"FOOTWEAR FOR PREVENTION OF FOOT ULCERATION"

FIELD OF INVENTION

The invention relates to a temperature monitoring system. In particular, although not exclusively, to a temperature monitoring system that is capable of measuring and monitoring the temperature of an individual's feet.

BACKGROUND TO THE INVENTION

It known that diabetic patients can have a tendency to suffer from a condition known as diabetic preliminary neuropathy. People with this condition generally suffer from a lack of feeling in their lower limbs. As a result of the lack of feeling, the individual will receive no feedback from the feet for example, when pressure is being exerted on their feet. This can result in inflammation of the skin tissue and if left untreated can result in ulceration that if left untreated, could lead to infection and other potential complications. Inflammation due to local injury is typically determined by one or more of the following: Rubor (redness), Calor (heat), Tumor (swelling), and Dolor (pain). A person with diabetic pulmonary neuropathy cannot sense dolor, calor or tumor and sometimes cannot see rubor.

US patent 6,195,921 to Vincent Hoa Gia Truong discloses a virtual intelligence shoe with a podiatric analysis system. Sensors, such as pressure sensors, are permanently integrated into a shoe that includes an electronics module used to scan each of the sensors and to obtain specific sensor data that is stored for analysis. The data is not analysed in situ as such is not capable of providing or reporting any warnings of any potential issues relating to the user's feet. If left unattended, the user's feet can ultimately be caused to ulcerate. US patent 6,767,330 to Salix Medical Incorporation discloses a platform assembly on which a patient stands. The platform incorporates a number of sensors used to determine the temperature of the user's skin on the bottom of a person's foot. The device provides vital health information for diabetics in particular as it enables the temperature of areas of the foot to be measured and the data collected can be compared with previously recorded results. If the detected temperature exceeds a pre-defined level an audible signal or visual message can be generated to indicate that the user need medical intervention. This device is a static device and as such is not portable. Furthermore, the system is not capable of monitoring an individual's foot temperature while they undergo normal everyday activity.

US patent 5,642,096 to Paromed Medizintechnik GmbH discloses a device that can be incorporated in an article of footwear and includes a sensor disposed in a liquid mass of

hydrocell that is carried in the inner sole of a shoe. The sensor is capable of detecting both pressure and temperature of the patient's feet. The sensor is interfaced to an electrical circuit that can be used to provide an early warning of conditions that may lead to ulceration in a diabetic patient. This document does not disclose a temperature comparison mechanism to detect and measure the temperature of both of the user's feet within each shoe and comparing the data to determine any increase or variations between each foot.

Incipient ulceration can be detected by an increase local difference in temperature. However, one problem that needs to be overcome is the ability to distinguish between temperature differentials caused by time of day, footwear, environmental conditions and exercise and those that are caused by incipient ulceration.

In this specification if reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing features of the invention. Unless it is specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art or form part of the common general knowledge in the art.

It is an object of the present invention to provide an improved temperature sensing or at least alternative system for insertion into or which is incorporated in an item of footwear, related characteristics in at

SUMMARY OF THE INTENTION

In a first aspect the invention may broadly be said to consist in a temperature sensing device for an item of footwear comprising: a flexible insert capable of being inserted into said item of footwear, at least one temperature sensing element integral with said flexible insert and capable of sensing a user's temperature data in an analogue format, a flexible circuit electrically connected to said at least one temperature sensing element, an electronic sensing device adapted to be electrically connected to said flexible circuit and receiving as an input said user's temperature data, said electronic sensing device including; a data store, a controller, said controller adapted to perform a number of processing steps including: converting said received user's temperature data into a readable digital data format indicative of a user's foot temperature data, applying at least one algorithm to said user's foot temperature data

to detect and compare said received user's foot temperature with acquired foot temperatuie data relating to temperature of the user's other foot, to detect a difference over a period of time, storing said received user's foot temperature data in a data store, activating an alarm when said received user's foot temperature exceeds said expected user's foot temperature over a period of time, and a communication system for communicating said user's foot temperature stored in said data store to a separate module for storage and visual display and analysis and/ or for outputting by said separate module an audible or visual alarm to alert a user of a potential adverse health problem. Preferably, said flexible insert is integral with said item of footwear.

Preferably, a plurality of temperature sensing elements are integral with said flexible insert to form at least one temperature sensing region.

Alternatively, said temperature sensing elements are attached to one or more regions of a user's foot. Alternatively, said temperature sensing elements are attached to a region on an individual's body.

Preferably, said temperature sensing region is located in close proximity to a user's foot plantar surface.

Preferably, each of said temperature sensing elements is a resistive temperature sensing device.

Preferably, said temperature sensing device is a chip thermistor.

Preferably, said flexible circuit is formed from a copper foil displaced on one or more regions of said flexible insert.

Preferably, said temperature sensing elements are each electrically connected to said flexible circuit.

Alternatively, said temperature sensing elements are arranged in a grid configuration wherein each of said temperature sensing elements forms a node of said grid.

Alternatively, said temperature sensing elements are magnetically coupled to said controller. Alternatively, said temperature sensing elements are interfaced to said controller via a wireless connection.

Preferably, said wireless connection is a radio connection.

Preferably, said flexible insert includes a calibration element to provide calibration data as an input to said electronic sensing device.

Preferably, said flexible insert includes a load sensor to sense a force being applied by an individual's foot within said item of footwear.

Preferably, said item of footwear is selectable from the list including shoes, sandals, boots, socks or hosiery. Preferably, said temperature sensing element is woven into a fabric item such as a sock or other material used to form an inner sole for a shoe.

Preferably, said temperature sensing elements are embedded in mylar.

Preferably, said flexible insert is integral with an item of footwear.

Alternatively, said flexible insert is retrofit to an item of footwear. Preferably, said electronic sensing device is powered by batteries within said electronic sensing device.

Alternatively, said electronic sensing device is powered by an energy conversion mechanism used to convert a user's footfall into a useable energy source.

The invention may also be broadly be said to consist in a temperature sensing system comprising: temperature sensor units integral with, or capable of insertion into, one into each of a pair of items of footwear and each comprising at least one temperature sensing element for acquiring user foot temperature data, a module arranged to communicate wirelessly with one or both of the temperature sensor units and to either output an audible or visual alarm in the event of a difference beyond a threshold in temperature sensed by the temperature sensor units, to alert a user of a potential adverse health problem, and/or to store for subsequent downloading or to transmit user foot temperature data or temperature difference data in temperature sensed by the temperature sensor units, and either in said module or in or associated with one or both of said temperature sensor units, a processor arranged to receive and compare user temperature data from the temperature sensing element(s) to detect a difference beyond a threshold in temperature sensed by the temperature sensor units.

In a second aspect the invention may broadly be said to consist in a method comprising of preventing foot ulceration comprising acquiring user foot temperature data from each foot of a subject via temperature sensor units one in each of a pair of items of footwear worn by the subject, and comparing the foot temperature data relating to each foot for a difference beyond a threshold in temperature of each foot indicative of increased risk of foot ulceration..

The term "comprising" as used in this specification including claims means "consisting at least in part of, and in interpreting statements which include that term, the features prefaced by that term in each statement all need to be present but other features can also be present.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred form of the invention is described by way of example only and with reference to the accompanying drawings, which:

Figure 1 is a block diagram of the temperature sensing system of the invention.

Figure 2 is a diagram of one electrical configuration of the temperature sensing system of Figure 1.

Figure 3 is a block diagram of the electronic sensing device interfaced to the temperature sensing system of Figure 1.

Figute 4 is a block diagram of the sensing electronics incorporated in the electronic sensing device of Figure 3. Figure 5 is a flow chart showing a number of processing step undertaken by the electronic sensing device of Figure 3 and 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The invention in the preferred form relates to a system and method of making continuous measurements the temperature of the plantar regions of an individual's foot and in particular to a diabetic patient's foot. Temperature sensing elements 4 are incorporated within both the left and right footwear and a detected temperature comparison is made between each foot to determine any local difference between each foot. This difference is used to determine the likelihood of ulceration and alert the patient of the need to seek further professional advice.

Shoe Sole Insert

The conventional construction of a shoe incorporates an upper or body of the shoe, that is secured to the sole using glue, stitching, moulding or other means known in the art. An inner sole (or insole) is placed on top of the sole within the shoe on which inner sole the wearer's foot will press when the shoe is worn on the inner sole and be retained within the shoe by the upper or body of the shoe.

Temperature sensing units 1 herein often referred to as flexible inserts are incorporated within an individual's footwear such as shoes, sandals or boots, enabling the temperature of each users foot to be monitored when an individual is pursuing every day activities. This enables the likelihood of inflammation of one or both feet to be determined and an analysis of the detected

temperature measurements to be undertaken to determine the risk of foot ulceration. The temperature sensing units 1 may comprise integral parts of the insoles of the footwear, or maybe incorporated into the upper part of the sole pieces of the footwear, of footwear not comprising separate insoles as original equipment at the time of manufacture of the footwear. Alternatively the temperature sensing units 1 may comprise replacement insoles sold separately which can be retro-fitted into existing footwear, or further may comprise flexible pieces or inserts which are shorter than insoles and which are intended to be fitted into existing footwear below the existing (or replacement) insoles thereof. Further the temperature sensing units may be integrally incorporated into the sole parts of specialist socks or other items of hosiery. In a preferred form a thin flexible shoe sole insert, innersole or a podiatric innersole 2 shown in Figure 1 is provided, incorporated into a shoe during manufacture, or alternatively which can retrofit into an existing shoe. The insert 2 incorporates one or more temperature sensitive elements 4 that are arranged over one or more areas 7 of the innersole to provide temperature sensing zones 3. It is preferable that the temperature sensitive elements 4 are located in. close proximity to the plantar surface of an individual's foot such that there is a thermal conductive path between the temperature sensitive elements 4 and the individual's foot. The arrangement of temperature sensitive zones 3 is selected in order to provide optimum coverage of those areas of the individual's foot that tend to be most susceptible to ulceration. The flexible shoe insert 2 may be constructed from mylar or other suitable flexible material known in the art, and have the temperature sensing elements 4 embedded within the mylar material. The temperature sensing elements 4 are electrically connected using a ribbon cable 5 for example, to a lightweight electronic sensing device 6 that may be clipped on to the individual's shoe. Furthermore, the flexible shoe insert 2 may also incorporate a calibration element (not shown) that is interfaced to a microprocessor 8 within the electronics sensing device 6 . The calibration element can then be used to calibrate the temperature sensing elements 4 and eliminate manufacturing variations when determining the actual temperature. It is preferable that the flexible shoe inserts 2 are symmetrical about an imaginary central axis such that the shoe inserts 2 are reversible enabling interchanged for the left and right foot

Temperature sensing elements 4

In the preferred form, the temperature sensing elements 4 are thin flexible elements that may be constructed from a resistive temperature sensing device such as chip thermistors that are thermally bonded to regions of copper foil on one or more regions of the flexible shoe insert. The copper foil provides thermal conductivity between the measurement zone on the plantar surface of the individual's foot and the thermistors 4. ^" Whilst it is preferable to use chip

_ γ — thermistors 4 on copper foil, other constructions and means for measuring temperature over a region may also be used.

One terminal 11 of each of the temperature sensing elements 4 is connected to a common ground plane 9 as shown in figure 2 provided by the electronic sensing device 6 via an electrical conducting means such as a flexible circuit 10, conductive ink or conductive threads. The second terminal 12 of the temperature sensing elements 4 is connected to the electronic sensing device 6 via a second electrical conducting means such a flexible circuit 10, conductive ink or conductive threads.

In an alternative form, the temperature sensing elements 4 may be connected together to form a grid arrangement 13 as referred to in Figures 3 and 4. In this configuration the temperature sensing elements have one of their terminals 11 electrically connected to one of a number of vertical conductive threads for example and the second terminal 12 electrically connected to one of a number of horizontal conductive threads. This configuration of temperature sensing element array 13 arrangement enables more temperature sensing elements 4 to be incorporated into the inner sole 2 without the need to significantly alter the number of electrical connections to the electronic sensing device 6. In yet a further alternative form, the temperature sensing elements 4 may be powered and interfaced to the electronic sensing device processor 8 using magnetic coupling and/ or via radio frequency transmission.

Electronic Sensing Device

With reference to Figure 4, the electronic sensing device 6 in includes a number of circuit elements used to measure process the analogue temperature sensed by the temperature sensing elements 4 within an individual's shoe. A microprocessor 8 is programmed to control an analogue multiplexer 14 that is connected to a voltage supply source 15 and a sense resistor 16 which is in turn electrically connected to at least one thermistor 4. Hence, the selected thermistor 4 and sense resistor 16 form a voltage divider chain.

The temperature signal from any thermistor 4, each located in a specific area of the individual's foot, provides is an analogue voltage signal representative of temperature, and is input to the electronic sensing device 6. The induced voltage signal across the sense resistor 16 is converted into a digital data signal by analogue to digital converter 17 for processing by the microprocessor 8. The digital data signal is sampled by the microprocessor 8 and compared to a data table stored in a data store or memory 18 within the microprocessor 8 to convert the received induced voltage into an output that is representative of the temperature of the area of the individual's foot sensed by the thermistor 4. It is preferable that an electronic sensing device 6 is interfaced to one or both of the flexible shoe inserts 2. Therefore, in order to compare the

temperature sensed by the temperature sensing elements 4 within each flexible shoe insert 2, each electronics sensing device 6 also incorporates a wireless transceiver 19 to enable data to be transmitted from electronic sensing device 6 for processing as required.

Individual thermistor differences caused by manufacturing variations can be corrected using a table of reference correction factors stored in the microprocessor data store 18.

Alternatively, a calibration element can be integrated into the inner sole sensing surface the output of which can be used to adjust the detected thermistor outputs if required.

Additional circuit elements can be incorporated into the flexible inner sole 2 to provide other specific information such as the force being applied to one or more areas of an individual's foot to further aid foot problem diagnosis. To measure force, capacitive force measurement devices 20 as shown in Figure 2 can be incorporated into the inner sole 2 alongside the temperature sensing elements 4. Other force measuring devices known in the art may alternatively be incorporated into the inner sole 2.

The electronic sensing device 6 is controlled by the microprocessor 8 within the device 6 which is programmed to operate in at least two modes 8 power saving sleep mode and active mode. The microprocessor 8 is programmable to 'wake up' the electronic sensing device 6 from a sleep mode to an active mode at specific time intervals. Once the electronic sensing device 6 is in the active mode, the temperature of various areas under an individual's foot can be detected and measured by the microprocessor 8. The detected temperature values for each thermistor 4 are filtered by the processor 8 to remove self learned activity such as 8 temperature change due to the individual walking, standing on the forefoot for a length of time which will create a change in vascular flow that would result in localised temperature increases that are not indicative of potential inflammatory conditions, time of day based variations due to external temperature induced changes in vascular flow, and transitory temperature differences due to changes in thermal conductivity between the individual's foot and the temperature sensing elements 4.

Once the detected temperature values are filtered the detected temperature data is transmitted from the electronic sensing device 6 to a separate data processing module, incorporated in a wrist watch module or module adapted to be clipped to the user's clothing or a belt for example, or a key fob for example via the wireless transceiver 19. Once the detected temperature data has been transmitted the one or two electronic sensing devices 6 revert to a 'sleep mode' to minimize power consumption until the next programmed active measurement period. The microprocessor may be programmed such that the period of the 'sleep' mode may be adjusted or suspended based on the likelihood of inflammation activity detected by the microprocessor 8.

Differences in detected temperature between the left and right foot may be caused by patient specific circulatory problems for example. These physiological variations, which are a static bias between the sampled temperatures from both feet, are learned and tracked by the microprocessor algorithms 8 over time and stored in the data store as reference values. Prior to undertaking any analysis on the detected temperature data, these differences and variations are filtered or removed from the profiles prior to further analysis by the microprocessor 8.

These temperature data preparation steps may alternatively be carried out in the temperature comparison module described next.

Temperature Comparison Module

A number of programmes are activated by the data processing module in order to perform analysis processing steps on the detected temperature data for each foot as illustrated in Figure 5. At step 21, the processor 8 compares and evaluates the temperature profiles for each foot to test for any inconsistent local temperature increases that may be indicative of foot inflammation. The evaluation process compares the temperature for each sensing zone of the foot "within the shoe with those identical areas from the other foot as well as comparing temperature between adjacent areas on the same foot for each individual foot. Increased local' temperature (being the temperature between adjacent areas of a foot or between feet) may be caused as a result of either physical activity or time of day variations as well as inflammation. Typical time of day type of variations are learned over a period of time whilst physical activity type differences are filtered and deleted over time at step 22. The filtering of the detected temperature data for each foot produces 'clean' foot temperature data for assessing the possible existence of foot inflammation. Remaining local temperature increases are determined at step 23 and if pre-programmed temperature variation limits (typically of between 1 to 5 ⁰ C) are exceeded, an event will be generated at step 24 and registered by the microcontroller 8. These events 24 are stored for future retrieval and analysis by providing feedback over time of transitory events that is used by the microprocessor 8 to improve the accuracy over time using self-learning. In the system of the invention each foot is used as a reference for the other foot. This eliminates some complexities involved in trying to determine the change in temperature for just one foot. Change in environmental conditions (such as temperature, humidity) can be removed as this is common to both feet. Temperature data can be used as a differential signal. This in turn simplifies the algorithm and processing can be done on a small lower power and cost processor. Even if the both feet have different temperature profiles compared to each other over time these should form a pattern that can be identified. Comparing the difference in the pattern is a more

robust method in determining an issue. This can lead to a alert system that is more reliable and does not provide false alerts to a user.

A user can confirm using good judgement if the algorithm or alarms provided by the system are valid by looking at a simple image of both feet and comparing the immediate or average temperature at different zones and judge if there is a problem with either foot. Even in the absence of an alarm of a user can make a simple judgement that the temperature difference between two zones on either foot is higher than they normally expect and take action. This acts to make the system easy to use and robust.

A central unit can communicate wirelessly with both electronic insoles and this can be used to analyse the temperature and provide comparison data. Each individual insole can comprise simple electronics for only measuring temperature and transmitting to the processing unit. This processing unit can then analyse data and provide feedback to the user. The processing device could be a mobile phone, PDA, PC or custom device.

If the detected temperature data is not available from one of the shoes the microprocessor 8 can analyse the detected temperature data for one foot in isolation by analysing the temperature gradient between a number of adjacent temperature sensing elements 4.

The electronic sensing device 6 of each insole or footwear can incorporate one of more systems to transmit or stream data using a wireless transceiver 19 for example, from the electronic sensing device 6 to data processing module25 incorporated in for example a watch, computer, Personal Digital Assistant (PDA) or mobile telephone device for example. This feature enables detected temperature data and alerts to be transmitted to a medical professional for example for analysis and/or further diagnostic purposes. The data processing module arranged to compare the foot temperature data acquired from either foot may be provided in a watch, key fob, belt clip, computer, PDA, mobile telephone or similar as a separate unit, or alternatively the data processing module may be provided in the microprocessor 8 of one of the shoe inserts. In this event the microprocessor 8 in one of the shoe inserts is arranged to receive temperature data from the other insert and compare to detect a difference and transmit an alarm signal to a visual or audible alarm unit comprised in a watch, key fob, belt clip etc. In a further embodiment the microprocessor 8 in each flexible insert may carry out the comparison. The data processing module can also support a hierarchical sequence of alerts.

Therefore, when an event is initially detected and recorded the processor will activate a local' alert to alert the individual being monitored of a potential problem. This alert can be an audible and/or visual alarm. Alternatively, the alert can be transmitted to the individual's PDA, mobile telephone or other computer type device 25. In the event that the detected local temperature increase does not revert to normal after a pre-defined period of time, the alert will be escalated

such that a medical professional for example is also alerted to a potential problem. Furthermore, the alerts and/or detected temperature data can be on forwarded to other systems and users such as other medical professionals via the internet, wireless connections, radio and SMS message services. Hence, whilst the system is generally factory configured to suit an individual user's requirements, the system can be re-configured locally or remotely as a result of the interfacing capabilities of the system with third party systems.

The electronic sensing device 6 is powered by batteries within the device 6. Alternatively, it is possible to power the electronic sensing device 6 by incorporating an energy conversion device within the individual's shoe to convert the energy generated by the individual as a result of the individual's foot striking the ground. Whilst it is preferable that the microprocessor 8 within the electronic sensing device 6 implements each of the processing steps on the detected temperature data, one or more of the processing steps can alternatively be run by a separate application device such as a mobile telephone, PDA or third party computer system for example. This would further reduce power consumption utilised by the electronic sensing device 6 and extend the time between changes or recharging of the batteries within the electronic sensing device 6.

Additional Features

As mentioned previously, the data processing module is capable of interfacing and downloading detected temperature data to one of a number of different types of third party system 25. As the electronic sensing device 6 incorporates a wireless transceiver 19 for example, detected and analysed temperature data stored within the electronic sensing device 6 may be remotely accessed via the internet for example, by medical professionals and other caregivers. Hence, a flexible insert 2 incorporating one or more temperature sensing elements 4 strategically positioned on or within the flexible insert 2 enables continuous monitoring of the individual's feet so that pote'ntial foot problems can be detected early and remedial action taken. By including pressure sensors 20 within the flexible insert 2 enables pressure to be measured to determine the likelihood of local weight bearing that has the potential to lead to ulceration on the foot/ feet. Furthermore, measuring pressure enables a person's activity to be estimated which will assist in determining movement based changes in foot temperature.

Pressure in this case can be determined through the measuring of the dynamic increase and decrease in temperature due to the mechanical reaction when the insole is compressed and released. As the material of the insole is compressed during walking the insole material (foams or rubber) will be compressed and some of this mechanical energy will be converted into heat and cause a small increase in temperature, when the pressure is then released

the reveres will happen and heat will be released leading to a reduction in temperature. This temperature wave form can be used as an indication of applied pressure and to count steps. This data can then be used to determine a persons activity and assisting in determining movement based changed in foot temperature.

Other Applications

Whilst the invention has been described with reference to the early detection of potential foot ulceration for people with diabetic pulmonary neuropathy, the invention can also be used to: • Determine good shoe fit.

• Determine appropriate load bearing.

• Determine appropriate shoe types in hot or cold environments.

• Detection of infection in other modalities such as broken limbs or pressure bandages.