LATEST Questions And Answers On
HMX Physiology
(NOTE:cThisciscnotcacduplicatecquestion)cCarboncmonoxide,cacproductcofccombustion,ciscact
oxiccgascthatchascancextremelychighcaffinitycforchemoglobinc(muchchighercthancthatcofcoxyg
encforchemoglobin);cconsequently,cascsooncascitcdissolvescincthecliquidcpartcofcbloodcatclowc
partialcpressure,citcdiffusescquicklycintocredcbloodccellscandcbindsctochemoglobin.cInccarbonc
monoxidec(CO)cpoisoning,cevencwithcveryclowcpartialcpressurecofcinspiredcCO,cCOcrapidlyc
bindsctochemoglobinc(Hgb),cleavingcaclowercfrac-cCORRECTccANSWER-
Decreasedcoxygenccontent
Explanation:
RecallcthatcthecO2ccontentcofcthecbloodciscthecsumcofcthecdissolvedcoxygencascwellcascthecox
ygencboundctocHgb.cThecO2ccontentcofcthecperson'scbloodcwouldcbeclow,cgivencthatcthecam
ountcofcO2cboundctocHgbciscdecreasedcbycCOcbinding.cGivencthatcthecmajoritycofcbloodcoxy
genccontentciscnormallyccomprisedcofcoxygencboundctocHgb,cthiscpersoncwouldclikelycsufferc
fromctissuechypoxemiac(lowcoxygencincthectissuescofcthecbody).
Ac22-year-
oldcpatientcarrivescincyourccliniccbycambulance.cThecemergencycmedicalctechniciansctellcyo
ucthatchiscfriendscfoundchimcunresponsivecwithcacneedlecinchiscarmcandccalledcforcancambul
ance.cHeciscfoundctochavecslow,cshallowcbreathingcandchascancarterialcpCO2cofc80c(normalc
=c40)candcpHcofc7.08c(normalc=c7.40).cAcmembercofcthecambulancecteamcstickscaroundcforc
acwhilecandcaskscyoucwhycyoucdidn'tcgivecthecpatientcHCO3-
ctocresolvecthecpatient'sclowcpH.cYouctellchercthat
thecpatient'scacidosisc-cCORRECTccANSWER-
bicarbonatecadministrationcwouldconlycincreasecthecalreadychighcpCO2.
Explanation
RespiratorycacidosiscisccausedcbycthecproductioncofcCO2cwithoutcadequatecremoval.cWhen
ctherecisctoocmuchcCO2,cthecfollowingcreactionciscdrivenctocthecright:
CO2c+cH2Oc⇌cH2CO3c⇌cHCO3-c+cH+
producingcH+candcHCO3-.cIfcHCO3-
ciscadministered,cthecreactioncwillcbecdrivencbackctocthecleft,cbutcthiscwillconlycresultcincincrea
sedcproductioncofcCO2,cwhichcdoescnotcaddresscthecproblemcofchighcCO2clevelscincthecbloo
dc(note:cthoughcpHcmaycnormalizectemporarilycwithcadditioncofcbicarbonate,cexcesscCO2cle
velscincthecbloodcarecstillcproblematic).cThisciscwhycHCO3-
,iscnotcancadequatec"buffer"cforcacrespiratorycacidosis.cInjectioncofcbicarbonatecwouldcprodu
c
cecacmetaboliccalkalosiscandcacrisecincthecpH,cwhichciscnotcpresentcincthisccase.
Ac26-year-
oldcmanciscinvolvedcincancautomobilecaccident.cHecarrivesctocthecemergencycdepartmentcwi
thcacbloodcpressurecofc122/73c(normalc=c90-120/60-
80).cOncrapidcassessmentcofcthecpatient,cyoucsuspectcthatcthatchechascabdominalcbleeding.
cYoucarecsurprisedcthatchiscbloodcpressureciscwithincthecnormalcrange.cYoucwouldcexpectctoc
findcthatchisc_____________cisc_____________,callowingchimctocmaintainchiscbloodcpress
ure.
heartcrate;cincreased
heartcrate;cdecreased
respiratorycrate;cincreased
respiratc-cCORRECTccANSWER-heartcrate;cincreased
Explanation
Incthisccase,cthecheartcrateciscmostclikelycelevatedcascaccompensationctocmaintaincthecbloodc
pressure,cascMAPc-
cCVPc=cQcxcSVR,candcQc=cHRcxcSVc(MAPc=cmeancarterialcpressure,cCVPc=ccentralcvenousc
pressure,cQc=cCardiaccoutput,cSVRc=csystemiccvascularcresistance,cHRc=cheartcrate,candcS
Vc=cstrokecvolume).cNotecthatcthecpatientcmaycbecbreathingcrapidlycduectocpain,cbutcthiscwo
uldcnotcservectocmaintainchiscbloodcpressure.
Ac49-year-
oldcwomancwascrescuedcfromcachousecfire.cThecfirefighterscreportcthatcshecwascrescuedcfro
mcacsmoke-
filledcroom.cYoucknowcthatcoxygenciscconsumedcandccarboncdioxidecproducedcduringccomb
ustion.cWhenclookingcatcthecpatient'scbloodcwork,cwhatcwouldcyoucexpectctocfind?c(selectcall
ccorrectcanswers)
highcpCO2,chighcserumcHCO3-clevels
highcpCO2,clowcserumcHCO3-clevels
highcpCO2,chighcserumcH+clevels
highcpCO2,clowcserumcH+clevelsc-cCORRECTccANSWER-highcpCO2,chighcserumcHCO3-
clevels
highcpCO2,chighcserumcH+clevels
Explanation
ForcancacidosisccausedcbychighclevelscofcCO2cincthecblood,chemoglobincactscascbuffercbycbi
ndingcprotonsc(H+).cConsequently,cwhencH+cremainsctrappedcincthecredcbloodccellcboundct
ochemoglobin,cHCO3-
ciscreleasedcintocthecbloodstream.cTherefore,cincancinstancecwherecacpatientchascrespirator
ycacidosisc(acidosisccausedcbychighclevelscofcCO2),cyoucwouldcexpectctocseechighclevelscofc
CO2candchighclevelscofcHCO3-
,.cWhilecbufferingcmitigatescthecimpactcofcthecrespiratorycacidosis,cthecconcentrationcofcprot
onscdoescincreasecasccarboniccacidcformscfromctheccombinationcofcCO2candcwater.
Ac66-year-
oldcfemalecarrivescincthecemergencycdepartmentccomplainingcofcheadache,closscofcappetit
e,candcfatigue.cBasedconcbloodwork,cyoucfindcthatcshechascancanion-
gapcmetaboliccacidosis.cWhichcofcthecstatementscbelowcbestcdescribescthecprocessescincth
eckidneycthatcwillceliminatecthecmetaboliccacidscthatchavecbuiltcupcinchercblood?
Anionscarecfilteredcout,cprotonscarecsecreted,candcbicarbonateciscreabsorbedcintocthecblood
stream.
Cationscarecfilteredcout,cprotonscarecsecreted,candcbicarbonatecisc-cCORRECTccANSWER-
Anionscarecfilteredcout,cprotonscarecsecreted,candcbicarbonateciscreabsorbedcintocthecblood
stream.
Explanation
Ancanion-
gapcmetaboliccacidosiscisccausedcbycthecproductioncofcacidscthatcdissociatecintocprotonscan
dcanionscthatcarecnotcHCO3-corcCl-
.cThesecanionscmustcbecfilteredcintocurinecincorderctocbecexcretedcfromcthecbody.cThecproton
scbeingcproducedcmustcalsocbecsecretedcfromctheccellscliningcthecrenalctubule,candcforceachc
protoncsecretedcbycthecrenalctubuleccells,cacmoleculecofcHCO3-
ciscabsorbedcintocthecbloodstreamcduectocthecmechanism cofccarboniccanhydrase.
Ac66-year-
oldcmancvisitscyoucincthecoutpatientcrenalcclinic.cHechascsignificantcrenalcdysfunctioncandchi
scurinecoutputchascsignificantlycdiminishedcovercthecpastcseveralcdays.cHecsayscthatcheccon
tinuesctocconsumechiscnormalcdietcandcdrinkcwatercatchiscnormalcrate.cHecreportscnocothercl
ossescofcwater,csuchcascvomiting,cdiarrhea,corcexcessivecsweating.cWhatcwouldcyoucexpec
tctochavechappenedcwithcregardsctochiscweight?
increased
decreased
stayedcthecsame
notcenoughcinformationc-cCORRECTccANSWER-increased
Explanation
Incacsteadycstatecsituation,cinputc=coutput.cIfcsomethingcchangesctoceithercofcthesecfactors,ct
hencthecsystemcwillcnoclongercbecincsteadycstate.cIfcthecoutputcofcacsubstancecdecreasescwit
houtcanycchangecincitscinput,cthiscwillcresultcincancincreasecincthecamountcofcthecsubstance.cI
ncthisccase,cthecpatient'scfluidcoutputchascdecreased,csocthecamountcofcfluidcinchiscbodycwillci
ncrease,ccausingchiscweightctocrise.
Ac67-year-
oldcmancarrivescincthecemergencycdepartmentccomplainingcofcfatigue,cconfusion,cheadach
e,candclosscofcappetite.cWhencyouctakechiscmedicalchistory,checrevealscthatchechascadvance
, dcrenalcdiseasecandcrecentlycmissedcacdialysiscappointment.cYoucordercacbasiccmetaboliccp
anelcandcancarterialcbloodcgas.cThesectestscrevealcthecfollowingcpertinentcvalues:
pHc=c7.22
PCO2c=c23cmEq/L
PO2c=c98cmEq/L
HCO3-c=c10cmEq/L
Na+c=c140cmEq/L
K+c=c5.0cmEq/L
Cl-c=c110cmEq/L
Thecpatient'scanioncgapcisc_________c-cCORRECTccANSWER-
25corc25cmEq/Lcorctwentycfivecorctwenty-fivecorctwentycfivecmEq/L
Explanation
Thectraditionalcanioncgapcisccalculatedcbycusingcthecfollowingcequation:cAGc=c([Na+]c+c[K+])
c-c([HCO3-]c+c[Cl-]).cThiscpatient'scanioncgapciscthereforec(140c+c5)c-
c(110c+c10)c=c25cmEq/L.cAcnormalcrangecofcthecanioncgapciscbetweenc12candc16cmEq/Lc(alth
oughclabscmaycdiffercslightlyconcnormalcrangecdependingconcthecmeanscofcmeasurement),c
socthiscpatientchascancelevatedcanioncgap.
Ac72-year-
oldcmanciscsittingccomfortablycinchiscchaircreceivingcoxygencviacnasalccannulac(acdevicectocd
elivercsupplementalcoxygencviacthecnose)catc2cL/min.cHecisconcacnormalcdietcandciscincnocdist
ress.cWhatcdocyoucexpectchiscmajorcmetaboliccwastecproductsctocbecifchiscbodyciscprimarilyc
metabolizingccarbohydrates?
lacticcacid
ketocacids
SO4,cPO4
CO2c-cCORRECTccANSWER-CO2
Explanation
AerobiccmetabolismcofccarbohydratescproducescCO2.cAtcrest,cmostcindividualscrelyconcacmi
xcofcfuelcsourcescbutcproducecapproximatelyc200cml/mincofccarboncdioxidecfromcaerobiccme
tabolismcofccarbohydrate.cProteincmetabolismcproducescPO4candcSO4cwhilecfatcmetabolis
mcproducescketocacidscandcanaerobiccglucosecmetabolismcproducesclacticcacid.
Note:cthereciscacbaselineclevelcofcmetabolismcofcfatscandcproteinsc(especiallycincbetweencm
eals).
Acballooncwithcacsmallcradiuscwouldcseemctochaveclessccollapsingcforcecvs.cacballooncwithcac
largercradiusc(morecinflated).cHowciscthiscconsistentcwithcLaplace'scLaw,cgivencthatcyouclear
nedcincthecvideocthatcbubblescatcsmallercradiichavecgreatercpressurecthanconescatclargercrad
ii?
Tensioncandcradiuscchangecatcthecsamecratecforcacballoon,csocthatcpressurecinsidecthecballo
oncremainscconstantcovercacrangecofcradii.
Tensioncforcthecdifferentcsizecballoonsciscnotcconstant.
HMX Physiology
(NOTE:cThisciscnotcacduplicatecquestion)cCarboncmonoxide,cacproductcofccombustion,ciscact
oxiccgascthatchascancextremelychighcaffinitycforchemoglobinc(muchchighercthancthatcofcoxyg
encforchemoglobin);cconsequently,cascsooncascitcdissolvescincthecliquidcpartcofcbloodcatclowc
partialcpressure,citcdiffusescquicklycintocredcbloodccellscandcbindsctochemoglobin.cInccarbonc
monoxidec(CO)cpoisoning,cevencwithcveryclowcpartialcpressurecofcinspiredcCO,cCOcrapidlyc
bindsctochemoglobinc(Hgb),cleavingcaclowercfrac-cCORRECTccANSWER-
Decreasedcoxygenccontent
Explanation:
RecallcthatcthecO2ccontentcofcthecbloodciscthecsumcofcthecdissolvedcoxygencascwellcascthecox
ygencboundctocHgb.cThecO2ccontentcofcthecperson'scbloodcwouldcbeclow,cgivencthatcthecam
ountcofcO2cboundctocHgbciscdecreasedcbycCOcbinding.cGivencthatcthecmajoritycofcbloodcoxy
genccontentciscnormallyccomprisedcofcoxygencboundctocHgb,cthiscpersoncwouldclikelycsufferc
fromctissuechypoxemiac(lowcoxygencincthectissuescofcthecbody).
Ac22-year-
oldcpatientcarrivescincyourccliniccbycambulance.cThecemergencycmedicalctechniciansctellcyo
ucthatchiscfriendscfoundchimcunresponsivecwithcacneedlecinchiscarmcandccalledcforcancambul
ance.cHeciscfoundctochavecslow,cshallowcbreathingcandchascancarterialcpCO2cofc80c(normalc
=c40)candcpHcofc7.08c(normalc=c7.40).cAcmembercofcthecambulancecteamcstickscaroundcforc
acwhilecandcaskscyoucwhycyoucdidn'tcgivecthecpatientcHCO3-
ctocresolvecthecpatient'sclowcpH.cYouctellchercthat
thecpatient'scacidosisc-cCORRECTccANSWER-
bicarbonatecadministrationcwouldconlycincreasecthecalreadychighcpCO2.
Explanation
RespiratorycacidosiscisccausedcbycthecproductioncofcCO2cwithoutcadequatecremoval.cWhen
ctherecisctoocmuchcCO2,cthecfollowingcreactionciscdrivenctocthecright:
CO2c+cH2Oc⇌cH2CO3c⇌cHCO3-c+cH+
producingcH+candcHCO3-.cIfcHCO3-
ciscadministered,cthecreactioncwillcbecdrivencbackctocthecleft,cbutcthiscwillconlycresultcincincrea
sedcproductioncofcCO2,cwhichcdoescnotcaddresscthecproblemcofchighcCO2clevelscincthecbloo
dc(note:cthoughcpHcmaycnormalizectemporarilycwithcadditioncofcbicarbonate,cexcesscCO2cle
velscincthecbloodcarecstillcproblematic).cThisciscwhycHCO3-
,iscnotcancadequatec"buffer"cforcacrespiratorycacidosis.cInjectioncofcbicarbonatecwouldcprodu
c
cecacmetaboliccalkalosiscandcacrisecincthecpH,cwhichciscnotcpresentcincthisccase.
Ac26-year-
oldcmanciscinvolvedcincancautomobilecaccident.cHecarrivesctocthecemergencycdepartmentcwi
thcacbloodcpressurecofc122/73c(normalc=c90-120/60-
80).cOncrapidcassessmentcofcthecpatient,cyoucsuspectcthatcthatchechascabdominalcbleeding.
cYoucarecsurprisedcthatchiscbloodcpressureciscwithincthecnormalcrange.cYoucwouldcexpectctoc
findcthatchisc_____________cisc_____________,callowingchimctocmaintainchiscbloodcpress
ure.
heartcrate;cincreased
heartcrate;cdecreased
respiratorycrate;cincreased
respiratc-cCORRECTccANSWER-heartcrate;cincreased
Explanation
Incthisccase,cthecheartcrateciscmostclikelycelevatedcascaccompensationctocmaintaincthecbloodc
pressure,cascMAPc-
cCVPc=cQcxcSVR,candcQc=cHRcxcSVc(MAPc=cmeancarterialcpressure,cCVPc=ccentralcvenousc
pressure,cQc=cCardiaccoutput,cSVRc=csystemiccvascularcresistance,cHRc=cheartcrate,candcS
Vc=cstrokecvolume).cNotecthatcthecpatientcmaycbecbreathingcrapidlycduectocpain,cbutcthiscwo
uldcnotcservectocmaintainchiscbloodcpressure.
Ac49-year-
oldcwomancwascrescuedcfromcachousecfire.cThecfirefighterscreportcthatcshecwascrescuedcfro
mcacsmoke-
filledcroom.cYoucknowcthatcoxygenciscconsumedcandccarboncdioxidecproducedcduringccomb
ustion.cWhenclookingcatcthecpatient'scbloodcwork,cwhatcwouldcyoucexpectctocfind?c(selectcall
ccorrectcanswers)
highcpCO2,chighcserumcHCO3-clevels
highcpCO2,clowcserumcHCO3-clevels
highcpCO2,chighcserumcH+clevels
highcpCO2,clowcserumcH+clevelsc-cCORRECTccANSWER-highcpCO2,chighcserumcHCO3-
clevels
highcpCO2,chighcserumcH+clevels
Explanation
ForcancacidosisccausedcbychighclevelscofcCO2cincthecblood,chemoglobincactscascbuffercbycbi
ndingcprotonsc(H+).cConsequently,cwhencH+cremainsctrappedcincthecredcbloodccellcboundct
ochemoglobin,cHCO3-
ciscreleasedcintocthecbloodstream.cTherefore,cincancinstancecwherecacpatientchascrespirator
ycacidosisc(acidosisccausedcbychighclevelscofcCO2),cyoucwouldcexpectctocseechighclevelscofc
CO2candchighclevelscofcHCO3-
,.cWhilecbufferingcmitigatescthecimpactcofcthecrespiratorycacidosis,cthecconcentrationcofcprot
onscdoescincreasecasccarboniccacidcformscfromctheccombinationcofcCO2candcwater.
Ac66-year-
oldcfemalecarrivescincthecemergencycdepartmentccomplainingcofcheadache,closscofcappetit
e,candcfatigue.cBasedconcbloodwork,cyoucfindcthatcshechascancanion-
gapcmetaboliccacidosis.cWhichcofcthecstatementscbelowcbestcdescribescthecprocessescincth
eckidneycthatcwillceliminatecthecmetaboliccacidscthatchavecbuiltcupcinchercblood?
Anionscarecfilteredcout,cprotonscarecsecreted,candcbicarbonateciscreabsorbedcintocthecblood
stream.
Cationscarecfilteredcout,cprotonscarecsecreted,candcbicarbonatecisc-cCORRECTccANSWER-
Anionscarecfilteredcout,cprotonscarecsecreted,candcbicarbonateciscreabsorbedcintocthecblood
stream.
Explanation
Ancanion-
gapcmetaboliccacidosiscisccausedcbycthecproductioncofcacidscthatcdissociatecintocprotonscan
dcanionscthatcarecnotcHCO3-corcCl-
.cThesecanionscmustcbecfilteredcintocurinecincorderctocbecexcretedcfromcthecbody.cThecproton
scbeingcproducedcmustcalsocbecsecretedcfromctheccellscliningcthecrenalctubule,candcforceachc
protoncsecretedcbycthecrenalctubuleccells,cacmoleculecofcHCO3-
ciscabsorbedcintocthecbloodstreamcduectocthecmechanism cofccarboniccanhydrase.
Ac66-year-
oldcmancvisitscyoucincthecoutpatientcrenalcclinic.cHechascsignificantcrenalcdysfunctioncandchi
scurinecoutputchascsignificantlycdiminishedcovercthecpastcseveralcdays.cHecsayscthatcheccon
tinuesctocconsumechiscnormalcdietcandcdrinkcwatercatchiscnormalcrate.cHecreportscnocothercl
ossescofcwater,csuchcascvomiting,cdiarrhea,corcexcessivecsweating.cWhatcwouldcyoucexpec
tctochavechappenedcwithcregardsctochiscweight?
increased
decreased
stayedcthecsame
notcenoughcinformationc-cCORRECTccANSWER-increased
Explanation
Incacsteadycstatecsituation,cinputc=coutput.cIfcsomethingcchangesctoceithercofcthesecfactors,ct
hencthecsystemcwillcnoclongercbecincsteadycstate.cIfcthecoutputcofcacsubstancecdecreasescwit
houtcanycchangecincitscinput,cthiscwillcresultcincancincreasecincthecamountcofcthecsubstance.cI
ncthisccase,cthecpatient'scfluidcoutputchascdecreased,csocthecamountcofcfluidcinchiscbodycwillci
ncrease,ccausingchiscweightctocrise.
Ac67-year-
oldcmancarrivescincthecemergencycdepartmentccomplainingcofcfatigue,cconfusion,cheadach
e,candclosscofcappetite.cWhencyouctakechiscmedicalchistory,checrevealscthatchechascadvance
, dcrenalcdiseasecandcrecentlycmissedcacdialysiscappointment.cYoucordercacbasiccmetaboliccp
anelcandcancarterialcbloodcgas.cThesectestscrevealcthecfollowingcpertinentcvalues:
pHc=c7.22
PCO2c=c23cmEq/L
PO2c=c98cmEq/L
HCO3-c=c10cmEq/L
Na+c=c140cmEq/L
K+c=c5.0cmEq/L
Cl-c=c110cmEq/L
Thecpatient'scanioncgapcisc_________c-cCORRECTccANSWER-
25corc25cmEq/Lcorctwentycfivecorctwenty-fivecorctwentycfivecmEq/L
Explanation
Thectraditionalcanioncgapcisccalculatedcbycusingcthecfollowingcequation:cAGc=c([Na+]c+c[K+])
c-c([HCO3-]c+c[Cl-]).cThiscpatient'scanioncgapciscthereforec(140c+c5)c-
c(110c+c10)c=c25cmEq/L.cAcnormalcrangecofcthecanioncgapciscbetweenc12candc16cmEq/Lc(alth
oughclabscmaycdiffercslightlyconcnormalcrangecdependingconcthecmeanscofcmeasurement),c
socthiscpatientchascancelevatedcanioncgap.
Ac72-year-
oldcmanciscsittingccomfortablycinchiscchaircreceivingcoxygencviacnasalccannulac(acdevicectocd
elivercsupplementalcoxygencviacthecnose)catc2cL/min.cHecisconcacnormalcdietcandciscincnocdist
ress.cWhatcdocyoucexpectchiscmajorcmetaboliccwastecproductsctocbecifchiscbodyciscprimarilyc
metabolizingccarbohydrates?
lacticcacid
ketocacids
SO4,cPO4
CO2c-cCORRECTccANSWER-CO2
Explanation
AerobiccmetabolismcofccarbohydratescproducescCO2.cAtcrest,cmostcindividualscrelyconcacmi
xcofcfuelcsourcescbutcproducecapproximatelyc200cml/mincofccarboncdioxidecfromcaerobiccme
tabolismcofccarbohydrate.cProteincmetabolismcproducescPO4candcSO4cwhilecfatcmetabolis
mcproducescketocacidscandcanaerobiccglucosecmetabolismcproducesclacticcacid.
Note:cthereciscacbaselineclevelcofcmetabolismcofcfatscandcproteinsc(especiallycincbetweencm
eals).
Acballooncwithcacsmallcradiuscwouldcseemctochaveclessccollapsingcforcecvs.cacballooncwithcac
largercradiusc(morecinflated).cHowciscthiscconsistentcwithcLaplace'scLaw,cgivencthatcyouclear
nedcincthecvideocthatcbubblescatcsmallercradiichavecgreatercpressurecthanconescatclargercrad
ii?
Tensioncandcradiuscchangecatcthecsamecratecforcacballoon,csocthatcpressurecinsidecthecballo
oncremainscconstantcovercacrangecofcradii.
Tensioncforcthecdifferentcsizecballoonsciscnotcconstant.
