Delpeuch, Francis

Dupuy, R.P.

Gartner, Agnès

Maire, Bernard

Rieu, D.

Sarda, P.

Horizon / Pleins textes

1067 
analyses. Contrary to Abernathy's assertion, smoking is quite 
unlikely to account for the increased mortality in heavier people 
because in virtually all studies heavier people have smoked less 
than thin people. 
Although Abemathy would prefer to discard height and weight 
tables, the excess mortality,and morbidity associated.with over- 
weight is not eliminated just by dismissing the tables. We concur 
that long-term weight loss for obese people is seldom achieved. 
This is all the more reason to have clear and sound weight guide- 
lines that can be used as a criteria for avoiding weight gains as 
we age. Clearly, the focus must be primarily on prevention of 
weight gain rather than on treatment after it has already occurred. 
Waller C f i  Ï l l m  
Meir StaiiipJer 
J o h n  Manson 
Harvard School of Public Health 
Department of Nutrition 
665 Huntington Avenue 
Boston. MA O2 I 15 
Importance of electrode position in bioelectrical impedance analysis 
Cote t 0 
, Dear Sir: 
Mayfield et al (1) recently used two reference methods (H2'*0 
and bromide dilution) to demonstrate that resistance and re- 
actance in newborns are correlated with total body water and 
extracellular water, respectively. This work represents an im- 
portant step forward in the application of bioelectrical impedance 
analysis (BIA) in young children because it is the first to propose 
predictive equations for aqueous body compartments. Unfor- 
tunately, these equations can only be used by teams that use the 
same positions for the four electrodes. However, no standard 
position has yet been established in young children and it is of 
great importance to consider this parameter. 
The majority of BIA measurements use a tetrapolar system 
t o  minimize skin reactions caused by the adhesive electrodes. 
To measure total body impedance, a pair of electrodes is placed 
at  the extremity of the upper limbs and another pair a t  the ex- 
tremity of the lower limbs. Current is applied between the hand- 
and foot-signal electrodes and the resistance (R) to the current 
detected between the sensor electrodes of each pair. Because 
impedance is related to the length of the conductor, the mea- 
surement of R is therefore closely linked to the position of the 
electrode pairs. 
In adults the most widely used method uses standard electrode 
positions on the back of the hands and feet: the signal electrodes 
are placed on the phalanges and the sensor electrodes just beneath 
a line between the prominent bones of the wrist and  the ankle. 
This position is such that the sensor electrode is always placed 
at  exactly the same anatomical site and there is always 2 5 cm 
between the two electrodes of the pair. Note that the English 
Holtain device uses other sites for electrode application in adults: 
the signal electrode is placed on the wrist and ankle articulation, 
and the sensor electrodes between 3 and 5 cm farther along the 
a rm and 4 cm along the leg. It is unfortunate that different sites 
are used because this compromises any attempt to  compare R 
values. 
The  standard sites used in adults are too close together in 
young children and can lead to an interaction between the elec- 
trodes in each pair. Of the teams that have already published in 
this field, some have tested different sites (2) or indicated the 
sites used (1, 3-6), but others have not given any indication of 
electrode position (7, 8). These studies in children were per- 
formed by using direrent application sites. 
In newborns Mayfield et al (1) used the same electrode posi- 
~ tions as in adults. The resulting interaction could explain the 
elevated R values they obtained. which were higher than those 
we recorded in newborns (A Gartner, P Sarda, RP Dupuy, B 
i 
Maire, F Delpeuch, D Rieu, unpublished data presented at the 
Sixth International Congress of Auxology in Madrid, 199 I ) .  
Mayfield et al report R values > 1000 Q, which is incompatible 
within the context of BIA standardization in that the machines 
used have a measurement range of between O and 1000 Q. 
The positioning of the various electrodes has never been tested 
in newborns. To  perform these tests we positioned the electrodes 
as for adults and added six electrodes side by side on the arm 
and leg in fixed numbered positions, something that is easier to 
d o  in newborns. The  electrodes were 1.2 cm wide. The R values 
we obtained (Fig 1) with adult positions (positions 1 and 2) were 
in the same region as R values obtained by Mayfield et al (1). 
The farther the selected sensor electrode from the signal electrode, 
the more R values decreased. The interaction tested with the 
sensor electrode in position 8 disappeared as soon as the signal 
electrode moved toward the fingers (Fig I) .  
These conclusions were similar to those found by Barillas- 
Mury et al (2), who performed the same tests in  young children. 
According to them the minimal interelectrode distance is 5.5 
cm. A child's hand is not sufficiently large for such a distance 
to be used and this led to  the proposal that electrode application 
could be extended in young children to the forearm and the leg. 
Subsequent BIA studies performed by this team in children used 
a distance of 6 cm from the signal electrodes placed on the wrist 
and ankle articulations (5,6).  This is the site that we used recently 
for the study in newborns. 
Two BIA studies in young children (3, 4) were performed 
with the signal electrode placed in the adult position on the 
phalanges and the sensor electrode 3 or 4 cm farther along the 
hand and the foot. The  authors found that a minimal distance 
of 3 cm was necessary (3) but they used a test that, to  us, seems 
unclear. The effect of electrode position on the measurement of 
R was tested by incfeasing the distance between the fixed-signal 
elec.trode and the mobile-sensor electrode by steps of 0.5 cm. 
The results (expressed as a percentage ofthe smallest value mea- 
sured) showed that a plateau was reached. However, in such a 
test in which the sensor electrode is moved, R decreases contin- 
uously and the smallest value measured is that obtained with 
the largest distance tested. It is not possible to obtain a plateau 
under these conditions. 
Growth references from the National Center for Health Sta- 
tistics and the Centers for Disease Control are currently being 
revised and the measurements planned include BIA in children 
aged 2 12 y (9). It is therefore important to  define electrode 
position in this case so that measurements performed today can 
be compared with the future reference. 
In conclusion, electrode 
1068 LETTERS TO THE EDITOR 
---a 
, -  . ~ -*-+ -i -3 
. ..&-a . - .--* 
c 
The effect of sensor position 
with fixed signal at position 1 
The effect of signal position 
With fixed sensor at position 8 - " -:.-* 
- -:e " _I 
Resistance (ohms) 
1100 - 
300' I '  " " " 
1 2 3 4 5 6 7 8  
--a - . 1  
- i  
_. .... -w,- Resistance (ohms) 
I -  * 1   
470 
S 
e 
420 I S 
3701 
$20'  I '  " ' I " 
1 2 3 4 6 6 7 8  
position of the  sensor electrode position of the signal electrode 
FIG I .  Effect of electrode position on bioelectrical impedance analysis measurement in newborns. Resistance was 
measured by using an AKERN (Firenze, Italy) analyzer. Positions I and 2 correspond to the standard positions in 
adults. The other positions correspond to electrodes (1.3 cm wide) placed side by side along the arm or leg from 
position 2 and above. The sensor electrode at position 8 was 6 cm from position 2. The value 999 LI is the maximum 
of the machine. 
of the sensor electrode, is one of the most critical factors in BIA 
measurements. Standard electrode positioning must at least de- 
scribe an anatomic site for one of the electrodes and the precise 
distance that separates the electrodes within each pair. To date, 
a small number of BIA studies in young children have been 
published but with large variations in electrode position. Stan- 
dard electrode positions in young children have now become 
indispensable. Studies should be performed to test and compare 
possible sites and result in the definition of a single standard., 
This step forward in the application of BIA measurements in 
young children is indispensable to allow R values to be compared 
and thus lend more weight to  the results obtained and increase 
interest in studies using BIA in young children. 
Agnès Gartner 
Bernard Maire 
Francis Delpeirch 
Laboratoire de Nutrition Tropicale 
UR 4 F  du Département Santé de I'Orstom 
BP 5045 
34032 Montpellier Cedex, France 
Pierre Sarda 
Renée Pierre Dtipiiy 
Daniel Rieii 
Service de Pédiatrie II 
Hôpital St Charles 
34059 Montpellier Cedex, France 
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. weight infants determined by.using bioelectrical resistance and re- 
actance. Am J Clin Nutr 1991;54:296-303. 
2. Barillas-Mury C, Vettorazzi C, Molina S, Pineda O. Experience with 
bioelectrical impedance analysis in young children: sources of vari- 
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No rep1.v was receivedfrom SR 1Mayfield. 


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