Download ESSAY: PRESSURE AND SHEAR RELIEF AND THE

ESSAY:PRESSUREANDSHEARRELIEFANDTHEJARIKFLUIDCUSHION
Thepurposeofthisessayistoexplainthetheorybehindpressureandshearrelief
andhowtheJARIKFluidCushionisdesignedtoneutralizetheseforces,tohelp
preventpressuresores.
First,whatisapressuresore?Quitesimplyitisanopenwoundcausedbydying,
necrotictissuethathasbeenstarvedofitsnaturalbloodsupply.Thesizeofthe
visiblewoundissmallcomparedtotheunderlyingproblem,asthetissuediesfrom
theinsideout.
Theimplicationsofapressuresoreforawheelchairusercanbemonthsofbed‐rest,
waitingforthewoundtoheal.Duringthistime,theperson’sactivelifeliterally
comestoahalt.Orworse,thewoundcanbecomeinfected,leadingtoasystemic
infectionthatoftencausesdeath.Infact,pressuresoresarethenumberonekillerof
peoplewithspinalcordinjuriesindevelopingcountries.
Thetwobiggestcausesofpressuresoresarepressureandshear.
PRESSURE
Let’sstartwithpressure.Todemonstratetheeffectsofpressure,withtwofingers,
pressagainstthetopofyourotherhand.Liftyourfingers,andnoticetheblanching
ofthehand.Thispressureisenoughtosloworstopbloodflow.Ifyouweretohold
yourfingersthereforafewhours,thetissuewouldstartdyingfromthelossof
bloodflow.
Thinkofthecapillariesthatsupplythisbloodflowasaseriesoftinyhosescarrying
blood.Whenyousteponawaterhose,youslowdownorstoptheflowofwater.
Theproblemisthatcapillarybloodpressureisonlyabout35‐40mmofmercury,so
it’svery,veryeasytoslowdowntheflowofblood.
Nowthatyouunderstandpressure,imaginethebuttocksastheyrestonacushion.
Worseyet,imagineaparaplegicorquadriplegicbuttocks,wherethenormalmuscles
haveatrophiedfromlackofuse,andtheseatbonesorischialsprotrudeastheydo
onaskeletonwithnotissue.Inordertorelievepressure,thecushionhastobeable
toconformtoaveryboneybuttocks.Ifitdoesn’t,theseatboneswilltaketwoto
fivetimesasmuchpressureastheareasaroundit,andtheprobabilityofapressure
soreismagnified.Stateddifferently,theboneyseatbonesofaparaplegicor
quadriplegicwill,onaverage,beexposedto70‐150mgofpressureona
conventionalfoamcushion–severaltimesthepressureofbloodflow!
Now,lookatthedesignoftheJARIKFluidCushion.Amoldedfoambaseiscutaway
attheareaoftheseatbonesandtailbone.Overthatarea,weplaceourfluidpad.
Duringsitting,theviscousfluidflowsawayfromtheseatbonesandtailbone,to
completelyconformandtoevenlydistributepressureovertheentireseatingarea.
Asaresultofuniformpressuredistribution,peakpressuresareoftencutinhalf
comparedtoconventionalcushions.Lesspressuremeanslesschanceofapressure
sore.
You’veprobablynoticedthewrinklesinthefluidpadandwonderedwhetherthey
couldcauseasore.TheanswerisNO,becausethethicknessofthewrinkleis
absorbedintothefluid.Pressyourhandonthewrinkleandyoucannotfeelit.
Sowhyaretherewrinkles?Iftherewerenotwrinkles,thinkofwhatwouldhappen
whenaboneyprominencesitsonthecushion.Thefluidwouldwanttoconform,but
thesurfacematerialwouldactasahammock,preventingconformation,asthe
boneyprominancescouldnotfreelyenterthefluid.Asaresult,thebonestakemost
ofthesittingweight.Butwiththewrinkles,thesurfacematerialcollapses,allowing
trueimmersionintothefluid.Thebonesnowtakealotlesspressure.
SHEAR
Thewrinklesalsorelieveshearforces.Whatisshear?Mostpeoplethinkofshearas
friction,butthat’sonlypartofthestory.Sheariscausedbymovementduring
sitting.Forexample:whenshiftingpositions,ortransferringintothewheelchair‐
ortheback‐and‐forthrockingoftheseatbonesasapersonpropelshischair.
Tobetterunderstandshear,tryasimpledemonstration.Takeyourknuckleand
pressitintoaconventionalfoamcushion.Feelthepressure?Now,gentlyrockyour
knuckleforwardandholdIthere.Rockitbackandholditagain.Doyoufeelthe
movementofyourtissueagainstthebone?Thatisshear.Itispressureplus
movementplusfriction,causingthetissuetomoveagainstthebone.Thinkofshear
asdoublingtheeffectsofpressure.
Now,let’sgobacktoourhoseanalogy.Ifpressureislikesteppingonthehose,then
shearislikebendingorkinkingthehose–whichisexactlywhatishappeningatthe
capillarylevel.Andweallknowthatitismucheasiertostopwaterorbloodflowing
inthehosebybendingit–whichiswhatsheardoes.
Andfinally,let’sgobacktothewrinklesinthefluidpad.Asthesittershifts
positions,thesurfacewrinklesofthepadmovewithhim,therebytransferringthe
shearforcestothefluid.Withoutthewrinkles,shearforceswouldnotberelieved.
Andnoticealsothatthesamewrinklesaredesignedintotheoutercover,sothatit
alsoconformstotheseatbonesandmovestorelieveshearforces.
WRITTENSTUDIES
Ofcourse,theoryisonething.Practiceisanother.WhichiswhyIencourageyouto
accesstwostudiesonourwebsite.Thefirst,coordinatedbytheIndianSpinal
InjuriesCentreinDelhiIndia,testedtheJARIKFluidCushionon81patients,mostly
spinalinjured.ItfoundastrongpreferencefortheJARIKFluidCushionon11of12
cushionattributes,includingpressurerelief.Thesecondstudy,conductedatDenver
GeneralHospitalintheUnitedStates,showedsittingpressuresonaveryboney
paraplegictobesignificantlylowerontheJARIKFluidCushionascomparedtoa
highquality,dualdensitymemoryfoamcushion.Furthermore,JARIKpressures
werecomparabletothetwoleadingpressure‐reliefcushionsintheworld‐theJAY
(whichIalsodesigned)andtheROHO.
SITTINGSTABILITYANDBALANCE
InowwanttoquicklyreviewtheotherbenefitsoftheJARIKFluidCushion,starting
withsittingstabilityandbalance.
Asapartoftheirdisability,peopleoftenlosefunctionormusclecontrolindifferent
ofpartsoftheirbodies.Thismakesitharderforthemtomaintaintheirbalanceand
tositupright.Itmakesithardertopropelthewheelchair.Itoftenmakesitharder
totakeasipfromaglassofwater.
Thesittingbaseisthestartingpointandthefulcrumpointfromwhichallstability
andbalanceisderived.Instabilitythereisaccentuatedineverypartofthebody.To
betterpromotestability,balanceandfunction,theJARIKFluidCushionisdesigned
fortheutmoststability.Acontouredfoambaseliterallycradlesandholdsthehips
tothebackofthewheelchair.Theviscousfluidinthepadmovesonlywhenyou
shiftpositions.Otherwise,itmaintainsyourshape,toholdyoucomfortablyand
firmlyinplace.Theresultisanoticeableimprovementinstability,balanceand
function.
POSTURE
Sittingpostureisalsoacriticalelementincushiondesign.Assumingyou’veread
thefirstessayonPostureandtheContouredFoamCushion,Iwon’trepeatallthe
commonpostureproblemsseenamongwheelchairusers.ButIwillpointoutthe
following:
‐ Slouchingposturesarediscouragedbythecontouredfoambaseandthenon‐
skidbottom,whichhelppreventthehipsfromslidingforward.
‐ Pelvicobliquitiesandscoliosisarediscouragedbyadual‐chamberfluidpad
thatdoesnotallowfluidshiftingfromonesidetotheother.
‐ Properlegpositioningisencouragedbyfirmsupportunderthelegsanda
centralabductor(amildlegseparatorbuiltintothecushionbase).Plus,the
cushioncomeswithoptionallegpositioningwedgesthatcanbeusedto
separateorunitethelegs,asdesired.Formostpeople,simplydroppingthe
footrestsprovidesenoughlegsupporttoavoidusingthelegaccessories,
whichnecessarilyinterferewithtransfers.
‐ TheFluidCushioncomesinavarietyofwidthsandlengthstoallowproper
fitting.Inaddition,thebasecaneasilybeshortenedornarrowedtocustom
sizesbyusingaserratedknife.
EASYMAINTENANCE
MylastsubjectispropermaintenanceoftheJARIKFluidCushion.Forcomplete
fittingandmaintenanceinstructions,pleasedownloadourUserManualfromour
website.
Allcomponentsofthecushionarewashable.Removetheoutercovertowashand
dry.Thefluidpadandbasecovercanbescrubbedwithsoapandwaterandrinsed
withawetcloth.Theinsidebaseisprotectedbyasecond,urineproofpouchand
shouldneverrequiremaintenance.
Themostimportantpartofthemaintenance,however,ischeckingthefluidlevel–
topreventbottomingout.Thisisveryimportant.Todothis,sitonthecushion
withoutthecoverforoneminute.Liftyourselfoffthecushionandpushwithone
fingeratthelowestpartofthefluid.Formostpeople,therewillbe½”or1cmof
fluidormorebeforeyoucanfeeltheunderlyingfoambase.Ifthereislessthanthis,
thepadisindangerof“bottoming‐out.”Tocorrect,simplydetachthefluidpadand
re‐attachitclosertothecenterofthebase.Thiswillconcentratemorefluidunder
theareathatwasbottoming‐out.Nowsitonthecushionagainandrecheckthefluid
levelasyoudidbefore.Ifitisstill“bottoming‐out”thendonotusethecushionand
seeifyoucantryanarrowersize.NOTE:Bottomingoutwillnotoccuronheavy
patients,butonthethinnestpatientswhotendtodisplacethefluidtothesides.
Also,donotincreasethefluidlevelunlessyouneedto,oryouwillactuallyincrease
sittingpressures.
Ihopethisessayhashelpedyoubetterunderstandpressurerelief,sittingstability
andpostureandhowawell‐designedcushioncanhelpimprovesittingsafety.I
encourageyoutocontactmeat:[email protected]
questionsorcomments.
RickJay
FounderJARIKMedical