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81 0 THE JOURNAL O F BONE AND JO INT SURGERY

REDUCT ION OF PO ST -TRAUM AT IC SW ELL ING AND

COM PARTM ENT PRESSURE BY

IM PUL SE COM PRESSION O F TH E FOOT

A . M . N . GARDNER , R . H . FOX , C . LAWRENCE , T . D . BUNKER , R . S . M . L ING , A . G . M A cEACHERN

F rom Torbay H osp ita l, D evon , P rincess E liza be th O rth opa ed ic H osp ita l, E xeter and D epartm en t o f

M ath em atica l S ta tistic s, E xe ter U niversity

Fo llow in g th e d iscov ery of a power f u l venous pum p in th e f oo t tha t is a ctiva ted by w eigh t-b ear ing

independen tly o f m uscu lar action , a pneum atic im pu lse d ev ice w as dev elop ed to actua te th is pum p artific ia lly .

In a m u lticen tre in ternationa l tria l th e dev ice w a s show n to reduce post-traum atic and po stoperative sw ellin g ;

pain a lso w as a llev ia ted . Ev idence is a lso p resen ted tha t dange rously h ig h com partm en t p re ssu re s m ay be

reduced to accep tab le leve ls and fascio tom y avo id ed .

W e presen t an exp lanation of th e c lin ica l effec ts o f a c tiva tion of th e v enou s foo tpum p, based on recen t

im prov ed understand ing o f th e physio logy of th e m icro c ircu la tion . T he hyperaem ic respon se that fo llow s th e

lib eration o f endothe lia l-d eriv ed re lax ing fac tor (EDRF ) by sudden changes of p ressu re after w eigh t-b ea ring

or im pu lse com pression is particu lar ly im portan t.

F or over 100 y ea rs th e presen ce o f a v enou s pum p in th e

foo t has been pos tu la ted (L e D en tu 18 69) . W eigh t-

bear ing has b een thou gh t to em pty a subcu taneou s ven ous

p lexus in the so le in to th e d eep ve ins o f the fo o t. T h en ce ,

m uscu la r ac tion p um p s b lo od up in to th e sup erfic ia l ve ins

on the do rsum and from the re in to the lon g an d sh ort

sap henous ve ins . T he b loo d then en te rs the ca lf th ro ug h

the pe rfo ra ting ve ins (B ass i 19 67 ; P egum and F eg an

1967 a, b ; H ach 1985 ). D urin g an inv estiga tion in to th e

p hysio logy o fv en ous re tu rn , us ing th e dyn am ic tech n iqu e

of v id eo ph leb ography , th is co ncep t w as foun d to be

in co rrec t. V ideo p h!eb ography pe rfo rm ed on one of us

A . M . N . G ardne r, M Ch , FRCS , C on sultan t V ascu lar Su rgeon

R . H . Fox, FRCR , DM RD , C onsultant R adio lo gist

A . G . M acEache rn , FRC S, Consu ltant O rthopaedic S urg eon

To rbay H ospita l, Law es B rid ge, T orquay , South D evon TQ2 7AA ,

England.

C . L aw rence, B Sc(Hon), S tatistic ian

D epartm ent of M ath em atic al S tatistic s, U niv ersi ty of Exete r, S trea -

tham C ourt, R enn es D rive , Ex eter , D evon EX 4 4PU , England.

T . D . Bunke r, M Ch , FRCS E d, FRCS , C on sultan t O rth op aed ic

Surgeon

R . S . M . L ing , FRCS , C on sultant O rthopaedic Su rgeon

Pr incess E liz abe th O rthopaedic Ho spital, W on fo rd R oad , Ex ete r,

D evon EX2 4U E , England.

Co rre spondence should be sent to M r A . M . N . G a rdn er at the P riory ,

Ip plepen, South D evon TQ I2 5RT .

© l990 B rit ish E ditorial Soc iety ofBone and Join t S urgery

030l-6 2OX /90/5138 $2 .00

JBoneJoin tSurg[Br] 1 99 0; 7 2- B:8 10 -S .

(AM NG ), stan d ing u prigh t on one leg , c lea rly iden tif ied

the p resen ce o fa veno us pum p in th e n on-w eig h t-bear ing

foo t (F ig . 1 , G ardn e r and Fox 1983). Th is pum p consis ts

o f th e venae com itan te s o f th e late ral p lan ta r a rte ry ; it

w as una ffec ted b y to e and an k le m ovem en ts , bu t w as

im m ed ia te ly em p tied by w eig h t-bear ing . Em p ty ing d e-

pended prim arily o n flatten in g o fthe p !an tar a rch ; t ak ing

w e igh t on tran sve rs e ba rs u nde r the heel and the

m eta ta rs al h ead s e ffec tiv e ly em ptied the pum p (F ig . 2 ) ,

w he reas w e igh t-bea rin g on a tran sve rs e rid ge un de r th e

m id -fo o t m erely em p ties the v enou s foo t-pum p a t th e

p o in t o f co n tact.

I t seem s, th e re fo re , tha t m uscu la r con trac tion p lays

little o r no pa rt in th is actio n and tha t th e p um p is

em p tied by lo ng itu d ina l s tretch in g of the ve ins. Ind eed ,

th e p lan ta r m u sc les do n o t con trac t o n no rm al w eig h t-

bea rin g un til a fte r the venou s foo t-pum p has em p tied

(B asm a jian and B en tzon 1954 ; B asm a jian and S tecko

1963 ). F u rthe rm ore , the pum p is fu lly ope ra tiv e in

p arap leg ic s , in w hom stro ng D opp le r f low sig na ls a re

g en e ra ted in the pop litea l an d the fem oral ve ins by

w e ig h t-bea ring w ith the knees b raced (G ard ne r and Fox

1989).

T hese f ind in gs sugg ested the pos sib ility o f ar tific ia l

ac tiv a tion o f the v en ous fo o t-p um p in orde r to m a in ta in

a pu lsa tile v en ous b lo od flow in p atien ts af te r op era tion

o r in ju ry , th ereby reduc ing the r isk o f veno us th rom bosis .

T he d ev ice tha t w as d ev e loped in f late s rap id ly , un lik e

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F ig . lb F ig . lc

T he A -V Impulse pump , show ing th e com pre sso r and air rese rvo ir. w hich v en ts in term itten tly and rapid ly in to a pneum a tic pad applied

rig . around the foot. Th is flattens the arch and emp ties the venou s pum p.

POST-TRAUMATIC SW ELL ING AND COM PARTM ENT PRESSURE REDUCED BY IM PULSE COM PRESSION O F THE FOOT 81 1

VOL. 72 -B , N o. 5 , SEPTEMBER 1990

Figure la - Phlebogram o fth e non -w eight-b ea ring foot ofo ne o fth e auth ors (AMNG) wh ile stand ing on th e oth er leg . T he

radiog raph show s la rge foo t-p um p veins . To e and ank le m ovem ents d id not affe ct th em , but (F ig . lb) w eig ht-bea rin g

imm ediate ly em ptied them . F igu re lc is an an teropo ste rio r v iew o f th e foo t-p um p to show tha t it co ns ists of the v enae

com itante s of the lateral p lan tar ar tery (reproduced w ith perm issio n from the B ris to l M edico-Ch iru rgic al Jou rna l).

F ram es of a video ph lebog raphic record ing show ing tha t bea rin g

w eight on transv erse b locks unde r the ball o f the fo ot and the heel

e ffe ctiv ely em p ties the v enous foo t-p um p (by p erm iss ion , Jo hn L ibbey

and C o).

o the r p neum a tic bo o ts and leg g ing s ; it fla ttens the a rch

of th e fo o t and abru p tly em p ties the veno us foo t-pum p

thus im ita tin g the actio n ofw a lk in g (F ig . 3 , A -V Im pu lse

System , N ov am ed ix L td U K ). T he in fla tion p ad m ay be

in co rp o rated u nde r an im m ob ilisa tio n cast o r w ith in a

pu rp ose -m ade slipp er . T he venou s foo t-pum p, w hen

ac tiva ted e ithe r na tu rally o r b y the d ev ice, is pow erfu l

eno ugh to ov e rcom e a calfcu ff in f la ted to 100 mmH g and

can the refo re d isp lace a co lum n of b lood up to th e heart

in the e rec t pos tu re (G ardn er and Fox 1989).

A ltho ugh the A -V Im pu lse dev ice w as o rig ina lly

d ev e!op ed w ith the ob jec t o f p reven tin g v en ous th rom -

bosis - a p ossib ility cu rren tly u nde r in vestiga tion - it s

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F ig . 4 a F ig .4b

Tab le I. D eta ils o fth e 71 patients studied

81 2 A . M . N . GARDNER , R . H . FOX , C . LAW RENCE, T . D . BUNKER , R . S . M . L ING , A . G . M AcEACHERN

THE JOURNAL OF BONE AND JO IN T SURGERY

F ram es ofa vid eophlebographic re co rdin g

show ing the e ffe ctiv e em ptyin g o f the foo t

veins by the A -V Im pu lse d evice.

m os t o bv io us imm ed ia te effec t w as to red uce po st-

traum atic sw e lling and pa in ; th is is th e su b ject o f th is

paper .

PA T IENTS AND M ETHODS

The A -V Impulse pump . T he dev ice con sis ts o f an

e lectr ically d riven air com presso r and a ir re se rv o ir tha tven ts in te rm itten tly in to a sm all pn eum a tic p ad w hich is

shaped so as to fla tten the p lan ta r a rch on in f latio n . It is

sm a ll and po rtab le (F ig . 3 ), re lativ ely ch eap and sim p le

to app ly . It de live rs in term itten t pn eum a tic im pu lses to

im ita te the e ffect o f w e igh t-bea ring (F ig . 4 ) . T he pad is

used e ith er und er a cast o r in a specia l s lip pe r, b ein g

app lied ove r sto ck ine t o r p ad d ing . I t is pe rfo ra ted o n its

cu taneous aspect to p ro v ide v en tilatio n an d grad ua l

de fla tion . F o r those pa tien ts w ho a re ab le to w a lk the re

is a q u ick re lea se fac ility .

T h e cyc le o f ab ou t 2 0 sec allow s tim e fo r e ff ic ien t

p r im ing of the v en ous p um p. In f la tion occu rs rap id ly , in

le ss than 0 .4 sec , fo llow ed by slow er de fla tio n th rou ghthe pad pe rfo ra tion s, w h ich is com p leted b y cen tral

de fla tion o f the d ev ice . T he A -V pum p differs from o the r

pneum a tic com pression dev ices in tha t the com p ressio n

a rea is lim ited to the fo o t, w ith th e to es expo sed , and it

can be used con tin uou sly . Th e su dden in fla tion im pu lse s

rep rod uce the p hysio log ica l ra tch et- like flow pa tte rn o f

venou s re tu rn and gen era te tu rbu lence in v a lv e p ocke ts .

P atien ts . W e organ ised a m u !ticen tre tria l o f the e ffec ts

o f the p um p on sw e lling fo llow in g ope ratio ns o r traum a

to the leg w here p la ste r ca sts w ere no t u sed . T ab le I g ives

de ta ils o f th e 7 1 pa tien ts (con secu tive in each cen tre)

w ho pa rtic ip ated in the stud y . The re w ere m o re w om en

than m en and in alm ost 60% the righ t leg w as invo lved .

The age d is tr ibu tion w as that w hich m igh t b e expected

from a study ofth is k ind .

M easu rem en ts w ere m ade e ithe r a ro und th e foo t o r

abov e the an k le at iden tica l an d accu rate ly m arked sites

on the a ffec ted and on the con tra late ral u na ffected leg . A

spring -loaded tape m easu re w as u sed to en su re con stan t

tension . E ach obse rva tion w as the m ean of th ree

m easu rem en ts . U sin g th is p ro toco l, m easu rem en ts accu -

ra te to ± 1 m m cou ld be m ade . Fo llow ing base line

observa tion s, th e in ju red lim b w as trea ted w ith th e pum p

C ountry o fo rig in Spa in 35, N eth erland s 13 , UK 9, A us tralia 7 ,

B elg ium 4, Sweden 3

Se x M ale 31, fem ale 39, u nknow n 1

O pe ration or in ju ry H ip replacem ent

K ne e re pla ce me nt

H ip in ju ry

K nee in jury

K ne e a rth ro de sis

H ip o st eo to my

T ib ia l o ste oto my

T ib ia l fra ctu re

A nk le fra ctu re

C alc ane al fracture

30

5

7

7

2

1

1

7

8

3

L im b a ffe cted L eft 29 , rig ht 41 , unknown 1

Ageinyears l5 to25

26to35

36to45

46toSS

56to65

66to75

Ove r 7S

Unknown

5

7

0

3

12

13

11

20

T im e in days b efo re

f ir st m e a su re m en t 0 t o I

2 to3

4to9

Ove r 9

Unknown

17

19

14

15

6

fo r alte rna te 24 -h our p eriod s, an d at th e end of each

pe riod the m easu rem en ts w ere repea ted .

In a sepa ra te stu dy , 1 1 consecu tiv e pa tien ts w ith

seve re tib ia ! frac tu res w ere trea ted by im pu lse pum pin g .

C om partm en t p ressu re s w ere m easu red usin g a cann u la

(V enflon ) w ith u ltra -s low hepa rin ised in fusion , trans-

d ucer and reco rde r . F iv e case s w ere h igh v elo city in ju r ies

and six low ve loc ity .

RESULTS

Swel l ing . Fo r th e statis tica l ana lys is w e used on ly th ose

3 8 p atien ts w ho h ad com p lete se ts o f m easu rem en ts fo r

the base lin e an d four sub sequen t tim e po in ts , tha t is tw o

pe rio ds in w hich th e pum p w as o ff an d tw o w hen it w as

on . T he sam e se t o f v ariab le s w ere m easu red fo r each

pa tien t a t th e end o f each 24 -ho ur pe rio d . C on sequen tly

the da ta w as approp ria te fo r ana lysis b y a m u ltiva ria te

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Table II . M ean ch ange in girth in mm (sca led by un affected lim b

m easu rem en t and x 1000 (s.c .m .) ) d ur ing each of fou r 24 -hour

tim e p erio ds in th e a ffec ted and the una ffec ted lim b

Table I I I . Summary o f the F -te st statis tic al re su lts from the

mu ltivar iate analysis of v ariance

T im e per iod

1 st 2 nd 3 rd 4t h

(P um p on ) (Pum p off ) (P um p on) (Pump off)

A ffected lim b

M easurem ent I -41 (8) + 12 ( 4) - 26 (7 ) + 3 (5)

2 -49 (9) + 13 ( 9) - 30 (10) +7 (4)

3 -35 (7) +3 (3) -23 (5) -3(4 )

Unaffe cted lim b

M easurem ent 1 - 3 (3) + 10 ( 8) - 17 (1 1) - 1 ( 2)

2 + I (6) 0 (3) - 2 (3) - 2 (2)

3 -5(4) -3(3) -3(4) 0(2)

O n/O ffpump effect P erio d sequence effect

F -va lue (d .f .) F -va lue(d .f .)

Table IV . E ffe ct of im pu lse com pression on compar tm ent

p ressures in 1 1 pa tients w ith tib ial frac tures

# {1 49 }s ta ti st ic al ly s ig ni fi ca nt : p < 0. 00 1

Compa r tmen t

pressure

Numbe r of

pa t ie n ts

Pressure change

( mmHg )

Hou r s fo r

change

D ecreased from

>40 mmHg 4 42 to 10

42to36

45to3649to32

32

7

132

D ecreased 2 31 to27

38to27

10

3

In cre ased I lO tol4 1

U nch anged 4 9

27

28

6S

-

-

-

-

th is patien t had a tense haem arth ros is and an an ter ior

com par tm ent synd rom e wh ich required fasc io tom y after half

an hour

P S P S P S P

17

33

5

56

S

85

Pump -ON

11 8

33

63

82

48

23 22

Pum p-O FF Pum p -O N

Fig . 5

Pe rcentag es of pa tien ts w ith an increase (ha tch ed ) o r a dec rea se (b lack)

in sw ellin g (5 ) and p ain (P ) during fou r consecu tiv e 24 -hour per iod s in

wh ich the A -V Impulse pum p was eith er ON or O FF.

PO ST -TRAUMATIC SW ELL ING AND COM PARTMENT PRESSURE REDUCED BY IM PULSE COM PRESSION O F THE FOOT 81 3

VOL . 72-B , N o. 5 , SEPTEM BER 1990

A ffec ted lim b

M easu rem en t I 3 5 . 1 97 (l.37) 0 .40 (1 .3 7)

2 l8 .3 66 (l.3 6) 0 .471 (1 .37 )

3 23.0 22( l.27 ) 0 .513(1 .27 )

Unaffected L im bM easurem ent 1 2.2 45 (1 .38) 1 .8 12 (1 .3 8)

2 0.003(1.3 7) 0.3 65 (1 .37)

3 0.2 84 (1 .2 7) 0 .626 (1 .2 7)

rep ea ted m easu re s d esign . Im portan t in su ch a design

a re th e p ossib le ‘ca rry o ve r’ effec ts th a t w ere absen t from

th is stu dy . D ifferences in su bsequen t m easu rem en ts w ere

sca led by th e asso cia ted m easu rem en ts o f the u na ffected

lim b . Th is en ab led th e an aly sis to be carried ou t on the

basis tha t th e d ata from each pa tien t w as com m on to a

comm on sca le .

The p atte rn o f m ean g irth ch anges, ca !cu lated from

the th ree m easu rem en ts m ade ove r the fo u r tim e p eriod s,

a re g iv en in T ab le II . I t show s a sig n ifican t o n /o ff p um p

effect. T h is effec t w as in dependen t o f the fac to rs o f sex ,

la tera !ity , age , ty pe o f op era tion o r in ju ry , and the tim e

in te rv al be fo re sta rting ob se rv atio ns. T o take acco un t o f

the sequence o f tim e pe rio ds and th e na tu ra l recov e ry o f

the p a tien t the sets o f m easu rem en ts w ere u sed in a

m u !tiva r iate an aly sis o f v a riance .

The m ain re su lts ob ta ined from th is ana lysis a re

sum m arised in T ab le III w h ich show s tha t sw e lling

dec reased w ith pum pin g . Th e sta tis tic a lly s ign if ican t on /o ff pum p effect cann o t b e acco un ted fo r by na tu ral

recove ry o r ‘sequ en ce ’ effec t. T h is co nc lusion d id no t

alte r w hen a va riety o f ad d ition al ana lyses w ere pe r-

fo rm ed in w hich the o the r fac to rs w ere cons ide red as

54 co va ria te s . In pa rticu la r , the tim e in terva l b etw een

traum a or o pe ra tion and th e firs t ba se line obse rva tion

d id n o t change the s ign if ican ce o f the on /o ff pe riod .

Pa in . A n attem p t was m ade a lso to m easu re the e ffec t o f

im pu lse p um p ing on p ain . A stan da rd 1 0 cm an a logu e

scale w as em p loyed and w e a lso reco rded the am oun ts o f

an a lgesics requ ired , b u t the da ta w ere inadequ ate to g ive

sta tis tica l co n firm a tion . H ow eve r, it ha s been our

repea ted c lin ica l o bse rv atio n ove r seve ral y ea rs tha t

3 1 cessatio n o fpum pin g pro du ced recu rren t pa in w h ich w as

re lieved w hen the pum p w as re sta rted . F in d ing s in

re la tion to bo th p ain and sw e lling in a !! the 71 pa tien ts

are ch arted in F ig u re 5 .

Com partm en t p ressu re . T ab le IV show s th e com partm en t

Pump -OFF pres su res in 1 1 tib ia ! frac tu res trea ted w ith th e A -V

pum p. O ne pa tien t w ith a p lateau fractu re and a tense

h aem arth rosis o f the knee h ad an an ter io r tib ia ! com -

pa rtm en t p re ssu re o f 65 mm Hg . Pum p ing fo r ha lf an

hou r d id no t a lter th e p res su re an d fa sc io tom y w as

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81 4 A . M . N . GARDNER , R . H . FOX , C . LAWRENCE, T . D . BUNKER , R . S . M . L ING , A . G . M A cEACHERN

THE JOURNAL OF BONE AND JO IN T SURGERY

p erfo rm ed . In fo u r o th e r p atien ts p re ssu re s in itia lly in

excess o f4O mmH g dim in ished to b elow th is leve l w ith in

tw o to 32 hours o f trea tm en t. In norm a l p rac tice these

p atien ts w ou ld p robab ly have needed su rg ica l d ecom pres -

sio n . I t co u ld be argu ed tha t the se an te r io r com partm en t

p re ssu re s w ou ld have d ecreased w ithou t spec ific trea t-

m en t, b u t s tud y o f the tim e sca le s and the tenden cy fo r

th e p re ssu re to r ise w hen pum pin g w as stopp ed m ak e

th is in te rp re ta tion u n like ly .

DISCUSSION

It is n eces sary to con sid er th e physio logy o f th e

m icroc ircu la tion in o rd e r to u nde rstan d th e e ffect o n

tissue sw e lling o f im pu lse pum pin g or w a lk ing . U nfo rtu -

na te ly th e re are m any m isco ncep tion s in th is f ie ld , the

m o st im portan t be ing tha t f low th roug h the m ic ro circu -

la tion is con tro lled b y th e a rter iov en ous p re ssu re g rad ien t,

w ith cap illa rie s behav ing like rig id tubes.

Sw e lling . T he re is no rm a lly a co n tinu al circu la tion o f

flu id th rou gh th e in te rs titia l sp aces to nou rish tis sue ce llsand rem ove w as te p rod uc ts . Sw e lling is comm only caused

by the accum ula tion o f tis sue f lu id as th e re su lt o f an

im ba lance be tw een flu id ou tflow th rou gh the w alls o f th e

re la tive ly h igh -p res su re afferen t lim bs o f th e cap illa ry

loo ps an d osm otic reabso rp tio n in to the low -p res su re

e fferen t v en ous lim bs. Th is is S ta rlin g ’s c lass ica l co ncep t

o f th e m ic ro circ ula tio n.

O n ly a sm a ll p ro portion o f cap illa rie s a re n orm ally

op en a t o ne tim e . Th ey a re con tinua lly op en ing and

c losing to p rov ide an even d is tribu tion of tissue n ourish -

m en t. C ap illa ry b lo od flow is in term itten t and , a s bo th

F !o rey (1 925 ) and H e im berge r (192 6) show ed , it m ay be

reve rsed , and on ly one pa rt o f a cap illa ry m ay be op en .

The effe c t of exe rc ise an d im pu lse p um p ing in

redu cin g oedem a cou ld be ex p la ined if su dden rise s in

venou s p re ssu re cau sed a g rea ter p ropo rtio n o fthe veno us

lim bs o f the cap illa ry loop s to o pen , th us in c rea sing the

osm otic reabso rp tio n of in te rs titial f lu id . A lthou gh

vo lum e trica lly le ss im po rtan t, d ra in ag e of in te rs titia l

flu id b y lym pha tics is a lso like ly to be assis ted by

pump in g .

C om partm en t syn drom es. K now ledg e of m ic roc ircu la to ry

phy sio log y is a lso essen tia l in und erstand in g th e com -

pa rtm en t syn drom e in w hich a m oderate inc rea se o f

tissue p re ssu re , m u ch les s than the m ean a rter ia l p re ssu re ,

can cause ab rup t ces satio n o fm ic ro circu !ato ry b lood flow

and acu te tissue ischaem ia (A sh ton 1962) .

W hen the effective p erfu sion pressu re (p er fu sion

pressu re m in us tis sue p res su re) is p rog re ssiv ely reduced ,

cap illa r ies c lose w hile the re is s till a head of p re ssu re o f

abo u t 3 0 m mH g (c ritic a l clo sing pre ssu re - posi t ive

p ressu re in te rcep t) and th is o ccu rs u sua lly w h en tissu e

p ressu re rise s ab ove 40 m mH g. W ith cap illa ry c losu re a

v icio us c irc le beg in s, reabso rp tio n of tissue f lu id cease s,

f irs t p rod uc ing an ox ia an d then tissue dea th . The

p ersis tence o f a r ter ia l p u lsa tion is clin ica lly m islead in g .

It is ev iden t, the re fo re, tha t a low system ic b lo od

pres su re, eith e r from o !ig aem ic sh ock or from local

ar te ria l h ypo ten sion fo llow ing eleva tio n of th e lim b , w ill

encourage c ritic a l cap illa ry c losu re and com pound th e

effec t o f a rais ed com partm en t p re ssu re cau sed b y

b leed ing o r b y venou s con gestion . Ex terna l com pression

by pneum a tic sp lin ts , b an dages o r an ti-sh ock ga rm en ts

sim ila rly encourage cap illary c losu re (A sh ton 1962) .

Im pu lse o r phy sio lo g ical venou s pum p ac tion cou ld

reopen c ritic a lly clo sed cap illa rie s and redu ce tissu e

p re ssu re eith er b y causin g re flu x o f b lood in to th e v en ous

lim bs o f cap illary lo ops , en ab ling tissue f lu id to b e

reab so rbed by osm osis , o r by in c rea sing b loo d pe rfusio n

p re ssu re thu s causin g relaxa tion of the sm oo th m usc le o f

th e a rte r io la r re sis tance vesse ls .

I t is now estab lish ed tha t rap id p re ssu re changes

such as th ose p ro duced by w e igh t-b ea r ing o n the foo t, o r

by im pu lse pum ping , a re fo llow ed by inc rea sed b loo d

flow in to th e lim b due to w id esp read d im in ished vascu la r

re sis tance . Su ch hyp eraem ia la sts ab ou t 2 0 sec ; i n crease s

in pop !itea l a rte ry f low of 93% in norm a l sub jec ts and8 4% in pa tien ts w ith pe riphe ral v ascu lar d isea se h ave

b een reco rded (G ard ne r and Fox 1989). T hese in crease s

are to tally ou t o f p rop ortion to the sligh t d im inu tio n o f

flow reco rded d urin g the ac tua l com p ressio n .

H yp eraem ia a fte r im pu lse com p ressio n is p ro bab ly

m ed ia ted th ro ugh endo the !ia!-d er ived re lax ing fac to r

(EDRF ). EDRF is n itr ic ox id e w ith a half-life o f a few

secon ds ; its e ffect is loca lised to the tissu es and is n o t

sy stem ic . It is libe ra ted by su dden pre ssu re ch an ges

(Y ield Sh ea r S tres s)o n endo the lium and it d iffu se s lo ca lly

and rap id ly to re lax v ascu lar sm oo th m u sc le (E d ito r ia ls ,

Lancet 1987, 1988).

S ince the h ype raem ic e ffect is d ep enden t on v en ous

p rim in g , ED RF is p rob ab ly p ro duced by p re ssu re

ch an ges in the sm a ller veno us rad ic le s and th en d iffuse s

lo ca lly to th e c lose ly accom pany ing a rte r io la r re sis tan ce

v es sels (T ange ld er , S laa f an d R en em an 1984 ) w hich it

tem porar ily d ila te s to in crease b loo d flow . In com part-

m en t syn drom es an inc rea se in p e rfusion pres su re w ou ld

encou rage the reopen in g of c r itica lly c losed cap illa r ies

enab lin g reabso rp tion of tis sue flu id to resum e and

com partm en t p re ssu re to fa ll.

Pain . R elie f o f p ost- traum atic pa in by im pu lse pum pin g

m ay a lso be the re su lt o f h ype raem ia : it h as been show n

th at ischaem ic re st pa in is re liev ed b y th is trea tm en t

(G ardne r and Fox 1989 ). A no the r facto r m ay b e th e

re lief from venous co ngestio n and from the con sequen t

lo ca l acid osis w h ich p ro bab ly inc rea se s the pe rcep tion of

p ain (L ind ah l 19 61) .

V enou s th rom bosis. P relim ina ry resu lts sugg es t tha t

im pu lse pum pin g can red uce th e in cid ence o f deep

venous th rom bo sis a fte r k nee rep lacem en t op e ra tions .

T h is is pe rhaps to be expec ted s ince in ad d ition to

p ro duc ing hype raem ia the pum p resto re s venou s f low in

a phy sio lo g ical fash ion . V ideo ph lebo grap hy has show n

th at im pu lse p um ping produ ces tu rb u lence in va lve

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PO ST -TRAUMAT IC SW ELL ING AND COM PARTMENT PRESSURE REDUCED BY IM PULSE COM PRESS ION O F THE FOOT 815

V OL . 7 2-B , N o. 5 , SE PTEM BER 1990

pocke t s and D opp le r ve loc im e try c lear ly d em on stra ted

acce lera ted flow ra te s in the m ajo r ve ins. It is su rp r is ing

tha t th e venou s foo t-pum p w ith its re lativ ely sm all s tro ke

vo lum e , o f abou t 20 m l, can h av e such w id e-ran g ing

e ffects . I t is how eve r stra teg ica lly p laced a t the ex trem ity

to p roduce pressu re changes to lib erate E DRF and

the reb y cau se hyp e raem ia th rou ghou t the lim b . H ow eve r ,

fo r a ll th is to h ap pen , veno us p rim ing is firs t neces sary

since ve ins a re co llapsib le tub es an d pres su re im pu lse s

can o n ly be tran sm itted a lon g th em w hen th ey con ta in a

con tinuo us co lum n of b lood .

W e are grea tly in deb ted to the surgeons in sev era l coun tries w ho

collabo rated in th is stu dy . W e are m ost gra te fu l to the L eague of F rien ds

o f To rbay H osp ital and to th e S pec ia l E qu ipm ent and R esearch Fund

fo r gen erous fin anc ial su ppo rt. N ot le ast o ur thanks are due to D r A .

G oldberg an d M r And rew G ardner fo r m uch o f the o rgan isa tion of th is

t r ial .

O ne or m ore of the au thors have rece iv ed or w ill rece ive benefits

fo r p erson a l o r p ro fe ssion al use from a comm erc ia l party re la ted d irectly

or in d irectly to the sub jec t o f th is a rtic le . In add ition benefits have alsobeen or w ill be d irec ted to a research fun d , founda tion , educa tio na l

in stitu tio n , or o the r n on-pro fit ins titu tio n w ith w hich on e o r m o re of

the au tho rs is assoc iated .

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