Rev. Bras. Anestesiol. vol.66 número3

REVISTA

BRASILEIRA

DE

ANESTESIOLOGIA

SCIENTIFIC

ARTICLE

Analysis

of

cricoid

pressure

application:

anaesthetic

trainee

doctors

vs.

nursing

anaesthetic

assistants

Nurul

Haizam

Yahaya

_,

_Rufinah

_Teo

_,

_Azarinah

_Izaham

_,

_Shereen

_Tang

_,

Aliza

Mohamad

Yusof

_,

_Norsidah

_Abdul

_Manap

a_{DepartmentofAnaesthesiologyandIntensiveCare,TelukIntanHospital,Perak,Malaysia}

b_{DepartmentofAnaesthesiologyandIntensiveCare,UniversitiKebangsaanMalaysiaMedicalCentre,KualaLumpur,Malaysia}

Received30September2014;accepted28October2014

Availableonline12May2015

KEYWORDS

Cricoidpressure; Trainee

anaesthetists; Anaestheticassistants

Abstract

Backgroundandobjective: Toevaluate the ability ofanaesthetic trainee doctors compared tonursinganaestheticassistantsinidentifyingthecricoidcartilage,applyingtheappropriate cricoidpressureandproducinganadequatelaryngealinletview.

Methods:Eighty-fiveparticipants,42anaesthetictraineedoctorsand43nursinganaesthetic assistants,wereaskedtocompleteasetofquestionnaireswhichincludedthecorrectamountof forcetobeappliedtothecricoidcartilage.Theywerethenaskedtoidentifythecricoid carti-lageandapplythecricoidpressureonanupperairwaymanikinplacedonaweighingscale,and thepressurewasrecorded.Subsequentlytheyappliedcricoidpressureonactualanaesthetized patientsfollowingrapidsequenceinduction.Detailsregardingthecricoidpressureapplication andtheCormack---Lehaneclassificationofthelaryngealviewwererecorded.

Results:Theanaesthetictraineedoctorsweresignificantlybetterthanthenursinganaesthetic assistantsinidentifyingthecricoidcartilage(95.2%vs.55.8%,p=0.001).However,bothgroups wereequallypoorintheknowledgeabouttheamountofcricoidpressureforcerequired(11.9% vs.9.3%respectively)andinthecorrectapplicationofcricoidpressure(16.7%vs.20.9% respec-tively).Thethree-fingertechniquewasperformedby85.7%oftheanaesthetictraineedoctors and65.1%ofthenursinganaestheticassistants(p=0.03).Therewerenosignificantdifferences intheCormack---Lehaneviewbetweenbothgroups.

Conclusion: Theanaesthetictraineedoctorswerebetterthanthenursinganaestheticassistants incricoidcartilageidentificationbutbothgroupswere equallypoorintheir knowledgeand applicationofcricoidpressure.

© 2015SociedadeBrasileirade Anestesiologia.Publishedby ElsevierEditoraLtda.Allrights reserved.

∗_{Correspondingauthor.}

E-mails:nmanap@ppukm.ukm.edu.my,nmanap@ymail.com(N.AbdulManap).

http://dx.doi.org/10.1016/j.bjane.2014.10.008

284 N.H.Yahayaetal.

PALAVRAS-CHAVE

Pressãocricoide; Residentesem anestesiologia; Assistentesde anestesia

Análisedaaplicac¸ãodepressãocricoide:residentesemanestesiologiavs.

enfermeirosassistentesdeanestesia

Resumo

Justificativaeobjetivo:Avaliaracapacidadederesidentesemanestesiologiaemcomparac¸ão comenfermeirosassistentesdeenfermagemparaidentificaracartilagemcricoide,aplicara pressãocricoideadequadaeproduzirumavistaadequadadaentradadalaringe.

Métodos: Oitentaecincoparticipantes,42residentesemanestesiologiae43enfermeiros assis-tentesdeenfermagemforamconvidadosaresponderalgunsquestionáriossobreaquantidade corretadeforc¸aaseraplicadanacartilagemcricoide.Osparticipantesdeviamidentificara cartilagemcricoideeaplicarapressãocricoideemmodelosdeviasaéreassuperiores coloca-dossobreumabalanc¸adepesagem,eapressãoeraregistada.Posteriormente,osparticipantes aplicarampressãocricoideempacientesanestesiadosreaisapósainduc¸ãodesequência ráp-ida.Osdetalhesasobreaaplicac¸ãodepressãocricoideeaclassificac¸ãodeCormack-Lehane davisibilidadedalaringeforamregistrados.

Resultados: Osresidentesemanestesiologiaforamsignificativamentemelhoresqueos enfer-meirosassistentesdeenfermagem naidentificac¸ãodacartilagemcricoide(95,2%vs.55,8%, p=0,001).Noentanto,oconhecimentodeambososgruposeraprecáriosobreaquantidadede forc¸anecessáriaparaaplicarapressãocricoide(11,9%vs.9,3%,respectivamente)eacorreta aplicac¸ãodapressãocricoide(16,7%vs.20,9%,respectivamente).Atécnicadetrêsdedosfoi realizadapor85,7%dosresidentesemanestesiologiae65,1%dosenfermeiros assistentesde enfermagem(p=0,03).Nãohouvediferenc¸asignificativaentreosdoisgruposemrelac¸ãoà classificac¸ãodeCormack-Lehaneparaavisão.

Conclusão:Osresidentesemanestesiologiaforammelhoresqueosenfermeirosassistentesde enfermagem para identificar acartilagem cricoide,mas ambos os gruposapresentaram um conhecimentoigualmenteprecáriosobreaaplicac¸ãodepressãocricoide.

©2015SociedadeBrasileiradeAnestesiologia.PublicadoporElsevierEditoraLtda.Todosos direitosreservados.

Introduction

Cricoidpressureisanexternalmechanicalpressureapplied ontothe patient’s cricoidcartilage duringrapid sequence induction. Also known as Sellick’s manoeuvre, it was introducedin 1961 tocontrolregurgitationandaspiration ofgastriccontentduringinductionofanaesthesia.1_Theuse

ofcricoidpressurefor preventionof pulmonaryaspiration

inhighrisksurgicalpatientsisconsideredstandardpractice

amongstthemajorityofanaesthesiaproviders.2

The routine application of cricoid pressure has been

challengedwith theproblems of impaired laryngeal view,

less effective mask ventilation and unproven benefit in

reducingtheincidenceofaspirationorregurgitation.3_The

effectiveness of cricoid pressure is becoming an issue

asmany operators lack the appropriate knowledge about

it. It has been suggested that a proper training

pro-grammeiswarranted toimprovethe cognitiveknowledge

and practical clinical skill of cricoid pressure

applica-tion.Participants whowereunabletoidentifythecorrect

anatomical location of cricoid cartilage were also less

likelytodemonstrate cognitiveknowledge concerningthe

correct amount of cricoid pressure to be applied.2 _In

an observational study on African women, Fenton and

Reynold found that cricoid pressure did not provide any

protection against regurgitationor deathin patients who

underwentcaesareansection.4_{Applicationofcricoid}

pres-sure resulted in significant reduction in the mean tidal

volumeandupperairwayobstructionin9---18%ofnon-obese

individuals.5

Inouroperatingtheatres,thenursinganaesthetic

assis-tantswhoroutinely assistintheapplication ofthecricoid

pressurearenotallformallytrained,butreceivedin-house

training. This study was done to determine if they were

comparable with the anaesthetic trainee doctorsin their

abilitytoapplythecricoidpressure.

Methods

Thiswasaprospectiverandomizedsingle-blindclinicalstudy

that evaluated the ability of anaesthetic trainee doctors

and nursing anaesthetic assistants in applying the cricoid

pressure. Prior approval wasobtained from the Research

andEthicsCommittee ofourinstitution. Patients’written

informedconsentwasalsoobtainedbeforetheir

participa-tion.

Thisstudyconsistedoftwoparts.Inthefirstpart,

partic-ipantswereaskedtofillinaquestionnairewhichincluded

age, gender, hand dominance, years of anaesthetic

work-ingexperienceandprevious formaltrainingrelatedtothe

applicationofcricoidpressure.Then,theirknowledgeand

demonstration of the cricoid pressure on an upper

air-waymanikinweredocumented.Theairwaymanikinwitha

clearlydefinedoropharynx,thyroidcartilage,cricoid

Figure1 Modelofupperairwayonweighingscale.

asshowninFig.1.Theweighingscalewascalibratedwith

the modelin placebefore each reading.The participants

wereaskedtoapplythecricoidpressureontothemanikin

as in clinical settings and informed the investigator once

thecorrectpressurehadbeenapplied.Theanatomicalsite

chosen by theparticipant,the technique performed (e.g.

three-finger or two-finger)and the pressureapplied were

thenrecorded.Thenumericaldisplayofthescalewasonly

visibletotheinvestigator.

Inthesecondpartofthestudy,theparticipantsapplied

cricoidpressure onactual anaesthetizedpatients. A total

ofeighty-fiveAmericanSocietyofAnaesthesiologists(ASA)

physicalstatusI---IIIpatients,aged18---70years,who

under-went general anaesthesia with rapid sequence induction

andendotracheal intubationwere enrolled.Patientswere

excluded if there was anticipated difficult intubation,

presence of neck abnormalities or goitre that prevented

effectivecricoidpressureapplication.

Patientswererandomlyassignedtotwogroupsusing

ran-dom sequence computergenerated numbers. In Group A,

cricoidpressurewasperformedbyanaesthetictrainee

doc-torswithatleast3yearsofanaestheticexperience.InGroup

B,cricoid pressure wasperformed by nursing anaesthetic

assistants who were registered staff nurses and routinely

assisted in the application of the cricoid pressure in our

operatingtheatres.Theywerenotallformallytrained,but

receivedonthejobtraining.

Allpatientswerefastedforatleast6handwerenot

pre-medicatedwithsedatives.Standardanaestheticmonitoring

ofelectrocardiography, non-invasiveblood pressure,pulse

oximetryandcapnographywereappliedonallpatients.The

patient’sheadwasplacedonaheadring,withaneck

flex-ionandheadextensionforintubation.Pre-oxygenationfor

3minwasfollowedbyinductionofanaesthesiawith

intra-venousfentanyl2␮g/kgandintravenouspropofol2mg/kg.

Endotracheal intubation was facilitated with intravenous

suxamethonium2mg/kg. Once thepatientstarted tolose

consciousness,theparticipantsappliedcricoidpressureas

theynormallydid(Figs.2and3).

Figure2 Three-fingertechniqueofcricoidpressure.

Theinvestigatorrecordeddetailsonthecricoidpressure

application,thelaryngealviewbasedonCormack---Lehane

classification, cricoid pressure adjustment requirement,

manipulationsusedandcomplicationssuchasregurgitation

oraspiration.Endotrachealintubationwascarriedoutbythe

anaesthetist 30s after administration of suxamethonium.

Surgerywasallowedtoproceedafterconfirmationofcorrect

placementoftheendotrachealtube.

Data calculated in our pilot study of 15 participants

showedthatasamplesizeof26wasabletodetecta57.8%

differencebetween the twogroups. Using the Powerand

Sample Size Calculation Version 3.0.14, the sample size

requiredwas13patientsperarmbasedonanalphavalueof

0.05andapowerof80%.Thus,atotalofatleast29nursing

anaestheticassistantsandanaesthetictraineedoctorswere

requiredwhenconsideringadrop-outrateof10%.

286 N.H.Yahayaetal.

Table1 Demographicdataofparticipants.Valuesareexpressedasmean±SDandnumber,n(%)asappropriate.

Nursinganaesthetic assistants

(n=43)

Anaesthetic traineedoctors (n=42)

p

Age(years) 28.7±0.3 33.0±2.6

Handdominance

Right 40(93.0) 35(83.3)

Left 3(7.0) 7(16.7)

Gender <0.001a

Male 0 14(33.3)

Female 43(100) 28(66.7)

Durationorexperienceinapplyingcricoidpressure

<1year 7(16.3) 1(2.4)

>1year 36(83.7) 41(97.6)

Formaltrainingoncricoidpressureapplication 13(30.2) 33(78.6) <0.001a

a_{p<0.05statisticallysignificant.}

Statisticalanalysis

Data were analysed with SPSS 17.0 software (SPSSTM_,

Chicago,IL).Chi-squaretestwasusedtocomparethe

cog-nitiveknowledgeandactualapplicationofcricoidpressure

andunpaired Student’s t-test for analysisof participants’ age.A p-value of <0.05wasconsidered tobestatistically significant.

Results

Atotalof85participantswererecruitedintothisstudywith 43nursinganaestheticassistantsand42anaesthetictrainee

doctors. There were no drop-outs. As shown in Table 1,

thetwogroups werecomparablewithrespecttotheage,

hand dominance and experience in applying cricoid

pres-sure.However,thenursing anaestheticassistantswereall

females andtheir lack of formal previous training wasof

statisticalsignificance.

Thecorrectcricoidpressurewastakentobeeither30or

40N.Only9.3%ofnursinganaestheticassistantsand11.9%

of anaesthetic trainee doctors gave the correct answer

as shown in Table 2. Both groups were also comparable

in applying the correct pressurewith only 20.9% of

nurs-inganaestheticassistantsand16.7%ofanaesthetictrainee

doctorsdoingitcorrectly.Theanaesthetictraineedoctors

weresignificantlybetterinidentifyingthecricoidcartilage

(p=0.001)with95.2%identifyingitcorrectly comparedto

55.8%nursinganaestheticassistants.Amajorityofthe

par-ticipants performed the three-finger technique of cricoid

pressureapplication,85.7%oftheanaesthetictrainee

doc-tors compared to 65.1% of nursing anaesthetic assistants

(p=0.03).

Table 3 shows there was no significant difference in

theCormack-Lehaneviewsduringtheinitialapplicationof

cricoidpressureinboth groups.Mostofthepatientswere

intubatedwithasingle attempt,97.7% and92.9%

respec-tively.Therewasnoaspirationorregurgitationseeninboth groups.

Discussion

The correctapplicationofcricoidpressureisimportantto

beeffectiveinpreventingpulmonaryaspirationandavoiding

complicationssuchasoesophagealinjuryordifficult intuba-tionduetoimpairmentofthelaryngealview.Technically,it

Table2 Analysisofcricoidpressureonairwaymanikin.Valuesexpressedasnumber,n(%)asappropriate.

Nursinganaesthetic assistants

(n=43)

Anaesthetictrainee doctors

(n=42)

p

Correctlystatedcricoidpressure 4(9.3) 5(11.9) 0.70 Correctapplicationofcricoidpressure 9(20.9) 7(16.7) 0.62 Correctidentificationofcricoidcartilage 24(55.8) 40(95.2) 0.001a

Handthatappliescricoidpressure 0.72

Right 39(90.7) 39(92.9)

Left 4(9.3) 3(7.1)

Technique 0.03a

Three-finger 28(65.1) 36(85.7)

Two-Finger 15(34.9) 6(14.3)

Table3 Theimpactofcricoidpressureonlaryngealview.Valuesareexpressedasnumber,n(%)asappropriate.

Nursinganaesthetic assistants

(n=43)

Anaesthetic traineedoctors (n=42)

p

Cormack-Lehanescoreatfirstattempt 0.27

I 27(62.8) 31(73.8)

II 14(32.6) 11(26.2)

III 2(4.7) 0

Numberofattemptsatintubation 0.29

1 42(97.7) 39(92.9)

2 1(2.3) 3(7.1)

issimplytheapplicationofbackwardpressureonthecricoid cartilage,justinferiortothethyroidcartilage,toocclude theoesophagus.6_{Thismanoeuvrepromotessafeanaesthesia}

butrequires trainedor experiencedpersonneland

consid-erationsofthe anatomicalfeatures,physiological effects,

techniqueandpressurerequirementsanditseffectonthe

easeofintubation.

Our study revealed there was significant knowledge

deficit in the identification of the cricoidcartilage which

is essential for correct cricoid pressure application. The

majority of our anaesthetic trainee doctors (95.2%) were

abletoidentify,but only55.8%ofthenursing anaesthetic

assistantswereabletodoso.Lowidentificationresultsby

nursing anaestheticassistantswerealso reportedinother

studies at 55.6% and 24.0%.2,7 _{The application of cricoid}

pressure onto the wronganatomical structure can

poten-tiallyleadtocomplicationssuchastrauma,distortionofthe airwayordifficultywithbagmaskventilation.4_Poorcricoid cartilageidentificationbyournursinganaestheticassistants

canbeattributedtothelowpercentageofformaltraining

receivedon cricoidpressureapplication (30.2%). As such,

formal coaching of the nurses to include the anatomical

relationships pertainingtothe cricoidcartilage should be

emphasized.

Our nursing anaesthetic assistants and anaesthetic

traineedoctorsshowedcomparablylowvaluesforcorrectly

stating (9.3% vs. 11.9% respectively) and applying (20.9%

vs.16.7%respectively)therequiredpressure.Thegenerally

substandardlevelofknowledgewithregardtocricoid

pres-surearesimilarlyreportedinseveralotherstudieswhereby

only 5.0---17.8% of the subjects (perioperative nurses or

anaesthetictrainees)wereabletocorrectlystatethe

cor-rect amount of cricoid pressure.2,8---10 _{These studies show}

thatthereis stillinadequatebasicknowledgeandskillsin cricoidpressureapplicationbyboththeanaesthetictrainees andassistants.

Although most of ouranaesthetic trainee doctorshave

attendedpreviouscoursesrelatedtocricoidpressure

appli-cation,theywerenotbetterthanthenursingassistantsat

performingit.Factorsthathavebeen proposedbyseveral

authorsforthepoorperformanceincluded lackof

formal-ized or standardized training,infrequencyof training and

lackofclinicalguidelines.11---13_{Inourinstitution,the}

anaes-thetic trainee doctors are responsible for managing the

airway including the intubation process. Therefore, they

rarelyhavetheopportunitytopracticeapplyingthecricoid

pressureadequately. This could be oneof the reasons as

totheirpoorperformanceinapplyingthecricoidpressure

despitehavingsoundknowledgetocorrectlyrecognizeand

identifythecricoidcartilageaswassimilarlydescribedby BrissonandBrissonin2010.14

In2006,PattenutilizedtheKnowlestheoryinaneffortto educatenursesaboutcorrectapplicationofcricoidpressure

andsucceededinincreasingtheknowledgeandskillfroma

pre-testresultof3.5%toapost-testresultof68.6%.15_Kopka

and Crawford proposed an effective biofeedback trainer

basedon key features of regular, simple and inexpensive

training which was able to effectively train anaesthetic

personnelinthe correctapplication of cricoidpressure.16 Thus,apartfromregulartraining,thequalityofthetraining

remains an important aspect of successfuleducation

pro-grammes.

The majority of the participantsin our studyare right

handdominant.Asthepredominantpositionforthe

assis-tantapplyingthecricoidpressureistostandonthepatient’s

right side, hand dominance is logically deemed to be an

important factor for the application of cricoid pressure.

Cooket al. demonstratedthat whencricoid pressure was

applied withthe left hand, the average mean force was

lessby5---12N.17 _{Onthecontrary,SchmidtandAkeson} con-cludedthattherewasnosignificantdifferenceintheability toapplyandmaintainforcewitheitherhand.18_Cooketal.

alsoshowed that nursing anaesthetic assistantsapplied a

muchlowerforce thanis classicallytaughtandwereable

to maintain the force with either hand for a sustained

period.17 _{Thus, left hand application is acceptable when}

clinically indicated, but it may have a lower margin for

errorthanwhenappliedwiththerighthand.17_Beaversetal.

demonstratednocorrelationinhanddominanceandactual

applicationofcricoidpressureamongstperioperativenurses

andsuggested thatthebesthandchoice foreffectiveand

sustainablecricoidpressureapplicationwouldbethehand

withthegreaterstrengthanddexterity.2

When patients become unconscious, pressure on the

cricoidcartilageshouldbeincreasedto3---4kgor30---40N.

Theaspirationofgastriccontentscanbeavoidedbygiving

atotal of4kgor 40Npressure.7---10 _{Studies have reported} thatonly10---31%ofparticipantsappliedthecorrectamount ofcricoidpressure.7,9,10_{Thisisdisconcertingbecause}

inad-equate pressure application may result in an unoccluded

oesophagusrenderingpatientsatriskforregurgitationand

288 N.H.Yahayaetal.

result in airway management difficulties and inadvertent

patientinjuries.

Mostofourparticipantsusedthethree-fingertechnique

duringcricoidpressureapplication.Wraightetal.suggested thatthe three-fingertechnique is lesslikelyto cause lat-eraldisplacementwhichcouldhindertheglottisviewduring

laryngoscopy.19 _{Other common methods using thumb and}

index finger or thumb, index finger and middle finger or

extendedthenarweb have beendescribed.1,19 _{As a result}

of the variety of methods postulated in cricoid pressure

application,sometechniquescontributedto25%ineffective

performance according to Brisson and Brisson.14 _The

cur-rentlyavailable resourcesareconflictingandthereareno

airwaytrainingfocusingoncricoidpressureapplication.14 Thisstudywaslimitedbythelackofreal-timemonitoring duringapplicationofcricoidpressureonactualpatients.The

amountofpressureappliedontheairwaymanikinandonthe

realpatientsmaydifferasthesensationfeltisnotthesame,

withthepatients’tissueconsistencybeingsofterthanthe

stiffrubberymaterialoftheairwaymanikin.

Our institution’s nursing anaesthetic assistants are

skewedtowardsthefemalegender.This couldbeanother

limitationtothestudy.InSweden,asimilarstudyrevealed

that the inadequate comprehension on the practice of

cricoidpressureapplicationremainedprevalentdespitenot

reportinganygenderdifference.18

Inconclusion,theanaesthetictraineedoctorsweremore

proficientintheidentificationofcricoidcartilagebutboth

theanaesthetictraineedoctorsandthenursinganaesthetic

assistants were equally poor in their application of the

cricoid pressure. Strategies to ensure safe and effective

cricoidpressureapplication shouldbeimprovedtoensure

goodpatientoutcome.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

Acknowledgements

TheauthorsthankMuhamadRahimiCheHassan,Scientific

Research Officer, Universiti Kebangsaan Malaysia Medical

Centreforhisinvaluableassistanceinthestatistical analy-sis.

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