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Year: 2010

Evaluation of high-definition and conventional oscillometricblood pressure measurement in anaesthetised dogs using ACVIM

guidelines

Wernick, M; Doherr, M; Howard, J; Francey, T

Wernick, M; Doherr, M; Howard, J; Francey, T (2010). Evaluation of high-definition and conventionaloscillometric blood pressure measurement in anaesthetised dogs using ACVIM guidelines. Journal of Small AnimalPractice, 51(6):318-324.Postprint available at:http://www.zora.uzh.ch

Posted at the Zurich Open Repository and Archive, University of Zurich.http://www.zora.uzh.ch

Originally published at:Journal of Small Animal Practice 2010, 51(6):318-324.

Wernick, M; Doherr, M; Howard, J; Francey, T (2010). Evaluation of high-definition and conventionaloscillometric blood pressure measurement in anaesthetised dogs using ACVIM guidelines. Journal of Small AnimalPractice, 51(6):318-324.Postprint available at:http://www.zora.uzh.ch

Posted at the Zurich Open Repository and Archive, University of Zurich.http://www.zora.uzh.ch

Originally published at:Journal of Small Animal Practice 2010, 51(6):318-324.

1

Evaluationofhigh‐definitionandconventionaloscillometricbloodpressuremeasurement1

inanaesthetiseddogsusingACVIMguidelines2

M.Wernick1,2,M.Doherr3,J.Howard4,5,T.Francey1,53

4 1SmallAnimalClinic,DepartmentofSmallAnimalinternalMedicine,VetsuisseFaculty,5

UniversityofBern,Switzerland6

7 2Currentaddress:ClinicforZooAnimals,ExoticPetsandWildlife,VetsuisseFaculty,8

UniversityofZurich,Switzerland9

10 3DepartmentofClinicalResearch&VeterinaryPublicHealth,VetsuisseFaculty,Universityof11

Bern,Switzerland12

13 4ClinicalLaboratory,DepartmentofVeterinaryMedicine,VetsuisseFaculty,Universityof14

Bern,Switzerland15

16 5Theseauthorscontributedequally17

18

Correspondenceto:MorenaWernick,ClinicforZooAnimals,ExoticPetsandWildlife,19

Winterthurerstr.260,8057Zurich,Switzerland,mwernick@vetclinics.uzh.ch20

21

Runninghead:Evaluationofstandardandhigh‐definitionoscillometricdevices22

23

2

Summary23

24

Objectives:25

Toevaluatehigh‐definitionandconventionaloscillometryincomparisonwithdirectblood26

pressuremeasurementsinanaesthetiseddogs.27

Methods:28

Eightsimultaneousreadingsforsystolic,diastolicandmeanpressurewereobtaineddirectly29

andwitheachoftwodevicesin9anaesthetiseddogs.Measurementprocedureand30

validationwerebasedonthe2007ACVIMguidelines.31

Results:32

Sixty‐threesimultaneousreadingswereevaluatedforeachdeviceanddirectmeasurements.33

Themeandifferences(bias)todirectvalueswerewithin10mmHgforbothdevicesalthough34

biasforSAPandDAPwashigherforMemodiagnostic.Thestandarddeviationsofdifferences35

(precision)werewithin15mmHgforDinamapbutexceededforMemodiagnostic.36

CorrelationcoefficientswerehigherforDinamapthanMemodiagnosticbutbothfailedto37

reachacorrelationof0.9.Over50%ofvalueslaywithin10mmHgofdirectmeasuresfor38

bothdevicesbutthispercentagewasgreaterforDinamapthanMemodiagnostic.Over80%39

ofvalueslaywithin20mmHgofdirectmeasuresforDinamapbutnotforMemodiagnostic.40

Clinicalsignificance:41

BothdevicesfailedtomeetACVIMguidelinevalidation.However,Dinamaponlyfailedwith42

regardstocorrelation.Memodiagnosticfailedonseveralrequirementsand,basedonpoor43

correlation,accuracyandprecision,thisdevicecannotbecurrentlyrecommendedfordogs44

underanaesthesia.45

46

Keywords:47

Dog,bloodpressure,directarterialpressure,oscillometry,high‐definitionoscillometry,48

validation49

3

Introduction50

Theimportanceofdetectingalterationsinsystemicbloodpressure(BP)isincreasingly51

recognisedinveterinarymedicine.Asearlydetectionandtreatmentofhypertensionmay52

avertseriousandpotentiallyfatalsequela,measurementofBPindogsandcatsaffectedbya53

varietyofdisordersisfrequentlyperformedinclinicalpractice(Brownandothers2007,54

Habermanandothers2006).Inaddition,continuousBPmonitoringofdogsandcatsunder55

generalanaesthesiahaslongsincebecomeroutine,inparticularbecauseoftheimportance56

ofrecognisinghypotension(Sawyerandothers2004).Directintra‐arterialBPmeasurement57

istheacceptedgoldstandardbutisnotcommonlyusedinclinicalpracticebecauseitis58

technicallydemandingandinvasive.Instead,avarietyofnoninvasivedevicesarein59

widespreaduse(Brownandothers2007,DeflandreandHellebrekers2008,Grandyand60

others1992,Habermannandothers2006,Mandigers2005,Sawyerandothers2004,61

Stepienandothers2003).62

Cliniciansexpectthatcomparativestudiesshowingthatmeasurementsare63

meaningfulareperformedwhennewnoninvasiveBPdevicesareintroduced.Priorto64

evaluatingdevicesinconsciousclinicalpatients,initialstudiesareoftenperformed65

comparingresultswithdirectBPmeasurementsinanimalsunderanaesthesia(Bodeyand66

others1994,Gainsandothers1995,Geddesandothers1980,Meursandothers1996,67

Sawyerandothers1991,Sawyerandothers2004)butnospecificrequirementsfor68

validationofveterinaryBPdevicesexist.Asaresult,themannerinwhichdevicesare69

assessedvariesgreatlyfromstudytostudy,makingdifficultdirectcomparisonsbetween70

assessmentsofdifferentdevicesindifferentreports.71

InanattempttoofferveterinarypractitionersguidelinestostandardiseBP72

assessment,theACVIMissuedaconsensusstatementfortheidentification,evaluation,and73

4

managementofsystemichypertensionindogsandcatsin2007(Brownetal.2007).These74

guidelinesincluderecommendationsfordevicecalibration,patientrestraint,cuffsizeand75

position,andpatientpositioningforbloodpressuremeasurement.Instructionsforthe76

validationofBPdevicesinanaesthetisedandconsciousanimals,basedonguidelinesofthe77

AssociationfortheAdvancementofMedicalInstrumentation(AAMI),arelistedinthe78

ConsensusStatementappendixandincludespecificconditionsunderwhichsystemic79

efficacyofadevicearesatisfied.80

OscillometricBPdeviceshavebeeninwide‐spreadclinicaluseformanyyearsinsmall81

animals.Recently,anewhigh‐definitionoscillometricdevice,theMemodiagnostic(S+B82

MedVETGmbH,Germany)wasintroducedandismarketedinEuropeandtheUSA.This83

deviceholdspromisefordeliveringaccurateandreliablemeasuresofbloodpressureindogs84

andcats,however,noreportsonthevalidityofBPreadingswiththisdevicehavebeen85

published.Ifcliniciansaretooptforuseofthisdevice,theywouldexpecttoknowhow86

measurementscomparewithagoldstandardaswellaswithconventionaloscillometry.87

Oneofthemostwidelyassessedconventionaloscillometricdeviceshasbeenthe88

Dinamap(Critikon,Tampa,Fl,USA).AvarietyofstudiesevaluatingtheDinamap1846sx,89

Dinamap8100,andtheDinamap8300,specificallydevelopedforclinicalveterinarypatients90

in1993,havebeenpublished(Binnsandothers1995,Bodeyandothers1994,Bodeyand91

others1996,BodeyandMitchell1997,Gainsandothers1995,Habermanetal.2004,92

Habermanandothers2006,Meursandothers1996,GrosenbaughandMuir1998,Sawyer93

andothers2004)butnostudyhasevaluatedthisdeviceinaccordancewiththe2007ACVIM94

guidelinessodirectcomparisonwithfuturedevicesisdifficult.95

Theaimofthisstudywastoevaluatethehigh‐definitionoscillometricdevice,96

MemodiagnosticMD_15/90Pro,andtheconventionaloscillometricdevice,DinamapModel97

5

8300,comparedwithdirectarterialBPmeasurementinanesthetiseddogsbasedonthe98

guidelinesofthe2007ACVIMConsensusStatement.99

MaterialsandMethods100

Nineclient‐owneddogswererecruitedfrompatientsrequiringanaesthesiafor101

reasonsunrelatedtothestudyintheSmallAnimalClinic,DepartmentofClinicalVeterinary102

Medicine,VetsuisseFaculty,UniversityofBerne.Thestudyprotocolwasevaluatedand103

approvedbytheinstitution’sEthicsCommittee.Dogswererecruitedbyrequestingowner104

consentforparticipationinthestudyofdogsscheduledforasurgicalprocedure.The105

measurementswereperformedafterreachingastableplaneofanaesthesia,butpriortoany106

otherprocedures,inthesurgerypreparationroomwiththedogsindorsalrecumbency.For107

oscillometricdevices,theBPcuffwasplacedaroundthemidleftorrightantebrachium108

overlyingthemedianartery.Forconventionaloscillometricmeasurements,cuffsizewas109

selectedtoaccountforapproximately40%ofthecircumferenceofthelimbatplacement110

site.Forhigh‐definitionoscillometricmeasurement,thecuffusedwasselectedfromoneof111

thoseprovidedwiththedeviceaccordingtothemanufacturer’sguidelines.Carewastaken112

toensurethatmeasurementsweretakenattheleveloftheheartbaseandthatECG113

readingsshowedasinusrhythm.Fordirectarterialpressuremeasurement,theskinoverthe114

leftorrightdorsalhindpawwassurgicallyprepared,anda20‐or22‐gauge,1‐inchfluoro‐115

ethylene‐propylenecatheter(Jelco®2i.v.,SmithsMedicalInternationalLtd.,Kent,UK)was116

placedinthedorsalpedalartery.Thearterialcatheterwasconnectedtoadisposable117

transducerviaanon‐compliantsaline‐filledtubing.Thetransducerwasconnectedtoa118

monitorandattachedtoapressurised(300mmHg)bagofsaline(0.9%NaCl)solution.The119

catheterwasflushedintermittentlytoavoidbloodclots,andthesystemclearedofair120

bubbles.Thetransducerwasplacedattheleveloftheheartandzeroedtoatmospheric121

6

pressurebeforestartingtheprocedure.Priortoallmeasurements,thedirectBPmonitor122

andtheoscillometricdeviceswerecalibratedfrom0to200mmHgusingastandardaneroid123

manometerthatmetthestandardsfornonautomatedsphygmomanometersestablishedby124

theAAMI.Attheendofthestudy,thecalibrationwasrecheckedtoensurethattheir125

accuracywasmaintained.126

AtotalofeightconsecutivereadingsweretakensimultaneouslybydirectBP127

measurementandwitheachoftheoscillometricdevices(DinamapModel8300and128

MemodiagnosticMD_15/90Pro).Foreachsinglemeasurement,thesystolic(SAP),diastolic129

(DAP)andmean(MAP)bloodpressuresandtheheartratewererecorded.Otherdata130

recordedincludeddate,starttimeofthemeasurementsession,thecircumferenceofthe131

dog’slimb,thesizeofthebloodpressurecuff,anddrugsandintravenousinfusions132

administeredtothepatient.Atleastfivesecondselapsedbetweenconsecutive133

measurements.134

Throughouttheentirestudy,allmeasurementsweretakenbyasingleinvestigator,135

familiarisedwithalldevices,andtheprotocolforBPmeasurementsconformedtothe136

ACVIMconsensusstatement(Brownandothers,2007,Table2).Basedontheseguidelines,137

thefirstintheseriesof8consecutiveBPmeasurementswasdiscardedandnotusedfordata138

comparison.139

Statisticsandvalidation140

Simplelinearregressionanalysiswasusedtoevaluatetherelationshipsbetweenthe141

directvaluesandtheindirectvaluesobtainedwitheachoftheoscillometricdevices.The142

agreementbetweenoscillometricandsimultaneousdirectBPmeasurementsforSAP,DAP143

andMAPwereevaluatedusingBland‐Altmanplots(BlandandAltman1986,Blandand144

Altmann1995)inwhichthedifferencesbetweenthetwomeasurementswasplottedagainst145

7

themeanofthetwomeasurementsforeachsetofsimultaneousmeasurements.Thebias146

(meandifferencefromdirectBPvalues),precision(standarddeviationofdifferences)and147

the95%limitsofagreement(mean±2SD)werecalculated.Thepercentagesof148

measurementswithin5mmHg,10mmHgand20mmHgofthedirectmeasuresforboth149

indirectdeviceswerecalculated.Theindirectdeviceswereconsideredtopassvalidationif150

theymetallofthefollowingconditions(Brownandothers,2007):themeandifferenceof151

pairedmeasurementsforSAPandDAPtreatedseparatelyis±10mmHgorlesswitha152

standarddeviationof15mmHgorless;thecorrelationbetweenpairedmeasuresforSAP153

andDAPtreatedseparatelyis≥0.9acrosstherangeofmeasuredvaluesofBP;50%ofall154

measurementsforSAPandDAPtreatedseparatelyliewithin10mmHgofthedirectvalues;155

80%ofallmeasurementsforSAPandDAPtreatedseparatelyliewithin20mmHgofdirect156

values;dataareobtainedfornofewerthan8animals.Inaddition,thedeviceswere157

consideredtogivereliablereadingsonlyifthecoefficientofvariationforeachsetof7158

measurementsforSAPwasbelow20%(Brownandothers,2007).Analyseswereperformed159

usingstatisticalsoftware(Medcalc®v11.0.1,MedcalcSoftwarebvba,Belgium).160

Results161

Dogsrecruitedwerebetween3and11yearsold(meanage6.5±2.87years)andweighed162

between11.8and45.0kg.Readingswereobtainedforall72measurementswithboththe163

DinamapandtheMemodiagnosticdevice.AllsetsofvaluesforSAPhadacoefficientof164

variationof<20%foralldevices;therangesofcoefficientsofvariationforSAPwere1.09‐165

12.11%(median2.3%)fordirect,1.15‐13.22%(median3.07%)forDinamap,and1.87‐9.24%166

(median4.89%)forMemodiagnostic.Comparativestudiesofvaluesobtainedwith167

oscillometricanddirectmeasurementswereperformedafterdiscardingthefirstvalue168

8

(Brownandothers,2007),givingatotalof63simultaneousdataforeachofthetwo169

oscillometricdevices.170

Bland‐AltmanplotsrevealedaslightunderestimationofSAPandDAPand171

overestimationofMAPwiththeDinamap(Fig.1,Table1).ValuesforSAP,DAPandMAP172

werealloverestimatedwiththeMemodiagnosticandoverestimationincreasedforSAPand173

DAPwithincreasingpressures(Fig.2,Table1).Apositivecorrelationwasfoundbetweenall174

indirectandsimultaneouslymeasureddirectvalues(Figs.3,4).Thecorrelationwaspoor175

withtheMemodiagnostic(Table2,Fig.4).Althoughastrongcorrelationwasfoundwiththe176

Dinamap,thiswasslightlybelow0.9,requiredforvalidation(Table2,Fig.3).Themean177

differences(bias)betweendirectandindirectmeasuresweregreaterforthe178

MemodiagnosticthantheDinamap(Table2)althoughallwerewithin10mmHgrequiredfor179

validation.Theprecision(standarddeviationofthedifferences)waslessthan10mmHgfor180

theDinamapbutexceededthe15mmHgthresholdrequiredforvalidationwiththe181

MemodiagnosticforbothSAPandDAP(Table2).Thelimitsofagreementwerelikewisevery182

largefortheMemodiagnostic(Table2).Greaterthan75%ofoscillometricreadingswere183

within10mmHgandthevastmajoritywerewithin20mmHgofdirectvaluesfortheDinamap184

(Table2).However,onlybetween50and60%werewithin10mmHgfortheMemodiagnostic185

(Table2).Moreover,theMemodiagnosticdidnotfulfiltherequirementofover80%of186

valueswithin20mmHgforDAP.187

Discussion188

ThisstudycomparedBPbetweentwooscillometricdevicesanddirectmeasurements189

inanaesthetiseddogsbasedontheACVIMguidelines.Thisincludedastandardisedapproach190

tomeasurements(samepositionofanimals,samecuffsiteandsize,serialmeasurements191

withdiscardofthefirstmeasurement,asingleexaminer)withvalidationaccordingtothe192

9

suggestedguideline.Althoughdiseasestateandanaestheticprotocolmightsignificantly193

affectbloodpressure,thiswasconsideredirrelevanttotheaimofthestudyandnostudy194

inclusionlimitationswereenforcedinthisrespect.Ashortcomingofthisstudyisthatdogs195

wereevaluatedunderanaesthesiaandtherangeofBPswasrelativelynarrow(directSAP196

between76and137mmHg).Resultsofthisstudyarethereforeonlyvalidforanaesthetised197

dogswithpressureswithinthisrange.198

TheMemodiagnosticoscillometricdeviceisarelativelynewdeviceusinghigh199

definitionoscillometry.Therearecurrentlynopublicationsevaluatingthisdeviceindogsbut200

thedeveloperclaimsmanyadvantagestoconventionalindirectBPdevices(Egner2006a;201

Egner2006b,S+BMedVet1998).Contrarytoconventionaloscillometry,inwhichtheMAPis202

measured,andSAPandDAParecalculatedusinganalgorithmbasedontheoscillation203

curve,theMemodiagnosticperformsreal‐timeanalysisofarteryoscillationstoobtainpulse204

amplitudes.Otherpurportedbenefitsaretheelectronically‐controlledvaluesthatadaptto205

maintainlinearityduringdeflation,permittingreadingsfrom5to300mmHg,highsensitivity206

thatallowsmeasurementsfromminimalsignalsandheartfrequenciesofupto500beats207

perminute,andhigh‐speedanalysisthatallowsthedetectionofarrhythmias(S+BMedVet208

1998).Inapreviouslypublishedstudy,thisdevicewastestedforitsapplicationinthe209

cynomolgusmonkey(Schmeltingetal.2009),bothundergeneralanaesthesiaincomparison210

withtelemetryandinconsciousanimals.Inthisstudy,MAPwaslowerwiththe211

Memodiagnosticthanwithtelemetry.However,thisstudydidnotevaluatesimultaneously212

obtainedpairedreadingsandtheaccuracyofthereadingswasthereforenotassessed.213

TheDinamaphasbeenpreviouslyevaluatedinanesthetiseddogsinseveralstudies,214

mostofwhichfoundfavourableresultscomparedwithdirectmeasurements(Bodeyand215

others1994;Gainsandothers1995;GrosenbaughandMuir1998;Hamlinandothers1982;216

10

Meursandothers1996).However,thesestudieswereperformedpriortotheACVIM217

consensus,andevaluationprocedurevariedwidelybetweenstudies.218

Inthisstudy,theDinamapunderestimatedSAPandDAP,aswasfoundinprevious219

reports(GrosenbaughandMuir1998;Habermannandothers2006;Bodeyandothers1996).220

Incontrast,theMemodiagnosticoverestimatedSAPandDAP.Thecoefficientofvariationof221

consecutivevaluesforSAPsineachdogwasbelow20%withbothdevices,showing222

adequateconsistencyinreadingswitheachdevice.ThecorrelationbetweenDinamapand223

directmeasureswasnotcalculatedinsomepreviousstudiesandvariedsogreatlyinothers224

(RforSAPbetween0.24and0.908),notleastbecauseofvariationincuffsite,numberof225

consecutivemeasurements,positionofdogs,andBPranges,thatdirectcomparisonofdata226

betweenstudiesisdifficult(Bodeyandothers1994;Gainsandothers1995;Grosenbaugh227

andMuir1998;Hamlinandothers1982;Meursandothers1996).Asthisstudyusedthe228

sameprocedureforbothdevices,correlationcanbecomparedbetweenthetwodevices.229

NeitherdevicefulfilledthevalidationrequirementofR≥0.9.However,contrarytothe230

Memodiagnostic,theDinamapachievedhighcorrelationsandfelljustshortofthisvalidation231

criterion.232

Themeandifferences(bias)betweenSAPandDAPvaluesobtainedwiththeDinamap233

anddirectmeasurementswasgreaterthanthe10mmHgrequirementintwoprevious234

studies(Bodeyandothers1994;GrosenbaughandMuir1998).However,thiswasonlythe235

caseforhypertensivedogsbutnotfornormo‐orhypotensivedogsinoneofthesestudies236

(GrosenbaughandMuir1998),andonlyfortailanddistalhindlimbbutnotforproximal237

hindlimbcuffsitesintheotherstudy(Bodeyandothers1994).Bias(meandifference)for238

DAPrangedtovaluesupto13mmHginthesestudies.Wefoundaverylowbiasforthe239

11

DinamapandsomewhathighervaluesfortheMemodiagnostic,indicatingbetteraccuracy240

withtheDinamap.241

Thestandarddeviationsofthedifferences(precision)forSAPandDAPwerewithin242

15mmHgfortheDinamapaswasthecaseinapreviousstudyevaluatingBPoverawide243

pressurerangeinanaesthetiseddogs(GrosenbaughandMuir1998).However,standard244

deviationsfortheMemodiagnosticdeviceweregreaterthan15mmHg,indicatinga245

relativelypoorprecision.246

Thevalidationcriteriathat>50%and>80%ofSAPandDAPvaluesmustliewithin10247

and20mmHgofdirectmeasurements,respectively,hasnotbeenpreviouslyevaluatedfor248

theDinamapindogsunderanaesthesia.Inonestudywithconsciousbeagles,neitherthe249

DinamapnorDopplermetthisstandardfor10mmHg(Habermannandothers2006)despite250

thefactthatthiscriterionislessstringentthanAAMIrequirementsofhumanindirectBP251

devices.Inthepresentstudy,theDinamapfarsurpassedthisrequirementbutthe252

Memodiagnosticfellshort.253

DespitethepurportedadvantagesoftheMemodiagnostic,thisdevicedidnotmeet254

theACVIMrequirementsforbloodpressuredevicevalidationinthepresentstudy,and255

demonstratedpoorcorrelationwithdirectmeasuresinanaesthetiseddogs.Moreover,256

accuracyandprecisionwerepoorerthanwithDinamap,leadingtolimitsofagreementthat257

maybeclinicallyunacceptable.Furthermore,thepercentagesofmeasuredvalueswithin5,258

10or20mmHgofthoseobtaineddirectlywereverylowcomparedwiththoseachievedwith259

theDinamap.AlthoughtheDinamapmetalmostallvalidationcriteria,bothdevicesarelikely260

tofairlesswellinsatisfyingcriteriawhenmeasurementsaretakeninconsciousdogsand261

acrossagreaterrangeofBPvalues.TheACVIMConsensusStatementpanelrecognizesthat262

theguidelinesmaybesorigorousastoexcludeanydevicepresentlyinusewhenappliedto263

12

consciousdogsandcats(Brownandothers2007).Theresultsofthepresentstudysuggest264

thatthecriterionforcorrelationmayindeedbetoohighasitcouldnotbesatisfiedunder265

thenarrowconditionsofcontrolledmeasurementsinanaesthetiseddogsinthepresent266

study.However,thecriteriaforthepercentageofvalueslyingwithin10and20mmHgof267

directmeasurementsmaybetoolenient,inparticularbecauseadifferenceof20mmHgmay268

significantlyaffecttheclinicalinterpretationofresultsinpatients.269

270

13

270

Acknowlegements271

TheauthorswouldliketothankDr.MarcusClaussforhisassistance.272

14

273

References274

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15

Haberman,C.E.,Kang,C.W.,Morgan,J.D.&Brown,S.A.(2006)Evaluationofoscillometric317 andDopplerultrasonicmethodsofindirectbloodpressureestimationinconscious318 dogs.CanadianJournalofVeterinaryResearch70,211‐217319

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Stepien,R.L.,Rapoport,G.S.,Henik,R.A.,Wenholz,L.&Thomas,C.B.(2003)Comparative339 diagnostictestcharacteristicsofoscillometricandDopplerultrasonographicmethods340 inthedetectionofsystolichypertensionindogs.JournalofVeterinaryInternal341 Medicine17,65‐72342

343

16

Table1:Agreementandcorrelationofbloodpressuresmeasuredbyuseoftwo343 oscillometricdevicesandthosemeasureddirectlyin9anaesthetiseddogs.344

345 Dinamap MemodiagnosticParameter ACVIM

recommendedlimitsfor

systolicanddiastolicvalues(Brownandothers2007)

Systolic Diastolic Mean Systolic Diastolic Mean

Correlation(R) ≥0.9 0.8850* 0.8734* 0.8605* 0.5546* 0.7186* 0.5671*Bias(meandifference,mmHg)1

≤±10 1.78 1.82 ‐3.90 ‐5.80 ‐5.19 ‐2.90

Precision(Standarddeviation,mmHg)1

≤15 7.56 7.30 8.14 17.76 15.33 10.45

Limitsofagreement(mmHg)

none ‐13.0to16.6

‐12.5to16.1

‐19.9to12.1

‐40.6to29.0

‐35.2to24.9

‐23.4to17.6

≤5mmHg2 none 57.1% 47.6% 49.2% 22.2% 42.8% 26.9%≤10mmHg2 ≥50% 76.2% 88.9% 76.2% 52.4% 58.7% 61.9%≤20mmHg2 ≥80% 100% 98.4% 98.4% 82.5% 76.2% 96.8%Range3(mmHg) 76‐137 41‐83 53‐97 64‐124 36‐81 45‐96*Significantlinearrelationship(P<0.001)346 1.Direct–indirectmethod347 2.Percentageofindirectlyobtainedvalueswithin5,10or20mmHgofthedirectvalues348 3.Rangeofvaluesobtainedbydirectarterialmeasurements349 350