7一打OUG〃7昔A」V∂P尺OG月旦∫∫

4βjthanvenouspressure（〜8cmofH20）regardlessof
One s posture．In hydrocephalus，theintracranialCSFpressureis higherthan normaldue eitherto
increased resistance to CSFnow or to hyperpro−
duction ofCSF．The causes can be congenita）oracquired（e．gリtumOrS）．Hydrocephalusis treated

withone−WayShuntstodrainCSFfromthecerebral
Ventricleintotheabdominalcavltyandtherebyre−
StOreintracranialpressure to normal．This CSF
Shuntworkswellwhenthepatientliesdown，but
invitesanexcessnowwhenthepatientstands．Theexcessflowis causedbyapressure−headbetween
the cerebralventricle and the abdominalcavlty．
Thisleadstoalowintracranialpressure，Whichmay
PrOduce headaches or cause development ofsub−duralhematoma（l）．

In ordertolimit the excessnow，devices calledanti−Siphon valves have been used clinically（2）．

One such device consists of a diaphragm valve
Whichoccludestheshuntpasswithdeformationof
thediaphragmbyapressuredifEbrencebetweenthe
ANewlyDesignedFlow−RegulatingDevice
inShuntTherapyofHydrocephalus
・＼一山小イIルり一甘止、イ山‖りい 仙／一．＼−り／りJ．l・J山人 川・ 〃い♪（pdrJ∽e〃J∫q／βわβ〃gg〃ピer′〃g（了〃d＊〃e〟r（フ∫〟rgビワ，∫cん00Jqr〟ピdfcJ〃e，g加†創伯J■／一／l・ r項l・‥＼再伸扉／J 肌し／叫黒／JAbstract：A new now−regulatlng device fbr shuntlngln

hydrocephaluswasdesignedtolimitanexcessnowbva

pressure−headbetweenthecerebralventricleandtheab・
dominalcavityinastandingpositjon．Thedevjcehastwo
diaphragmvalvesconnectedtoeachotherbvtwoiines：

Oneisashuntlnglinetotransfercerebrospinalnuidand
theotherisacontrolline坑11ed withacontroinuidwitha
higherdensltythancerebrosplnalnuid．Theperformanceof the modeldevice witlla naturalrubber sheet diaY

Phragmwastestedinamocksyste叫uSlngglycerolfor
the controlfluid and waterforthe transfernuidinvitro，Resultsshowthatdevicedecreasestheexcessnowwhen
the pressure−head between two valves exceeds35cm．

Kcy Words：CSF Shullt−Flow−1imiting valve−
Hvdrocephalus−Control−fluid−Diaphragm．

Due toits delicate structure，the brainis sur−roundedinsideandoutbycirculatingcerebrospinal
fluid（CSF）withintheintracranialcavity．Inabrain

WithnormalCSFcirculation，theintracranialpresL

OutSideandinsideofthepass（1，3）．Whenitisim−
planted，however，theantisiphonva）vedoesnotal，

WayS function we11，becauseits diaphragmcanbe
deformedbythesurroundingtissue（4）．

InordertolmprOVetheperformanceofthevaive，
aflow−1imitlngValvewasconceiVedofthatcouidb己OPerated directly by the pressure−head．Thisidea】edtothedeveiopmentofafiow−regula貢ngdevice
Withtwodiaphragmva】vesandjtsperformancewas
testedinvitr（†，MATERIALS ANDMETHODS
Principleofthe壬l（珊・イegu皇a也唱dev孟ce

TheworkingprinCipleof琉ow regiila扇ngdeviceis
Shownin Fig，i．The device consists oftwo dia−phragm valves connected to each other byもWO
lines：a Shuntingline that transiもrs CSF（transferfluid），andacontro‖inethatisⅢ1edwithanu主dof
higherdensitythanthetrarlSfbrf）uid（controlfluid）．
One ofthediaphi▲agm valvesisimplantedintoor
a功acenttothecerebralventricleandtheotherinto

theabdominalcavlty．Theinletandoutletlinesare
COnneCted to the shuntlngline through each dia−phragmvalveandopenintothecerebralventricle
andtheabdominalcavity，reSPeCtively．InFig．1，amocksystemfbrtheperfbrmancetestisshownem−
PloylngtWOOVerflow−tankswithdepthshlandh2，

Whichrepresentpressuresinthecerebralventricle

Sureisnormal（〜15cmofH20），andslightlyhigher and the abdominalcavlty，reSPeCtively．Two dia−

Phragmvalvesarelocatedaqjacenttothe respec−tive overflow−tanks so that the pressure−head be−
Address correspondence and reprlnt requeStS tO Shigehiro tween the two valvesis equalto that ofthe two
Hashimoto，atDepartmentofBioengineering，SchoolofMedi−tanks．FigurelAillustratesthecasewithnopres−
Cine，KitasatoUnjversity，15−1，Kitasatol−Chome，Sagamihara−
Sure−head．In this case，the transfernuidis trans−
Shi．228Kanagawa，Japan．
Received：DecembeI 1987；reVisedFebruary1989．

Ar】ザOrg（Ⅰ那，γoJ．ノブ，〃0．5，ノ財9r〃OUG」打r∫AJV上）P尺OG尺g∫∫4β4density．Theextentofflowdecreaseis controlled
bythevolumeordensityofcontrolfluid，Orbythe
COmplianceofthediaphragm．FigurelCillustrates
the case with the counter−preSSure−head ofH．In

this case，the transftrfluid would be transferred
fromoutlettoinletaccordingtotheleveldifference
Of［Hr（hlr h2）】・Inthisdevice，thecounterflow

islimited by the diaphragm defbrmationin thelowervalve，aSinthecaseofFig．1B．
Performancetestinvitro

Theperfbrmanceofthemanufacturedmodelde−Vice（Fig．2）was testedin the mock system；tWO

diaphragmvalvesconsistofapolymethylmethacry−
1atehouslngandanaturalrubbersheetdiaphragm（0．21mmthick）andareconnectedbytwopolyeth−
ylenetubelines（1．5mminside diameter，3．O mmOutSide diameter，100cmlength）．A valve−irisistbrmedin the center part ofhouslng Of transftr
flow−pathside（Fig．2B）．Thediameteroftheopen−
1ng pOrt Oftheirisis4．O mm．The test was per−tbrmedinthissystemwithglycerol（1．26g／cm3den−Sityat20OC）forthecontrolfluidandwithwaterfor
FIG．1．Principleoff10W−regUlatingdevice・

ferred frominlet to outlet according to thelevel

difftrence of（hl−h2）・FigurelBillustrates theCaSeWiththepressure−headofH．Inthiscase，theexcessmotivefbrcegeneratesandthetransftrfluid
WOuldbetransftrredfrominlettooutletaccording
totheleveldifferenceof［（hl−h2）＋〟］．Inthis

device，theexcessflowbytheexcessmotivefbrceWiththepressure−headofHislimitedbytheirisof
thelowerdiaphragmvalve．Thisperfbrmanceisre−

alizedbythediaphragmdeformation（inthelowerValve）owing tothehigherpressureinthecontrol
fluid．Thehigherpressureisgeneratedbythehigher

the transferfluid at20OC．Tolink two overflow−tankswiththeshuntsystemeveninthecaseofnopressure−head between the two diaphragm valves（withoutfunctionofflow−regulatingdevice），50−Cm

lengthpolyethylene tubelineswereconnectedfbr
inlet and outletflow paths．Thus，flow rate withfunction of theflow−regulating device was com−pared with that without function of theflow−
regulatingdeviceinthewayofcontrollingthelevel
Ofdifferencebetweentwodiaphragmvalves．
RESULTS

Figure3showsflow rates as afunction ofthepressure−head betweeninlet and outlet when thehouslng

FIG．2．Manufacturedmodeldeviceoff10W−regUlatingdevice，A：Externalappearanceoftheentiredevice．B：Cross−SeCtional
Viewofdiaphragmvalve．
ArげOr卵那，V∂J．Jj，〃∂．5，J9β9

n70UG〟7昔A〃βP月OG尺g∫∫

4β5

1亡h flow−／∈ql＿11a亡1ng devIce′

山ヒhout flow−req。Iatingdevicel

U一∈＼一∈︑心﹈吾H−妄じ己′l／／／／／／／／ー100−50．」with no pressure−headhO叫／′叫霊じ−壱Iu与∈1空′もwlthoutflow＿′／／re9ulatingdevice／U召＼T∈l∈U︹OL︶H／／500100

Initialpressuredifference hlrh2，⊂mwlth flow−r甲ulatingdevice

FIG．4．Themaximumf10Wrateintherangeofpressure−head＜100cmasafunctionofinitialpressuredifferencebetween
inIetand outlet．

bralventricleandanabdominalcavitylnaStanding
POSition（2）．Theyarecalledantisiphondevicesand
may be construCtedin severalways，With a dia−

Phragmvalveoperatedbythepressure difference
between atmosphere andintrashunt path（1，3），ahl−h2三O

Pressure head H，QTL
FIG．3．FLowrateasafunctionofpressure−headwithoutini−
tialpressuredifference．Thearrowshowsthemaximumf10W「ate（Withf10W−regutatingdevice）．Thisvaluecorrespondsto
thedatum point（Withthearrowin Fig，4）ofwhichtheab−
SCissaequalszeroin Fig，4，ballvalvewithaspnngofwhichdeformationcon−
troIstheintrashuntpressure，aSeriesofvalvesof
VariableopenlngPreSSure，Oraballvalveoperated
bygravitationalforce．Whenanyofthesedevices
areimplanted，however，theydonotalwaysfunc−
tionwell．Thisisbecausethediaphragmisnotde−

formed by the atmospheric pressure butratheris
PreSSed by the surrounding tissue，because thepressure difference between the upper and lowerinitialpressuredifferencebetweenthemiszero（hlSides ofthe valve does not correlate with that be−−h2＝0）．Inthiscase，theidealflowratesarezero
tweentheinletandoutletofshunt，andbecausethe
tobalancethepressuresofinletandoutlet，because
PreSSure−head does notrenect onthe direction of
hlequalsh2．Whentheflow−regulatlngdevicedid
gravitationalforce．
notfunction，however，theexcessflowsaccording
Theflow−regulating device describedin thetothepressure−headoccurredasindicatedbythe
PreSentStudyisoperateddirectlybythepressure−brokenlinein Fig．3．The excessflow rates de−

CreaSedwiththeflow−regulatlngdeviceintherange
Ofpressure−head＞35cm，aSindicatedbythesolid
lineinFig．3．Thesimilarfunctionsweremeasured
forvariableinitialpressuredifferences：−−20cm＜hlL h2＜60cm．Themaximumnowrateforeach

initialpressure difference was determinedfrom
eachfunction curve andisindicatedby theopen
Circlesin Fig．4．Without function oftheflow−

regulatingdevice，themaximumflowrateswerethe
Values on the broken Line fbr the pressure−heads

head（betweentwodiaphragmvalves）amplinedby
thedensitydifference．ItsworkingprlnCIPleensures
thesameperfbrmanceinvivoasinvitro．Thus，thisStudy suggests that the flowAregulating device
WOuldlimit theexcessflowby thepressure−headbetween the cerebral ventricle and the abdominal
CaVltylnthestandingpositioninshunttherapleSOfhydrocephalus．
REFERENCES＜100cm．Theseexcessflowratesagaindecreased l．PortnoyHD，Schu）teRR，FoxJL，CroissantPD，TrippL．

tothesolidlinelevelandapproachedthosewithout
PreSSure−head（thedottedlineinFig．4）．
DISCUSSION

Some devices have been clinically applied toShunttherapleSOfhydrocephalusinordertolimit
anexcessflowbyapressure−headbetweenacere−Anti−Siphonandreversibleocclusionvalvesforshuntlngln
hydrocephalusandpreventingpost−Shuntsubduralhemato−mas，J〃g〟rO∫〟rg1973；う8：729−738．

2．MoriK，ed．CSFshunlsySlems．Tokyo：ExcerptaMedica．
1986．
3．GruberR，Jenny P，Herzog B．Experiences with the anti−
Siphon device（ASD）in shunt therapy ofpediatric hydro−
Cephalus．J〃g〟r（フ∫〟rg1984；61：156−162．

4．Portnoy HD．Shunt selection and operative technic．Mod7セcん〝fq〟g∫∫〟rg〃e〟rO∫〟rg1985；27：1−10．

Ar すOrg（】n∫，V（止JJ，〃0．J，J9β9