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progressively from 10 to 18 cm H 20 w ith w orsening of hypo xem ia an d h ype rca pn ea. A t this stag e a P E w as clinicallysu sp ec te d a nd a V /P sc an o bta in ed . T he s tu dy w as p erfo rm edw i t h k r y p to n - 8l m 8 1 m} Ã § 4or the ventilationand technetium9 9m @ m T c)ma c r oa g g re g a te da l bu mi n M A A ) f o r t h e p e rf usio n, a nd s ho we d c la ssic al V /P m ism atc he d lo ba r d efe cts tosu gg est P E as w ell as rev erse V /P m ism atch F ig . 2). T herewas a signi ficantreductionofperfusion in the rightupperand

m id dle lo bes an d p ossib ly a m ild red uctio n o f p erfu sio n inthe left upper lobe,w hilerelativelyincreasedventilation wasp re se n t i n t he se p o rt io n s o ft he l un g . A n a d di ti on a l r em a rk a bl efin ding w as rela tiv e hy perpe rfu sion an d no ven tilatio n inatelectaticbilaterallower lobes.

A 4 m o o ld b la ck g irl w as in itia lly trea ted a t th e ag e o f

5 w k fo r p re su me d p ne um oc oc ca l m en in gitis. S he w as re adm itte d w ith r es pir ato ry d is tr es s, r eq ui ri ng i nt ub ati on a nd a ssisted ve ntilatio n. S he w as tho ug ht to h av e an asp iratio np ne um on ia th at re sp on de d to a ntib io tic th era py . A lth ou ghe xtu ba tio n w as p ossib le a fte r 1 0 d ay s, th e p atie nt re qu ire ds u p pl em e n ta l o x y g en . C l in i ca l a s se s sm e n t s u g ge s te d a n a n o xi ce n c ep h a lo p a th y , an d c o mp u t ed t o mo g ra p h y CT ) s h o w e d ac al ci fi ca ti on a t t he b a se o ft he b ra in a s w e ll a s c er eb ra l a tr op h y.R ep ea te d e piso de s o f re sp ira to ry d istre ss o cc urre d th at required increasingoxygentherapy.Ch estradiographsrevealed

m i gr at or y a te le ct as is a n d i nf il tr at es . I nt ub a ti on w a s r eq u ir edto facilitatereexpansionofthe lung.Althoughthe patientwasplaced on P E E P sustained at 10 cm H 2O , there w as noim pro vem ent. C om pu ted to mog rap hy o f th e ch est sh ow edb ila te ra l lo w er lo be a te le cta sis F ig . 1 ). P E EP w a s in cr ea se d

R e c e iv e d N o v . 1 4 , 1 9 8 8 ;r e vi si o n a c c e pt ed F e b . 1 , 1 9 8 9 .Forreprintscontact:ChunK.Kim,MD,AndreMeyerDept.

o f P h ys ic s/ N uc le ar M e d ic in e , B o x 1 14 1 , M o u n t S in a i M e d ic alC e nte r, O n e G u sta ve L . L ev y P la ce , N e w Y o rk , N Y 1 00 29 .

FIGUREC h e st C T s h ow s b il at er al l o w e r l o be a te le ct as is .

T h e J o ur na l o f N u d ea r M e d ic in e268 KimandHeym an

Ventila tion/Perfusion M ismatch Caused

by Positive Pressure Ventila tory Support

C hun K . K im and Sydney H eym an

D e part me n t o fRad io logy D iv is ion o fN ucl ear M e d ic ine Ch il dr en ‘sosp it al o f Ph il ade lph ia

Universi ty ofPennsylvania Philadelphia Pennsylvania

I n a p a ti en t w i th l o ba r a te le ct as is w h o w a s o n p o si ti ve p re ss u re v e nt il at or y s u p po rt ,v e nt il at io n a nd p e rf u si on i m a ge s s h ow e d a b se n t v e nt il at io n a n d n o rm a l p e rf us io n r ev e rs em ism atc h) in th e re gio n o f th e a te le cta sis a nd n orm al v en tila tio n a nd d ec re as ed p erfu sio n  t ru e m i sm a tc h) n o t c au se d b y p ul m on ar y e m bo li sm i n a n ot he r l un g z on e. W e r ep o rt t hi s c as et o e m ph as iz e t ha t t he l un g s ca n f in di ng s i n p at ie nt s o n p o si ti ve p re ss ur e v en ti la to ry S U pp O rtb e c ar ef ul ly i n te rp re te d f o r t h e d ia g no s is o f p u lm o n a ry e m b o li .

J NuciMed30:1268—1270989

ulm onary em bolism PE ) is often difficult to diag

nose because the sym ptom s and signs can be nonspec ific o r s ub tle . L un g v en tila tio n/p erfu sio n V /P ) s cmtig rap hy is th e p rin cip al n on in vasive im ag in g m od alityfo r its d ia gn osis. W e rep ort a c ase d em on stratin g b othclassical V /P m ism atch false positive for PE in thisc as e) a nd r ev er se V /P m i sm a tc h a bs en t v en ti la ti on a ndn or m al p er fu si on , t he re fo re n eg at iv e f or P E ) i n a p at ie nto n p os it iv e e nd -e xp ir at or y p re ss ur e P E EP ) m e ch an ic alv e nt il at or y s up p or t.

C A SE R E PO R T

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  i@

LPOQ

A

F IGURE 2R ight posterior oblique A ) and le ftposterior oblique B ) V /P im agesd em on stra te sig nific an t re du ctio n o fperfusionntherightupperandmidd I e l o b e s w i t h n o r ma l v e n ti l at io n , a ndre lativ e h ype rp erfu sio n in b ilaterall ow e r l o be s w i th n o v e nt il at io n .

The patient s respiratorystatus improveddramaticallyfollo w in g d is co nti nu ati on o f P E EP a nd v ig or ou s c he st p hy sic altherapy.

D I S C U S S I O N

T he re gio na l d is trib uti on o f p ulm o na ry p erfu si on inn orm al persons is know n to be un even in the up rightp ositio n p rim arily b ecau se o f g rav ity 1 -3 ). A lv eo larp ressu re e xceed s p ulm on ary arteria l an d v en ou s p ressure in the uppe rm ost part ofthe upright lung, resultingin the co llapse of the capillaries. T here is b lood flowonly at the peaks of the pulsatile pressure w av e in thisz on e 4 †”6 ).A lv eo la r p re ss ure o f n or ma lly v en tila te d  therefore inflated) upper and m iddle lobes w as inc re as ed i at ro ge ni ca ll y b y p os it iv e p re ss ur e v en ti la to rys up po rt, a nd th e b lo od fl ow to th is p ortio n w as re du ce d.O n the other hand atelectatic lo w er lobes w ere notin fla te d in s pi te o f P EE P, s o th at th e b lo od v es se ls w erer el at iv e ly p ro t ec te d f ro m t he p re s su re e ff ec t a n d r el at iv ehyperp erfusion w as seen. T he resu lt of th is ph enom e

non w as a right to left shunt of blood flow throug h then on ve ntil ate d lo we r lo be s o fth e lu ng s. T his fin di ng w asp rev io us ly w ell d em on strated in clo sed -ch est p ig s 7 )a nd in d og s 8 ). O th er i nv es tig ato rs re po rte d th at P EE Ps ig n if ic an tly r ed u ce d in tr av as cu la r p u lm o na ry fl uid v ol

u mes alo ng w ith card iac o utp ut 9 ,1 0) an d p ulm on arya rte ria l fl ow 1 1). A ll th es e fa ct ors c ou ld c on trib ute tof ur th er d ec re as e o f P aO 2 .

In a previous case report dem onstratin g a sim ilarfin din g, th e a uth ors em ph asized th e n eed fo r a k no wle dg e o fth e p atie nt s c lin ic al s ta tu s a nd o fa tim ely c he stra diograph to com pare w ith V /P scan 12). W ithout a

c om p le te u nd er st an di ng o ft he e ff ec t o fP E EP , h ow e ve r,it w ould be difficult to accurately interpret this kind of

V /P sca n ev en w ith a tim ely ch est ra dio gra ph . O ur

s tu dy d em o ns tr at in g m a rk ed r ed uc ti on o fp er fu si on a ndn orm al v en tilatio n in th e rig ht u pp er an d m id dle lo bescould have been interpreted as having high probabilityfor PE , since large th rom boem boli m ay cause inco mp le te o cc lu si on o fl ar ge v es se ls .

W e w ish n ot o nly to d escrib e a relativ e h yp erp erfu

  269o l u me 3 0 â € ¢u mb e r 7 â € ¢u l y 19 8 9

RPc@ RPOV

LPOV

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4:154—167.5. M aloney JE , B erge l D H, G lazier JB , et al. T ransm is

s io n o f p u ls at il e b lo od p re ss ur e a nd f lo w t hr ou gh t heis ola te dlu ng . C irc Re s 1 96 8; 2 3:1 1â €” 24 .

6 . S ee ke r- W al ke r R H . T h e r es pi ra to ry s ys te m . I n: H a rb ert J , d a R o ch a A F G, e ds . T ex tb oo k o fn uc le ar m edi cine Volume II: c l inical applicat ions Philadelphia:Lea Febiger 1984:311.

7 . E njeti 5, O N eill JT , T erry P B, e t al. E ffects o f p ositiv ee nd e xp ir at or y p re ss ur e o n s hu nt f lo w i n a te le ct as is .R es pir Ph ys io l 1 98 2; 4 8: 24 3â €” 25 4

8. S anche z de L eon R , O rchard C , Sykes K , et al. P ositivee nd -e xp ira to ry p re ss ure m ay d ec re as e a rte ria l o xy ge nt en s io n i n t he p re se n ce o fa c o ll ap s ed l un g r eg io n . C r itC are M ed 1 98 5; 1 3:3 92 †”3 94 .

9 . S lu tsk y R A . R ed uctio n in p ulm on ary b lo od v olu meduring positive end-expiratory pressure. J Surg R es1983;35:181—187.

1 0. M a rin i J J, C ulv er B H , B utle r J . M e ch an ic al e ffe ct o fl un g d is te n ti o n w i th p o si ti ve p re s su re o n c ar di ac f u nct io n. A m R e v R e sp ir D i s 1 98 1; 1 24 :3 8 2â €” 38 6.

1 1. S charf SM , B row n R , Saunders N , et al. H em odyn am ic e ffe cts o f p os it iv e-p re ss ure in fla tio n. J A pp lPhys iol 98 ;49:12 4— 131

12. G oodw in C A, E pstein D H. L ung perfusion scanning.

T h e c a se o f â €• re v e rs emismatch―.C lin N uc iM e d 1 98 4;9:519—522.

sion in nonventilated ate lectatic lobes reverse V /P

m ism atch) but also to em phasize that a reduction o fp erfusion in the artificially inflated p art of the lungs

  true V /P m ism atch) m ay occur. T his finding should

not be interpreted as a high probability for P E . V /Pl u ng s ci nt ig ra p hy m a y b e e ff ec ti v el y u t il iz ed t o e v al ua tean u nex plain ed d ro p o fP aO 2 in th e p atien t o n m ech anical ventilation.

R E F E R E N C E S

1 . W e st J B. P ulm on ary fu nc tio n stu die s w ith ra dio ac tiv eg as es .A n nu R e v M e d 1 96 7; 1 8 :4 59 .

2. A nthonise n N R, M iic-E m ili J. D istribution of pulm o na ry p erfu sio n in e re ct m an . J Ap pi P hy sio l 1 96 6;21:760.

3. K aneko K , M ilic-E m ili J, D olovich M B , et al. R egional distribution of ventilation and perfusion as afunction of body position. J Appl Physiol 1966;21:767—777.

4. M aloney JE , B ergel D H , G alzie r JB , et al. E ffect of

p u ls a ti le p u lm o n a ry a rt er y p re ss u re o n d is tr ib u ti on o fbloo d flow in isolated lung. R esp ir P hysiol 19 68;

 27 KimandHeymanTheJo urnalof NuclearMed icine