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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
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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
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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 .
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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
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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
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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
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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 .
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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
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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 .
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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
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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
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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
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