Device for monitoring uterine contractions

Abstract

The device 10 is for use in monitoring uterine contractions. Means 18 for separately detecting tight (e.g., flush) contact of at least a portion of the device's sensor unit 14 against the abdomen and means 20 for detecting an initial onset or baseline pressure between the sensor unit and the abdomen are provided. A controller 24 is arranged to first detect contact of at least a portion of the sensor unit against the abdomen and then, in response to this contact detection, detect the onset pressure using an integrated pressure sensor. Preferably, the same pressure sensor is used to monitor uterine contractions. The onset pressure provides a direct or indirect measure or indication of the tension in a belt that, in use, is arranged to hold the device against the subject's abdomen. By detecting the onset pressure, e.g., directly in response to abdominal contact being detected, this initial pressure value or a derivative thereof can be used as a direct or indirect indication of the tension in the belt.

Description

Technical Field

[0001] The present invention relates to an apparatus for monitoring uterine contractions and a method for initializing the apparatus.

Background Art

[0002] Monitoring maternal uterine activity during labor and delivery is a standard measurement usually associated with tracking fetal heart rate, often measured using an ultrasonic Doppler. In obstetrics, information regarding uterine contractions (such as contraction duration, contraction strength, contraction waveform, etc.) is important in the assessment of the health status of the fetus during labor and delivery. For example, the interpretation of both uterine activity and fetal heart rate over time can assist medical personnel (such as doctors or caregivers) in providing optimal treatment to the mother and fetus.

[0003] A common technique for non-invasively deriving uterine contractions is to use a tocodynamometer (sometimes called a toc). The tocodynamometer is placed on the maternal abdominal wall and held in place by an elastic belt wrapped around the maternal abdominal circumference. The tocodynamometer includes a pressure sensor housed within a sensor housing. During uterine contractions, changes in the tension of the uterine muscle occur, and these changes are recorded as changes in the force due to pressure in the high-sensitivity region of the pressure sensor, which is located at the center of the sensor housing. The high-sensitivity region is surrounded by a rigid guard ring to reduce the influence of movement and respiratory artifacts. The strain gauge element of the tocodynamometer converts the force due to the above pressure into an electrical signal.

[0004] U.S. Patent No. 3,945,373 discloses another type of tocodynamometer for supplying an electrical output related to the displacement of the patient's body surface. This tocodynamometer includes a light barrier that extends within the space between an emitter and a detector and blocks the light passing from the emitter to the detector. Here, uterine contractions cause displacement of the light barrier and change the amount of light received by the detector from the emitter.

[0005] U.S. Patent Application Publication No. 2012 / 277631 describes other exemplary tocodynamometers. In this example, an optical displacement sensor is also used. A light emitter, a light converter, and a reflector surface are provided that are arranged to reflect at least a portion of the light emitted by the light emitter to the light converter. The reflector is coupled to a displacement member that contacts the abdomen of the subject during use and moves in response to movement of the abdomen. This movement changes the intensity distribution of the light reflected to the light converter.

[0006] The pressure change measurement unit is typically implemented using a pressure sensor that is mechanically coupled to the abdomen via a skin contact area on the bottom surface of the tocodynamometer device. Mechanical forces (uterine activity, changes in muscle tension) are measured by the sensor (i.e., strain gauge element, optical sensor, etc.).

[0007] For optimal performance of the tocodynamometer, the sensing components of the device should be held in a predetermined position relative to the abdomen with an appropriate tension of the elastic belt. The belt tension should ideally meet the following criteria. 1) The belt tension should not be too small, as being too small may cause a loss of physical contact between the abdomen and the sensor element. 2) The belt tension should not be too large, as being too large may cause physical discomfort to the patient. 3) The mechanical force measured by the toc sensor is directly affected by the belt tension. When the toc sensor is first applied to the abdomen, the measured force is the baseline for all other measurements. It is important that the baseline be within the operating range of the measurement sensor. The operating range is defined as the measurement range with the best signal-to-noise performance, high linearity, and / or other factors.

[0008] The belt tension is affected by the movement of the patient's body, the deterioration of the belt elasticity, attempts by medical personnel to increase the belt tension based on their experience, and losses in belt tension due to moisture, for example, when the belt gets wet in a shower or bathtub. It changes over time due to

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] If the tocodynamometer is attached to the abdomen with inappropriate belt tension, this may lead to inaccurate measurements.

[0010] For illustration, FIG. 1 shows a sample measurement signal obtained from a tocodynamometer when it is applied to the abdomen with insufficient belt tension or when uterine contractions are not detected. It is not possible to determine from the signal alone which of these two causes is involved. Therefore, low belt tension may be confused with the absence of contractions altogether, which has harmful clinical implications for the patient.

[0011] FIG. 2 shows a sample measurement signal for the case where the belt tension increases during measurement (resulting in a sharp change in the baseline that is visible near the start of the signal trace), and thus the measurement window is significantly reduced. As a result, the uterine contraction measurement is clipped at the top of the graph. The baseline can be adjusted by post-processing to eliminate the clipping. However, sensors at such high baseline pressures do not operate within their optimal range and thus are prone to reduced sensitivity.

[0012] FIG. 3 shows a sample measurement signal when obtained by a tocodynamometer applied with optimal belt tension. A strong signal is present in the measurement trace and there is no clipping at the upper limit.

[0013] Therefore, it can be seen that belt tension has a significant impact on the quality and reliability of tocodynamometer measurements. Since tocodynamometer measurements are acquired over a medium to long time period (e.g., several hours), inappropriately applied toc sensors may cause loss of useful patient information.

[0014] Therefore, a method for reducing or eliminating this problem is important.

Means for Solving the Problem

[0015] The present invention is defined by the claims.

[0016] According to an example according to an aspect of the present invention, a device for monitoring uterine contractions of a subject, the device comprising: a sensor unit for being arranged against the abdomen of the subject; a belt component for holding the contact surface of the sensor unit in place against the abdomen; contact detection means for detecting the engagement between the contact surface of the sensor unit and the abdomen of the subject; force or pressure detection means for detecting a force or pressure between the abdomen and the sensor unit; and a controller, the controller being configured to: detect the engagement between the contact surface of the sensor unit and the abdomen by the contact detection means; in response to the detection, use the force or pressure detection means to obtain a measured value of an initial pressure or force between the abdomen and the sensor unit; determine whether the tension or applied force of the belt component is within an optimal range by comparing the initial pressure with at least one predetermined reference range; and perform a procedure including: A device is provided.

[0017] The procedure may also be referred to as an initialization, setting, or calibration procedure. This procedure is performed when the device is first attached to the user (i.e., at startup) and may optionally be repeated during use of the device to check the belt tension.

[0018] The predetermined reference range is a reference range for the initial pressure or its derivative, for example, a baseline of the initial pressure.

[0019] The measured value from which the starting pressure is obtained is a pressure value or a pressure signal over a time window.

[0020] Embodiments of the present invention are based on indirectly evaluating the belt tension by an initial pressure measurement obtained as soon as the tokodynamometer device is attached to the abdomen. The starting pressure immediately after the device is attached to the abdomen can be regarded as indicating the level of belt tension, for example, rather than a contraction, because the time for abdominal movement to couple to the pressure sensor has not yet elapsed. The timing of the first attachment to the body can be detected using contact detection means. Thus, by providing a detection unit that incorporates both a contact sensor and a pressure sensor and is configured to obtain an initial pressure measurement in response to detecting skin contact, a reliable measurement value of the belt tension can be obtained.

[0021] Subsequently, this pressure measurement value or its derivative is compared with a threshold value or a reference range to evaluate whether this pressure measurement value or its derivative is within the optimal operating range for the tokodynamometer, for example, for the pressure sensor. This comparison between the starting pressure measurement value or its derivative and the reference range is used to determine whether the belt tension is within its optimal range. If it is not within the optimal range, response measures can be activated, for example, alerting the user or stopping the measurement until the tension is adjusted to the optimal level.

[0022] For example, there is a separate step of determining the measured value of the belt tension based on the detected initial pressure (starting pressure) using an algorithm or conversion formula. In some cases, the belt tension is considered to be equal to, for example, the baseline (i.e., offset) value of the acquired pressure measurement. The reference range is a reference range for the belt tension, and the determination is made based on a comparison of the calculated belt tension with the reference range. The reference range may be a range for the measured initial pressure value itself. Here, for example, the reference range is predefined such that it can be determined that the belt tension is within its starting range when the starting pressure is within this reference range. Therefore, in this case, the measured value of the starting pressure is itself used for further analysis and compared with the reference range. The starting pressure is considered to indicate, for example, the starting belt tension.

[0023] Therefore, apart from the reference range, there is no "optimal range" for the belt tension that needs to be explicitly defined. Determining whether the belt tension is within the optimal range is sufficiently achieved by the use of the reference range and the starting pressure or force measurement. For example, the controller performs an evaluation or analysis of the initial pressure measurement based on the use of the reference range and, based on that evaluation, obtains a classification as within or outside the optimal range for the belt tension. In some examples, the reference range defines, indicates indirectly, or is related to the optimal range for the belt tension.

[0024] The apparatus further comprises an ultrasonic transducer unit including one or more ultrasonic transducers. This can be used to detect and monitor the fetal heart rate using Doppler ultrasound technology.

[0025] Here, since it is important for any transducer to make good acoustic contact with the abdomen for accurate heart rate detection, a separate step of detecting the contact has further benefits. A pressure sensor alone does not always necessarily provide a reliable indication of contact without a gap with the abdomen.

[0026] In addition to the above, the controller is configured to continuously monitor the belt tension even after the pressure measurement for contraction monitoring has started, and to provide a response measure if the tension is outside the optimal range. This is based on, for example, repeatedly or continuously monitoring the pressure signal from the pressure detecting means and obtaining a baseline of the pressure signal, and regarding the baseline value as indicating the belt tension.

[0027] The controller is further configured to generate an information output indicating whether the belt tension is within the optimal range, and communicate the output to a user output device.

[0028] The controller preferably is further configured to monitor uterine contractions based on the output of the force or pressure detecting means. It is preferable to use the same pressure detecting means (for example, a pressure detecting component) to monitor uterine contractions to obtain an initial pressure measurement for checking the belt tension.

[0029] In an advantageous embodiment, monitoring of uterine contractions is performed on the condition that the belt tension is within the optimal range. In other words, the controller is configured to perform the function of monitoring uterine contractions only when the belt tension is within a predetermined optimal range. This avoids obtaining contraction measurement information that may cause inaccurate and thus incorrect clinical measures.

[0030] According to one or more embodiments, an output is generated that communicates to the user output device to alert the user in response to a determination that the belt tension is not within the optimal range. The user output device includes, for example, a display unit and / or one or more other sensory output devices.

[0031] There are various ways to perform contact detection.

[0032] According to one or more embodiments, the contact detection means is provided by the same components as the force or pressure detection means (e.g., a pressure sensor such as a strain gauge or an optical pressure sensor), and the engagement with the abdomen is detected based on detecting a change in the measured force or pressure that exceeds a predetermined threshold value.

[0033] According to a further set of embodiments, the sensor unit includes additional components for detecting contact.

[0034] For example, according to one set of embodiments, the sensor unit includes an optical sensor component including a light source arranged to direct a light output from the contact surface to the skin of the subject and a light detector arranged to detect the light output after passing through the skin at the contact surface, and the contact detection means is provided by the optical sensor component, and the contact is detected based on the output of the light detector.

[0035] In an advantageous embodiment, the optical sensor element is a PPG sensor, and the controller is adapted to determine the pulse of the subject using the output of the PPG sensor. In other words, the sensor unit incorporates an integrated PPG sensor, which includes a light source arranged to direct a light output from the contact surface to the skin of the subject and a light detector arranged to detect the light output after passing through the skin at the contact surface, and the controller is adapted to detect contact using these components of the PPG sensor. In this way, the number of components can be minimized.

[0036] Furthermore, there are various ways to detect the engagement with the abdomen using the optical sensor component.

[0037] For example, in one set of embodiments, the contact is detected based on detecting the light output generated by the light source at the light detector. When the contact is detected, it means that the optical sensor component must be in a state of optical communication with the skin, with light coupled to the light detector through the tissue of the subject, and thus the contact with the abdomen can be considered to be taking place.

[0038] According to a further set of embodiments, the contact is detected based on a detected decrease in light intensity indicating a change from exposure of the photodetector to ambient light to shielding of the light sensor by the surface of the abdomen.

[0039] In this example, the light source need not be activated for contact detection. Engagement with the abdomen can be detected based solely on a change in the photodetector output. The controller is configured to substantially detect engagement with the abdomen based on detection of a decrease in the detected light level.

[0040] For example, in one or more embodiments, the photodetector is adjusted to saturate when exposed to ambient light, and engagement with the abdomen is detected based on a change in the output of the photodetector from a saturated state to an unsaturated state.

[0041] An example according to a further aspect of the invention is a method of initializing or configuring an apparatus for monitoring uterine contractions of a subject, the apparatus comprising a sensor unit arranged to be placed against the abdomen of the subject, a belt component arranged to hold the contact surface of the sensor unit in place against the abdomen, contact detection means for detecting engagement between the contact surface of the sensor unit and the abdomen of the subject, force or pressure detection means for detecting a force or pressure between the abdomen and the sensor unit, comprising the method comprising detecting engagement between the contact surface of the sensor unit and the abdomen, in response to the detection, using the force or pressure detection means (e.g., included within the sensor unit) to obtain a measured value of an initial pressure or force between the abdomen and the sensor unit, determining whether the tension or applied force of the belt component is within an optimal range by comparing the initial pressure with at least one predetermined reference range, providing a method.

[0042] The predetermined reference range is a reference range for the starting pressure or its derivative, for example, for the baseline of the starting pressure.

[0043] The controller is further adapted to monitor uterine contractions based on the output of the force or pressure sensing means, and preferably, the monitoring of uterine contractions is performed on the condition that the belt tension is within the optimal range.

[0044] According to at least one set of embodiments, the step of detecting the engagement between the contact surface of the sensor unit and the abdomen comprises detecting the light received at the contact surface using a light detector; and detecting the engagement based on the output of the light detector. It has.

[0045] According to a further aspect of the present invention, there is also provided a computer program including code means for causing the processor to perform a method according to any of the examples or embodiments outlined above or described below, or according to any of the claims of the present application, when executed on the processor.

[0046] These and other aspects of the invention will become apparent from and will be elucidated with reference to the embodiments (s) described hereinafter.

[0047] For a better understanding of the invention and to more clearly show how the invention is implemented, reference is now made, by way of example only, to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048]

Figure 1

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Figure 5

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Figure 10

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Best Mode for Carrying Out the Invention

[0049] The present invention will be described with reference to the drawings.

[0050] It should be understood that the detailed description and specific examples show exemplary embodiments of the apparatus, system and method, but are for illustrative purposes only and are not intended to limit the scope of the present invention. These and other features, aspects and advantages of the apparatus, system and method of the present invention will be better understood from the following description, the appended claims and the accompanying drawings. It should be understood that the drawings are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings to indicate the same or similar parts.

[0051] The present invention provides an apparatus for monitoring uterine contractions, where means for separately detecting a gapless (e.g., flush) contact of at least a part of a sensor unit of the apparatus with the abdomen and means for detecting an initial starting pressure or baseline pressure detected by a pressure sensor of the sensor unit are provided. A controller is arranged to first detect the above at least partial contact of the sensor unit with the abdomen, and then, in response to the contact detection, to detect a starting pressure using an integrated pressure sensor. Preferably the same pressure sensor is used for monitoring uterine contractions. Using the starting pressure, a direct or indirect measurement or indication of the tension of a belt arranged during use to hold the apparatus against the abdomen of the subject can be provided. For example, directly in response to detecting abdominal contact, by detecting the starting pressure, this initial pressure value or its derivative can be considered to be a direct or indirect indication of the belt tension (not caused, for example, by uterine contraction activity).

[0052] Figure 4 schematically shows in block diagram form some of the functional components of an apparatus according to one or more embodiments of the present invention.

[0053] The apparatus 10 comprises a sensor unit 14 arranged against the abdomen of a subject.

[0054] The apparatus 10 further comprises a belt component 16 arranged to hold the contact surface of the sensor unit 14 in place against the abdomen.

[0055] The apparatus 10 further comprises contact detection means 18 for detecting the engagement of the contact surface of the sensor unit with the abdomen of the subject.

[0056] The apparatus further comprises force or pressure detection means 20 adapted to detect a force or pressure between the abdomen and the sensor unit 14.

[0057] The apparatus further comprises a controller 14 adapted to perform an initialization procedure, the initialization procedure being Detecting the engagement between the contact surface of the sensor unit and the abdomen, in response to the above detection, using force or pressure detection means to obtain a measured value of the starting pressure or force between the abdomen and the sensor unit, based on the starting pressure and at least one predetermined reference range, determining whether the tension or applied force of the belt component is within the optimal range, including.

[0058] The contact detection means, pressure detection means and controller are all integrated into the sensor unit in an advantageous embodiment.

[0059] The predetermined reference range is a reference range for the starting pressure or its derivative, for example, for the baseline of the measured value of the starting pressure.

[0060] The obtained measured value of the starting pressure is a pressure value or a pressure signal captured over a time window.

[0061] Then, this pressure measured value or its derivative can be compared with a threshold value or a reference range to evaluate whether the pressure measured value or its derivative is within the optimal operating range for the tokodyn dynamometer, for example, for the pressure detection means. Using this comparison between the starting pressure measured value or its derivative and the reference range, it is determined whether the belt tension is within its optimal range.

[0062] Using the required starting pressure, a direct or indirect indication of the belt tension can be provided. Based on the measured starting pressure, there may be a further separate step of determining the belt tension, for example using an algorithm or conversion formula, or the starting pressure itself may simply be used as an alternative measurement value for further analysis. For example, the belt tension is considered to be the baseline of the pressure measurement value. This belt tension may optionally be processed using one or more conversion formulas to convert the belt tension into a tension value. If there is a separate step of determining the belt tension, in some examples, this belt tension may be compared with the above reference range rather than the starting pressure measurement value itself.

[0063] Accordingly, according to some embodiments, the belt tension can be indirectly determined by pressure measurement from the pressure sensing means. Preferably, this pressure sensing means is the same pressure sensing means used by the device for measuring uterine contractions. The measured value of the belt tension can be obtained, for example, from the baseline of the pressure signal value of the pressure measurement (this indicates the mechanical force applied to the sensor without uterine contractions).

[0064] The predetermined reference range can correspond, for example, to the optimal range for the belt tension for the pressure sensing means 20 to operate within its optimal sensing range (e.g., maximum sensitivity).

[0065] To illustrate this, next, one exemplary configuration including an exemplary set of parameters will be described with reference to FIG. 5 showing the common part between those parameters.

[0066] For example, the pressure measurement sensor 20 is capable of measuring mechanical forces between 0 N and 15 N. Its optimal range (e.g., where the sensitivity is maximum) is from 1 N to 10 N. In this case, the optimal belt tension is within the range of 2 N to 9 N. Further, the optimal measurement window (which enables sufficient capture of the change in shrinkage pressure) is a pressure measurement window spanning 4 N. This means that the baseline for pressure measurement must be at least 4 N lower than the upper limit of the optimal belt tension range.

[0067] The common part of the ranges is shown in FIG. 5 and, in this specific example, is within the range of 2 N to 5 N. This common part is used as a predetermined optimal (reference) range to be used by the controller 20.

[0068] The above represents just one example of a setting. The exact range and magnitude of the reference range are determined according to the specific pressure sensor 20 and belt 16 used. This range and magnitude are determined in advance and stored in the controller 20 in advance. The controller may have various reference ranges stored for various devices to which the controller is connected. Here, the reference range can be selected by the user at the time of setting using the user interface.

[0069] In a preferred embodiment, after the initialization procedure, the controller 24 is configured to continuously monitor the belt tension by continuously monitoring the pressure measurement repeatedly. The belt tension can be determined, for example, as the baseline of the pressure measurement.

[0070] Preferably, the controller 24 is configured to detect when the belt tension or the baseline of the pressure sensor measurement is outside a predetermined optimal range. An early warning alarm may be implemented by the controller 24. The controller repeatedly detects trends in the belt tension or pressure measurement baseline and, when it detects that the belt tension or pressure measurement baseline will later be outside the optimal reference range at a predetermined time interval (based on that trend), provides an alarm output, for example, to communicate to a user interface.

[0071] The force or pressure sensing means 20 can take various forms. For example, the force or pressure sensing means may include a strain gauge sensor. The force or pressure sensing means may include, for example, a photopressure sensing means including a photodetector and an optical sensor arranged in optical communication and movably arranged relative to each other, and the optical path between the photodetector and the optical sensor varies according to the pressure applied by the abdomen. For example, one of the light source and the photodetector may be fixedly arranged with respect to the abdomen, and the other may be a cantilever member arranged to pivot or bend based on the pressure applied directly or indirectly from the patient's abdomen to the cantilever member. Any other example of a pressure sensor can be used, and various options will be readily apparent to those skilled in the art.

[0072] FIG. 6 shows a plan view of the outside of an exemplary embodiment of the sensor unit 14. FIG. 7 shows (on the left) a perspective view of the sensor unit 14 attached to the patient's abdomen 32 by the belt 16. The belt is wound around the patient's abdomen and extends across the upper part of the housing of the sensor unit, applying a certain pressure to the sensor unit 14 inwardly towards the abdomen 32 to keep the lower contact surface of the sensor unit in firm contact with the abdomen. The belt is, for example, elastic. FIG. 6 shows (on the right) a cross-sectional view of the sensor unit 14 in place with respect to the abdomen, with the belt 16 holding the sensor unit in place. The sensor unit is thus positioned to measure uterine contraction activity.

[0073] The sensor unit 14 may also incorporate one or more ultrasonic transducer elements. Using these ultrasonic transducer elements, one or more physiological parameters of the fetus, such as the fetal heart rate, can be detected. For example, the detection of the fetal heart rate using Doppler ultrasound is a technique well known in the art.

[0074] The controller 24 is further configured to generate an information output indicating whether the belt tension is within the optimal range. The controller communicates or transmits this output to, for example, a user output device. The user output device includes, for example, a display unit and / or one or more other sensory output devices.

[0075] When the initialization procedure is completed, the controller is further configured to monitor the uterine contractions of the subject based on the output of the force or pressure sensing means 20.

[0076] Monitoring uterine contractions based on pressure measurements from a pressure sensor in a tocodynamometer device is a technique well known in the art, and those skilled in the art know how to perform this technique.

[0077] In an advantageous embodiment, the monitoring of uterine contractions is performed exclusively on condition that it is determined that the belt tension is within the optimal range. If the belt tension is not within the optimal range, the uterine contraction monitoring is not activated or is stopped until it is detected that the belt tension is within the optimal range. In this way, the generation of inaccurate and thus clinically false uterine contraction information is avoided.

[0078] In some embodiments, in response to the belt tension not being within the optimal range, an information output is generated that is communicated to the user output device to alert the user. This information output is, for example, an on-screen message displayed on the display unit of the user interface device. The information output includes, additionally or alternatively, an audible alert such as an alarm sound.

[0079] There are various ways to implement the contact detection means 18, and these ways can be used alone or in combination in various embodiments. Next, the selection of these options will be discussed with reference to FIGS. 8 to 10.

[0080] In summary, there are two broad approaches to detecting contact. The first approach is to use the same pressure sensor integrated into the sensor unit 14 that is used to detect pressure measurements to monitor uterine contractions and detect the starting pressure (such as by determining belt tension), and to detect the engagement of the sensor unit with the abdomen. Engagement can be detected, for example, based on detecting a change in the measured force or pressure (the output of the pressure detection means) that exceeds a predetermined threshold. Engagement may be detected based on a change in the baseline of the measured force or pressure that exceeds a predetermined threshold.

[0081] For example, when the sensor unit is applied to the abdomen, a relatively sharp positive shift (or offset) in the baseline of the pressure signal occurs. This is, for example, a sharp change, or a sharp slope of the baseline that exceeds a specific gradient. Thus, detection of contact with the abdomen can be detected based on detecting this shift in the baseline. The baseline can be explicitly extracted, or the change may simply be detected by a sharp positive shift (e.g., occurring over a defined short time window) in the magnitude of the measured pressure signal value.

[0082] A threshold value is defined for changes in the baseline. The threshold value is a threshold value for the magnitude of the baseline shift and / or the gradient of the baseline shift (i.e., how steep or abrupt the baseline change is occurring). One or both of these indicate that contact is being made, and the baseline change corresponds to the initial pressure applied by the abdomen to the bottom of the sensor unit 14. For example, if the baseline shift exceeds x Newtons, where x is a predetermined value, the sensor unit can be considered to be "detected against the abdomen". The threshold value can be determined in advance and stored in the sensor unit controller 24, for example, based on empirical measurements or analytical calculations.

[0083] A second technique for detecting engagement with the abdomen is to include a separate sensor component for detecting contact within the sensor unit 14. There are also various options with respect to this technique.

[0084] One option is to use optical contact detection means. FIGS. 8 and 9 schematically show cross-sectional views of an exemplary device 10 incorporating such optical detection means 18. For the sake of brevity, the controller 24 is not shown, but the controller is also operably coupled to the pressure detection means 20 and the contact detection means 18 and is included within the sensor unit 14.

[0085] In both of the embodiments of FIGS. 8 and 9, the contact detection means 18 includes an optical sensor component having a light source 44 arranged to direct a light output from the (lower) contact surface of the sensor unit 14 to the skin of the subject's abdomen 32, and a light detector 42 arranged to detect the light output after passing through the skin at the contact surface. The contact detection means is provided by the optical sensor component, and contact is detected based on the output of the light detector 42.

[0086] As an example, the light source is an infrared (IR) source and the light detector is an infrared detector. However, alternatively, visible light may be used.

[0087] The light source 44 is an LED in some examples, but this is not essential. The light detector 42 includes one or more photodiodes.

[0088] In an advantageous embodiment, the same optical sensor assembly 18 is used to measure the maternal heart rate. For example, the sensor unit 14 incorporates an integrated optical sensor assembly for the purpose of detecting the heart rate, and the controller 24 is arranged to use this same sensor for the secondary or dual purpose of detecting contact. This minimizes the components in the device, and thus reduces the overall size and manufacturing complexity of the device.

[0089] For example, the optical sensor assembly is a PPG sensor integrated into a unit for determining the pulse, and this PPG sensor includes a light source 44 arranged to direct a light output from the contact surface to the skin of the subject, and a light detector 42 arranged to detect the light output after passing through the skin 32 at the contact surface.

[0090] For example, the optical sensor assembly includes a pair of infrared (IR) transmitter 44 and receiver 42 that can be used to determine the maternal pulse. The transmitter includes, for example, an LED. The receiver is, for example, a photodiode or includes a photodiode. The IR light source 44 irradiates the skin of the abdomen 32, and the photodiode 42 receives the light reflected from the skin, thus measuring the change in light absorption, which corresponds to the change in blood volume. These changes in blood volume (e.g., the frequency of blood volume fluctuations) indicate the maternal pulse.

[0091] For example, in some embodiments, the detection of contact with the abdomen is based on the controller detecting the maternal pulse using the optical sensor assembly. Thus, the detection of the maternal pulse is a criterion for detecting toc sensor contact with the abdomen.

[0092] There are various ways to detect contact using light detection means such as the light detection means outlined above.

[0093] In one set of embodiments, the contact is detected based on detecting the light output generated by the light source 44 at the photodetector 42. When this light output is detected, it means that the photosensor element must be in a state of optical communication with the skin, with light coupled to the photodetector through the tissue of the subject, and thus the contact with the abdomen can be considered to be taking place. This example is shown in FIG. 8.

[0094] In a further set of embodiments, the contact is detected based on using only the output of the photodetector 42. For example, the contact is detected based on detecting a decrease in the detected light intensity at the photodetector, where this decrease, indicating a change from exposure of the photodetector to ambient light to shielding of the photosensor by the surface of the abdomen, for example, is significant.

[0095] For example, the photodetector 42 is adjusted to saturate when exposed to ambient light, and the contact is detected based on a change in the output of the photodetector 42 from a saturated state to an unsaturated state.

[0096] According to a further set of embodiments, the contact detection means includes a capacitive sensor 18 element arranged to capacitively detect the contact between the lower contact surface of the sensor unit 14 and the surface of the abdomen. This example is shown in FIG. 10.

[0097] Further methods of detecting contact with the abdomen include, by way of non-limiting example, a mechanical switch (where contact is detected by mechanical depression of an integrated switch or button exposed at the contact surface), a temperature sensor (where contact is detected based on a detected temperature rise by a specific amount or to a specific value or range), an electrical conduction sensor, and / or a light proximity sensor. In each case, the sensor has a sensitive portion exposed at the contact surface of the sensor unit 14. Combinations of various contact detection methods are also possible.

[0098] According to a further aspect of the present invention, there is further provided a user interface unit that provides a sensory output of the result of the initial pressure detection and / or the result of the belt tension. This user interface unit takes the form of a monitoring unit or a monitoring station, for example, including at least a display device that displays information related to the detected initial belt tension and / or related to the analysis performed by the controller. Preferably, the user interface unit further includes user input means for the user to input control commands for the device, for example, to recheck the belt tension and / or to override various functions of the controller or to adjust a predetermined optimal range for parameters used by the controller, such as the detected belt tension.

[0099] The monitoring unit is, for example, a fetal monitoring unit, which in some examples is configured to display a plurality of measurement information related to the fetus and the mother (for example, the heart rates, blood pressures, body temperatures, and / or contraction activities of the fetus and the mother, as well as the belt tension), and receives sensor inputs from various different physiological sensor sources.

[0100] In some examples, a belt tension indicator is displayed on the display unit of the monitoring device, and this belt tension indicator is a graphic or text indicator in various examples. The belt tension indicator indicates, for example, a real-time evaluation value of the belt tension. The belt tension indicator is in the form of a linear graph scale, and uses a graph to display the belt tension in the form of a linear graph scale representing the optimal range for the belt tension within the scale, so that the person involved (for example, a clinician) can easily know when the belt tension is likely to be outside the optimal range.

[0101] In some examples, the sensor unit 14 is arranged to be visible on the outer surface of the housing of the sensor unit 14 and includes a visual indicator configured to provide a visual indication of the current belt tension and / or to indicate whether the belt tension is within an optimal range. The visual indicator includes, for example, a plurality of colored lights (e.g., LEDs). Different colors are used to indicate different grades or levels of belt tension, for example, a first color (too low tension), a second color (tension within the optimal range), and a third color (too high tension). The first color, the second color, and the third color can be, for example, blue, green, and red. This is merely an example and does not limit the present invention.

[0102] The monitoring unit or sensor unit is configured to generate an audible or visual signal to alert the user when the belt tension is outside the optimal range and thus adjustment is required. For example, an alarm is sounded.

[0103] An example according to a further aspect of the present invention is a method of initializing a device for monitoring uterine contractions of a subject, the device comprising a sensor unit for placement against the abdomen of the subject, a belt component for holding the contact surface of the sensor unit in place against the abdomen, and the method comprising detecting an engagement between the contact surface of the sensor unit and the abdomen, in response to the detection, using force or pressure sensing means to obtain a measured value of an initial pressure or force between the abdomen and the sensor unit, determining whether the tension or applied force of the belt component is within an optimal range based on the initial pressure and at least one predetermined reference range, and providing a method.

[0104] The predetermined reference range is a range for the initial pressure or its derivative, for example, a baseline of the initial pressure.

[0105] The implementation options and details for each of the above steps are understood and interpreted according to the description and explanation presented above for the apparatus aspect (i.e., the apparatus aspect) of the present invention.

[0106] Any of the features or details of the examples, options, or embodiments described above with respect to the apparatus aspect (with respect to the apparatus) of the present invention may be applied to, combined with, or incorporated into the present method aspect of the present invention with necessary modifications.

[0107] The method further comprises the step of monitoring uterine contractions based on the output of the force or pressure detecting means, and monitoring the uterine contractions is performed on the condition that it is determined that the belt tension is within the optimal range.

[0108] The step of detecting the engagement between the contact surface of the sensor unit and the abdomen using a light detector to detect the light received at the contact surface, and detecting the engagement based on the output of the light detector. has.

[0109] By way of example, a workflow according to one or more embodiments is outlined in FIG. 11.

[0110] The contact detection means 18 is arranged, for example, to detect the contact between the sensor unit 14 and the abdomen (62) using one or more of the methods outlined above. The controller repeatedly or continuously monitors the signal from the contact detection means to confirm whether contact is being made (64). As soon as contact is made, the belt tension is determined (66) based on obtaining an initial or starting measurement value from the pressure detection means integrated into the contact detection surface of the sensor unit. For example, the belt tension is regarded as the baseline of the pressure signal output from the pressure detection means immediately in response to detecting the contact. Additionally or alternatively, an algorithm or conversion formula may be applied to convert the measured pressure or baseline pressure into a belt tension value.

[0111] The determination (68) is made as to whether the belt tension is within a defined belt tension range. This determination can be made in a variety of ways. The value of the belt tension can be calculated from the initial pressure measurement and compared to a predetermined reference range for the belt tension. Alternatively, the reference range can be predefined for the initial pressure measurement itself or for a baseline of the initial pressure measurement, and this reference range is pre-calculated such that an initial pressure measurement value within this range implies that the belt tension is within its optimal range.

[0112] If it is determined (68) that the belt tension is outside the optimal range, the measurement of contraction by the device is stopped (74), and an alarm message (e.g., visual or audible) can be generated to alert the user that the belt tension needs to be adjusted. The belt tension is displayed on a display unit visible to the operator. Thereafter, the workflow returns to the start step, where contact with the sensor unit is detected again (62), and another start measurement of pressure is reacquired to recheck the belt tension.

[0113] This loop continues until a determination (68) is made that the belt tension is within the optimal range. At this point, measurement and monitoring of uterine contractions can be performed using the pressure sensing means 20 within the sensor unit 14. A check (70) is made as to whether contraction measurement is already in progress, and if so, the contraction measurement can continue and the workflow returns to the step of checking contact and rechecking the belt tension. If not, the contraction measurement is initiated (72) and the workflow returns to start (62) at this point. In this way, in any case, the workflow repeatedly or continuously rechecks the belt tension even after measurement has been started to determine whether the belt tension remains within the optimal range. At any point, if the belt tension is outside the range, the measurement is stopped (74) until the tension is adjusted.

[0114] Optionally, an early warning function may be included such that an early warning is issued when the belt tension is approaching the limit of the optimal tension range, for example, within a predetermined vicinity or threshold of either the upper or lower limit of the optimal tension range.

[0115] An example according to a further aspect of the present invention also provides a computer program product including code means configured to cause the above-described processor to perform a method according to any of the examples or embodiments outlined above or described below, or according to any of the claims of the present application, when executed on the processor.

[0116] As described above, embodiments utilize a controller 20. The controller can be implemented in a plurality of ways using software and / or hardware to perform the various required functions. A processor is an example of a controller that uses one or more microprocessors programmed with software (e.g., microcode) to perform the required functions. However, the controller can be implemented with or without using a processor, or as a combination of dedicated hardware for performing some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) for performing some other functions.

[0117] Examples of controller components used in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field programmable gate arrays (FPGAs).

[0118] In various implementations, a processor or controller is associated with one or more storage media such as volatile and non-volatile computer memories like RAM, PROM, EPROM, and EEPROM (registered trademark). The storage media are encoded with one or more programs that perform the required functions when executed on one or more processors and / or controllers. The various storage media may be mounted within the processor or controller or may be transportable such that one or more programs stored thereon can be loaded into the processor or controller.

[0119] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the terms "comprising," "including," and "having" do not exclude other elements or steps, and the singular forms do not exclude a plurality.

[0120] A single processor or other unit may perform the functions of several items recited in the claims.

[0121] The mere fact that certain measured values are recited in mutually different dependent claims does not indicate that a combination of these measured values cannot be advantageously used.

[0122] A computer program is stored / distributed on a suitable medium such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

[0123] It should be noted that when the term "configured to" is used in a claim or specification, this term "configured to" is intended to be equivalent to the term "adapted to."

[0124] None of the reference signs in the claims shall be construed as limiting the scope thereof.

Claims

1. An apparatus for monitoring uterine contractions of a subject, the apparatus comprising: a sensor unit for placement against the abdomen of the subject; a belt component for holding the contact surface of the sensor unit in place against the abdomen; contact detection means for detecting engagement between the contact surface of the sensor unit and the abdomen of the subject; force or pressure detection means for detecting a force or pressure between the abdomen and the sensor unit; a controller, wherein the controller is configured to: detect, by the contact detection means, engagement between the contact surface of the sensor unit and the abdomen; in response to the detection, obtain a measured value of an initial pressure or force between the abdomen and the sensor unit using the force or pressure detection means; perform a procedure including determining whether the tension or applied force of the belt component is within an optimal range by comparing the initial pressure with at least one predetermined reference range. Apparatus.

2. The apparatus according to claim 1, wherein the controller further generates an information output indicating whether the tension of the belt component is within the optimal range and communicates the information output to a user output device.

3. The apparatus according to claim 1 or 2, wherein the controller further monitors uterine contractions based on the output of the force or pressure detection means.

4. The apparatus according to claim 3, wherein the monitoring of the uterine contractions is performed on the condition that the tension of the belt component is within the optimal range.

5. The apparatus according to any one of claims 1 to 4, wherein an output is generated and communicated to the user output device to alert the user in response to a determination that the tension of the belt component is not within the optimal range.

6. The sensor unit includes an optical sensor component including a light source arranged to direct a light output from the contact surface to the skin of the subject and a light detector arranged to detect the light output after passing through the skin at the contact surface, the contact detection means is provided by the optical sensor component, and the engagement with the abdomen is detected based on the output of the light detector. The apparatus according to any one of claims 1 to 5.

7. The apparatus according to claim 6, wherein the engagement with the abdomen is detected based on detecting the light output generated by the light source at the light detector.

8. Contact is Based on the detected decrease in light intensity indicating a change from exposure of the light detector to ambient light to shielding of the light detector by the surface of the abdomen the apparatus according to claim 6, wherein the apparatus is detected. **Claim 9** The apparatus according to claim 8, wherein the light detector is adjusted to be saturated when exposed to ambient light, and the contact is detected based on a change in the output of the light detector from a saturated state to an unsaturated state. **Claim 10** The apparatus according to any one of claims 6 to 9, wherein the light sensor component is a PPG sensor, and the controller obtains the pulse of the subject using the output of the PPG sensor. **Claim 11** The apparatus according to any one of claims 1 to 10, wherein the contact detection means is provided by the same component as the force or pressure detection means, and the engagement is detected based on detecting a change in the measured force or pressure exceeding a predetermined threshold value. **Claim 12** A method of operating an apparatus for monitoring uterine contractions of a subject, the apparatus comprising: a sensor unit for placement against the abdomen of the subject; a belt component for holding the contact surface of the sensor unit in place against the abdomen; contact detection means for detecting an engagement between the contact surface of the sensor unit and the abdomen of the subject; force or pressure detection means for detecting a force or pressure between the abdomen and the sensor unit; a controller; and comprising: The method comprising: detecting, by the contact detection means, an engagement between the contact surface of the sensor unit and the abdomen; in response to the detection, obtaining, by the force or pressure detection means, a measured value of an initial pressure or force between the abdomen and the sensor unit; determining, by the controller, whether the tension or applied force of the belt component is within an optimal range by comparing the initial pressure with at least one predetermined reference range; a method having. **Claim 13** The method according to claim 12, further comprising the step of the controller monitoring uterine contractions based on the output of the force or pressure detection means, and the step of the controller monitoring the uterine contractions is performed on the condition that the tension of the belt component is within the optimal range. **Claim 14** The contact detection means includes a light detector, and the step of the contact detection means detecting an engagement between the contact surface of the sensor unit and the abdomen is The step of the light detector detecting the light received at the contact surface; The step of the controller detecting the engagement based on the output of the light detector; The method according to claim 12 or 13, comprising:

15. A computer program comprising code means for causing the processor to perform the method according to any one of claims 12 to 14 when executed on the processor.

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