnipple level of intubator with less forward movement of upper spine and less knee flexion. Landmarks mentioned above were used because these are easily matched to operating table heights in routine practice.Why every trainee bend during intubation?? is really a question. It might be due to less confidence in intubation because trained anaesthetists only take crouched posture when they facedifficultintubation.Twoofourmaletrainees(Height185cmand182cm) hadseverediscomfortperformingintubationingroupUevenafterhavingknees flexed.

1 J D Walker observed postures used by expert and trainee anaesthetist during intubationonmannequin.Resultsoftheirstudyshowthatlessexperiencedgroup hadshallowerlineofsight,leveredmoreandstoodwiththeirfaceclosertothe mannequin.ThedifferenceinangleAbetweenthetwostudiesmaybebecauseof ourtraineesleveredlaryngoscopemorethanliftingit.Novicesalwaysfeelpressurisedaboutsuccessofintubationwithoutteethinjury Thesestudieshaveused mannequinassubjectswhereaswehavedonestudyonlivepatients.As,mannequins are not same as real subjects, less compliant and are difficult to intubate becauseofstiffness.

2 AdamdeLavega etalstudiedergonomicsofnovicesandexpertsduringsimulated tracheal intubation at maximum and minimum height of adjustable bed. Observationwasmadethatexpertanaesthetistexhibitedlessulnardeviationand forearm supination during task requiring less wrist manipulation. Identifying best practices in intubation biomechanics could shorten the learning curve, improveETIsuccessratesandreduceventilationtimeinbothemergentandcontrolled intubation situations. We also emphasize on learning improved techniquesformaskventilationandtrachealintubationbyteachingtraineestosetOT tableheightathigherlevel.

3 AJayakumar etalobservedminimaleffectonthespeed(p=0.046)butnotsuccessrate(p=0.14)andsignificanteffectofhighertrolleyheightonperceptionof difficultywhenperformingintubationonmanikins.Anaesthetiststendtoadopt

poor posture when trolley height is lower Intubation duration is significantly higher in lower than higher OTtable height (P0.001). Our study also signifies earlyintubation,highersuccessrate,betterpostureandlessperceptionofdifficultyinintubationathighertrolleyheightthanlowerheight.Poorpostureinthe formofkneeandlowerbackflexionnotedingroupUandXespeciallybytaller anaesthetists.

4 H.C.Lee observedthatthelaryngealviewbeforeposturalchangeswasbetterat nipplelevelthaninumbilicuslevel(P=0.003).TheobjectiveandsubjectivemeasurementsofneckorlowerbackflexionduringintubationwerehigherinGroup U than in Groups X and N (P=0.01 for each). Higher operating tables (at the xiphoidprocessandnippleleveloftheanaesthetist)canprovidebetterlaryngeal views with less discomfort during tracheal intubation. Our study also shows higher degree of neck and lower back flexion angle in group U and improved laryngealviewathigherheight(GroupN).Moreflexionatkneelevelaswellas upperspinemovementangleswerenarroweringroupUandX.Fromergonomic pointofview,bodyposturewasverybad.Thistypeofbodyposturewasactually adjustedforlaryngealviewtocompensateforlowerheightofOTtable.

Accordingtotheprincipleofergonomics(thescienceofhumanfactors),workplacedesignshouldbebasedonminimizingdiscomfortandmaximizingperformancebecausehumanreservescancompensateforpoorlayoutwithoutdecrease ofperformance.So,itisimportanttoplacetheoperatingtablehighertominimize discomfortandmaximizeperformanceduringtrachealintubation.

5 A. J. Matthews et al observed the less experienced group compensate with upperbodybystoopingandbringingtheirfaceclosertopatientsreducingbinocularvision.Inourstudydata,angleAandangleDwhichindicatesneckflexion and upper back flexion is more in group U than in group N. Lower OT table height make novices to lean forward with upper body parts as well as knee flexioninourstudy Ourstudyobservedminimalbentormoreerectergonomic postureatOTtableheightattrainee'snipplelevel.LowerOTtableheightcauses armelevationwhichcausedifficultytoliftanteriorwalloftrachea.

Laryngoscopybymacintoshbladerequiresabductionandrotationofupperarm. Combination of crouched flexed posture by trainee makes laryngoscopy more difficultandmakesthemclosertopatient'smouth.

Twotalltrainees(>182cm)couldn'tintubateingroupUandtheywerenotcomfortableingroupU.Shorttrainees(<137cm)weremostcomfortableingroupN thaningroupU.Overall,wenoticedtheintubationsuccessratedependsonOT tableheight.So,OTtableheightatintubator'snipplelevelprovidedmoreerect andergonomicbodypostureandlesserthemusculoskeletalinjuryonlongterm andlessstressforintubationsuccessduringinductionphase.

Wenowteachtraineesexplicitlytotrytostandstraightandmakedistancefrom patient's mouth while attempting intubation. It is needed only to look in the mouthandnotgetintoit.

CONCLUSION:

HigherOTtableheightcanprovidemuchbetterlaryngealviewwithlessdiscomfortandlesstimeconsumingintubation.Traineesmustbetaughtandprefertoset OT table height at higher level from day one. Intubation must be done with straightbackandcompensationforheightshouldbemadebykneejointflexion ratherthanstooping.

REFERENCES:

I. J. D. Walker Posture used by anaesthetist during laryngoscopy British Journal of Anaesthesia.2002:89;(5):772±4.

II. Adam de Laveaga, Michael C. Wadman, Laura Wirth and M. Susan Hallbeck Ergonomics of novices and experts during simulated endotracheal intubation. Innovative DesignandErgonomicAnalysisLaboratory,IndustrialandManagementSystemsEngineering,UniversityofNebraska,Lincoln,NE,USA;2UniversityofNebraskaMedical Center,Omaha,NE,USA

III. A. Jayakumar, B.Ateleanu,A.R. Wilkes, I. Hodzovic Effect of trolley height on the managementofdifficultairway:amanikinstudy,JRomAnestTerapInt2013Vol20, Nr.294-98.

IV H.-C.Lee,M.-J.Yun,J.-W Hwang,H.-S.Na,D.-H.KimandJ.-Y Park.HigheroperatingtableprovidebetterlaryngealviewsfortrachealintubationBJA18,2013page1-7.

V A.J.Mathews,C.J.H.JohnsonandN.W GoodmanBodypostureduringsimulatedtrachealintubation,Anaesthesia,199853,pages331-334.

Table1:Laryngealview,maskventilationdiscomfort,discomfortininsertionofblade,intubationdurationandnumberofattempts. Groups GroupN GroupX GroupU Laryngealview–CormackLehane(i/ii/iii/iv) 22/2/1/0 22/1/1/1 18/3/2/2

Maskventilationdiscomfort(1/2/3/4) 20/2/1/2 13/12/0/0 22/1/2/0 Discomfortininsertionofblade(1/2/3/4) 5/8/6/6 24/1/0/0 25/1/0/0

Intubationdiscomfort(1/2/3/4) 24/1/0/0 19/2/2/2 14/3/3/5

Intubationduration(sec) 8.06±2.1* 9.7±2.02# 12.03±3.92$

Numberofattempts(1/2) 25/0 25/0 20/5

Categoricalvariablesarepresentedasthenumberofsubjectswhereascontinuousvariablesarepresentedasmean(SD)*P<0.05vsgroupU,#P<0.05vsgroupU,$P <0.05vsgroupN(Discomfortgrades1:Nodiscomfort,2:milddiscomfort,3:moderatediscomfort,4:severediscomfort)

Table2:DifferentpostureanglesduringIntubation Parameter GroupN GroupX GroupU p-value

A 27.4±4.6 26.9±7.2 32.4±6.9 0.004*

B 99.62±3.27 110.6±10.9 105.24±11.09 0.02* C 30.85±1.76 33.7±5.79 31.3±3.64 0.5

D 27.7±4.84 12.2±3.40 14.5±5.45 0.001*

Neckflexionangle 56.7±12.9 25.4±15.7 28.0±10.5 0.0001*

Upperspinemovementangle 94.4±5.3 75.9±10.2 70.4±12.4 0.0001*

Armelevationangle 36.4±3.9 35.4±3.6 32.3±5.9 0.005*

Kneeflexionangle 15.6±2.5 45.5±11.4 70.3±10.4 0.0001*

(A:Anglebetweenlineofsightandhorizontal,B: anglebetweenhandleofscopeandhorizontal,C:anglebetweenlineofsightandhandleoflaryngoscope,D:distance fromeyeofperformertoheeloflaryngoscopeasshowninFigure-1)*pvalue(betweengroupNandU)<0.05statisticallysignificant