VALI DATI ON OF THE RATI O SCALE OF THE DI FFERENTS TYPES OF PAI N
Priscilla Hort ense1 Ér ika Zam br ano2 Fát im a Aparecida Em m Faleiros Sousa3
Hort ense P, Zam brano E, Sousa FAEF. Validat ion of t he rat io scale of t he different s t ypes of pain. Rev Lat ino- am Enfer m agem 2008 j ulho- agost o; 16( 4) : 720- 6 .
The m ain aim was t o validat e t he rat io scale derived from t he non- m et ric cont inuum of t he int ensit y of t he different types of pain using cross- m odality m atching. Magnitude estim ation m ethod and cross- m odality m atching were used wit h perceived line lengt hs. The st udy was form ed by 30 out pat ient s from various specialt y clinics, 30 physicians and 90 nurses. The results were: Cancer Pain, Myocardium I nfarct Pain, Renal Colic, Burn I nj ury Pain, and Childbirth Labor Pain were regarded as the pains of greater intensity; the rank order of pain intensity for t he differ ent t y pes of pain, com par ing t he differ ent psy chophy sical m et hods used r esult ed in lev els of significant agreem ent. The conclusion was that the relation between the m agnitude estim ates and cross m odality m atching estim ates of the line- lengths is a power function, and the scale for the different types of pain is valid, st able and consist ent .
DESCRI PTORS: pain m easurem ent ; psychophysics; pain
VALI DACI ÓN DE LA ESCALA DE RAZÓN DE LOS DI FERENTES TI POS DE DOLOR
El obj et ivo general fue validar la escala de razón derivada para el cont inuo no m ét rico de int ensidad de los diferent es t ipos de dolor por m edio del m ét odo de em parej am ient o int erm odal. Fueron ut ilizados los m ét odos de estim ación de m agnitud y de em parej am iento interm odal con la m odalidad de respuesta en largo de líneas. Part iciparon 30 pacient es de am bulat orio de diferent es clínicas, 30 m édicos y 30 enferm eros. Los result ados m ost raron: Dolor en el Cáncer, Dolor por I nfart o del Miocardio, Dolor por Cólico Renal, Dolor por Quem adura y Dolor en el Parto; que fueron considerados los tipos de dolor de m ayor intensidad; el orden de las posiciones de la intensidad de los diferentes tipos de dolor, cuando se com para los diferentes m étodos psicofísicos utilizados, resultó en niveles de concordancia significativa. Concluim os que la relación entre las estim ativas de m agnitudes y las est im at ivas de largo de líneas es una función exponencial y la escala de los diferent es t ipos de dolor es válida, est able y consist ent e.
DESCRI PTORES: m edición del dolor; psicofísica; dolor
VALI DAÇÃO DA ESCALA DE RAZÃO DOS DI FERENTES TI POS DE DOR
O obj etivo geral foi validar a escala de razão derivada para o contínuo não m étrico de intensidade dos diferentes t ipos de dor, por m eio do m ét odo de em parelham ent o int erm odal. Foram ut ilizados os m ét odos de est im ação de m agnit ude e de em parelham ent o int erm odal com a m odalidade de respost a em com prim ent o de linhas. Part iciparam 30 pacient es am bulat oriais de diferent es clínicas, 30 m édicos e 30 enferm eiros. Os result ados m ost raram dor no câncer, dor por infart o do m iocárdio, dor por cólica renal, dor por queim adura e dor no par t o, consider ados os t ipos de dor de m aior int ensidade; as or denações de posições da int ensidade dos difer ent es t ipos de dor , com par ando os difer ent es m ét odos psicofísicos ut ilizados, r esult ar am em níveis de concordância significat ivos. Conclui- se que a relação ent re as est im at ivas de m agnit udes e as est im at ivas de com prim ent o de linhas é um a função de pot ência e a escala dos diferent es t ipos de dor é válida, est ável e consist ent e.
DESCRI TORES: m edição da dor; psicofísica; dor
1 Ph.D. in Nursing, Facult y, e- m ail: prihrt @yahoo.com .br; 2 M.Sc. in Nursing, Facult y, e- m ail: ez5871@yahoo.com .br. Araraquara Universit y Cent er, UNI ARA,
Brasil; 3 Full Professor, Universit y of Sao Paulo at Ribeirao Pret o College of Nursing, WHO Collaborat ing Cent er for Nursing Research Developm ent , Brazil,
e-m ail: faleiros@eerp.usp.br.
I NTRODUCTI ON
P
ain is a problem t hat m ust be faced by t he healt h t eam ; it is a sym pt om t hat can have acut e orchr onic char act er ist ics and m ay w or sen healt h st at e
if it is n ot adequ at ely r eliev ed. How ev er, as it is a
com p lex an d su b j ect iv e p h en om en a, on e m ay say
t h at in div idu als in pain m u st be t r eat ed r espect in g
t heir t ot alit y and indiv idualit y.
We r ecog n ize t h e im p or t an ce of assessin g
p ai n , i t s m an ag em en t , an d co n t r o l , t h e Am er i can
Societ y of Pain est ablished t his sym pt om as t he “ fift h
v it al sign ”, em ph asizin g t h at pain assessm en t is as
im por t ant as t he assessm ent of t he ot her four v it al
sig n s an d t h at h ealt h p r of ession als n eed t o r ecor d
t his phenom ena. Thus, it is necessar y t o use scales
t o pr odu ce m easu r e par am et er s an d, con sequ en t ly,
an adequat e pain cont r ol.
S t u d i e s o n p a i n f u l p h e n o m e n o n a r e
i n cr e a si n g l y f o cu si n g o n t h e co m p l e x i t y o f t h e i r
dim en sion s. Appr oach in g ot h er aspect s r at h er t h an
t he sensit ive ones m akes it easier t o underst and t his
p h e n o m e n o n . B r o a d a n d c o m p r e h e n s i v e
under st anding of t he painful per cept ion is im por t ant
b eca u se i t d ea l s w i t h o t h er a sp ect s b esi d es p a i n
i n t e n si t y, su ch a s t h e a f f e ct i v e a n d m o t i v a t i o n a l
aspect s of pain and t he assessm ent of it .
The pur pose of m easur ing is t o assign value
t o a f e a t u r e , t r a i t , o r st a t e . I n t h e ca se o f p a i n
m easu r em en t , t h e p u r p ose is t o g iv e v alu e t o t h e
pain ex per ienced and/ or per ceiv ed. Psy chophy sics is
an experim ent al branch of Psychology t hat deals wit h
m easur ing and assessing m echanism s and pr ocesses
e n t a i l e d i n d i f f e r e n t s e n s i t i v e a n d p e r c e p t i v e
m odalit ies( 1 ).
The values of t he exponent supply inform at ion
on t he basic propert ies of t he “ inflow- out flow” of t he
sensor y and t he per cept ion dim ension being st udied;
t his feat ur es t he r at e at w hich an “out flow” sy st em ,
i n d e x e d b y t h e se n sa t i o n , g r o w s b e ca u se o f t h e “ inflow” of t he st im ulus. The power funct ion advocat es
t hat t he principle of invariance bet ween st im ulus and
sensat ion rat io, can be applied t o all sensory syst em s,
and is essent ial t o sur v ival of t he body, t hat is, t he
se n so r y t r a n sd u ce r w o r k s a s a e x p a n d e r o f t h e
en cou r agin g en er gy w h en n ecessar y( 2 ).
M a g n i t u d e e s t i m a t i o n i s b a s e d o n t h e
j u dgm en t of in div idu als t o sev er al st im u li, an d it is
on e of t h e m et h ods u sed t o pr odu ce a r at io scale.
The idea is t o m at ch perceived int ensit y of a physical
st im ulus wit h anot her percept ion. I t is defined as t he
pr ocess t o assign n u m ber s pr opor t ion al t o social or
cl i n i ca l st i m u l u s t h a t r e f l e ct t h e i n t e n si t y o f t h e
subj ect ive answer. This m et hod has im port ant feat ures
as a m easur e st r at egy for subj ect iv e concept s such
as pain( 3).
Wh en m agn it u de scales ar e design ed, t h ey
sh ou ld u n d er g o p sy ch op h y sics v alid at ion p r ocesses
w i t h t h e u se o f cr o ss- m o d al i t y m at ch i n g w h i ch i s
specif ically dev eloped t o ch eck ex pon en t s obt ain ed
by r at io or m agn it u de est im at ion , accor din g t o t h e
t y pes of r esponse used.
Th e p ar ad i g m o f cr o ss- m o d al i t y m at ch i n g
supplies a m et hod t o confir m t he pow er law , w hich
c h e c k s t h e f e a t u r e d e x p o n e n t a n d r e l a t e s t h e
m agnit ude of st im ulus wit h t he m agnit ude of subj ect ive
an sw er. Th u s, in st ead of h av in g su bj ect s com bin in g
num bers t o st im ulus int ensit ies, t hey use line lengt hs
( t ape m easur e) as a t y pe of r esponse. Thus, t o r at e
a pain int ensit y scale, each subj ect m ay be guided t o
point out t he size of t ape m easur e t hat cor r esponds
t o t h e in t en sit y of p ain , t h e g r eat er t h e p ain , t h e
great er t he lengt h of t he line( 4).
Psychophysics assess sensor y, desirable, and
cognit ive com ponent s of pain, t hus, it is very im port ant
t o en h a n ce i t s a ssessm en t , esp eci a l l y b eca u se i t
supplies ways t o m easure pain percept ion in it s several
dim en sion s( 5 ).
Th e p r o b l em t o assess an d m easu r e p ai n
b ecom es p sy ch op h y sical an t it in v olv es d et ect ion ,
discr im inat ion, and m agnit ude of t he answ er t o t he
p ain f u l st im u lu s, t h u s, p sy ch op h y sics p r esen t s t h e
cen t r al assu m pt ion t h at t h e per cept ion sy st em is a
m easu r in g m ech an ism( 6 ).
Measuring pain has been considered as a m ain
challenge for t hose t hat want t o cont rol it adequat ely,
since pain is underst ood as a com plex, individual, and
s u b j e c t i v e p e r c e i v e d e x p e r i e n c e , t h a t m a y b e
qu an t if ied on ly in dir ect ly. Ev er sin ce pain h as been
st u d ied in d if f er en t w ay s in t h e in v est ig at ion w it h
anim als, hum an beings, in labor at or ies or in clinical
sit u at ion s, in t egr at ion of t h e k n ow ledge f r om t h ese
dom ain s h as in cr eased.
The search for underst anding how t he painful
p h e n o m e n a o ccu r, h o w i t i s p e r ce i v e d b y t h o se
exper iencing it , and by t hose t r eat ing it r esult s fr om
t he m ain goal professionals from t he field have, which
is t o t r y t o adj ust t r eat m ent accor ding t o t he sour ce
OBJECTI VES
Gen er al ob j ect iv es
- To r a n k t h e d i f f e r e n t t y p e s o f p a i n p r e s e n t ,
c o m p a r i n g t h e m u s i n g d i f f e r e n t p s y c h o p h y s i c a l
m et h od s;
- To validat e t he rat io scale derived t o t he nonm et ric
cont inuum of int ensit y of t he differ ent t y pes of pain
using cr oss- m odalit y m at ching.
Specif ic Obj ect iv es
- t o assess if t he r ank of t he differ ent t y pes of pain
d er iv ed f r om t h e t w o p sy ch op h y sical m et h od s ar e
sim ilar ;
- t o ch eck st abilit y an d/ or equ iv alen ce of t h e r at io
scale, using t wo different answer m odalit ies, num erical
( m agnit ude est im at es) and v isual ( line lengt h) .
MEASURI NG PAI N
Ex p er i m en t – Va l i d a t i o n o f t h e r a t i o sca l e o f t h e
d if f er en t t y p es of p ain u sin g m ag n it u d e est im at ion
m et hod and cross- m odalit y m at ching wit h t he answer
using line lengt hs
This st udy has been approved by t he Et hical
Com m it t ee of t he Hospit al das Clínicas of t he Medical
School of Ribeir ão Pr et o, Univer sit y of São Paulo. All
par t icipan t s gav e t h eir w r it t en con sen t , sign in g t h e
t er m ap p r ov ed b y t h is com m it t ee af t er t h ey w er e
v er bally ex plained about t he r esear ch, it s obj ect iv es
and accept ed t o t ak e par t .
Th is is an ex p er im en t al q u an t it at iv e st u d y
using Psy chophy sics as t he par adigm and t heor et ical
r ef er en ce( 2 - 4 ).
Met h od s
Participants: Thirt y out pat ient s from different
clinical specialt ies t ook par t in t he st udy ; t hey w er e
over 18 and were chosen from a convenience sam ple
t hat could pr esent any of t he t y pes of pain st udied.
Si x t y h e a l t h p r o f e ssi o n a l s, 3 0 p h y si ci a n s a n d 3 0
n u r se s a l so ch o se n f r o m a co n v e n i e n ce sa m p l e ,
specialized in different areas. The place of st udy was
t h e Hosp it al d as Clín icas of t h e Med ical Sch ool of
Ribeir ão Pr et o.
Material: Pens and not epads, on t he first page t h e r e w e r e s p e c i f i c i n s t r u c t i o n s f o r e a c h
psychophysical m et hod and, in t he following pages, a list wit h 20 different t ypes of pain and t heir respect ive
defin it ion . Addit ion ally, a pr ofession al t ape m easu r e wit h 5 m et ers in lengt h was used.
Pr o ced u r e: Psy ch o p h y si cs m e t h o d s u se d w e r e m a g n i t u d e e s t i m a t i o n m e t h o d a n d c r o s s
-m odalit y -m at ch in g in v olv in g t h e an sw er con t in u u -m of t he line lengt h.
The inst r um ent for dat a collect ion w as built using t he different t ypes of pain: Low back pain, Head
ach e, Join t pain , Bu r n pain , Per iph eral Neu r opat hy,
Pa i n d u e t o r e p e a t e d st r a i n i n j u r i e s, AI D S p a i n , Post operat ive pain, Cancer pain, Labor pain, Pain due
t o Tem por om andibular Joint Disor der ( TMJ) , Pain due t o Herpes- Zost er, Tr igem inal neuralgia, fibr om yalgia,
Myocardial I nfarct ion Pain, Renal colic pain, Pain from Gast ric Ulcer, biliary colic pain, Menst rual Cram ps pain,
a n d To o t h a ch e . Fo r e a ch m e t h o d u se d , d i f f e r e n t
inst r uct ions w er e m ade.
I nst r uct ions giv en t o subj ect s, r egar dless of
t he cont inuum of answ er em ploy ed, dem anded t hat j u d g m en t s w er e p er f o r m ed acco r d i n g t o i n t en si t y
given t o one t ype of pain.
I n t he m et hod of m agnit ude est im at ion, t he
t ask of par t icipan t s w as t o giv e a n u m ber for each t ype of pain t hat was proport ional t o pain int ensit y of
t hat t ype and com pare it wit h St andard st im ulus t hat w as low back pain w it h num er ical v alue of 100. For
exam ple, if part icipant s considered t hat a cert ain t ype
of pain was t wo t im e m ore int ense t han low back pain, t hey should give t o it a num ber t wice as big, t hat is,
200. I f part icipant s considered t hat a cert ain pain had half the intensity of low back pain, they should give this
type of pain a num ber that was the half, that is, 50. I n t he cr oss- m odalit y m at ching, inv olv ing a
r e s p o n s e c o n t i n u u m o f l i n e l e n g t h , t h e t a s k o f part icipant s was t o m at ch a line lengt h for each pain
t hat was proport ional t o t he int ensit y of pain, and t hen com pare it t o t he st andard st im ulus t hat was low back
pain. This st andard st im ulus had a 50 cm lengt h. For exam ple, if part icipant s considered t hat a t ype of pain
w as t w ice as m u ch in t en se as low back pain , t h ey
sh ou ld m at ch t h e lin e len g t h t w ice as lon g as t h e st andar d st im ulus, t hat is, appr ox im at ely 100 cm . I f
p ar t i ci p an t s f i n d t h at a t y p e o f p ai n h ad h al f t h e int ensit y of low back pain, t hey should m at ch a lengt h
that would be half of the standard, approxim ately 25 cm . Each su bj ect est ablish ed t w o est im at es f or
an ot h er for lin e len gt h . Th e sam e 9 0 su bj ect s t ook par t in t he t w o t ask s, and t he t ask s w er e pr esent ed in a r andom or der for each par t icipant . Par t icipant s m ade t he j udgm ent s indiv idually.
Fo r d a t a a n a l y si s, g eo m et r i c m ea n s w er e a s s e s s e d t o g e t h e r w i t h s t a n d a r d d e v i a t i o n o f geom et ric m eans of t he m agnit ude est im at es and line lengt h m at ching est im at es. Rank of posit ions for each o f t h e d i f f e r e n t t y p e s o f p a i n f o r e a ch g r o u p o f p ar t i ci p an t s, t h at i s, o u t p at i en t s, p h y si ci an s, an d n u r ses w er e est ab lish ed . I n ad d it ion , t h e f u n ct ion e x p o n e n t w a s ca l cu l a t e d t o g e t h e r w i t h Ke n d a l l ’ s
coefficient of concor dance ( W) .
n i a P f o s e p y
T OPME R OPLL R Phy.ME R Phy.LL R Nur.ME R Nur.LL R
n i a P r e c n a
C 277.80 1 98.50 1 345.72 2 135.45 1 335.81 1 125.13 1
n i a P n o it c r a f n I l a i d r a c o y
M 225.20 2 84.60 2 265.57 5 110.33 4 279.69 3 115.92 3
n i a P S D I
A 204.70 3 77.50 4 100.03 16 61.79 14 134.56 13 75.91 9
n i a P c il o C l a n e
R 177.70 4 83.30 3 383.47 1 130.19 2 294.75 2 118.86 2
n i a P r o b a
L 152.60 5 64.50 6 330.39 3 116.48 3 275.53 4 104.47 4
a i g l a y m o r b i
F 135.00 6 70.20 5 74.70 20 42.00 19 136.98 11 79.06 8
n i a P c il o C y r a il i
B 127.30 7 63.40 7 194.08 8 85.32 9 175.29 6 83.04 7
n i a P r e c l U c i r t s a
G 110.80 8 61.20 8 156.53 11 76.70 10 146.68 8 74.41 10
n i a P n r u
B 104.70 9 61.10 9 211.04 7 99.08 7 239.13 5 96.94 5
a i g l a r u e N l a n i m e g i r
T 104.50 10 47.80 14 268.74 4 105.92 5 115.66 17 68.02 14
e h c a h t o o
T 102.20 11 60.10 10 158.83 10 71.58 11 139.77 9 72.98 12
n i a p k c a b w o
L 100.00 12 50.00 13 100.00 17 50.00 17 100.00 19 50.00 20
e h c a d a e
H 93.40 13 44.90 17 143.32 12 58.99 15 120.17 16 59.93 17
n i a p r e d r o s i d J M
T 92.60 14 46.20 15 123.21 14 62.86 13 123.39 14 66.45 16
n i a p e v it a r e p o t s o
P 87.00 15 53.70 11 177.17 9 87.87 8 173.70 7 89.28 6
n i a p y h t a p o r u e N l a r e h p i r e
P 85.10 16 51.30 12 101.40 15 64.87 12 138.76 10 73.75 11
n i a p p m a r c l a u r t s n e
M 70.70 17 45.00 16 126.35 13 56.78 16 108.78 18 67.47 15
s e i r u j n i n i a r t s d e t a e p e
R 96.90 18 35.60 19 76.42 19 41.00 20 92.37 20 52.93 19
n i a P t n i o
J 58.00 19 36.20 18 82.66 18 47.55 18 122.67 15 58.80 18
n i a P r e t s o Z s e p r e
H 42.60 20 27.80 20 222.12 6 101.14 6 136.80 12 72.44 13
RESULTS
I n t he group of out pat ient s, t he t ypes of pain
of great er int ensit y, bot h in m agnit ude est im at ion and
in cross- m odalit y m at ching ( line lengt h) were: Cancer
Pain, Myocardial I nfarct ion Pain, AI DS Pain, Renal colic
pain , Labor Pain an d Fibr om y algia. I n t h e gr ou p of
phy sicians t hey w er e: Cancer Pain, Renal Colic Pain,
Labor Pain, Myocardial I nfarct ion Pain, and Trigem inal
Ner v e Pain. I n t he nur ses gr oup t hey w er e: Cancer
Pain , Ren al Colic Pain , My ocar d ial I n f ar ct ion Pain ,
Labor Pain and Bur n Pain ( Table 1) .
Table 1 – Geom et ric Mean of t he m agnit ude est im at es ( ME) and line lengt h est im at es ( LL) for t he different t ypes
of pain ranked ( R) accor ding t o Out pat ient s ( OP) , phy sicians ( Phy.) and Nur ses ( Nur )
Table 1 also pr esent s t he differ ent t y pes of
pain classified as sm aller int ensit y t ypes. I n t he group
of out pat ient s, t he t ypes of pain assessed as sm aller
int ensit y, bot h in t he m agnit ude est im at es and in lines
lengt h, were Herpes Zoster Pain, Joint Pains, Repeat ed
st rain inj uries, and Menst rual Cram p Pain; in t he group
o f Ph y si ci an s t h ey w er e Rep eat ed st r ai n i n j u r i es,
Fibr om y algia, Join t Pain an d Low back pain ; in t h e
group of nurses t hey were: Low back pain, Repeat ed
st r ai n i n j u r i es, Jo i n t Pai n , Men st r u al Cr am p p ai n .
Ou t com es sh ow ed gr eat er dif f er en ce am on g gr ou ps
r efer r ing t o less int ensit y pain.
Kendall’s coefficient of concor dance ( W) w as
applied t o est im at es of m et hods used, com paring t he
rank for t he different t ypes of pain. For t he group of
out pat ient s W= 0. 87, for t he gr oup of nur ses W= 81,
and for t he group of physicians W= 0.86. This indicat es
t hat ranking of t he t wo est im at es are highly agreeable, w it h st at ist ically significant p< 0.001.
I n pict ur e 1, geom et r ic m eans of line lengt h est im at es for t he gr oup of out pat ient s ar e pr oj ect ed i n l o g a r i t h m i c c o o r d i n a t e s , a c c o r d i n g t o t h e co r r esp o n d i n g g eo m et r i c m ea n s o f t h e n u m er i ca l est im at es for each t y pe of pain. A st r aight line w it h an inclinat ion ( exponent of t he power funct ion) of 1.40 was for m ed. How ev er, as obser v er s t end t o lim it t he am plit ude of t he adj ust m ent s according t o t he variable t hey cont r ol, on Pict ur e 2, t hese m eans in r ev er sed coor dinat es hav e been pr oj ect ed t hat is, m agnit ude est im at es accor din g t o t h e cor r espon din g est im at es o f l i n e l e n g t h f o r e a ch t y p e o f p a i n w i t h a 0 . 6 6 inclinat ion of t he st raight line.
Psy ch op h y sical scale of t h e d if f er en t t y p es of pain in t he group of out pat ient s was assessed, and
Figure 1 – Correlat ion bet ween logarit hm s of geom et ric m ean of line lengt hs and logarit hm s of geom et ric m ean
of m agnit ude est im at es giv en t o t he differ ent t y pes
of pain, out pat ient s, r2= 0.94
Fi g u r e 2 - Co r r el at i o n b et w een l o g ar i t h m s o f t h e g e o m e t r i c m e a n o f m a g n i t u d e e s t i m a t e s a n d
logarit hm s of t he geom et ric m ean of line lengt hs given
t o t he different t ypes of pain, out pat ient s, r2= 0.94
Geom et ric m eans of est im at es of line lengt hs
o f p h y si ci a n s h a v e b een p r o j ect ed i n l o g a r i t h m i c
coordinat ed according t o t he corresponding geom et ric
m ean s for each t y pe of pain . A st r aigh t lin e w it h a
1.34 inclinat ion ( exponent of t he power funct ion) was
m a d e . Li k e w i se , t h e se m e a n s w e r e p r e se n t e d i n
r ev er sed coor din at es, t h at is, m agn it u de est im at es
accor ding t o t he cor r esponding line lengt hs for each
t y pe of pain , w it h a 0 . 7 0 in clin at ion in t h e st r aigh t
line. The respect ive pict ures have not been present ed
i n t h i s a r t i cl e ; h o w e v e r, t h e y p r e se n t t h e sa m e
feat ur es of t he pr ev ious pict ur es.
Psy ch op h y sical scale of t h e d if f er en t t y p es
of pain in t he group of physicians was validat ed, and
t he geom et r ic m ean of t he ex ponent s w as 0.96.
I n t he gr oup of nur ses, geom et r ic m eans of
l i n e l e n g t h e s t i m a t e s h a v e b e e n p r o j e c t e d i n
logarit hm ic coordinat es according t o t he corresponding
geom et ric m eans of t he num erical est im at es for each
t y pe of pain . A st r aigh t lin e w it h a 1 . 4 2 in clin at ion
( ex p on en t of t h e p ow er f u n ct ion ) w as b u ilt . Th ese
m eans are in reversed coordinat es, t hat is, m agnit ude
est im at es accor ding t o line lengt hs for each t y pe of
pain, w it h a 0.65 inclinat ion of t he st r aight line. The
r espect iv e pict ur es hav e not been pr esent ed in t his
ar t icle; how ev er, t hey pr esent t he sam e feat ur es of
t he pr ev ious pict ur es.
Psy ch op h y sical scale of t h e d if f er en t t y p es
of pain in t he group of nurses was validat ed and t he
geom et r ic m ean of ex ponent s w as 0. 96.
Ex ponent v alue for t he t hr ee gr oups st udied
was 0.96. Such values were close t o t hose predict ed,
t hat is, 1.00, when line lengt hs and m agnit ude est im at e
m a t c h i n g w e r e d i r e c t l y i n v o l v e d . Th e p r o o f o f
eq u i v al en ce b et w een em p i r i cal ex p on en t an d t h at
p r ed i ct ed i n a ca l i b r a t i o n t a sk , d i r ect l y i n v o l v i n g
sen sa t i o n s b et w een t h e t w o m et h o d s i s a st r o n g
evidence of t he validit y of m agnit ude est im at ion and,
t hus, of t he power law or St evens’s law( 4).
Cor r elat ion b et w een m ag n it u d e est im at ion
a n d l i n e l e n g t h i s a p o w e r f u n ct i o n w i t h a n o n
-significant ly exponent different from 1.00. Agreem ent
b et w een t h ese scale v alu es is h ig h , in d icat in g t h e
scales ar e hom ogeneous and consist ent .
DI SCUSSI ON
An ideal in st r u m en t t o assess an d m easu r e
p a i n m u st r e a ch t h e f o l l o w i n g cr i t e r i a : h a v e t h e
p r o p e r t i e s o f a r a t i o s c a l e , s u p p l y i m m e d i a t e
i n f o r m a t i o n o n a ccu r a cy a n d f a i t h f u l n e ss o f t h e
p e r f o r m a n c e o f s u b j e c t s o n t h e s c a l e a n s w e r s
g i v en , b e si m p l e t o u se w i t h p a t i en t s i n p a i n , i n
cl i n i ca l a n d r esea r ch co n t ex t s, b e a b l e t o a ssess
sen sit iv e an d af f ect iv e dim en sion s of pain , be u sef u l
b ot h f or ex p er ien ced an d clin ical p ain , an d en ab le
c o n f i d e n t c o m p a r i s o n s b e t w e e n b o t h t y p e s o f
p ain( 7 ).
The act ion of int raderm al sufent anil used wit h
or wit hout lidocaine for t he t reat m ent of pain induced
by t herm al st im ulus has been st udied using m agnit ude
est im at es. Nin e h ealt h y v olu n t eer s t ook par t in t h e
st udy, t hey received five t herm al st im uli in t he forearm
at differ ent t em per at ur es, w hich r anged fr om 44° t o
52° C, and so t hey est im at ed int ensit y of pain. Aft er
st im ulus, t hey received salt solut ion, or lidocaine, and/
or su f en t an il + lid ocain e; t h en t h ey assessed p ain
1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2 2,1
1,2 1,4 1,6 1,8 2 2,2 2,4 2,6
Magnitude etimates
Line lenght
1,2 1,4 1,6 1,8 2 2,2 2,4 2,6
1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2 2,1
Line length
again at 6 , 3 0 , 6 0 , 9 0 , 1 2 0 an d 1 5 0 m in u t es aft er
inj ect ion of t he m edicat ion. Result s showed t hat , at 6
m inut es aft er adm inist rat ion of m edicat ions, t he sit es
w e r e l i d o c a i n e a n d l i d o c a i n e + s u f e n t a n i l w e r e
adm inist ered obt ained a m ean of 83% less pain t han
t h e ot h er sit es. How ev er, t h er e w as n o d if f er en ce
a m o n g t h e p a i n f u l se n sa t i o n i n t h e si t e s w h e r e
lidocaine and lidocaine + sufent anil w er e applied, or
am ong sit es w her e sufent anil and salt solut ion w er e
applied. At 30 and 60 m inut es t hese pain scores were
sm al l er 3 8 % an d 2 0 % r esp ect i v el y, i n t h e u se of
lidocaine com pared t o t he salt solut ion and sufent anil.
At 90 m inut es, and in t he following m inut es, t he pain
scor es w er e t h e sam e as t h ose b ef or e m ed icat ion .
These result s suggest t hat int raderm al sufent anil has
no analgesic effect , and t hat in t he com binat ion w it h
lidocaine, sufent anil neit her st r engt hens nor pr olongs
t he analgesic effect of t his m edicat ion( 8).
I t can be highlight ed by t his st udy t hat t he
u s e o f p s y c h o p h y s i c a l m e t h o d f o r m a g n i t u d e
est im at es t hat leads t o a rat io scale, enables t o know
w hen a pain is great er or sm aller t han anot her.
Th e p e r c e p t i o n o f t h e r m a l p a i n a n d t h e
displeasu r e w as st u died com par in g t w o gr ou ps, t h e
Sou t h Asian ( I n d ia, Pak ist an an d Ban g lad esh ) an d
Caucasian English. Fort y m en t ook part , 20 from each
et hnic gr oup. For t his, sensor y quant it at iv e t est w as
used t hat defines not only st im ulus but also t he answer.
Th er m al st im u lu s w as ap p lied t o t h e f or ear m an d
pat ient s were request ed t o assess t hrough m agnit ude
est im at e t h e t h r esh old of cold, h eat det ect ion , an d
t he t hreshold of pain due t o heat or cold. Addit ionally,
t he t hreshold of sensory det ect ion was used wit h t he
m et h od of ascen d in g lim it s, w h en ch an g es on t h e
t em perat ure were det ect ed, t he pat ient was asked t o
sign al ( t h e t em per at u r e r an ged f r om 8 º t o 5 0 º C) .
Th e m easu r e of in t en sit y an d displeasu r e r egar din g
pain w it h a num er ical scale of 0- 100 w as also used
for t herm al st im ulus at 46, 47, 48 and 49º C. Result s
s h o w e d t h a t t h e r e w e r e n o d i f f e r e n c e s o n t h e
percept ion of cold and heat bet ween t he t wo groups.
However, t here were st at ist ically significant differences
b et w een t h e t w o g r ou p s f or t h e t h r esh old an d t h e
i n t e n s i t y o f p a i n d u e t o h e a t ; S o u t h - A s i a n s
dem onst r at ed sm aller t hr eshold for heat and gr eat er
sensibilit y t o pain. Per cept ion of int ensit y ex pr ession
an d r epor t of pain ar e in flu en ced by t h e social an d
cult ur al env ir onm ent( 9 ).
Th u s, t h e pr esen t st u dy v alidat es t h e scale
of per cept ion of t h e dif f er en t t y pes of pain f or ou r
cou n t r y an d m or e pr ecisely for ou r r egion , poin t in g
ou t t h e pain con sider ed as m or e in t en se an d t h ose
consider ed as less int ense.
Anot her st udy( 10) inv est igat ed descr ipt or s or
h i g h er o r l o w er a t t r i b u t i o n t o ch r o n i c p a i n u si n g
psychophysical m et hods of m agnit ude est im at ion and
cross- m odalit y m at ching in t he m odalit y of answer in
l i n e l en g t h . I n a f i r st ex p er i m en t , t h e m ag n i t u d e
est im at ion m et hod w as used w her e 30 pr ofessionals
o f t h e h e a l t h a r e a ( p h y s i c i a n s , n u r s e s a n d
psychologist s) assessing 100 pain descript ors. Of t his
ex per im ent , 15 descr ipt or s hav e been select ed fr om
sev er al posit ions; t hey w er e pr esent ed on a second
ex per im en t t o an ot h er 3 0 h ealt h pr of ession als t h at
assessed t h em u sin g t w o p sy ch op h y sical m et h od s.
Out com es show t hat descript ors t hat described chronic
p ain b est in ou r cu lt u r e ar e d ep r essiv e, p er sist en t
and dist ressing, and t hose describing less chronic pain
ar e ag g r essiv e, in t en se, an d com p r essiv e, b ot h in
t h e m agn it u de est im at ion an d in t h e cr oss- m odalit y
m at ch in g m et h od. Ken dall’s coef f icien t con cor dan ce
w as calcu lat ed , W= 0 . 9 9 , sh ow in g t h at t h e r an k in g
r e s u l t i n g f r o m t h e t w o m e t h o d s a r e h i g h l y
a g r e e a b l e .
CONCLUSI ONS
- Cancer Pain, Myocardial I nfarct ion Pain, Renal Colic
Pain, Bur n Pain, and Labor Pain w er e consider ed as
t h e m o s t i n t e n s i v e p a i n , r e g a r d l e s s o f t h e
psy chophy sical m et hod used or t he sam ple st udied;
- Repeat ed St rain I nj ury, Joint Pain, Menst rual Cram p
Pain and Low back pain w er e consider ed as t he less
int ensiv e pain;
- Ken dall’s v alu e ( W) f or t h e t h r ee gr ou p in dicat ed
t h at r an k in g r esu lt in g fr om t h e t w o est im at es w er e
highly agr eeable, w it h p< 0. 001 w hich is st at ist ically
sign if ican t ;
- Relat ionship bet w een t he m agnit ude est im at es and
t he m at ching of line lengt hs is a pow er funct ion and
t he scale of t he different t ypes of pain is valid, st able
and consist ent , because t he exponent obt ained in t he
differ ent sam ples st udied w as equal t o 0.96 t o all of
t h em ; su ch ex pon en t w as n ot sign ifican t ly differ en t
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