Note: Descriptions are shown in the official language in which they were submitted.
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The present invention has for its ob~ect an
apparaeus for the automatic measurement of the arterial
pressure of a patient.
To measure this pressure by the palpation
method, by the auscultative method or by the oscillometric
method, one uses apparatuses which are called sphygmomano-
meters.
The most recent methods are based always on
the principal of the splyRmomanometry but have improved
means to detect the pulsations or the arterial noises.
Among these methods~ the most used are the photoelectric pletis-
mographie for the determination of the arterial pulsations
and a system which amplifies the arterial noises.
Another detecting method for the arterial pulsations
for the indirect measurement of the systolic and diastolic
pressure is the use of ultrasonic waves.
The advantage of this method is its insensibility
to the external noises and that it permits the measurement
of the pressure even in the cases where the known methods
which measure the arterial noises can not be used due to the
low level of these noises (as it is the case by children or
hypotensitives adults).
The method is based on the Doppler effect, the
frenquency variation which is obtained is :
dF = 2f v/c
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where dF is the frequency of the incident ultrasonic waves
v is the vibration speed of the arteria
c is the propagation speed of the ultrasonic waves
through the body tissues.
All these devices or methods to take the arterial pres-
sure necessitate the use of a pneumatical inflatable bag which
takes with it a non negligible manutention and thus a loss of time.
The aim of the present invention is to realize an auto-
matic apparatus to measure the arterial pressure which does not
use a pneumatical inflatable bag.
More specifically, the invention resides in an auto-
matic apparatus for the measurement of arterial pressure, compri-
sing a housing having a supple wall at one of its ends, said wall
partly defining a measuring chamber within said housing, and in
said housing a piezoelectric emitter of ultrasonic waves, a piezo-
electric receiverof the Doppler effect, a piezoelectric pressure
detector, said emitter and receiver and detector all being spaced
from said wall, a measuring and display circuit electrically con-
nected to said pressure detector to display pressure in said cham-
ber, said receiver controlling said display circuit, whereby whensaid wall is applied against the artery of a patient, the ultra-
sonic waves emitted by said piezoelectric emitter are reflected
from said wall to said receiver and said display circuit displays
the diastolic or systolic pressure of the artery to which said
wall is applied, and means permitting a controlled leakage of air
from said chamber.
The attached drawing shows schematically and by way of
example one embodiment of the apparatus according to the invention.
Figure 1 is a schematic view of it.
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Figure 2 shows at greatest scale the front
portion of the apparatus.
Figure 3 is a block sheme of the apparatus.
Figure 4 shows electrical curves showing the
working of the aparatus.
The apparatus comprises a casing 1 the wall 2
of which is constituated by a deformable supple material.
The front part of this casing comprises a measuring chamber 3
separated from the rest of the inside of the casing 1 by a
wall 4. This wall 4 comprises a calibrated hole 5 as well as
an aperture 6 the closing of which is controlled by a valve 7.
mis wall 4 carried further an ultrasonic waves transducer 8
the membrane of which separates the measuring chamber 3 from
the rest 9 of the casing 1.
A support 10 placed within the chamber 3 and
fixed to the casing 1, carries two ultrasonic waves transducers
11~ 12.
The transducer 11 is used as waves transducers
transducer 12 is used as a detector for the ultrasonic waves
which are reflected.
This support comprises a passageway 13 giving
passage to the ultrasonic waves.
An emitter-receiver of ultrasonic waves 14,
electrically connected to the transducers 11 and 12, emits
at a power which is lower than 200 mW/cm2 in order to avoid
the hemolyse effects which could be induced through the inter-
mediary of the eransducer 11.
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The transducer 8 is electrically connected
to a measuring circuit controlling a display circuit 15.
This display appears however in 16 or 17 only when the
presence of reflected ultrasonic waves is detected by the
transducer 12. Finally a battery 19 delivers the electric
power necessary to the working of the apparatusO
~ he resilient membrane 2 of the dome shown in
full line in its rest position takes the position shown in
dolted line when the operation of pressure measurement
is in course, that is when this membrane 2 is applied against
a member of the patient. The pressure inside the chamber 3
takes a maximum instantaneous value and diminishes slowly,
due to the presence of the calibrated hole 5, the valve 7
being closed.
The transducer 11 emits an ultrasonic signal
which is reflected in the presence of an arterial oscillation
on the transducer 12. me two transducers 11, 12 are fixed on
a support 10 which permits, through the apertures 13~ the
penetration of the emitted ultrasonic waves up to the
transducer 8 used as a pressure detector. This transducer 8
has its upper part in contact with the inside of the chamber 3
and its lower part in contact with the environemental aera
When there is a pressure within the chamber 3,
the upper part of the transducer is submitted to a mechanical
stress which varies in function of the pressure~ At the end of
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the measure and when the dome is taken away, the valve 7
is open and enables the wall 2 to take lts initial shape.
The membrane 2 of the dome deforms itself
during the measurement of the pressure, and creates in the
chamber 3 an instataneous pressure which is higher than the
systolic pressures to be measured. This pressure diminishes
slowly due to the hole 5 and corresponds successively
to the diastolic and the systolic pressures to be measured.
Figure 3 shows an electrical diagram cf the system
used. The emitter 20 is connected to the base of the emitting
transducer 21; that base emits permanently on to the base of
the transducer of the receiver 22 used as pressure detector
The recelver 23 translates the pressure variations in electrical
varlations. ~he base of the transducer for the reception 24
is submitted to the ultrasonic emission only in case of a
vibration of the arteria In this case, the receiver 24
measures the Doppler signal obtained and actuates a memory 26
in coincidence with the first reception of the Doppler effect
received. This blocks the displays 27, which receive
permanently the pressure information which is inside the
chamber 3, through the intermediary of the receiver 23. The
maximum information is thus displayed in the first indicator 28.
During the second Doppler effect, the same cycle is reproduced,
the me~ory 29 is selected and the minimum information is
displayed in the-second indicator 30. The setting to zero is
made by the switch 31.
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Figure 4 shows electric curves of the working
of the system. Curve A shows the heart beats rythme
(Ps being the systolic pressure and Pd the diastolic pressure
The cure B shows the pressure within the dome before the
measure and during the measure. The curve C shows the presence
of Doppler effect signals in the receiver. These being
defined in fuction of the pressure within the dome on the one
hand and in function of the heart beat signal on the other
side. The curves D and E determine the working moments thus
the blocking of the displays.
When the pressure being in the chamber 3 is
equal to the diastollc or systolic arterial pressure, the
transducer 12 detects reflected ultrasonic waves modified by
the beating of the artery. The signal which this transducer 12
delivers causes then the unlocking of the display circuit
and the pressure being in the chamber 3, measured by this
transducer 9~ is displayed to the indicating circuits 16~ 17
showing respectively the diastolic or systolic pressure.
The detection through Doppler effect of the
beating of an artery is already used in medicine but only in
combination with a pneumatic inflatable bag permitting to apply
a pressure on the arm of the patient.
Used in combination with a pressure detector of
the ultrasonic waves detector, which uses the same emitter 11~
this apparatus is self sufficient, and permits the direct digital
reading of the arterial pressure. This apparatus is very easy
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and handy to use. It is to be noted that the pressure detector
used is of the type of the one described in the Swiss Patent
No. 598,587.
The sensibility of this apparatus enables to measure the
arteri.al pressure of hypertensive individuals or o~ children.
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