electrotherapy for pain relief: does it work? a laboratory-based study to examine the analgesic...

8/9/2019 Electrotherapy for pain relief: does it work? A laboratory-based study to examine the analgesic effects of electroth

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E l e c t r o t h e r a p y f o r p a i n

r e l i e f : d o e s i t w o r k ?

A la b o r a to r y b a s e d s tu d y

t o e x a m i n e t h e a n a l g e s i c

e f f e c t s o f e l e c t r o t h e r a p y o n

c o l d i n d u c e d p a i n i n h e a l t h y

i nd iv idua ls

G T a b a s a m a n d M I J o h n s o n

G h a z a l a T a b a s a m

Partt ime Lecturer in

Heal th Sc iences, D r Ma rk

I .Johnson Pr inc ipa l

Lecturer- n Hum an

Physiology, Schoo l o f

Health Sciences, Faculty of

Heal th and Environment,

Leeds Metropolitan

University, Calverley S treet,

Leeds LSI 3HE, UK

Correspondence to:

GhazalaTabasam

I n t e r f e r e n t i a l c u r r e n t s I F C ) a r e a t y p e o f t r a n s c u t a n e o u s e l e c t ri c a l n e r v e s t i m u l a t i o n

T E N S ) a n d a r e p r e d o m i n a n t l y a d m i n i s t e r e d f o r t h e m a n a g e m e n t o f p a i n, h o w e v er ,

t h e re i s l i t t l e o b je c t i ve e v id e n ce t o su p p o r t t h e i r c l i n i ca l e f f e c t i ve n e ss .Th is p a p e r

d e m o n s t r a t e s t h e v a l u e o f l a b o r a t o r y -b a s e d s t u d ie s i n th e i n i t i a l a s se s s m e n t o f t h e

a n a lge s ic e f f e c ts o f a n e le c t ro th e r a p y a n d d iscusse s t h e f i n d in g s o f a s in g le b l in d

p la ce b o -co n t ro l l e d s tu d y w h ich e x a m in e d t h e a n a lg e s ic e ff e c ts o f IFC o n co ld - in d u ce d

p a in in 4 0 h e a l t h y in d iv id u a ls . Su b je c t s co m p le te d s i x cyc le s o f t h e co ld - in d u ce d p a in

t e s t d u r i n g w h i c h t h e t i m e t o p a i n th r e s h o l d s ) a n d t h e s e lf r e p o r t o f p ai n i n t e n s i t y a n d

p a in u n p le a san tn e ss 0 -1 0 c m V isu a l An a lo g u e S ca le) w e re re co rd e d . Su b je c t s w e re

r a n d o m l y a l lo c a t e d t o r e c e i v e e i t h e r a c t i v e IF C o r s h a m I F C t r e a t m e n t d u r i n g

th

t h i r d a n d f o u r t h e x p e r i m e n t a l c y c l es . T w o -w a y r e p e a t e d m e a s u re s A N O V A w e r e

p e r f o r m e d o n th e p e r c e n t a g e ch a n g e i n e a ch o u t c o m e m e a s u r e f r o m t h e p r e -

t re a tme n t b a se l in e f o r e a ch su b je c t . R e su l t s sh o w e d t h a t IFC e le va te d p a in t h re sh o ld

w h e n c o m p a r e d t o s h a m I F C d u r i n g tr e a t m e n t b u t n o t p os t t r e a t m e n t . T h e r e w e r e n o

d i ff e re n c e s b e t w e e n t h e I F C a n d s h a m t r e a t m e n t g r o u p s fo r t h e p e r c e n ta g e c h a n ge i n

p a in in te n s i t y a n d u n p le a sa n tn e ss ra t in g s . I t w a s co n c lu d e d t h a t IFC p ro d u ce d

a n a lg e sic e f fe c t s w h ich w e r e g re a te r t h a n t h o se p ro d u ce d b y sh a m IFC fo r p a in

t h r e s h o l d , b u t n o t f o r t h e p a in i n t e n s i t y a n d u n p le a s a n tn e s s r a t i n g s u n d e r t h e p r e s e n t

e x p e r i m e n t a l c o n d i t i o n s . H o w e v e r , t h e s e ef fe c ts o n l y o c c u r r e d w h e n t h e s t i m u l a t o r

w a s sw i t ch e d o n .Th e c l i n i ca l imp l i ca t io n s o f t h e se f i n d in g s a re d iscu sse d .

Ke y w o rd s : i n t e r f e re n t ia l cu r re n t t h e ra p y , e le c t ro th e ra p y , p a in , a n a lg e s ia , co ld - in d u ce d

p a in

I N T R O D U C T I O N

O v e r t h e l a s t f ew d e c a d e s t h e a d m i n i s t r a ti o n o f e l e c -

t r o t h e r a p y f o r th e m a n a g e m e n t o f a v a r i e t y o f c l i n i -

c a l c o n d i t i o n s h a s b e c o m e v e r y p o p u l a r ( P a x t o n

1 9 8 0 , R o b i n s o n e t a l . 1 9 8 8 , L i n d s a y e t a l . 1 9 90 ,

B a x t e r e t a l . 1 9 9 1 , P o p e e t a l . 1 9 9 5 ) . T h e o v e r a l l

c o s t s t o t h e N a t i o n a l H e a l t h S e r v i c e o f p u r c h a s i n g

n e w e l e c t r o th e r a p y e q u i p m e n t a r e i n t h e r e g i o n o f

s m i l l i o n a y e a r w i t h a c a p i t a l i n v e s t m e n t o f s

m i l l i o n ( I d e P a r t r i d g e 1 9 8 8 ). I t h a s b e e n e s t i m a t e d

t h a t t h e r e a r e c u r r e n t l y m o r e t h a n 2 5 0 0 0 e l e c t r o t h e r -

a p y d e v i c e s u s e d b y t h e N H S i n t h e U K ( P o p e e t al .

1 9 9 5) . T w o o f t h e m o s t p o p u l a r e l e c t r o t h e ra p i e s

l i n ic a l E f f e c ti v e n e s s i n N u r s i n g

(I 999) 3, 14-24 9 1999 Harcourt Brace& Co. Ltd


2/11

e m p l o y e d b y t h e r a p i s t s in t h e U K a r e tr a n s c u t a -

n e o u s e l e c t r i c a l n e r v e s t i m u l a t i o n ( T E N S ) a n d

i n t e r f e r e n t i a l c u r r e n t t h e r a p y ( 1 F C ) .

T E N S i s u s e d w i d e l y b y n u r s es a n d m i d w i v e s t o

r e l i e v e p o s t o p e r a t i v e p a i n , l a b o u r p a i n a n d c h r o n i c

p a i n ( R e e v e e t a l . 1 9 9 6 ) . T h e r e i s a v a s t l i t e r a t u r e

o n T E N S , a l t h o u g h r e c e n t s y s t e m a t i c r e v i e w s s u g -

g e s t t h at T E N S i s n o m o r e e f f e c t i v e th a n p l a c e b o

f o r p o s t o p e r a t i v e p a i n ( C a r r o l l e t a l . 1 9 9 6 ) a n d

l a b o u r p a i n ( C a r r o l l e t a l . 1 9 9 7 ) a n d i t s e f f e c t iv e -

n e s s f o r t h e m a n a g e m e n t o f c h r o n i c p a i n i s a l s o a t

p r e s e n t u n c l e a r ( R e e v e e t a l. 1 9 9 6 , G a d s b y

F l o w e r d e w 1 9 9 7 ) .

I F C i s a t y p e o f T E N S t h a t is u s e d p r e d o m i n a n t l y

b y p h y s i o t h e r a p i s t s fo r t h e m a n a g e m e n t o f p a i n f u l

c o n d i t i o n s . T o d a t e , n o s y s t e m a t i c re v i e w s h a v e

b e e n p e r f o r m e d t o a s s e s s t h e c l i n i c a l e ff e c t i v e n e s s

o f I F C . T h e I F C l i t e ra t u r e co n s i s t s o f m a n y u n c o n -

t r o l l e d s tu d i e s a n d e f f e c t i v e n e s s i s b a s e d o n a n e c d o -

t a l e v i d e n c e ( N i k o l o v a 1 9 67 , 1 9 8 7, N e l s o n 1 9 8 1,

E i g l e r 1 9 7 9 ) .

I t is c o m m o n s c i e n t if i c p r a c t i c e t o e v a l u a t e a n y

n e w t r e a t m e n t , b e f o r e i m p l e m e n t i n g i t , a n d t o

c a t a l o g u e i t s p o t e n t i a l b e n e f i t s a n d s i d e e f f e c t s a s

w e l l a s i t s s u p e r i o r i t y o v e r e x i s t i n g t r e a t m e n t s .

I n i t ia l i n s ig h t s i n t o t h e e f f e c t i v e n e s s o f a n a n a l g e s i c

i n t e r v e n t i o n c a n c o m e f r o m l a b o r a t o r y - b a s e d

e x p e r i m e n t s u s i n g h e a l t h y s u b j e c t s . A s i n g l e - b l i n d

p l a c e b o - c o n t r o l l e d s t u d y w h i c h w a s p e r f o r m e d t o

e x a m i n e t h e a n a l g e s i c e f fe c t s o f I F C i n 4 0 h e a l t h y

v o l u n t e e r s u s i n g t h e c o l d - i n d u c e d p a i n t e c h n i q u e

w i l l b e u s e d t o h i g h l i g h t t h e i m p o r t a n c e o f s u c h

w o r k . T h e a i m o f t h is p a p e r i s t o d e m o n s t r a t e t h e

v a l u e o f l a b o r a t o r y - b a s e d s t u d i e s i n t h e i n i t i a l

a s s e s s m e n t o f a n a n a l g e s i c i n t e r v e n t i o n u s i n g a

l a b o r a t o r y - b a s e d s t u d y a s a n e x a m p l e .

B C K G R O U N D

I F C a r e a t y p e o f T E N S a n d a r e u s e d p r e d o m i n a n t l y

b y p h y s i o t h e r a p i s t s t o m a n a g e a r a n g e o f c l i n i c a l

c o n d i t i o n s ( D e D o m e n i c o 1 9 87 , N i k o l o v a 1 9 87 ,

S a v a g e 1 9 9 2, L o w R e e d 1 9 94 , M a r t i n 19 9 4 , P o p e

e t a i. 1 9 9 5 ). D u r i n g I F C t h e r a p y t w o o u t o f p h a s e

m e d i u m - f r e q u e n c y e l e c t r i c a l c u r r e n t s ( 2 - 4 K h ) a r e

d e l i v e r e d a c r o s s t h e s u r f a c e o f th e s k i n . T h e s k i n

o f f e r s l i t t l e r e s i s t a n c e t o e l e c t r i c a l c u r r e n t s a t t h i s

f r e q u e n c y r a n g e a n d b y o v e r c o m i n g s k i n i m p e d a n c e

t h e c u r r e n t i s a b l e t o p e n e t r a t e d e e p e r i n t o t h e t i s -

s u e s . A t t h e p o i n t w h e r e t h e t w o c u r r e n t s c l a s h o r

i n t e rf e r e a n e w ' i n t e r f e r e n c e ' w a v e i s p r o d u c e d . T h e

r e s u l t a n t i n t e r f e r e n c e w a v e i s m o d u l a t e d i n i t s

a m p l i t u d e a n d i t i s c l a i m e d t h a t t h i s a m p l i t u d e m o d -

u l a t e d w a v e i s a b l e t o e x c i t e t is s u e l o c a t e d i n d e e p -

s e a t e d s tr u c t u re s t o p r o d u c e a v a r i e t y o f p h y s i o l o g i c a l

a n d e f f e c ts w h i c h c o n t r i b u t e t o t h e p r o p o s e d c l i n i c a l

e f f e c t s o f t h i s m o d a l i t y ( s e e F i g . 1 ). I F C i s o n e o f

t h e m o s t f r e q u e n t l y u s e d e l e c t r o t h e r a p i e s e m p l o y e d

b y p h y s i o t h e r a p i s t s ( P o p e e t a l . 1 9 9 5 ). A r e c e n t s u r -

v e y b y o u r s e l v e s h a s f o u n d t h a t p h y s i o t h e r a p i s t s u s e

E l e c t r o t h e r a p y f o r p a in r e li e f: d o e s i t w o r k ? 1 5

i AAAAAAAAAAAAAAAAAAAAAA

VVVVVVVVVVVVVVVVVVVVVV

C u r r e n t 1 4 O H z

IL

T i m e

i AAAAAAAAAAAAAAAAAAAAAA

~ VVVVVVVVVVVVVVVVVVVVVV

C u r r e n t 2 41OOHz T i m e

Currents l and 2

_~ cancelout here

l ' v V v v vv v v v vv ' , ,s

Where currents 1 and 2 interfere N

a 100Hz ampli tude modulated Sum matio nf

.wave is forme d currents

F i g . I T h e f o r m a t i o n o f a n i n te r f e re n c e c u r re n t w a v e . T w o

o u t o f p h a se c u r r e n t s a ) a n d b ) a r e d e l i v e r e d a c ro s s t h e

s u r f a c e o f t h e s k i n t o g e n e r a t e a n in t e r e f e r e n c e c u r r e n t c )

w h i c h i s m o d u la t e d i n i ts a m p l i tu d e . C u r r e n t a ) a n d b ) a r e

d e l i v e r e d i n t h e k i l o h e r t z r a n g e t o o v e r c o m e t h e r e s is t an c e o f

t h e s k i n . I t i s c l a im e d t h a t t h e r e s u l t a n t a m p l i t u d e m o d u la t e d

i n te r f e re n c e w a v e , w h i c h h a s a f re q u e n c y o f a p p r o x i m a t e l y

1 0 0 H z , e x c i t e s d e e p - s e a t e d n e r v o u s t is s u e l e a d in g t o

analgesia

I F C t o r e l i e v e p ai n , r e d u c e s w e l l i n g , p r o m o t e h e a l i n g

o f w o u n d s a n d b o n e f r a c t u r e s , a n d t o r e s t o r e f u n c -

t i o n a s s o c i a t e d w i t h m u s c l e w e a k n e s s ( J o h n s o n

T a b a s a m 1 9 9 8) .

I t h as b e e n s u g g e s t ed t h at I F C m a y b e m o r e

e f f e c t i v e t h a n T E N S f o r t h e t re a t m e n t o f p a i n s o f

m u s c u l o s k e l e t a l o r v i s c e r a l o ri g i n . I F C m a y , t h e r e -

f o r e , b e m o r e c l i n i c a l l y e f f e c t iv e t h a n T E N S f o r c e r -

t a i n c o n d i t i o n s a n d , t h u s , i t m a y b e n e c e s s a r y t o

i n d i c a t e I F C a n d T E N S f o r t h e tr e a t m e n t o f d i f f e r -

e n t c l i n i c a l c o n d i t i o n s . T h i s t h e o r y , h o w e v e r , i s

e n t i r e l y s p e c u l a t iv e a n d a t p r e s e n t h a s n o o b j e c t i v e

e v i d e n c e i n i t s s u p p o r t .

P r o b l e m s w i th I F C l i t e r a t u r e

T h e l i t e r a tu r e o n I F C i s s p a r s e a n d t h e r e i s a l a c k o f

o b j e c t i v e e v i d e n c e s u p p o r t i n g i t s c l a i m e d a n a l g e s i c

e f f e c t i v e n e s s . P u b l i s h e d s t u d i e s o n I F C l a c k a d e -

q u a t e c o n t r o l o r p l a c e b o g r o u p s , a n d t h i s d r a w s i n t o

q u e s t i o n t h e r e l i a b i l i t y a n d v a l i d i t y o f t h e r e s u l ts

a n d c o n c l u s i o n s .

T h e p l a c e b o e f f e c t i s a p o w e r f u l p h e n o m e n o n

w h i c h r e l i e v e s m a n y c o n d i t io n s i n c l u d i n g p a i n ( W a l l

1 9 9 3 ) a n d t h e i m p o r t a n c e o f d e t e r m i n i n g w h e t h e r

e l e c t r o t h e r a p i e s p r o d u c e e f f e c t s o v e r a n d a b o v e t h o s e

o f p l a c e b o c a n n o t b e e m p h a s i z e d e n o u g h ( G e o r g i o u

1 9 96 , M c Q u a y M o o r e 1 9 96 ). P l a c e b o i n t e r v en -

t i o n s a r e u s e d i n r e s e a r c h t o e n a b l e i n v e s t i g a t o r s t o

d i s c r i m i n a t e b e t w e e n t h e e f f e c t s o w i n g t o a n a c t i v e

i n g r e d i e n t i n t h e t h e r a p e u t i c a g e n t a n d n o n - s p e c i f i c

e f f e c t s w h i c h c a n r e s u l t f r o m m a n y f a c t o r s i n c l u d i n g

t h e i n t e r a c t i o n b e t w e e n i n v e s t i g a t o r a n d s u b j e c t .

P l a c e b o s h a v e n o k n o w n a c t i v e th e r a p e u t ic i n g r e d i -

e n t a n d t h e y a r e u s e d t o i m i t a t e t h e t r e a t m e n t u n d e r

s t u d y . I f t r e a t m e n t e f f e c t s a r e s h o w n t o b e n o g r e a t e r


3/11

6 C l i n i c a lEf fect iveness in Nu rsing

than p lacebo , then i t i s importan t to ques t ion the

phys io log ica l ra t iona le underp inn ing the c l in ica l use

o f th e t r e a tm e n t . N e w d ru g s a re r e q u i re d to u n d e rg o

thorough eva lua t ions in the labora to ry to p rove tha t

th e d ru g p ro d u c e s e f f e c t s w h ic h a re g re a t e r t h a n

th o s e p ro d u c e d b y a p l a c e b o d ru g (W a l l 1 9 93 ). T h i s

i s a c h ie v e d b y p e r fo rm in g p la c e b o -c o n t ro l l e d s tu d ie s

in th e l a b o ra to ry b e fo re th e t r e a tm e n t i s im p le m e n te d

in the c l in ic . Th is , however , i s no t the case a t p resen t

fo r e lec tro the rap ies , such as TENS and IFC. I t i s

be l ieved tha t p lacebo e ffec ts a re o f ten g rea tes t fo r

expens ive , and impress ive look ing the rap ies such as

TENS and o the r e lec tro the rap ies (Evans 1985 , Wall

1 9 9 4 ) . Mo d e m IF C s t im u la to r s l o o k t e c h n ic a l ly

impress ive and requ ire ac t ive the rap is t invo lvement

in the admin is t ra t ion o f the t rea tment . The p roduc t io n

of an unfamil ia r t ing l ing sensa t ion a lso fu r the r

enhances the p lace bo e ffec t a s soc ia ted with IFC s t im-

u la to rs (Evans 1985 , Kien le & Kiene 1998) .

T h e re i s a n e e d fo r m o re r ig o ro u s ly c o n t ro l l e d

s tu d ie s w h ic h in c o rp o ra t e a p l a c e b o t r e a tm e n t g ro u p

to a s s e s s th e t ru e t r e a tm e n t e f f e c t s o f IF C . T h i s w i l l

a l lo w b o th th e ra p is t a n d p a t i e n t t o b e c o n f id e n t t h a t

th e t r e a tm e n t i s p ro d u c in g i t s e f f e c t s o w in g to a n

a c t iv e c o m p o n e n t o f t h e th e ra p y .

T h e re a re m a n y e th i c a l c o n c e rn s r e g a rd in g th e

admin is t ra t ion o f a p lacebo t rea tment to pa t ien ts su f-

fe r ing from c l in ica l pa in . Th is makes i t d i f f icu l t to

p e r fo rm c l in i c a l s tu d ie s w h ic h in c o rp o ra t e p l a c e b o

contro l g ro ups tha t a re a im ed a t a s sess ing the c l in ica l

e ffec t iveness o f a the rapy . However , in i t ia l ins igh ts

in to the the rapeu t ic e ffec t iveness and p lacebo e ffec ts

a s s o c ia t e d w i th a th e ra p y c a n c o m e f r o m l a b o ra to ry -

based s tud ies on hea l thy ind iv idua ls .

Laboratory s tudies

T h e in i t i a l a s s e s sm e n t s o f a n y n e w a n a lg e s i c

t r e a tm e n t c o n s i s t s o f t h o ro u g h e v a lu a t io n s in th e

l a b o ra to ry o n h e a l th y in d iv id u a l s b e fo re t r i a l s a re

c o n d u c te d o n p a t i e n t s i n th e c l in i c . L a b o ra to ry -

b a s e d s tu d ie s a l lo w th e in v e s t ig a to r s :

9 to c h e c k th e s a fe ty a n d e f f e c t iv en e s s o f t h e

trea tment be fore c l in ica l t r ia ls

9 to a s s e ss th e e f f ic a c y o f a t r e a tm e n t u n d e r

s t r i ct ly c o n t ro l l e d c o n d i t io n s

9 to c a re fu l ly c o n t ro l a n d m a n ip u la t e th e

o u tc o m e m e a s u re s u n d e r s tu d y , su c h a s th e

in t e n s i ty a n d th e lo c a t io n o f t h e p a in

9 to c a re fu l ly c o n t ro l a n d m a n ip u la t e th e

t r e a tm e n t p a ra m e te r s u n d e r in v e s t ig at io n .

T h e re a re a v a r i e ty o f ex p e r im e n ta l p a in m o d e l s

w h ic h h a v e b e e n u s e d b y w o rk e r s to in d u c e p a in in

hea l thy sub jec ts in labora to ry s tud ies (e .g . e lec tr i -

c a l , t h e rm a l , m e c h a n ic a l a n d c h e m ic a l ) . T h e c o ld -

i n d u c e d p a i n t e c h n i qu e h a s b e e n e m p l o y e d f o r o v e r

5 0 y e a r s to e v a lu a te th e a n a lg e s i c e f f e c ts o f d ru g s

and e lec tro the rap ies in hea l thy sub jec ts and i t i s

e s t a b l is h e d a s a s a fe m e th o d fo r t h e in d u c t io n o f a

deep-sea ted , ach ing , pa in sensa t ion s imila r to tha t

exper ienced b y pa t ien ts su ffe r ing c l in ica l pa in (W olff

e t a l, 1966 , Posn er e t a l. 1985 , Grac e ly 1989, Grace ly

1994) . The tech n ique invo lves the imm ers ion o f the

d is ta l por t ion o f a l imb (usua l ly the hand) in to ve ry

c o ld w a te r t o p ro d u c e a r a p id o n s e t o f p a in s e n s a tio n .

A v a r i e ty o f o u tc o m e m e a s u re s c a n b e m o n i to re d

during the co ld- induced pa in te s t inc lud ing the t ime-

to -pa in th resho ld , and pa in to le rance and pa in ra tings

such as pa in in tens i ty and unp leasan tness .

S tu d ie s w h ic h h a v e e x a m in e d th e a n a lg e s i c

e f fe c t s o f IF C o n e x p e r im e n ta l ly - in d u c e d p a in in

h e a l th y s u b je c ts h a v e p ro d u c e d c o n f l i c t in g re s u lt s .

S c o t t a n d P u rv e s (1 9 9 1 ) e x a m in e d th e e f fe c t s o f IF C

o n i s c h a e m ic p a in in d u c e d b y th e to u rn iq u e t t es t o n

1 5 h e a l th y v o lu n te e r s . T h e y fo u n d th a t a c t iv e IF C

d id n o t e l e v a te t im e to to l e ra n c e o f i s c h a e m ic p a in

w h e n c o m p a re d to a s h a m IF C s t im u la to r . In c o n -

t r as t , p re l im in a ry w o rk u s in g th e c o ld - in d u c e d p a in

t e c h n iq u e b y o u r g ro u p fo u n d th a t IF C c a n e l e v a te

th e t im e to p a in th re s h o ld in h e a l th y v o lu n te e r s ,

a l th o u g h a p l a c e b o c o n t ro l g ro u p w a s n o t e m p lo y e d

(S te p h e n s o n & J o h n s o n 1 99 5 ).

T h e fo l lo w in g l a b o ra to ry -b a s e d s tu d y w a s p e r -

fo rm e d to in v e s t ig a te th e a n a lg e s i c e f f e c t s o f IF C

u n d e r p l a c e b o -c o n t ro l l e d c o n d i t io n s u s in g a n e x p e r -

im e n ta l p a in m o d e l .

M E T H O D O L O G Y

Subjects

F o r ty e l e c t ro th e ra p y n a iv e , h e a l th y u n iv e r s i ty s u b -

j e c t s w e re r e c ru i t e d f ro m n o t i c e -b o a rd a d v e r t i s e -

m e n t s (2 9 f e m a le s , 1 1 m a le s ; a g e m e a n = 2 6 y e a r s ) .

A l l s u b je c t s a t t e n d e d th e l a b o ra to ry fo r a b r i e f

f a m i l i a r i z a t io n s e s s io n w i th in th e w e e k p re c e d in g

th e e x p e r im e n t , d u r in g w h ic h th e y w e re g iv e n a

v e rb a l a n d w r i t t e n e x p la n a t io n o f th e n a tu re o f

th e e x p e r im e n t . A l l s u b je c t s w e re a l s o s c re en e d fo r

c o n t ra in d ic a t io n s to e l e c t ro th e ra p y a s in d ic a t e d b y

th e C h a r t e re d S o c ie ty o f P h y s io th e ra p y ( s t an d a rd s

fo r th e u s e o f e l e c t ro p h y s ic a l m o d a l it i e s) . S k in w a s

te s t e d fo r n o rm a l s e n s a t io n b y u s in g s t a n d a rd

sharp /b lun t and ho t /co ld te s ts , and a l l sub jec ts

a d m i t t e d o n to th e s tu d y c o m p le te d a c o n s e n t fo rm .

A l l e x p e r im e n t s w e re a p p ro v e d b y th e L e e d s

Me t ro p o l i t a n U n iv e r s i ty E th ic s C o m m i t t e e .

E X P E R I M E N T L P R O C E D U R E

The experim ents were cond uc ted by a female inves t i -

ga to r (GT) us ing a s imila r me thodology to tha t

employed in p rev ious s tud ies pe rfo rmed by the

authors (Johnson et a l. 1989, Johnson et a l. 1992,

S tephenson & Johnson 1995 , Tabason and Johnson

1996, Tabasam & Johnson 1997). All subjects

fo l low ed a se t o f wri t ten insmac t ions dur ing the exper-

imenta l sess ion under the gu idan ce o f the inves t iga to r .


4/11

Electrotherapy for pain relief: does it work? 17

T r e a t m e n t T r e a t m e n t

S w i t c h o n h o f f

C o ld in d u ced ~ C

pain test

I lOmin cyce

C y c l e 1 C y c l e 2 C y c l e 3 C y c l e 4 C y c l e 5 C y c l e 6

I I I I I I I

min 1 rain 2 rain 3 rnin 4 rnin 5 min 6 rain

m e~

Fig. 2 Time course of the experimental procedure

Subjects were randomly allocated, by pulling a

number out of a hat, to one of the following treat-

ment groups before the start of the experiment:

9 active IFC

9 sham IFC

Each subjects completed 6 10 min cycles of the

cold-induced pain test (two pre, two dur ing and two

post treatment) (see Fig. 2). The outcome measures

during each of the six experimental cycles of the

cold-induced pain test were:

9 the time to pain threshold

9 and the self report of pain intensity and pain

unpleasantness.

P A IN I N D U C T I O N O N E C Y C L E O F

T H E C O L D - I N D U C E D P A I N T E S T )

During each cycle of the cold- induced pain test, the

subjects non-domin ant hand was innnersed into a

warm water bath (37~ for 5 min (Fig. 3). The hand

was then transferred into (iced) cold water (0-2~

until it became defin itely painfu l (e.g. 'the ve ry first

sensation of pain in the han d') when the subject made

the statement 'P ain!' . Time-to-pain threshold was

recorded as the time from hand immersion in cold

water to the very first sensation of pain. The hand

remained immersed in the cold water for a further 30

s after which it was removed . Pain intens ity and pain

unpleasantness ratings were recorded as the intensity

and unpleasantness of pain immediately prior to

removal of the hand from the cold water and were

recorded using a 10 cm visual analogue scale (where

0= no p ain and 10= worst pain imaginable for pain

intensity, 0= not unpleasant at all and 10= most

unpleasant I could imagine for pain unpleasantness).

If clarification on how to distinguish between

pain intensity and pain unpleasantness was

requested by the subjects they were told that inten-

sity related to 'the severity of the pain in the hand'

and unpleasantness to 'the way that you feel about

the pain in the hand '. The cycle was completed by a

rest period whereby the subject read a magazine.

Prior to the start of the experiment, four self-

adhesive electrodes (4 4 cm) were applied to all

subjects in a quadripolar fashion on the anterior

aspect of the subjects forearm 5 cm above the first

wrist crease (Fig. 4). The purpose of these electrode

HAND IN

Warm HAND IN

Water Ice Water

at 37~

I

141 hi4

I I

I 5 Min i

t t

"PAIN"

Pain

Threshold

HAND

OUTPain Ratings

30 sec i

5 Min

R e s t ~ I

~J

i

Pain ntensity cale

0 10

No Pain Worst Pain

Imaghlable

P a i n u n p l e a s a n t n e s s s c a l e

0 10

Not Most

Unpleasant unpleasant I

at all could magine

Fig 3 One cycle cold induced pain


5/11

8 Clinica l Effectiveness in Nurs ing

q

~Anterior aspect of the arm

Nerve activity generated

k ~ / ( travels toward the central

nervous system

II Channel 1 electrodes

Channel 2 electrode s

Fig

4 The location of the electrodes used to deliver

treatment. a) Electrode placement on anterio r aspect of the

arm. b) The location of the resultant interference wave

placements was to ta rge t the median nerves (deep

affe rents emerging from the pa infu l , immersed

hand) . Al thoug h the e lec t rodes were appl ied pr ior to

the s ta r t of the exper imenta l procedure , the t rea t -

ment w as only adm iniste red dur ing cyc les 3 and 4

(e .g . the two during t rea tment cyc les) dur ing which

a l l subjec ts rece ived 20 min of unin te rrupted t rea t -

ment (e i ther ac t ive or sham IFC).

T R E T M E N T

G R O U P S

A l l su b je c t s r e c e iv e d t r ea tme n t w h ic h w a s d e l iv e re d

u s in g a n EMS M e d i -L in k c o n t ro l mo d u le Mo d e l 7 0

a n d Me d i -L in k In t e r fe re n t i a l mo d u le mo d e l 7 1 . Th e

current output f rom th is device was regula ted en

route to the s ubjec t using an e lec t ronic c i rcui t which

enabled the invest ig a tor to contro l whether or not

the subjec ts rece ived a current output f rom the IFC

device (e .g . rece ived e i ther ac t ive IFC or sham

IFC), but i t d id not a l te r the output charac te r is t ics of

IFC in any way. In addi t ion , the output f rom the IFC

d e v ic e w a s d i sp l a y e d o n a c a th o d e r a y o sc i l l o sc o p e

during the t rea tment cyc les for both the ac t ive and

sham t rea tment groups.

Act ive IFC

A c t iv e IFC w a s sw i t c h e d o n a t th e e n d o f t h e se c o n d

pre- t rea tment cyc le and the in tensi ty of s t imula t ion

was adjusted by the subjec t to produce a ' s t rong

but com fort able s timul ation' (mean~_+SD = 8.45+

2.65 mA). Subjec ts were requested to mainta in th is

in tensi ty leve l throughout the two t rea tment cyc les

by making m inor ad justm ents to the in tensi ty d ia l of

the IFC uni t . The e lec t r ica l charac te r is t ics of ac t ive

IFC were chosen fo l lowin g examina t ion of the l ite r-

a ture which indica ted tha t an ampl i tude modula ted

f re q u e n c y o f 1 0 0 H z sh o u ld b e e mp lo y e d w h e n

using IF C for the re l ie f of pa in (DeDom enico 1987,

Niko lova 1987, Savage 1992, Low Reed 1994,

Mart in 1994, Pope e t a l . 1995) . There i s , however ,

a t present , no s t rong evidence to support the use of

th is f requency. The ampl i tude modula ted wave was

de l ivered using a cont inuous pa t te rn~ which was

a c h ie v e d b y u s in g tw o s in u so id a l c a r r i e r w a v e s

de l ivered a t 4000 cyc les per second and 4100 cyc le s

per second (Fig. 1).

S h a m I F C

Sham IFC was used as the p lacebo contro l . Sham

IFC w a s d e l iv e re d u s in g th e sa me IFC d e v ic e as

used for the ac t ive IFC group except tha t the sub-

jec ts rece iv ed no current output . The p lacebo e ffec t

was re inforced by a verba l suggest ion f rom the

invest iga tor tha t, 'The IF C uni t re l ieves pa in by sub-

threshold s t imula t ion which you wi l l not be able to

fe e l ' , a n d b y d i sp l a y in g th e o u tp u t f ro m th e IFC

device on a ca thode ray osc i l loscope . No subjec ts in

the present s tudy qu est ioned th is procedure .

S T A T I S T I C A L A N A L Y S I S

A pre- t rea tment base l ine mean was ca lcula ted for

the two pre- t rea tment cyc les for each indiv idua l .

Be tween subjec t var iance in pre - t rea tment base l ine

va lues was la rge , as ev idenced by the SD va lues

and, there fore , the percentage change in pa in thresh-

old f rom the pre - t rea tment base l ine was used as a

su mma ry me a su re o f r e sp o n se . Th e p e rc e n ta g e

change in outcome measures dur ing and post t rea t -

ment w as ca lcu la ted by subtrac t ing the pre - t rea t -

ment mean from each of the dur ing and

post - t rea tment observa t ions, and represent ing the

va lue as a percentage change from the pre - t rea tment

base l ine mean. A two-way ana lysis of var iance for

re p e a t e d me a su re s (RM-A N O V A ) w a s p e r fo rme d

on the percentage change for each of the outcome

measures (Jande l Sc ient i f ic Gm bH 1994) .

RE S ULTS

The mear~+SD results for ice pain threshold, pain

in tensi ty and unpleasantness ra t ing a re shown in

Table 1. Pre-treatment baseline measures w ere similar

in magni tude to previous work in th is and o ther labo-

ratories using the s ame tech nique (Pos ner et al . 1985,

Johnso n Wils on 1997, Tabason Johnson 1996).

I CE P A I N T H R E S H O L D

No signif icant d i f fe rences in pa in threshold where

found be tween the two pre- t rea tment cyc les

(mear~+SD diffe rence pre - t rea tmen t cyc le 1 and 2 =

-0 .43s+ 4.5s, P=0.55 , p a i red t - test , n=40) . The mean


6/11

P ~

t r e a t m e n t I

E l e c t r o t h e r a p y f o r p a in re l ie f : d o e s i t w o rk? 9

P e r D u r i n g D u r i n g P o s t P o s t

t r e a t m e n t 2 t r e a t m e n t I t r e a t m e n t 2 t r e a t m e n t I t r e a t m e n t 2

P a i n t h r e s h o l d s )

a c t i ve 1 8 .1 + 1 2 .7 1 6 . 9 + 1 0 .6 2 1 . 8 + 1 3 .2 2 4 . 4 + 1 5 .2 2 1 . 0 + 1 7 .2 2 1 . 4 + 1 7 .8

s h a m 1 8 .2 _ + 1 0 . 7 2 0 . 3 _+ 1 2 . 6 2 0 . 5 + 1 2 . 1 2 2 . 6_ + 1 2 . 6 2 0 . 7_ + 1 2 . 8 2 0 . 5_ + 1 2 . 2

P a i n i n t e n s i t y c m s )

ac t i ve 5 .8 _+ 2 .0 6 .0 _+ 1 .9 5 .6 + 2 . I 5 .8 + 1 .9 6 .2 + 2 .2 6 .3 + 2 .0

sham 5.7 _+ 1 .9 5 .6 _+ 2 .2 5 .6 _+ 1 .8 5 .4 _+ 2 . I 6 . I + 2 .2 6 .3 _+ 2 .5

P a i n u n p l e a s a n t n e s s c m s )

ac t i ve 6 ,2 _+ 2 .0 6 .3 _+ 2 .0 5 .7 + 2 .2 6 .2 _+ 2 .2 6 .7 _+ 2 .4 6 .7 + 2 .2

s h a m 6 . 5 + 2 , 3 6 . 2 _+ 2 . 6 6 . 0 _ + 2 . 7 5 . 6 + 2 . 6 6 . 3 _ + 2 . 6 6 . 2 + 3 . 0

pre-treatment baseline was calculated for each ind i-

vidual and no significant differences in this baselin e

were found between the two treatment groups

(mea~+SD IFC=17.5s+ll.6s, sham=19.2s+ll.4s,

P=0.63, unpaired t-test, n=20 per group).

There was rapid rise in the percentage change in

pain threshold for the IFC group which occurred

within 10 min of ]FC switch on (Fig. 5). This eleva-

tion in pain threshold rapidly declined and had

returned to 20 of the baseline value within 10 min

of IFC switch off. The percentage change in pain

threshold for the sham group mirrored that of the

IFC group across the treatment cycles, although i t

was significantly smaller in magnitude. This

response profile for the sham IFC group is similar t o

that observed for other placebo electrotherapyies

administered in previous experiments by ourselves

and others.

These observations were con firmed in the statis-

tical analysis. A two-way analysis of variance for

repeated measures (RM-ANOVA) was performed

on the percentage change in pain threshold from the

pre-treatment baseline for the two during- and two

post-treatment cycles. Significant effects were

foun d for time (e.g. across the two during- and two

post-treatment cycles: P0.05). The percentage change

in pain ratings from the pre-treatment baseline for

each of the during and post-treatment observations

was calculated (Fig. 6 & 7). The results of the RM-

ANOVA across the two during- and two post-treat-

ment cycles are shown in Table 2.

P a i n i n t e n s i t y r a t i n g

There were no significant group effects for pain

intensity ratings (Fig. 6, Table 2). S ignificant effects

were found across the different levels of time


7/11

2 0 l in i c a l E f f e c t iv e n e s s i n N u r s i n g

A c r o s s t w o d u r i n g a n d p o s t

t r e a t m e n t c y c l e s

A c r o s s tw o d u r i n g

t r e a t m e n t c y c l e s

D F F P D F F P

P a in t h r e s h o ld

t im e 3 5 . 4 0 . 0 0 2

g r o u p I 3 . 4 0 . 0 7

g r o u p x t im e i n t e r a c t i o n 3 1 .5 0 . 2

Pain- intensity rat ing

t im e 3 3 . 3 0 . 0 2

g r o u p I 0 . 3 0 . 5 5

g r o u p x t im e i n t e r a c t i o n 3 0 . 7 0 . 5 4

Pain-unp leasantness ra t ing

t im e 3 7 . 7 0 . 0 0 0 I

g r o u p I 1 .8 0 . 2

g r o u p x t im e i n t e r a c t i o n 3 3 . I 0 . 03

8 . 2 0 . 0 0 7

3 . 7 0 . 0 6

0 . 3 3 0 . 5 7

0.19 0.66

0.49 0.5

1.5 0.22

O 18 0.68

1.22 0.28

10.2 0.003

~ 2 ~

~ ~

20

g ~ o

o N s

-10

e ~

D~g 1 Org 2 Post 1 Post 2 ~

i 10 min

20

ain 10 min

20

min

E x p e r i m e n t a l C y c l e

F i g 6 Mean_+SE ercentage change in pa in in tens i t y ra t ing

f r o m p r e - t r e a t m e n t b a s e li n e f o r sh a m - n - - ) a n d I FC - 0 - )

g r o u p s

D r g = d u r i n g t r e a t m e n t ; P o s t = p o s t t re a t m e n t

( e . g. t w o d u r i n g a n d t w o p o s t - t r e a t m e n t c y c l e s ) f o r

t h e p e r c e n t a g e c h a n g e i n p a i n i n t e n s i t y r a t in g f r o m

t h e p r e - t r e a t m e n t b a s e l in e . T h e r e w e r e n o s i g n i f i-

c a n t e f fe c t s b e t w e e n t h e I F C a n d s h a m w h e n t h e d i f -

f e r e n t l e v e l s o f t i m e w e r e t a k e n i n t o a c c o u n t ( t i m e x

g r o u p i n t e r a c t i o n , T a b l e 2 ) . A n a d d i t i o n a l R M -

A N O V A w a s p e r f o r m e d u s i n g o n l y d a ta f r o m t h e

t w o d u r i n g - t r e a t m e n t c y c l e s . N o s i g n i f i c a n t e f f e ct s

w e r e f o u n d ( T a b l e 2 ).

P a i n U n p l e a s a n t n e s s r a t i n g

S i g n i f i c a n t e ff e c t s w e r e f o u n d f o r t i m e ( e .g . t w o

d u r i n g - a n d t w o p o s t - t r e a t m e n t c y c l e s ) a n d f o r t im e

g r o u p i n t e r a c t i o n ( T a b l e 2 ) .

A n a d d i ti o n a l R M - A N O V A w a s p e r f o r m e d

u s i n g o n l y d a t a f r o m t h e t w o d u r i n g t r e a t m e n t

c y c l e s . S i g n i f i c a n t e f f e c t s w e r e f o u n d f o r g r o u p x

t i m e i n t e r a c t i o n ( P = 0 . 0 0 3 ) , b u t n o t f o r t i m e o r f o r

g r o u p ( T a b l e 2 ) . S u b j e c t s i n t h e I F C g r o u p r a t e d

p a i n t o b e m o r e u n p l e a s a n t d u r i n g t h e s e c o n d t r e a t -

m e n t c y c l e , a l t h o u g h t h e m a g n i t u d e o f t h e t h is e l e -

v a t i o n w a s s m a l l ( F i g . 7 ) . A d e c r e a s e i n p a i n

F i g 7

2 0 -

1 5 -

1 0 -

5 .

0 '

5.

- 10 . q \ \ / /

-15 ~

-20 i i ~ I

~ Drg 1 Drg 2 Post 1 Post 2

~ t0 min 20 ra in 10 ra in 20 ra in

~. E x p e r i m e n t a l C y c l e

Plean+SE percen tage cha nge in pain unpleasantness

f r o m p r e - t r e a t m e n t b a s e l in e f o r s h am - - n - - ) a n d I FC - Q - )

g r o u p s

D r g = d u r i n g t r e a t m e n t ; P o s t = p o s t t r e a t m e n t

u n p l e a s a n t n e s s o c c u r r e d d u r i n g t r e a t m e n t i n t e r v e n -

t i o n f o r t h e s h a m g r o u p , w h i c h r a p i d l y r e tu r n e d t o

b a s e l i n e o n t r e a t m e n t t e r m i n a t i o n . T h is c h a n g e w a s

n o t s t a t i s t i c a l l y s i g n i f i c a n t .

S U M M A R Y O F T H E M A I N F I N D I N G S

T h e m a i n f i n d i n g s o f t h is s t u d y w e r e t h a t :

9 I F C e l e v a t e d p a i n t h r e s h o l d w h e n c o m p a r e d t o

s h a m I F C d u r i n g t h e t w o t r e a t m e n t c y c l e s (e . g .

w h e n t r e a t m e n t w a s s w i t c h e d o n ) b u t n o t p o s t

t r e a t m e n t

9 n o d i f f e re n c e s w e r e o b s e r v e d b e t w e e n t h e I F C

a n d s h a m f o r t h e p e r c e n t a g e c h a n g e i n p a i n

i n t e n s i ty a n d u n p l e a s a n t n e s s r a t i n g s

9 a s i g n i f i c a n t i n c r e a s e i n p a i n i n t e n s i t y o c c u r r e d

d u r i n g a n d a f t e r t h e t r e a t m e n t i n t e r v e n ti o n

a l t h o u g h t h e r e w e r e n o s i g n i f i c a n t d i f fe r e n c e i n

t h e m a g n i t u d e o f t h e s e c h a n g e s b e t w e e n t h e

g r o u p s .


8/11

D I S U S S I O N

T h i s s t u d y h a s s h o w n d i f f e r e n c e s in t h e a n a l g e s i c

e f fe c ts o f I F C w h e n c o m p a r e d t o s h a m I F C o n c o l d -

i n d u c e d p a i n i n h e a l t h y v o l u n t e e r s . A c t i v e I F C e l e -

v a t e d p a in t h r e s h o ld w h e n c o m p a r e d t o s h a m I F C

o n l y w h e n t h e s t i m u l a t o r w a s s w i t c h e d o n , a l t h o u g h

t h i s e l e v a t i o n j u s t f a i l e d t o r e a c h s t a t is t i c a l s i g n i fi -

c a n c e ( P = 0 . 0 6 ) . T h e e l e v a t i o n i n p a i n t h r e s h o l d

r a p i d l y r e t u r n e d t o w a r d s t h e p r e - t r e a t m e n t b a s e l i n e

v a l u e s w h e n t h e I F C s t i m u l a t o r w a s s w i t c h e d o f f ,

s u g g e s t i n g th a t t h e r e w a s m i n i m a l p o s t I F C a n a l g e -

s i a u n d e r t h e p r e s e n t e x p e r i m e n t a l c o n d i t i o n s .

C h a n g e s i n p a i n i n t e n s i t y a n d p a i n u n p l e a s a n t n e s s

r a t i n g s w e r e v a r i a b l e t h r o u g h o u t t h e e x p e r i m e n t a n d

t h e r e w e r e n o s i g n i f ic a n t d i ff e r e n c e s i n th e m a g n i -

t u d e o f t h e se r a t in g s b e t w e e n a c t i v e I F C a n d s h a m

I F C . I t w a s , t h e r e f o r e , c o n c l u d e d t h a t I F C c a n e l e -

v a t e e x p e r i m e n t a l p a i n t h r e s h o ld b u t h a d n o e f f e c t

o n t h e p a i n r a t i n g s . T h e m a i n f i n d i n g s o f t h i s s t u d y

w i l l b e d i s c u s s e d b e l o w .

P a i n t h r e s h o l d

T h i s s t u d y f o u n d t h a t I F C i n c r e a s e d i c e p a i n t h r e s h -

o l d w h e n c o m p a r e d t o s h a m I F C , a l t h o u g h t h i s j u s t

f a i l e d t o r e a c h s t a t i s t i c a l s i g n i f i c a n c e ( P = 0 .0 6 ) . T h i s

f i n d i n g s u g g e s t s th a t I F C c a n m o d i f y t h e e x p e r i e n c e

o f p a i n in h u m a n s o v e r a n d a b o v e t h a t p r o d u c e d b y

p l a c e b o . A t p r e s e n t , t h e r e i s l i tt l e o b j e c t i v e e v i d e n c e

t o s u p p o r t t h e a n a l g e s i c e ff e c t s o f I F C a n d s o m e

c o m m e n t a t o r s h a v e , t h e r e f o r e, q u e s t i o n e d t h e e f f e c -

t i v e n e s s o f t h e m o d a l i t y ( L o w R e e d 1 9 9 4 , M a r t i n

1 9 9 4 ) . M o r e o v e r , t h e r e i s c o n f u s i o n o n t h e m o s t

a p p r o p r i a t e w a y o f a d m i n i s t e r i n g I F C . S p e c i f i c

t e x t b o o k s o n I F C o f f e r p r e s c r i p t i v e t r e a t m e n t

r e g i m e s i n c o r p o r a t i n g s p e c i f i c e l e c t r i c a l c h a r a c te r -

i s ti c s o f c u r r e n t d e l i v e r y f o r d i f f e re n t m e d i c a l c o n -

d i t io n s ( D e D o m e n i c o 1 9 87 ; N i k o l o v a 1 9 8 7 ; S a v a g e

1 9 9 2) . H o w e v e r , p h y s i o t h e r a p i s t s c o n t in u e t o

a d m i n i s t e r t h e m o d a l i t y o n a t r i a l a n d e r r o r b a s is i n

c l i n i c a l p r a c t ic e . A r e c e n t q u e s t i o n n a i r e s u r v e y p e r -

f o r m e d b y o u r t e a m f o u n d t h a t p h y s i o t h e r a p i s t s

r e p o r t e d t h at t h e y a d m i n i s t e r e d I F C f o r 1 1 - 2 0 m i n

( 2 7 : 3 5 ) d u r i n g e a c h t r e a t m e n t s e s s i o n a n d t h a t , o n

a v e r a g e , e a c h p a ti e n t r e c e i v e d a c o u r s e o f 1 - 5 I F C

t r e a t m e n t s e s s i o n s ( J o h n s o n T a b a s a m 1 9 9 8 ) . I t

w a s n o t p o s s i b l e to d e t e r m i n e w h e t h e r t h e r a p i s t s

e x p e c t e d t h a t t h e 1 1 - 2 0 m i n I F C t r e a t m e n t w o u l d

p r o v i d e l o n g - l a s t i n g p a i n r e l i e f w h i c h o u t l a s ts s t i m -

u l a t i o n . T h e p r e s e n t s t u d y h a s f o u n d t h a t I F C p r o -

d u c e d a n i n c r e a s e i n p a i n t h r e sh o l d w h i c h w a s r a p i d

i n o n s e t a n d o f f s e t , a n d o n l y o c c u r r e d w h e n t h e

s t i m u l a t o r w a s s w i t c h e d o n . A s p o s t - s t i m u l a t i o n

e f f e ct s w e r e m i n i m a l i t i s s u g g e s t e d t h a t t h e r e w i l l

b e l i m i t e d a n a l g e s i c b e n e f it o n c e t h e s t i m u l a t o r i s

s w i t c h e d o f f . T h e r e f o r e , i t i s p o s s i b l e t h a t p a t i e n t s

w h o a r e m a n a g e d u s i n g I F C s t i m u l a t i o n l a s t i n g

1 1 - 2 0 r a i n a r e re c e i v i n g n o b e n e f i t f r o m I F C w h e n

t h e y l e a v e t h e c l i n i c . I F C m a y b e m o r e e f f e c t i v e l y

e m p l o y e d t o r e l i e v e p a i n i f p a ti e n t s w e r e a l l o w e d t o

Elec t ro therap y for pa in re l ie f i does i t work? 2

s e l f - a d m i n i s t e r I F C a s a n d w h e n r e q u i r e d a t h o m e

( i n a s i m i l a r m a n n e r t o T E N S ) . T h i s w o u l d i n c r e a s e

t h e t r e a tm e n t t i m e a n d , s u b s e q u e n t l y , t h e a m o u n t o f

p a i n r e l i e f o b t a i n e d b y t h e p a t i e n t . K e y t e x t s o n t h e

c l i n i c a l u s e o f I F C s u g g e s t t h a t I F C s h o u l d b e d e l i v -

e r e d f o r n o m o r e t h a n 3 0 r a i n a t a t im e a n d t h e p r a c -

t i c e o f d e l i v e r i n g I F C f o r s h o r t p e r i o d s o f t i m e

m e r i t s f u r t h e r c o m m e n t a s i t h i g h l i g h t s t h e d a n g e r

o f n o n - e v i d e n c e - b a s e d p r a c t i c e i n p h y s i o t h e r a p y .

T h e r e i s c u r r e n t l y n o o b j e c t i v e e v i d e n c e t o s u p p o r t

t h e u s e o f I F C f o r a s h o r t p e r i o d o f t i m e ( u n d e r 3 0

r a i n ) , a l th o u g h i t h a s b e e n s u g g e s t e d t h a t c o n t i n u o u s

I F C s t i m u l a t i o n m a y f a t i g u e p a t i e n t s ( D e D o m e n i c o

1 9 8 7, N i k o l o v a 1 9 8 7 , S a v a g e 1 9 9 2 ). H o w e v e r , c l i n -

i c a l st u d i e s o n T E N S h a v e s h o w n t h a t p a t i e n t s w h o

d e l i v e r T E N S c a n u s e T E N S f o r m a n y h o u r s w i t h -

o u t a n y o b s e r v a b l e f a t i g u e ( J o h n s o n e t a l . 1 9 9 1 ).

T h e f i n d i n g s o f s t u d ie s o n c o n v e n t i o n a l T E N S h a v e

a l s o s h o w n t h a t a n a l g e s i a o c c u r s d u r i n g r a t h e r t h a n

a f t e r t r e a t m e n t ( J o h n s o n e t a l . 1 9 9 1 ) . P a t i e n t s w h o

s e l f a d m i n i s t e r T E N S f o r c h r o n i c p a i n d e l i v e r

T E N S t h r o u g h o u t t h e d a y , a s t h e y f i n d t h a t t h e

g r e a t e s t a n a l g e s i a o c c u r s w h e n t h e T E N S d e v i c e i s

s w i t c h e d o n ( J o h n s o n e t a l . 1 9 9 1 ) . T h e f i n d i n g s o f

t h e p r e s e n t s t u d y s u g g e s t s I F C a n a l g e s i a m a y h a v e a

s i m i l a r re s p o n s e p r o f i l e t o t h a t o f T E N S a n d , t h e r e -

f o r e , g r e a t e r th e r a p e u t i c b e n e f i t f r o m t h i s m o d a l i t y

m a y b e g a i n e d b y a d m i n i s t e r i n g i t i n a s i m i l a r

m a n n e r t o T E N S .

I t is i m p o r t a n t t o c o n s i d e r t h a t t h e I F C t r e a t m e n t

p r o t o c o ls e m p l o y e d b y p h y s i o t h er a p i s ts m a y h a v e

b e e n d e v e l o p e d t o s u i t t h e t h e r a p i s t ra t h e r t h a n t h e

n e e d s o f t h e p a t i e n t. T h e m a j o r i t y o f I F C d e v i c e s i n

u s e a r e l a r g e , n o n - p o r t a b l e a n d e x p e n s i v e , a n d a r e

l o c a t e d i n h o s p i t a l d e p a r t m c n t s o r t h e r a p i s t s c l i n i c s .

P a t i e n t s , t h e r e f o r e , n e e d t o a t t e n d t h e c l i n i c t o

o b t a i n t r e a t m e n t . T h e r a p i s t s m a y b e u n a b l e t o

a d m i n i s t e r I F C f o r m o r e t h a n 2 0 m i n , a s t h e i r c l i n i-

c a l r o t a d i c t a t e s a t i m e - l i m i t e d c o n s u l t a t i o n . A s e r i e s

o f s u b s e q u e n t t r e a t m e n t s e s s i o n s m a y b e i n d i c a t e d

t o o v e r c o m e t h i s p r o b l e m , h o w e v e r , t h i s d o e s n o t

p r o v i d e a d e q u a t e p a i n r e l i e f f o r t h e p a t i e n t .

A n e c d o t a l r e p o r t s s u g g e s t t h a t 1 F C a n a l g e s i a i s

c u m u l a t i v e w i t h s u c c e s s i v e t r e a t m e n t s e s s i o n s :

H o w e v e r , i t i s l i k e l y t h a t o t h e r f a c t o r s , s u c h a s n a t -

u r a l f l u c t u a ti o n s i n t h e h e a l i n g o f t h e c o n d i t i o n , m a y

a c c o u n t f o r t h e o b s e r v a t i o n s . A t p r e s e n t , t h e r e i s

i n s u f f i c i e n t e v i d e n c e t o s u p p o r t c l a i m s t h a t a s e r ie s

o f I F C t r e a t m e n t s w i l l p r o d u c e c u m u l a t i v e e f f e c ts .

I f I F C a n a l g e s i a i s s i m i l a r i n n a t u r e t o e l e c t r o t h e r -

a p y ' s , s uc h a s T E N S t h e n p a t i e n t s s h o u l d b e a l l o w e d

t o u s e t h e m o d a l i t y w h e n n e e d e d ( e . g . w h e n t h e y a r e

i n p a i n ) . T h e d e v e l o p m e n t o f c h e a p e r p o r t a b l e I F C

d e v i c e s m a y a l l o w c l i n i c s t o l o a n I F C d e v i c e s t o

p a t i e n t s w h o w i l l b e a b l e t o s e l f - a d m i n i s t e l t r e a t m e n t

a s a n d w h e n i t i s r e q u i r e d . T h i s a p p r o a c h h a s b e e n

e m p l o y e d b y m a n y P a i n C l i n i c s s u c c e s sf u l l y f o r t h e

m a n a g e m e n t o f p a i n b y T E N S . H o w e v e r , i t m a y b e

m o r e a p p r o p r i a t e to i n v e s t in T E N S r a t h e r t ha n I F C ,

a s T E N S i s c h e a p e r a n d e a s i e r f o r b o t h t h e t h e r a p i s t

a n d t h e p a t i e n t t o a d m i n i s t e r . T h e r e a r e h y p o t h e t i c a l


9/11

l in i c a l E f fe c t i v e n e s s i n N u r s i n g

d i f f ere n c e s in th e m e c h a n i s m o f a c t io n o f IF C a g a in s t

T E N S , a l th o u g h e v id e n c e w h ic h h a s e x a m in e d th e

ana lges ic e ffec ts and c l in ica l e ffec t iveness o f the two

m o d a l i t i e s i s n o t a v a i l a b le a t p re s e n t (D e D o m e n ic o

1 9 8 7 , L o w R e e d 1 9 94 ). A p re l im in a ry b u t a s y e t

u n p u b l i s h e d s tu d y b y o u r g ro u p h a s fo u n d th a t ,

a l th o u g h IF C a n d T E N S s ig n i fi c a n t ly in c re as e p a in

th resho ld to exper imenta l pa in , the re a re no d iffe r-

e n c e s in th e m a g n i tu d e o f t h i s r e sp o n s e b e tw e e n

TENS and IFC (Tabasam e t a l . 1998) . Furthe r work

in th is a rea shou ld compare the ana lges ic e ffec ts ,

m e c h a n i s m o f a c t io n a n d c l in i c a l e f f e c t iv e n e s s o f

T E N S a n d IF C . T h i s i n fo rm a t io n w i l l h e lp th era p i st s

to d e te rm in e th e ci r c u m s ta n c e s w h e re T E N S a n d IF C

should be indicated separately.

P a i n i n t e n s i t y a n d p a i n u n p l e a s a n tn e s s

r a t i n g

T h is s tu d y fo u n d n o d i f f e re n c e s b e tw e e n IF C a n d

s h a m fo r th e p e rc e n ta g e c h a n g e in p a in in t e n s i ty

and unp leasan tness ra t ings , and th is sugges ts tha t

IF C d id n o t m o d i fy th e s e l f re p o r t o f p a in u n d e r th e

p re s e n t e x p e r im e n ta l c o n d i t io n s . T h i s f in d in g i s

c o n s i s t e n t w i th o u r p re v io u s s tu d ies o n T E N S u s in g

th e s a m e t e c h n iq u e s ( J o h n s o n e t a l. 1 9 9 2 ). D e s p i t e

th e l a c k o f d i f f e re n c e s b e tw e e n th e t r e a tm e n t

g ro u p s , t h e re w a s a s ig n i f i c a n t i n c re a s e in p a in

in t e n s i ty fo r b o th IF C a n d s h a m g ro u p s w h e n th e

t r e a tm e n t in t e rv e n t io n w a s t e rm in a te d . T h i s

in c re a s e in p a in in t e n s i ty r a t in g m a y b e a t t r ib u ted to

a pos t- t rea tment inc rease in pa in in tens i ty , a l though

th e m a g n i tu d e o f t h is r e b o u n d e f fe c t fo r IF C m a y b e

n o g re a t e r t h a n th a t o f s h a m . S im i l a r r e b o u n d

e f fe c t s h a v e b e e n o b s e rv e d in th e c l in i c w h e n

p a t i e n t s r e p o r t t h a t p a in in t e n s i ty in c re a s e s w h e n

T E N S i s s w i t c h e d o f f a n d th e ra p is t s s o m e t im e s u s e

th i s t o c o n v in c e p a t ie n t s t h a t T E N S i s r e d u c in g th e

m a g n i tu d e o f p a in. T h e a u th o r s w i s h to r e m a in c a u -

t io u s a b o u t t h e s e f in d in g s a s th e y h a v e n o t b e e n

re p ro d u c ib le in o u r p re v io u s s tu d ie s u s in g a c t iv e

a n d s h a m e le c t ro th e ra p e u t i c in t e rv e n t io n s .

T h e f in d in g s o f th i s s tu d y a re in a g re e m e n t w i th

a p re v io u s s tu d y o n c o ld - in d u c e d p a in b y

S te p h e n s o n a n d J o h n s o n (1 9 9 5 ) . T h i s s tu d y , h o w -

e v e r , f a i le d to in c lu d e a p l a c e b o c o n t ro l , a n d i t w a s

no t poss ib le to a t t r ibu te the e ffec ts on pa in th resho ld

o b s e rv e d s o le ly to t r e a tm e n t w i th IF C .

T h e f in d in g s o f t h i s s tu d y d i s a g re e w i th p re v io u s

s tu d ie s b y S c o t t a n d P u rv e s (1 9 9 1 ) a n d T a y lo r e t al .

(1 9 8 7 ) . S c o t t a n d P u rv e s (1 9 9 1 ) in v e s t ig a t e d th e

a n a lg e s i c e f f e c ts o f IF C u s in g e x p e r im e n ta l p a in

a n d , a l th o u g h th e i r s tu d y w a s p l a c e b o c o n t ro l l e d ,

th e s e in v e s t ig a to r s e m p lo y e d a d i f f e re n t e x p e r im e n -

t a l p a in m o d e l t o th e o n e e m p lo y e d b y o u r s e lv e s

( i s c h a e m ic p a in t e s t ) . T h i s m a y h a v e a c c o u n te d fo r

th e d i f f e re n c e s o b s e rv e d b e tw e e n th e tw o s tu d ie s .

T h e f in d in g s o f o u r s tu d y a l s o d i s ag re e w i th c l in i c a l

s tu d ie s b y T a y lo r e t a l. (1 9 8 7 ) w h o in v e s t ig a t e d th e

a n a lg e s i c e f f e c t s o f IF C o n r e c u r re n t j a w p a in .

A g a in , a l th o u g h th e s tu d y w a s p l a c e b o c o n t ro l l e d , it

w a s a c l in i c a l s tu d y p e r fo rm e d o n p a t i e n ts s u f fe r in g

f ro m c l in i c a l p a in . I t i s im p o r t a n t t o a c k n o w le d g e

th e p re s e n c e o f a d d i t io n a l p s y c h o s o c ia l a n d b e h a v -

io u ra l f a c to r s w h ic h w o u ld m a rk e d ly in f lu e n c e th e

re s p o n s e o f p a t i e n t s i n th e c l in i c . T h i s m a y h a v e

a c c o u n te d fo r t h e d i f f e re n c e s o b s e rv e d b e tw e e n

these two s tud ies .

O N L U S I O N

In c o n c lu s io n , t h i s s tu d y h a s s h o w n th a t IF C c a n e l e -

va te exper imenta l pa in th resho ld , bu t had no e ffec ts

o n p a in r a t in g s ; h o w e v e r , o n e s h o u ld b e c a u t io u s

w h e n e x t r a p o la tin g th e f in d in g s o f l a b o ra to ry -b a s ed

s tud ies us ing hea l thy sub jec ts to pa t ien ts su ffe r ing

c l in ica l pa in . Neverthe less , th is s tudy h igh l igh ts the

im p o r t a n c e in p ro v id in g e x p e r im e n ta l e v id e n c e f ro m

both bas ic sc iences and c l in ica l p rac t ice to support

the t rea tment approaches by c l in ic ians . Th is is e spe-

c i a l ly a p p ro p r i a t e to n u r s in g w h e re p ra c t i c e c a n

s t e m f ro m t r e a tm e n t p re fe ren c e s w h ic h a re b a se d o n

a n e c d o ta l e v id e n c e .

l i n i c a l i m p l i c a t i o n s a n d f u t u r e

d i r e c t i o n s f o r r e s e a r c h

T h e c l in i c a l im p l i c a t io n s fo r t h i s r e s e a rc h a re th a t

IF C m a y b e u s e fu l c l in i c a l ly fo r p a in r e l i e f a s t h i s

s tu d y h a s s h o w n th a t it c a n e l e v a te p a in th re s h o ld in

h e a l th y v o lu n te e r s . In a n e a r l ie r s tu d y b y o u r s e lv e s

( J o h n s o n T a b a s a m 1 9 9 8 ) i t w a s s h o w n th a t IF C i s

a d m in i s t e re d b y th e ra pi s t s 3 x 2 0 m in t r e a tm e n t s

p e r w e e k in th e c l in i c , h o w e v e r , i t m a y b e m o re

a p p ro p r i a t e to im p le m e n t a l o n g e r t r e a tm e n t t im e a s

th i s s tu d y h a s in d ic a t e d m in im a l p o s t - t r e a tm e n t

a n a lg e s i a . T h i s s tu d y h a s s h o w n th a t l a b o ra to ry -

based s tud ies a re va luab le in the in i t ia l eva lua t ion o f

the ana lges ic e ffec ts o f an e lec tro the rapy .

O v e r a ll s u m m a r y

T h is p a p e r h a s h ig h l ig h te d th e im p o r t a n c e o f l a b o -

ra to ry -b a s e d s tu d ie s w h ic h s h o u ld b e e x te n d e d in to

c l in ic a l r a n d o m iz e d -c o n t ro l l e d t r ia l s t o c o n f i rm th e

c l in i ca l e f f e c t iv e n e s s o f IF C fo r t h e m a n a g e m e n t o f

pa in . At p resen t , the re is l i t t le ob jec t ive ev idence in

s u p p o r t o f IF C . T h e re i s a l s o a n e e d to c o m p a re th e

e f fe c t s o f IF C w i th o th e r c h e a p e r , m o re e f f i c i e n t

e l e c t ro th e ra p ie s, s u c h a s T E N S , w h ic h m a y h a v e

c o s t e f f e c t iv e n e s s im p l i c a t io n s fo r t h e N H S a n d

m a y a l s o in d ic a te th e a d m in i s t ra t io n o f IF C a n d

T E N S fo r d i f f e re n t c l in ic a l c o n d i t io n s . I t i s c ru c ia l

tha t c l in ic ians , e spec ia l ly when cons ide r ing t rea t-

m e n t r e g im e s fo r p a t i e n t s , i n t e g ra t e k n o w le d g e

g a in e d th ro u g h th e i r c l in ic a l e x p e r i e n c e w i th o b je c -

t iv e e v id e n c e f r o m th e a v a i l a b le l i t e r atu re in o rd e r

to a d v a n c e e x i s t in g c l in i c a l p ra c t i c e . T h e im p o r -

t a n c e o f r e in fo rc in g th e im p le m e n ta t io n o f g o o d

e v id e n c e -b a s e d p ra c t i c e b y h e a l th c a re p ro fe s s io n -

a l s c a n n o t b e o v e r e m p h a s iz e d .


10/11

C K N O W L E D G E M E N T S

T h i s w o r k i s f u n d e d b y a n N H S E x e c u t i v e P h D s t u d e n t s h i p

g r a n t n o . R A C 7 3 3 .

RE FERENCE S

B a x t e r G D , B e l l A J , A l i e n A M , R a v e y J 1 9 9 1 L o w l e v e l

l a se r t he r a py : c u r r e n t c l i n i c a l p r a c t i c e in N o r t he r n

I r el a n d . P h y s i o th e r a p y 7 7 : 1 7 1 - 1 7 8

C a r r o l l D , M o o r e A , T r a m e r M , M c Q u a y H 1 9 97

T r a nsc n t a ne ou s e l e c t ri c a l ne r ve s t imu l a t i on doe s no t

r e l i e ve in l a bour pa i n : up da t e d sy s t e ma t i c r e v i e w .

C o n t e m p o r a r y R e v i e w s i n O b s t e t r ic s a n d G y n e c o l o g y ,

S e p t e m b e r 1 9 97 1 9 5 - 2 0 5

C a r r o ll D , T r a m e r M , M c Q u a y H , N y e B , M o o r e A 1 9 9 6

R a n d o m i z a t io n i s i m p o r t a n t in s t u d ie s w i t h p a i n

ou t c om e s : sys t e ma t i c r e v i e w o f t r a nsc u t a ne ous e l e c t r i c a l

ne r ve s t i mu l a t i on i n a c u t e pos t ope r a t i ve pa i n . B r i t i sh

J o u r n a l o f A n a e s t h e s i a 7 7 : 7 9 8 - 8 0 3

C a r r o ll D , T r a m e r M , M c Q u a y H , N y e B , M o o r e A 1 9 9 7

T r a nsc u t a ne ous e l e c t r i c a l ne r ve s t i mu l a t i on i n l a bour

pa i n : a sys t e ma t i c r e v i e w . Br i t i sh Jou r na l o f O bs t e t r i c s

a n d G y n a e c o l o g y 1 0 4 : 1 6 9 - 1 7 5

D e D o m e n i c o G 1 9 87 N e w d i m e n s i o n s i n i n t er f e re n t i al

t he r a py . A t he o r e t i c a l a nd c l i n i c a l gu i de . L i n f i e l d : Re i d

M e di c a l Books , 1987

D e y o R , W a l s h N , S c h o e n f e l d L , R a m a m u r t h y S 1 9 90 C a n

t r ia l s o f p h y s i c a l t re a t m e n t s b e b l i n d e d ? T h e e x a m p l e o f

t r a nsc n t a ne ou s e l e c tr i c a l ne r ve s t i m u l a t i on f o r c h r on i c

p a i n [ s e e c o m m e n t s ] . A m e r i c a n J o u r n a l o f P h y s i c a l

M e d i c i n e a n d R e h a b i li t a ti o n 6 9 : 6 - 1 0

E i g l e r E 1 9 7 9 S u c c e s s a c h i e v e d b y t r e a tm e n t w i t h

i n t e f f e r e n t i a l c u r r e n t on pa t i e n t s w i t h e p i c o ndy l i t i s

h u m e r i . 8 4 t h C o n g r e s s o f t h e G e r m a n S o c i e t y f o r

P h y s i c a l M e d i c i n e a n d R e h a b i l it a ti o n , H a n o v e r W e s t

G e r m a n y , O c t 1 2 - 1 4

E va ns F 1985 E xpe c t a nc y , t he r a pe u t i c i n s t ruc t i ons a nd t he

p l a c e bo r e sponse . I n : Whi t e L , T ur sky B , S c hw a r t z G

( e ds ) P l a c e bo t he o r y , re se a r c h a nd me c h a n i sm s . N e w

Y or k: G u i l f o r d P r e s s , 215- 228

G a dsb y G , F l ow e r de w M 1997 N e r ve s t imu l a t i on f o r l ow

ba c k pa i n - a r e v i ew . N ur s i ng S t a n da r ds 11 : 32 - 33

G e or g i ou A 1996 H i gh qua l i t y p l a c e bos shou l d be use d . BM J

3 1 3 : 1 0 0 9

G r a c e ly R 1 9 89 M e t h o d s o f t e s t in g p a i n m e c h a n i s m s in

nor ma l ma n . l n : Wa l l P D , M e l z a c k R ( e ds ) T e x t book o f

pa i n . E d i nbur gh : Chur c h i l l L i v i ngs t one , 257- 268

G r a c e l y RH 1994 S t ud i e s o f pa i n i n no r m a l ma n . I n :

M e l z a c k P D W R ( e d. ) T e x tb o o k o f p a i n . E d i n b u r g h :

C h u r c h i ll L i v i n g s t o n e , 3 1 5 - 3 3 6

I de L , P a r t r i dge CJ 1989 S ur ve y o f e l e c t ro t he r a py e qu i pm e n t

i n phys i o t h e r a py de pa r t me n t s a nd p r i va t e p r a c ti c e .

C e n t r e t b r P h y s i o t h e r a p y R e s e a r c h K i n g s C o l l e g e

L o n d o n

Ja nde l S c i e n t i f i c G m bH , S i gma S t a t s t a t i s t ic a l so f t w a r e .

U se r s ma nua l , 1994

John son M 1 1997 T r a nsc u t a ne ous e l e c t r i c a l ne r ve s t i mu l a t i on

( T E N S ) i n t h e m a n a g e m e n t o f l ab o u r p a i n : t h e

e x p e r i e n c e o f o v e r t e n t h o u s a n d w o m e n . B r i t i s h J o u rn a l

o f M id w i fe r y 5 : 4 0 0 4 0 5

J o h n s o n M , A s h t o n C , B o u s f i e l d D , T h o m p s o n J W 1 9 89

A na l g e s i c e f f e c t s o f d i f f e r e n t f r e que nc i e s o f

t r a nsc u t a ne ous e l e c t r i c a l ne r ve s t i mu l a t i on on c o l d -

i n d u c e d p a i n i n n o r m a l s u b j e c ts . P a in 3 9 : 2 3 1 - 2 3 6

J o h n s o n M I , A s h t o n C H , B o u s f i e l d D R , T h o m p s o n J W 1 9 91

A na l g e s i c e f f e c t s o f d i f f e r e n t pu l s e pa t t e r ns o f

t r a nsc n t a ne ous e l e c t r i c a l ne r ve s t i mu l a t i on on c o l d -

i nduc e d pa i n i n no r ma l sub j e c t s . J P syc hoso m Re s 35 :

313- 321

J o h n s o n M I , A s h t o n C H , T h o m p s o n J W 1 9 9 1 A n i n - d e p t h

s t udy o f l ong- t e r m use r s o f t r a nsc u t a ne o us e l e c t r i c a l

E l e c t r o t h e r a p y f o r p a i n r e li e f : d o e s i t w o r k ? 9 . I

ne r ve s t i mu l a t i on ( T E N S ) . I mp l i c a t i ons f o r c l i n i c a l u se

o f T E N S . P a i n 4 4 : 2 2 1 - 2 2 9

J o h n s o n M I , A s h t o n C H , T h o m p s o n J W 1 99 1 T h e

c o n s i s t e n c y o f p u l s e f r e q u e n c i e s a n d p u l s e p a t t e r n s o f

t r a nsc u t a ne ou s e l e c t ri c a l ne r ve s t i mu l a t i on (T E N S ) use d

b y c h r o n i c p a i n p a t i en t s . P a in 4 4 : 2 3 1 - 2 3 4

J o h n s o n M I , A s h t o n C H , T h o m p s o n J W 1 9 92 A n a l g e s i c

e f f ec t s o f A c u p u n c tu r e L i k e T E N S o n c o l d p r e s s o r p a i n i n

n o r m a l s u b j e c ts . E u r o p e an J o u r n a l o f P a i n 1 3 : 1 0 1 - 1 0 8

J o h n s o n M , T a b a s a m G 1 9 98 A q u e s t i o n n a i r e su r v e y o n t h e

c l i n i c a l u se o f i n t e r f e r e n t i a l c u r r e n t s ( I F C) by

p h y s i o t h e r a p is t s . T h e P a i n S o c i e t y o f G r e a t B r i t a in

A nnua l Conf e r e nc e ( a bs t r a c t s ) , L e i c e s t e r

J o h n s o n M , W i l s o n H 1 9 97 T h e a n a l g e s i c e f f ec t s o f 6 ^ 6 a n d

1] 1 sw i ng pa t t e r ns o f i n t e r f e r e n t i a l c u r r e n t s ( I F C) on

c o l d - i n d u c e d p a i n i n h e a l t h y s u b j e c t s : a p r e l i m i n a r y

s t udy . P hys i o t he r a py 83 : 461- - 467

K i e n l e G , K i e n e H 1998 T he p l a c be o e f f e c t : a s c i e n t i f i c

c r it i qu e . C o m p l e m e n t a r y T h e ra p i e s i n M e d i c i n e 6 : 1 4 - 2 4

L i n d s a y D M , D e a r n e s s J , R i c h a r d s o n C e t a l. 1 9 9 0 A s u r v e y

o f e l e c t r o m o d a l i t y u s a g e i n p r i v a t e p h y s i o t h e r a p y

pr a c t i c e s . A us t r a l i a n Jour na l o f P hys i o t h e r a py 36 :

2 4 9 - 2 5 6

L o w J , R e e d A 1 9 94 E l e c t ro t h e r a p y e x p l a in e d p r i n c i p le s a n d

p r a c ti c e . O x f o r d : B u t t e r w o r t h - H e i n e m a n n L t d ,

M a r t i n D 1994 I n t e r f e r e n t i a l f o r pa i n c on t r o l . I n : K i t c he n S ,

Ba z i n S ( e ds ) C l a y t on s e l e c t r o t he r a py 10E . L ondo n :

W B S a u n d e r s C o m p a n y L t d , 3 0 6 -- 31 5

M c Q u a y H , M o o r e A 1 9 96 P l a c e b o m a n i a : p l a c e b o s a r e

e s s e n t ia l w h e n e x t e n t a n d v a r i a b i li t y o f p l a c e b o

r e s p o n se a re u n k n o w n B M J 3 1 3 : 1 0 0 8

M c Q u a y H , M o o r e A 1 9 98 A n e v i d e n c e - b a s e d r e s o u r c e fo r

pa i n r e l i e f. O xf o r d : O x f o r d U n i ve r s i t y P r e s s ,

N e l so n B 1981 I n t e r f e r e n t i a l t he r a py . A us t r a l i a n Jour na l o f

P h y s i o th e r ap y 2 7 : 5 3 - 5 6

N i k o l o v a L 1 9 67 V e r g l e ic h e n d e u te r s u c h u n g e n u b e r

t he r a pe u t i s c he e r f o l ge de r i n t e r f e r e nz t he r a p i e und

a n d e r e r m e t h o d e n b e i a r t h r o s is d e f o r m a n s .

P h y s i k a l i s c h e M e d i z i n u n d R e h a b i li t a ti o n 8 : 6 6 - 6 9

N i ko l ov a L 1987 T r e a t me n t w i t h i n t e r f e r e n t i a l c u r r e n t .

E d i nbur gh : Chur c h i l l L i v i ngs t one

P a x l on S 1980 C l i n i c a l u se s o f T E N S . A su r ve y o f phys i c a l

t h e ra p i s ts . P h y s i c a l T h e r a p y 6 0 : 3 8 M 4

P op e G , M oc k e t t S , Wr i gh t J 1995 A su r ve y o f

e l e c t r o t he r a pe u t i c moda l i t i e s : ow ne r sh i p a nd us e i n t he

N H S i n E n g l a n d . P h y s i o t h e r a p y 8 1 : 8 2 - 9 1

P osn e r J , T e l e ke s A , Cr ow l e y D , P h i l l i p son R , P e e k A 1985

E f f e c t s o f an o p i a t e o n c o l d - i n d u c e d p a i n a n d t h e C N S

i n h e a l t h y v o l u n te e r s . P ai n 2 3 : 7 3 - 8 2

R e e v e J , M e n o n D , C o r a b i a n P 1 9 9 6 T r a n s c u t an e o u s

e l e c t r i c a l ne r ve s t i mu l a t i on ( T E N S ) : a t e c hno l ogy

a s se s sm e n t . In t e r na t i ona l Jou r na l o f T e c hno l ogy

A s s e s s m e n t i n H e a l th C a r e 1 2 : 2 9 9 - 3 2 4

Rob i nson A J , S nyde r - M a c k l e r L 1988 C l i n i c a l a pp l i c a t i on o f

e l e c t r o t he r a pe u t i c moda l i t i e s . P hys i c a l T he r a py 68 :

1 2 3 5 - 1 2 3 8

S a va ge B 1992 I n t e r f e re n t i a l t he r a py . L ond on : Wol f e

P u b l i s h i n g L t d

S c o t t S M , P u r v e s C E 1 9 91 T h e e f f e c t o f i n t e r fe r e n t i a l

t h e r a p y i n t h e r e l i e f o f e x p e r i m e n t a l l y i n d u c e d p a i n ;

a p i l o t s tu d y . P r o c e e d i n g s o f t h e 1 t h I n t e r n a t i o n a l

C o n g r e s s o f W o r l d C o n f e d e r a t io n o f P h y s i c a l

T h e r a p y

S t e p h e n s o n R , J o h n s o n M 1 9 95 T h e a n a l g e s i c ef f e c ts o f

i n t e r f e r e n t i a l t he r a py on c o l d - i nd uc e d pa i n i n he a l t hy

s u b j e c t s A p r e l i m i n a r y r e p o rt . P h y s i o t h e r a p y T h e o r y

a nd P r a c t i c e 11 : 89 - 95

T a b a s am G , J o h n s o n M I , T m j a J 1 9 98 A d o u b l e b l i n d

p l a c e bo c on t r o l l e d i nve s t i ga t i on i n t o t he a na l ge s i c

e f f e c t s o f i n t c r f e r e n t i a l c u r r e n t s ( I F C) a n d

t r a nsc u t a ne ou s e l e c tr i c a l ne r ve s t i mu l a t i on ( T E N S ) on

c o l d i nduc e d pa i n i n he a l t hy sub j e c t s . T he P a i n S oc i e t y

o f G r e a t B r i t a in A nnua l Co n l e r e nc e , L e i c e s t e r


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4 l in i c a l E f f e c t i v e n e s s i n N u r s i n g

T a b a s a m G , J o h n s o n M I 1 9 97 T h e a n a l g e s i c ef f e c ts o f

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sub j e c t s . P r e l i mi na r y f i nd i ngs . T he P a i n S oc i e t y o f

G r e a t B r i t a in A n n u a l C o n f e r e n c e

T a b a s o n G , J o h n s o n M I 1 9 96 S e x d i f f e r en c e s i n t h e r e s p o n s e

t o p l a c e bo t r a nsc u t a n e ous e l e c t r i c a l ne r ve s t i mu l a t i on

T E N S ) i n h e a l t h y s u b j e c ts . V I I It h W o r l d C o n g r e s s o n

P a i n , V a n c o u v e r

T a y l o r K , N e w t o n R , P e r s o n i u s W , B u s h F 1 9 87 E f f e c t s o f

i n t e r f e r e n t i a l c u r r e n t s t i mu l a t i on f o r t he t r e a t me n t o f

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T h e C h a r t e r e d S o c i e t y o f P h y s i o t h e r a p y . S t a n d a r d s f o r t h e

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Wa l l P 1994 T h e p l a c e bo a nd t he p l a c e bo r e sponse . I n : Wa l l

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W o l f f B B , K a n t o r T G e t a l . 1 9 6 6 R e s p o n s e o f e x p e r im e n t a l

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