Functional Exercise Testing_ Ventilatory Gas Analysis
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9/4/2015 Functionalexercisetesting:Ventilatorygasanalysis
http://www.uptodate.com/contents/functionalexercisetestingventilatorygasanalysis?topicKey=CARD%2F3465&elapsedTimeMs=10&source=see_link&vie 1/16
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
NewYorkHeartAssociationfunctional
classification
CanadianCardiovascular
Societyfunctional
classification
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