Patent Description:
A major requirement for effective wound care management is the need to monitor and change wound dressings to provide optimal conditions for tissue healing. Most known methods of wound monitoring and care require manual and/or subjective analysis of a range of parameters such as wound temperature and wound dressing saturation/age which usually involves disturbing the patient and/or removing the dressing for inspection. For example, it is recognized that wound temperature is a quantitative measurement that has the potential to assist in assessing and diagnosing chronic deep wound and surrounding skin infection. Indeed, studies have shown that incorporating quantitative skin temperature measurement into routine wound assessment provides a timely and reliable method for a clinician to quantify the heat associated with deep wound and surrounding skin infection (e.g. elevated local temperatures above <NUM> are an indication of wound infection) and to monitor ongoing wound status.

Similarly, it is known that, as healing occurs, the amount of exudate produced usually decreases. The volume of exudate is related to the surface area of the wound and large wounds often produce higher volumes of exudate. However, although a moist wound environment is necessary for optimal wound healing, over- or under-production of exudate may adversely affect healing. Any factor that increases capillary leakage or predisposes a patient to the development of tissue oedema (e.g. inflammation, bacterial contamination or limb dependency) may boost exudate production while low exudate production may indicate a systemic problem (e.g. dehydration, hypovolemic shock and microangiopathy) or may be a feature of ischaemic ulcers. Accordingly, it is essential to accurately determine and evaluate the factors contributing to the production of too much or too little exudate.

However, currently, measurement and assessment of the aforementioned and other wound parameters are generally performed manually using subjective visual inspections and/or equipment such as thermometers or moisture meters resulting in suboptimal dressing changing frequency, clinical timewasting, patient discomfort, increased dressing cost and increased wound healing time.

Accordingly, various attempts have been made to develop smart dressings in which sensors such as a moisture sensor and an associated electronic module communicable with a clinician have been incorporated into the dressings. However, the placement of the sensor and module, as well as the construction of the dressing itself, can negatively impact on the performance of the smart dressing. More particularly, diffusion of wound exudate in a typical dressing takes place initially by vertical diffusion from a wound, through the dressing layers as far as a super-absorbent fibre (SAF) layer where fast lateral diffusion then takes place and the surface of this layer, which is generally in contact with the (moisture) sensor, gets rapidly wet. As a result, moisture is wicked across the dressing very rapidly into contact with the (moisture) sensor which is then activated (i.e. shows a sudden and significant change in measurand) and saturates earlier than desired for wound monitoring purposes i.e. before <NUM>% of the dressing capacity is reached. As a result, it is not possible to measure or map the progress of the wound exudate through the dressing. The measurand can be, for example resistance, impedance, capacitance and/or optical properties.

It has also been found that dressing performance can be compromised by the presence of the electronic module and associated sensor in the dressing e.g. typically electronic modules are placed over the absorbent layers giving rise to pressure being generated by the electronic module on the absorbent layers in the dressing which can change the diffusion/wicking properties of the dressing so that the dressing does not perform as originally intended. Importantly, the placement of the electronic modules over the absorbent layers can also severely compromise the breathability of the dressings which is highly undesirable resulting in negative consequences for the healing process.

<CIT> describes a dressing system for a wound comprising various sensors and an absorbent pad. However, the sensor(s) of the dressing system are not moisture sensors adapted to measure the progress of wound exudate across the dressing. Similarly, <CIT> describes a dressing having a matrix of temperature sensors unsuitable for mapping wound exudate in the dressing, while <CIT> describes a separate sensing device for attachment to a dressing in which the non-integral external sensing device has a plurality of separate moisture sensors which are arranged in such a way that progress of exudate across the dressing cannot be mapped. <CIT> relates to a negative pressure wound dressing having a sealed, negative pressure device intended for drawing wound fluids into a vacuum reservoir. <CIT> discloses a reduced pressure wound dressing with saturation sensors that generate a signal based on exposure to liquid. <CIT>,relates to stimulus responsive substrates and uses of the substrates but fails to disclose a configuration of moisture sensors.

It is therefore an object to provide an improved dressing system to overcome at least one of the above mentioned problems.

According to a first aspect of the invention there is provided a dressing system for a wound comprising:.

Preferably, the peripheral sensor is located beyond the periphery of the absorbent pad.

Preferably, the dressing system further comprises a diffusion barrier to delay diffusion of wound exudate towards the sensor.

Preferably, the diffusion barrier comprises a delay channel defined in the absorbent pad.

Preferably, the absorbent pad comprises a first superabsorbent layer and the diffusion barrier comprises a second superabsorbent layer between the sensor and the first superabsorbent layer, and wherein the first and second superabsorbent layers comprise superabsorbent fibre layers.

Preferably, the moisture sensors of the moisture sensor array are radially offset with respect to the centre of the absorbent pad, to delay activation of the moisture sensors by diffusing exudate until after about <NUM>% of the dressing system capacity is reached.

Preferably, exudate progress across the dressing is measurable to provide a time-dependent indication of saturation levels of the dressing.

Preferably, the sensor further comprises one of: a pH sensor, a pressure sensor, a bacterial sensor, a temperature sensor, and an inertial sensor.

Preferably, the electronic module is offset with respect to the absorbent pad.

Preferably, the electronic module is located towards a periphery of the absorbent pad.

Preferably, the electronic module is located beyond the periphery of the absorbent pad.

Preferably, the electronic module is located beyond the periphery of the absorbent pad on a substrate.

Preferably, the electronic module comprises a communications module for communicating the wound data from the electronic module to a clinician, and wherein the communications module comprises a wireless communications module, and wherein the electronic module further comprises a power source for powering the electronic module.

Preferably, the dressing system further comprises a backing film on the absorbent pad.

The invention therefore results in a smart or intelligent wound dressing for the intelligent monitoring of wound health and dressing condition having integral moisture sensors adapted to map the progress of exudate in the dressing - i.e. the moisture sensors form part of the dressing (in particular the absorbent pad) or are located internally within the dressing The radially offset position of the (moisture) sensors can delay activation of the sensors by diffusing exudate until after about <NUM>% of the dressing capacity is reached. In addition, by locating an array of the (moisture) sensors in a radial manner i.e. both centrally and offset from the centre of the absorbent towards the periphery of the dressing, exudate progress across the dressing can be measured or mapped to give a time-dependent indication of the saturation levels of the dressing.

Moreover, offset positioning of the electronic module ensures that dressing performance is not compromised by the presence of the electronic module. In particular, the offset electronic module does not impede or impinge upon exudate diffusion in the dressing. Although the Applicant does not wish to be bound by any theorem, it is believed that additional pressure created by centrally positioned electronic modules on the absorbent foam in previous dressings can alter the diffusive/wicking properties of the absorbent pad so that the dressing does not perform as intended. The offset position of the electronic module of the present invention eliminates any such additional pressures in the dressing and improves breathability.

The dressing of the invention is a laminated or multi-layer dressing adapted to rapidly absorb exudates and interstitial fluids and optimize conditions for healing at the wound-dressing interface. A primary wicking or absorbent pad provides a rapid capillary action response to quickly distribute absorbed exudate throughout the dressing and create a sustained movement of fluid away from wound beds.

The dressing of the invention facilitates the monitoring of individual and multiple sensor readings of a wound in real-time and/or the provision of time specific updates. The data generated from the dressing provides a constant and/or time specific update to an app and/or software available to a clinician. Each sensor reading provides a specific reading that is easily interpreted for ease of use and understanding.

In addition to the moisture sensors, pH sensors can be employed in the dressing system to facilitate the measurement of exudate pH to reflect the condition of a wound bed and aid in monitoring and determining the wound's response to treatment. Pressure sensors can also be employed to provide clinicians with key evidence describing pressure applied on wounds during critical healing stages. Temperature sensors can also be employed to monitor healing. Similarly, bacterial sensors can be used to assist in detecting infection. Inertial sensors can be adapted to monitor patient orientation, motion and/or activity.

The dressing of the invention provides a sealing arrangement preventing any bodily fluids or other material that may cause infection and/or impact sensor readings from reaching a wound. The waterproof sealing arrangement also enables the patient to wash and shower without damaging or obstructing the dressing. This is particularly beneficial when the dressing is employed on long term wounds.

Data generated from the dressing is used for the prediction of wound healing to help clinicians adopt a more specific management strategy, at the right time, to achieve healing. The use of the sensed parameters (e.g. moisture, pH and temperature) in combination provides essential information that improves future patient care.

Data transferred to a downloaded app on a handheld device can be used to provide clinicians with continuous data for monitoring and analysing wounds with the app enabling real-time bi-directional communication between patient and clinician.

<FIG> show a typical multi-layered intelligent wound dressing system for monitoring and treating a wound generally indicated by the reference numeral <NUM> and made up of a wicking absorbent foam pad <NUM> for absorbing wound exudate <NUM> having an intermediate non-absorbent layer <NUM> thereon and also an upper super-absorbent fibre (SAF) layer <NUM>. The dressing system <NUM> also has an adhesive backing film <NUM> attached to the SAF layer <NUM> defining a peripheral adhesive side border <NUM> for adhering the dressing <NUM> to a patient. The absorbent pad <NUM> is provided with a silicon adhesive <NUM> for assisting in adhesion and a removable release film <NUM> on the absorbent pad <NUM> and the backing film <NUM> for protecting the dressing <NUM> prior to use.

The absorbent pad <NUM> is substantially square in shape and is made up of a substantially square lower wound face <NUM> for contacting a wound having four side walls <NUM>,<NUM>,<NUM>,<NUM> upstanding therefrom and an upper face <NUM> disposed towards the non-absorbent layer <NUM> and the SAF layer <NUM>.

The dressing system <NUM> has a (moisture) sensor <NUM> centrally positioned with respect to the sidewalls <NUM>,<NUM>,<NUM>,<NUM> on top of the absorbent foam pad <NUM> and under the backing film <NUM> at the SAF layer <NUM>. Accordingly, in practice, the centrally positioned moisture sensor <NUM> of the dressing system <NUM> is located directly above the exudate <NUM> source i.e. the wound. The dressing system <NUM> can also have additional moisture sensors <NUM> as required.

The dressing system <NUM> of <FIG> is further provided with an electronic module <NUM> for harvesting and communicating data from the moisture sensor <NUM>.

As shown in <FIG>, in use, diffusion of wound exudate <NUM> takes place initially by vertical diffusion from a wound, through the absorbent foam pad <NUM>, the non-absorbent layer <NUM> and the SAF layer <NUM>. At the SAF layer <NUM>, fast lateral diffusion then takes place so that the surface of the SAF layer <NUM>, which is in direct contact with the moisture sensor <NUM> becomes rapidly wet.

The fast lateral diffusion wicks moisture across the dressing system <NUM> very rapidly, and into contact with the moisture sensors which <NUM> which are then activated (i.e. show a sudden and significant drop in resistance where resistance moisture sensors <NUM> are employed) and saturate earlier than desired i.e. well before about <NUM>% of the dressing capacity is reached. Alternatively any other type of sensor can be used that shows a change in measurand upon contact with or proximity to exudate.

<FIG> shows a top plan view of a first embodiment of a multi-layered intelligent wound dressing system <NUM> of the invention for monitoring and treating a wound similar to the dressing system <NUM> of <FIG> and like numerals indicate like parts. However, the intelligent wound dressing system <NUM> of the invention is provided with an array of moisture sensors in the form of a plurality of moisture sensors <NUM> namely four integral moisture sensors <NUM> formed as part of the dressing system <NUM> positionally offset on and with respect to the centre of the absorbent pad <NUM> so that activation of the sensors <NUM> via the vertical and lateral diffusion of exudate <NUM> is delayed until after about <NUM>% of the dressing capacity is reached - i.e. radial positional offsetting of the moisture sensors <NUM> causes a delay in diffusion of exudate <NUM> to the moisture sensors <NUM> so that travel of wound exudate <NUM> can be mapped and/or measured. More particularly, in the present embodiment, the four moisture sensors <NUM> are located towards the periphery of the intelligent dressing <NUM> e.g. towards the sidewalls <NUM>,<NUM>,<NUM>,<NUM> of the absorbent pad <NUM>. More particularly, in the present embodiment, the four peripheral sensors <NUM> of the array are located in the four corners of the square absorbent pad <NUM>.

<FIG> shows a top plan view of a second embodiment of a multi-layered intelligent wound dressing system <NUM> of the invention similar to the dressing system of <FIG> in which a single moisture sensor <NUM> is offset with respect to the centre of the absorbent pad <NUM> towards the periphery of the dressing <NUM>. Like numerals indicate like parts.

More particularly, in the present embodiment, the moisture sensor <NUM> is located at the corner of the absorbent pad <NUM> defined between the sidewalls <NUM>,<NUM>. However, the dressing system <NUM> is further provided with a diffusion/wicking barrier <NUM> to delay diffusion of exudate <NUM> towards the moisture sensor <NUM> to in turn to delay activation of the moisture sensor <NUM>. In the present embodiment, the diffusion barrier <NUM> is a delay line or channel <NUM> defined in and across the absorbent foam pad <NUM> including the non-absorbent layer <NUM> and the SAF layer <NUM> adjacent the moisture sensor <NUM>. The delay channel <NUM> is cut into absorbent foam pad <NUM>, the non-absorbent layer <NUM> and the SAF layer <NUM> to partially diffusively isolate the moisture sensor <NUM> from the absorbent pad <NUM> (and hence the exudate <NUM>) so that diffusion of exudate <NUM> to the moisture sensor <NUM> is delayed until after about <NUM>% of the dressing capacity is reached. As the moisture sensor <NUM> is only partially diffusively isolated by the delay channel <NUM>, the delay channel <NUM> extends only partially across the absorbent pad <NUM>, the non-absorbent layer <NUM> and the SAF layer <NUM> so that the moisture sensor <NUM> remains diffusively communicable with exudate <NUM> in use.

<FIG> shows a cross-sectional view through a third embodiment of a multi-layered intelligent wound dressing system <NUM> of the invention similar to the dressing system <NUM> of <FIG> but in which two moisture sensors <NUM> are offset with respect to the absorbent pad <NUM> on a diffusion barrier <NUM> in the form of a secondary superabsorbent (SAF) layer <NUM> i.e. a second superabsorbent layer <NUM> between the moisture sensors <NUM> and the first SAF layer <NUM>. More particularly, the two moisture sensors <NUM> are offset with respect to the centre of the absorbent pad <NUM> towards the periphery of the dressing <NUM> on the secondary SAF layer <NUM> which is located between the (primary) SAF layer <NUM> and the backing film <NUM>. The secondary SAF layer <NUM> is sized and dimensioned to delay exudate <NUM> diffusion so that sensor <NUM> activation is delayed until after about <NUM>% of the dressing capacity is reached.

<FIG> shows a top plan view of a variant of the intelligent wound dressing system <NUM> of <FIG> with a radial spacing of moisture sensors <NUM> and like numerals indicate like parts. However, in the present embodiment, the electronic module <NUM> is also offset with respect to the centre of the absorbent pad <NUM> on a laminar substrate <NUM> to preserve and enhance the performance of the intelligent dressing <NUM>. More particularly, in the present embodiment, the electronic module <NUM> is located to the left of the side wall <NUM> of the absorbent pad <NUM> on the substrate <NUM>. The electronic module substrate <NUM> is accommodated in the multi-layer dressing system <NUM> and supports the electronic module <NUM> in the dressing system <NUM> fully offset from absorbent pad <NUM> so that the electronic module <NUM> does not overlie or overlay the absorbent pad <NUM>. Accordingly, the electronic module <NUM> in the dressing system <NUM> does not impact, negatively or otherwise, on exudate <NUM> diffusion in the dressing system <NUM>.

As shown in the drawing, in the present embodiment, the dressing system <NUM> is provided with radially offset peripheral moisture sensors <NUM> as previously described disposed towards the periphery of the dressing system <NUM>. The offset moisture sensors <NUM> are positioned adjacent the corners of the side walls <NUM>,<NUM>,<NUM>,<NUM> of the absorbent pad <NUM> on peripheral tabs <NUM> connected to the absorbent pad <NUM>. However, additionally, the dressing system <NUM> is provided with a further array <NUM> of moisture sensors <NUM>. The moisture sensors <NUM> of the array <NUM> are radially offset from and/or spaced apart across the centre of the absorbent pad <NUM> between the side walls <NUM>,<NUM> towards the periphery of the dressing system <NUM> so that exudate <NUM> diffusion rates across the dressing system <NUM> can be measured by the array <NUM> of sensors <NUM>.

The electronic module <NUM> on the substrate <NUM> can include a processor for processing data from the sensors <NUM>, memory for storing data and programmes, a communications module <NUM> (e.g. a BLE, NFC, WiFi (Trade Mark) or narrowband IoT based communications module) for communicating the sensor data to a base station attended by a clinician, batteries <NUM> and an actuator for controlling actuation of the dressing system <NUM>. The module can be made up of several sections electrically linked as appropriate. Other components can use an inertial sensor for patient activity monitoring, voltage regulators, switches, LED indicators etc. As shown in the drawing, all the aforementioned components can be accommodated on the electronic module substrate <NUM> in a fully offset position without overlying the absorbent pad <NUM>.

<FIG> shows a graph of sensor performance of the moisture sensors in the intelligent dressings of <FIG> showing the improved performance of the offset moisture sensors of the intelligent dressing systems <NUM> of <FIG> when compared with that of the non-offset moisture sensor of the dressing system of <FIG>. The dressing systems <NUM> shown in <FIG> were sized so that the dressing capacity was about <NUM> i.e. the moisture sensors <NUM> were activated at about <NUM> (<NUM>% of the dressing capacity). As shown in the graph, a progressive shift in sensor activation (a drop in resistance) occurred for the intelligent dressing systems <NUM> of <FIG>. Accordingly, by offsetting the moisture sensors away from the centre of the absorbent pad <NUM>, both with and without the diffusion barrier <NUM> and the secondary SAF layer <NUM> the desired dressing saturation target was achieved.

<FIG> shows a graph of exudate threshold volume in the intelligent dressing system <NUM> of <FIG> according to the radial moisture sensor <NUM> spacing in the dressing system <NUM>. More particularly, the graph illustrates the threshold volume (i.e. the amount of exudate required to activate the moisture sensors <NUM>) as a function of sensor <NUM> distance from the centre of the dressing system <NUM>. As shown in the graph, sensors <NUM> placed at or near the dressing centre activated early while those towards the periphery of the dressing system remained inactive until more exudate <NUM> was absorbed by the dressing system <NUM>. Accordingly, wound exudation rates could be assessed, the diffusion of exudate across the dressing measured, and predictions made regarding the time at which the dressing would become fully saturated and require changing.

The absorbent pad <NUM> is formed from a die-cut adhesive bandage material which allows for sufficient transfer of oxygen to a wound site while effectively preventing passage of microbes to the wound. The backing film <NUM> can be formed from a polymer such as acrylic or polyurethane while the release film <NUM> can be formed from polyethylene terephthalate (PET).

The electronic module <NUM> of the dressing system of the invention includes a communications module such as a wireless communications module for communicating wound data from the electronic module to a clinician and a power source such as a battery for powering the electronic module.

The dressing system <NUM> can be manufactured in any suitable size as required in accordance with wound sizes. Typical dressing sizes are <NUM> x <NUM>, <NUM> x <NUM>, <NUM> x <NUM> and <NUM> x <NUM>.

The dressing system <NUM> is sterilised to kill microorganisms transferred during the manufacturing process. A suitable sterilization method is an ethylene oxide (EtO) sterilisation method which protects the sensors <NUM> and electronic module <NUM> from damage. This method of sterilisation is also preferred due to its handling ease, versatility and suitability for use with delicate medical dressings which could be damaged by other sterilisation methods such as heat sterilisation.

In use, data from the sensors <NUM> is harvested and processed for optimal wound monitoring and healing. Other sensor types can be employed in the dressing system <NUM> in addition to the moisture sensors <NUM> as required e.g. pressure sensors, bacterial sensors, temperature sensors and pH sensors. The sensors <NUM> can be offset from the centre of the absorbent pad <NUM> as hereinbefore described and can also be included in the offset electronic module <NUM> if desired. Various data processing methods can be employed as necessary.

Claim 1:
A dressing system (<NUM>) for a wound comprising:
an absorbent pad (<NUM>);
at least one sensor (<NUM>) for detecting wound data, and
an electronic module (<NUM>) communicable with the sensor, characterised in that:
the sensor (<NUM>) comprises a moisture sensor array (<NUM>) provided on or in the absorbent pad (<NUM>) adapted to map the progress of exudate (<NUM>) in the absorbent pad (<NUM>), and wherein the moisture sensor array comprises a plurality of moisture sensors (<NUM>) radially offset with respect to the centre of the absorbent pad (<NUM>) including a peripheral moisture sensor (<NUM>) located towards a periphery of the absorbent pad.