Factors associated with inspiratory muscle weakness in patients with HIV-1

The

Brazilian

Journal

of

INFECTIOUS

DISEASES

w w w . e l s e v i e r . c o m / l o c a t e / b j i d

Original

article

Factors

associated

with

inspiratory

muscle

weakness

in

patients

with

HIV-1

Fabiana

S.

Jerônimo

_,

_Giovanni

_N.

_Alves

_,

_Gerson

_Cipriano

_Jr.

_,

_Paulo

_J.C.

_Vieira

_,

Adriana

M.

Güntzel

Chiappa

_,

_Gaspar

_R.

_Chiappa

a_{BomPastorHealthCenterUnit,Ararangua,Brazil}

b_{ExercisePathophysiologyResearchLaboratoryandCardiologyDivision,HospitaldeClinicasdePortoAlegre,PortoAlegre,Brazil} c_{PhysicalTherapyDepartment,UniversityofBrasilia,Brasilia,Brazil}

d_{PhysicalTherapyService,IntensiveCareUnit,HospitaldeClinicasdePortoAlegre,PortoAlegre,Brazil} e_{SerraGauchaCollege,CaxiasdoSul,Brazil}

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Articlehistory:

Received29May2014 Accepted27July2014

Availableonline16September2014

Keywords:

Diaphragmmuscle Inflammatoryresponse Lungfunction

Exercisetolerance,highlyactive antiretroviraltherapy

Inspiratorymuscle

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Background:theimpactofhumanimmunodeficiencyvirustype1(HIV-1)onlungfunction iswellknownandassociatedwithareductioninpulmonaryventilation.Moreover,the useofhighlyactiveantiretroviraltherapyhasbeenassociatedwithmitochondrial dysfunc-tionanddecreasedmusclestrength.However,thereisscarceinformationaboutthefactors associatedwithinspiratorymuscleweaknessinthesepatients.

Objective:thepurposeofthepresentstudywastoinvestigatethefactorsassociatedwith inspiratorymuscleweaknessinpatientswithHIV-1.

Methods:two-hundredfiftysevenpatientswithHIV-1werescreenedandcategorizedinto two groups: (1) IMW+ (n=142) and (2) IMW− (n=115). Lung function (FEV1, FVC and FEV1/FVC),maximuminspiratorypressure,distanceonthesix-minutewalktestandCD4 cellcountwereassessed.

Results:the meandurationofHIVinfectionwassimilarinthetwogroups.The follow-ingvariablesweresignificantlydifferentbetweengroups:meandurationofhighlyactive antiretroviraltherapy(81±12inIMW+versus38±13monthsinIMW−;p=0.01),andCD4 cellcount(327±88inIMW+versus637±97cells/mm3_{inIMW−;p=0.02).IMW+presented} reducedlungfunction(FEV1,FVC,FEV1/FVC).

Conclusion: patientswithIMW+hadlowerdistanceonthesix-minutewalktestin com-parisontotheIMW−group.Thedurationofhighlyactiveantiretroviraltherapy,distance traveledonthe6MWTandCD4countweredeterminantsofIMWinpatientswithHIV.

©2015PublishedbyElsevierEditoraLtda.

∗ _{Correspondingauthorat:ExercisePathophysiologyResearchLaboratoryandCardiologyDivision,HospitaldeClinicasdePortoAlegre,} RuaRamiroBarcelos2350,CEP90035-007PortoAlegre,RS,Brazil.

E-mailaddress:gaspar.chiappa@gmail.com(G.R.Chiappa). http://dx.doi.org/10.1016/j.bjid.2014.07.003

Introduction

Theuse ofhighly-active antiretroviraltherapy(HAART)has improvedthe prognosisofpatients infectedbythe human immunodeficiency virustype1(HIV-1).1–4 _{Aprevious study}

hasdemonstratedthat suchindividuals exhibitprogressive skeletalmuscledysfunctionaffectingexerciseperformance.5

However,other studiessuggestthatmitochondrial function maybeadverselyaffectedbythebiochemicalchangesthat occur in HIV-1 infection6 _{or bythe use of HAART.}7 _These

factorshelpexplaintheinspiratorymuscleweakness(IMW) foundinpatientswithHIV-1,asevidencedbyreduced maxi-muminspiratorypressure(MIP<70%ofpredictedvalue).8–11

Themechanismsresponsibleforlimitedexercisecapacity includeabnormalitiesinthecentralhemodynamics(sluggish bloodflowandfasteroxygenextractioninperipheraltissues) aswellasautonomic,vascularandrespiratoryresponsesto exercise.11 _{However,studies haveshown thateven}

asymp-tomaticpatientswithHIV-1exhibitgeneralizedwastingand significant loss of functional capacity, as demonstrated by a shorter distance traveled on the six-minute walk test (6MWT).5,12

Other factorslinked tophysicalde-conditioning include the chronicnature ofthe disease,anemia, diabetes, infec-tionandperipheraloxidativedysfunctionrelatedtotheuse ofnucleosidereversetranscriptaseinhibitors.8,10 _These

fac-torsresult inexaggerated ventilatory responseto exercise, withreducedlungcompliance10_{andprogressiverecruitment}

ofinspiratoryandexpiratorymuscles,resultingininspiratory musclefatigueduringexercise.Theinspiratorymusclesmay alsobe adverselyaffected bychanges inand resistance to contractileproperties13,14_{duetochronicoxidativestressand}

infection.15

According to Schulz et al.16 _{impaired respiratory}

mus-clefunctionmaycontributetotheunexplainedshortnessof breathfoundinpatientswithHIV.However,nopreviousstudy hasaddressedthedeterminantsofIMWinsuchindividuals. Thus,theaimofthepresentstudywastoinvestigatepossible factorsassociatedwithIMWinpatientswithHIV.

Material

and

methods

Subjects

Acomparativestudy wascarriedout involving257patients withHIV-1receivingHAARTandphysicallyinactiveforatleast sixmonths.Patientswererecruitedfromanationalreference center for acquired immunodeficiency syndrome (AIDS) in Brazil.TheinclusioncriteriawereadiagnosisofHIVinfection, clinical stability(without hemodynamicinstability or pres-enceofopportunisticdisease)andnochangeinantiretroviral regimeninthepreviousthreemonths.Theexclusioncriteria wereunstableangina,myocardialinfarction,chroniclung dis-ease,orcardiacsurgeryinthepreviousthreemonths;chronic metabolic or orthopediccondition treated with steroidsor hormones;undergoing chemotherapyforcancer;history of lung disease (forcedvitalcapacity [FVC] <80% ofpredicted value and/or forced expiratory volume in 1s [FEV1] <70%

ofpredictedvalue);historyofexercise-inducedasthma;and smokinghabit.ThisstudyreceivedapprovalfromtheHuman ResearchEthicsCommitteeoftheHospitalClinicasdePorto Alegre(Brazil)underprocessnumber240.254andallsubjects signedastatementofinformedconsent.

Protocol

Themedicalhistoryofeligiblepatientswasrecordedandthe subjectswere submittedtoaninitialphysicalexamination, resting electrocardiogram,the determinationof inspiratory musclefunctionandthe6MWT.Thepatientsalsoprovided blood samples for fasting glucose, total-, LDL- and HDL-cholesterol,CD4andCD8counts.Theparticipantshadtwo came to the laboratory on day 1 and 48h thereafter. The patients had to undergo a protocol for maximal inspira-torymusclestrength(MIP) evaluationandwere categorized into twogroups: (1) withmaximal inspiratory muscle dys-functiondenominatedinspiratorymuscleweaknesspositive (IMW+, MIP<70% ofpredicted value);11,16,17_{and (2)without}

inspiratorymuscleweakness,i.e.,withMIPpreserved denom-inatedIMW−(MIP>70%ofpredictedvalue).The6MWTwas performedthreetimesoneachevaluationdayforthe determi-nationofthemaximumdistancetraveledandreproducibility.

Lungfunction

LungfunctionassessmentwasperformedusingtheCPF Sys-tem (Medical Graphics-MGC, St. Paul, MN), with air flow measuredusingacalibratedPitottube(PreVent,Pneumotach). FVC(inliters),FEV1(inliters),FEV1/FVCandinspiratory

capac-ity(inliters)wererecordedasrecommendedbytheAmerican ThoracicSociety.18_{Theresultswereexpressedasabsoluteand}

percentage ofpredicted value. Inspiratorymuscle function testing was performedusing apressure transducersystem (POWERbreatheK5,NorthfieldRoad,Southam,Warwickshire, UK).Maximumstaticinspiratorypressurewasdeterminedin deepinspirationstartingfromresidualvolume.Thehighest pressureofsixmeasurementswasusedforanalysis.

Six-MinuteWalkTest

The6MWTwasperformedinanindoorcorridormeasuring 25minlength,followingrecommendationsbyGuyattetal.19

Theparticipantswereinstructedtowalkfromoneendtothe otherofthecorridorasmanytimesaspossibleinsixminutes. Attheendofthetest,thephysicaltherapistmeasuredthetotal distancetraveled.Reproducibilitywasdeterminedinasample ofthe257patientsandthedifferenceindistancebetweenthe twotestswaslessthan5%.Themaximumdistancetraveled wasusedtoassesssubmaximalfunctionalcapacity.Patients self-gradedtheirdegreeofdyspneaduringthetestusingthe Borgscale.17

Statisticalanalysis

ThedatawereanalyzedwiththeStatisticalPackageforthe SocialSciences (version19.0,SPSS, Chicago,IL).Descriptive dataarepresentedasmean±standarddeviation.Dataofthe two groupswere comparedbyone-way repeated-measures

Table1–Characteristicsofparticipants.

Characteristics Allpatients(n=257) IMW+(n=142) IMW−(n=115) p-Value

Demographic/anthropometric Age(years) 45±11 46.5±11 49.2±10 0.24 Sex(male/female) 53/18 35/10 18/8 0.77 BMI(kg/m2_{) 23±3 23±4 25±4 0.42} FastingGlucose(mg/dL) 99±22 91±25 86±16 0.12 Totalcholesterol(mg/dL) 180±40 176±42 189±37 0.23 HDL-cholesterol(mg/dL) 43±13 46±14 39±9 0.11 LDL-cholesterol(mg/dL) 110±45 105±34 118±37 0.29 Hemodynamics MBP(mmHg) 90±16 98±12 90±18 0.35 HR(beatsmin−1) 77±7 88±8 76±10 0.74

DurationofHIV(months) 122±18 104±12 111±21 0.34

DurationofHAART(months) 56±27 81±12a _{38±13 0.01} Virology

CD4count(cells/mm3_{) 536±72 327±88}a _{637±97 0.02}

CD8count(cells/mm3_{) 1098±444 1086±480 1124±358 0.25}

CD4/CD8ratio 0.48±0.18 0.31±0.04a _{0.56±0.09 0.01}

CD4nadir(cells/mm3₎

Median(interquartilerange) 245(140–368) 90(19–144)a _{270(159–354) 0.03}

Viralload(log) 2.1(1.7–3.5) 2.5(1.8–3.6) 2.1(1.5–3.4) 0.55

Viralload(≤50cells/mm3_{;%) 71 67}b _{92 0.04}

Lungfunction

FEV1(L) 3.02±0.45 2.66±0.46a 2.88±0.67 0.02

FEV1(%ofpredicted) 95±10 85±6a 93±8 0.03

FVC(%ofpredicted) 101±12 92±13a _{102±9 0.03}

FEV1/FVC 94±5 92±8 91±9 0.67

Inspiratorymusclefunction

MIP(cmH2O) 80±12 45±12a 90±17 0.01

MIP(%predicted) 77±11 46±14 89±12 0.01

Exercise

6MWD(m) 445±65 265±38a _{452±67 0.01}

6MWD(%ofpredicted) 95±22 45±18a _{91±12 0.01}

Continuousvariablesexpressedasmean±standarddeviation;categoricalvariablesexpressedusingchi-squareorFisher’sexacttest. BMI,bodymassindex;HDL,high-densitylipoprotein;LDL,low-densitylipoprotein;MBP,meanbloodpressure;HR,heartrate;FEV1,forced

expiratoryvolumein1stmin;FVC,forcedvitalcapacity;FEV1/FVC,forcedexpiratoryvolumein1stmintoforcedvitalcapacityratio;MIP,

maximalinspiratorypressure;6MWD,distancetraveledonsix-minutewalktest;HAART,highlyactiveantiretroviraltherapy.

a _{Significantdifferenceincomparisontoothertwogroups.} b _{SignificantdifferenceincomparisontoIMW−(p<0.05).} c _{Chi-squaretest.}

analysisofvariance.Posthocanalysiswasconductedusing eitherTukey’stestorFisher’sexacttestforcategorical vari-ables. Pearson’s correlation coefficients (r) were calculated to determine factors associated with MIP. Stepwise multi-pleregressionanalysiswasperformedwithMIP,durationof HAART,distancetraveledonthe6MWTandCD4cellcount.

Results

Two hundred sixty-nine patients with HIV were evaluated betweenMay2010andNovember2011.Twelvepatientshave notmettheeligibilitycriteriaandwereexcluded.Therefore, 257patientswerescreenedforthestudy,amongwhom142 werecategorizedasIMW+(MIP<70%ofpredictedvalue)and 115wereIMW−(MIP>70%ofpredictedvalue)(Fig.1).

Table1displaysthecharacteristics ofthe sample.Mean agewas45±11years.Cholesterolvalueswerenotelevated.

Assessed for eligibility (n=269)

Randomized (n=257)

Excluded (n=12)

♦ Not meeting inclusion criteria (n=10) ♦ Declined to participate (n=2)

Allocated (n=142) Allocated (n=115)

Completed both treatment periods of study n=257

IMW+ IMW–

CD4 count (cells/mm3₎ MIP (cm H 2 O) 0 0 20 40 60 80 100 120 140 160 180 200 400 600 800 1000 r =0.761 P<0.001 1200 1400 1600

Fig.2–Scattergramoftheassociationbetweenmaximum inspiratorypressure(MIP)andCD4count(cells/mm3)forall subjects.Opencirclesrepresentpatientswithout

inspiratorymuscleweakness.Filledcirclesrepresent patientswithinspiratorymuscleweakness.r=Pearson’s correlationcoefficient.

Noabnormalitieswerefoundregardinghemodynamics.The IMW+grouphadhigherfastingglucose.Timeelapsedsince the diagnosis of HIV infection was not significantly differ-entbetweengroups.IMW+patientshadbeenunderHAART for a longer period oftime, had a significantly lower CD4 count,butnodifferenceintheCD8count,resultinginalower CD4/CD8ratio.Thelungfunctionwasmorecompromisedin IMW+ comparedto IMW− (FEV1: 85±6 vs. 93±8%of

pre-dicted;p=0.03;FVC:92±13vs.102±9%ofpredicted;p=0.03), butwithinnormalitywithoutdifferencesbetweenFEV1/FVC.

TheIMW+grouphadlowerMIP(45±12vs.90±17cmH2O; p=0.01)andtraveledashorterdistanceonthe6MWT(265±38 vs.452±67m;p=0.01)incomparisontotheIMW−group.

The therapeutic regimens consisted of two nucleoside analog reverse transcriptase inhibitors plus one protease inhibitor,withorwithoutlow-doseritonavir(25%),ora non-nucleoside reverse transcriptase inhibitor (75%). The most commonHAARTcombinationintheIMW+groupwas zidovu-dine,lamivudineandefavirenz,whichdifferedfromthatof patientsintheIMW−group.MIPwascloselyassociatedwith theCD4cellcountinallpatients(r=0.761;p<0.001;Fig.2).In thestepwisemultipleregressionanalysis(Table2),the CD4

Table2–Resultsofstepwisemultipleregression analysisofmaximuminspiratorypressure.

Dependentvariable Independentvariable ˇ ra

6MWD HAARTduration −0.62 0.68

MIP 0.66

CD4count 0.78

MIP,maximuminspiratorypressure;HAARTduration,durationof highlyactiveantiretroviraltherapy;6MWD,distanceonsix-minute walktest;ˇ,standardizedpartialregressioncoefficient;r,multiple correlationcoefficient.

a _p<0.001.

countwasasignificantdeterminantof6MWT.Thetotal vari-anceexplainedbythismodelwas56%(p<0.001).

Table 3 displays the CD4 cell counts in the IMW+ and IMW− groups. Eighty-eight patients in the IMW+ group had <200cells/mm3 _{and 54 had >200cells/mm}3_{. In the}

IMW− group, 49 patients had <200cells/mm3 _{and 66 had}

>200cells/mm3_{. Interestingly,the combination ofIMW and}

CD4count<200cells/mm3_{alteredpulmonaryfunction,}

inspi-ratory musclestrengthanddistancetraveledonthe6MWT in comparison to the absence of IMW and CD4 count >200cells/mm3_.

Discussion

Thepresent study isthefirst todescribethedeterminants ofinspiratorymuscleweakness (IMW)inpatientswithHIV. Inspiratorymuscle dysfunctionisrelatedto theseverityof HIVinfection.16,20 _{Thepresentdatarevealthat 55%of}

HIV-infected patients presented IMW in a sample of clinically stable patients. This finding is compatible with previous studies.16,21_{However,incontrasttothepresentstudy,these}

studieshadsmallersamplesizes.

IMWwasstrikinginthepatientsanalyzed.Thisresponse isdependentonhemodynamicandclinicalvariablesaswell aschangesindiaphragmmorphology.11_{Moreover,thelonger}

duration ofHAARTinIMW+patients, associatedwithboth thedistancetraveledonthe6MWTandCD4cellcount,might have caused highertoxicity inthese patients comparedto IMW−patients.However,theeffectsofHIVinfectionon respi-ratorymusclesfunctionhavenotbeenwellcharacterizedin theliterature.Ourstudyhasshownthatinspiratorymuscle dysfunctioncanleadtoareductioninlungfunction,evenin clinicallystablepatients(CD4>200).22_{Previousstudieshave}

describedthatsuchareductionisassociatedwithlowerCD4 count,23,24 _{whichexplainsthe increase inthefrequencyof}

respiratory symptoms combined with dyspnea in patients withHIV.Moreover,impairedlungfunctionisconsideredto beanimportantpredictorofincreasedrespiratorymortality andcloselyassociatedwithadversecardiovascularevents.25

HIV infection is associated with progressive depletion of CD4T lymphocytes and defective HIV-specific T-cell responses.26_{Persistentimmuneactivationplaysacentralrole}

indrivingCD4T-celldepletionandprogressiontoAIDS.27,28

Theauthorsofthepresentstudybelievethatsevereinfection and reactiveoxygen speciesare requiredforthe molecular cascades that eventually produce myofiber atrophy of the diaphragm,whichmayfavorIMWinpatientswithHIV.

Inthepresentstudy,MIPwascloselycorrelatedwiththe distance traveledon the 6MWT(r=0.61;p<0.001)and CD4 cell count(r=0.73;p<0.001), independently ofIMW, which suggests an importantcombinationwith theinflammatory response.Moreover,associationswerefoundbetweenMIPand durationofHAART(r=−0.62;p<0.001)aswellasbetweenthe distancetraveledonthe6MWTandfastingglucose(r=−0.65,

p=0.02). Studies have suggested that inadequate glucose controlmay belinkedtoinflammationand decreasedlung function inindividualswith diabetes.29 _{Theauthors ofthe}

present study agreewiththe hypothesis that IMWor dys-functionoccursinthecourseofHIVinfection.Moreover,the

Table3–Comparativeassessmentofpulmonaryfunction,inspiratorymusclestrengthanddistancewalkedindifferent groupsaccordingtoCD4count.

IMW+ IMW− CD4<200(n=88) CD4>200(n=54) CD4<200(n=49) CD4>200(n=66) FEV1(L) 1.88±0.66a,b 2.58±0.45 2.88±0.49c 3.01±0.56 FEV1(%ofpredicted) 83±5a 90±8 95±12 96±9 FVC(%ofpredicted) 95±12 95±7 98±8 102±12 FEV1/FVC 88±6a,b 94±5 96±5c 94±8 MIP(cmH2O) 45±12a,b 68±15 80±13c 97±20

MIP(%ofpredicted) 46±14a,b _{69±12 82±18 98±19}

6MWD(m) 265±38a,b _{301±44 349±49}c _452±67

6MWD(%predicted) 45±18a,b _{52±14 81±27 95±29}

Viralload(%)

≤50 41a _{69 60 83}

Dataexpressedasmean±standarddeviation.

IM,inspiratorymuscleweakness;FEV1,forcedexpiratoryvolumein1stmin;FVC,forcedvitalcapacity;FEV1/FVC,forcedexpiratoryvolumein

1stmintoforcedvitalcapacityratio;MIP,maximalinspiratorypressure;6MWD,distancetraveledonsix-minutewalktest.

a _{Significantdifferenceinoverallcomparison(p<0.001).}

b _{ComparisonofCD4below200cells/mm}3_{inIMW+andIMW−(p<0.01).} c _{ComparisonbetweenCD4aboveversusbelow200cells/mm}3_{inIMW−(p<0.01).}

authorsbelievethatareductioninCD4cellcountresultsin IMWandexerciseintolerance.

Anumberofmechanismshavebeensuggestedtoexplain thereductionininspiratorymusclestrengthinpatientswith HIV,suchasreducedcross-sectionalareaofalltypesof mus-clefiberinthediaphragmandmusclesoftheribcage,typeI fiberatrophy,changesinthetypeItotypeIIbfiber ratioin thediaphragm,30–32_{areducednumberofactin-myosin}

cross-bridgesin the diaphragm,33 _{and an abnormalintracellular}

Ca2+_profile.30,31_{Thesameappliesforpotentialmechanisms}

leading to inspiratory muscle dysfunction, impaired car-diac function,9 _{a reduction in oxidative enzymes}15,34 _and

impairedmitochondrialreplicationthroughtheinhibitionof mitochondrial DNA gyrase byzidovudine,16,35 _{which could}

furthercompromisetheinspiratorymuscles.Inthepresent study, the prevalence of IMW coincided with the use of zidovudine.Evidencesuggeststhatzidovudineandtenofovir resultinsignificant myopathy.21,35,36 _{Although thepatients}

in the present study exhibited IMW, the authors believe thatsystemicbiochemical abnormalitiesmay occur, result-ingininspiratory muscledysfunctioninpatients withHIV. Studies have reported a lack of l-carnitine, which lim-its the intra-mitochondrial transport of long-chain fatty acids, leading to a change in energy metabolism6 _and

impairment of diaphragm contractions. Studies have also suggested that an impaired oxidation reduction mecha-nism in muscle may contribute to oxidative stress in the diaphragm.13,14,37–39

Shortnessofbreathisoftenassociatedwithexercise intol-erance and it has been suggested that IMW may be an importantcontributingcausetothesensationofdyspnea,16

aswellastoashorterthedistancetraveledonthe6MWTin patientswithHIV.Several studieshavereporteda relation-shipbetweenanemiaandfatigueinsuchpatients.40,41 _The

distancetraveledonthe6MWTinthepresentstudyprovides furtherevidencethatinfectionscouldresultindecreased exer-cisecapacity.

Surprisingly,aCD4count<200cell/mm3 _affected

inspira-torymusclestrengthandthedistancetraveledonthe6MWT, whichsupportsourhypothesisthatinfectionisanimportant factortoexerciseintoleranceinpatientswithHIV.

The present study has a limitation that should be addressed.Nocardiopulmonaryexercisetestwasperformed, whichwouldhaveconfirmedexerciseintolerance.However, asubmaximalexercisetext(6MWT)wasused.5_Thedistance

traveledonthe6MWThasdemonstratedimportant associa-tionswiththelossofmusclemass,generalizedwastingand weakerhandgripstrength.12,42 _{Theseassociationshave}

pre-viouslybeenevaluatedinpatientswithchronicheartfailure andIMW.11,19_{Inourstudy,IMWwasassessedbynon-invasive}

techniqueas describedinother publishedstudies.Perhaps weshouldhaveusedmoreinvasivemeasuressuchastension timediaphragmaticindexortwitchPdi.

The findings of the present study demonstrate that patientswithHIVinfectionhavesignificantexercise limita-tionsresultingfromIMW.Theunderlyingpathomechanisms, responsestotreatment,andthe potentialrole ofIMWasa prognostic markerofrespiratory muscle dysfunction merit furtherinvestigation.

Conflicts

of

interest

Theauthordeclaresnoconflictsofinterest.

Acknowledgments

Financial support was partially provided by National ResearchCouncil(CNPq,478063/2010-5)andCoordenac¸ãode Aperfeic¸oamentodePessoaldeNívelSuperior(CAPES,PNPD 2818/2011).

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