The present disclosure relates to liquid sensing in an ostomy appliance. In particular, the present disclosure relates to a monitor device of an ostomy system configured to sense the presence of liquid and to differentiate the nature of the liquid based on electrical readings.

Brief description of the drawings

The accompanying drawings are included to provide a further understanding of embodiments and are incorporated into and a part of this specification. The drawings illustrate embodiments and together with the description serve to explain principles of embodiments. Other embodiments and many of the intended advantages of embodiments will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.

Fig. 1 illustrates an exemplary layout of electrodes of a sensor assembly according to an embodiment of the invention,

Fig. 2A illustrates an exemplary situation of a liquid 99, emanating from the stomal opening 101, causing a bridge to form between the first electrode 111 and the second electrode 112 of the sensor assembly,

Fig. 2B illustrates an evolving case of the exemplary situation in Fig. 2A,

Fig. 3A illustrates a schematic graph of the electrical resistance R as a function of time t, R(t), for each of the primary sensor SI and the secondary sensor S2 (dashed) in an exemplary case,

Fig. 3B illustrates a schematic graph of the electrical resistance R as a function of time t, R(t), for each of the primary sensor SI and the secondary sensor S2 (dashed) in an evolved situation of the case in Fig. 3A,

Fig. 3C illustrates a schematic graph of the electrical resistance R as a function of time t, R(t), for each of the primary sensor SI and the secondary sensor S2 (dashed) in an exemplary case, and

Fig. 4 illustrates a flow diagram of an exemplary method of determining an operating state of an ostomy appliance of an ostomy system as performed in a monitor device of the ostomy system.

Detailed description

Various exemplary embodiments and details are described hereinafter, with reference to the figures when relevant. It should be noted that the figures may or may not be drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be noted that the figures are only intended to facilitate the description of the embodiments. They are not intended as an exhaustive description of the invention or as a limitation on the scope of the invention. In addition, an illustrated embodiment needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated, or if not so explicitly described.

Throughout this disclosure, the words "stoma" and "ostomy" are used to denote a surgically created opening bypassing the intestines or urinary tract system of a person. The words are used interchangeably, and no differentiated meaning is intended. The same applies for any words or phrases derived from these, e.g., "stomal", "ostomies" etc. Also, the solid and liquid wastes emanating from the stoma may be referred to as both stomal "output," "waste(s)," "liquids," and "fluids" interchangeably. A subject having undergone ostomy surgery may be referred to as "ostomist" or "ostomate" - moreover, also as "patient" or "user". However, in some cases "user" may also relate or refer to a health care professional (HCP), such as a surgeon or an ostomy care nurse or others. In those cases, it will either be explicitly stated, or be implicit from the context that the "user" is not the "patient" him- or herself.

In the following, whenever referring to proximal side or surface of a layer, an element, a device or part of a device, the referral is to the skin-facing side or surface, when a user wears the ostomy appliance. Likewise, whenever referring to the distal side or surface of a layer, an element, a device or part of a device, the referral is to the side or surface facing away from the skin, when a user wears the ostomy appliance. In other words, the proximal side or surface is the side or surface closest to the user, when the appliance is fitted on a user and the distal side is the opposite side or surface - the side or surface furthest away from the user in use.

The axial direction is defined as the direction of the stoma, when a user wears the appliance. Thus, the axial direction is generally perpendicular to the skin or abdominal surface of the user.

A radial direction is defined as perpendicular to the axial direction. In some sentences, the words "inner" and "outer" may be used. These qualifiers should generally be perceived with respect to the radial direction, such that a reference to an "outer" element means that the element is farther away from a centre portion of the ostomy appliance than an element referenced as "inner". In addition, "innermost" should be interpreted as the portion of a component forming a centre of the component and/or being adjacent to the centre of the component. In analogy, "outermost" should be interpreted as a portion of a component forming an outer edge or outer contour of a component and/or being adjacent to that outer edge or outer contour. The use of the word "substantially" as a qualifier to certain features or effects in this disclosure is intended to simply mean that any deviations are within tolerances that would normally be expected by the skilled person in the relevant field.

The use of the word "generally" as a qualifier to certain features or effects in this disclosure is intended to simply mean - for a structural feature: that a majority or major portion of such feature exhibits the characteristic in question, and - for a functional feature or an effect: that a majority of outcomes involving the characteristic provide the effect, but that exceptionally outcomes do not provide the effect.

The present disclosure provides an ostomy system, a method for determining an operating state of an ostomy appliance of an ostomy system, and a monitor device of an ostomy system.

In a first aspect of the invention, an ostomy system is disclosed. The ostomy system comprises a monitor device and an ostomy appliance, the ostomy appliance comprising a sensor assembly. The sensor assembly comprises a stomal opening with a centre point. The sensor assembly comprises three or more electrodes including a first electrode arranged at a first radial distance from the centre point, a second electrode arranged at a second radial distance from the centre point, and a third electrode arranged at a third radial distance from the centre point. The second radial distance is greater than the first radial distance is greater than the first radial distance and the third radial distance is greater than the second radial distance. The first electrode and the second electrode form a primary sensor, and the first electrode and the third electrode form a secondary sensor. The monitor device comprises a processor, a memory connected to the processor, a first interface connected to the processor, the first interface being configured for connecting the monitor device to the sensor assembly. The monitor device is configured to determine a first value of an electrical quantity of, such as associated with, the primary sensor, to determine a second value of the electrical quantity of, such as associated with, the secondary sensor, and to determine an operating state of the ostomy appliance based on at least the absolute difference between the first value and the second value.

In embodiments, the sensor assembly is provided in a base plate of the ostomy appliance. In embodiments, the sensor assembly is provided in a sensor patch of the ostomy appliance, the sensor patch being configured for attachment to an adhesive proximal surface of a base plate. In embodiments, the stomal opening and the centre point of the sensor assembly is aligned with a stomal opening and centre point of a base plate or sensor patch of the ostomy appliance.

The present disclosure relates to an ostomy system and devices thereof, such as an ostomy appliance, a base plate for an ostomy appliance, a sensor patch for application to a base plate, a monitor device, and optionally one or more accessory devices. Further, methods related to the ostomy system and devices thereof are disclosed. An accessory device (also referred to as an external device) can be a mobile phone or other handheld device, such as a smart device including a smartphone or a smartwatch. In embodiments, an accessory device is a personal electronic device, e.g., a wearable, such as a watch or other wrist-worn electronic device. An accessory device can be a docking station. In embodiments, the docking station is configured to electrically and/or mechanically couple the monitor device to the docking station. In embodiments, the docking station is configured for charging a battery of the monitor device and/or configured for transferring data between the monitor device and the docking station. The ostomy system can comprise a server device. In embodiments, the server device is operated and/or controlled by the ostomy appliance manufacturer and/or a service centre.

The present disclosure provides an ostomy system and devices thereof, such as an ostomy appliance, a base plate for an ostomy appliance, a sensor patch for application to a base plate, a monitor device, and optionally one or more accessory devices which either alone or together facilitate reliable determination of the nature, severity, and rapidness of moisture propagation in the adhesive material provided for attaching the base plate and/or sensor patch to the skin surface of a user. Depending on the nature of the pattern of moisture propagation in the adhesive, the ostomy system and devices thereof enable providing information to the user about the type of failure, such as adhesive failure patterns, and in turn enable providing an indication to the user of the severity and thus the remaining time frame for replacing the ostomy appliance without experiencing severe leakage and/or skin damage.

In embodiments, the ostomy appliance includes a base plate, such as a monolithic, one-piece base plate, e.g., integrated with a sensor assembly part, or a separate sensor assembly part, such as a sensor assembly part to be subsequently applied to a base plate. In embodiments, the sensor assembly part is a sensor patch for application to the base plate, such as the proximal surface of the base plate. Thereby, an arbitrary base plate, such as a conventional base plate provided with the sensor patch, can achieve the features as described herein. Features as described with respect to sensing/monitoring capabilities of the base plate herein can be provided by a sensor assembly of a sensor patch to be applied to a base plate, e.g., by the user, and vice versa. In embodiments, the sensor patch is adapted to adhere to a base plate. In embodiments, the sensor patch comprises a first adhesive layer adapted to adhere to the skin surface of a user.

In embodiments, a method of attaching a base plate having sensing capabilities, e.g., through the provision of a sensor patch, to a user's stoma and/or skin surrounding the stoma, such as the peristomal skin area, comprises attaching the sensor patch to a base plate and attaching the base plate, i.e., together with the attached sensor patch, to the user's stoma and/or skin surrounding the stoma, such as the peristomal skin area. Alternatively, the method of attaching the base plate to the user's stoma and/or skin surrounding the stoma comprises attaching the sensor patch to the user's stoma and/or skin surrounding the stoma and attaching the base plate to the user's stoma and/or skin surrounding the stoma above the attached sensor patch, i.e., on a distal surface of the sensor patch.

In embodiments, the ostomy appliance comprises a base plate and an ostomy pouch (also referred to as an ostomy bag). The ostomy appliance can be a colostomy appliance, an ileostomy appliance, or a urostomy appliance. In embodiments, the ostomy appliance is a two-part ostomy appliance, i.e., the base plate and the ostomy pouch are releasably coupled e.g., with a mechanical and/or an adhesive coupling, e.g., to allow that a plurality of ostomy pouches can be utilized (exchanged) with one base plate. Further, a two-part ostomy appliance can facilitate correct application of the base plate to skin, e.g., to an improved user sight of the stomal region. In embodiments, the ostomy appliance is a one-part ostomy appliance, i.e., the base plate and the ostomy pouch are fixedly attached to each other. The base plate is configured for coupling to a user's stoma and/or skin surrounding the stoma, such as a peristomal skin area.

In embodiments, the ostomy system comprises a base plate or a sensor patch for application to a base plate. In embodiments, parts of the ostomy system are incorporated into a base plate or a sensor patch for application to a base plate. In embodiments, the first adhesive layer of the ostomy system is a first adhesive layer of a base plate or a sensor patch for attachment to a base plate. In embodiments, the first adhesive layer and the sensor assembly of the ostomy system are incorporated into a base plate or sensor patch to provide such with the ability to indicate a site of leakage. In embodiments, the ostomy system provides a base plate and/or a sensor patch with the ability to indicate a site of leakage from an ostomy appliance, e.g., from the base plate.

The ostomy system comprises a first adhesive layer with a proximal surface configured for attachment to the skin surface of a user and a distal surface. In embodiments, the first adhesive layer of the ostomy system is provided as part of a base plate or a sensor patch. In embodiments, the base plate and/or the sensor patch comprises the first adhesive layer and the sensor assembly of the ostomy system according to the first aspect of the invention. The first adhesive layer comprises a stomal opening, such as a first adhesive stomal opening, with a centre point, or is at least prepared for forming a stomal opening with a centre point.

During use, the first adhesive layer adheres to the user's skin (peristomal area) and/or to additional seals, such as sealing paste, sealing tape and/or sealing ring. Thus, in embodiments, the first adhesive layer is configured for attachment to the skin surface of a user, e.g., for attachment of a base plate and/or the sensor patch to the skin surface of a user. A first adhesive layer, e.g., when embodied in a base plate and/or a sensor patch, according to the present disclosure enables detection of presence of liquid or output on the proximal surface of the first adhesive layer (in the interface between a skin surface of the user, such as the peristomal skin area, and the proximal surface of the first adhesive layer).

The ostomy appliance comprises a sensor assembly. The sensor assembly has a stomal opening with a centre point, such as a stomal opening and centre point aligned with a stomal opening and centre point of a base plate and/or sensor patch incorporating the sensor assembly. In embodiments, the sensor assembly is attached to the distal surface of the first adhesive layer. In embodiments, the sensor assembly is attached to the proximal surface of the first adhesive layer. In embodiments, the sensor assembly is attachable to the distal surface or the proximal surface of the first adhesive layer. In embodiments, the sensor assembly is embedded in the first adhesive layer, i.e., the sensor assembly is covered by an adhesive layer, such as the first adhesive layer, on each (proximal and distal) side. The sensor assembly comprises at least two sensors; a primary sensor and a secondary sensor. In embodiments, the sensor assembly comprises two, three, four, five, or six sensors. In embodiments, the sensor assembly comprises more than six sensors. The sensors are arranged to facilitate detection of liquid on the proximal surface of the first adhesive layer, e.g., on the proximal surface of a base plate and/or a sensor patch incorporating parts of the ostomy system. Detection of liquid can be indicative of output present in the interface between the first adhesive layer and the skin surface, which eventually can cause leakage from the first adhesive layer, i.e., output escaping the base plate and causing distress to the user. Thus, it is desired to provide a warning before such leakage. By liquid is meant in particular all types of output emanating from a stoma, varying from highly viscous output to solid output. Further, in embodiments, by liquid is meant moisture, such as moisture absorbed by the first adhesive layer. Thus, in the following, a reference to liquid is meant at least a reference to all types of output. In the following, whenever referring to an interface is meant the interface between the first adhesive layer and the (peristomal) skin surface, unless otherwise specified.

The sensor assembly comprises three or more electrodes including a first electrode, a second electrode and a third electrode. In embodiments, the electrodes extend in an appliance plane of the sensor assembly and/or the base plate or sensor patch incorporating the sensor assembly.

The electrodes are electrically conductive and can comprise one or more of metallic (e.g., silver, copper, gold, titanium, aluminium, stainless steel or other), ceramic (e.g., ITO or other), polymeric (e.g., PEDOT, PANI, PPy or other), and carbonaceous (e.g., carbon black, carbon nanotube, carbon fiber, graphene, graphite, or other) materials. In embodiments, the electrodes can be wire electrodes or one-dimensional electrodes resembling a string or wire. In embodiments, the electrodes can have a width and/or thickness being considerably smaller than their length. In embodiments, the width and/or thickness of the electrodes can be up to 50 times smaller than the length of the electrodes. In embodiments, the electrodes can be less than 3 mm wide, and more than 100 mm long. In embodiments, the electrodes are printed on a support layer, whereby the electrodes comprise, such as consist of, conductive traces of a conductive ink, e.g., silver ink or carbon ink suitable for printing on a surface. Thus, in embodiments the electrodes comprise, such as consist of, a (hardened/cured) conductive ink. In embodiments, conductive ink is created by infusing graphite, silver, or other conductive materials, into ink. In embodiments, the support layer is stretchable, flexible and/or elastic. In embodiments, the support layer is flexible and elastic. In an embodiment, the support layer is made of a polymeric material In embodiments, the support layer is made of polyurethane (PU), e.g., thermoplastic polyurethane (TPU). In alternative embodiments, the support layer material can be made of or comprise one or more of PTFE, PVDF, polyester (e.g., PET), a thermoplastic elastomer (TPE), polyamide, polyimide, Ethylene-vinyl acetate (EVA), polyurea, and/or silicones. Exemplary thermoplastic elastomers (TPEs) of the support layer include styrenic block copolymers (TPS, TPE-s), thermoplastic polyolefin elastomers (TPO, TPE-o), thermoplastic Vulcanizates (TPV, TPE-v), thermoplastic polyurethanes (TPU), thermoplastic copolyester (TPC, TPE-E), and thermoplastic polyamides (TPA, TPE-A). In embodiments, the support layer has a thickness of less than 0.1 mm, such as less than 50 pm.

In embodiments, the sensor assembly, the base plate, and/or the sensor patch comprises a monitor interface. In embodiments, the monitor interface is configured for electrically and/or mechanically connecting the ostomy appliance (base plate and/or sensor patch), in particular electrodes of the sensor assembly, to the monitor device. In embodiments, the monitor interface is configured for wirelessly connecting the ostomy appliance (base plate and/or sensor patch) to the monitor device. Thus, the monitor interface of the sensor assembly, base plate, and/or the sensor patch can be configured to electrically and/or mechanically couple the electrodes, and thus the sensors formed therefrom, and the monitor device.

In embodiments, the monitor interface of the sensor assembly, base plate, and/or the sensor patch comprises, e.g., as part of a first connector of the monitor interface, a coupling part for forming a mechanical connection, such as a releasable coupling between the monitor device and sensor assembly, base plate, and/or the sensor patch. In embodiments, the coupling part is configured to engage with a coupling part of the monitor device for releasably coupling the monitor device to the sensor assembly, base plate, and/or the sensor patch.

In embodiments, the sensor assembly is arranged on a distal side of the first adhesive layer. In embodiments, the sensor assembly is arranged at least partially in contact with a distal surface of the first adhesive layer, such that the sensor assembly may determine electrical properties of the first adhesive layer. In embodiments, the first adhesive layer is provided with a plurality of sensor point openings, such as at least 10, or at least 20, sensor point openings. In embodiments, the plurality of sensor point openings are aligned with at least parts of the three or more electrodes of the sensor assembly. In embodiments, the sensor point openings provide a passage from the proximal surface of the first adhesive layer to the distal surface of the first adhesive layer, such that liquid, such as stomal output and/or sweat, may form a bridge in the interface between the skin and the proximal surface between neighbouring electrodes, such that current may pass through the bridge of liquid and cause an electrical signal, such as a short-circuit.

The first electrode is arranged at a first radial distance rl from the centre point, the second electrode is arranged at a second radial distance r2 from the centre point, and the third electrode is arranged at a third radial distance r3 from the centre point. The second radial distance r2 is greater than the first radial distance rl, such that r2 > rl, and the third radial distance r3 is greater than the second radial distance r2, such that r3 > r2, and such that r3 > r2 > rl. Where more than three electrodes are provided, the same relationship may apply to such further electrodes, such that the electrodes are provided at increasing (e.g., discrete) radial distances.

In embodiments, the radial distances from the centre point are fixed/constant about the centre point, such that the mutual radial distances between each of the electrodes are likewise fixed/constant. In embodiments, the radial distances vary, such as where the electrodes are provided in a wavy pattern, but the average radial distance may be constant. Thus, in embodiments, by the radial distance is meant the average radial distance, such as to account for minor wavy patterns, such as wave patterns providing a certain stretchability to the electrodes.

In embodiments, the three or more electrodes are arranged concentrically about the centre point.

In embodiments, the three or more electrodes are arranged concentrically about the centre point in an angle space of at least 180 degrees, or at least 270 degrees. Thereby, a sensing coverage of at least 180 degrees or at least 270 degrees about the centre point, and as such the stoma, is provided. By concentrically is meant that the radial distance is fixed (or average thereof, as explained above) relative to the centre point for each of the three or more electrodes, and consequentially that the mutual distance (or average thereof) between neighbouring electrodes is fixed. Thereby, as will be explained further below, the monitor device may be configured to determine a speed of propagation by having such mutual radial distance stored in a memory.

The first electrode and the second electrode form a primary sensor. The first electrode and the third electrode form a secondary sensor. By forming a sensor is meant that the monitor device is configured to apply a voltage across the two electrodes forming the respective sensor. Thus, a potential difference/voltage can be applied across the sensor, i.e., across the first electrode and the second electrode to form the primary sensor and across the first electrode and the third electrode to form the secondary sensor, by means of a monitor device or a power source. In other words, in embodiments, the monitor device is configured to form a primary sensor by applying a voltage across the first electrode and the second electrode, and to form a secondary sensor by applying a voltage across the first electrode and the third electrode. Thus, in an embodiment, to determine a first value and a second value comprises applying a voltage across the primary sensor and the secondary sensor and monitoring the associated current, respectively.

By monitoring an electrical quantity across/between the two electrodes of the sensor, changes in such electrical quantity can be attributed to changing conditions of the surroundings, such as increasing or decreasing moisture content in the first adhesive layer and/or presence of liquid forming a liquid path between such two electrodes, and hence a short-circuit, between the two electrodes. Thereby is realized a sensor configured to detect/arranged to facilitate detection of liquid on the proximal surface of the first adhesive layer and hence, by means of the monitor device, provide a warning to the user that a leakage is imminent.

According to embodiments of the ostomy system disclosed herein, the primary sensor covers a region closer to the stomal opening (namely because the radial distances of the first and second electrodes forming the primary sensor are less than the radial distance of the third electrode; (rl < r2) < r3), whereas the secondary sensor covers a larger area including the region more distant (greater radial distance) from the stomal opening. In other words, the secondary sensor covers part of the region covered by the primary sensor and a region more distant from the stomal opening (in particular the region between the second electrode and the third electrode). In other words, an overlap between the primary sensor and the secondary sensor exists, namely because the first electrode forms part of both the primary sensor and the secondary sensor. In the following, the effects of this build/design are discussed in greater detail.

In embodiments, the monitor device comprises a housing, a processor, a memory connected to the processor, and a first interface connected to the processor, the first interface being configured for connecting the monitor device to the sensor assembly. In embodiments, the first interface is configured for obtaining ostomy data from the sensor assembly, e.g., the base plate and/or the sensor patch comprising a sensor assembly and coupled to the first interface. The ostomy data comprises primary ostomy data from a primary sensor of the sensor assembly, e.g., of the base plate and/or the sensor patch comprising a sensor assembly, and secondary ostomy data from a secondary sensor of the sensor assembly, e.g., of the base plate and/or the sensor patch comprising a sensor assembly. The first interface of the monitor device may comprise a plurality of terminals, such as two, three, four, five, six, seven or more terminals, for forming electrical connections with respective terminals and/or electrodes of the ostomy appliance, in particular the sensor assembly as discussed herein. One or more terminals of the first interface may be configured for forming electrical connections with an accessory device, e.g., with respective terminals of a docking station. The first interface may comprise a ground terminal. The first interface may comprise a first terminal, a second terminal and optionally a third terminal. The first interface may comprise a fourth terminal and/or a fifth terminal. The first interface optionally comprises a sixth terminal. In one or more exemplary monitor devices, the first interface has M terminals, wherein M is an integer in the range from 4 to 8.

The monitor device comprises a power unit for powering the monitor device. The power unit may comprise a battery. The power unit may comprise charging circuitry connected to the battery and terminals of the first interface for charging the battery via the first interface, e.g., the first connector. The first interface may comprise separate charging terminal(s) for charging the battery.

The monitor device may comprise a sensor unit with one or more sensors. The sensor unit is connected to the processor for feeding sensor data to the processor. The sensor unit may comprise an accelerometer for sensing acceleration and provision of acceleration data to the processor. The sensor unit may comprise a temperature sensor for provision of temperature data to the processor.

The monitor device is configured determine a first value of an electrical quantity of the primary sensor and to determine a second value of the electrical quantity of the secondary sensor. For example, the first value of an electrical quantity of the primary sensor is the size/magnitude of the concerned electrical quantity associated with the primary sensor (e.g., the resistance of material disposed between the first electrode and the second electrode), and the second value of the (same, to provide a meaningful analysis) electrical quantity of the secondary sensors is the size/magnitude of the electrical quantity associated with the secondary sensor (e.g., the resistance of material disposed between the first electrode and the third electrode).

By an electrical quantity is meant any of at least resistance, conductance, impedance, admittance, and capacitance. In an embodiment, the electrical quantity is selected from resistance, impedance, and capacitance. In embodiments, the electrical quantity is selected from the reciprocals/inverse of resistance, impedance, and capacitance. In embodiments, the electrical quantity is measured in an a.c. (alternating current) setup or a d.c. (direct current) setup.

Thus, by an electrical quantity is meant any descriptive quantity suitable for representing the electrical properties of the sensor and surroundings thereof (e.g., material disposed between the electrodes forming the sensor). In embodiments, the surroundings of a sensor herein, as is explained above, may be an adhesive composition capable of absorbing moisture or the vicinity thereof (e.g., the skin surface and liquids disposed thereon, such as in the interface), whereby the electrical properties thereof change, which will be noticeable from monitoring an electrical quantity. In an embodiment, the electrical quantity is indicative of an electrical property of an adhesive composition of the ostomy appliance and/or the sensor assembly. In embodiments, the adhesive composition is an adhesive of a base plate or a sensor patch of the ostomy appliance, such as a first adhesive layer as previously discussed. In embodiments, the eiectricai quantity is indicative of an eiectricai property of the (immediate) surroundings of the respective sensor, such as the adhesive composition and/or a surface of a iayer of the ostomy appiiance, such as the presence of iiquid on a proximai (skin-facing) surface of the ostomy appiiance.

In the foiiowing, when providing iiiustrative examples of the principies of the present invention, resistance is considered, but it is appreciated that such eiectricai quantity may as weii be substituted by any of conductance, impedance, admittance and capacitance by choosing appropriate thresholds and equipment, without departing from the scope of the invention. Thus, for the purpose of discussing the principies, resistance is considered, and it is noted that presence of moisture and/or iiquid in the surroundings of a sensor wiii cause the resistance across the sensor to decrease due to the increased conductance of current through such medium (adhesive or iiquid path).

By a vaiue of an eiectricai quantity is meant the numericai magnitude of the specific eiectricai quantity. In other words, in embodiments, the monitor device is configured to determine, e.g., the resistance (or any of the iisted eiectricai quantities herein) of the primary sensor and the resistance of the secondary sensor.

The monitor device is configured to determine an operating state of the ostomy appiiance based on at ieast the absolute difference between the first vaiue and the second vaiue. Thus, the monitor device is configured to caicuiate an absolute difference between, e.g., the resistances of each of the two sensors. In other words, the monitor device can determine the difference in, e.g., resistance between the primary sensor and the secondary sensor. By using the absolute difference, the choice of eiectricai quantity is reduced, as it is noted that using the conductance (the reciprocai of resistance) might cause a negative difference. However, for the purpose of determining an operating state, oniy the size, and thus the absolute, of the difference is considered according to the present embodiment. In aiternative embodiments, the monitor device is configured to determine an operating state of the ostomy appiiance based on at ieast the difference between the first vaiue and the second vaiue.

In embodiments, the operating state is indicative of a degree of radiai erosion of the base piate, such as of the first adhesive iayer, and/or the presence of (e.g., propagating) iiquid in the interface between the ostomy appiiance (such as a base piate or a sensor patch) and the skin surface, and as such being indicative of an acute ieakage risk for the ostomy appiiance. For exampie, an operating state may be indicative of a ievei of erosion of the adhesive properties of the adhesive of the base piate and/or sensor patch incorporating the sensor assembiy. In embodiments, an operating state is indicative of the dynamic internai state of the ostomy appiiance, reiated to the adhesive performance of the ostomy appiiance. Adhesive performance of the ostomy appiiance may be related to the condition inside the adhesive layer (e.g., which may affect by several factors such as humidity, temperature, misplacement of the ostomy appliance on the stoma, and/or malfunction of the ostomy appliance) and/or related to misplacement of the ostomy appliance on the stoma, and/or malfunction of the ostomy appliance. In embodiments, the operating state is indicative of the presence of liquid in the interface between the skin surface and the ostomy appliance, such as the position (angular and/or radial), amount and/or speed of propagation of the liquid in the interface. In embodiments, an operating state may be an indication that everything is fine, i.e., that no erosion and/or presence of liquid has been detected. Thus, in embodiments, the operating state is indicative of any condition of the ostomy appliance.

Due to the arrangement of electrodes and the corresponding formation of sensors according to embodiments of the first aspect of the invention, the operating state may, in embodiments, be determined solely based on the absolute difference between the first value and the second value of the primary and secondary sensors, respectively, as was disclosed above.

In case output starts propagating from the stoma (arranged within the stomal opening and coinciding with the centre point), it will first reach, and cause a change of, e.g., resistance, by the primary sensor. Such change is reflected by a change of the first value: in the case of monitoring resistance, the first value will decrease (e.g., short-circuit due to the presence of a liquid path between the first electrode and the second electrode) and change relative to the second value. The change of the first value due to the presence of liquid will result in an (absolute) difference between the first value and the second value since the output has not (yet) reached and formed a liquid path between the first electrode and the third electrode (i.e., across the secondary sensor). Hence, the (absolute) difference between the first value and the second value may be indicative of liquid propagating in a direction radially away from the centre point, which would most likely be stomal output. Thereby, an operating state may be determined based on the absolute difference between the first value and the second value.

Thereby is realized an ostomy system and corresponding monitor device and method for determining an operating state of an ostomy appliance by means of a simple electrode layout and a simple operation of the monitor device. In particular, since output propagates radially away from the source (the stoma), the monitor device of the ostomy system and the corresponding method is capable of differentiating stomal output from other liquids, such as sweat forming uniformly on the peristomal skin surface.

In further embodiments, an auxiliary sensor may be formed (by applying a voltage) between the second electrode and the third electrode, such as to provide a back-up for confirming the presence of liquid bridging the two sensors in the interface. Further, the presence of the auxiliary sensor may provide for determining whether liquid is propagation in a radial direction away from the stoma/centre point (e.g., most likely stomal output) or in a radial direction towards the stoma/centre point (e.g., due to external water entering the interface, e.g., due to swimming). The monitor device may be configured to determine an auxiliary value of the electrical quantity and to determine a signed difference between the auxiliary value and the first value and a signed difference between the auxiliary value the second value. Further, the monitor device may be configured to determine an operating state indicative of liquid propagating in a radial direction towards the centre point based on the signed difference between the auxiliary value and the first value. For example, where the electrical quantity is resistance, a low auxiliary value and a high first value may be indicative of liquid in the vicinity of the auxiliary sensor but not in the vicinity of the first sensor, and as such, that liquid has occurred in the outermost region of the sensor assembly; namely by the auxiliary sensor formed by the second electrode and the third electrode (being arranged at greater radial distances from the centre point than the first electrode).

Providing an ostomy system having sensing capabilities, e.g., through a base plate comprising an incorporated sensor assembly or through a sensor patch comprising a sensor assembly, provides for an optimum or improved use of an ostomy appliance of the ostomy system. In particular, it is facilitated that a base plate is not changed too late (leading to adhesive failure, leakage and/or skin damage), or at least that a user is informed that a leakage will happen, is happening, or has happened. Accordingly, the user or a health care professional is able to monitor and plan the use of the ostomy appliance. In an embodiment, the monitor device is configured to determine the operating state based on compliance of the absolute difference between the first value and the second value with a primary threshold value. In embodiments, the monitor device is configured to determine the operating state based on at least one of (i) the absolute difference between the first value and the second value and (ii) on compliance of the absolute difference between the first value and the second value with a primary threshold value.

Thereby, the first value must change a certain amount relative to the second value (i.e., the absolute difference has to be larger than the primary threshold value) before the operating state is changed, such as to be indicative of the presence of liquid, in particular output, in the interface. Thereby is provided a system providing for the operating state not changing too often, but only when a significant change (determined by the value of the primary threshold value) in the absolute difference occurs.

In an embodiment, the monitor device is configured to determine a first initial baseline of the electrical quantity of the primary sensor and a second initial baseline of the electrode quantity of the secondary sensor in response to a connection between the monitor device and the sensor assembly. Thereby, in response to the monitor device being connected to the sensor assembly, the monitor device is configured to determine a first and second initial baseline of the primary and secondary sensors, respectively. For example, the first and second initial baselines are the average first and second values, respectively, collected within a certain time-period, such as less than 5 minutes, following the connection between the monitor device and the sensor assembly. Thereby, such baselines may form basis for further data analysis, as it may be assumed, at least by the monitor device, that the first and second initial baselines are the respective initial values of the primary and secondary sensors prior to exposure to moisture, liquid, or other substances. In embodiments, the time-period for determination of the first and second initial baselines may be less than 10 minutes following the connection between the monitor device and the sensor assembly. Alternatively, the time-period may be between 5 seconds and 10 minutes, such as between 10 seconds and 5 minutes. In general, the time-period should be less than the time between application of the ostomy appliance to the skin surface and an expected onset of changes in the adhesive performance of the base plate or sensor patch incorporating the sensor assembly, such as changes due to absorption of moisture, such as sweat.

In an embodiment, the determination of the operating state is based on a deviation of the first value from the first initial baseline and/or a deviation of the second value from the second initial baseline. Thereby, the operating state may be determined based on the absolute difference and a deviation of any of the first and second values from their respective initial baselines. In embodiments, a deviation of any of the first and second values from the respective initial baselines may be a deviation by at least a secondary threshold value from the respective initial baseline. Thereby, minor fluctuations do not cause the determination of a (new) operating state, whereas larger deviations, exceeding such secondary threshold value may cause a change of operating state.

For example, where an operating state indicative of stomal output in the vicinity of the primary sensor (example provided above) was previously determined, a new operating state may be determined by further considering a deviation of any of the first and second values from their respective initial baselines. For example, in an embodiment, the determination of the operating state is based on a previous operating state and on a deviation of the second value from the second initial value. In particular, following an operating state indicative of stomal output in the vicinity of the primary sensor, the monitor device may update/determine a new operating state if the monitor device determines that the second value deviates from the second initial baseline. If the previous operating state was indicative of stomal output in the interface by the primary sensor, a change of value of the second value is likely caused by the stomal output having propagated to cause the change of the second value. In other words, the monitor device may determine a new operating state indicative of the stomal output having propagated to the third electrode (as this forms part of the secondary sensor). Thereby is realised a monitor device and corresponding method for detecting the propagation of output in the interface by means of solely the absolute difference (as used to determine the previous operating state) and the deviation of the second value from the second initial baseline.

On the contrary, the monitor device may determine an operating state indicative of sweat/moisture forming in the interface if the absolute difference between the first and second values remains constant (such as below the primary threshold value) but both the first value and the second value deviate from their respective initial baselines. For example, the formation of sweat is likely to form uniformly about the stoma and cause erosion of the adhesive in contact with the sensor assembly, and such erosion may be detected through a uniform decrease of resistance

Thereby, the monitor device and corresponding method is capable of detecting, and differentiating, stomal output from sweat by means of the same sensors (primary and secondary sensors) and without requiring modification of the adhesive layer. In particular, the monitor device and corresponding method according to the present disclosure is capable of providing selectivity towards the type of liquid (stomal output or sweat) and indication on propagation of output by means of a sensor assembly comprising merely three electrodes forming two sensors.

In embodiments, the monitor device is configured to determine the operating state based on at least one of (i) the absolute difference between the first value and the second value, (ii) on compliance of the absolute difference between the first value and the second value with a primary threshold value, (iii) a deviation of the first value from the first initial baseline and/or a deviation of the second value from the second initial baseline and (iv) a previous operating state and on a deviation of the second value from the second initial value.

In an embodiment, the determination of the operating state is based on a time difference between a deviation of the first value from the first initial baseline and a deviation of the second value from the second initial baseline. Thus, in embodiments, the monitor device is configured to record a first time stamp indicative of the time of recording the first value deviating from the first initial baseline and to record a second time stamp indicative of the time of recording the second value deviating from the second initial baseline, and to determine a time difference based on said first time stamp and second time stamp.

In embodiments, a deviation of any of the first and second values from the respective initial baselines may be a deviation by at least a secondary threshold value from the respective initial baseline. Thereby, minor fluctuations do not cause the determination of a (new) operating state, whereas larger deviations, exceeding such secondary threshold value may cause a change of operating state. In embodiments, the radial distance between the three or more electrodes is fixed/constant and stored in a memory of the monitor device. By considering the time difference between deviations of the first and second values from their respective initial baselines, a speed of propagation may be determined based on such time difference. In particular, the speed of propagation may be determined in units of length per unit time, such as mm/min, if the radial distance between the electrodes is known. Thereby, the operating state may be indicative of a speed of propagation of output propagating in the interface between the skin surface and the ostomy appliance or be indicative of an urgency of action needed to avoid leakage onto clothes.

In embodiments, a high time difference, such as a time difference above a first time threshold, may be indicative of a slow propagation of output and/or indicative of presence of sweat rather than output, such as if the time difference is above a second time threshold greater than the first time threshold. In embodiments, a low time difference, such as a time difference lower than a third time threshold, may be indicative of a quickly propagating output in the interface.

As such, the time difference, in particular in combination with the fixed distance between the electrodes, provides further insights into the nature of the liquid as detected in the interface, as is reflected by the determined operating state.

In embodiments, the monitor device is configured to determine the operating state based on at least one of (i) the absolute difference between the first value and the second value, (ii) on compliance of the absolute difference between the first value and the second value with a primary threshold value, (iii) a deviation of the first value from the first initial baseline and/or a deviation of the second value from the second initial baseline, (iv) a previous operating state and on a deviation of the second value from the second initial value and (v) a time difference between a deviation of the first value from the first initial baseline and a deviation of the second value from the second initial baseline.

In an embodiment, the operating state is selected from a plurality of operating states including an operating state indicative of presence of stomal output in an interface between the skin surface and the ostomy appliance and an operating state indicative of presence of sweat in the interface. In embodiments, the operating state indicative of presence of sweat in the interface may be an operating state indicative of moisture absorbed in an adhesive composition of the base plate or the sensor patch of the ostomy appliance. Further, the plurality of operating states may include a default operating state indicative of neither presence of stomal output nor sweat/moisture.

For example, as previously discussed, in an embodiment, in accordance with at least the absolute difference being in non-compliance with the primary threshold value, the operating state is indicative of presence of stomal output in the interface. Thereby, based on, in embodiments, a single parameter - the absolute difference - an operating state may indicate the reason to liquid in the interface; presence of stomal output or presence of sweat. In other words, the layout of electrodes including as few as three electrodes may be used, by appropriate configuration of the monitor device according to embodiments of the present invention, to determine operating states indicative of different sources of liquid in an interface between a skin surface and an ostomy appliance.

In embodiments, the plurality of operating states includes at least two, such as at least three, operating states. In embodiments, the plurality of operating states includes between 2 and 10 operating states, such as between 3 and 10 operating states, such as between 3 and 6 operating states. Thereby, a user is presented a limited number of operating states, such that the presented information is more comprehensible. For example, the limited number of operating states may be formed by appropriate use of threshold values, such that minor changes of the first and second values of the electrical quantity are grouped in a single operating state.

In an embodiment, the monitor device further comprises a second interface comprising a transceiver module connected to the processor and configured for connecting the monitor device to an accessory device of the ostomy system. In an embodiment, the monitor device is configured to transmit a primary signal indicative of the operating state. The second interface may be configured as an accessory interface for connecting, e.g., wirelessly connecting, the monitor device to one or more accessory devices. The second interface may comprise an antenna and a wireless transceiver, e.g., configured for wireless communication at frequencies in the range from 2.4 to 2.5 GHz. The wireless transceiver may be a Bluetooth transceiver, i.e., the wireless transceiver may be configured for wireless communication according to Bluetooth protocol, e.g., Bluetooth Low Energy, Bluetooth 4.0, Bluetooth 5. The second interface optionally comprises a loudspeaker and/or a haptic feedback element for provision of an audio signal and/or haptic feedback to the user, respectively.

Thereby, the determined operating state and/or related data may be transmitted, through the primary signal indicative of such operating state and/or related data, to an accessory device, such as a smartphone running an app configured to indicate the operating state, such as in a graphical user interface.

In a second aspect of the invention, a method, performed in a monitor device of an ostomy system, for determined an operating state of an ostomy appliance of the ostomy system is disclosed. The ostomy appliance comprises a sensor assembly having a stomal opening with a center point. The sensor assembly comprises three or more electrodes including a first electrode arranged at a first radial distance from the center point, a second electrode arranged at a second radial distance from the center point, and a third electrode arranged at a third radial distance from the center point, wherein the second radial distance is greater than the first radiai distance and the third radiai distance is greater than the second radiai distance. The first eiectrode and the second eiectrode form a primary sensor, and the first eiectrode and the third eiectrode form a secondary sensor. The monitor device comprises a processor, a memory connected to the processor, and a first interface connected to the processor, the first interface being configured for connecting the monitor device to the sensor assembiy. The method comprises the steps of determining a first vaiue of an eiectricai quantity of the primary sensor, determining a second vaiue of the eiectricai quantity of the secondary sensor, and determining an operating state of the ostomy appiiance based on at ieast the absoiute difference between the first vaiue and the second vaiue.

The method is performed in a monitor device of an ostomy system. In embodiments, the method comprises the initiai step of coupiing the monitor device to the sensor assembiy. In embodiments, the monitor device is connected by means of a mechanicai coupiing to terminais of the eiectrodes of the sensor assembiy, such as in a monitor interface of the sensor assembiy. In embodiments, the method comprises the initiai step of appiying the ostomy appiiance, such as a base piate or a sensor patch incorporating the sensor assembiy, to the (peristomai) skin surface of a user.

In embodiments, the method is repeated/reiterated during use, such as for the duration of the monitor device being coupied to the sensor assembiy. For exampie, the method may comprise repeatabiy determining the first and second vaiues and determining an operating stated based on at ieast the absoiute difference for each iteration of the method.

It is appreciated that functionaiities of the monitor device and ostomy system as disciosed herein in reiation to the first aspect of the invention are appiicabie to the method as disciosed herein in reiation to the second aspect of the invention, and vice versa. Further, definitions reiating to, and embodiments of, the monitor device and ostomy system are considered appiicabie to the method as disciosed herein. Thus, it is appreciated that disciosures of the monitor device as being configured to perform certain acts aiso appiy to the corresponding acts in the method of operating such monitor device and vice versa.

For exampie, in embodiments, the step of determining the operating state may comprise determining the operating state based on at ieast one of (i) the absoiute difference between the first vaiue and the second vaiue, (ii) on compiiance of the absoiute difference between the first vaiue and the second vaiue with a primary threshoid vaiue, (iii) a deviation of the first vaiue from a first initiai baseiine and/or a deviation of the second vaiue from a second initiai baseiine, (iv) a previous operating state and on a deviation of the second vaiue from the second initiai vaiue and (v) a time difference between a deviation of the first vaiue from the first initiai baseiine and a deviation of the second vaiue from the second initiai baseiine. In embodiments, the monitor device further comprises a second interface comprising a transceiver module connected to the processor and configured for connecting the monitor device to an accessory device of the ostomy system, and the method comprises the additional step of transmitting a primary signal indicative of the operating state to the accessory device.

Thus, in embodiments, the method comprises, in accordance with determining an operating state of the monitor device, transmitting a primary signal indicative of such operating state to an accessory device of the ostomy system. The accessory device may be a smart device, such as a smartphone, a smartwatch, a tablet, or it may be a server device. In embodiments, the primary signal is transmitted wirelessly, such as by means of the second interface as previously disclosed.

Thereby, the user may be notified of the determined operating state by means of his/her accessory device, such as in a graphical user interface of the accessory device.

In alternative embodiments, the method is performed in an accessory device connected, such as wirelessly connected, to the monitor device, such that the monitor device may relay raw data indicative of the first and second values to the accessory device, and such that the accessory device may perform the step of determining the operating state and associated steps of the method relating to the determination of the first and second base lines, time deviations, etc.

In a third aspect of the invention, a monitor device of an ostomy system comprising a sensor assembly is disclosed. The monitor device is configured to perform the steps of the method according to the second aspect of the invention. The ostomy system may be the ostomy system according to the first aspect of the invention.

Detailed description of the drawings

Fig. 1 illustrates an exemplary layout of electrodes 110 of a sensor assembly according to an embodiment of the invention. The sensor assembly forms part of an ostomy appliance, such as a base plate or a sensor patch, and comprises a stomal opening 101 with a center point 102. The stomal opening 101 may be defined by a support layer (not shown) of the sensor assembly support the electrodes 110. The sensor assembly comprises a first electrode 111, a second electrode 112 and a third electrode 113. The first electrode 111 is arranged at a first radial distance rl from the center point 102, the second electrode 112 is arranged at a second radial distance r2 from the center point 102, and the third electrode 113 is arranged at a third radial distance r3 from the center point 102. The second radial distance r2 is greater than the first radial distance rl; r2>rl, and the third radial distance r3 is greater than the second radial distance r2; r3>r2, such that rl<r2<r3. In the illustrated embodiment, the electrodes span an angle space of 90 degrees about the center point 102, but in alternative embodiments, they may span angle space of at least 180 degrees, such as at least 270 degrees, such as to provide even greater sensing coverage about the stomal opening 102. The electrodes 111,112,113 may, as illustrated, be arranged concentrically about the center point 102, such that their respective radial distances rl,r2,r3 are constant about the center point 102, and such that the mutual radial distances between the electrodes are constant.

By means of a monitor device (not shown) coupled to the sensor assembly, a voltage is applied across the first electrode 111 and the second electrode 112, thus forming a primary sensor SI. The primary sensor SI is, at least, capable of sensing changes in the environment between the first electrode 111 and the second electrode 112, such as the presence of a liquid or moisture causing a change in an electrical quantity, such as the electrical resistance, between said electrodes. Likewise, a voltage is applied across the first electrode 111 and the third electrode 113, thus forming a secondary sensor S2. The secondary sensor S2 is, at least, capable of sensing changes in the environment between the first electrode 111 and the third electrode 113, such as the presence of a liquid or moisture causing a change in an electrical quantity, such as the electrical resistance, between said electrodes.

Fig. 2A illustrates an exemplary situation of a liquid 99, emanating from the stomal opening 101, causing a bridge to form between the first electrode 111 and the second electrode 112 of the sensor assembly. Such bridge provides a path for the current, and thus causes the resistance between the first electrode 111 and the second electrode 112 to decrease, such as to form a short- circuit. Because the liquid does not bridge between the first electrode 111 and the third electrode 113, the resistance therebetween is essentially unaffected by the presence of the bridge between the first electrode 111 and the second electrode 112. Consequentially, the absolute difference between the resistance of the primary sensor SI and the resistance of the secondary sensor S2 increases, such as increases above a primary threshold value (e.g., for triggering a change in operating state). Thereby, the monitor device may determine that liquid has occurred in the vicinity of the primary sensor SI, but not in the (entire) vicinity of the secondary sensor S2: namely, since the secondary sensor S2 spans the primary sensor SI due to the arrangement of electrodes and configuration of the monitor device, a change in absolute difference between the first and second values must be due to liquids in the vicinity of the primary sensor SI only. Further, because the presence of liquid has been determined in the vicinity of the primary sensor SI, which is composed of electrodes 111,112 radially closer to the stomal opening 101 than the electrodes of the secondary sensor S2, the monitor device may determine that the liquid stems from features in such vicinity, which is most likely the stoma. Therefore, the monitor device may determine an operating state of the ostomy appliance, the operating state according to the present example being indicative of the presence of stomal output in the interface between the skin surface and the ostomy appliance. The monitor device may be configured to provide a signal and/or a warning to the user that attention is needed, as described herein.

Fig. 2B illustrates an evolving case of the exemplary situation in Fig. 2A. Here, the liquid 99 has propagated to reach the third electrode 113 such that the liquid further causes a short-circuit of the secondary sensor S2 comprising the first electrode 111 and the third electrode 113. Now, the monitor device may determine that liquid spans from the first 111 to the third electrode 113, such that said liquid has propagated from spanning the first 111 and the second electrode 112, forming the primary sensor SI, to now having reached the third electrode 113. Thereby, the monitor device may determine, given that it was previously determined, in relation to Fig. 2A, that the liquid is indeed stomal output (originating from the stomal opening), that the output is propagating further, and as such, the monitor device may determine a new operating state indicative of such propagation. Further, based on the mutual distance between the electrodes, in particular the radial distance between the second electrode 112 and the third electrode 113, given by r3-r2 due to the concentrical layout of electrodes, the monitor device may determine a speed of propagation based on a time difference between determining the operating state indicative of presence of output and the (new) operating state indicative of the propagation of output.

Fig. 3A illustrates a schematic graph of the electrical resistance R as a function of time t, R(t), for each of the primary sensor SI and the secondary sensor S2 (dashed) in an exemplary case. The primary sensor SI is formed by a voltage applied across the first electrode 111 and the second electrode 112, and the secondary sensor S2 is formed by a voltage applied across the first electrode 111 and the third electrode 113, as explained in relation to Fig. 1.

In the illustrated example, the resistance of the primary sensor SI has dropped from the value Rl_l to the value Rl_2 at time tO while the resistance R2_2 of the secondary sensor S2 has remained constant at the value R2_l, such that R2_1=R2_2 at time tO. Such situation may indicate that liquid has short-circuited (decreased resistance) the primary sensor SI, whereas the secondary sensor S2 remains unaffected by such liquid (i.e., "dry"). According to embodiments of the invention, the monitor device is configured to continuously (here, considered at time tO) determine a first value (here, Rl_2) of an electrical quantity (here, resistance) of the primary sensor SI and a second value (here, R2_2) of the (same) electrical quantity (hence, resistance) of the secondary sensor S2. Based on such determinations of the resistances of each of the two sensors S1,S2, the monitor device can determine the absolute difference in resistance |R2_2 - Rl_2| between the two sensors. In accordance with such absolute difference |R2_2 - Rl_2| being above a primary first threshold Tip (in Fig. 3A indicated for illustrative purposes as a range on the y-axis R), the monitor device is configured to determine that liquid is present in the interface between the skin surface and the ostomy appliance - and in particular in the vicinity of the primary sensor SI.

Namely, the drop in resistance of the primary sensor SI occurring before a similar drop in resistance of the secondary sensor S2 is indicative of liquid not having reached the third electrode 113 of the secondary sensor S2 at time tO, and as such, the liquid must originate from the stomal opening, which indicates that the liquid is indeed stomal output. Thereby, based on the difference of resistance between the two sensors S1,S2 alone, the monitor device may determine the presence of stomal output in the interface. As was explained in relation to Fig. 1, this analysis applies to the situation where the primary sensor SI is formed by a first electrode and a second electrode, the first electrode being arranged at a first radial distance from the stomal opening (e.g., center point thereof) and the second electrode being arranged at a second radial distance from the stomal opening (e.g., center point thereof), the second radial distance being greater than the first radial distance, and where the secondary sensor S2 is formed by the first electrode and a third electrode, the third electrode being arranged at a third radial distance from the stomal opening (e.g., center point thereof), the third radial distance being greater than the second radial distance.

Fig. 3B illustrates a schematic graph of the electrical resistance R as a function of time t, R(t), for each of the primary sensor SI and the secondary sensor S2 (dashed) in an evolved situation of the case in Fig. 3A. Here, at time tl, the secondary sensor S2 has experienced a similar drop in resistance as the primary sensor SI at time tO. Further, indicated is the first initial baseline R01 and the second initial baseline R02 (dashed-dotted, coinciding) representing the initial value of resistance of each of the two sensors S1,S2, such as the initial average values of the respective resistances as measured upon connection between the monitor device and the sensor assembly, such as within a first time period upon such connection. The first R01 and second initial baselines R01 represent the resistances of the respective sensors S1,S2 in a dry/clean situation.

At time tl, each of the first value Rl_3 and the second value R2_3 are below the respective first initial baseline R01 and the second initial baseline R02: Rl_3 < R01 and R2_3 < R02. This indicates that liquid has caused the resistance of the secondary sensor S2 to decrease similar to the resistance of the primary sensor SI. Since the previously determined operating state was indicative of the presence of output in the interface (discussed in relation to Fig. 3A), the monitor device may determine a new operating state, taking into account the previous operating state and the situation of Rl_3 < R01 and R2_3 < R02. Therefrom, the new operating state may be determined to be indicative of a propagation of the output in the interface. In embodiments, the time difference between the determination of the previous operating state indicative of presence of liquid in the vicinity of the primary sensor SI and the determination of the current operating state indicative of the propagation of the liquid may be used to determine the speed of propagation, and as such an urgency of the current operating state. For example, where the speed of propagation is high, such as above a threshold, the urgency may be considered high due to the risk of imminent leakage of output onto the user's clothes, whereas a low speed of propagation may give the user more time to take remedying actions.

Fig. 3C illustrates a schematic graph of the electrical resistance R as a function of time t, R(t), for each of the primary sensor SI and the secondary sensor S2 (dashed) in an exemplary case. In this case, at time tO, the absolute difference between the first resistance Rl_2 and the second resistance R2_2, |R2_2 - Rl_2|, is less than a first primary threshold value Tip. Further, the first resistance Rl_2 is below the first initial baseline R01 (dashed-dotted) of the primary sensor SI, and the second resistance R2_2 is below the second initial baseline R02 (dashed-dotted) of the secondary sensor S2. Based on at least the absolute difference, the monitor device may determine that the measurements are not indicative of stomal output in the interface. Further, based on the deviations of the first Rl_2 and second resistances R2_2 from the respective initial baselines R01,R02, the monitor device may determine that the measurements are indicative of moisture, such as sweat, absorbed by the adhesive layer of the ostomy appliance in contact with the primary sensor SI and the secondary sensor S2. Thus, the operating state may be determined to be an operating state indicative of the presence of moisture and/or sweat having formed uniformly in a radial direction from the stoma, thus giving rise to the substantially identical decrease of resistance by each of the two sensors S1,S2.

Fig. 4 illustrates a flow diagram of an exemplary method of determining an operating state of an ostomy appliance of an ostomy system as performed in a monitor device of the ostomy system. For illustrative purposes, the electrical quantity considered in the present method is resistance, but it is appreciated that other electrical quantities may be used upon selecting appropriate threshold values. Further, it should be noted that further parameters or values may be used in the determination of the various operating states, but the flow diagram intends to illustrate how such various operating states may be determined based on solely two sensors comprising three electrodes (see e.g., Figs. 3A-3C) and an application of voltage forming a primary sensor and a secondary sensor as previously disclosed. For illustrative purposes, the monitor device is configured to determine four different operating states O.S. using the references 1, 2, 3, and 4. In other embodiments, the monitor device may be configured to determine fewer operating states, such as at least two operating states. In embodiments, the monitor device may be configured to determine more than four operating states. The four operating states referred to herein are the first operating state 1 indicative of presence of stomal output in the interface by the primary sensor, the second operating state 2 indicative of a propagating stomal output in the interface, the third operating state 3 indicative of sweat in the interface/absorbed in an adhesive layer of the ostomy appliance, and the fourth operating state 4 indicative of no change from initial application of the ostomy appliance. Thus, the fourth operating state 4 may be considered a default operating state where no change has been detected since initial application.

The monitor device is initially configured to determine the resistance R1 (the first value as referred to previously) of the primary sensor and the resistance R2 (the second value as referred to previously) of the secondary sensor.

In step S101, the absolute difference AR=|R1-R2| between the two resistances is determined.

In step S102, if AR is greater than a primary threshold value Tip, the monitor device may determine that the operating state O.S. is the first operating state, O.S.=l (indicative of presence of stomal output by the primary sensor).

In step S103, if AR is less than the primary threshold value Tip, the monitor device may determine that the operating state O.S. is either the second, the third, or the fourth operating state; O.S.=2/3/4.

In step S104, if the first resistance R1 is substantially unchanged from its first initial baseline R01 and if the second resistance R2 is substantially unchanged from its second initial baseline R02, the monitor device may determine that the operating state O.S. is the fourth operating state; O.S.=4 (indicative of no change from initial application of the ostomy appliance.

In step S105, if the first resistance R1 is less than its first initial baseline R01 (such as if less than a threshold value indicative of a drop below the first initial baseline R01) and if the second resistance R2 is less than its second initial baseline R02 (such as if less than a threshold value indicative of a drop below the second initial baseline R02), the monitor device may determine that the operating state O.S. is either the second or the third operating state; O.S.=2/3.

In step 106, if the previous operating state O.S._p (such as determined in a previous iteration of the flow diagram) was determined not to be the first operating state; O.S._p¹l, the monitor device may determine that the operating state is the third operating state; O.S.=3 (indicative of sweat in the interface).

In step S107, if the previous operating state O.S._p (such as determined in a previous iteration of the flow diagram) was determined to be the first operating state; O.S._p=l, the monitor device may determine that the operating state is the second operating state; O.S.=2 (indicative of a propagation of stomal output, i.e., the presence of stomal output as determined according to the previous operating state O.S._p has propagated to the secondary sensor). In step S108 (dashed; optional), the monitor device may determine the time difference At between the monitor device determining that the operating state is the first operating state, O.S.=l, and the monitor device determining that the operating state is the second operating state, O.S.=2. Thus, such time difference At is indicative of the time between output having been determined to be present by the primary sensor and output having been determined to be present by the secondary sensor.

In step S109 (dashed; optional), the monitor device may determine the speed of propagation v, based on the time difference At as determined in step S108 and on a radial distance Ar between the second electrode and the third electrode: v=Ar/At. The distance Ar may be stored in a memory of the monitor device. The speed of propagation v may be indicative of an urgency of the second operating state O.S.=2. For example, the second operating state may comprise a plurality of secondary second operating states, such that, based on the speed of propagation, a certain operating state of the secondary second operating state indicative of the urgency may be selected. For example, a set of threshold values associated with the speed of propagation may determine the urgency, and as such the secondary second operating state.

In Fig. 4, the monitor device may be configured to transmit a primary signal indicative of any of the operating states 1/2/3/4, such as to transmit a primary signal to an accessory device comprising a visual interface configured to notify the user of the determined operating state.

Although particular features have been shown and described, it will be understood that they are not intended to limit the claimed invention, and it will be made obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the claimed invention. For example, it is envisioned that the sensor assembly and the electrodes thereof may be incorporated and/or provided in a variety of different embodiments without departing from the scope of the invention.

The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. The claimed invention is intended to cover all alternatives, modifications, and equivalents.