A pneumatic connector for an automated non-invasive blood pressure
monitor having a connector body (1) containing two oppositely arranged
hollow cavities (8) for insertion of a differential pressure sensor
in each cavity. The hollow cavities are connected by a bore (10)
which is in connection with the main airway (6,7) in the connector
body (1). Additionally, both differential pressure sensors have
differential pressure sensors which are connected to the ambient
air via a secondary airway.
1. A pneumatic connector for coupling a blood pressure monitor
to a blood pressure cuff comprising:
a connector body,
means defining oppositely disposed cavities in outer surfaces of
said connector body, said cavities having bottoms facing each other,
a first passageway extending between the bottoms of said cavities,
a second passageway for receiving air from a pump coupling said
first passageway to one point on the surface of said body,
a third passageway for connection to a pressure cuff coupling said
first passageway to another point on the surface of said body, and
pressure sensors respectively mounted to the bottoms of said cavities
in a pressure tight manner so that only the bottoms thereof are
in communication with said first passageway.
2. A pneumatic connector as set forth in claim 1 wherein said sensors
are differential pressure sensors having reference inputs on their
sides opposite said bottoms and further comprising:
recesses in outer surfaces of said body respectively leading to
the cavities so as to be in communication with said reference inputs,
a fourth passageway communicating between said recesses, and
a fifth passageway communicating between said fourth passageway
and a point on the surface of said body.
3. A pneumatic connector as set forth in claim 2 further comprising:
a U shaped cover extending over said cavities and recesses.
4. A pneumatic connector for coupling a blood pressure monitor
to a blood pressure cuff comprising:
a solid body,
means defining oppositely disposed cavities in respective outer
surfaces of said body, said cavities having bottoms facing each
a first bore extending between the bottoms of said cavities,
a second bore extending from a surface of said body and through
said body to said first bore so as to permit air under pressure
to be introduced to said bores,
a third bore communicating between said first bore and a surface
of said body so as to serve as a connection for an airway to a pressure
first and second recesses in outer surfaces of said body respectively
communicating with outer portions of said cavities,
a fourth bore extending between said first and second recesses,
a fifth bore between said fourth bore and a point on an outer surface
of said body.
5. A pneumatic connector as set forth in claim 4 further comprising:
means for covering the said cavities so as to form reference pressure
chambers and for covering said first and second recesses.
6. A pneumatic connector as set forth in claim 5 further comprising:
pressure sensors having active sides and reference sides, said
sensors being respectively sealed in said cavities with their active
sides in communication with said first bore.
7. A pneumatic connector as set forth in claim 6 wherein said pressure
sensors have electrical contacts extending therefrom and further
means defining openings in said covering means through which said
8. A pneumatic connector comprising:
a solid body,
means defining a cavity in one side of said body that is adapted
to receive a pressure sensor,
means defining a first bore inside of said body forming a connection
between one point on the surface of the body and said cavity that
is adapted to be coupled to a pressure cuff,
means defining a second bore in said body forming a connection
between said first bore and a point on the surface of said body
adapted to be coupled to a source of air, and
a pressure sensor having an active side and a reference side mounted
in said cavity so that said active side is in sealed communication
with said first bore.
9. A connector for coupling a blood pressure monitor to a blood
pressure cuff comprising:
a solid body,
means defining a cavity in a surface of said body,
means defining an opening within said body communicating with said
means defining a first aperture in a surface of said body, said
first aperture being adapted for coupling to a tube from a blood
means within said body defining an airway between said opening
and said first aperture,
means defining a second aperture in a surface of said body, said
second aperture being adapted for coupling to a tube from an air
means defining a passageway between said second aperture and said
a pressure sensor having an active side and a reference side, said
sensor being located within said cavity with its active side facing
said opening, and
adhesive between said sensor and said means defining said cavity
forming a seal between the active and reference sides of said sensor.
10. A connector as set forth in claim 9 further comprising:
means including a cover positioned over said cavity so as to form
a reference pressure chamber adjacent to the reference side of said
a third aperture in a surface of said body, and
means including means defining a passageway in said body for providing
communication between said reference pressure chamber and said third
11. A connector as set forth in claim 10 further comprising:
electrical connection pins extending from said pressure sensor,
means defining holes in said cover through which said pins respectively
BACKGROUND OF THE INVENTION
This invention relates to a monitor for the automated non-invasive
measurement of a patient's blood pressure comprising means for automatically
inflating and deflating a cuff which is to be applied around a patient's
extremity, in particular an arm, a pressure sensor coupled to the
airway of said cuff and providing an electronic signal indicative
of the cuff pressure, electronic means for calculating the blood
pressure from the signals obtained by said pressure sensor, in particular
from the oscillations of the pressure signal, pneumatic connecting
means attached to said monitor--preferably, the casing thereof--said
pneumatic connecting means being provided for connection with a
cuff connector and comprising a connector body.
Monitors for the automated non-invasive measurement of blood pressure
generally comprise a cuff which is to be applied around a patient's
arm or leg. This cuff is inflated in periodic intervals by a pressure
pump integrated in the monitor. Subsequent to each inflating of
the cuff, it is deflated slowly by means of at least one valve integrated
in the monitor.
The deflating process is used to determine the blood pressure of
the patient, e.g. the systolic, diastolic or mean blood pressure.
This can be achieved, for example, by using a microphone which records
the Korotkoff sounds which appear when the arteries open (this method
is similar to the manual "auscultation" technique). Another
method which is better suited for automated blood pressure recordings
is the so-called "oscillometric method". According to
this method, the oscillations superimposing the generally decreasing
cuff pressure are monitored during the deflating process to determine
the various blood pressures (systolic, diastolic or mean). The algorithms
used to determine the blood pressure from these oscillations are
rather complex; algorithms of this kind have been described in a
lot of patent applications. An example out of many other ones is
European patent application EP-A-208 520.
Monitors of the kind described above comprise a pneumatic connector,
usually of the female type, which is attached to the casing of the
monitor. In operation, a second (male) pneumatic connector is inserted
in the female connector. The second (male) connector is connected
with the cuff by means of a flexible tube. Such a monitor further
comprises a pressure sensor coupled to the airway of said cuff and
providing an electronic signal indicative of the cuff pressure.
Such a pressure sensor is necessary for controlling and monitoring
the pressure in the cuff, in particular for monitoring the maximum
cuff pressure (i.e. the pressure at maximum inflation--this pressure
is not identical to the pressure upon which a safety valve may open!)
and for controlling the process of cuff deflation (this is particularly
important if the cuff is deflated in single decrementing steps).
When using the osillometric method which apparently becomes the
most common one in the automated monitoring field, the pressure
sensor is further required to record the high-frequency oscillations
during the deflating process. Such a pressure sensor or pressure
transducer is, for example, shown in EP-A-208 520, cf. reference
Monitors according to the state of the art comprise a lot of airway
tubes, T-connectors and tube nozzles arranged inside the monitor.
These connection elements are necessary to connect the pump, one
or two valves and one or two pressure sensors to the main airway
leading to the pneumatic connector at the front end of the monitor.
In these monitors, the pressure sensor is arranged inside the monitor
casing, and most commonly it is soldered on a printed circuit board.
A tube connects the pressure sensor with the pneumatic connector.
Such an arrangement has a lot of disadvantages with respect to manufacturing;
in particular, the various tubing elements are expensive and time-consuming
to assemble. Furthermore, the tubing elements and the pressure sensors
mounted directly on the printed circuit board require a lot of space,
particularly board space. Other disadvantages do have physical reasons;
in particular, the pressure sensor is positioned relatively distant
to the patient, and therefore the pressure recorded by the sensor
may not correspond to the actual pressure in the cuff as each tube
acts as a pressure resistance. Further, the connection tube may
expand, and the volume of the airway system is rather large.
It is therefore a major objective of the present invention to provide
a monitor for the automated non-invasive measurement of blood pressure
which ensures that the actual cuff pressure is recorded very precisely
and which is easy and cost-saving to assemble.
BRIEF SUMMARY OF THE INVENTION
According to one aspect of the invention, this objective is solved
in a monitor of the type described above by the following features:
The connector body of the pneumatic connecting means comprises
at least one hollow cavity adapted to receive the pressure sensor,
the hollow cavity is pneumatically connected with the airway of
the connecting means, and
the pressure sensor is fixed in said hollow cavity in pressure-tight
The connector body itself is preferably manufactured from plastic.
The pressure sensor is integrated in said connector body by placing
it in a hollow cavity (preferably, a cylindrical bore). The sensor
is fixed in said hollow cavity in pressure-tight manner. Such a
pressure-tight seat may advantageously be achieved by gluing the
pressure sensor in the hollow cavity; a preferred glue ensuring
pressure-tightness is a one-component polyester glue.
The hollow cavity is further connected pneumatically with the (main)
airway in the pneumatic connector, i.e. the airway leading from
a tube nozzle (which is provided for connection to the pump and
the valve via a tube) to the outside opening.
As--according to the invention--the pressure sensor is integrated
in the connector body, the sensor is positioned closer to the cuff
than in prior art monitors. Therefore, the cuff pressure may be
recorded more precisely. Further, the connector body (whether manufactured
from plastics, metal or any other suitable material) contains only
well-defined cavities and bores which do not influence the recorded
pressure value, whereas--in prior art arrangements--the necessary
tubes could expand when pressure was applied to them, and, thus,
distort the measured value. By omittance of tubes as required in
prior art solutions, the volume of the airway system is reduced.
Further, the pressure resistance effect of connector tubes is ommitted.
The solution provided by the present invention has also manufacturing
and cost advantages. In particular, costs can be saved as there
is no need for tubes, T-connectos and the like (the pneumatic connecting
means according to the invention only provides one tube nozzle for
connection to the pump and the valve and an outside opening). Manufacturing
costs may be saved by the simplified assembly of the new connector.
Last not least, the invention helps to save space inside the monitor,
particularly board space (space on printed circuit boards).
The invention further relates to a pneumatic connector for attachment
to an automated non-invasive blood pressure monitor--preferably,
for attachment to the casing thereof--said pneumatic connector being
provided for connection with a cuff connector and comprising a connector
body. According to this aspect of the invention, the connector body
comprises at least one hollow cavity--preferably, a cylindrical
bore--adapted to receive a pressure sensor; the hollow cavity is
pneumatically connected with the airway of said pnuematic connector,
and said pressure sensor is fixed in the hollow cavity in pressure-tight
It has been found that it may be advantageous to use not only one
pressure sensor (which is most commonly a piezoelectric sensor),
but two independent pressure sensors instead. These two pressure
sensors may be used to control each other in order to detect malfunctions.
The connector body of the pneumatic connector provides therefore
two hollow cavities adapted to receive a pressure sensor each. In
this case, it is advantageous if the two hollow cavities are located
opposite each other and if they are connected by a bore which is
in connection with the airway of the pneumatic connector. Such a
connector is not only easy to manufacture (in addition to the other
advantages as outlined above), but it also ensures that both pressure
sensors receive the same pressure which cannot be guaranteed if
they are connected to the connector using tubes.
Most pressure sensors used in the technique of non-invasive blood
gas monitoring are differential pressure sensors, i.e. they generate
an electrical signal indicative of the difference between the unknown
(cuff) pressure to be measured and a reference pressure, usually
the pressure of the ambient air. If such a differential pressure
sensor is--as in prior art monitors--placed inside the monitor,
it is a major problem that the reference input of the sensor is
not exposed to the pressure of the room air, but rather to the pressure
inside the monitor which may differ from the outside pressure caused
e.g. by temperature effects, convection and the like.
According to a preferred embodiment of the invention, the connector
body comprises at least one additional bore connecting the reference
input of the differential pressure sensor to the outside. This is
a very cheap and easy-to-manufacture solution which ensures that
the outside pressure is applied to the reference input of the pressure
sensor. This solution requires no additional tubes, connecting means
therefor etc. to connect the reference input of the differential
pressure sensor to the outside.
Advantageously, a cover is used covering the outside of the pressure
sensor. This cover defines a reference pressure chamber connecting
the reference input of the pressure sensor with the additional bore.
This ensures that no further components like bores, tubes etc. are
necessary to connect the reference input of the pressure sensor
with the outside. In particular, said cover may be fastened to the
connector body by a glue or adhesive. The connector body may further
provide additional recesses, said cover fitting on these for further
sealing. According to a preferred embodiment, said cover comprises
recesses for guiding the pins of the pressure sensor and allowing
them to project to the outside of the pneumatic connector. These
pins may then be directly soldered to a printed circuit board to
save additional electrical connections.
If the pneumatic connector comprises two differential pressure
sensors, advantageously a common bore connects the reference inputs
of said differential pressure sensors, said common bore being connected
to the outside by an additional bore approximately perpendicular
to said common bore. Such a solution is not only easy to manufacture,
but has the additional advantage that the reference inputs of both
differential pressure sensors receive exactly the same reference
signal via their common bore. The two hollow cavities may be covered
by a common, generally U-shaped cover which is preferably glued
to the connector body. Such a cover will define two reference pressure
chambers connecting the reference inputs of the differential pressure
sensors with the common bore. Such a common cover may be positioned
very tight to the connector body and is easy to assemble.
According to a further advantageous embodiment, the outside of
the connector body is covered by an outside cover which comprises
recesses at its back side connecting the outlet of said additional
bore with the ambient air. Room air has therefore to pass said recesses
to reach the additional bore leading to the one or two differential
pressure sensor(s). This ensures that the outside opening of said
additional bore cannot be blocked by foreign bodies. Preferably,
said recesses connect the outside opening of the additional bore
in the connector body with a large opening in the outside cover,
said large opening being provided for insertion of the cuff connector.
A pneumatic connector embodying the invention will now be described--by
way of a non-limiting example--with reference to the accompanying
drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a pneumatic connector embodying the invention,
FIG. 2 is a side view of this connector in the direction of arrow
II of FIG. 1,
FIG. 3 is a further side view according to arrow III of FIG. 1,
FIG. 4 is the top view according to arrow IV of FIG. 1,
FIG. 5 is the bottom view according to arrow V of FIG. 1,
FIG. 6 is the back view of the pneumatic connector according to
arrow VI of FIG. 4, the left half of the connector being partially
FIG. 7 is a section according to line VII--VII of FIG. 1,
FIG. 8 is the backside view of the outside cover covering the front
end of the connector,
FIG. 9 is a side view of this outside cover according to arrow
IX of FIG. 8, the upper part of this cover being partially broken
FIG. 10 is a section along line X--X of FIG. 8,
FIG. 11 is the bottom view of a cover covering one of the pressure
FIG. 12 is a side view of this cover according to arrow XII of
FIG. 13 is a further side view according to arrow XIII of FIG.
FIG. 14 depicts a view similar to that of FIG. 1, but including
a differential pressure sensor, and
FIG. 15 is a cross section similar to that of FIG. 7, but also
including the differential pressure sensors.
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, the connector body of a pneumatic connector is generally
outlined as 1. This connector is intended for attachment to the
casing of an automated non-invasive blood pressure monitor. Connector
body 1 is snapped in an appropriate opening of the front wall of
said casing by means of groove 2. Connector body 1 is manufactured
A cuff connector--not shown--is introduced into an opening 4 of
connector body 1 during operation. In FIG. 1, the contour of opening
4 is shown by broken lines 3a and 3b; the opening can further be
seen in FIG. 7 which is a section along line VII--VII of FIG. 1.
The cuff connector is connected via a tube to the cuff which is
to be applied around a patient's arm. Connector body 1 is further
connected with a pump and at least one valve inside the monitor;
for this purpose, connector body 1 provides a tube nozzle 5 for
connection with a tube. In operation, the monitor inflates the cuff
by applying a pressure generated by a pump (not shown) to tube nozzle
5; a main airway in the connector body defined by a first connection
line 6 (in broken lines), a second connection line 7 (also in broken
lines) and opening 4 connects tube nozzle 5 with the cuff connector.
As the cuff connector is connected with the cuff via a tube, the
pump pressure is applied to the cuff and inflates it. When the maximum
cuff pressure is achieved, the monitor stops inflating the cuff
and starts the deflating process by opening a valve. During the
deflating process, the oscillations superimposing the generally
decreasing cuff pressure are monitored. These oscillations are indicative
of the blood pressure (systolic, diastolic, mean) of the patient.
The calculated blood pressure(s) are then monitored or recorded.
The main airway inside the connector body can also be seen in FIG.
6 which is a backside view with the left part partially broken away.
The main airway is defined by connection lines 6 and 7 and opening
The connector body further provides two hollow cavities 8 and 9
for insertion of a differential pressure sensor in each cavity.
These sensors are required for monitoring the cuff pressure, in
particular the maximum cuff pressure and the oscillations caused
by the opening of the patient's arteries during the deflating process.
For graphical purposes, these sensors are not shown explicitly in
FIGS. 1-7; they fit exactly in hollow cavities 8 and 9 and are attached
there in pressure-tight manner by a one-component polyester glue.
The signal inputs of the differential pressure sensors are connected
via a bore 10 which is also in contact to the main airway as defined
by connection lines 6 and 7.
Within connector body 1, recesses 11 and 12 (FIGS. 1 and 6) are
defined. A cross section of recess 11 can be further seen in the
small broken-away region in FIG. 3.
Recesses 11 and 12 are connected via a common bore 13. Said common
bore is further in connection with an additional bore 14 which connects
common bore 13 with the ambient air. Common bore 13 and additional
bore 14 define a secondary airway which is not in connection with
the main airway as defined by connection lines 6 and 7 and opening
4. This secondary airway provides connection of the reference inputs
of the differential pressure sensors with the ambient air.
After attachment of the connector body to the casing of the monitor,
the outside of the connector body is covered by an outside cover
as shown in FIG. 8. FIG. 8 depicts a backside view of said outside
cover 16. A recess 15 connects the outside opening of additional
bore 14 with the ambient air. For this purpose, outside cover 16
is placed on the front end of connector body 1 (i.e. the bottom
side according to FIG. 1) such that the end 15a of recess 15 faces
the outside opening of additional bore 14. For example, one could
take outside cover 16 as shown in FIG. 8 and turn it around its
vertical axis; then it would fit exactly on the connector body front
end as shown in FIG. 5.
Outside cover 16 is snapped on a connector body 1. Opening 17 serves
for insertion of the cuff connector.
When the differential pressure sensors are placed in hollow cavities
8 and 9, these cavities are further covered each by a cover of the
type as depicted in FIG. 11. Such a cover 18 fits exactly over hollow
cavities 8 and 9 which contain the differential pressure sensors.
Over each of hollow cavities 8 and 9, a cover 18 is placed and glued
there. Further, cover 18 fits in recesses of connector body 1 which
are defined by edges 23, 23', 24, 24', 25, 25', 26 and 26'. These
covers define reference pressure chambers as will be explained by
means of FIG. 15.
A projection 19 of cover 18 covers the lower openings 20 and 21
(FIG. 3) adjoining hollow cavities 8 and 9. Portion 19 is equipped
with teeth 22a, 22b and 22c. The spaces or recesses 29a, 29b, 29c,
29d between these teeth receive the electrical connection pins of
the differential pressure sensor when the pneumatic connector is
completely assembled. These pins then project to the outside of
the connector. Therefore, the connector may be directly soldered
to a printed circuit board; the feet 23 and 24 (FIGS. 1, 3, 4 to
6) seat on the printed circuit board in this case.
Instead of using two covers as depicted in FIG. 11, it is also
possible to use a common, generally U-shaped cover to cover cavities
8 and 9; such a common cover may be snapped on connector body 1.
FIG. 14 depicts a side view of connector body 1 similar to that
of FIG. 1. A differential pressure sensor 30 fits exactly in the
chamber defined by hollow cavity 8 (cf. FIG. 1) and is glued there.
Differential pressure sensor 30 provides four pins 31a, 31b, 31c
and 31d projecting to the outside. These pins fit into recesses
29a-29d of a cover 18 when this cover is applied to connector body
1. Differential pressure sensor 30 provides a reference input 32.
A similar input (the measurement input) is located centrally on
the bottom side of the sensor and is in contact with bore 10 (cf.
FIG. 15 depicts a cross section of connector body 1 similar to
that of FIG. 7. Hollow cavities 8 and 9 (cf. FIG. 7) contain differential
pressure sensors 30 and 33. Their outside is covered by covers 18a
and 18b which define reference pressure chambers 34 and 35 which
connect the reference inputs of pressure sensors 30 and 33 with
common bore 13.