WO2011023521A1

WO2011023521A1 - A uterine contraction measurement device and a fetal monitoring system

Info

Publication number: WO2011023521A1
Application number: PCT/EP2010/061409
Authority: WO
Inventors: Balaji Teegala; Archana Kalyansundar; Barath Ramesh
Original assignee: Siemens AG; Siemens Corp
Current assignee: Siemens AG; Siemens Corp
Priority date: 2009-08-27
Filing date: 2010-08-05
Publication date: 2011-03-03
Anticipated expiration: 2012-02-27

Abstract

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).

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 interrelate 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 the 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.

Claims

What is claimed is:

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 (Fl) from a woman's abdomen (4), - the piezoelectric element (10) mechanically coupled to the elastic structure (6) such that the normal force (Fl) 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 .