Patent Description:
<CIT> discloses a tocodynamometer (TOCO) transducer that incorporates a strain gauge, wherein monitoring signals are wirelessly transmitted as optical signals.

<CIT> discloses a fetal motor activity monitoring apparatus comprising a fetal motor activity sensor having a base plate with a base plate topside and a base plate underside for respectively facing away from and towards an expectant mother's abdomen, said base plate topside having at least one elongated planar strain gauge film element defining a nominal measurement plane in a non-flexed state, and having a variable electrical property proportional to resilient elastic flexion in a transverse direction to said measurement plane on application of a bending moment.

Pregnancy monitoring which may be also referred to as fetal monitoring and/or labor monitoring is commonly used in late stages of pregnancy. By way of example, during labor, physiological parameters such as fetal heart rate may be monitored so as to identify signs of fetal distress and/or fetal well-being. Prior to labor, the mother-to-be may undergo one or more medical ultrasound examinations, thereby providing fetal heart rate information, fetal movement information, fetal size information and similar information that is used to identify markers of fetal growth during pregnancy. During labor and birth, also uterine activity, particularly uterine contractions, are frequently monitored.

In gynecology and obstetrics, generally two medical parameters are important to assess the condition of the fetus and the state of delivery. These two parameters are the fetal beat-to-beat heart rate, e.g. measured via an ultrasound Doppler signal, and uterus (or labor) activity. Simultaneous assessment and correlation of the fetal heart rate (FHR) and uterine activity allows an exact determination of the fetal condition. Monitoring systems that are capable of detecting both parameters are frequently referred to as cardiotocographs (CTG monitors). Further, also fetal movement is considered as an indicative parameter for assessing the condition of the fetus.

By way of example, a conventional CTG device (cardiotocography device) may contain an ultrasound Doppler transducer (US transducer) for measuring fetal heart rate (FHR) and detecting fetal movements, as well as a pressure transducer (also called toco transducer, or tocodynamometer) for measuring uterine activity.

Each of the transducers may be placed at the abdomen of the mother, e.g. by an elastic belt fitted around the waist or by an adhesive tape or patch. Each of the transducers may be arranged inside a respective probe. Particularly the ultrasound transducer may be manually placed and positioned so as to seek for a considerably strong signal, e.g. a considerably strong heart beat or heart rate signal. An ideal position of the ultrasound transducer at the expectant mother's abdomen may depend on an actual orientation of the fetus and an actual posture of the mother.

Monitoring the uterine activity is of importance during labor and fetal expulsion. Depending on the intervals of occurrence, intensity, timing patterns and waveform shapes of uterine contractions in connection with the also recorded fetal heart rate, obstetricians can make decisions, for example about possible administration of medication. As indicated above, a common method for noninvasively deriving this information is the use of a so-called tocodynamometer. The tocodynamometer is placed on the abdominal wall and, for instance, held in position with an elastic belt. Tension changes of the uterine muscle during a contraction are registered by a sensitive area arranged in the middle of the sensor housing. The sensitive area is surrounded by a stiff guard ring in order to reduce the influence of overall movement and breathing artifacts.

Several approaches to tocodynamometer design have been proposed, including electromechanical sensor arrangements, pneumatic sensor arrangements, and strain gauge sensor arrangements. By way of example, <CIT> discloses a tocodynamometer comprising an electro-optical transducer, and <CIT> discloses a pneumatic tocodynamometer.

In some tocodynamometers, due to their sensitivity and stability, the conversion of the pressure force to an electrical signal is done by metal strain gauge elements. An important component of this design is the strain gauge element. However, numerous elaborate manufacturing steps for this device like cutting, sputtering, etching, coating and final trimming are required which render the strain gauge element expensive. Further, due to the complex design, the design approach based on metal strain gauge elements is prone to quality variations.

Measuring uterine activity with external sensors that are placed on the abdomen is generally susceptible to sudden and unexpected offset and sensitivity changes. This may involve a temperate drift of the strain gauge element, for instance. Typically, offset and sensitivity of the strain gauge element has to be controlled and adjusted by manual user interaction. To this end, separate operation steps and control elements are required, e.g. control buttons at the transducer's housing.

If the adjustment remains undone, consequences may involve clipped or flat contraction traces on the resulting measurement plot. The permanent re-adjustment and offset control causes additional workload and unnecessary stress for a user, particularly the caregiver.

Hence, there is thus still room for improvement in maternal monitoring transducers, particularly uterine activity transducers.

In view of the afore-going, it is an object of the present disclosure to provide an improved maternal monitoring transducer, particularly a tocodynamometer transducer for measuring uterine activity, that enables a precise detection of maternal motion, involving a considerable degree of accuracy and sensitivity. Further, it would be advantageous to provide a maternal monitoring transducer that is easy to operate. Preferably, manual adjustment and setting operations can be widely dispensed with. Further, it would be beneficial to provide a maternal monitoring transducer that is easy to assemble and easy to manufacture. Preferably, the maternal monitoring transducer is configured in a cost-saving but still reliable and sensitive fashion.

It is a further object of the present disclosure to provide for a maternal and fetal monitoring system that incorporates a respective maternal monitoring transducer. Further, it is an object of the present disclosure to present a method of operating a maternal monitoring transducer.

In a first aspect of the present disclosure, a maternal monitoring transducer that detects uterine activity is presented, the transducer comprising:.

This aspect is based on the insight that the substrate board, particularly the printed circuit board (PCB), that is anyway provided in the transducer may be used to incorporate the measurement arrangement therein, at least in part. Such a substrate board comprises circuitry components, which at least in part enable the sensing functionality of the transducer. In other words, the substrate board itself is used to (mechanically) sense the maternal motion. At the substrate board, at least one displacement-sensitive structure is provided as an integrally part of said substrate which is arranged to be deflected or deformed in response to external motion events, for instance induced by muscular uterine activity. The displacement-sensitive structure is exposed to the maternal motion events.

As a consequence, no separate, distinct displacement measurement sensor is provided that is an additional attachment component. Rather, at least a part of the displacement measurement arrangement is integrally formed with the substrate board. By way of example, a deformable lug or tab may be defined at the substrate board. The deformable lug may be coupled with a sensing section of the transducer that contacts an abdominal portion of the (female) patient. Hence, the displacement-sensitive structure may be deformed or deflected, wherein a deformation degree may be sensed by appropriate components. The advantage of such a displacement measurement arrangement is a reduction in the transducer component's as well as its cost.

The substrate board may be arranged as a fiber reinforced epoxy board. An example for an appropriate material is FR4 based on which printed circuit boards may be formed. The material from which the substrate board is typically formed is at least partially deflectable in a considerably resilient and elastic fashion. Hence, the material for the substrate board is well suited for deflection/deformation measurement. As the deflectable measurement section of the substrate board is an integrally formed part of the substrate board, the displacement measurement arrangement is arranged as an integrated component and not as a separate component that is merely attached to or connected with the substrate board.

The maternal monitoring transducer may be also referred to as tocodynamometer. The maternal monitoring transducer may form a part of a CTG monitoring system. Typically, maternal motion involves muscular uterine activity or uterine contractions.

The displacement-sensitive structure may be arranged as strain-sensitive structure, deflection-sensitive structure and/or motion-sensitive structure.

In accordance with the above-presented aspect, an integrated displacement measurement may be provided which does not require additional, separate displacement sensors that do not use the deformability and/or flexibility of the substrate board material.

The above-presented aspect has the further advantage that standard PCB processes may be used to configure and manufacture the displacement sensing element. Further, a direct integration of the displacement-sensitive structure is achieved which is cost saving and installation space saving. A further benefit is that the number of separate assembly components may be reduced. Further, an increased freedom of design is provided as design restrictions that are inherent to conventional transducers may be overcome. Particularly the housing of the maternal monitoring transducer may be arranged in a more compact fashion.

A further benefit is that more than only one displace-sensitive structure and, accordingly, displacement measurement arrangement may be provided at the substrate board. Hence, maternal motion monitoring may be even more sensitive, for instance involving multiaxial measurements.

A further advantage of the presented approach is that the circuitry components may include at least one signal processing controler enabling software-based automatic signal compensation or correction measures, involving gain adjustment and offset adjustment. This may have the advantage that manual adjustment and working steps, particularly for baseline correction, may be reduced or even avoided.

As a result, the signal provided by the maternal monitoring transducer may be already automatically processed and fitted without manual intervention.

In one exemplary embodiment, the transducer is arranged as a pressure-sensitive maternal monitoring transducer that detects maternal uterine activity indicative information. In other words, the transducer may be arranged as a tocodynamometer transducer. The displacement measurement arrangement may be configured for sensing and monitoring uterine contractions which are indicative of labor.

By way of example, the displacement measurement arrangement may involve a magnetic/inductive displacement sensor. Further, in another exemplary embodiment, the displacement measurement arrangement may involve a capacitive displacement sensor. In yet another exemplary embodiment, the displacement measurement arrangement may involve a conductive deformation sensor. For instance, the conductive deformation sensor may use conductive tracks or traces, wherein the conductivity thereof is dependent on a degree of deformation/deflection of the measurement section of the substrate board.

In yet another exemplary embodiment of the transducer, the displacement measurement arrangement is arranged at the substrate board, wherein the deflectable measurement section is integrally formed in the substrate board. Therefore, the substrate board, particularly the PCB, itself may be deformed so as to detect the maternal motion. The support board forms an integral part of the displacement measurement arrangement.

According to the invention, the displacement-sensitive structure of the displacement measurement arrangement is embedded in the substrate board. For instance, integral conductive layers may be provided at the substrate board that define an electrode, a coil and/or a conductive track.

In another exemplary embodiment of the transducer, the deflectable measurement section is defined by a circumscribing recess that increases the deformability of a residual transitional portion of the substrate board. In other words, the measurement section may be arranged as a lug that forms a deflectable or deformable arm. The recess forms a gap that separates the measurement section from surrounding portions of the substrate board. Consequently, the overall stability and strength of the substrate board is maintained, while the deformability of the transitional portion is deliberately increased. As a consequence, the measurement sensitivity is even further improved. In a further exemplary embodiment, the deflectable measurement section is arranged in a central portion of the substrate structure.

In yet another embodiment of the transducer, the deflectable measurement section is operatively coupled with a contact section that contacts an abdominal portion when the transducer is applied to a maternal patient. For instance, the transducer may be attached to the abdominal portion and secured by a tape, patch, strap or belt. In this way, the contact section is exposed to and may sense, at the abdomen, contractions that are caused by uterine activity (labor contractions). The deflectable measurement section may be mechanically linked with the contact section. Hence, external movements may be transferred to the measurement section. The contact section may be arranged at or form part of the housing.

Preferably, the transducer is a movable compact design transducer that may be basically freely positioned at the abdominal portion of the maternal patient. Hence, depending on the actual posture of the patient, the transducer may be attached at an appropriate position that is suitable for measuring uterine contractions.

In yet another exemplary embodiment of the transducer, the displacement-sensitive structure comprises an inductive coil and a reference element, wherein an actuation of the deflectable measurement section involves relative motion between the inductive coil and the reference element. In this way, an inductive displacement sensor may be provided. Preferably, the conductive coil is embedded in or directly formed at the substrate board. Hence, a deflection of the deflectable measurement section involves a movement of the inductive coil with respect to the reference element.

The inductive sensor may be arranged as a non-contact proximity sensor. The reference element may be arranged as a conductive reference element which may be made from ferrous metal and from non-ferrous metal. For instance, the reference element may be made from aluminum or an aluminum alloy. Electric current in the coil generates a magnetic field, wherein a relative movement between the inductive coil and the reference element influences the magnetic field and the inductance of the coil. This change can be detected by appropriate sensing circuitry which may be as well provided at the substrate board.

In yet another exemplary embodiment of the transducer, the displacement-sensitive structure comprises a trace or coil to which constant current is applied in order to generate a magnetic field. For instance, the coil/trace may be arranged at the deflectable measurement section of the substrate board and a Hall-Effect sensor or a similar sensor may be used that is placed at a defined distance for measuring changes of the magnetic field which are attributable to a deflection of the deflectable measurement section. For instance, the sensor may be placed at or connected with the substrate board as well, preferably at a relatively fixedly attached (i.e. non-deflectable) portion thereof that is spaced away from the deflectable measurement section. In a further exemplary embodiment, a permanent magnet is used that is similarly arranged at the deflectable measurement section.

In yet another exemplary embodiment of the transducer, the displacement-sensitive structure comprises a movable electrode and a reference electrode, wherein an actuation of the deflectable measurement section involves relative motion between the movable electrode and the reference electrode. Hence, the movable electrode and the reference electrode may form a capacitive displacement/proximity sensor. Preferably, the movable electrode is provided at and/or attached to the deflectable measurement section in an integrally formed fashion.

The two electrodes are spaced from one another and define a capacitor the capacitance thereof is dependent on the actual distance between the two electrodes. A capacitance-based sensor is accurate and capable of high-resolution sensing.

In yet another exemplary embodiment of the transducer, the displacement-sensitive structure comprises at least one conductive track that is associated with the deflectable measurement section. By way of example, the conductive track may be arranged as a conductive polymer track. The track may involve a pattern that ensures a certain effective length of the track. Preferably, the at least one conductive track is arranged at the deformable transitional portion. The conductive track does not necessarily cooperate with a reference element. Rather, the deflection and/or deformation of the deformable transitional portion which induces internal tension may influence the conductance of the at least one conductive track. Hence, an actuation of the deflectable measurement section may be reliably detected. Preferably, the conductive track is at least partially arranged in a transitional portion where the deflectable measurement section is coupled with the surrounding substrate board. Hence, the transition region which is exposed to considerable strain may be used for the displacement detection. In other words, the displacement of the displacement-sensitive structure is mediately detected by measuring the strain at the transitional portion.

In yet another exemplary embodiment of the transducer, the displacement-sensitive structure comprises at least one conductive polymer thick-film trace that is associated with the deflectable measurement section. Hence, the conductive track may be formed by at least one thick-film trace from conductive polymer material. Thick-film traces may be for instance formed at the substrate board by printing. Other manufacturing techniques for providing the thick-film traces may be envisaged.

In yet another exemplary embodiment of the transducer, the displacement measurement arrangement comprises double-sided displacement-sensitive structures arranged on opposite sides of the substrate board. This may even further increase the measurement accuracy and reliability. For instance, at a first side, the displacement-sensitive structure may be stretched when the deflectable measurement section is actuated. On the opposite side of the substrate board, the displacement-sensitive structure may be squeezed.

In yet another exemplary embodiment of the transducer, the displacement measurement arrangement comprises a plurality of measurement sections disposed over the substrate board. This may have the advantage that multi axis measurement may be achieved which further increases measurement accuracy and reliability.

In still another exemplary embodiment of the transducer, the displacement measurement arrangement is coupled with a compensation control unit that is arranged to compensate a uterine activity signal, wherein signal compensation involves at least one of drift compensation and offset compensation.

Preferably, the compensation control unit may be at least partially provided as an circuitry component of the substrate board. Hence, also the compensation control unit may be integrally provided and/or incorporated at the transducer. The compensation control unit enables a software-based signal compensation. This aspect is based on the insight that the displacement measurement arrangement, particularly the displacement-sensitive structure and the deflectable measurement section, is susceptible to drift, particularly temperature drift, humidity drift, or pressure drift if the transducer is used under water (when the transducer is used in a bath tube, for instance).

Further, as the transducer may be basically freely arranged at the abdominal portion and secured by a strap or belt, also a wide range of (mechanical) preloading may be present. Preloading may involve a certain range of signal offsets, depending on a current position and state of the transducer at the maternal patient.

For instance, the substrate board, particularly the PCB, may incorporate appropriate sensors, involving temperature sensors, humidity sensors, etc. In this way, the actual performance and characteristics of the displacement measurement arrangement may be monitored. Signals generated and supplied by the sensors may be used to control the compensation measures.

Therefore, applying mathematical methods like statistical analysis, low pass filtering, automatic gain control and/or contraction detection may reduce or even eliminate the need for repeated (manual) check and adjustment. As a result, due to computational control and signal shaping methods, basically considerably inaccurate sensor techniques may be used which are easy to manufacture and also considerably cost-efficient. However, the compensation control unit ensures that the required accuracy and reliability level may be achieved. Further, automatic signal compensation further simplifies operating the transducer as the level of manual intervention may be further decreased.

As a consequence, the displacement measurement arrangement may utilize polymer thick-film resistors, accelerometers, magnetic (inductive) field detectors, capacitive field detectors and further components, depending on an actually implemented displacement measurement principle. Hence, the freedom of design is greatly increased.

In yet another aspect of the present disclosure, a method of operating a maternal monitoring transducer is presented, the method comprising the following steps:.

It shall be understood that the claim method has similar and/or identical preferred embodiments as the claimed device and as defined in the dependent claims.

These and other aspects of the disclosure will be apparent from and elucidated with reference to the embodiments described hereinafter.

In the following, several embodiments of devices and methods that can make use of at least some aspects of the present disclosure will be presented and elucidated in more detail.

<FIG> is a schematic simplified view of a monitoring system <NUM> that is used to monitor the well-being of a pregnant patient and the fetus. The system <NUM> may be also referred to as fetal monitoring system or as maternal and fetal monitoring system.

More particularly, at least in some embodiments, the system <NUM> may be referred to as CTG monitoring system.

The system <NUM> comprises transducers that are attached to the patient <NUM> so as to monitor health indicative signals. The system <NUM>, at least in some embodiments, monitors physiological signals of the maternal patient <NUM> and the fetus <NUM> in the abdominal portion <NUM>.

By way of example, the system <NUM> comprises a fetal monitoring transducer <NUM> and a maternal monitoring transducer <NUM>. In accordance with the exemplary embodiment illustrated in <FIG>, the fetal monitoring transducer <NUM> is arranged to monitor the heart rate of the fetus <NUM>. To this end, the transducer <NUM> may be arranged as an ultrasonic transducer. For instance, the maternal monitoring transducer <NUM> may be arranged to monitor uterine activity, particularly uterine contractions, of the maternal patient <NUM>. To this end, the transducer <NUM> may involve a strain-sensitive and/or displacement sensitive sensor, as will be discussed in more detail herein further below.

The transducers <NUM>, <NUM> may be placed at the abdomen <NUM> of the patient <NUM>. For instance, the transducer <NUM> as shown in <FIG> is secured by a belt or strap <NUM>. Depending on the actual posture and condition of the patient <NUM> and the fetus <NUM>, a proper position and placement for the transducers <NUM>, <NUM> may be chosen. Also the transducer <NUM> may be secured by a strap.

The system <NUM> further comprises a control unit <NUM> which is arranged to receive signals monitored by the transducers <NUM>, <NUM>. The control unit <NUM> is arranged to provide a plot <NUM>, particularly a so-called CTG plot. Further, the control unit <NUM> may be provided with a display <NUM>, user controls <NUM> for operating the system <NUM>, etc..

Via signal cables <NUM>, <NUM>, the transducers <NUM>, <NUM> are coupled with the control unit <NUM>. Hence, in accordance with the exemplary embodiment illustrated in <FIG>, the transducers <NUM>, <NUM> are arranged as wired transducers. However, in alternative embodiments, so-called wireless transducers may be envisaged that communicate with the control unit <NUM> in a wireless fashion.

In <FIG>, an exemplary CTG plot <NUM> is illustrated. The plot <NUM> involves two sections including a signal trace <NUM> that displays a fetal heart rate-indicative signal. Further, a signal trace <NUM> may be provided which displays a uterine activity-indicative signal. A time axis is indicated by reference numeral <NUM>.

In accordance with the present disclosure, the detection of uterine activity is of particular interest. Overall, monitoring both the fetal heart rate and the uterine activity may allow conclusions to be drawn as to the general state of health and stress level of the fetus <NUM>. Further, a correlation of uterine contractions (labor) and a responding increase or decrease in the heart rate of the fetus <NUM> may be monitored.

The uterine activity-indicative signal trace <NUM> includes a baseline <NUM> indicating periods of little or no uterine activity and periods <NUM> of uterine activity including characteristic peaks. For instance, a peak interval of the uterine activity signal <NUM> is indicative of the progress of delivery.

Further reference is made to <FIG> illustrating a simplified schematic perspective bottom view of a maternal monitoring transducer <NUM> that is arranged to monitor uterine activity, particularly uterine contractions. The transducer <NUM> includes a housing <NUM>. Further, the transducer <NUM> incorporates a sensing section <NUM>. The sensing section is actuable (displaceable) when the respective side of the housing <NUM> is attached to the abdomen <NUM> of the female patient <NUM>. In other words, the sensing section <NUM> may be deflected and/or displaced in response to muscular uterine activity. By way of example, the housing <NUM> is arranged in a discoid or cylindrical fashion, wherein the sensing section <NUM> is arranged at a frontal side thereof facing the abdomen <NUM>. So as to allow for the deformability and/or movability of the sensing section <NUM>, a diaphragm <NUM> may be provided. Hence, the sensing section <NUM> may be actuated and displaced relative to the remaining portion of the housing <NUM>.

By way of example, the sensing section <NUM> may be arranged as sensing head or sensing knob. The sensing section <NUM> may be arranged as push button.

In <FIG>, a block arrow <NUM> indicates a direction of an actuating force when a uterine contraction is present. However, as the transducer <NUM> is typically attached to the abdomen <NUM> using a belt or strap <NUM>, also a certain level of preloading may be present that is applied to the sensing section <NUM>. This may further involve a respective drift or changes of the preloading when the transducer <NUM> slips out of place or is deliberately displaced along the abdomen <NUM>. Caregivers and midwives regularly seek for better signals by shifting the position of the transducer <NUM> when the respective signal trace <NUM> (<FIG>) is not yet sufficiently conclusive.

<FIG> illustrates an interior of an exemplary embodiment of a fetal monitoring transducer <NUM>. In <FIG> a perspective top view of the transducer <NUM> is provided. A housing bottom wall of the transducer <NUM> is omitted for illustrative purposes.

In the housing <NUM> of the transducer <NUM>, a printed circuit board (PCB) <NUM> is provided that involves a substrate board <NUM>. By way of example, the substrate board <NUM> may be made from composite material involving fiberglass cloth that is impregnated with an epoxy resin. For instance, so-called FR4 material may be used. Several circuitry components <NUM> are attached to or formed in the substrate board <NUM>. Hence, the transducer <NUM> as such may already provide a certain computing and control capability. An important component of the transducer <NUM> is the uterine activity sensor as such. For instance, a so-called displacement measurement arrangement <NUM> may be provided which is at least partially integrated in the substrate board <NUM> of the PCB <NUM>. In other words, at least a major component of the displacement measurement arrangement <NUM> may be integrally formed with or provided by the substrate board <NUM>. This involves that at least a portion of the substrate board <NUM> is arranged in a displaceable and/or deflectable fashion so as to detect uterine contractions which may be converted into a respective signal (signal trace <NUM> in <FIG>).

In accordance with the present disclosure, the displacement measurement arrangement <NUM> is not arranged as a separate sensor that is merely attached to the substrate board <NUM>. Rather, the substrate board <NUM> is, at least in part, an inherent component of the displacement measurement arrangement <NUM>.

<FIG> shows a simplified top view of a substrate board <NUM> that forms a PCB <NUM>. At the substrate board <NUM>, the displacement measurement arrangement <NUM> is provided. The arrangement <NUM> involves a displacement sensitive structure <NUM> that is arranged to detect deformations and/or deflections of a deflectable measurement section <NUM>. The deflectable measurement section <NUM> may be arranged as a lug or tab formed in the substrate board <NUM>. As shown in <FIG>, the deflectable measurement section <NUM> is encompassed or surrounded by a recess <NUM>.

At a transitional portion <NUM>, the deflectable measurement section <NUM> is connected with a surrounding region of the substrate board <NUM>. Needless to say, the deflectable measurement section <NUM> does not necessarily have to be arranged in a central region of the substrate board <NUM>. Rather, the deflectable measurement section <NUM>, at least in some exemplary embodiments, may be arranged at a boundary region of the substrate board <NUM>.

The material from which the substrate board <NUM> is formed is generally resilient and arranged in an elastic fashion. Hence, in response to an application of force to the deflectable measurement section <NUM>, a certain deformation of the deflectable measurement section <NUM> is present, whereas the deflectable measurement section <NUM> returns to an original position when no force is applied thereto. Also the displacement sensitive structure <NUM> is exposed to the deformations/deflections. Hence, by appropriate circuitry and sensory arrangements, a signal may be generated that is indicative of a current degree of deflection/deformation and, consequently, of a current level of uterine activity.

In contrast to prior art transducers, no separate, additional strain/deflection measurement element is used. Rather, an inherent section of the substrate board <NUM> is mechanically actuable or manipulable and therefore forms a major component of the displacement measurement arrangement <NUM>.

Several principles may be used to detect deformations/deflections of the deflectable measurement section <NUM>. This may involve, for instance, capacitive sensing, inductive sensing, conductivity sensing, accelerometer sensing, Eddy-current sensing, etc..

With reference to <FIG>, several measurement principles will be illustrated. <FIG> illustrate a partial cross-sectional view through an exemplary embodiment of a displacement measurement arrangement <NUM>. An orientation of the views of <FIG> is indicated in <FIG> by a dot-dashed line. In <FIG>, primarily the substrate board <NUM> is illustrated, wherein a deflectable measurement section <NUM> is shown in <FIG> in a non-deflected state and in <FIG> in a deflected state, in response to an application of force (reference numeral <NUM>).

In <FIG>, the displacement sensitive structure <NUM> is not explicitly shown. <FIG> illustrate exemplary embodiments of the displacement measurement arrangement <NUM>. In <FIG>, the deflected state of the deflectable measurement section <NUM> is indicated by dashed lines.

In <FIG>, the displacement sensitive structure <NUM> involves conducting tracks <NUM>, <NUM> which are associated with the transitional portion <NUM> that connects the deflectable measurement section <NUM> and a main portion of the substrate board <NUM>. Consequently, the deflection of the deflectable measurement section <NUM> which causes a deformation of the transitional portion <NUM> is sensed in a mediate fashion. When the deflectable measurement section <NUM> is deflected, one of the conducting tracks <NUM>, <NUM> is squeezed, while the other one is stretched. The deformation of the conducting tracks <NUM>, <NUM> may have an influence on the conductance thereof, and may be sensed by appropriate circuitry. As indicated further above, the conductive tracks <NUM>, <NUM> may be arranged as conductive polymer tracks. More particularly, the tracks <NUM>, <NUM> may be arranged as conductive polymer thick-film traces.

<FIG> illustrates an alternative embodiment of the displacement measurement arrangement <NUM>, wherein the displacement sensitive structure <NUM> involves an inductive coil <NUM> that is arranged to be displaced/moved with respect to a reference element <NUM>. Hence, an inductive proximity sensor is provided that is at least partially integrally shaped with the substrate board <NUM>. Similarly, also a capacitive proximity/motion sensor may be provided, wherein reference numerals <NUM>, <NUM> would in this case represent respective electrodes.

As indicated above, also accelerometer sensors, Eddy-current sensors and further appropriate types of displacement/deformation sensors may used and attached, at least in part, to the deflectable measurement section <NUM>.

Further, in some exemplary embodiments, several types of sensors for sensing the deflection and/or strain of the deflectable measurement section <NUM> are combined. This may enable an even more precise and reliable detection of maternal motion.

<FIG> illustrates by means of a block diagram a schematic simplified layout of a control unit <NUM> for the transducer <NUM>. The control unit <NUM> may be at least partially provided and formed at the substrate board <NUM>. The control unit <NUM> involves an analog control section <NUM> and a digital control section <NUM>. In some embodiments, the digital control section <NUM> may be referred to as compensation control unit.

The analog section <NUM> is arranged to detect the (input) force that causes a deflection of the deflectable measurement section <NUM> of the displacement measurement arrangement <NUM>. The displacement measurement arrangement <NUM> involves a respective sensor which may be arranged as an inductive sensor, a capacity sensor and/or a conductance/conductivity sensor.

The displacement measurement arrangement <NUM> is arranged to provide an analog (electric) signal which is fed to an A/D converter <NUM>. Hence, a digital signal that represents an actual state of deflection/deformation end, consequently, an actual level of uterine activity is provided.

In the digital control section <NUM>, a signal processor <NUM> is provided. The signal processor <NUM> may involve a single processor or a distributed arrangement involving a plurality of processors. The signal processor <NUM> is arranged to process and shape the digital signal provided by the A/D converter <NUM>. Exemplary signal processing measures will be discussed further below. Downstream of the signal processor <NUM>, an interface <NUM> is provided which may be coupled with the (overall) control unit <NUM> of the monitoring system <NUM> by a cable <NUM>, refer also to <FIG>, or in a wireless fashion.

It has been detected that properties and characteristics of the substrate board <NUM> and of further components of the displacement measurement arrangement <NUM> involving the displacement sensitive structure <NUM> are somewhat unsteady and subject to variations in response to temperature changes, humidity changes, etc. Therefore, it may not be unlikely that the detected signal (refer to the signal trace <NUM> in <FIG>) is somewhat corrupted and/or distorted, involving offset and drift phenomena. This applies in particular when environmental conditions are unsteady.

Further, as discussed above, the transducer <NUM> as such is typically not fixedly attached to the abdomen <NUM> of the subject <NUM>. Rather, a somewhat flexible unsteady attachment is used, taking account of the current posture and state of the maternal patient <NUM> and the fetus <NUM>. Also the subject <NUM> is typically not resting in a perfectly immobile fashion.

It is also noted that CTG monitoring typically takes a certain time period, for instance half an hour or even longer. Therefore, it may not be totally unlikely that a certain drift of further distortions are present in the detected uterine activity-indicative signal.

Therefore, it is proposed to apply compensation algorithms to the signal provided by the A/D converter <NUM>. With reference to <FIG>, exemplary signal compensation/shaping measures will be presented. <FIG> shows a signal trace <NUM>. <FIG> shows a signal trace <NUM>. Both signal traces <NUM>, <NUM> may be referred to as uterine activity/contractions traces and may therefore form a part of a CTG plot.

In <FIG>, a time axis is indicated by <NUM>. In <FIG>, a time axis is indicated by <NUM>. In <FIG>, a distortion containing (original) signal is indicated by <NUM>. In <FIG>, a distortion containing (original) signal is indicated by <NUM>. In <FIG>, an assumed (calculated) baseline range is indicated by <NUM> and <NUM>, respectively. The baseline ranges <NUM>, <NUM> shall represent a state where no uterine contractions are present. It is recalled in this context that the uterine activity traces <NUM>, <NUM> typically involve a relative or arbitrary scale as generally an unpredictable level of preloading is present at the transducer <NUM>. Therefore, signal processing measures may be applied that align an actual baseline <NUM>, <NUM> of the signals <NUM>, <NUM> with the baseline range <NUM>, <NUM>.

In <FIG>, the (original) distorted signal <NUM> is subject to an offset distortion (left portion of chart). Reference numeral <NUM> indicates a compensating event, wherein the signal is aligned with the baseline range <NUM>. In <FIG>, a similar compensation is performed at the compensating event <NUM>. In <FIG>, a respectively compensated signal is indicated by <NUM>. In <FIG>, a respectively compensated signal is indicated by <NUM>. As a result of the baseline/offset compensation, the compensated baseline <NUM>, <NUM> is aligned with the preferred baseline range <NUM>, <NUM>. Offset compensation may involve shifting and scaling the signals.

In some exemplary embodiments, compensation events are marked in the CTG plot (reference numeral <NUM> in <FIG>), for instance with a marker character on the record to indicate corrections caused by the signal processing. Hence, further augmented information may be provided in the CTG plot and used for interpreting the measured data.

In <FIG>, a further corrective event is indicated by <NUM>. The compensating event <NUM> involves drift compensation. As can be seen in <FIG>, a slight drift is present in the signals which may be for instance attributable to temperature and/or humidity changes. Hence, the signal baseline <NUM> is again aligned with the preferred baseline range <NUM>.

Further reference is made to <FIG> showing a block diagram illustrating several steps of an exemplary embodiment of a method in accordance with the present disclosure.

The method contains a step S10 involving a provision of a displacement measurement arrangement at a maternal monitoring transducer. Preferably, the displacement measurement arrangement involves a displacement-sensitive structure that is arranged to detect deformations of a deflectable measurement section, wherein the deflectable measurement section is integrally formed/provided in a substrate board of the transducer. In other words, a substrate board, particularly a PCB which is anyway provided at the transducer, may be advantageously used for deflection/deformation measurement.

In a further step S12, deformations and/or deflections of the displacement-sensitive structure are sensed, wherein the deformation/deflections are attributable to respective actuations of the deflectable measurement section.

In a further step S16, a corresponding original signal, particularly a uterine activity signal is supplied which is indicative of uterine activity. The signal is based on the deformations/deflections of the deflectable measurement section sensed by the displacement-sensitive structure.

In yet another step S16, the displacement measurement arrangement is coupled with a compensation control unit which is preferably provided at the substrate board as well. The compensation control unit is arranged to compensate the original signal. Preferably, signal compensation involves at least one of drift compensation and offset compensation.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments and is defined in the appended claims.

Claim 1:
A maternal monitoring transducer (<NUM>) that detects uterine activity, comprising:
- a housing (<NUM>),
- a substrate board (<NUM>) formed as a PCB (<NUM>), disposed in the housing (<NUM>), said substrate board comprising a deflectable measurement section (<NUM>), which is integrally formed in the substrate board (<NUM>), and circuitry components (<NUM>), and
- a displacement measurement arrangement (<NUM>) arranged as an integrated component of the substrate board (<NUM>) and comprising a displacement-sensitive structure (<NUM>) that is arranged to detect deformations of the deflectable measurement section (<NUM>) of the substrate board (<NUM>),
wherein the maternal monitoring transducer (<NUM>) is arranged to supply a maternal uterine-activity indicative signal (<NUM>) based on the detected deformations, and
the maternal monitoring transducer characterised in that
the displacement-sensitive structure (<NUM>) of the displacement measurement arrangement (<NUM>) is embedded in the substrate board (<NUM>).