functional exercise testing_ ventilatory gas analysis

9/4/2015 Functionalexercisetesting:Ventilatorygasanalysis

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OfficialreprintfromUpToDate www.uptodate.com2015UpToDate

AuthorFrankGYanowitz,MD

SectionEditorWilsonSColucci,MD

DeputyEditorSusanBYeon,MD,JD,FACC

FunctionalEXERCISE testing:Ventilatorygasanalysis

Alltopicsareupdatedasnewevidencebecomesavailableandourpeerreviewprocessiscomplete.Literaturereviewcurrentthrough:Mar2015.|Thistopiclastupdated:Jun04,2012.

INTRODUCTIONAlthoughexercisephysiologistsandpulmonaryphysicianshaveusedexercisetestingwithrespiratorygasanalysisformanyyears,itsapplicationtocardiovascularmedicineisrelativelynew.Thepurposeofthisreviewistodiscussthephysiologicbasisforfunctionalexercisetesting,methodologicconsiderations,andclinicalapplications.Cardiologistshaveusedthistechniquemostoftenintheevaluationandmanagementofpatientswithheartfailure.(See"ExercisecapacityandVO2inheartfailure".)

PHYSIOLOGICASPECTSOFEXERCISEAnunderstandingofexercisephysiologyandtheFickequationisaprerequisiteforappreciatingtheutilityoffunctionalexercisetesting.(See"Exercisephysiology".)

AerobicparametersTheFickequationstatesthatoxygenuptakeequalscardiacoutputtimesthearterialmixedvenousoxygencontentdifference.Thisisusuallyexpressedasfollows:

Vo =(SVxHR)x(CaO CvO )

whereVo istheoxygen(O )uptake,SVisthestrokevolume,HRisheartrate,CaO isarterialoxygencontent,andCvO isthemixedvenousoxygencontent.OxygenuptakeisoftennormalizedforbodyweightandexpressedinunitsofmLO2/kgpermin.Onemetabolicequivalent(MET)istherestingoxygenuptakeinasittingpositionandequals3.5mL/kgpermin.

Atmaximalexercise,theFickequationisexpressedasfollows:

Vo max=(SVmaxxHRmax)x(CaO maxCvO min)

TheVo maxreflectsthemaximalabilityofapersontotakein,transport,anduseoxygen,anditdefinesthatperson'sfunctionalaerobiccapacity.Vo maxhasbecomethe"goldstandard"laboratorymeasureofcardiorespiratoryFITNESS andisthemostimportantparametermeasuredduringfunctionalexercisetesting.AlthoughsomeinvestigatorsinsistthataVo plateauoccursatnearmaximalexercise,thisisnotalwaysseen.Ithasbeensuggestedthattheterm"peakVo "beusedinsteadofVo maxtodefinethissituation[1].

SeveralimportantchangesoccurintheFickequationasahealthypersongoesfromresttomaximalexercisebeforeandafterexercisetraining(figure1)[2]:

Functionalaerobicimpairment(ie,exerciseintolerance)isdefinedasanabnormallylowVo max.Thiscanoccur

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TheVo maxresponsetoexerciseislinearuntilmaximalVo isachieved.Inmanyindividuals,thereisaplateauatnearmaximalexercisebeyondwhichtheVo doesnotchange.ExercisetrainingenablesthepersontoachieveagreatermaximalworkloadandahigherVo max.

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Theheartrateresponseislinearuptoamaximalheartratethatapproximatelyequals"220beats/minage."Aftertraining,theheartrateisloweratrestandateachstageofexercise,butthemaximalheartratedoesnotchange.

Thestrokevolumeresponseiscurvilinear,increasingearlyinexercisewithlittlechangethereafter.Thetrainingeffectincreasestherestingstrokevolumeandthestrokevolumeateachworkload.

TheavO contentdifferencewidensasthemixedvenousO contentfallssincearterialO contentdoesnotchangeinnormalsubjects.ThemaximalavO contentdifferenceincreasesaftertraining.

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withanyfactorthataffectsoneormoreofthefourparametersoftheFickequationthatdetermineVo max:areductioninmaximalheartrate,maximalstrokevolume,ormaximalCaO oranincreaseinminimalCvO (figure2).Asanexample,themajorfactorlimitingVo maxinpatientswithheartfailure(HF)isthemarkedreductioninstrokevolumeresponsetoexercisewithsmallerreductionsinmaximalheartrateandmaximalavO contentdifference[35].

Otherconditionsthatcancompromisestrokevolumearesegmentalwallmotionabnormalitiesandvalvularstenosisorregurgitation.Ontheotherhand,diseasesofthelungs,skeletalmuscles,andhematologicsystemoftenhaveaprofoundeffectonVo maxbyaffectingarterialormixedvenousoxygencontent.

AnaerobicparametersAlthoughthereisstillconsiderabledebateintheliteratureconcerningthevalidityoftheventilatoryanaerobicthreshold(VAT),functionalexercisetestingoftenincludessuchmeasurementsbecauseitisclinicallyusefulinassessingfunctionalimpairmentinpatientswithHF[1,4,6,7].

Duringtheinitial(aerobic)phaseofaprogressiveEXERCISE test,whichlastsuntil50to60percentofVo maxisreached,expiredventilation(VE)increaseslinearlywithVo andreflectsaerobicallyproducedCO inthemuscles(figure3).Bloodlactatelevelsdonotchangesubstantiallyduringthisphase,sincemusclelacticacidproductionisminimal.

Duringthelatterhalfofexercise,anaerobicmetabolismoccursbecauseoxygensupplycannotkeepupwiththeincreasingmetabolicrequirementsofexercisingmuscle.Atthistime,thereisasignificantincreaseinlacticacidproductioninthemusclesandinthebloodlactateconcentration.TheVo attheonsetofbloodlactateaccumulationiscalledthelactatethresholdoranaerobicthreshold.

Intheperipheralblood,almostallthelacticacidisbufferedbysodiumbicarbonateaccordingtothefollowingreactions:

Lacticacid+NaHCO =Nalactate+CO +H O

TheexcessCO producedduringthebufferingprocessisaddedtotheaerobicallyproducedCO ,causingexpiredventilationtoincreasemoresteeplyduringthelaterstagesofexercise.Itisduringthisphasethatexercisingsubjectsbegintoexperiencedyspnea.

Becausethechangeinexpiredventilationattheonsetofanaerobicmetabolismisreasonablywelldefined,noninvasivemethodshavebeendevelopedtodetectthistransition[7].TheVo attheonsetofthisventilatorychangeisappropriatelycalledtheventilatorythreshold(VAT)(figure3).However,thevalidityofthesenoninvasivemeasuresandwhetherornotatruethresholdexistsremaincontroversial.

METHODSOFFUNCTIONALEXERCISETESTINGSeveraldifferentmethodsexistformeasuringventilationandrespiratorygasparametersduringexercise.Mostclinicalsystemsrelyonbreathbybreathanalysistechniquesbecausetheyprovidethebestmeasuresofthemetabolicresponsetoexercise.

GasanalysistechniquesThreebasicparametersarecontinuouslymonitoredatthemouthpieceduringabreathbybreathexercisestudy:

Anonrebreathingvalveisconnectedtothemouthpiecetopreventmixingofinspiredandexpiredair.Oxygenandcarbondioxidegasanalyzersareusuallyincorporatedina"metaboliccart"designedspecificallyforfunctionaltesting.Respiratoryvolumesarecomputedbyintegratingtheairflowsignalsoverthetimeofinspirationandexpiration.BreathbybreathvolumesofO intake,CO output,andexpiredventilationareobtainedbyintegratingthecontinuousvariablesoverthetimecourseofinspiration(forO ),andexpiration(forCO andexpiredventilation[VE]).Averageminutevolumesarederivedfromthebreathbybreathdatamultipliedbytherespiratoryrate.The

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PercentO 2PercentCO 2Respiratoryairflow

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gasvolumesobtainedunderambientconditionsarethenconvertedtoSTPD(standardtemperatureandpressure,dry)conditionsusingtheappropriateconversionequations.

ExercisetestprotocolsManydifferentprotocolsareusedforfunctionaltesting.(See"ExerciseECGtesting:PerformingthetestandinterpretingtheECGresults".)Thepurposeofthetestandthefunctionalcapabilitiesofthepatientdeterminethechoiceofprotocol.Inevaluatingpatientswithheartfailure(HF),bothbicycleandtreadmillprotocolshavebeenused(figure4).

Therateofworkloadprogressionissomewhatarbitrary,althoughithasbeensuggestedthatoptimalexercisedurationforfunctionalassessmentonthebicycleisbetween8and17minutes[8].Bicycleworkisquantifiedinwattsorinkilopondmeterspermin(kpm/min1wattequalsabout6kpm/min).TheinitialworkloadforpatientswithHFpatientsisusually20to25wattsandincreasedby15to25wattseverytwominutesuntilmaximalexertionisreached.Alternatively,theworkloadcanbecomputercontrolledforelectronicallybrakedbicycleergometers,andarampprotocol(eg,increasingby10watts/min)isoftenused.

ThemodifiedNaughtonprotocolisrecommendedfortreadmillexercisetestinginpatientswithHF[9].Thisprotocolisdesignedtoincreasetheworkloadbyapproximately1metabolicequivalent(MET)(3.5mLO /kg/min)foreachtwominutestage.

Patientswithheartdiseaserequirecontinuouselectrocardiogrammonitoringandfrequentbloodpressuremeasurementsduringexercisetesting.Handsignals(eg,onetofivefingersforperceivedintensityandthumbsdowntostop)areusedbythepatientduringexercise,sinceverbalcommunicationisusuallynotpossiblewiththemouthpieceapparatus.

Symptomsatmaximalexercisethatresultintestterminationincludemusclefatigue,exhaustion,extremedyspnea,andlightheadedness.Cardiacarrhythmiasareusuallynotanindicationtostopthetestunlesssustainedtachyarrhythmiasdeveloporthephysicianmonitoringthetestfeelsthatfurtherexerciseiscontraindicated.

Adecreaseinsystolicbloodpressurebelowtherestingpressureisasignofsevereleftventriculardysfunctionandanindicationtostopthetest.However,manypatientswithHFfailtosignificantlyincreasetheirsystolicpressureduringexercisebecauseofleftventriculardysfunction.

VentilatoryanaerobicthresholddeterminationThereareseveralmethodsforestimatingtheventilatorythreshold(VAT)fromtherespiratorygasdata[10].TheVATortheVo attheonsetofanaerobicmetabolismisvisuallyidentifiedastheonsetofadisproportionateriseinVE/Vo relativetoVE/Vco .ThisoccursbecauseCOproductionratherthanO consumptionisdrivingventilationariseinVE/Vo withoutachangeinVE/VcoindicatesthatventilationisincreasinginparallelwiththeincreasedCO productionthatoccurswithanaerobicmetabolism.

TheVATisusuallyvisuallydetectedfromtheplottedbreathbybreathdata.TheVATcanalsobevisuallyidentifiedasadisproportionateriseofVco orVErelativetoVo oradisproportionateriseinendtidalO relativetoendtidalCO .

Unfortunately,thereisconsiderableinterandintraobservervariabilityinthevisualdetectionoftheonsetofanaerobicmetabolismfromthebreathbybreathdata[11].Toovercomethisproblem,computerdetectionalgorithmshavebeendevelopedtomoreobjectivelymeasuretheanaerobicthreshold.Onesuccessfulapproachiscalledthe"Vslopemethod"(figure5)[12].

Withthismethod,thebreathbybreathVco dataareplottedagainstVo ,andthecomputerselectstheupperandlowerslopesbyaleastsquarelinearregressiontechnique.Theintersectionofthetwoslopesidentifiestheanaerobicthreshold.OnecanalsovisuallyselectthebreakpointfromtheplotofVco versusVo withlessambiguitythanwhenusingtheventilatoryequivalentdata.

CLINICALAPPLICATIONSTheAmericanCollegeofCardiology/AmericanHeartAssociation(ACC/AHA)UpdateofPracticeGuidelinesforEXERCISE Testing,publishedin2002,listthefollowingindicationsfor

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orderingafunctionalVo exercisetest(table1)[13,14]:

ThefunctionalVo exercisetestisaglobaltestofapatient'scardiorespiratorycapacity,sinceitreflectstheentireoxygentransportsystembeginningwiththelungsandpulmonarycirculation,includingtheheart,theoxygencarryingcapacityoftheblood,theperipheralcirculation,andtheskeletalmuscles.ThisobjectiveglobalassessmentoffersadvantagesoverothermethodstoassesstheseverityofHF:

Thus,theexercisetestisoftenhelpfulforclassifyingdiseaseseverityfortreatmentdecisionsandinthedifferentialdiagnosisofexerciseintoleranceandsymptomsofdyspneaandfatigue(figure2).KnowledgeofthefactorsthatcanadverselyaffecttheFickequationparametersandresultinalowVo maxcombinedwiththeresultsoffunctionalexercisetestingandotherancillarytests(eg,pulmonaryfunctiontests)oftenleadstothecorrectdiagnosis.

PrognosisofheartdiseaseTheparametersobtainedduringfunctionalexercisetestingalsohaveprognosticimportance.SeveralstudieshavefoundthatventilatoryparametersarebetterpredictorsofHFmortalitythanVo max[15,16].Inastudyof470patients,forexample,anabnormalelevationintheratioofpeakminuteventilationtoCO production(VE/Vco 44.7)wasthestrongestpredictorofdeathduring1.5yearfollowup[15].

Anenhancedventilatoryresponsetoexerciseisamarkerofdecreasedventilatoryefficiency,andispredictiveofoutcomeinpatientswithpreservedexercisecapacity.Inonestudyof123patientswithaVo max18mL/kgperminute,thethreeyearsurvivalwassignificantlylowerinthosewithaVE/Vco >34(57versus93percentforVE/Vco 34)[16].(See"ExercisecapacityandVO2inheartfailure".)

Moststudiesoffunctionalexercisetestinginheartfailurefocusedprimarilyonpatientswithsystolicdysfunction.TheprognosticimportanceofpeakVo andVE/Vco wasevaluatedinamixedpopulationof409HFpatientswithbothsystolicanddiastolicdysfunction[17].DependinguponthedefinitionofdiastolicHFthatwasapplied(ie,HFwithanleftventricularejectionfraction40,45or50percent),thenumberofpatientswithdiastolicHFandtheoptimalpredictorsofoutcomevaried.However,regardlessofwhichdefinitionwasused,bothpeakVo andtheVE/Vco slopewerepredictorsofoneyeareventfreesurvival(mortalityandcardiacrelatedhospitalization)inpatientswithdiastolicHF.

AnobjectivegradingsystemthatisbaseduponvaluesofVo maxandtheanaerobicthresholdhasbeenproposedthatisespeciallyapplicabletopatientswithchronicHF(table3)[18].BecauseofthecloserelationshipbetweenVo maxandthemaximalcardiacindex,thegradingsystemprovidesanexcellentmeasureofdiseaseseverity.

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Evaluationofexercisecapacityandresponsetotherapyinpatientswithheartfailure(HF)whoarebeingconsideredforhearttransplantation.AreproducibleVo maxoflessthan10to12mL/kgperminisoneoftheminimumrequirementsforconsiderationfortransplantation.(See"Indicationsandcontraindicationsforcardiactransplantation".)

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Assistanceinthedifferentiationofcardiacversuspulmonarylimitationsasacauseofexerciseinduceddyspneaorimpairedexercisecapacitywhenthecauseisuncertain.

Evaluationofexercisecapacitywhenindicatedformedicalreasonsinpatientsinwhomtheestimatesofexercisecapacityfromexercisetesttimeorworkrateareunreliable.

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ThetraditionalNewYorkHeartAssociationclassificationoffunctionalimpairmentinHFisnotalwaysaccuratebecauseitisbaseduponapatient'ssymptomsratherthanonobjectivecriteria(table2)[5].

Restingcentralhemodynamics,suchascardiacindex,ejectionfraction,andpulmonarycapillarywedgepressuresdonotalwayscorrelatewellwithfunctionalimpairmentmeasuredduringexercisetesting[7].

ThesymptomsofexerciseintoleranceinHF,suchasdyspneaonminimalexertion,fatigue,orboth,resultfromacomplexinterplayofmechanismsoriginatingfromboththecentralandperipheralcomponentsoftheoxygentransportsystem.Thesesymptomsarenonspecificandmayalsobeduetomedicationsideeffectsorothercoexistingconditionsthatmayormaynotberelatedtotheunderlyingheartdisease.

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Thisclassification,althoughwidelyused,canbecriticizedbecauseitfailstoconsiderage,sex,andweightdifferencesinVo maxthatoccurinnormalsubjects.Vo maxdeclineswithageandislowerinwomenthaninmenasaresult,itmaybemoreappropriatetouseageandsexspecificnormalvaluesandtoclassifyimpairmentasapercentagereductionfromthesenormalvalues.FormulasforpredictingVo maxinnormalsedentaryadultshavebeenpublishedforbothcycleergometryandtreadmilltesting[10].

FunctionalEXERCISE testingmayhavelongtermpredictivevalueinpatientswithcoronaryheartdisease.Thiswasillustratedinastudyofover12,000menwhowerereferredforcardiacrehabilitation(postmyocardialinfarction,postcoronaryarterybypassgraftsurgery,ornewischemicheartdisease)[19].Atamedianfollowupof7.9years,Vo max22mL/kgperminwereassociatedwithadjustedhazardratiosforcardiacdeathof1.0,0.62,and0.39,respectivelysimilarvalueswerenotedforallcausemortality.Theonlyothersignificantpredictorsofcardiacmortalityinthedifferentgroupsweresmokinganddigoxintherapy.

Itisimportantthatphysiciansperformingthesetestsunderstandthedifferentproceduresforanalyzingandinterpretingtherespiratorygasdata.Knowledgeofcalibrationtechniquesandequipmentmaintenanceisalsoanimportantprerequisiteinprovidingaccuratefunctionalassessmentsintheexerciselaboratory.ItislikelythatthenumberofexerciseVo studieswillincreaseinthefutureasnewandinnovativetherapiesforchronicHFbecomeavailable.

SUMMARY

UseofUpToDateissubjecttotheSubscriptionandLicenseAgreement.

REFERENCES

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TheFickequationstatesthatoxygenuptakeequalscardiacoutputtimesthearterialmixedvenousoxygencontentdifference.(See'Aerobicparameters'above.)

TheVo maxreflectsthemaximalabilityofapersontotakein,transport,anduseoxygen,anditdefinesthatperson'sfunctionalaerobiccapacity.Vo maxhasbecomethe"goldstandard"laboratorymeasureofcardiorespiratoryFITNESS andisthemostimportantparametermeasuredduringfunctionalexercisetesting.AlthoughsomeinvestigatorsinsistthataVo plateauoccursatnearmaximalexercise,thisisnotalwaysseen.Ithasbeensuggestedthattheterm"peakVo "beusedinsteadofVo maxtodefinethissituation.(See'Aerobicparameters'above.)

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ThemajorfactorlimitingVo maxinpatientswithheartfailure(HF)isthemarkedreductioninstrokevolumeresponsetoexercisewithsmallerreductionsinmaximalheartrateandmaximalavO contentdifference.(See'Aerobicparameters'above.)

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ThemodifiedNaughtonprotocolisrecommendedfortreadmillexercisetestinginpatientswithHF.(See'Exercisetestprotocols'above.)

AreproducibleVo maxoflessthan10to12mL/kgperminisoneoftheminimumrequirementsforconsiderationfortransplantation.(See'Clinicalapplications'aboveand"Indicationsandcontraindicationsforcardiactransplantation".)

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Theexercisetestisoftenhelpfulforclassifyingdiseaseseverityfortreatmentdecisionsandinthedifferentialdiagnosisofexerciseintoleranceandsymptomsofdyspneaandfatigue(figure2).(See'Clinicalapplications'above.)

AnobjectivegradingsystemthatisbaseduponvaluesofVo maxandtheanaerobicthresholdhasbeenproposedthatisespeciallyapplicabletopatientswithchronicHF(table3).(See'Prognosisofheartdisease'above.)

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1. BrooksGA.Anaerobicthreshold:reviewoftheconceptanddirectionsforfutureresearch.MedSciSportsExerc198517:22.

2. MitchellJH,BlomqvistG.Maximaloxygenuptake.NEnglJMed1971284:1018.3. SimontonCA,HigginbothamMB,CobbFR.Theventilatorythreshold:quantitativeanalysisofreproducibility

andrelationtoarteriallactateconcentrationinnormalsubjectsandinpatientswithchroniccongestiveheartfailure.AmJCardiol198862:100.

4. MatsumuraN,NishijimaH,KojimaS,etal.Determinationofanaerobicthresholdforassessmentoffunctionalstateinpatientswithchronicheartfailure.Circulation198368:360.

5. NeubergGW,FriedmanSH,WeissMB,HermanMV.Cardiopulmonaryexercisetesting.Theclinicalvalueofgasexchangedata.ArchInternMed1988148:2221.

6. DavisJA.Anaerobicthreshold:reviewoftheconceptanddirectionsforfutureresearch.MedSciSportsExerc198517:6.

7. JenningsGL,EslerMD.Circulatoryregulationatrestandexerciseandthefunctionalassessmentofpatientswithcongestiveheartfailure.Circulation199081:II5.

8. BuchfuhrerMJ,HansenJE,RobinsonTE,etal.Optimizingtheexerciseprotocolforcardiopulmonaryassessment.JApplPhysiolRespirEnvironExercPhysiol198355:1558.

9. NAUGHTONJ,SEVELIUSG,BALKEB.PHYSIOLOGICALRESPONSESOFNORMALANDPATHOLOGICALSUBJECTSTOAMODIFIEDWORKCAPACITYTEST.JSportsMedPhysFitness19633:201.

10. WassermanK,HansenJE,SueDY,WhippBJ.PrinciplesofExerciseTestingandInterpretation,Lea&Febiger,Philadelphia1987.

11. YehMP,GardnerRM,AdamsTD,etal."Anaerobicthreshold":problemsofdeterminationandvalidation.JApplPhysiolRespirEnvironExercPhysiol198355:1178.

12. BeaverWL,WassermanK,WhippBJ.Anewmethodfordetectinganaerobicthresholdbygasexchange.JApplPhysiol(1985)198660:2020.

13. GibbonsRJ,BaladyGJ,BrickerJT,etal.ACC/AHA2002guidelineupdateforexercisetesting:summaryarticle:areportoftheAmericanCollegeofCardiology/AmericanHeartAssociationTaskForceonPracticeGuidelines(CommitteetoUpdatethe1997ExerciseTestingGuidelines).Circulation2002106:1883.

14. GibbonsRJ,BaladyGJ,BeasleyJW,etal.ACC/AHAGuidelinesforExerciseTesting.AreportoftheAmericanCollegeofCardiology/AmericanHeartAssociationTaskForceonPracticeGuidelines(CommitteeonExerciseTesting).JAmCollCardiol199730:260.

15. RobbinsM,FrancisG,PashkowFJ,etal.Ventilatoryandheartrateresponsestoexercise:betterpredictorsofheartfailuremortalitythanpeakoxygenconsumption.Circulation1999100:2411.

16. PonikowskiP,FrancisDP,PiepoliMF,etal.Enhancedventilatoryresponsetoexerciseinpatientswithchronicheartfailureandpreservedexercisetolerance:markerofabnormalcardiorespiratoryreflexcontrolandpredictorofpoorprognosis.Circulation2001103:967.

17. GuazziM,MyersJ,ArenaR.Cardiopulmonaryexercisetestingintheclinicalandprognosticassessmentofdiastolicheartfailure.JAmCollCardiol200546:1883.

18. WeberKT,JanickiJS..CardiopulmonaryEXERCISE Testing.In:PhysiologicPrinciplesandClinicalApplications,WBSaunders,Philadelphia1986.

19. KavanaghT,MertensDJ,HammLF,etal.Predictionoflongtermprognosisin12169menreferredforcardiacrehabilitation.Circulation2002106:666.

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GRAPHICS

Oxygenuptake,heartrate,andavO2contentdifferenceatrestandduringincreasinglevelsofexercise

WithEXERCISE andanincreaseinworkload,thereisanincreaseinoxygen(O2)uptake(upperpanel),heartrate(HR)(middlepanel),andavO2difference(lowerpanel).Exercisetrainingproducedanincreaseinthemaximaloxygenuptake(VO2max)thatcanbeachieved(upperpanel)andadecreaseinmaximalHRoccurringatanygivenworkload(dashedblueline,middlepanel).

DatafromMitchellJH,Blomqvist,G.Maximaloxygenuptake.NEnglJMed1971284:1018.

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DeterminantsofVO maxintheFickequation

VO :oxygen(O )uptakeSV:strokevolumeHR:heartratePiO :partialpressureinspiredO :FiO xPatmosphericCaO :arterialoxygencontentCvO :mixedvenousoxygencontent.

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VentilatoryandbloodlactateresponsetoEXERCISE

VentilatoryandbloodlactateresponsetoEXERCISE asafunctionofoxygenuptake(VO2)Theanaerobicthreshold(AT)indicatestheonsetofsignificantanaerobicmetabolismandtheproductionoflactate,whichoccursatapproximately50to60percentofVO2max.

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VentilatoryresponsesduringexerciseinHF

Ventilatoryresponsesinapatientwithheartfailurewhounderwentexercisetestingusingabicyleprotocolwitha10watt/minramp.Thecarbondioxideoutput(VCO2)paralleledtheoxygenuptake(VO2)untilminutesevenwhenitincreasedmorerapidlyduetotheanaerobiccomponent.

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Vslopemethodfordetermininganaerobicthreshold

Carbondioxideoutput(VCO2)isplottedasafunctionofoxygenuptake(VO2).Theintersectionofthetworegressionlinesindicatestheanaerobicthreshold.

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ACC/AHAguidelinesummary:Exercisetestingwithventilatorygasanalysis

ClassIThereisevidenceand/orgeneralagreementthatexercisetestingwithventilatorygasanalysisshouldbeperformedinthefollowingsettings:Toevaluateexercisecapacityandtheresponsetotherapyinpatientswithheartfailurewhoarebeingconsideredforhearttransplantation.

Toassistinthedifferentiationbetweencardiacandpulmonarycausesofexerciseinduceddyspneaorimpairedexercisecapacitywhenthecauseisuncertain.

ClassIIaTheweightofevidenceoropinionisinfavoroftheusefulnessofexercisetestingwithventilatorygasanalysisinthefollowingsetting:Toevaluateexercisecapacitywhenindicatedformedicalreasonswhenestimatedexercisecapacityfromexercisetesttimeorworkrateisunreliable.

ClassIIbTheweightofevidenceoropinionislesswellestablishedfortheusefulnessofexercisetestingwithventilatorygasanalysisinthefollowingsettings:ToevaluatetheresponsetospecifictherapeuticinterventionswhenimprovementinEXERCISE toleranceisimportantgoalorendpoint.

Todeterminetheintensityforexercisetrainingaspartofcomprehensivecardiacrehabilitation.

ClassIIIThereisevidenceand/orgeneralagreementthatexercisetestingwithventilatorygasanalysisisnotusefulinthefollowingsetting:Routineusetoassessexercisecapacity.

DatafromGibbonsRJ,BaladyGJ,BrickerJT,etal.ACC/AHA2002guidelineupdateforexercisetesting:summaryarticle:areportoftheAmericanCollegeofCardiology/AmericanHeartAssociationTaskForceonPracticeGuidelines(CommitteetoUpdatethe1997ExerciseTestingGuidelines).Circulation2002106:1883.

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Comparisonofthreemethodsofassessingcardiovasculardisability

Class

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CanadianCardiovascular

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Specificactivityscale

I Patientswithcardiacdiseasebutwithoutresultinglimitationsofphysicalactivity.Ordinaryphysicalactivitydoesnotcauseunduefatigue,palpitation,dyspnea,oranginalpain.

Ordinaryphysicalactivity,suchaswalkingandclimbingstairs,doesnotcauseangina.Anginawithstrenuousorrapidprolongedexertionatworkorrecreation.

Patientscanperformtocompletionanyactivityrequiring7metabolicequivalents,eg,cancarry24lbupeightstepsdooutdoorwork(shovelsnow,spadesoil)dorecreationalactivities(skiing,basketball,squash,handball,jog/walk5mph).

II Patientswithcardiacdiseaseresultinginslightlimitationofphysicalactivity.Theyarecomfortableatrest.Ordinaryphysicalactivityresultsinfatigue,palpitation,dyspnea,oranginalpain.

Slightlimitationofordinaryactivity.Walkingorclimbingstairsrapidly,walkinguphill,walkingorstairclimbingaftermeals,incold,inwind,orwhenunderemotionalstress,oronlyduringthefewhoursafterawakening.Walkingmorethantwoblocksonthelevelandclimbingmorethanoneflightofordinarystairsatanormalpaceandinnormalconditions.

Patientscanperformtocompletionanyactivityrequiring5metabolicequivalents,eg,havesexualintercoursewithoutstopping,garden,rake,weed,rollerskate,dancefoxtrot,walkat4mphonlevelground,butcannotanddonotperformtocompletionactivitiesrequiring7metabolicequivalents.

III Patientswithcardiacdiseaseresultinginmarkedlimitationofphysicalactivity.Theyarecomfortableatrest.Lessthanordinaryphysicalactivitycausesfatigue,palpitation,dyspnea,oranginalpain.

Markedlimitationofordinaryphysicalactivity.Walkingonetotwoblocksonthelevelandclimbingoneflightinnormalconditions.

Patientscanperformtocompletionanyactivityrequiring2metabolicequivalents,eg,showerwithoutstopping,stripandmakebed,cleanwindows,walk2.5mph,bowl,playgolf,dresswithout

[1][2]

[3]

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stopping,butcannotanddonotperformtocompletionanyactivitiesrequiring>5metabolicequivalents.

IV Patientswithcardiacdiseaseresultingininabilitytocarryonanyphysicalactivitywithoutdiscomfort.Symptomsofcardiacinsufficiencyoroftheanginalsyndromemaybepresentevenatrest.Ifanyphysicalactivityisundertaken,discomfortisincreased.

Inabilitytocarryonanyphysicalactivitywithoutdiscomfortanginalsyndromemaybepresentatrest.

Patientscannotordonotperformtocompletionactivitiesrequiring>2metabolicequivalents.Cannotcarryoutactivitieslistedabove(SpecificactivityscaleIII).

References:1. TheCriteriaCommitteeoftheNewYorkHeartAssociation.NomenclatureandCriteriafor

DiagnosisofDiseasesoftheHeartandGreatVessels,9thed,Little,Brown&Co,Boston,1994.p.253.

2. LucienC.Gradingofanginapectoris.Circulation197654:5223.3. GoldmanL,HashimotoB,etal.Comparativereproducibilityandvalidityofsystemsforassessing

cardiovascularfunctionalclass:Advantagesofanewspecificactivityscale.Circulation198164:1227.

Graphic52683Version8.0

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Functionalclassificationofpatientswithheartfailure

Class SeverityVO max,

mL/kg/min

Anaerobicthreshold,mL/kg/min

Maximalcardiacindex,L/min/m

A Nonetomild

>20 >14 >8

B Mildtomoderate

1620 1114 68

C Moderatetosevere

1015 811 46

D Severe 69 58 24

E Verysevere

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Disclosures:FrankGYanowitz,MDNothingtodisclose.WilsonSColucci,MDConsultant/AdvisoryBoards:Merck[Heartfailure(Enalapril)]Novartis[Heartfailure(Enalapril)]Janssen[Heartfailure]Mast[Heartfailure].EquityOwnership/Cardioxyl[Heartfailure].SusanBYeon,MD,JD,FACCNothingtodisclose.Contributordisclosuresarereviewedforconflictsofinterestbytheeditorialgroup.Whenfound,theseareaddressedbyvettingthroughamultilevelreviewprocess,andthroughrequirementsforreferencestobeprovidedtosupportthecontent.AppropriatelyreferencedcontentisrequiredofallauthorsandmustconformtoUpToDatestandardsofevidence.Conflictofinterestpolicy

Disclosures