Description
A uterine contraction measurement device and a fetal
monitoring system
The invention relates to a uterine contraction measurement
device and a fetal monitoring system.
Uterine Contraction has a primary function to expulse the
intrauterine contents. Uterine activity before the onset of
active labor may prepare the uterus and cervix for labor. The
uterus is a smooth muscle organ that, during pregnancy, is
progressively stretched. Contractions may be the
physiological response to this stretch. These contractions
are of high intensity and have a frequency that increases
from 1 contraction per hour at 30 weeks to in every 5 to 10
minutes at term period. Due to the structure of the uterus
the strength of the contraction is greater at the fundus and
the least at the cervix.
Initially the fetal monitoring systems were developed to
measure the fetal heart rate to determine the fetal distress.
But the fetal heart rate data is not sufficient to determine
the fetal distress. Thus the uterine contraction patterns
were also included later by some of the devices, so that the
various deccelerative patterns of fetus heart rate could be
timed in relation to the uterine contractions.
Uterine activity is assumed to be adequate if progress in
labor, as defined by progressive cervical dilations and
descent, is occurring. Failure to progress in labor is due to
inadequate contractions. On the other hand, the excessive
uterine activity gives rise to fetal hypoxia. When it is
necessary to induce labor, the clinician must be aware of the
uterine activity, because it could lead to fetal distress or
uterine rupture. Any of these conditions required close
monitoring of uterine activity.
One possible way to measure the uterine contraction is
through manual palpation. The disadvantage with it is that it
can only measure the frequency relatively. It is time
consuming, requires constant attendance, and provides no
permanent record.
Another possible way is to use the ring tocodynamometer. It
provides a weight with a centrally placed pressure sensitive
button secured to the abdominal wall through a strap. The
tocodynamometer is positioned near the fundus and adjusted to
a position that results into the best contraction recording.
It reduces the problem of constant attendance and no
permanent record. But it requires a high level of precision
and expertise to locate the right point to put on the
tocodynamometer.
Yet another possible way could be to increase the size of the
tocodynamometer to increase the precision and also to make it
less location sensitive. But in contrast, this makes the
device heavy and bulky to be put on the woman abdomen. Also,
using more material would make the device costly.
One another technique uses strain sensor to detect the
pressure fluctuations from the Uterine Contraction. It uses
different patches where it embeds the pressure sensor and
stick to three part of the women abdomen to make it non-
location specific. But it uses larger sheets of the strain
sensor. Also to detect the right uterine contraction, this
technique has to provide a higher processing time to
eliminate the non-effective uterine contraction rate. This
makes the device costly as well as bulky, thus, difficult to
use also.
It is an object of the present invention to provide an
economical and easy measurement of uterine contraction.
The said object is achieved by providing a uterine
contraction device- according to claim 1 and by a fetal
monitoring system according to claim 13.
The invention is based on the idea to provide a piezoelectric
element which detects a tangential stress received from an
elastic structure through a mechanical coupling between the
elastic structure and the piezoelectric element. The use of
elastic structure with the piezoelectric element increases
its sensitivity as through the elastic structure
piezoelectric element can detect the tangential stress from
an area from a women's abdomen which would be beyond the
reach of piezoelectric element if made in direct contact with
woman's abdomen. Use of the light weight piezoelectric
element and the light weight elastic structure makes the
uterine contraction measurement device light weight and easy
to be handled by a doctor or any other person measuring the
uterine contraction. With the use of simple elastic structure
and an inexpensive, readily available piezoelectric element,
the uterine contraction measurement uterine contraction
measurement device become cost-effective.
In one of the embodiments, the uterine contraction
measurement device receives the tangential stress when the
piezoelectric element comes directly in contact with the
elastic structure. This form of mechanical coupling helps to
increase the sensitivity of the piezoelectric element as the
stress is directly transferable into the piezoelectric
element from the elastic structure.
In another embodiment, the uterine contraction measurement
device has the piezoelectric element which is fixed to the
elastic structure. Direct fixation of the piezoelectric
elements helps to detect low intensity tangential stress
received at the elastic structure surface.
In another embodiment, the uterine contraction device have
the piezoelectric element placed in center relative to the
elastic structure such that to receive the tangential stress
with the uniform intensity and from whole of the elastic
structure more effectively than a non-centered placement.
In another embodiment, the uterine contraction device has a
piezoelectric element which is in a shape of a loop. The loop
is in contact to the elastic structure and an inner
circumference of the loop covers a substantial area of the
elastic membrane. It helps the piezoelectric element to
detect the tangential stress from a substantial area of the
elastic structure, thus increases sensitivity of the uterine
contraction device.
In another embodiment, the uterine contraction device has a
fastening means to fasten the device to a women's abdomen, so
that the device is not displaced by the woman's movements or
excessive force of the stress.
In another embodiment, the uterine contraction device has an
adhesive fastening means, so that the device would be easy to
wear by a woman.
In another embodiment, the uterine contraction device has an
interface to output a uterine contraction electrical signal,
so that the signal can be further processed.
In another embodiment, the uterine contraction device has a
mechanical coupling between the piezoelectric element and the
elastic structure,- such that the normal forces are
transferred into the piezoelectric element through the
elastic structure. This helps to increase the sensitivity of
the piezoelectric element as it can receive now both the
tangential as well as normal stress.
In another embodiment, the uterine contraction device has the
elastic structure having a sheet shape. Such elastic
structure is easily available off the shelf, thus make the
uterine contraction device cost-effective.
In another embodiment, the uterine contraction measurement
device provides with a fetal contraction signal processor to
process the uterine contraction electrical signal obtained
from the piezoelectric element and generate a uterine
contraction data which is further displayed on a display
unit. The display unit helps the doctor to understand the
uterine contraction data to make more precise medical
analysis.
Another embodiment relates to a fetal monitoring system which
comprises a uterine contraction measurement device that
processes the uterine contraction electrical signal through a
fetal monitoring system signal processor to provide the
uterine contraction data which is further displayed on a
fetal monitoring data display unit. The inclusion of the
device in the fetal monitoring system makes it possible to
correlate the uterine contraction data to the fetus health
and its activity in a better way.
In another embodiment, the fetal monitoring system further
interfaces to a fetal heart rate measurement device. The
fetal monitoring system signal processor in addition to the
uterine contraction signal also processes a fetal heart rate
electrical signal received from the fetal heart rate
measurement device. A data generator is provided which
generates a fetal monitoring data from the uterine
contraction data and the fetal heart rate. The fetal
monitoring data is displayed on the display unit. The
interface with the fetus heart rate measurement device
provides the fetal monitoring system with facility to inter-
relate the fetus heart rate data and the uterine contraction
data which increases the fetal monitoring system's utilities
beyond measuring uterine contraction, like to determine the
labor period, requirement of a cesarean, the fetus health,
etc.
The above-mentioned and other features of the invention will
now be addressed with reference to the drawings of a
preferred embodiment of the present uterine contraction
measurement device. The illustrated embodiment of the uterine
contraction measurement device is intended to illustrate, but
not limit the invention. The drawings contain the following
figures, in which like numbers refers to like parts,
throughout the description and drawings.
Fig 1 is a side view of a uterine contraction measurement
device interfaced to an electrical signal processor which is
connected to a display unit.
Fig 2 is a sectional view of a uterine contraction
measurement device according to an embodiment of the
invention showing the piezoelectric element when not placed
on a women abdomen.
Fig 3 is a sectional view of a uterine contraction
measurement device according to an embodiment of the
invention showing the uterine contraction measurement device
fastened to a woman's abdomen.
Fig 4 is a sectional view of a uterine contraction
measurement device according to an embodiment of the
invention showing the uterine contraction measurement device
fastened to a woman's abdomen when women's abdomen is in
stress condition.
Fig 5 is a top view of a of uterine contraction measurement
device according to an embodiment of the invention showing
the piezoelectric element receiving tangential stress from
the elastic structure.
Fig 6 is a top view of a of uterine contraction measurement
device according to an embodiment of the invention showing a
loop shaped piezoelectric element receiving tangential stress
from the elastic structure.
Fig 7 is a top view of a of uterine contraction measurement
device according to an embodiment of the invention showing a
plurality of the piezoelectric element receiving tangential
stress from the elastic structure.
Fig 8 is showing a fetal monitoring system according to an
embodiment of the invention having interface with the uterine
contraction measurement device.
Fig 9 is showing a fetal monitoring system according to an
embodiment of the invention having interface with the uterine
contraction measurement device and with a fetal heart rate
measurement device.
Figure 1 illustrates a uterine contraction measurement device
2 according to an embodiment of the invention, having a
piezoelectric element 10 and an elastic structure 6
mechanically coupled together to transfer tangential stress
from the elastic structure 6 to the piezoelectric element 10.
When the uterine contraction measurement device 2 is fastened
to a woman's abdomen 4 and the woman is in a uterine
contraction stage, it generates a tangential stress F2 on its
abdomen. This tangential stress F2 from the women abdomen 4
is received by the elastic structure 6 to transfer the stress
F2 to the piezoelectric element 10 through a mechanical
coupling.
The mechanical coupling is advantageously achieved by
providing a contact between the piezoelectric element 10 and
the elastic structure 6 helps to increase the sensitivity of
the piezoelectric element 10 as the stress is directly
transferable into the piezoelectric element 10 from the
elastic structure 6. The mechanical coupling can also be
achieved by introducing any mechanical structure like spring
or a rod or any other element which transfers the stress F2
from the elastic structure 6 to the piezoelectric element 10,
or by directly fixing the piezoelectric element 10 on the
elastic structure 6, or the likes. Direct fixation of the
piezoelectric elements 10 is advantageous to detect low
intensity tangential stress received at the elastic structure
surface 6.
The elastic structure is advantageously provided with an
easily available sheet shape which can be bought off the
shelf. Such an elastic structure 6 reduces the cost of the
uterine contraction measurement device. The elastic structure
can also be in a uniform or a non-uniform shape or it can
specifically be designed to give a shape to achieve the easy
storage of the elastic structure. The uniformly thick elastic
structure is advantageous to receive the stress from the
woman's abdomen 4 uniformly and also avoids dampening of the
stress before being detected by the piezoelectric element 10.
The piezoelectric element 10 is advantageously placed
centered to the elastic structure 6, so that the tangential
stress F2 is received uniformly from all direction of the
elastic structure 6 and also with a uniform intensity.
The piezoelectric element 10 can also be placed near the
edges of the elastic structure 6 or near the centre or
anywhere between the centre and the edges relative to the
elastic structure 6.
The piezoelectric element 10 receives the stress F2 from the
elastic structure 6 to produce an electric signal. The
electric signal is amplified through an amplifier 12 to
increase the signal intensity. According to one another
embodiment of the invention, the electric signal is output
from the uterine contraction measurement device through an
interface for further processing of the signals.
According to one another embodiment of the invention, the
uterine contraction measurement device 2 is interfaced to a
uterine contraction signal processor 14 which processes the
signal to produce the uterine contraction data like the
presence of uterine contraction, the intensity of the uterine
contraction, the uterine contraction rate, the images of the
uterus in contraction stages and other such data related to
rhe uterine contraction measurement.
The uterine contraction data is then displayed through a
uterine contraction data display unit 16 which is connected
to the uterine contraction signal processor 14. The display
unit 16 could be a video display unit, a LED display unit or
any other mechanical display unit. The mechanical display
unit makes the uterine contraction measurement device 2
cheaper as less processing is requires, while, the LED
display unit provide precision in respect to numerical data
representation or raising an alarm in form of different
colors. The video display unit has an advantage to provide
the images in regards to various movements inside a woman's
abdomen 4.
Figure 2 illustrates the uterine contraction measurement
device 2 of figure 1 having a housing 8 which holds the
piezoelectric element 10 and an amplifier 12. The housing 8
has a convex side and a concave side. The piezoelectric
element 10 is attached to the housing 8 facing the concave
side. The piezoelectric element 10 is advantageously attached
centered to the housing 8 facing the concave side and the
elastic structure 6. The centered position provide a regular
structure to the uterine contraction measurement device 2, as
well it provide proper reception and transmission of the
electrical signal. The elastic structure 6 is extended over
the piezoelectric element 10 and attached to the housing 8
such that it covers the concave side of the housing 8.
Figure 3 illustrates the uterine contraction measurement
device 2 as shown in figures 1 and 2 when it is fastened to a
woman's abdomen 4 and the woman's abdomen 4 is in a non-
stress stage which occurs when a woman is not experiencing a
uterine contraction. On fastening the uterine contraction
measurement device 2, the elastic structure 6 is compressed.
In this stage of a women's abdomen 4 the piezoelectric
element 10 can come in contact with the elastic structure 6
to establish a contact with it. This contact is limited in
respect to provide a stress F2 on the piezoelectric element
and still more stress F2 needs to be applied to create any
electrical signal. The piezoelectric element 10 need not
contact the elastic structure 6 in the current position of
the woman abdomen 4 and the element 10 could come in contact
when the woman abdomen 4 is in the contraction stage.
The uterine contraction measurement device 2 is provided with
a fastening means 28 to fasten it to the woman's abdomen 4.
The uterine contraction measurement device 2 is provided with
the strip based adhesive fastening means 28, as such
fastening means is fastening the housing 8 to the woman's
abdomen 4. The adhesive based fastening means 28 provides
easy fastening and de-fastening of the uterine contraction
measurement device 2 to the woman's abdomen 4. The uterine
contraction measurement device 2 can also be provided with
other adhesive based fastening means 28 like the adhesive to
fix the elastic structure 6 to fix to the woman's abdomen or
gel based fastening means to be used on woman's abdomen 4 to
fasten the uterine contraction measurement device or the
likes. The adhesive based fastening means 28 helps to provide
comfort to the woman and also keeps the uterine contraction
measurement device 2 intact to the woman's abdomen 4, so the
device 2 need not to be monitored repeatedly to check the
position of the device 2 on the woman's abdomen 4. Other
temporary fastening means 28 can also be used like belts to
be wrapped around the woman's abdomen 4 having the uterine
contraction measurement device 2 attached to the belt or
magnetic fastening pads or any other such temporary fastening
means.
Figure 4 illustrates a uterine contraction device 2 when the
device 2 is fastened to a woman's abdomen 4 and the woman's
abdomen 4 is in the stress stage which occurs when a woman is
experiencing a uterine contraction. In this stage, the
elastic structure 6 gets more compressed and also receives
stress F2, Fl from the woman's abdomen 4. This stress can be
identified as the tangential stress F2 and a normal stress
Fl. The piezoelectric element 10 comes in contact to the
elastic structure 6 and the tangential as well as the normal
stress Fl, F2 get transferred to the piezoelectric element
10. The piezoelectric element 10 produces the uterine
contraction electrical signal which is amplified by.the
amplifier 12.
Figure 5 illustrates a top view of the uterine contraction
measurement device 2 as shown in the figures before which
shows the piezoelectric element 10 receiving the tangential
stress F2 in a radial direction in respect to the
piezoelectric element 10 contact to the elastic structure 6.
The tangential stress F2 make the piezoelectric element 10 to
deform and with this deformation an electric potential is
generated which is amplified in the form of electrical signal
for further processing.
Figure 6 illustrates the uterine contraction measurement
device 2 according to one another embodiment of the invention
where the piezoelectric element 10 is loop shaped and detects
the tangential stress F2 from a wide area of the elastic
structure 6. The loop is in contact to the elastic structure
10. An inner circumference of the loop covers a substantial
area of the elastic structure 6. The loop need not be a
closed loop, but it can also be an open loop with an opening
into the loop. The loop whether open or closed, it should be
such that to cover a substantial area of the elastic
structure 6 by the inner circumference of the loop. The
surface area of the loop can be more than half of the surface
area of elastic structure 6, but it need not be limited to
more than half and it can be less than half also. A diameter
of the inner circumference of the loop can be more than one-
third of the length or diameter of the elastic structure 6
for a rectangular or circular elastic structure 6
respectively but it need not be limited to more than one-
third of the length or diameter of the elastic structure 6
for a circular or rectangular elastic structure respectively
and it can be less than one-third of the diameter or length
of the elastic structure 6 in the case of a circular or a
rectangular elastic structure 6 respectively. The size of the
piezoelectric element 10 should be such that to cover a
substantial area of the elastic structure 6. Such a
piezoelectric element 10 detects the signal more precisely in
comparison to a same weight based non-loop piezoelectric
element 10. The use of loop shaped piezoelectric element 10
increases the sensitivity and a stress detection capability
of the piezoelectric element 10. Also, the geometry of the
piezoelectric element is not limited to a ring, it can be a
helical geometry or a net geometry or any such geometry which
can cover the substantial area of the elastic structure 6
while keeping the weight of the piezoelectric element 10 low.
Figure 7 illustrates the uterine contraction measurement
device 2 according to one another embodiment where there is
plurality of the piezoelectric element 10, so that the
tangential stress F2 is transferred to the piezoelectric
element 10 more accurately in respect to a single
piezoelectric element 10. The use of a plurality of
piezoelectric elements 10 ensures that the uterine
contraction measurement device can still continue to work if
one piezoelectric element 10 is disabled e.g. damaged, short
circuit in the amplifier and piezoelectric element connection
or any other electrical or mechanical disability.
Figure 8 illustrates a uterine contraction measurement device
2 according to another embodiment of the invention where the
device 2 is connected to a fetal monitoring system 18 through
an interface. An electrical signal generated by the uterine
contraction measurement device 2 after amplification through
the amplifier 12 is transmitted to the fetal monitoring
system 18. The electrical signal is processed by a fetal
monitoring signal processor 20 to produce a uterine
contraction data like the presence of uterine contraction,
the intensity of the uterine contraction, the uterine
contraction rate, the symbolic images of the uterus in
contraction stages and other such data related to the uterine
contraction measurement. The uterine contraction data is than
displayed on a fetal monitoring data display unit 22. The
display unit 22 can be a video display unit, a LED display
unit, any other mechanical display unit or any other display
unit which can display the uterine contraction data. The
mechanical display unit makes the uterine contraction
measurement device 2 cheaper as less processing is requires,
while, the LED display unit provide precision in respect to
numerical data representation or raising an alarm in form of
different colors. The video display unit has an advantage to
provide the images in regards to various movements inside a
woman's abdomen 4. The inclusion of the uterine contraction
measurement device 2 in fetal monitoring system 18 makes it
possible to correlate the uterine contraction data to the
fetus health and its activity.
Figure 9 illustrates a fetal monitoring system 18 according
to one another embodiment of the invention where the system
18 has an interface to connect to a uterine contraction
measurement device 2 and a fetal heart rate measurement
device 24. The system 18 has a fetal monitoring signal
processor 20 which processes the electrical signal received
from the uterine contraction measurement device 2 and the
fetal heart rate measurement device 24. The processed signal
is further fed into a data generator 26 to produce a fetal
monitoring data for determining either a labor period, or
requirement of a cesarean, or fetus health or any such data
which could be critical for fetus and the woman in regards to
the labor and child delivery. The fetal monitoring data is
displayed on a fetal monitoring data display device 22. The
interface with the fetus heart rate measurement device 24
provides the fetal monitoring system 18 with a facility to
inter-relate the fetus heart rate data and the uterine
contraction data which increases the fetal monitoring
system's 18 utilities beyond measuring uterine contraction.
The inter-relation between the fetal heart rate data and the
uterine contraction data is to find the fetal heart rate
deccelerative pattern with respect to the Uterine Contraction
data either at the time of woman experiencing the uterine
contraction or just after she has experienced the uterine
contraction. The fetal monitoring system 18 can further be
used to determine either the labor period, or requirement of
a cesarean, or the fetus health, etc.
We Claim:
1. A uterine contraction measurement device (2) comprising
- an elastic structure (6) having a contact surface to
receive a tangential stress (F2) from a woman's abdomen (4),
- a piezoelectric element (10) mechanically coupled to the
elastic structure (6) such that the tangential stress is
transferable from opposing directions of the elastic
structure (6) to the piezoelectric element (10).
2. A uterine contraction measurement device (2) according to
claim 1, wherein the tangential stress (F2) is transferable
when the piezoelectric element (10) directly comes in contact
to the elastic structure (6).
3. A uterine contraction measurement device (2) according to
claim 2, wherein the piezoelectric element (10) is directly
fixed onto the elastic structure (6).
4. A uterine contraction measurement device (2) according to
claim 1 to 3, wherein the piezoelectric element (10) is
centered relative to the elastic structure (6).
5. A uterine contraction measurement device (2) according to
claim 1 to 4, wherein the piezoelectric element is in a shape
of a loop, and wherein the loop is in contact with the
elastic structure (6) circumferentially around a inner
circumference of the loop and the inner circumference covers
a substantial part of the surface of the elastic structure
(6) .
6. A uterine contraction measurement device (2) according to
any of the claims 1 to 5, wherein the uterine contraction
measurement device (2) comprises a fastening means (28) to
fasten the uterine contraction measurement device to the
woman's abdomen (4).
7. A uterine contraction device (2) according to any of the
claims 1 to 6, wherein the fastening means (28) is an
adhesive strip.
8. A uterine contraction measurement device (2) according to
any of the claims 1 to 7, wherein the uterine contraction
measurement device (2) comprises an interface to output an
uterine contraction electrical signal depending on a
measurement of the piezoelectric element (10).
9. A uterine contraction measurement device (2) according to
any of the claims 1 to 8, further comprising
- the elastic structure (6) having the contact surface to
receive a normal force (F1) from a woman's abdomen (4),
- the piezoelectric element (10) mechanically coupled to the
elastic structure (6) such that the normal force (F1) is
transferable from the elastic structure (6) to the
piezoelectric element (10).
10. A uterine contraction measurement device (2) according to
any of the claims 1 to 9, wherein the elastic structure (6)
is in the shape of a sheet.
11. A uterine contraction measurement device (2) according to
any of the claims 1- to 10, wherein the uterine contraction
measurement (2) device further comprises
- a fetal contraction signal processor (14) which is adapted
to process an uterine contraction electrical signal from the
piezoelectric element (10) to generate an uterine
contraction data indicative of the uterine contraction;
- a uterine contraction data display unit (16) adapted to
display the uterine contraction data.
12. A uterine contraction measurement (2) device
substantially as herein above described in the specification
with reference to the accompanying drawings.
13. A fetal monitoring system (18) comprising
- a uterine contraction measurement device (2) according to
any of the claims 1 to 12;
- a fetal monitoring system signal processor (20) which is
adapted to process an uterine contraction electrical signal
from the uterine contraction device to generate a uterine
contraction data;
- a fetal monitoring data display unit (22) adapted to
display the uterine contraction data generated.
14. A fetal monitoring system (18) according to the claim 13,
wherein
- the fetal monitoring system (18) further comprises
- an interface adapted to receive a fetal heart rate
electrical signal from a fetal heart rate measurement device
(24),
- the signal processor (20) which is further adapted to
process the fetal heart rate electrical signal received from
the fetal heart rate measurement device (24) to generate a
fetus heart rate;
- a data generator (26) to generate a fetal monitoring data
from the uterine contraction data and the fetus heart rate;
- the display unit (22) which is further adapted to display a
fetal monitoring data.
15. A fetal monitoring system (18) substantially as herein
above described in the specification with reference to the
accompanying drawings.

A uterine contraction measurement device (2) having an elastic structure (6) with a contact surface to receive a tangential stress (F2) from a woman's abdomen (4) and a piezoelectric element (10) mechanically coupled to the elastic structure (6) such that the tangential stress (F2) from opposing directions of the piezoelectric element (10) are transferable from the elastic structure (6) to the piezoelectric element (10). The uterine contraction device (2) has a processor (14) to process the signal received from the piezoelectric element (10) and generate a uterine contraction data. A uterine contraction data (2) is further displayed on a display unit (16) which is also a part of the uterine contraction measurement device (2).