GE CARESCAPE - Stopping the gas exchange measurement; Gas exchange measurement basics; Gas exchange measurement description; How to interpret the gas exchange values

Gasexchange
Stoppingthegasexchangemeasurement
1.Removethegasexchangeparameterwindowsfromthescreen.
YoucancontinuemeasuringairwaygasesandPatientSpirometrywiththesame
module.
Gasexchangemeasurementbasics
Gasexchangemeasurementdescription
TheE-COVXandE-CAiOVXmoduleswithgasexchangeoptionenablemonitoringof
O
2
consumption(VO
2
),CO
2
production(VCO
2
),energyexpenditure(EE)andrespiratory
quotient(RQ).
Toprovideanaccuratebreath-to-breathmeasurementofrespiratorygasexchange,
theE-COVXandE-CAiOVXmodulesalgorithmicallyintegratesidestreamgas
concentrations(CO
2
andO
2
)aswellasowsandvolumesgeneratedbyeachbreath.
ThisisdonewiththeD-lite(+)/Pedi-lite(+)owsensorinconjunctionwiththefast
paramagneticoxygensensorandtheinfraredgasbenchforCO
2
measurement.
Duetothesidestreammeasurementprinciple,thereisadelayofapproximately2.5
secondsinthemeasurement,causedbythetravelingtimeofthesamplethrough
thesamplinglinetothemodule.Themodulealgorithmicallysynchronizesthese
concentrationsandows.
Toobtaintheoxygenconsumptionofapatient,thegasexchangemodulemeasures
theamountofoxygenthatisinhaled,andsubtractstheexhaledamountfromit.
Carbondioxideproductionismeasuredbysubtractingtheamountofinhaledcarbon
dioxidefromtheamountofexhaled.Theseamountscanbeobtainedbymultiplying
eachmeasuredvolumesamplebythecorrespondinggasconcentration.
Toensurevolumemeasurementresultsthatarelesssensitivetoerrors,theHaldane
transformationisapplied.TheHaldanetransformationisbasedontheassumption
thatnitrogenisaninertgas,andanindividualwillneitherconsumenorproduceit,
exceptinthecaseofairemboli.Therefore,theamountofnitrogeninhaledisequal
totheamountexhaled.
Howtointerpretthegasexchangevalues
Thoughthemeasurementscanbemadeeasily,accuracyandreproducibilityof
resultsrequiresunderstandingofthebasicprinciplesofthemeasurementand
relatedphysiology.Furthermore,gasexchange,orindirectcalorimetry,issensitiveto
measurementerrors;theneedforroutineproceduresofqualitycontrolistherefore
emphasized.Despiteaccuratemeasurement,severalclinicalandphysiologicalfactors
inuencetheresultsofgasexchangemeasurementsandshouldbeconsideredin
interpretation.Inthisrespect,therelationshipbetweenventilationandgasexchange
isofcrucialimportance.Anyacutechangeinalveolarventilationwillbeimmediately
reectedinCO
2
production,whichwillnotmeasurethemetabolicproductionofCO
2
,
untilanewsteadystatehasbeenachieved.Similar,butshorter,transientwillalso
beseeninO
2
consumption.Analogously,acutechangesintissueperfusionmay
inuencebothtissueoxygenuptakeandremovalofCO
2
fromthetissues.
Pulmonarygasexchangemeasurementmeansmonitoringofoxygenconsumption
(VO
2
)andcarbondioxideproduction(VCO
2
).Basedonthesemeasurements,itis
possibletocalculatetherespiratoryquotient,RQ,whichistheratiobetweenCO
2
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