Seediscussions,stats,andauthorprofilesforthispublicationat:http://www.researchgate.net/publication/5612209

ElectricalPropertiesofAcupuncturePointsandMeridians:ASystematicReviewARTICLEinBIOELECTROMAGNETICSMAY2008ImpactFactor:1.86DOI:10.1002/bem.20403Source:PubMed

CITATIONS93

DOWNLOADS460

VIEWS249

8AUTHORS,INCLUDING:

AgathaPColbert38PUBLICATIONS427CITATIONS

SEEPROFILE

rjanGMartinsenUniversityofOslo98PUBLICATIONS885CITATIONS

SEEPROFILE

RichardHammerschlagOregonCollegeofOrientalMedicine102PUBLICATIONS1,773CITATIONS

SEEPROFILE

SteveCinaTheNewEnglandSchoolofAcupuncture9PUBLICATIONS118CITATIONS

SEEPROFILE

Availablefrom:rjanGMartinsenRetrievedon:13July2015

Author Proof

ABioelectromagnetics 00:1^12 (2008)

Review

Electrical Properties of Acupuncture Pointsand Meridians: ASystematic Review

Andrew C. Ahn,1,2,3* Agatha P. Colbert,4 Belinda J. Anderson,5 -rjan G. Martinsen,6,7

Richard Hammerschlag,8 Steve Cina,9 Peter M.Wayne,1 and Helene M. Langevin10,11

1Division for Research and Education in Complementary andIntegrativeMedical Therapies, HarvardMedical School, Boston, Massachusetts

2Division of GeneralMedicine andPrimary Care, Beth Israel DeaconessMedical Center,Boston, Massachusetts

3Center for Biomedical Engineering, Massachusetts Institute of Technology,Cambridge, Massachusetts

4Helfgott Research Institute, National College of NaturalMedicine, Portland, Oregon5Pacific College of OrientalMedicine, NewYork, NewYork6Department of Physics, University of Oslo, Oslo, Norway

7Department of Clinical andBiomedical Engineering, Rikshospitalet, Oslo, Norway8Oregon College of OrientalMedicine, Portland, Oregon

9NewEngland School ofAcupuncture,Watertown, Massachusetts10Department of Neurology, University of Vermont, Burlington,Vermont

11Department of Orthopaedics andRehabilitation, University of Vermont,Burlington,Vermont

According to conventional wisdom within the acupuncture community, acupuncture points andmeridians are special conduits for electrical signals. This view gained popularity after anecdotalreports and clinical studies asserted that these anatomical structures are characterized by lowerelectrical impedance compared to adjacent controls. To ascertain whether evidence exists to support orrefute this claim, we conducted a systematic review of studies directly evaluating the electricalcharacteristics of acupuncture structures and appropriate controls. We searched seven electronicdatabases until August 2007, hand-searched references, and consulted technical experts. We limitedthe review to primary data human studies published in English. A quality scoring system wascreated and employed for this review. A total of 16 articles representing 18 studies met inclusioncriteria: 9 examining acupuncture points and 9 examining meridians. Five out of 9 point studiesshowed positive association between acupuncture points and lower electrical resistance andimpedance, while 7 out of 9 meridian studies showed positive association between acupuncturemeridians and lower electrical impedance and higher capacitance. The studies were generally poorin quality and limited by small sample size and multiple confounders. Based on this review, theevidence does not conclusively support the claim that acupuncture points or meridians areelectrically distinguishable. However, the preliminary findings are suggestive and offerfuture directions for research based on in-depth interpretation of the data. Bioelectromagnetics00:112, 2008. 2008 Wiley-Liss, Inc.

Key words: impedance; resistance; capacitance; skin; electrodermal

62008Wiley-Liss, Inc.BEM07-0187.R1(20403)

Grant sponsor: National Center for Complementary AlternativeMedicine (NCCAM); Grant number: K23-AT003238.

*Correspondence to: Andrew C. Ahn, Harvard Medical School,Division for Research and Education in Complementary andIntegrative Medical Therapies, 401 Park Drive Suite 22A-West,Boston, MA 02215. E-mail: aahn@hms.harvard.edu

Received for review 12 October 2007; Final revision received 28November 2007

DOI 10.1002/bem.20403Published online in Wiley InterScience(www.interscience.wiley.com).

Author Proof

ABACKGROUND

Despite hundreds of mechanistic and clinical studiesin acupuncture, the fundamental tenets of acupuncturethe point and meridianare poorly understood. ClassicChinese medical theory recognizes about 361 points, saidto be located on 14 main meridians connecting the body.The 14 main meridians are associated with specific organsand serve as pathways for the flow of vital energy or qi[Birch and Felt, 1999; Kaptchuk, 2002]. Within theacupuncture community, it is a commonly held opinionthat these acupuncture structures are special conduitsfor electrical signals [Brewitt, 1995]. This view gainedpopularity as early as the 1950s when anecdotal reportsand clinical studies from China, Japan, France, Germany,and the United States asserted that acupuncture points andmeridians are distinguishable by their lower electricalimpedance compared to adjacent controls [Royal andRoyal, 1991; Brewitt, 1995]. As this view gained traction,devices such as acupuncture point locators and electro-diagnostic devices became commercially available toscientifically assist the clinicians in diagnosis andtreatment delivery.

The fundamental premise by which these deviceswere developed, however, has always been viewed withconsiderable skepticism from the conventional scien-tific community. Confounding factors, such as skinmoisture, electrode pressure, stratum corneum thick-ness, electrode polarization, and other factors have ledmany to assert that the reportedly distinct electricalcharacteristics are attributable to external factors and/orartifacts and not to the acupuncture point or meridian.To this day, no systematic evaluation of these studieshas been conducted.

This article aims to systematically review andsummarize the studies evaluating the electrical propertiesof acupuncture points and meridians. This review assesseswhether sufficient evidence can support or refute the claimthat acupuncture structures are electrically distinct. Tomaintain focus, we limited the review to human studies.This review does not include studies that assess theclinical significance of these electrical measures, focus onthe temporal behavior of electrical measurements atacupuncture structures alone, or offer theoretical explana-tion for this reported association without empirical data.To make this review as objective as possible, we createdand employed a scoring system to characterize the qualityof the studies that met review criteria.

EVIDENCE ACQUISITION

Search Strategy

We sought studies that evaluated the electricalproperties of acupuncture points and meridians com-

pared to appropriate controls. We searched sevenelectronic databases, including PubMed, CochraneLibrary Database, AltHealthWatch (EBSCO Host),Allied and Complementary Database (AMED), Biosis,EMBASE, and Scientific Citation Index Expanded fordates ranging from the databases inception to August2007 for all seven databases. We also searched theConference Paper Index and Dissertation Citationbut found no useful citations or references in thesetwo databases. Searches were limited to the Englishlanguage due to translation challenges.

Titles, abstracts, and keyword lists of the sevenelectronic databases were searched using the followingMeSH terms: acupuncture, acupoint, and meridiancrossed with the terms: impedance, resistance, conduc-tivity, conductance, admittance, susceptance, potential,capacitive, capacitance, electropermeable, electrophy-siologic, electrodermal, electrodiagnostic, and electro-diagnosis. The MeSH terms were exploded to maximizeyield and to capture all possible relevant studies. Welimited the search to Human or English languagestudies, if such search options were available. Wherepossible, related articles function was used to identifyadditional references. We referred to popular acupunc-ture texts to identify other potential studies, hand-searched all relevant references from papers and texts,and contacted experts in the field to identify anyadditional references.

Study Selection

For each database citation, we read the fullabstract to determine whether acupuncture pointsor meridians were measured electrically. Whenthe abstract lacked sufficient detail or was simplyabsent, the full text article was acquired for citationscontaining titles or abstracts indicating involvementof electrical stimulation or device. Full text articlescontaining primary data on electrical measures atpoints and/or meridians as well as controls weremaintained in the review and further evaluatedfor methodological quality. Controls were definedas (1) areas not containing an acupuncture point ormeridian or (2) areas within the vicinity of a pointor meridian. Based on the second definition, studiescontaining only topographic profiles of electricalmeasures around an acupuncture point were maintainedin the review. Non-English publications and studieswith animals were excluded. We did not includestudies that evaluated the clinical significance ofelectrical measures, reported electrical measurementswithout appropriate controls, or speculated on themechanistic reasons for these electrical characteristicsat acupuncture points or meridians without empiricaldata.

2 Ahn et al.

Bioelectromagnetics

Author Proof

AFull-text articles were further screened with a

predetermined set of scoring criteria and eliminated ifthey scored less than three out of the possible tenpoints. This strategy was employed based on theassumption that poor quality studies would unlikelycontribute meaningfully to our understanding ofacupuncture points and meridians.

Development and Application of theScoring Instrument

To assess study quality in a manner that minimizessubjective, a set of scoring criteria was created forthis review. The criteria were developed by a multi-disciplinary panel of five experts, representing therelevant disciplines of acupuncture, biomedicine,electrophysiology, biophysics, electrical engineering,and survey methodology. Each panelist first produceda list of items he/she considered important forevaluating electrical characteristics at acupuncturesites. The items were combined into one large listand resent to all panelists for reevaluation. Items withlow face validity were eliminated by consensus, withthe understanding that the instrument should becomprehensive yet flexible enough to account forstudy diversity. The items were presented in a yes/no/partial format to minimize subjectivity.

Based on panelists feedback, a preliminaryscoring instrument was created and subsequentlytested on selected articles by three academic clini-cianstwo of whom were not on the panel of experts.Problems in clarity and/or applicability of eachitem were identified, and wording was modified toaddress these concerns. The panelists categorized theitems into ten domains: subjects and settings, siteselection, controls, electrode, confounding variables,instruments, electrical input, measurements, blinding,and result/statistical analysis. Each domain has a valueof one point, yielding a total of ten points for the scoringsystem. The final instrument was resent to panelistsfor final approval. (The final scoring instrument can beviewed at http://osher. hms.harvard.edu/pu_general_pub.asp.)

Two physicians (AA and AC) with backgrounds inacupuncture and electrophysiology independentlyreviewed and scored the qualifying studies. Thesereviewers were not blinded to the study title or authorsnames. Each item within the scoring criterion wasdiscussed until a final agreement was reached. For thoseitems where an agreement could not be reached, a thirdparty evaluator was involved to achieve consensus.Relevant data were extracted from the studies andaggregated in tabular form.

EVIDENCE SYNTHESIS

Selection Results

From 1663 citations, we identified 320 withpotential relevance to this review (see Fig. 1). Afterobtaining and reading the full texts, we identified50 articles that actively measured electrical parametersat the skin. Of these articles, 10 were excluded due tolack of a control [Nakatani, 1956, 1986; Nakatani andYamashita, 1977; Motoyama et al., 1984; Motoyama,1986; Ionescutirgoviste et al., 1987; Cho and Chun,1994; Comunetti et al., 1995; Cheng et al., 2000; Fanget al., 2004]; 16 were excluded due to poor quality asdefined by a quality score of less than three out ofpossible ten points [Bergsmann and Woolley-Hart,1973; Noordergraaf and Silage, 1973; Brown et al.,1974; Ghaznavi, 1974; Roppel and Mitchell, 1975;Becker, 1976; Shenberger, 1977; Eory, 1984; Zhu et al.,1984; Croley, 1986; Nansel and Jansen, 1988; Zhu et al.,1988; Chen, 1996; Eickhorn and Schimmel, 1999; Luet al., 1999; Halek, 2000]; and 6 were excluded for usingelectrical parameters to initially define acupuncturepoints or meridians [Wulfson and Warren, 1976;Prokhorov et al., 2000a,b, 2006; Lee et al., 2003; Zhanget al., 2004]. Sixteen articles representing 18 studieswere maintained in the review and evaluated in detail.Nine studies evaluated the acupuncture point [Reich-manis et al., 1975, 1976; Hyvarinen and Karlsson, 1977;McCarroll and Rowley, 1979; Poon et al., 1980; Falket al., 2000; Pearson et al., 2007], while the other nineevaluated the acupuncture meridian [Reichmanis et al.,1977a,b, 1979; Hu et al., 1992; Zhang et al., 1999a;Martinsen et al., 2001; Johng et al., 2002; Lee et al.,2003; Ahn et al., 2005].

Acupuncture Points: Data Summary

Most studies evaluating the acupuncture pointswere of poor quality and published in journals withlow citation index (see Table 1). All studies testedthe hypothesis that acupuncture points are areas oflower resistance or impedance. Overall, the samplesizes were small (mean N 13), and study participantswere mostly healthy. DC or low frequency currentswere commonly used and thus electrical resistanceor conductance was the parameter most frequentlyevaluated. In four cases, the choice of controls wasinadequately justified and could have easily influencedthe outcome [Reichmanis et al., 1975, 1976; Falk et al.,2000; Pearson et al., 2007]. All studies employed amonopolar electrode arrangement with a smaller activeelectrode over the point(s) of interest and a largerreference electrode frequently held in the hand by thestudy participant. In addition, the studies tended to limit

Properties of Acupuncture Points andMeridians 3

Bioelectromagnetics

Author Proof

Atheir evaluation to the upper extremities. Only threestudies evaluated acupoints not located on the armsand evaluated points on the ear and forehead aswell [Hyvarinen and Karlsson, 1977; Falk et al., 2000;Pearson et al., 2007].While five out of nine studies showed a positiveassociation between acupuncture points and decreasedelectrical impedance/resistance, the higher qualitystudies showed little to no association. Pearson et al.sstudy [2007], the highest rated study, used two devicesone with a DC current and the other with a 100 Hz ACcurrentto determine the resistance/impedance at an(1) acupuncture point, (2) non-acupuncture point locatedon a meridian, and (3) a non-acupuncture point not on ameridian. These three points were identified on severalbody sites that included the palm (PC8), forehead(GB14), and fourth finger (TW1). Only acupoint GB14showed any significant differencewith the non-meridian/non-acupuncture control and, furthermore, this differ-ence was seen only with the 100 Hz device. The meridianpoints, on the other hand, demonstrated significant (ornear significant) decrease in electrical impedancecompared to the non-meridian control in all three bodysites with the exception of the DC resistance at acupointPC8.

In evaluating acupuncture points, two generalstrategies were taken. One strategy was to firstidentify the acupuncture point/control and then meas-

ure the electrical resistance or conductance [McCarrolland Rowley, 1979; Pearson et al., 2007]. The otherstrategy was to scan or survey the skin to identifylow resistance areas and subsequently see if theareas coincided with acupuncture points [Hyvarinenand Karlsson, 1977]. The studies that resorted tothe latter method tended to have more positiveresults than those taking the former approach. Thisimplies that the inappropriate or inaccurate identifica-tion of points might have contributed to the discrepantfindings.

The techniques applied in these studies wereremarkably diverse, particularly with respect to probetype. Reichmanis in 1975 wheeled a circular steelelectrode 0.2 cm in diameter along the meridian andcontrol line [Reichmanis et al., 1975], whereas Reich-manis in 1976 used a 6 6 array of 2 mm diameter steelelectrodes to produce a topographic representation ofelectrical conductance [Reichmanis et al., 1976]. Incontrast, Hyvarinen used two concentric electrodesa0.5 mm diameter inner electrode and a 2.5 mm diameterouter ring electrode that served as a control [Hyvarinenand Karlsson, 1977], while Poon et al. [1980] used anadhesive, conducting tape with high voltage intensities.This diversity in techniques accounts for why the resultsare neither readily comparable between studies norgeneralizable to all low-impedance points and controlson the human body.

Fig. 1. Study flow.

4 Ahn et al.

Bioelectromagnetics

Aut

hor P

roof

AT

AB

LE

1.

Stu

die

sQ1

Ele

ctri

cal

Ch

ara

cter

iza

tio

no

fA

cup

un

ctu

reP

oin

ts

Ref

eren

cesQ

2D

esig

nS

amp

leE

lect

rica

lcu

r-re

nt

Ele

ctro

de

Sit

eo

fte

stin

gC

on

tro

lR

esu

lts

Ev

iden

ced

irec

tio

n

Qu

alit

ysc

ore

(ou

to

f1

0)

Rei

chm

anis

etal

.[1

975

]Id

enti

fied

max

imal

con

du

ctan

cep

oin

tsw

ith

in1

cm2

area

atac

up

oin

tan

dco

ntr

ol

and

com

par

ed

frac

tio

nal

incr

ease

in

con

du

ctan

ce

7D

C,

1mA

0.2

cmw

ide

stai

nle

ssst

eel

wh

eel

17

acu

po

ints

on

PC

and

LI

mer

idia

nb

/wm

etac

arpophal

angea

lan

del

bow

join

t

N

earb

yan

atom

ical

lysi

mil

arlo

cati

on

2

ou

to

f6

PC

po

ints

and

3o

ut

of

11

LI

po

ints

had

sig

nifi

can

tfr

acti

on

alin

crea

sein

con

du

ctan

cein

all

7su

bje

cts

4

Rei

chm

anis

etal

.[1

976

]O

bta

ined

top

og

rap

hic

con

du

ctio

np

rofi

les

atac

up

oin

tan

dco

ntr

ol,

and

com

par

edco

nd

uct

ance

var

iance

10

DC

,2

V0

.2cm

36

stai

nle

ssst

eel

rod

sin

gri

dp

atte

rn3

.5

2.5

cm

10

acu

po

ints

TB

4

9,

Lu

5

8(o

nfo

rear

m)

2.5

2.5

cmn

earb

yp

oin

t

ascl

ose

asfe

asib

le

76

/10

0ac

up

oin

tlo

cish

ow

edin

crea

sed

con

du

ctan

cevar

iance

com

par

edto

con

tro

l>

5su

bje

cts

wit

hin

crea

sed

con

du

ctan

cevar

ian

ceat

all

10

acu

po

ints

4

Hy

var

inen

and

Kar

lsso

n[1

97

7]

Iden

tifi

edlo

wre

sist

ance

po

ints

on

fore

arm

and

han

du

sin

gco

nce

ntr

icel

ectr

od

e

5h

ealt

hy

mal

em

edic

alst

ud

ents

DC

,6

.7V

0.5

mm

dia

met

erci

rcu

lar

elec

tro

de

wit

h2

.5m

mco

nce

ntr

icre

fere

nce

elec

tro

de

Fore

arm

,h

and

s,ea

rsS

urr

ou

nd

ing

skin

(2.5

mm

rad

ius)

Rep

rod

uci

ble

low

resi

stan

cep

oin

tsw

ere

iden

tifi

edo

nh

and

and

ears

.P

oin

tsre

sem

ble

acu

po

ints

inlo

cati

on

3

Hy

var

inen

and

Kar

lsso

n[1

97

7]

Mea

sure

dim

ped

ance

of

low

resi

stan

cep

oin

tsan

dth

ear

eaw

ith

inth

eir

vic

init

y

5h

ealt

hy

mal

em

edic

alst

ud

ents

DC

,A

C;

50

0,

10

00

Hz

0.5

mm

silv

erw

ire

Fore

arm

,ea

rsS

urr

ou

nd

ing

skin

(2.5

mm

rad

ius)

Imp

edan

cep

eru

nit

area

was

50

-to

10

0-f

old

low

erat

low

resi

stan

cep

oin

tsco

mp

ared

toad

jace

nt

skin

1

0

10

0kO

vs.

2

3MO

,re

spec

tivel

y

3

McC

arro

llan

dR

ow

ley

[19

79

]

Det

erm

ined

wh

eth

erim

ped

ance

min

imu

mex

iste

din

a5

5g

rid

aro

un

dac

up

oin

t

8A

C,

1k

Hz,

4.5mA

1m

msi

lver

wir

ero

d,

chlo

rin

ated

7ac

up

oin

tso

nh

and

/arm

4

ou

to

f3

2co

llec

ted

sets

show

edd

ecre

ased

skin

imp

edan

ceu

po

nre

pli

cati

on

Dat

ash

ow

edte

mp

ora

lvar

iab

ilit

y

4

Po

on

etal

.[1

98

0]

Iden

tifi

ed

elec

troper

mea

ble

p

oin

tsu

sin

gta

pe

elec

tro

de

9A

C,

0.5

Hz,

0

18

V3

1in

chep

idu

ctiv

eta

pe

elec

tro

de

Fore

arm

al

on

gL

u,

PC

mer

idia

nN

/AC

on

du

ctiv

e

spo

ts

on

fore

arm

wer

eid

enti

fied

.S

po

tsli

eal

on

gm

erid

ian

,bu

tnot

clea

rly

asso

ciat

edw

ith

acu

po

ints

.N

og

ener

alp

atte

rnac

ross

sub

ject

s

3

Fal

ket

al.

[20

00

]M

easu

red

2

2g

rid

imp

edan

ces

at

acti

ve

v

s.co

ntr

ol

zones

and

com

par

edm

inim

um

imp

edan

ces

b/w

zones

34

h/o

coca

ine

abu

seo

nm

eth

adon

e;1

7M

,1

7F

AC

,5

Hz,

2.5mA

1m

mA

g/A

gC

lp

rob

e4

acti

ve

ear

zon

es(s

hen

men

,sy

mp

ath

etic

,li

ver

,lu

ng

)

4co

ntr

ol

zon

eso

nh

elix

of

ear

Low

est

imp

edan

ceval

ues

fou

nd

wit

hin

acti

ve

zon

esw

ere

sig

nifi

can

tly

low

erth

anth

ose

wit

hin

contr

ol

zon

es.

Act

ive

1.3

6v

s.C

on

t1

.97

MO

(P