CZ307183B6 - A device for monitoring vital functions of a pregnant woman's foetus - Google Patents

Abstract

The object of the invention is a monitoring device vital functions of a pregnant woman with a sensor fiber processing unit and processing unit a signal that contains an A / D converter (1 2) and a digital signal processor (13) residing therein that the signal processing unit is connected to an interferometer that includes a transmitter unit (1) with radiation source (7), receiver unit (2) with at least one photodetector (6) and through optical fibers between receiving unit (2) and the transmitting unit (1) connected fiber optic fiber optic sensor forming measuring route with measuring loop (4) and reference route with a reference loop (5) having at least one binding loop a member (8) at the beginning and end of said paths, where jc preferably at least a portion of the measuring path with the measuring fixed by the loop (4) of the fiber optic sensor in a primary binding agent (9) of elastomers.

Description

The present invention relates to a device for monitoring the vital functions of a pregnant woman using a fiber optic interferometer sensor. Furthermore, it will enable, among other things, the acquisition of mechanical / acoustic manifestations, such as the uterine activity containing the fetus and the measurement of the vital functions of a pregnant woman.

BACKGROUND OF THE INVENTION

During pregnancy and during labor, it is important to monitor the fetal and maternal vital functions and the uterine contractions. With the increasing possibility of performing births (for example, birth in water or birth in a position of choice by the mother), the demands on the used sensors of vital functions of the mother and the fetus are also increasing. However, the vibration sensing principle requires the mother to be calm for optimal measurement, unwanted vibration can reduce the signal sensing accuracy.

Monitoring of the Fetal Heart Rate (FHR) and its changes in relation to fetal movements and contracting activity of the pregnant woman uterus allows the gathering of the information needed to properly assess the condition of the fetus before and during delivery. In particular, this information can help doctors monitor and diagnose endangered fetuses and pregnant women during pregnancy and delivery.

The current measurement of the fetal heart echo is performed by a method called KTG examination or cardiotocography. Cardiotocographic examination is a way to determine the fetal condition in utero by monitoring the contraction of the mother's uterus and the fetal heart echo by recording the FHR. The cardiograph consists of a recording device and two probes, namely a toco-probe and a cardio-probe. The toco-probe is a piezo-electric crystal sensor and is used to record uterine contractions. The cardio-probe can be of two types: for indoor use (electrode) or for outdoor use (ultrasonic). The function of the cardio-probe is based on the Doppler effect, with contractions of the heart valves, atria and ventricles being recorded. The ultrasonic probe, which can be used even before birth due to external use, has a greater use. Cardiotocography is the most widespread method for measuring the fetal heart rate in the mother's womb. While this method is reliable and effective, it is accompanied by several disadvantages or limitations, such as the need to attach individual ultrasound probes to the body of a pregnant woman in the abdominal area so that they are firm and non-slip, most often using a Velcro belt or compression bandage wrapped around probes around the body of a pregnant woman. Attaching ultrasound probes to the body can be frustrating for the mother, it is time consuming due to the process of attaching and searching for a sufficiently strong signal for these less sensitive probes, and often inefficient for spot sensing fetal heart sounds. If the child is in a less accessible position, the position of the probes must be changed and the monitoring repeated.

The complicated and inconvenient attachment of the probes to the body of a pregnant woman in the abdominal area is solved by patent application WO 2005/110 236 A1, which describes a waistless device for monitoring the fetal heart rate by means of an ultrasound sensor. The adhesive coated device is comfortably applied to the body of a pregnant woman in the abdominal region and is preferably used in a wireless form allowing the mobility of the pregnant woman. The device can also be used to monitor heart rate in children and adults.

A solution for measuring heart rate using a fiber (but not interferometric) principle is known from U.S. Patent No. 6,463,187 B1. Here, the measuring mechanism is the pressure exerted on the coupler. The coupler is a passive optical element in which the optical radiation is combined or distributed. The basic parameter is the split ratio. In this case, it varies based on the pressure exerted on the fiber joint. It is therefore a mere conversion of pressure to optical power and then to electrical voltage. These sensors are called intensity sensors and are simple to solve. In practice, however, they achieve low sensitivities, which is particularly limiting in monitoring fetal vital signs. They are therefore mainly used for measuring the pulse of the wrist. Moreover, the use of this sensor is purely point-wise, where it is necessary to place the wrist at a specific location where the movement of the piston from the artery is transmitted to the coupler.

According to the article by S. Albín et al. (A non-invasive Fiber Optic Sensor for Fetal Heart Rate Monitoring, SPIE Vol. 3211, 0277-786X / 97, pages 496-500) is a non-invasive fiber optic sensor for FHR measurement. The optical fiber section is deprived of acrylic primary protection on the surface, these bare portions of the two fibers (with a wavelength of 750 ± 50 nm) are twisted and joined together in a special melting micro-oven to form 2 x 2 couplers that attach to the elastic membrane in an aluminum plate. At the input is a laser semiconductor diode producing radiation of 5 mW and a wavelength of 830 nm. The light input to the coupler produces two outputs. The signals on two outputs are detected by a silicon (Si) detector, monitored by an oscilloscope with a GPIB computer interface. Signal filtering techniques are used to shield background signals such as maternal breathing and fetal or cardiac pulse movements. The sensor mentioned in the article by Albín et al., Is not based on the principle of interferometer, but works on the principle of changing the binding ratio of a specially manufactured coupler, where the intensity of radiation changes directly at the output. Nor is it indicated how the non-invasive probe is placed near the signal source.

Optical interferometers are instruments whose principle is based on light interference, they have a wide application especially in physics. Two-beam interferometers differ schematically in their arrangement, different types are known under the names Mach-Zehnder interferometer, Michelson interferometer, Sagnac interferometer and others. They always contain a radiation source (normally a laser) and a radiation detector (or its replacement), where the beams pass through an optical system with mirrors, light-transmitting glass plates and other elements. In the fiber optic interferometer, the connection of the radiation source and the detector is realized by means of optical fibers, which serve to transmit light signals in the direction of the longitudinal axis of the optical fiber. Fiber optics can only be used to transmit information or even as sensors. Optical fiber interferometers measure the average fiber deformation between two points compared to a second loose fiber that is not attached to these points.

Interferometric sensors using fiber optic interferometers to measure cardiac echo are also used to measure heart rate. These interferometric sensors are based on phase modulation of the light wave that propagates through the optical fiber caused by applying pressure to the optical fiber applied to the body. The measured physical quantities are determined from the phase change of the detected light wave.

In the article by Sprager et al. (Heartbeat and Resporation Detection Form Optical Interferometric Signals by Using a Multimethod Approach, IEEE Transastions on Niomedical Engineering, Vol. 59, No. 10, October 2012, pages 2922-2929) mentions the use of a Michelson interferometer to measure vital signs using an optical sensor in direct or indirect contact with the human body, the experimental part being presented on the indirect contact method.

U.S. Patent No. 6,498,652 discloses a portable, non-invasive device primarily serving as a monitor for the breath, heart rate, and physical movement of adults or children based on an interferometer of known type (Mach-Zehner, Sagnac, Michelson, Fabry-Perot) generating an optical signal acousto-mechanical signals in the optical fibers, which include a radiation source, input of the first and second optical fiber paths with a minimum path length of 10 m with an optical loss of about 20 dB, where the paths are divided in the first coupler (optionally combined in the second coupler). The first optical fiber path is located close to the patient and the second path includes a reference loop with a polarizer, means for generating a series of interference patterns, which senses the photodetector and converts it into an electrical signal further processed

-2GB 307183 B6 and displayed on an output system where a combination of heart rate and breath signals is possible using a low pass filter. One or more optical sensors are located in the rectangular lining of the pad, where the pad is placed on a cot mattress, hospital bed, etc., and overlaps with a sheet where the optical fiber is guided zigzag side to side through the entire pad, and the pad is connected to the electro - an optical unit (with a radiation source, a photodetector, a signal processor and other circuits) mounted to the bed structure, from which signals are transmitted by a transmitter to a remote portable receiver with a signal processing system imaging system. The device also includes a connected A / D converter, digital signal processor and controller. However, this solution cannot monitor hard-to-read and unavailable signals such as fetal heart rate (FHR), uterine contractions or fetal movements in the uterus, which require a much more sensitive device to monitor.

The fiber optic and non-invasive ultrasound sensors described in the introductory section are not sensitive enough to monitor the fetal vital signs in the early stages of pregnancy, and their use in the prenatal phase is often accompanied by lengthy mounting and finding the right position for the probes. High sensitivity of the probes or gain of a sufficiently strong FHR signal are the key parameters of efficient data acquisition.

SUMMARY OF THE INVENTION

The above drawbacks are overcome by a device for monitoring the fetal vital signs of a pregnant woman with an optical fiber sensor and a signal processing unit comprising an A / D converter and a digital signal processor, which is based on the signal processing unit being connected to an interferometer comprising a transmitter unit with a radiation source, a receiver unit with at least one photodetector, and a fiber optic sensor comprising a measuring loop with a measuring loop and a reference loop with a reference loop with at least one coupler initially connected via a fiber optic between the receiving unit and the transmitting unit and at the end of these routes.

The main benefit over prior art solutions is the use of an interferometer-based sensor that allows for a much more sensitive sensing of the fetal heart rate. The advantage of using a fiber optic sensor is also passive optical detection and passive demodulation, complete isolation from the electrical network, ie resistance to interference from the network, the electrical non-conductivity of the probe are connected to the pregnant woman by electrically nonconductive optical fibers.

A further substantial increase in the sensitivity of the fetal heart rate sensing can be achieved in a preferred embodiment of the invention, wherein at least a portion of the measuring path with the measuring loop of the fiber optic sensor is fixed in the primary binding agent of the zelastomer. The primary binding means is intended for non-invasive contact with the body in the abdominal region of a pregnant woman, thus being placed directly on the skin near the signal source, the primary binding means preventing air from contacting the contact surfaces, i.e. between the sensor and the skin. The advantage is also easy applicability with lower demands on operation by personnel.

In any case, thanks to advanced signal processing techniques, the invention allows the sensing and separation of two or more quantities from a single signal, such as a pregnant woman's fetus and a fetus, either using a single measuring loop in contact with the body or using a measuring and reference device. body contact loops, wherein in a preferred embodiment where the reference loop is also in contact with the body separately from the measurement loop, the sensitivity of the measurement is substantially increased. Sensing multiple quantities at the same time is economical in terms of time, number of probes used.

Thus, in a further preferred embodiment, at least a portion of the reference loop with the reference loop is also fixed in the secondary elastomer binding means, and the secondary binding means can then be used for non-invasive contact with the body of a pregnant woman, particularly in the thoracic region. The advantage of this embodiment of the reference loop is the possibility of sensing various quantities

With only one universal sensor, it is easier to extract two or more variables from the difference between the reference and measuring loops of a single signal, such as the pregnant woman's breath, the pregnant woman's heart rate and the fetal heart rate, even at an early pregnancy , uterine contractions, fetal movement, etc.

At least a portion of the reference loop with the reference loop may also be fixed in the primary binding agent of the zelastomer, which is intended for non-invasive body contact, particularly in the abdominal region. Of course, the reference loop reference path need not be fixed in any elastomeric binding means, and in this case it is not intended for body contact.

In a preferred embodiment, the at least one binding member is also fixed in the primary or secondary binding means.

Elastomers are characterized by the ability to elastically deform, ie the body can return to its original shape. The elasticity or stiffness of the material is expressed by the modulus of elasticity (Young's modulus of elasticity E). Rigid materials, such as glass, with a modulus of elasticity of tens of GPa or more have a hard surface. As a result, they transmit high-frequency vibrations faster and more efficiently. In contrast, materials with a low modulus of elasticity, such as elastomers with a modulus of elasticity in the order of MPa, have a soft surface, the sound propagates more slowly, and is thus more sensitive to the low frequencies that are characteristic of the human body. Suitable / optimal elastomers for use in the manufacture of a primary or secondary binder have an elastic modulus in the range of 1 to 10 MPa. These include, for example, polydimethylsiloxanes (PDMS) having a modulus of elasticity of 1 to 3 MPa, natural rubber having a modulus of elasticity of 1 to 5 MPa, or polyurethanes with a modulus of elasticity of 2 to 10 MPa.

However, not all materials with a corresponding modulus of elasticity are suitable for the production of a primary or secondary binder. An important parameter is also the tensile strength and plasticity that determines if the deformation is permanent. From the point of view of the modulus of elasticity, a suitable material could also be plasticine with a modulus of elasticity of 2 to 5 MPa, but for plasticine the tensile strength is in the order of tens of kPa. Elastomers incl. PDMS have an ultimate tensile strength in the order of MPa, which ensures good bonding of the bonding agent under mechanical stress. E.g. PVC has a modulus of elasticity of 2 to 4 MPa, but the lack of plasticity of the material does not allow easy copying of the shape and adhesion to the body surface of the pregnant woman, which the elastomers have. Thus, the elastomeric binding means is so flexible and flexible that it readily conforms to the shape of the human body, i.e., completely conforms to the shape of the body and adheres well thereto. A particularly preferred material for making binding agents is polydimethylsiloxane, which is non-toxic, inert, non-toxic, non-flammable, easy to wash and reusable, safe, non-invasive, and water resistant.

Preferably, the primary and / or secondary coupling means are in the form of a body with a rectangle, circle, oval, square, ring, or other shape. Preferably, the coupling means has a base content of 15 to 2500 cm ² , a height of 2 to 10 mm, a weight of 50 to 300 g. The use of the coupling means results in a higher sensor sensitivity and a higher probability of signal capture. signal, which results in higher accuracy / sensitivity of the measured data. The high sensitivity of the sensor enables monitoring of the fetus in the period prior to the antenatal phase of pregnancy, so it is suitable for measuring vital functions of the fetus or pregnant woman in both early and advanced stages of pregnancy. The attachment of the fiber optic sensor of the present invention is not precisely determined by the size and shape of the body of the pregnant woman, preferably the binding means can be made from an elastomer with a fixed measuring or reference loop in a universal dimension. The advantage of all said embodiments of the binding means is a simple method of attachment to the body. In addition, the simplicity of the fiber optic sensor allows measurement in unconventional birthing positions or in non-standard environments such as water births or electromagnetically stressed environments (during electromagnetic resonance, near a computer tomograph).

-4GB 307183 B6

The minimum length of the optical fiber fixed in the binding means depends, inter alia, on its size and affects the overall sensitivity of the fetal vital signs monitoring device of the pregnant woman of the present invention. When designing the coupling means, the critical bending radius of the optical fiber, which is about 2 cm by default, should also be considered. The minimum length of the optical fiber useful, for example, in a 15 cm ² binding device is about 4 cm, and such a binding device is suitable for monitoring the fetal vital functions in the prenatal phase. Optimum results were obtained by fixing 2 to 3 m of optical fiber in the binding device, where the life function of the fetus can be detected already during the second half of the second trimester. Longer sections of optical fibers (more than four times the optimum length) in the coupler generally have an even higher sensitivity, but in principle they can also cause undesirable effects (temperature sensitivity, mechanical stresses in the probe, radiation source quality) which ultimately reduce measurement quality . These optimum values were verified for single mode G.652D fibers with 900 µm free protection. Particular values of optical fiber length may vary slightly depending on optical fiber performance / parameters (fiber material, material and presence of primary and secondary protections, fiber refractive index profiles, etc.).

In a preferred embodiment, the primary and / or secondary binding agent for application to the body is provided with a layer of a spreadable binding material, for example sonogel, petrolatum, oil or plasticine. The binding material preferably allows to eliminate or reduce the formation of air bubbles that would otherwise reduce the transmission of the measured signal.

The coupling ratio of the coupler affects the quality of the interference. Therefore, in the preferred embodiment, the coupling member has a uniform separation ratio.

A sampling frequency of 10 to 20 kS / s is sufficient to process signals from the device of the invention. The resolution of the A / D converter is typically 16 or 24 bit, the higher resolution allows to measure weaker signals, ie, the fetal vital function at an earlier stage of development.

In one embodiment, the Mach-Zehnder interferometer is wired, preferably the device comprises a 1 x 2 coupler for splitting the measurement and reference paths, a 3 x 3 coupler for combining said paths, and has an optical fiber to loop measurement length and optical fiber length. with a reference loop selected from 1 to 10 m. The difference in fiber lengths (in the measurement and reference loops) in the preferred embodiment in the case of signal demodulation of multiple photodetectors with typically 3x 3 (or 4x 4) coupler is less than the coherent radiation source length. . The Mach-Zehnder type interferometer is the most advantageous for the purposes of the present invention for economic reasons and due to lower demands on the protection of the radiation source and back reflection.

In another embodiment, the interferometer may be of the Michelson type. Such a device preferably comprises a 3x3 coupler. In the 3x3 coupler, said paths (measuring and reference) are split and merged. The device according to the invention has an optical fiber length with a measuring loop and an optical fiber length with a reference loop selected from 1 to 10 m. The difference in optical fiber lengths (in the measuring and reference loops) is preferred. or 4x 4) the coupler is less than the coherent length of the radiation source. Each of the loops and thus the two outputs of the 3x3 coupler are terminated with a reflective element, and the transmitting unit is connected to the third output of the coupler 3x3 connected to, via an inbuilt or externally connected fiber optic insulator therein. The fiber optic insulator protects the radiation source against reflection. Preferably, the reflective element may be a Faraday mirror, a Bragg grating or a kinked fiber. A Michelson interferometer using a reflective element is economically less advantageous compared to a Mach-Zehnder circuit.

In another possible embodiment, the Sagnac interferometer is wired, preferably the device comprises a single optical fiber 0.1 to 10 km long arranged in a single loop that is both the measuring loop and the reference loop, the measuring path in the loop having the opposite direction to the reference a single 3x3 coupler is located at the intersection of the optical fibers of the loop. At least part of this loop (measurement and

The reference) is fixed in a single primary elastomer binding agent. In this embodiment, the transmitting unit is coupled to the third output of the coupler via a fiber optic insulator incorporated therein or externally connected thereto. The advantage of the Sagnac type interferometer is lower requirements for the radiation source, which can be here also wide-spectrum, with unstable wavelength. The disadvantage of the above-mentioned interferometers is the lower sensitivity to vibrations, which increases with the length of the fiber (several km) in the shoulders, and in the case of too long fibers, the sensor may become incompatible.

The advantage over extrinsity fiber sensors, when the fiber is used only for light / radiation transmission and the sensor itself is then constructed outside the fiber (various cavities, resonators, etc.) or compared to conventional optical sensors, where the fetus is directly irradiated by laser, the whole in-line solution, ie that light does not leave the optical fiber, which carries safety positives, for example, there is no need to address the degree of irradiation of the body by non-ionizing radiation (light).

The advantage is also the possibility of using the device based on the optical interferometer according to the invention and monitoring the condition of the fetus in home conditions, especially due to the ease of application, compact dimensions of the sensor and evaluation unit (PC / tablet).

Clarification of drawings

The principle of the invention is further elucidated by means of exemplary embodiments thereof, which are described using the accompanying drawings, in which:

Fig. 1 schematically illustrates a device according to the invention with a Mach-Zehnder type interferometer, where the measuring line with the measuring loop is fixed in the primary coupling means and the reference path with a reference loop is fixed in the secondary coupling means; Michelson, with two couplers of Fig. 2b schematically illustrates a device according to the invention with a Michelson-type interferometer, with one coupler of Fig. 3a schematically illustrates a device according to the invention with a Sagnac type interferometer with two couplers of Fig. 3b. with one coupler.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be further illustrated, but not limited, by way of example with reference to the accompanying drawings.

The subject of the invention is a device for monitoring the fetal vital signs of the pregnant woman, optionally other mechanical / acoustic manifestations, such as the operation of the uterus and the vital signs of a pregnant woman, comprising an optical fiber sensor as part of an optical fiber interferometer.

The device for monitoring a fetus of a pregnant woman comprises an interferometer and a signal processing unit 3, wherein the interferometer further comprises a transmitting unit 1, a receiving unit 2, and an optical fiber sensor connected thereto by means of optical fibers.

-6GB 307183 B6

The transmitting unit 1 comprises a radiation source 7, preferably a fiber optic insulator 14, and is connected to the optical fibers of the fiber optic sensor.

A suitable radiation source 7 in both the transmitter unit and the fiber optic interferometer of the present invention is a narrow-spectrum laser having sufficient coherence to produce interference. However, any other suitable radiation source may be used, for example, a wide-spectrum LED with correction elements to meet the coherence condition for the single-mode fibers used (standard G.652.D single-mode fibers have a working wavelength in the region of 1280 to 1625 nm). .

The fiber optic sensor is comprised of optical fibers, a primary coupling means 9, at least one coupler 8 in which the signal is divided into two optical paths comprising a fiber optic loop, optionally comprising a secondary coupling means 10, preferably Michelson described below The interferometer may also contain at least one reflective element 11. One so-called measuring path passes through the measuring loop 4, the other the so-called reference path passes through the reference loop 5. These paths are divided in the coupler 8 and depending on the interferometer type

a) conducted in pairs of separate optical fibers to a second coupler 8 (MachZehnder interferometer, see Fig. 1), or

b) guided by a pair of separate optical fibers and, after reflection from the reflective element 11, returned at the end of the optical fibers (Michelson interferometer, see Fig. 2) to the same point and again pass through the coupler 8 (single coupler);

(c) run along a fiber-optic loop circuit (Sagnac interferometer, see Figure 3), where the first measurement path is started in one direction and the second reference path is started in the opposite direction of the same circuit, after returning the signal to the same location; after the second pass of the signal through the coupler 8 (a single coupler), both signals are further fed to the receiver unit 2 with the photodetector 6 by optical fibers.

The optical fibers of the fiber optic sensor are connected to a receiving unit 2 where the signal is received by a photodetector 6, followed by a signal processing unit 3 in which the analog signal is converted by an A / D converter 12 to a digital signal and processed in a digital signal processor. 13 and displayed on a display, such as a monitor, printing in a printer, and the like.

There are several variants of the physical location of the individual components of the invention, some of which are shown in the following exemplary embodiments, but they do not have a limiting effect on the invention. In a first exemplary compact embodiment, the transmitting unit 1, the receiving unit 2 and the signal processing unit 3 are integrated in one housing. In the second exemplary embodiment, a digital signal processor 13 is integrated in the first housing, and in the second housing the transmitting unit 1, the receiving unit 2 and the A / D converter 12 are integrated. Externally to the housing of the first embodiment or the two housings of the second embodiment The sensor is fixed in one primary coupling means 9 or two coupling means 9, 10 where the measuring loop 4, the reference loop 5 and the coupler (s) 8 are fixed in the coupling means or in the two coupling means.

In a third exemplary embodiment, the transmitting unit 1, the receiving unit 2 and the signal processing unit 3 are integrated in one housing. The coupler (s) 8 and the reference loop (s) (s) (s) (s) (s) (s) (s) (s) (s) (s) are / are located in the second housing coupled to the light source and the optical output (s).

- 7 GB 307183 B6

The measuring path for the optical signal routed over the optical fibers of the fiber optic sensor in the section between two couplers 8 (Mach-Zehnder interferometer) or between the first and second pass through a single coupler 8 (Michelson or Sagnac interferometer) at least a portion of which is fixed in the primary bonding means 9, wherein the binding means is an elastomer, for example based on polydimethylsiloxane, into which the optical fiber is fixed, for example by embedding in a certain shape and curing. In the exemplary embodiment, this portion of the measuring loop with the measuring loop 4, which is fixed in the primary coupling means 9, is intended to contact and attach to the body of the pregnant woman in the abdominal area, i.e. near the fetus. probe.

Similarly, the reference path in the section between the two couplers 8 or between the first and second passages of the coupler 8 defines a fiber optic section of the reference path with a reference loop 5 having, in one exemplary embodiment, at least a part fixed in the secondary coupler 10. an elastomer, for example based on polydimethylsiloxane, into which the optical fiber is fixed, for example by embedding in the form of a certain shape and curing. In this case, the contact reference probe can be used for this part of the sensor.

The following basic possibilities of sensing mechanical / acoustic body signals are possible:

a) If the reference line with reference loop 5 is made up only of optical fiber without fixation in the elastomer (in the case of Mach-Zehnder or Michelson interferometer), it is integrated into the box mentioned above. In this case, this part of the sensor can be referred to as a non-contact reference probe.

b) Or, in another exemplary embodiment, at least a portion of the reference loop 5 is fixed in the primary binding means 9 (in the case of a Sagnac interferometer) and is intended only for contact with the abdominal region (near the fetus) by a single binding means. The fiber optic sensor then does not contain the secondary coupling means 10 and only the primary coupling means 9 is in contact with the body, where the reference loop 5 is also the measuring loop

4.

c) Another variant in another exemplary embodiment is that two coupling means are used for contact with the body, which is only possible with a Mach-Zehnder and Michelson interferometer, wherein at least a portion of the reference loop 5 (contact reference probe) is located in the secondary coupling 10. ) and at least a portion of the measuring loop 4 (contact measuring probe) is located in the primary coupling means 9 and each of these means is intended for a different location in contact with the body (e.g., abdominal and reference chest loop) measurement, which is useful for amplifying the signal when sensing fetal vital signs early in pregnancy, which significantly increases system performance and sensitivity of measurement and it is possible to analyze two or more variables, such as pregnant woman's breath, pregnant woman's heart rate and fetal heart rate, one signal.

The sensor and loop fasteners are non-invasive (non-intrusive), ie they are in contact with the outside of the body, ie they do not penetrate into the body of a pregnant woman.

The splitting ratio of the coupler 8 affects the quality of the interference. Ideally, the light is composed with the same intensity, ie, with destructive interference, the intensity of the signals is equal to zero and at the constructive maximum. Therefore, in the preferred embodiment, the coupling member 8 has a uniform separation ratio.

The length of the optical fibers, respectively the distance of the person on which the measuring part of the sensor is placed, from the box with the transmitting unit 1 and the receiving unit 2 etc. is limited only by the maximum possible

Optical fiber length. In the exemplary embodiment, single-mode quartz fibers are used. However, other types of optical fibers may also be used, such as polarization-preserving optical fibers, dual-core and multi-core fibers, plastic single-mode optical fibers, as long as they are suitable for the working wavelength.

The primary coupling means 9 and the secondary coupling means 11 are bodies of a certain shape, with the shape of a base such as a rectangle, square, strip, circle, oval, ring or possibly other shapes. Preferably, the binding means have a base content of 15 to 2500 cm ² , a height of 2 to 10 mm, a weight of 30 to 300 g. In order to increase the probability of signal capture it is advisable to cover a wider area, i.e. From above, the dimensions of the binding means are limited by the price, the maximum possible length of the optical fibers, and the practicality of use according to the shape and range of dimensions that the human body can assume. In principle, the coupling means can be manufactured in multiple dimensions, with a smaller dimension, eg to cover the measured area for smaller persons and for measurements in a smaller space, eg on the side of a pregnant woman, or to a larger dimension, eg to cover an enlarged abdominal area prenatal phase of pregnancy. Another important parameter of said binding means is sufficient weight / volume for the required adhesion / adhesion to the skin. In an exemplary embodiment, the binding means has the shape of a hollow cylinder having a height of 5 mm, a ring-shaped base with an outer diameter of 160 mm and an inner diameter of 100 mm, weighing 75 g and this embodiment has been chosen for universal use. Alternatively, in another exemplary embodiment, the binding means has the shape of a cylinder having a height of 5 mm with a circular base having a diameter of 300 mm and a weight of 300 g.

In order to obtain good measurement results, the coupler must be sufficiently attached to the body surface, such as the skin in the abdominal area, to ensure the best possible transmission of acoustic waves or vibrations from the sensed area. The binding means is made of a suitable material that ensures that a portion of the sensor can easily adhere to the body without the need for external fastening elements. Suitable materials are elastomers which, following substantial deformation by low stresses and releasing this stress at room temperature, quickly return to approximately their original dimensions and shape. Elastomers such as polysulfide masses, polyester masses, polycondensation silicones, polyaddition silicones, vinyl silicones can be used. it must also be suitable for health care. In an exemplary embodiment, the binding agent is a polydimethylsiloxane based material (PDMS, from the group of polycondensation silicones), with the following advantages. The probe is non-toxic, inert, non-toxic, non-flammable, washable, reusable, and its resilience and flexibility allows it to follow the shape of the human body and adhere to it. However, any other elastomer or material meeting said properties and having good adhesion to the skin may be used whose manufacturing conditions for fixing the probe similarly do not allow air access to the probe and the elastomer composition does not compromise the functionality of the probe.

In order to increase signal efficiency and to prevent damping of the transmission of vibrations or acoustic waves, it is necessary to prevent the formation of air bubbles between the sensed surface (eg the abdominal area) and the coupling device. The rigid bonding agent itself is sufficiently adherent, or it is necessary to push out air penetrated between the contact surfaces, however, in order to improve the transmission quality of the acoustic / vibration / mechanical signal and the bonding strength of the bonding agent to the body, the body. The binder is preferably spreadable and may be, for example, gel-based (e.g., sonogel), fat-based (e.g., petrolatum, oil), plasticine, etc., or various binding compositions may be used in combination. In one embodiment, the optical fiber of the measuring loop 4 is fabricated into PDMS elastomers during manufacture, thereby forming a primary coupling means 9 which is coated with a sonogel prior to application to the body.

The principle of vibration / acoustic signal monitoring of the body utilizes the known connections of fiber optic interferometers.

In a preferred embodiment, as shown in Fig. 1, the Mach-Zehnder optical interferometer comprises single mode optical fibers, a 1x2-type coupler 8 for

-9EN 307183 B6 Measurement and reference path splitter, 3x 3 coupler for combining the paths, allowing passive sensor design and passive demodulation of the interferometer signal. The couplers 8 have a uniform split ratio of 50:50 resp. approximately 33:33:33. The laser radiation source 7 with the power of -30 dBm to + 15dBm, which is stored in the transmitting unit I, emits electromagnetic radiation with wavelengths 1280 to 1625 nm, which is transmitted by single-mode optical quartz fibers. The measuring loop 4 and the reference loop 5 each have a length of approximately 8 m, with a length of approximately 2.5 m of the measuring loop 4 being fixed in the primary coupling means 9 and a length of approximately 2 m of the reference loop optical fiber 5 is fixed in the secondary coupling means 10. The difference in optical fiber lengths (in the measuring and reference loop) preferably in the case of signal demodulation by multiple photodetectors 6 with typically 3x 3 (or 4x 4) coupler 8 is less than the coherent length of radiation source 7 . Photodetectors 6 are made of semiconductor materials (eg, InGaAs, Ge) sensitive to working wavelengths in the PIN design (photodiode with PN junction and intrinsic interlayer interconnected in the reverse direction in the photoconductivity mode) or APD (avalanche photodiode, suitable for weak signals). A standard A / D converter 12 for a digital signal processor 13 with a minimum sampling rate of 10 kS / s is connected to the interferometer.

In another exemplary embodiment shown in Fig. 2a, the Michelson optical interferometer comprises single mode optical fibers and a coupler 8 (3x 3 type). In the coupler 8 3x 3d, the above-mentioned paths (measuring and reference) are split and merged. The coupling member 8 has a uniform separation ratio. The laser radiation source 7 with the power of -30 dBm to +15 dBm, which is stored in the transmitting unit 1, emits electromagnetic radiation of wavelengths 1280 to 1625 nm, which is transmitted by single-mode optical quartz fibers. The transmitting unit 1 is connected to the third output of the coupler 8 via a built-in or externally connected fiber optic insulator 14, which protects the radiation source 7 against reflection. The optical fiber with the measuring loop 4 and the optical fiber with the reference loop 5 each have approximately the same length of 10 m and each terminate in a reflective element 11. A length of approximately 3 m optical fiber with the measuring loop 4 is fixed in the primary coupling means 9 and a length of approximately 3 m The reflective element 11, preferably of maximum reflectivity, may be, for example, a Faraday mirror, a Bragg grating or a broken fiber. Photodetectors 6 are made of semiconductor materials sensitive to working wavelengths (eg InGaAs, Ge) in PIN or APD design. A standard A / D converter 12 for a digital signal processor 13 with a minimum sampling rate of 10 kS / s is connected to the interferometer. Fig. 2b shows another possible embodiment of the invention with a Michelson interferometer with one 2x2 coupler 8 and one photodetector 6.

In another exemplary embodiment, as shown in Figure 3a, the Sagnac-type optical interferometer comprises single mode optical fibers and one coupler 8 (type 3x3). The coupling member 8 has a uniform separation ratio. The laser radiation source 7, with power ranging from -30 dBm to +15 dBm stored in the transmitter unit, emits electromagnetic radiation at wavelengths of 1280 to 1625 nm, which is transmitted by single-mode optical quartz fibers. Transmitting unit! is connected to the third output of the coupler 8 3x 3 via a built-in or externally connected fiber optic insulator 14, protecting the laser against reflection. The fiber optic sensor comprises a single optical fiber of 0.1 to 10 km, for example 1 km, arranged in a single loop, which is both the measuring loop 4 and the reference loop 5, the measuring path in the loop having the opposite direction to the reference path in the same loop. and for splitting and merging said paths, one coupler 8 3x3 is positioned at the intersection of the optical fibers of the loop. The sensitivity of the sensor increases linearly with the length of the optical fiber section fixed in the primary coupling means 9, in the exemplary embodiment, the entire 1 km optical fiber section and the coupler 8 were 3x fixed in the primary coupling means 9. The photodetectors 6 are made of semiconductor materials. Ge) sensitive to working wavelengths in PIN or APD design. A standard A / D converter 12 for the digital signal processor 13 is connected to the interferometer

- 10GB 307183 B6 with a minimum sampling rate of 10 kS / s. Fig. 3b shows a possible embodiment of the invention with a Sagnac interferometer with one coupler 8 2x 2 and one photodetector 6.

The A / D converter 12 has a finite sampling rate that affects, for example, the maximum rate / phase change rate that can be monitored. The correct sampling rate is important for undistorted sensing of the analog signal from the photodiodes. A sampling frequency of 10 to 20 kS / s is sufficient for the device according to the invention. The resolution of the A / D converter 12 is typically 16 or 24 bit, a higher resolution allows to measure weaker signals, ie, the fetal life function at an earlier stage of development.

Although the device according to the invention is primarily intended for monitoring the fetal vital signs of a pregnant woman, by sensing acoustic waves / vibrations using the fiber optic sensor according to the invention, a number of bodily vital functions accompanied by mechanical / acoustic activity can be monitored. For example, in the uterus and fetus, fetal heart rate (FHR) can be monitored during fetal heart activity, fetal movement in the uterus, uterine contractions, and other functions. At the same time, the vital functions of a pregnant woman, such as breath, heart rate and blood pressure, and other body indicators in pregnant women can be monitored. In the exemplary embodiment, the basic measurement of the vital functions of the fetus and the pregnant woman is carried out in the sitting or lying positions in the office, hospital room, delivery room or even at home.

The measured data are further analyzed and interpreted. The FHR heart rate is degraded by a number of undesirable components under real conditions. The generally known principle of using adaptive methods is newly applied here also for analyzed data from interferometric measurements according to the invention. By using adaptive measurement signal processing methods that allow the environment in which the filter operates to change over time, so changes in conditions are recorded and the filter coefficients are adjusted depending on the changing environment, these unwanted components can be filtered out, for example filter out superimposing of a stronger MHR heart rate (to avoid contamination of FHR), technical artifacts and biological artifacts (movement artifacts, uterine contractions) to measure fetal heart rate in real conditions.

Industrial applicability

The invention is primarily intended to monitor the fetal vital functions, possibly other mechanical / acoustic manifestations, for example, uterine activity containing the fetus or vital functions of a pregnant woman. In the future it is possible to count on the application for veterinary purposes. Furthermore, modifications can be made to the proposed system for monitoring fetal cardiac activity, uterine contractions during pre-term pregnancy, or to obtain a sound record of heart activity, for example, to monitor cardiac, valvular, breath, or fetal position in the uterus.

Claims (15)

PATENT CLAIMS A device for monitoring a fetal vital sign of a pregnant woman having an optical fiber sensor and a signal processing unit comprising an A / D converter and a digital signal processor, wherein the signal processing unit is connected to an interferometer comprising a transmitting unit (1). a radiation source (7), a receiving unit (2) with at least one photodetector (6) and a fiber optic sensor comprising optical fibers forming the measuring path with the measuring loop (4) connected by means of optical fibers between the receiving unit (2) and the transmitting unit (1); a reference path with a reference loop (5) with at least one coupler (8) at the beginning and end of said paths, characterized in that at least part of the measurement path with the measuring loop (4) of the fiber optic sensor is fixed in the primary coupling means (9) elastomer with a modulus of elasticity of 1 to 10 MPa. A device for monitoring the fetal vital signs of a pregnant woman according to claim 1, characterized in that at least a portion of the reference loop with the reference loop (5) is fixed in the secondary elastomer binding means (10) or in the primary binding means (9). The elastomer has an elastic modulus of 1 to 10 MPa. A device for monitoring the vital functions of a pregnant woman according to any one of claims 1 to 2, characterized in that at least one binding member (8) is fixed in the primary binding means (9) or in the secondary binding means (10). A device for monitoring the vital function of a pregnant woman according to any one of claims 1 to 3, characterized in that the elastomer is polydimethylsiloxane or natural rubber or polyurethane. Device for monitoring the vital signs of a pregnant woman according to any one of claims 1 to 4, characterized in that at least 4 cm of the optical fiber forming the measuring path with the measuring loop (4) are fixed in the primary coupling means (9). A device for monitoring vital signs of a pregnant woman according to claim 5, characterized in that 2 to 3 m of optical fiber forming the measuring path with the measuring loop (4) are fixed in the primary coupling means (9). A device for monitoring the fetal vital signs of a pregnant woman according to any one of the preceding claims, characterized in that the secondary binding means (10) and / or the primary binding means (9) is provided with a layer of a spreadable binding substance, for example sonogel. greases, oils or plasticine. A device for monitoring fetal vital signs according to any one of the preceding claims, characterized in that the A / D converter (12) has a sampling frequency of 10 to 20 kS / s and a resolution of 16 or 24 bit. A device for monitoring vital fetal function of a pregnant woman according to any one of the preceding claims, characterized in that the interferometer is of Mach-Zehnder type. A device for monitoring vital signs of a pregnant woman according to claim 9, characterized in that it comprises a 1x2 coupler (8) for division into a measuring and reference path, a coupler (8) 3x3 for combining said paths, and having an optical fiber length. with the measuring loop (4) and the length of the optical fiber with the reference loop (5) from 1 to 10 m, the difference of these lengths being smaller than the coherent length of the radiation source (7). - 12 GB 307183 B6 A device for monitoring vital signs of a pregnant woman according to claims 1 to 8, characterized in that the interferometer is of the Michelson type. A device for monitoring vital signs of a pregnant woman according to claim 11, characterized in that it comprises a coupler (8) 3x3 for splitting and merging the measurement and reference paths and has an optical fiber length with the measuring loop (4) and an optical fiber length a reference loop (5) from 1 to 10 m, where the difference of these lengths is less than the coherent length of the radiation source (7) and wherein each of the loops and thus the two outputs of the coupler (8) 3x3 are terminated the transmitting unit (1) is connected to the third output of the coupler (8) 3x 3 via a fiber optic insulator (14) built in or externally connected therein. The device for monitoring vital signs of a pregnant woman according to claim 12, characterized in that the reflective element (11) is any of the following: Faraday mirror, Bragg lattice or kinked fiber. 14. A device for monitoring vital signs of a pregnant woman according to claims 1 to 8, wherein the interferometer is of the Sagnac type. A device for monitoring vital signs of a pregnant woman according to claim 14, characterized in that it comprises a single optical fiber 0.1 to 10 km long arranged in a single loop, which is simultaneously the measuring loop (4) and the reference loop (5), wherein the measuring path in the loop has the opposite direction to the reference path in the same loop, and to divide and merge said paths, a coupler (8) 3x3 is located at the intersection of the optical fibers of the loop, and at least a portion of the loop is fixed in the primary coupling means ) of the elastomer, and wherein the transmitting unit (1) is connected to the third output of the coupler (8) 3 x 3 via a built-in or externally connected fiber optic insulator (14).