The present invention relates to needle dislodgement detection device, useful for alerting a patient or medical practitioner when a needle inserted into a patient is dislodged. There is also provided a device to detect excess sweat or blood on a patient's skin.

BACKGROUND TO THE INVENTION

A dialysis apparatus removes _. blood from a patient via an arterial blood line, in order to treat the blood, and then returns the blood to the patient via a venous blood line. If the venous blood line is dislodged, but the arterial blood line remains in place, the patient can lose a great deal of blood very quickly. Fatalities have occurred through this issue, in particular where patients have been sleeping through the dialysis process.

Needle dislodgement detection devices are known to monitor for dislodgement of the venous line in particular. Devices which monitor for wetness due to blood leakage are known.

Over time, the moisture on a patient's skin is likely to change greatly due to sweating and moisture in the surrounding environment. Some known moisture sensitive needle dislodgement devices are programmed not to react to such changes in moisture making them insensitive to early stage blood leaks. Other known moisture sensitive needle dislodgement devices are associated with a large number of false positives. This leads to medical practitioners tending to ignore alarms leading to an increased risk of significant blood leakages going undetected. The taping securing the arterial and venous lines of a dialysis apparatus onto the patient cover a relatively large area and medical practitioners commonly attach known needle dislodgement detection devices to the taping. However, known devices do not provide an alarm where the dislodgement detection device itself becomes detached from the patient. Accordingly, where the taping securing both the venous line and the dislodgement detection device separates from the patient, no alarm is raised as the dislodgement device does not sense any wetness.

To avoid this, known sensors are generally secured directly to the patient's skin. To allow this, less taping of the venous and arterial lines is provided, meaning that they are less secure. As such, the use of such needle dislodgenient devices actually makes the likelihood of dislodgenient of the needle more likely.

US2009322543 discloses a wetness detector system to monitor for needle dislodgement/presence of blood.

US7147615 describes an apparatus comprising a sensor capable of detecting wetness due to blood and a sensor holder adapted to secure the sensor to the patient, such that sensor detects wetness due to blood loss from the patient upon dislodgenient of the needle. The sensor may include a capacitive type sensor that does not come in contact with blood when detecting blood.

WO2009045582 discloses an algorithm for detecting needle dislodgement. The algorithm uses the normal, initial values of a plurality of parameters of the patient and the therapy machine to set criteria or limits for an alarm, and then adjusts those criteria based on the later values of those parameters as they change during one therapy or over several therapies experienced by the patient.

WO2009038836 describes a method of monitoring for needle dislodgement by detecting wetness, generally through RF1D sensors.

However, a sensor comprising ECG electrodes where the sensor recalibrates itself during use is not known. This allows the sensor to take account of gradual changes in moisture, only setting the alarm off for sudden changes in moisture. This provides a highly sensitive sensor whilst avoiding false positives.

STATEMENT OF INVENTION

According to an aspect of the present invention there is provided a device for detecting sudden increases in the moisture on a patient's skin and/or for detecting sudden excess fluid on the skin of a patient comprising:

a resistive sensor including two electrodes suitable for affixment to the patient;

means to calibrate the sensor during use in accordance with gradual changes in moisture on the patient's skin and to provide an upper resistance threshold; an alert activated when the resistance between the two electrodes exceeds the upper resistance threshold.

According to one embodiment, the increase in moisture monitored is due to one or more of blood leakage and sudden excessive sweating.

According to an aspect of the presem invention there is provided a device for detecting sudden increases in the moisture on a patient's skin and/or for detecting sudden excess fluid on the skin of a patient comprising:

a resistive sensor including two electrodes suitable for affixment to the patient, in particular to the skin of a patient during use;

means to calibrate the sensor during use in accordance with gradual changes in moisture on the patient's skin and to provide a lower resistance threshold;

an alert activated when the resistance between the two electrodes falls below the lower resistance threshold.

Where the resistance between the two electrodes falls below the lower resistance threshold, this can be an indication that one or both of the electrodes has ^" become detached from the patient. Accordingly, the incorporation of a lower resistance threshold provides an alert for the dislodgement of the device itself from the patient.

Generally the device is for detecting needle dislodgement.

According te an aspect of the present invention there is provided a device for detecting needle dislodgement when used for dialysis comprising:

a resistive sensor including two electrodes suitable for affixment to the patient, in particular to the skin of a patient during use;

means to calculate an upper resistance threshold;

an alert activated when the resistance between the two electrodes exceeds the upper resistance threshold;

means for partially or completely occluding the arterial line upon activation of the alert.

According to one embodiment, the resistive sensor is provided proximate to the venous line. According to an aspect of the present invention there is provided a device for detecting needle dislodgement when used for intravenously administering a substance to a patient, in particular over a sustained period comprising:

a resistive sensor including two electrodes suitable for affixment to the patient, in particular to the skin of a patient during use;

means to calibrate the sensor during use in accordance with gradual changes in the resistance between the electrodes and to provide an upper resistance threshold a d a lower resistance threshold;

an alert activated when the resistance between the two electrodes exceeds the upper resistance threshold or falls below the lower resistance threshold.

The upper and lower thresholds generally correspond to percentage changes in the resistance level measured on the patient's skin over time periods of 5 seconds or less (generally 1 second or less).

According to one embodiment, the means to calibrate the sensor includes the use of an adaptive algorithm which calculates and adapts the upper and/or lower resistance tlireshold depending on gradual changes in the resistance between the electrodes. According to one embodiment, the means to calibrate the sensor includes:

inputting means to input an initial reading comprising data relating to the resistance between the electrodes at a first time period, and to input a second reading comprising data relating to the resistance between the electrodes at a second time period, calculating means to calculate the rate of change in resistance, and to assess whether the rate of change constitutes a gradual change or a sudden change in resistance.

According to an aspect of the present invention there is provided a method of detecting sudden increases in the moisture on a patient's skin and/or for detecting sudden excess fluid on the skin of a patient comprising:

affixing the electrodes of the resistive sensor as described herein directly or indirectly to the skin of the patient;

obtaining an initial reading of the resistance between the electrodes;

obtaining a second reading of the resistance between the electrodes;

calculating the rate of change in the resistance between the electrodes, and assessing whether the rate of change constitutes a gradual change or a sudden change in resistance depending on the magnitude of the resistance between the electrodes at the initial and second readings;

wherein if the rate of change is a gradual change, the sensor is calibrated in accordance with the gradual change and wherein if the rate of change is a sudden change the alert is activated.

According to one embodiment, there is provided a method of monitoring a patient for conditions associated with excessive sweating comprising the use of a device as described herein.

In various embodiments of the present teachings, the methods of monitoring a patient generally can include inputting into a computer including a computer readable medium measurements of the resistance between the electrodes; and causing the computer to calculate the rate of change in resistance and to determine whether the rate of change constitutes a sudden change in resistance. Where a sudden change is determined, an alert is generally activated.

The methods described herein including those above can include transmitting, displaying, storing, printing; or outputting to a user interface device, a computer readable storage medium, a local computer system or a remote computer system, information related to the resistance between the electrodes, and the changes in the resistance. The methods also can include recommending, authorizing, or effecting partial or complete occlusion of the arterial line where a change in the resistance between the electrodes is determined as being sudden. Various features and steps of the methods of the present teachings can be carried out with or assisted by a suitably programmed computer, specifically adapted, designed and/or structured to do so.

In another aspect, the present teachings include a suitably programmed computer comprising software code adapted to perform a method of monitoring a patient, wherein execution of the software code by one or more processors of the suitably programmed computer causes the one or more processors to carry out the step of calculating the rate of change of resistance between the electrodes and determining whether the rate of change constitutes a sudden change in resistance. In yet another aspect, the present teachings provide systems and kits for detecting sudden increases in the moisture on a patient's skin and/or for detecting sudden excess fluid on the skin of a patient. A system can include an analytical instrument adapted to measure the resistance of the patient's skin, and a suitably programmed computer adapted to calculate the rate of change of resistance on the patient's skin, and to calculate whether the rate of change constitutes a sudden change in resistance.

Kits are also provided for monitoring a patient, and for detecting sudden increases in the moisture on a patient's skin. The kit may include the device as provided herein and instructions for use.

According to one embodiment, there is provided a method of intravenously administering a substance to a patient, in particular over a sustained period comprising the use of a device as described herein. According to one embodiment, there is provided a method of dialysis, in particular for a patient suffering from complete or partial kidney failure comprising the use of a device as described herein.

According to one embodiment, there is provided a dialysis apparatus comprising the device as described herein.

According to one embodiment, there is provided a method of monitoring a patient during dialysis comprising the use of a device as described herein. According to one embodiment, there is provided a method of medical treatment comprising the steps of:

inserting a needle into a patient;

affixing the device as described herein onto a patient to monitor for the dislodgement of the needle.

In particular the method of medical treatment may involve the intravenous administration of a substance or a method of dialysis. According to one embodiment, there is provided a method of medical treatment comprising affixing the device as described herein to a patient suffering from a condition in order to monitor for excessive sweating. DEFINITIONS

The "arterial line" of a dialysis apparatus is the blood line removing blood from the patient for treatment.

The "venous line" of a dialysis apparatus is the blood line returning blood to the patient following treatment of the blood.

All numerical values provided incorporate 10% less than and 1 0% more than the numerical value provided. Throughout the Application, where devices are described as having, including, or comprising specific components, or where processes or methods are described as having, including, or comprising specific process steps, it is contemplated that devices of the present teachings also consist essentially of, or consist of, the recited components, and that the processes or methods of the present teachings also consist essentially of, or consist of, the recited process steps.

In the Application, where an element or component is said to be included in and/or selected from a list of recited elements or components, it should be understood that the element or component can be any one of the recited elements or components, or the element or component can be selected from a group consisting of two or more of the recited elements or components. Further, it should be understood that elements and/or features of a composition, an apparatus, or a method described herein can be combined in a variety of ways without departing from the spirit and scope of the present teachings, whether explicit or implicit herein. The use of the terms "include," "includes", "including," "have," "has," or "having" should be generally understood as open-ended and non-limiting unless specifically stated otherwise.

The use of the singular herein includes the plural (and vice versa) unless specifically stated otherwise. In addition, where the use of the term "about" is before a quantitative value, the present teachings also include the specific quantitative value itself, unless specifically stated otherwise. As used herein, the term "about" refers to a ± 10% variation from the nominal value unless otherwise indicated or inferred. It should be understood that the order of steps or order for performing certain actions is immaterial so long as the present teachings remain operable. Moreover, two or more steps or actions may be conducted simultaneously.

The foregoing as well as other features and advantages of the present teachings will be more fully understood from the following figures, description, examples, and Claims.

Device

According to an aspect of the present invention there is provided a device for detecting sudden increases in the moisture on a patient's skin/detecting sudden excess fluid on the skin of a patient comprising:

a resistive sensor including two electrodes suitable for affixment to the patient, in particular to the skin of a patient during use;

means to calibrate the sensor during use in accordance with gradual changes in moisture on the patient's skin and to provide an upper resistance threshold;

an alert activated when the resistance between the two electrodes exceeds the upper resistance threshold.

According to one embodiment, the increase in moisture monitored is due to one or more of blood leakage and sudden excessive sweating.

The moisture on the skin of a patient can change significantly over time, for instance due to changes in the humidity of the surrounding environment, or due to the patient sweating. As such, during lengthy procedures such as dialysis, the moisture on a patient ^' s skin can alter. In order to take these significant alterations in moisture into account, known needle dislodgement devices are either less accurate than they may be and alarm only upon contact of large amounts of liquids, or are associated with a significant number of false positives. The device of the present invention self-calibrates once it has been attached to the patient, meaning that the upper threshold limit changes with changes to the moisture and thus the resistance of the skin. The device of the present invention is less likely to be triggered by false alarms as the alert activation levels change to suit the condition

The device of the present invention overcomes these problems by the alert only being activated due to sudden changes in moisture levels on the skin. Gradual changes in moisture, and thus resistance between the electrodes are used to calibrate the device.

The resistance of a person's skin varies due to a number of factors, including the area of the patient's body and the moisture of the skin. In a normal state, a person's skin generally has a resistance of more than 100,000 ohms, generally more than 300,000 ohms, suitably more than 500,000 ohms. The resistance of a person's skin may be from around 200,000 to around 1,000,000 ohms in a normal state, generally 200,000 to 900,000, suitably around 200,000 to around 800,000. The resistance of the skin can change during use. and the device of the present invention allows for gradual changes, or drift during use (for instance due to normal levels of sweating). However, sudden changes in resistance are cause for concern. The percentage change in resistance required to cause alarm depends on the initial resistance of the patient's skin.

During use of the device, measurements of the resistance of the skin are measured regularly, generally at least every minute, typically at least every 30 seconds, suitably at least every 10 seconds, more suitably at least every second, preferably at least every 0.5 seconds. Generally measurements of the resistance of the skin are provided at least every second, suitably for each time period of between 0.5 and 1 seconds. Sudden changes tend to be changes which occur between consecutive measurements.

The percentage change required to activate the alert is generally smaller the higher the initial resistance.

Where the initial or measured resistance is less than 80,000 ohms, a change of 0.7% or more over a time period of 1 second or less would activate the alert, suitably a change of 0.8% or more over a time period of 1 second. According to one embodiment, the time period under consideration would be around 0.5 seconds. Where the initial or measured resistance is 80,000 to 90,000 ohms, a change of 0.9% or more over a time period of 1 second or less would activate the alert, suitably a change of 1 .0% or more over a time period of 1 second. According to one embodiment, the time period under consideration would be around 0.5 seconds.

Where the initial or measured resistance is 90,000 to 150,000 ohms, a change of 1 .5% or more over a time period of 1 second or less would activate the alert, suitably a change of 2.0% or more over a time period of 1 second. According to one embodiment, the time period under consideration would be around 0.5 seconds.

Where the initial or measured resistance is 160,000 to 1 80,000 ohms, a change of 2.5% or more over a time period of 1 second or less would activate the alert, suitably a change of 3.0% or more over a time period of 1 second. According to one embodiment, the time period under consideration would be around 0.5 seconds.

Where the initial or measured resistance is 190,000 to 280.000 ohms, a change of 4% or more over a time period of 1 second or less would activate the alert, suitably a change of 5% or more over a time period of 1 second. According to one embodiment, the time period under consideration would be around 0.5 seconds.

Where the initial or measured resistance is 290,000 to 600,000 ohms, a change of 6% or more over a time period of 1 second or less would activate the alert, suitably a change of 7% or more over a time period of 1 second. According to one embodiment, the time period under consideration would be around 0.5 seconds.

Where the initial or measured resistance is 61 0,000 to 750,000 ohms, a change of 8% or more over a time period of 1 second or less would activate the alert, suitably a change of 9% or more over a time period of 1 second. According to one embodiment, the time period under consideration would be around 0.5 seconds.

Where the initial or measured resistance is more than 760,000 ohms, a change of 1 0% or more over a time period of 1 second or less would activate the alert, suitably a change of 32% or more, generally 13% or more over a time period of 1 second. According to one embodiment, the time period under consideration would be around 0.5 seconds.

A change of 1 0% or more in the resistance level over a time period of 1 second or less would generally constitute a sudden change in resistance regardless of the initial or measured resistance value.

As noted above, the device of the present invention allows for gradual changes, or drift during use. Generally changes 50% or less than those which activate the alert constitute gradual changes in resistance. Such changes may be used to calibrate the device during prolonged use.

Where changes in resistance are 50%» or less than those which activate the alert, the device is calibrated, and the alert activation threshold is adjusted accordingly. If the skin resistance increased by. for instance 30%o of the percentage change which activates the alert, the alert activation threshold would be increased. Likewise, if the skin resistance decreased by, for instance 30% of the percentage change which activates the alert, the alert activation threshold would be decreased.

Where changes in resistance are more than 50% of those which activate the alert, the device is not calibrated and the alert activation threshold is not adjusted accordingly. This takes account of minor leakages of fluid onto the skin, and ensures the device of the present invention is highly responsive.

According to an aspect of the present invention there is provided a device for detecting sudden increases in the moisture on a patient's skin/detecting sudden excess fluid on the skin of a patient comprising:

a resistive sensor including two electrodes suitable for affixment to the patient, in particular to the skin of a patient during use;

means to calibrate the sensor during use in accordance with gradual changes in moisture on the patient's skin and to provide a lower resistance threshold;

an alert activated when the resistance between the two electrodes falls below the lower resistance threshold. Where the resistance between the two electrodes falls below the lower resistance threshold, this can be an indication that one or both of the electrodes from the device itself have become

r

detached from the patient. Where this happens, the patient and medical staff can suffer from a false sense of security. They will be relying on the device to alert when the skin of the patient is the subject of sudden changes in moisture and may minimize visual checks j accordingly. The device of the present invention activates the alert where the device becorhes detached from the patient. i

The device may be affixed to the means for securing a needle in the patient; in particular the device may be affixed to taping to secure a needle in the patient. Where tlje means for securing the needle becomes detached from the patient, the device will also become detached. The needle is then far more likely to become dislodged.

A significant proportion of patients requiring dialysis suffer from confusion (including conditions such as dementia and confusion due to sudden changes in blood sugar caused by diabetes). In a confused state, patients may try to remove the needles inserted into them and any monitoring device. The device of the present invention alerts medical practitioners to this as removal of the device would cause the resistance level to fall below the lower threshold level, thus activating the alert.

According to an aspect of the present invention there is provided a device for detecting sudden increases in the moisture on a patient's skin /detecting excess fluid on the skin (in particular due to needle dislodgement) comprising:

a resistive sensor including two electrodes suitable for affixment to the patient, in particular to the skin of a patient during use; \

means to calibrate the sensor during use in accordance with gradual changes in moisture on the patient's skin and to provide an upper resistance threshold and a lower resistance threshold; j

an alert activated when the resistance between the two electrodes exceeds the upper resistance threshold or falls below the lower resistance threshold.

According to one embodiment, the device is programmed with a calibration graph prior to use thereof. The skilled person would be able to produce a suitable calibration graph using the Table la and 1 b herein. Typically the alert is audible, alternatively or additionally the alert may be visual. The alert may include LEDs and an audible alarm. Generally the alert requires intervention before it stops.

According to one embodiment, the device monitors for sudden increases in moisture on the patient's skin due to needle dislodgement and associated blood leakage. Alternatively or additionally, the sudden increases in moisture on the patient ^' s skin may be due to excessive sweating.

Generally where there has been a leakage of blood onto a patient's skin, the resistance value would be less than 1 000 ohms, typically less than 500 ohms, suitably less than 1 00 ohms.

Where the patient is sweating profusely, for instance due to the onset of a hypoglycaemic state, the resistance would generally be less than 5000 ohms, typically 1000 to 4000 ohms.

In contrast, where the patient is sweating normally, the resistance value would generally be more than 100,000 ohms, generally more than 300,000 ohms. As well as being useful in monitoring for needle dislodgement, the device of the present invention is useful in monitoring patients for sudden excessive sweating which is generally caused by an underlying health problem, for example sudden changes in blood pressure or the onset of a hypoglycaemic state. The activation of the alert due to excessive sweating can be useful in alerting medical practitioners that a patient may be having difficulties, and should be the subject of more intensive scrutiny. For instance, a patient suffering from heart problems or diabetes may be monitored using the device of the present invention. Sudden decreases in blood pressure and the onset of a hypoglycaemic state are commonly associated with sweaty or clammy skin. This sudden increase in moisture on the skin would push the resistance between the electrodes over the upper resistance threshold, thus activating the alert.

A large proportion of patients requiring dialysis are suffering from other underlying health problems, for instance diabetes, obesity and heart disease. According to some estimates, 20% or more of patients who require dialysis also suffer from diabetes. According to one embodiment of the invention, the alert of the device is activated upon increases in moisture due to blood leakage or due to sudden excessive sweating. According to an aspect of the present invention there is provided a device for detecting needle dislodgeraent, said needle used to return blood to the body of the patient following dialysis, the device comprising:

a resistive sensor including two electrodes suitable for affixment to the patient, in particular to the skin of a patient during use;

means to calculate/provide an upper resistance threshold;

an alert activated when the resistance between the two electrodes exceeds the upper resistance threshold

means for partially or completely occluding the arterial line upon activation of the alert.

Typically the needle is attached or associated with the venous line.

According to one embodiment, the device of the present invention includes check means to ensure that the initial resistance of the skin of the patient falls within a predetermined range.

The check means may include an indication of whether the initial resistance reading falls within a predetermined range. The indication may be a visual and/or audible indication, for instance a light which flashes one colour where the initial resistance reading falls outside the predetermined range and another colour where the initial resistance falls within the predetermined range.

Generally the electrodes of the resistive sensor may be attached directly to the skin of the patient. Alternatively, the electrodes of the resistive sensor may be attached to securement means, for instance means to secure a needle into the patient, or a thermometer onto a patient. Typical securement means include taping. The means for partially or completely occluding the arterial line is generally a clamp, for instance a solenoid clamp.

The means for partially or completely occluding the arterial line is directly or indirectly in communication with the alert for instance via an electrical or fluid connection. According to one embodiment, the means for partially or completely occluding the arterial line is directly or indirectly in communication with the aJert via an electrical cable or Blue Tooth.

Where the arterial line is partially or completely occluded, the dialysis apparatus will generally sense this and stop pumping blood from the patient. The rate of blood flow from a patient during dialysis is high, typically up to 400ml/min. Partially or completely occluding the arterial line upon activation of the alert ensures that blood isn't pumped from the patient whilst the venous line is dislodged. Even small intervals of such pumping can lead to large blood losses. Depending on the general health of the patient, even relatively short periods of detachment of the venous line can lead to very serious affects. In some cases, detachments of 5 minutes can lead to the death of the patient.

According to an aspect of the present invention there is provided a method of detecting sudden increases in the moisture on a patient's skin and/or for detecting sudden excess fluid on the skin of a patient comprising:

affixing the electrodes of the resistive sensor as described herein directly or indirectly to the skin of the patient;

obtaining an initial reading of the resistance between the electrodes;

obtaining a second reading of the resistance between the electrodes;

calculating the rate of change in the resistance between the electrodes, and

assessing whether the rate of change constitutes a gradual change or a sudden change in resistance depending on the magnitude of the resistance between the electrodes at the initial and second readings;

wherein if the rate of change is a gradual change, the sensor is calibrated in accordance with the gradual change and wherein if the rate of change is a sudden change the alert is activated.

According to one embodiment, the method of the present invention includes a check step to ensure that the initial resistance reading falls within a predetermined range. Where the initial resistance reading falls below the lower limit of the predetermined range, the electrodes should be moved further apart. Where the initial resistance reading falls above the upper limit of the predetermined range, the electrodes should be moved closer together.

The predetermined range generally incorporates the normal range of resistances for sk in.

The device of the present invention is generally portable.

According to one embodiment, the device includes a low battery alert, activated prior to the power in the battery running out.

Generally the device of the present invention would be formed from water tight material with minimal joins to allow effective cleaning of the device between patients.

Calibration

According to one embodiment, the means to calibrate the sensor includes the use of an adaptive algorithm which calculates and adapts the upper and/or lower resistance threshold depending on gradual changes in the resistance between the electrodes.

Gradual changes in resistance are generally those associated with increases in moisture on the patient's skin due to the patient sweating. Sudden increases in resistance are generally associated with increases in moisture on the patient's skin due to blood leakages.

The calibration algorithm is generally set within software used to programme the device. The upper and lower alarm thresholds vary dependent on the resistance measured between the electrodes. The alarm thresholds are generally a percentage of the measured value so large resistance values typically require a greater change in resistance to trigger the alert and lower resistance values requiring smaller changes in resistance to trigger the alert.

According to one embodiment, the means to calibrate the sensor includes:

inputting means to input an initial reading comprising data relating to the resistance between the electrodes at a first time period, and to input a second reading comprising data relating to the resistance between the electrodes at a second time period, calculating means to calculate the rate of change in resistance, and to assess whether the rate of change constitutes a gradual change or a sudden change in resistance. The means to calibrate the sensor may be in the form of a computer programme on a computer readable medium. The device is typically programmed with the computer programme during manufacture.

In another aspect, the present teachings include a suitably programmed computer comprising software code adapted to perform a method of monitoring a patient, wherein execution of the software code by one or more processors of the suitably programmed computer causes the one or more processors to carry out the step of calculating the rate of change of resistance between the electrodes and determining whether the rate of change constitutes a sudden change in resistance.

The rate of change of resistance, and the determination as to whether the rate of change constitutes a sudden change in resistance can be calculated using a suitably programmed computer, which can include other electronic devices. Suitable programming can include, for example, software, firmware, or other program code that enables the computer to process, analyze, and/or convert measured resistance levels to a rate of change in resistance, and to interpret whether the rate of change in resistance constitutes a sudden change. Such programming can be included within the computer, or can be embodied on a computer readable medium such as a portable computer readable medium. Of course, other steps or processes of the present teachings can be carried out using or can be assisted by a suitably programmed computer, for example control of dialysis, the recommending and/or authorizing of complete or partial occlusion of the arterial line, and the transmitting, displaying, storing, printing, and/or outputting of information.

Information may be outputted or displayed to a user interface device, a computer readable storage medium, or a local or remote computer system. Such information can include, for example, the measured levels of resistance, the rate of change of resistance, and equivalents thereof (all of which can include or be, e.g., a graph, a figure, a symbol, and the like), and any other data related to the methods described herein. Displaying or outputting information means that the information is communicated to a user using any medium, for example, orally, in writing, on a printout, by visual display computer readable medium, computer system, or other electronic device (e.g., smart phone, personal digital assistant (PDA), laptop, etc.). It will be clear to one skilled in the art that outputting information is not limited to outputting to a user or a linked external component(s), such as a computer system or computer memory, but can alternatively or additionally be outputted to internal components, such as any computer readable medium.

Computer readable media can include, but are not l imited to, hard drives, floppy disks, CD- ROMs, DVDs, and DATs. Computer readable media does not include carrier waves or other wave forms for data transmission. It will be clear to one skilled in the art that the various methods disclosed and claimed herein, can, but need not be. computer-implemented, and that, for example, the displaying or outputting step can be done by, for example, by communicating to a person orally or in writing (e.g., in handwriting).

According to an aspect of the ^" present invention there is provided a method of detecting sudden increases in the moisture on a patient's skin and/or for detecting sudden excess fluid on the skin of a patient comprising:

affixing the electrodes of the resistive sensor as described herein directly or indirectly to the skin of the patient;

obtaining an initial reading of the resistance between the electrodes;

obtaining a second reading of the resistance between the electrodes;

calculating the rate of change in the resistance between the electrodes, and

assessing whether the rate of change constitutes a gradual change or a sudden change in resistance depending on the magnitude of the resistance between the electrodes at the initial and second readings;

wherein if the rate of change is a gradual change, the sensor is calibrated in accordance with the gradual change and wherein if the rate of change is a sudden change the alert is activated.

The assessment of whether the change in resistance is gradual or sudden may involve the use of an algorithm using the rate of change in resistance and the magnitude in resistance at the initial and second readings.

The algorithm may form part of a computer programme.

The means for calibrating the sensor may include a calibration curve detailing upper and/or tower resistance threshol ds at different magnitudes of resistance. Generally the sensor is calibrated during use through the steps of:

inputting an initial reading comprising data relating to the resistance between the electrodes at a first time period,

inputting a second reading comprising data relating to the resistance between the electrodes at a second time period,

calculating the rate of change in resistance

assessing whether the rate of change constitutes a gradual change or a sudden change in resistance. Generally the assessment step takes into account the magnitude of the resistance between the electrodes at the initial and second readings as well as the rate of change.

The method of calibration may involve the inputting and assessment of additional information such as one or more of temperature, pH of the moisture and colour analysis

The method of calibration may involve inputting multiple readings.

The resistance between the electrodes is generally a measure of the moisture on the patient's skin.

In general, the higher the resistance level, the larger the change in resistance necessary for the upper and/or lower threshold to be breached, activating the alert.

At high resistance levels, for instance 1 500 ohms or more, relatively large changes in resistance would be considered gradual, and be used to calibrate the device.

At low resistance levels, for instance 500 ohms or less, relatively small changes in resistance would be considered gradual, and be used to calibrate the device. According to one embodiment, for resistances of 1 00 to 2500 ohms, changes of 500 ohms per hour would be considered gradual and would be used to calibrate the device. Suitably, changes of 200 to 250 ohms per hour would be considered gradual for resistances of 1250 to 1000. Typically changes of 100 to 150 ohms per hour would be considered gradual for resistances of 1000 to 750. Generally changes of 50 to 100 ohms per hour would be considered gradual for resistances of 750 to 500. For resistances of 500 to 250 ohms, changes of 10 to 50 ohms would generally be considered gradual. For resistances of less than 250 ohms, changes of 5 to 10 ohms would generally be considered gradual. Sudden changes in resistance would generally be changes greater than those detailed above. Changes in resistance resulting in sudden high resistance would mean that the resistance exceeded the upper threshold, thus activating the alert. Changes in resistance resulting in sudden low resistance would mean that the resistance fell below the lower threshold, thus activating the alert.

The upper limit is determined from various factors, including the resistance level between the two electrodes.

The lower limit is determined from various factors, including the resistance level between the two electrodes.

The resistance range to be measured by the device of the present invention is generally from around 100k to 1.7 in ohms, According to one embodiment, skin resistance may be measured as conductance. Conductance can be easier to calculate than resistance. Skin conductance may be measured and used as a reference for changes of resistance/conductance on the surface of the skin.

Method of Treatment

According to one embodiment, there is provided a method of monitoring a patient for sudden excessive moisture on the patient's skin comprising the use of the device as described herein.

Typically the method includes the steps of:

fixing the electrodes of the device onto the patient's skin.

optionally allowing the device to equilibrate,

wherein the alert of the device is activated if the skin of the patient undergoes a sudden increase in moisture. Generally the method is used for patients undergoing the sustained intravenous administration of a substance and the electrodes are fixed proximate to the needle intravenously administering the substance. According to one embodiment, there is provided a method of medical treatment comprising the steps of:

inserting a needle into a patient;

affixing the device as described herein onto a patient to monitor for the dislodgement of the needle.

In such embodiments, where the alert is activated, the intravenous administration of the substance is generally automatically stopped.

Generally the method is used for patients undergoing a dialysis procedure and the electrodes are fixed proximate to the needle attached to the venous line of the dialysis apparatus.

In such embodiments, where the alert is activated, the blood pump of the dialysis apparatus is stopped while further investigations are undertaken. According to one embodiment, there is provided a dialysis apparatus comprising the device as described herein.

According to one embodiment, there is provided a method of monitoring a patient during dialysis comprising the use of a device as described herein.

According to one embodiment, there is provided a method of monitoring a patient for conditions associated with excessive sweating comprising the use of a device as described herein. The method may be used to monitor patients identified as high risk, for instance due to an underlying health problem or condition.

Suitably the condition is heart disease (including angina, heart attack and congestive heart failure), stroke, deep vein thrombosis, pulmonary embolism, atrial fibrillation, mesenteric ischaemia, mesenteris venous thrombosis _; renal vein thrombosis, obesity, difficulty in breathing, increased blood pressure, diabetes or partial or complete kidney failure resulting in the need for dialysis. In such embodiments, where the alert is activated, medical practitioners generally monitor the patient closely, typically observing one or more of blood pressure, temperature, blood sugar level.

According to one embodiment, there is provided a method of monitoring a patient for conditions associated with sudden excessive sweating comprising the use of a device as described herein. ^'

According to one embodiment, there is provided a method of intravenously administering a substance to a patient, in particular over a sustained period comprising the use of a device as described herein.

According to one embodiment, there is provided a method of dialysis, in particular for a patient suffering from complete or partial kidney failure comprising the use of a device as described herein.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

Throughout the description and Claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", mean "including but not limited to", and are not intended to (and do not) exclude other moieties, additives, components, integers or steps. All documents referred to herein are incorporated by reference.

The present invention will now be described by way of example only with reference to the accompanying figures in which:

Table l a and table l b show the percentage changes within 1 second or less required to activate the alert at different resistance values;

Figure 1 shows a front-view photograph of a device according to the present invention;

Figure 2 shows a rear- view photograph of a device according to the present invention Figure 3 shows a front-view schematic representation of a device according to the present invention;

Figure 4 shows a calibration curve for the device of Figure 3, including the upper and lower threshold resistances for different magnitudes of resistance.

Example

The device of the present invention as illustrated in the Figures may be operated as detailed below.

Operation

1 - Connect electrodes below and each side of needle site, about 1 inch apart;

2- Switch on alarm;

3- Unit goes into test mode and each led and sounder is switched on and off. If the resistance values are within the predetermined range the green Led will double flash. The left hand yellow led flashing means the resistance value is too high and this flashing provides an indication that the electrodes are too far apart. The right hand yellow led flashing means the resistance value is too low and this flashing provides an indication that the electrodes are too close together.

4- Once the green led has stopped double flashing it goes into single flash mode to indicate that the device is now active;

5- T!ie device may be switched off by pressing the on button for 3 seconds.

If the resistance between the electrodes moves above an upper resistance threshold or below a lower resistance threshold the alert led will flash and the sounder will sound. The unit can then be switched off by pressing on the switch for 3 seconds 2. There is a low battery alarm which is a continuous double bleep and double flash.

Electronics

ECG electrodes are placed on the skin below the needle site at a distance of about 2cm apart. When switched on, the device undergoes a self check, and then measures the initial skin resistance reading between the electrodes. Skin can have many different resistance values. If the initial resistance reading is towards or above the upper threshold, the device provides an indication that the electrodes should be moved closer together. If the initial resistance reading is towards or less than the lower threshold, the device provides an indication that the electrodes should be moved further apart. The device measures the resistance between the electrodes and monitors for sudden changes which could be indicative of moisture across the electrodes. The device is controlled by a microchip programmed with custom software. The software monitors for sudden changes in skin resistance, and if these sudden changes occur, an alert is activated. A person's skin resistance can vary greatly throughout the day. The device of the present invention tracks theses gradual changes and alters the upper and lower resistance thresholds eliminating false positives. If an electrode loses contact the alert will also be activated. In use, the electrodes are placed on a patient's skin and the initial resistance is measured. The user confirms that the initial resistance is within the operating range of the device. The following values are calculated throughout the monitoring process:

Output: the measured value of resistance on the skin of the patient, this is generally measured every few seconds, suitably between every 0.5 and 1 second period.

L Drift High: a stored value determined as a percentage of the previous measured value of resistance. Generally the L Drift High value is a change of 20 to 25% of the percentage change in the measured resistance value required to activate the alert.

Drift High: a stored value determined at a higher percentage change in the previous measured value of resistance than the L Drift High value. Generally the L Drift High value is a change of 40 to 50% of the percentage change in the measured resistance value required to activate the alert.

High Alarm: a stored value determined at a higher percentage change in the previous measured value of resistance than the Drift High value. Typical percentage changes required to activate the alert at different measured values of resistance are as provided in Table 1 . L Drift Low: a stored value determined as a percentage of the previous measured value of resistance. Generally the L Drift Low value is a change of 20 to 25% of the percentage change in the measured resistance value required to activate the alert.

Drift Low: a stored value determined at a lower percentage value of the previous measured value of resistance than the percentage value used to calculate the L Drift Low value. Generally the L Drift Low value is a change of 40 to 50% of the percentage change in the measured resistance value required to activate the alert.

Low Alarm: a stored value determined at a lower percentage value of the previous measured value of resistance than the percentage value used to calculate the Drift Low value. Typical percentage changes required to activate the alert at different measured values of resistance are as provided in Table 1.

If the initial resistance value is less than the stored L drift H value from the previous use of the device, and higher than the previous measured value all stored values remain unchanged. Measurement of the resistance of the patient's skin, and changes in the resistance are measured, and are used to calculate the L Drift High, Drift High, High Alarm, L Drift Low, Drift Low and Low Alarm values. These values alter as the measured value of the resistance of the skin alters during the monitoring process. Exemplary values are provided in Table 1 . At lower resistance levels, the drift and alarm triggers would have to be much less than at higher resistance levels. As the resistance of blood is so low, a larger change in the resistance is generally required to activate the alarm for low measured resistance levels compared to the change in resistance required to activate the alarm for high measured resistance levels. Liquid spillage between the electrodes (in particular blood) would saturate the readings because the resistance values measured would be tens to hundreds of ohms and not thousands of ohms as measured in non-alarm conditions.

Various modifications and variations of the described aspects of the invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes of carrying out the invention which are obvious to those skilled in the relevant fields are intended to be within the scope of the following claims.