Open Journal of Applied Sciences, 2012, 2, 128-134
doi:10.4236/ojapps.2012.23018 Published Online September 2012 (http :/ /
Biomagnetic Validation to Skin Level for Blood Pressure
Curves and Venous
T. Cordova-Fraga1*, Francisco Gómez-Aguilar1, T. Bravo-Arellano1, M. A. Hernández-Gonzalez2,
S. Solorio-Meza2, H. A. Perez-Olivas1, M. Sosa-Aquino1, J. J. Bernal-Alvarado1,
C. R. Contreras-Gaytan3
1Departamento de Ingeniería Física—DCI, Universidad de Guanajuato Campus León Loma del Bosque, León, México
2Unidad de Investigaciones Médicas, Los Paraísos, León, México
3Facultad de Ingeniería en Computación y Electrónica, Universidad De La Salle Bajío Campus Campestre,
Lomas del Campestre, León, México
Email: *, theoco rdo
Received May 31, 2012; revised June 28, 2012; accepted July 12, 2012
An analysis of the reproducibility from signal record bioelectric heart activity is presented. The measurements were
carried out with a recently patented medical device, which one is able to record the curves of pressure arterial and ve-
nous as those obtain ed using th e gold standard tech nique in these evalu ation s, the card iac catheterization techn ique. The
measurements were carried out 15 health subjects and patients; each one was measured 5 times in order to have
auto-correlations and correlations of these records. Analysis indicates correlations from 0.9 to 1 as long as p values
were below 0.05. It is indicated an excellent reproducibility of ev aluated patients.
Keywords: Bioelectric Heart Activity; Curves of Pressure Arterial and Venous; Correlation Coefficient; Statistical
1. Introduction
The arterial and venous pressures are values attributed to
blood flow through human body [1,2]. As far as it is
known, the first record about blood circulation existence
was performed in China by Nei Ching, 2600 years a. C.
[3] Although Miguel Servet made the first description of
pulmonary circulatory system [4]. Later, William Harvey
raised the pri nciple of hem ody nam ics to veri fy that the heart
muscle had phases of movement and rest [5]. Poiseuille
used a pr essure gauge in an imals to eva luate the pre ssure
in units of mmHg [6], Faivre used the Poiseuille he-
modinamometer on a human being to measure intra-
arterial pressure [7].
Some non-invasive studies have shown that hemo-
dynamic forces have a relationship with the pulse pres-
sure [8]. It has also been noted that with age, it is
increased cardiovascular risk, and it is directly related to
aortic pressure increase [8-12]. Currently there are two
methods of clinical routine use for measurement of blood
pressure and only one to record venous pressure: cardiac
catheterization and sphygmomanometer to arteries. The
second one is widely used, however provides a register
subjective due to its nature. As long as, the technique of
cardiac catheterization is able to record venous pressure
in their inside, it is considered the gold standard in these
assessments, despite it is widely invasive and it demands
high trained personnel and special patients areas for
implementation [9 ]. Nevertheless, it pr esen ts an obj ectiv e
In this paper, it is presented the validation of records
on blood pressure in healthy subjects and patients. It has
been used a device recently patented, the pulse pressure
cardiac gauge (PPC). This diagnostic and monitoring
device is able to have a distinction of recording of the
curves shape of pressure of arterial and venous as those
recorded by catheterization, it offer an express evaluation
with the advantage of carrying out the valuation on skin
level; the ionizing radiation is avoided and does not
require a sterile room for evaluation.
2. Methodology
Each one of the patients enrolled in this study gave a
written consent previous to carrying out measurements,
which were performed according to the treaty of Helsinki
for studies in humans. These assessments did not present
any risk or exposed the patient to any ionizing radiation.
To each volunteer was asked to be placed in semi-fowler
position with the head turned to the right, then the artery
*Corresponding a uthor.
Copyright © 2012 SciRes. OJAppS
or vein was identified by palpation and auscultation, this
is, the location of the internal jugular vein and common
carotid artery as shown in Figure 1; when the right
location under skin of artery or vein is done, on skin is
placed a magnetic marker (a magnet of 3 × 4 mm, diameter
and height, respectively), then, it is fixed the sensor base
of the PPC in contact with the skin. Without exerting
more pressure that the base and the magnetic sensor
weight on the neck of the person, the magnetometer is
always separated a distance of 2.5 cm from magnetic
marker on patient skin. This magnetic marker is light
enough not to crush the vessel but has the intensity of the
magnetic moment sufficiently intense, µ = 0.13 Am2.
Magnetic signal is registered with an excellent signal/
noise rate, such it is not required filtering digital addi-
tional so that the detected signal is read.
Mechanical action by the flow of blood in the v essel is
transmitted to magnetic marker. So, it generates a variable
magnetic field which increases as it approaches the sen-
sor having variability in time and decreases away from
this one.
In this validation study were measured 10 healthy sub-
jects, all with no history of heart disease and 5 patients
who underwent cardiac catheterization for suspected
coronary artery disease, while they were registered with
the cardiac catheter. So, after placing the magnetic
marker, it was measured pressure curves repetitively
every 30 seconds according to following order: 5 records
for aspiratory inhalation and 5 records for aspiratory ex-
halation. It was asked an apnea around of 30 s. These
measurements were performed on the left side of the
neck and suprasternal area, some of them also included
alternate position: semi-fowler and supine.
Validation of the obtained signals is carried out esti-
mating the correlation coefficient of the reproducibility
of the signal (cross-correlation of a signal with itself)
using mathematical procedures for processing biological
signals, first among the same individual (auto-correlation)
and then correlate measurements between healthy sub-
jects and patients.
3. Results
The first part of the measurements performed with the
PPC device shows an excellent behavior of the pulse
waves from arterial and venous, see Figures 2 and 3; it is
a stage of apnea where it is shown the wave morphology
of the artery and vein of the pulses according to the
physiological theory of the cardiac cycle, this was done
in healthy subjects.
A typical blood pressure waves recorded with the PPC
in an apnea segment is shown in Figure 4.
The positive waves of pulse venous coincide with a
delay or with the reverse of the flow, while each de-
pression indicates an acceleration of venous return.
When contracting the right atrium (RA), the blood cannot
enter the right ventricle (RV) flows back to the vena cava,
resulting in venous pulse wave. The wave “a” is pro-
duced by the contraction of the RA in a presystolic
period; the wave “c” occurs immediately after the wave
a” and at the beginning of “x”, is produced by inter-
ference in the carotid arterial pulse, see Figure 5.
Figure 1. Schematization of magnetic marker position on
subject skin, it is right over jugular artery.
Figure 2. Arterial pressures register on suprasternal region
for a healthy subject and stage of apnea in the supine position.
Figure 3. Pressure waveform in internal jugular artery, it
was recorded with two stages: breathing and apnea. Similar
pattern is repeated for a blood pressure pulse, at the stage
of apnea the signal present pattern de fined according to the
morphology searched.
Copyright © 2012 SciRes. OJAppS
Figure 4. Typical pressure wave recorded, using the PPC
device, on zone suprasternal in supine position with brea-
thing noise. In the curve is reached to clearly distinguish
three points of interest, dicróticas waves due to backflow of
blood as well as maximal and minimal corresponding to the
systolic pressure (SP) and diastolic pressure (DP) as the
cardiac cycle.
Figure 5. Waveform pressure recorded from the internal
jugular vein, taken on the left side of the neck, in a healthy
subject in inspiratory apnea phase and semi-fowler position.
Note the characteristic morphology “a”, “c”, “v”, and de-
clines calle d “x” and “y”.
The sine “x” is one of the predominant decreases, oc-
curs during diastole atrial due to pressure drop in the
atria, then follows the wave “v”, due to increased atrial
filling pressure right under the return of blood through
the vena cava and finally the depression “y” is produced
because the pressure in the RA descends to the open
tricuspid valve in the relaxation phase in the filling
period RV.
When the registration is made by reversing the polarity
of the magnet there is an inversion of the curves and
venous blood pressure in the temporary space, the Figure
6 shows the case of arterial register, there are the same
waveforms with an inverted orientation only.
For the standardization ph ase, waveforms are obtained
for healthy subjects, see Figures 7 and 8. The records
have the following identification: ica (internal carotid in
apnea aspiratory), ici (internal carotid in apnea inspiratory),
ija (internal jugular in apnea aspiratory) and iji (internal
jugular in apnea inspiratory). Measurements in the
suprasternal area with two variants are: saa (suprasternal
in apnea aspiratory) and sai (suprasternal in apnea inspi-
Figure 6. Waveform pressure from suprasternal area, in a
healthy subject, at the stage of apnea aspiratory and supine
position. It shows the morphology characteristic of the
curve of blood pressure.
Figure 7. Pressure waves ica, ija and saa, superimposed on
the phase of respiration in apnea aspiratory for the same
subject. The pressure in ica and ija are in semi-fowler
position, while the saa is supine. Note the difference in
amplitude, and morphological consistency that emerges as
the cardiac cycle, regardless of the different areas where
each record was taken, this is mentioned for blood pressure
supine and semi-fowler.
Copyright © 2012 SciRes. OJAppS
3.1. Statistical Analysis
A statistical analysis was performed in order to deter-
mine correlation between the pressure differences (Pd)
measures in mmHg obtained with the digital sphygmoma-
nometer standardization in healthy subjects and voltage
differences (Vd) for the PPC, Figure 9. At the same time
is the correlation for values of PPC and cardiac catheteri-
zation, see Figure 10. Using the correlation coefficient
model of Pearson, Spearman, and Kendall. Also per-
forms a linear fit for both cases, which is shown in Ta-
bles 1 and 2.
3.2. Repeatability and Reproducibility Test
For repeatability tests between measurements, there is a
phase shift in the signals, so that, to establish their corre-
lation between them, the area under the curve of each
signal was estimated and establishing an area correlation
see Figure 11. Subtracting point to point from the curves
Figure 8. Pressure waves ici, iji and sai, superimposed on
the phase of respiration in apnea aspiratory for the same
subject. The pressure in ici and iji are in semi-fowler position
while the sai is supine. Note the difference in amplitude.
Figure 9. Adjustment of correlation PPC vs. sphygmoma-
nometer in the suprasternal zone in supin e in h ealthy sub jects.
Figure 10. Adjustment of correlation PPC vs. catheteriza-
tion in the suprasternal zone in supine in healthy subjec t s.
Table 1. Summary of correlation results PPC vs. blood pres-
sure and linear regression.
Fitting curve: y = ax + b dV[V] = 0.98x + 9.4
Pearson Spearman Kendall
Corr. Coefficient r = 0.91 p = 0.92 τ = 0.82
Table 2. Summary of correlation results PPC vs. catheteri-
zation and linear regression.
Fitting curve: y = ax + b dV[V] = 0.9x + 12.8
Pearson Spearman Kendall
Corr. Coefficient
r = 0.95 p = 0.91 τ = 0.79
Figure 11. Area under the curve for the set sai.
integrated, there are correlations over 0.9 and p values
well below 0.05. Obtaining an excellent correlation and
thus validating the measurements using this device.
Copyright © 2012 SciRes. OJAppS
3.3. Hemodynamic Study and Calibration
In the cardiac catheterize lab of highly specialized medi-
cal unit (HSMU) No.1 at the Mexican Social Security
Institute (IMSS), printed data were obtained from the
pressure curves recorded by catheterization in 7 patients.
The Figure 12 shows one of the curves obtained simul-
taneously with the PPC and the polygraph in a cardiac
catheter intervention, consi dering the gold st andard.
4. Discussion
PPC is a device which measures variations in the in-
tensity of a magnetic field generated by a magnetic
marker at a fixed distance from a transducer that converts
mechanical movement to analog signals and a source to
amplify the signals recorded, filter, and stored in a com-
puter as digital signal, becoming text file for further
study and manipulation. Each of the elements constituting
the complete device are easy to transport and install in
any area where it is required to measure, only consists of
a horseshoe that supports the sensor connected to a
flexible tube attached to a microphone stand for easy
positioning at the time of measurement and a computer
with the software needed to acquire the data.
Because of the magnetic field measurements provide
a good approximation to see the angular dependence
exists around a coaxial cable or a cylindrical permanent
magnet, it is the possibility to register the oscillations of
a source for a determined distance. This measurement
modalities relates the blood pressure carried by the
conduits different called vessels and they are divided
according to their morphology and function in arteries,
veins and capillaries, wh ich not being rigid conduits tend
to contract and expand due to the strength that is against
the walls to resist the flow of blood pumped by the heart,
and this motion due to it is soft waves can be recorded by
the PPC successfully locating the vessel to be measured.
Figure 12. Superposition of signals obtained with the PPC
and polygraph and made the switch from units of volts to
The PPC device provides informatio
millimeters of mercury in the PPC signal.
n (voltage-time)
s of
pr robic/
nd to
forms o btained w ith the PPC are very sensitiv e
e protocol to PPC shows that
ents to the same test subject was
out the compliance of the arteries or veins. The maxi-
mum value of each wave equals the pressure systolic and
the minimums is equal to pressure diastolic, while the
decrease or dicrotic wave is related to the backflow of
blood, thus has a new way of measuring the patient’s
health status, graduating flexibility and arterial diameter
with the pressure non-invasively and continuously.
The PPC has a good correlation “0.9r” value
essure vs. sphygmomanometer (anaedigital), but
unlike the sphygmomanometer no have operation on the
whole sample. Excluded are subjects mainly in the
suprasternal space not have a reflection of the rebound of
the arteries confined and also in subjects in which their
side zones to the neck is not palpable the location of the
carotid arteries and the internal jugular vein, this group
includes those individuals who have a body mass index
(BMI) greater than 25 kg/m2 and elderly patients.
The waveforms obtained with the PPC correspo
e cardiac cycle and are similar to the curves obtained
by cardiac catheterization. The PPC can help determine
one of the many parameters of the catheterization, since
it is easy to use and does not require specialized personnel
for its use.
The wav e
any movement of the test subject among which are:
respiration, the fluid passes through the esophagus or
involuntary displacement.
When is standardized th
r venous pressure and arterial pressure the waveforms
were very similar in terms of amplitude, frequency and
period, being that biologically come to have a value
deferred of at least 60 mmHG between blood pressure
and venous, since the venous for transport higher amounts
of blood is not pulsatile compared with the pressure in
arteries reaching values of 120 mmHg, while the vein is
5 mm Hg, this is an important consideration when
calibrating the PPC in the modalities of arterial and
venous pressure.
During the measurem
served that had a change in amplitude in curves when
the variants were apnea in inspiration or aspiration, as,
when there deep breath, the chest cavity and the lungs
expand, the chest wall expands and diaphragm low. This
causes the pressure intrapulmonary becomes more nega-
tive, which causes the lungs, heart and the and the thoracic
vein cava is expand decreasing the pressure inside them.
As the right atrial pressure decreases during inspiration,
the pressure gradient between the inferior vein cava and
right atrium increases, which impulse blood into the r ight
atrium (there is an effect of “suction”), thereby increasing
the volume of right ventricular ejection, to the pulmonary
circulation. On the other hand, although the atrium and
left ventricle also increases volume during inspiration,
Copyright © 2012 SciRes. OJAppS
the lungs in expanding work as a reservoir (increase the
volume of pulmonary blood), so that, left ventricular filling
does not increase during inspiration. During aspiration,
however, is produced the opposite effect: the thoracic
cavity volume decreases, because the chest wall is re-
tracts and the diaphragm up. This produces a pressure
increase intrapulmonary, causing a decrease in lung
volume, the heart and the thoracic vena cava. Therefore,
the accumulated blood in the pulmonary reservoir during
the inspiration is forced to pass into the atrium and left
ventricle, which increases left ventricular filling and
stroke volume of ejection into the aorta artery, in other
words, when inhaled, there is an increase in venous
pressure and when exhaling, there is a decrease in this,
these small variations are also detected by the PPC.
Gravity, temperature and metal objects also affect the
se that suggest the possibility that
5. Conclusions
s shown an excellent signal, w
th BMI indicating a
ore measurements com-
6. Acknowledgements
artial support to the DAIP
[1] S. I. Fox, “Fisaw-Hill, New York,
otti, M. Lanti, M. Angeletti, G. Botta, M. Cirilio
. E.
. Paez, C. Galarza and G. Waisman,
easurements. Gravity has a significant effect on blood
reservoirs and changes the values of pressure for a person
in a supine position, semi-fowler or perfectly straight.
The temperature changes the levels distensible of the
vessel and metal objects are detected by the PPC due to
their magnetic nature.
There are no databa
s been measured the pressure central with a noninvasive
method. The PPC has an advantage at this point, because
when positioned a magnet properly according to the
anatomy over a vein, can be record the movement of this
in a voltage-time signal, considering the magnet as an
extension of that place where it is placed, for healthy
subjects the vein is best seen in semi-fowler position.
For graduation of the units between PPC and the 2003.
[2] A. Men
rdiac catheterization in the arteries, can be associate a
“size” of the curve of blood recorded according to the
protocol specified by the pressure units. The size of the
curve for both methods is qualitatively and quantitatively
similar. It is noteworthy that what is related and it makes
sense is talk about the “size” of the curve in the PPC, since
it is very sensitive to movement between measurements
and also the curve is shifted with respect to a reference
level and for another subject does not match the voltage
obtained with other measurements of the same subject,
however the magnitude or the “size” of the curves can be
related to high accuracy.
The PPC device hahich “Hemodynamic Significance of High Brachial Pulse Pres-
sure in Young Men,” Clinical Hypertension, Vol. 26, No.
3, 2004, pp. 199-207.
describes qualitatively and unequivo cally form elevations
and depressions corresponding to waves of arterial and
venous pressure by noninvasive methods, however is af-
fected by characteristics of the medium and particularly
by respiration, although it has proven highly correlated
with pressur e points o f a sphygmomano meter digital [13]
while the gold standard in measuring blood pressure [14].
It has more meaning find the magnitude under the
rve, see Figure 11, to relate maximum and minimum
to a coordinate of voltage as the device shows a wide
variability in their measurements if used at different
times with a variation period of 24 h, These results in a
descriptive curve outdated even for the same subject,
with the same values of pressure.
It cannot be used in individuals wi
gree of obesity, because both the suprasternal area as
the lateral neck show no oscillatory motion of venous
and arteries by the large amount of fatty material which
causes i t to lo se t he sp rea d of t he m ovem ent of vas odilat io n.
If it want to be used for pressure measurement, two
ales are needed depending on the type of vessel to
measure, because biologically both vessel s sho w pr essure
values and curved very characteristic, for th e PPC measur -
ing in (voltage-time) and which is already associated
with a curve (mmHg-time).
It is proposed to carry out m
ring the signal acquired by the PPC vs. cardiac cathe-
terization, Doppler echocardiography and oscillometric
methods. For the venous study a larger sample is needed.
The authors acknowledg e the p
No. 017/2010 and Universidad De La Salle Bajío P/2011.
iología Humana,” McGr
and M. Laurenzi, “Twenty-Year Cardiovascular and All-
Cause Mortality Trends and Changes in Intravascular
Risk Factors,” Vol. 27, 2009, pp. 266-274.
[8] J. C. R. Pascual, M. R. Romero, R. C. Cerda and J
Morales, “Test de Reac tividad Vascular Pulmonary Blan-
hir,” Neumología y Cirugía de Tórax, Vol. 65, No. S4,
2006, pp. S43-S50.
[9] J. Alfie, C. Majul, O
Scandurra, G. J. Meschino
. Devera and F. C. Y R.
[10] F.M. Clara, A. Casarini, A. G.
and A. R. Introzzi, “Evaluación De Hipertensos en Base a
Registros de Variación de diÁmetro Arterial Radial,”
Medicina, Vol. 66, No. 6, 2006.
[11] D. Bia, I. Aguirre, Y. Zocalo, L
Armentano, “Diferencias Regionales en Viscosidad, Ela-
Copyright © 2012 SciRes. OJAppS
Copyright © 2012 SciRes. OJAppS
Disipación Energética
so Pre-
Biomagnética de las Curvas
sticidad y Amortiguamiento Parietal de Arterias Sisté-
Micas: Análisis Isopulsátil de la Relación Presi Ón-
Diámetro Arterial,” Revista Española De Cardiologia,
Vol. 58, No. 2, 2005, pp. 844-847.
[12] D. R. Armentano and Y. Zócalo, “
y Protección Vascular Durante La Hipertensión Arterial
Sistemica: Rol Del Músculo Liso,” Revista Uruguaya de
Cardiología, Vol. 20, No. 3, 2005, pp. 125-135.
[13] L. A. Romero, “Validación del Dispositivo Pul
etro Magnético para la Medición de la Presión Ar-
terial Sistémica,” Universidad de Guanajuato División de
Ciencias de la Salud, 2011.
[14] M. Maldonado, “Medición
de Presión Arterial y Venosa,” Universidad de Gua-
najuato, 2009.