Textile electrode straps for wrist-to-ankle bioimpedance measurements for Body Composition Analysis. Initial validation & experimental results.
ABSTRACT Electrical Bioimpedance (EBI) is one of the non-invasive monitoring technologies that could benefit from the emerging textile based measurement systems. If reliable and reproducible EBI measurements could be done with textile electrodes, that would facilitate the utilization of EBI-based personalized healthcare monitoring applications. In this work the performance of a custom-made dry-textile electrode prototype is tested. Four-electrodes ankle-to-wrist EBI measurements have been taken on healthy subjects with the Impedimed spectrometer SFB7 in the frequency range 5 kHz to 1 MHz. The EBI spectroscopy measurements taken with dry electrodes were analyzed via the Cole and Body Composition Analysis (BCA) parameters, which were compared with EBI measurements obtained with standard electrolytic electrodes. The analysis of the obtained results indicate that even when dry textile electrodes may be used for EBI spectroscopy measurements, the measurements present remarkable differences that influence in the Cole parameter estimation process and in the final production of the BCA parameters. These initial results indicate that more research work must be done to in order to obtain a textile-based electrode that ensures reliable and reproducible EBI spectroscopy measurements.
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ABSTRACT: BACKGROUND/OBJECTIVES: Functional garments for physiological sensing purposes have been used in several disciplines, that is, sports, firefighting, military and medicine. In most of the cases, textile electrodes (textrodes) embedded in the garment are used to monitor vital signs and other physiological measurements. Electrical bioimpedance (EBI) is a non-invasive and effective technology that can be used for the detection and supervision of different health conditions.EBI technology could make use of the advantages of garment integration; however, a successful implementation of EBI technology depends on the good performance of textrodes. The main drawback of textrodes is a deficient skin-electrode interface that produces a high degree of sensitivity to signal disturbances. This sensitivity can be reduced with a suitable selection of the electrode material and an intelligent and ergonomic garment design that ensures an effective skin-electrode contact area. SUBJECTS/METHODS: In this work, textrode functional straps for total right side EBI measurements for body composition are presented, and its measurement performance is compared against the use of Ag/AgCl electrodes. Shieldex sensor fabric and a tetra-polar electrode configuration using the ImpediMed spectrometer SFB7 in the frequency range of 3-500 kHz were used to obtain and analyse the impedance spectra and Cole and body composition parameters. ResulTS: The results obtained show stable and reliable measurements; the slight differences obtained with the functional garment do not significantly affect the computation of Cole and body composition parameters. CONCLUSIONS: The use of a larger sensor area, a high conductive material and an appropriate design can compensate, to some degree, for the charge transfer deficiency of the skin-electrode interface.European Journal of Clinical Nutrition 01/2013; 67(S22-7):10.1038/ejcn.2012.161.. · 2.95 Impact Factor
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ABSTRACT: Patient biopotentials are usually measured with conventional disposable Ag/AgCl electrodes. These electrodes provide excellent signal quality but are irritating for long-term use. Skin preparation is usually required prior to the application of electrodes such as shaving and cleansing with alcohol. To overcome these difficulties, researchers and caregivers seek alternative electrodes that would be acceptable in clinical and research environments. Dry electrodes that operate without gel, adhesive or even skin preparation have been studied for many decades. They are used in research applications, but they have yet to achieve acceptance for medical use. So far, a complete comparison and evaluation of dry electrodes is not well described in the literature. This work compares dry electrodes for biomedical use and physiological research, and reviews some novel systems developed for cardiac monitoring. Lastly, the paper provides suggestions to develop a dry-electrode-based system for mobile and long-term cardiac monitoring applications.Physiological Measurement 08/2013; 34(9):R47-R69. · 1.50 Impact Factor
- Journal of Electrical Bioimpedance. 07/2013; 4:38.
Abstract— Electrical Bioimpedance (EBI) is one of the non-
invasive monitoring technologies that could benefit from the
emerging textile based measurement systems. If reliable and
reproducible EBI measurements could be done with textile
electrodes, that would facilitate the utilization of EBI-based
personalized healthcare monitoring applications. In this work
the performance of a custom-made dry-textile electrode
prototype is tested. Four-electrodes ankle-to-wrist EBI
measurements have been taken on healthy subjects with the
Impedimed spectrometer SFB7 in the frequency range 5 kHz to
1 MHz. The EBI spectroscopy measurements taken with dry
electrodes were analyzed via the Cole and Body Composition
Analysis (BCA) parameters, which were compared with EBI
measurements obtained with standard electrolytic electrodes.
The analysis of the obtained results indicate that even when dry
textile electrodes may be used for EBI spectroscopy
measurements, the measurements
differences that influence in the Cole parameter estimation
process and in the final production of the BCA parameters.
These initial results indicate that more research work must be
done to in order to obtain a textile-based electrode that ensures
reliable and reproducible EBI spectroscopy measurements.
n recent years, research and development efforts spent on
functional textile and materials have positioned textile
technology as an enabling element in personalized
healthcare monitoring applications [1, 2]. Several of the
afore-mentioned efforts have been focused on the use of
textile electrodes for non-invasive monitoring [3-5].
Measurements of Electrical Bioimpedance (EBI) have
been used in several health care applications such as
cardiovascular health monitoring , Body Composition
Manuscript received April 1, 2010. This work was supported in part by
the Mexican Conacyt under Scholarship 304684.
J.C. Márquez is with the Department of Signals & Systems at Chalmers
University of Technology and with School of Engineering at the University
of Borås, 501 90 SWEDEN (phone:+46334354630; fax: +46334354408,
J. Ferreira is with the School of Engineering at the University of Borås,
501 90 SWEDEN (firstname.lastname@example.org)
F. Seoane is with the School of Engineering at the University of Borås,
501 90 SWEDEN and the Department of Signals & Systems at Chalmers
University of Technology. (email@example.com).
R. Buendia is with the School of Engineering at the University of Borås
and with the Department of Signal Theory and Communications at the
University of Alcala, ES-28871, Madrid, SPAIN (firstname.lastname@example.org)
K Lindecrantz is with the School of Engineering at the University of
Borås and the School of Technology and Health at Royal Institute of
Technology, SE-141 52 Huddinge, SWEDEN. (email@example.com)
Analysis (BCA) for nutritional assessment  or monitoring
body fluid balance in peritoneal dialysis patients .
EBI applications for home health monitoring would be
greatly facilitated if textile based systems for instants
integrated in cloths or furniture could produce reliable
measurements. The availability of such textile-integrated
measurement systems would, not only improve the comfort
for the patients, but also help to place the sensing electrodes
in the same position in a reliable manner.
EBI measurements taken with textile electrodes for BCA
have been shown possible  and even good performance
when producing spectroscopy measurements [8, 9]. To fully
exploit the versatility that comes with textile based
electrodes they should preferably function without use of
electrode gel or other additional electrolyte. However, the
use of dry electrodes is very likely to reduce the quality of
the signals, and the aim of the presented study is to assess
Thus, a textile prototype to perform EBI measurements
for total BCA has been built and its performance has been
experimentally tested and compared with the measurements
taken with electrolytic gel electrodes.
II. MATERIAL & METHODS
A. Measurements & Analysis
measurements for Body Composition Analysis have been
performed with 4-electrodes from the wrist to ankle as
shown with Fig. 1. The EBI measurements were taken with
Impedimed electrolytic and textile electrodes in 3 healthy
subjects lying supine in a resting state.
Bioimpedance Spectroscopy (EBIS)
Fig. 1. Textile electrodes prototype placement.
The EBIS measurements were made with the Impedimed
Textile Electrode Straps for Wrist-to-Ankle Bioimpedance
Measurements for Body Composition Analysis. Initial Validation &
J. C. Marquez, J. Ferreira F. Seoane, R. Buendia, and K. Lindecrantz
SFB7 spectrometer in the frequency range 5 to 1000 kHz.
1) EBI Spectral Analysis
A set of 20 complex EBI measurements was taken for
each subject with both types of electrodes. The mean of the
reactance and resistance spectra obtained for each of the
subjects and type of electrode has been studied.
2) Measurement Correction
The performed EBIS measurements may be influenced by
parasitic capacitances. Therefore the obtained susceptance
has been analyzed to test for capacitive artifacts and if
present, it has been removed using a correction function
3) Cole Model & Body Composition Analysis
BCA parameters, Total Body Water (TBW), Intra Cellular
Fluid (ICF), Extra Cellular Fluid (ECF), and Fat Free Mass
(FFM), and the Cole model parameters Resistance at zero
frequency (R0), Resistance at infinite frequency (R∞), as well
as the characteristic frequency fC have been calculated with
the BioImp software.
1) Textile prototype hand-wrist & foot-ankle
• Hand-wrist: variable width & adjustable length up
to 60 cm with adjustable Velcro fasteners and
snap-buttons. Containing two textile-electrodes
of 32 and 90 cm2, black fabric in Fig. 2.
• Foot-ankle: 7 cm width & adjustable length up to
53 cm with adjustable Velcro fasteners and snap-
buttons. Containing two textile-electrodes of 163
and 117 cm2, black fabric in Fig. 2.
• Inner surface, sensor: Synthetic wrap knitted
textile material with silver fiber as a conductive
element. Sensor Manufactured by Clothing+.
Fig. 2. Foot-Ankle strap, up, and Hand-Ankle Textile-electrode prototype.
2) Impedimed Electrodes
• Area: 5.75 cm2
• Inner surface: adhesive conductive gel, electrode
manufactured by Impedimed ltd.
A. Complex EBI Spectrum
The averaged resistance and the reactance spectra of the
measurements taken on one of the subjects are shown in Fig.
3 and 4 respectively. Both plots show the EBI data obtained
with the electrolytic electrodes with solid line, while the EBI
data obtained with the dry textile prototype is shown using
the trace with circular markers. The trace with point maker
shows the EBI data obtained after correcting the capacitive
influence present on the textile measurement.
Fig.3. Resistance Spectrum measured with Impedimed and
Textile electrodes after and before correction for subject 2
Fig.4. Reactance Spectrum measured with Impedimed and
Textile electrodes after and before correction for subject 2
The plots in Fig. 3 show that the resistance obtained with
both types of electrodes present a similar frequency
dependency but a noticeable difference in the magnitude.
The resistance obtained with the textile electrodes exhibits
considerable lowers values and this is seen for the resistance
in all 3 subjects.
The reactance spectra plotted in Fig. 4 present a
remarkable difference at frequencies lower than 100 kHz.
The characteristic frequency of the impedance taken with
the textiles is shifted towards higher frequencies.
B. Measurement Correction
In Fig. 4 is possible to see the difference between the
measurement taken with the textile, solid trace with circular
marker, and its correction with solid trace and point marker.
Table I contains the mean values estimated for the
parasitic impedance for the measurements taken with the
textile electrodes. The Standard Deviation (S.D) is also
indicated. Note that no parasitic capacitance was found for
the measurement taken with the electrolytic electrodes.
MEAN VALUE AND STANDARD DEVIATION OF THE PARASITIC
CAPACITANCE CORRECTED IN THE TEXTILE ELECTRODES
MEAN VALUE OF THE COLE PARAMETERS OBTAINED WITH THE IMPEDIMED
ELECTRODES AND THE TEXTILE ELECTRODES
R0 (Ω Ω)
Subject gel Textile gel
1 559,19 473,91 352,22
2 592,01 514,76 386,24
3 671,81 536,13 445,46
N.B. The data showed for the textile electrode is after the correction
R∞ (Ω Ω)
C. Cole Parameters
In Table II is possible to observe that the mean value of
both R0 and Rinf estimated from the textile EBI
measurements are remarkable smaller than the values
obtained from the EBI measurements taken with electrolytic
electrodes for all 3 subjects. Notice that in the case of the
parameter fC the estimated value is higher.
D. Body Composition Parameters
The mean of the parameters for BCA estimated from the
performed EBI measurements are listed in Table III. Notice
that the ICF parameter is not indicated since it is equal to 1-
MEAN VALUE OF THE BODY COMPOSITION PARAMETERS OBTAINED WITH
THE IMPEDIMED ELECTRODES AND THE TEXTILE ELECTRODES CORRECTED
TBW (%) ECF (%)
Subject gel Textile gel
1 56,86 57,64 40,54
2 51,32 53,89 41,88
3 57,88 56,84 42,51
N.B. The data showed for the textile electrode is after the correction
A. Influence of dry textile electrodes in the measurement
Standard Ag/AgCl electrodes use conductive gel that
reduces the electrode polarization impedance, Zep,
facilitating the electron transfer between the measurement
system and the body, thus improving the electrical interface
between the electrode and the body. As we use dry textile
electrodes, it is expected that measurements will give a
larger value of Zep. Such an increment in the value of Zep
increases the total impedance of the electrical pathway in
series with the measuring load and making the EBI
measurement more susceptible to the presence of parallel
parasitic capacitances . In this way the current through
the measuring load decreases and the smaller voltage than
expected yields an underestimation of the measured
impedance. The effect would be more pronounced at higher
frequencies than lower, and this may be the reason behind
the under estimation of R∞.
The presence of a parasitic capacitance in parallel with the
load creates a current divider that increasing the capacitance
of the EBI measurement. This parasitic capacitance is
accountable for the shift towards higher frequencies of the
characteristic frequency, seen in Fig. 4. It is likely that the
parasitic capacitance is underestimated, since estimating it
from susceptance requires enough measurement points taken
at high frequencies.
Wetting the electrodes has shown to improve the
performance on EBI spectroscopy measurements, even when
the electrolyte comes from the own sweet , the
improvement in the performance is noticeable within
minutes. Therefore just by waiting some time certain
improvement on the EBI measurement could be obtained.
The structure on the surface of the textile electrode 
and the pressure on the electrode  can also reduce the Zep.
B. Influence of a large current injecting area
Since textile electrodes are dry, it was expected that
without wetting the electrodes or preparing the skin no EBI
spectra would be obtained at all, but to our surprise EBI
measurements were taken straight away with the dry
electrodes. This is due to the large area of contact of each
electrode, which is several times larger that the contact area
of the electrolytic electrodes or the textile electrodes
previously used in [8, 11].
The area together with the placement around the wrist,
hand, foot and ankle also contributes to reduce the influence
the constriction area on the EBI measurement. In standard
electrodes the current injected into the body is concentrated
near the contact area defined by the electrode. This current
concentration reduces the effective volume used by the
electrical current to flow through the portion of the body in
the constriction area producing a larger impedance. Using a
large electrode with a surface surrounding the limbs will
cause a more homogeneous current distribution maximizing
the effective conductive volume use by the measuring
current near the injecting electrodes reducing the
constriction and producing a slightly smaller impedance.
This reduction of the constriction area would explain the
observation of obtaining smaller values of impedance with
the dry textile electrodes than with the electrolytic at all
frequencies, especially at low.
C. Cole & BCA parameters
The aforementioned presence of the parasitic capacitances
and the large contact area of the textile electrodes cause the
observed deviation in the impedance spectroscopy data.
Such deviation influences in a noticeable manner the
estimation of the Cole and the BCA parameters.
V. CONCLUSION & FUTURE WORK
Even if the obtained results show that it is possible to
obtain EBI spectroscopy measurements with dry textile
electrodes, the obtained spectroscopy measurements present
differences that influence on the Cole and BCA parameters.
Whether the differences are due to the extended electrode
area of the textile prototype or due to larger Zep of the textile
electrodes, it is not completely clear. This work initially
suggests that dry textile electrodes might be able to be used
for obtaining EBI spectroscopy measurements, but at this
stage it is not clear if textile electrode can be used for
assessment on body composition since reliable Cole.
parameters cannot be obtain from the EBI measurements.
To increase the reliability of the estimation of the Cole
parameters from dry textile electrodes measurements
deviation-free EBI spectroscopy measurement must be
obtained. Experiments focused to identify the causes of the
differences observed in the spectroscopy EBI data are being
done and preliminary results indicate that effective
conductive area of the textile material and the robustness of
the method to estimate the Cole parameters will play an
important role in obtaining reliable EBI measurements and
accurate estimations of the BCA parameters.
The availability of a textile garment integrated EBI
spectroscopy measurements would allow the implementation
of EBI-based monitoring systems of body fluid distribution
that could shift care approaches for patients under dialysis
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