Philips Expression MR400 - Breath Rate Distortion

ExpressionMR400InstructionsforUse MonitoringCO2(LoFlo Option)7‐3
Breath Rate Distortion
Theeffectofrisetimedistortiontothegascurvebecomesapparentwhenthebreathingrate
increasessothat thetimeforafullinspiratoryorexpiratoryeventgetsshorter.Inthose
situations,duetotheeffectoftherisetime, thegascurvedoesnotreachthetrueend‐tidal
(or
firstinspiredvalue)andtheend‐tidalgasvaluemaythenbeunderestimated.Correspondingly,
thefirst inspiredvaluemaybeoverestimated.Belowisanexaggeratedillustrationoftheeffect.
Thebreathratelimitforaccuratelyresolvedend‐tidalgasvalues(atanI:Eratioof1:1)maybe
found
inAppendixA.TheeffectofotherI:Eratiosmaybecalculatedbydeterminingthelengthof
theshortestinspiratory/expiratoryeventthatcanberesolvedaccurately:
t
resolved
=60/(2xBR
limit
(1:1)
BR
limit
(I:E)=60/((I+E)xt
resolved
)
Thedifferenceintheseresultswhencomparedtotherisetime'sspecificationisthatrisetime's
onlytests10‐90%performance.Thisspecificationisfor(0+accuracy)to(100‐accuracy)%andis
thusmuchtougher.Theabilitytoproperlyresolveend‐tidalvaluescanbemeasuredbyusing
the
set‐updescribedinISO80601‐2‐55:2011figure201.101.Inshort,themethodconsistsof
samplinggasfromtwodifferentsourcesconnectedtoanelectricallycontrolledpneumaticvalve
topermitrapidswitchingbetweenthetwosources.Duringthetest,thevalveissettoswitchgas
sourceata
numberoffrequencies(simulatingtherangeofspecifiedbreathrates)andforeach
frequencytheend‐tidalvaluepresentedbythegasanalyzerisnoted.Fromadiagramofend‐tidal 
valueoverfrequency,thefrequencyatwhichthegasanalyzerisnolongerabletoresolveend‐
tidalvalues
accordingtospecificationisidentified.Thisabilitytoproperlyresolveend‐tidalvalues
islistedinthespecification.
2 SelecttheCO2VSbox.
TheCO2menuappears.Currentsettingsaredisplayed.
3 SelectZeroCal.
CalibrationwillbeginandPerformingCO2Zerowillbedisplayed.
Whencomplete,themessagewillberemoved.
Step Action
Fi error
Percent
Time
Et error
- - at gas sampling site
— as presented by gas analyzer