Non-Invasive Blood Pressure Monitoring with Positionable
Three-chamber Pneumatic Sensor
V. E. Antsiperov
1,2 a
, G. K. Mansurov
, M. V. Danilychev
and D. V.
Kotelnikov Institute of Radio Engineering and Electronics of RAS, Moscow, Russia
Moscow Institute of Physics and Technology, Moscow, Russia
Scientific and Technological Centre of Unique Instrumentation of the RAS, Moscow, Russia
Keywords: Blood Pressure Non-Invasive Measurement, Continues Pulse-Waveform Monitoring, Local Pressure
Compensation Principle, Pneumatic Pressure Sensor, Sensor Positioning Problem, Multichannel
Measurements and Control.
Abstract: The main goal of the paper is to present a new type of a sensor for non-invasive continuous blood pressure
measurements. The principle of such a sensor operation, based on local pressure compensation, is in the centre
of discussion. The sensor presented has very small sensing pads (1 mm
or less) which permits accurate sensor
positioning directly on the elastic surfaces such as the human skin. Thanks to that it is possible to provide a
high quality of the blood pressure measurement, when keeping the continuity of the measurement parameters
and minimizing the level of disturbances. For this reason, the paper focuses on a detailed discussion of the
positioning problem and the results of developing approaches to its solving. As a promising method, a
positioning based on the pulse wave controlling by a three-chamber pneumatic sensor is proposed.
The invasive method for measuring arterial blood
pressure (ABP) is direct and the most accurate.
However, due to strict professional personnel
requirements, it is used only in acute cases in a
hospital, under the supervision of a qualified and
certified medical personnel. This method does not
allow to continuously monitor the patient's every day
activities, to track objective hemodynamics and the
state of the cardiovascular system outside the
Most of modern methods for non-invasive
measurement of ABP are based on manipulation of
counter-pressure in the cuff or the applicator,
compressing the artery (usually together with the
limb). The goal of these manipulations is to neutralize
the possible additional pressure caused primarily by
strained elastic artery walls (Settels, 2014).
Oscillometric method and Korotkoff method are
quantitatively dominant in ABP measurement, but
they determine only two pressure levels - systolic and
diastolic, along with pulse frequency, just enough for
everyday use. These methods, however, do not
present the shape of ABP pulse wave beat-to-beat.
Moreover, continuous monitoring of ABP is
impossible when the methods inherently intermittent
are used. In further development of Marey’s
proceedings, dated 1860-80, new methods of arterial
tonometry were proposed in 1960-70-s. For example,
when monitoring BP using the Peňáz method, for
these purposes, the principle of volume compensation
is used, exploiting the idea of dynamic “unloading of
vessel walls” (Peňáz, 1973). Pressman and Newgard
proposed the idea of local compensation of an artery
wall by a flat applicator with a plunger (rider) located
in it (Pressman and Newgard, 1963). The plunger was
provided by a tracking drive for mechanical push on
the artery wall (through the skin) in counterphase
with pressure in it. It was assumed that the force
required to keep the plunger stationary (according to
the displacement sensor) is proportional to the
pressure in the arteries. Looking ahead, we note that
the distribution of pressure on the applicator pad in
the projection of the artery is very uneven, so at best
this method could measure the change in average
pressure at the plunger pad. High demands on the
accuracy of manufacturing miniature mechanical
Antsiperov, V., Mansurov, G., Danilychev, M. and Churikov, D.
Non-Invasive Blood Pressure Monitoring with Positionable Three-chamber Pneumatic Sensor.
DOI: 10.5220/0007574904620465
In Proceedings of the 12th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2019), pages 462-465
ISBN: 978-989-758-353-7
2019 by SCITEPRESS Science and Technology Publications, Lda. All rights reserved
assemblies and the presence of friction and backlash
in moving parts are the additional disadvantages of
this method.
The disadvantage of Peňáz method is that in order
to avoid stagnation of blood in the limb, it is
necessary to periodically relax the cuff, which breaks
the continuous regime of ABP monitoring. To
overcome this problem some new approach to a
continuous, non-invasive and indirect measurement
of ABP based on changes in pulse wave velocity
(PWV) was proposed in (Gesche et al., 2012). PWV
is the speed of the pressure pulse propagating along
the arterial wall and it can easily be calculated from
pulse transit time (PTT). The implementation of this
approach, based on MEMS pressure sensors was
reported in (Kaisti et al., 2017).
To avoid disturbances related to the inflation of
the cuff and the alterations of the ABP caused by such
disturbances, we also developed a new approach to
continuous, non-invasive blood pressure
measurement. But in contrast to PWV our method is
based on the principle of local pressure compensation
(Figure 1).
Figure 1: The measurement principle of blood pressure due
to local pressure compensation in the artery Part by pressure
in the measuring element Psen of the pneumatic sensor (A)
and the appearance of the element applied to the patient's
wrist (B).
Practical implementation of this method became
possible by the previously developed unique technic
of pressure compensating measurements on a very
small working area (1 mm2 or less) (Antsiperov et al.,
When analyzing well–known methods of non–
invasive continuous measurement of blood pressure,
we can conclude that the best results of monitoring
non–stationary dynamics of ABP are achieved by the
so–called compensation methods or methods similar
to them.
The compensation methods are used for
measurement of various physical quantities and are
based on the compensation of an unknown measured
value by controlled counter value and nullification of
their difference. The simplest example of the
compensation method is the use of balance scales on
which unknown mass is measured using a set of
counter -weights. The predetermined position of the
balance beam or the associated arrow serves as a null
indicator of the balance scales.
The compensation methods as methods of high
precision are used for electrical measurements, in
embodiments having bridge and half-bridge circuits.
Note that the compensation methods are usually used
to measure the static variables, for example the
constant unknown resistance in bridge circuits.
We consider the compensation method as the
fundamental basis to measure the varying blood
pressure. The application of this method for
measuring the non–static dynamic quantity has
become possible, for two reasons.
Firstly, the fact that blood pressure changes are
not so fast, its rhythm is of the order of one beat per
second, and its spectrum fits into the range of a few
tens of Hz. Secondly, there are relatively cheap, high
performance microcontrollers for which such a
change in pressure is quasi-static.The idea of local
compensation principle for measuring pressure in
inaccessible volumes of gas or fluid is as follows: if
the external force fails to make the shape of the
surface bounding the volume of the elastic membrane
locally flat, then the external pressure due to the lack
of longitudinal elastic stresses in the shell will be
equal to the internal. This principle is realized in the
method of applanation tonometry to measure
intraocular pressure (Goldmann and Schmidt, 1975).
For non-invasive pressure measurement in the
inaccessible volume of the artery this principle is
illustrated in Figure 1. Namely, if at some initial
moment the pressure in the measuring chamber of the
sensor element P
is less than the pressure in the
artery P
then the tissue and the skin directly above
the artery snug against the air channel of the sensor
and lock it. Once P
reaches P
, the channel outlet
is opened, and the excess air goes under the flat
surface of the measuring element being pressed
against the skin. If the air flow into the chamber is
chosen correctly (choice of pressure P
in the
receiver and the throttle position of the screw), the
laminar flow of air from the chamber will keep the
skin surface in a flat, minimally open state,
Non-Invasive Blood Pressure Monitoring with Positionable Three-chamber Pneumatic Sensor
automatically maintaining balance P
with variable blood pressure).
In other words, we developed the pneumatic
pressure sensor with local compensation principle,
based on the idea of an automatic pressure relief valve
in the working chamber with a constant flow of air
from the outside (from the receiver).
It turned out, however, that the advantages of locally-
compensatory blood pressure measurement are not
obtained free of charge, and they have to be paid for
by the problems arising here with the positioning of
the measuring sensor. Since the contact pad (outlet
channel hole) of the measuring element has
substantially smaller sizes than artery size, the in-
sensor pressure coincides with Р
(see Figure 1) only
when the sensor pad is located directly above the
artery. Defacements of blood pressure measurement,
associated with positioning of the sensing pads, are
illustrated in Figure 2.
Figure 2: Distinguishing shape of pulse wave signal from
sensor (A), depending on sensing pads position: — pad is
directly over the artery, . — pad is shifted to the left, to
the right from the centre of the radial artery.
Figure 3: Sensor with three-chamber measuring element
based on locally compensatory blood pressure
measurement (A), implementing the three-channel
synchronous measurement of the pulse wave (B).
A detailed study of the positioning problem
revealed the following. In the position just above the
artery the ABP signal has the greatest magnitude
between the major maxima and minima and wherein
the extrema are themselves more acute (see Figure 2).
As seen from Figure 3, the same symmetrical
positions with respect to the artery occur when the
pulse wave graphics substantially coincide.
These observations led us to design a pneumatic
sensor for monitoring blood pressure comprising a
measuring unit with three chambers for locally
compensating pressure measurements (each with its
own independent pressure meter), arranged in a row
transversely to the direction of the artery. Thus, in
certain positions of the measurement element the
chamber pads are simultaneously over the artery. A
schematic view of the sensor and the result of
simultaneously measuring by the three-channel pulse
wave at the proper position upon the artery are shown
in Figure 3. Details of the technical implementation
of the sensor are presented in the patent (Mansurov et
al., 2018).
In the claimed design of three-chambered
pneumatic blood pressure measuring sensor lateral
chambers are used basically to control the positioning
of the measuring element. Namely, the correct
arrangement of the sensor corresponds to the
maximum coincidence of signals from the lateral
channels (see Figure 3). Thus, it is not essential that
these channels cannot achieve complete "unloading"
of the side walls of the artery and, therefore, ABP
signals are significantly distorted. It is important that
the coincidence of these signals ensures the central
chamber to be located exactly above the artery normal
and in this position an undistorted signal from central
chamber replicates the pressure in the artery.
The methodology of measuring three-chambered
pneumatic ABP sensor is closely associated with the
described features of its construction. Namely,
immediately before the measurement the artery
location is estimated by means of palpation (feeling
for the pulse) to the patient's wrist. Then the
measuring element is applied so that the sensing pads
were arranged in a row transversely to the direction
of the artery (see Figures 2, 3). Further, moving the
sensor in the direction transverse to the artery, such a
position is sought in which the side channels signals
would maximally coincide. After that, the sensor is
pressed to the arm to make the contact of the central
pad with artery wall (through skin) as flat as possible,
without artery occlusion (applanation principle).
HEALTHINF 2019 - 12th International Conference on Health Informatics
A new method of positioning the three-chamber
pneumatic sensor for ABP measurement based on
local pressure compensation is proposed in the paper.
The main idea of local compensation is discussed in
detail. It is shown that this idea is quite simple and in
part resembles the principle of the relief valve. But to
achieve the stability in ABP measuring it is necessary
to provide very small sizes (tens of microns) for the
outlet channel hole of the measuring element. While
the sizes of a pads become smaller than the artery
size, the in-sensor pressure coincides with ABP only
when the sensor pad is located directly above the
artery. So, the advantages of locally-compensatory
blood pressure measurement are not obtained free of
charge – they have to be paid for by the problems
arising here with the positioning of the measuring
The features of the measuring element
construction that we found made it possible to
produce up to four or more working chambers with a
linear step from one and a half mm to two mm in one
block of the element. According to the results
obtained the variant with three working chambers is
optimal. We believe that this solution allows the
implementation of a sensor option with the automatic
positioning of the applicator over the artery, since
manual positioning restricts the applicability of the
sensor proposed.
In short, the test results of the three-chambered
pneumatic sensor positioning and the developed
calibration technique showed the following:
1) a significant improvement in the accuracy of
measuring of systolic, diastolic blood pressure
and pulse characteristics due to calibration and
correct positioning of the measuring element;
2) the possibility of continuously measuring blood
pressure beat-to-beat for a long time (many
3) the possibility for qualitative measurements of the
patient’s hemodynamics in everyday life.
The most important task in prospect is to replace the
manual positioning of the sensor by the automatic
control of its position and to develop on this basis a
mobile device for continuous monitoring of ABP
The authors are grateful to the Russian Foundation for
Basic Research (RFBR), grant N 18-29-02108 mk for
the financial support of this work.
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Non-Invasive Blood Pressure Monitoring with Positionable Three-chamber Pneumatic Sensor