Cannula alert system

Abstract

The invention concerns an alert system for detecting dislodgement or misplacement of a cannula when inserted into a user, or adverse subject event in relation to cannula status in a subject, comprising one or more sensors ideally positioned for detection of one or more parameters to indicate cannula status; a kit of parts relating to said system; and an associated method of detecting misplacement or dislodgement comprising the use of said system.

Description

[0001] Cannula alert System

[0002] Field of the Invention

[0003] The invention concerns an alert system for detecting dislodgement and / or misplacement of a cannula when inserted into a user, or adverse events in relation to its presence in the user, comprising one or more sensors ideally positioned for detection of one or more parameters to indicate cannula status; a kit of parts relating to said system; and an associated method of detecting adverse events, misplacement or dislodgement comprising the use of said system.

[0004] Background of the Invention

[0005] In healthcare settings, vascular access to a patient may be required for numerous reasons, such as when undergoing monitoring, testing, diagnosis, and / or treatment. For example, an intravenous (IV) cannula can be used to administer the medication directly into patients’ veins, including basic saline to drugs with very high acid and alkaline levels (e.g., antibiotics). The peripheral intravenous cannula (PIVC) is the most frequently used invasive medical device; At any time, 1 in 3 hospital in-patients in the UK has a PIVC in place. They are used on all patients from newborns to the elderly, and for fluid replacement, antibiotics and life-saving chemotherapy. PIVC are typically used in veins of the hands, arms, and in difficult cases in feet, legs and in some cases via the scalp

[0006] A common type of cannula is an over-the-needle peripheral IV cannula. As its name implies, the over-the-needle PIVC may be mounted over an introducer needle having a sharp distal tip. The cannula and the introducer needle may be assembled so that the distal tip of the introducer needle extends beyond the distal tip of the cannula with the bevel of the needle facing up away from skin of the patient. The cannula and introducer needle are generally inserted at a shallow angle through the skin into the vasculature of the patient. In order to verify proper placement of the introducer needle and / or the cannula in the blood vessel, a clinician generally confirms that there is “flashback” of blood in a flashback chamber of the cannula assembly. Once placement of the needle has been confirmed, the clinician may temporarily occlude flow in the vasculature and remove the needle, leaving the cannula in place for future blood withdrawal or fluid infusion.

[0007] Therefore, millions of intravenous infusions are carried out every year in the UK and rely on a safe and intact PIVC. However, it is estimated that up to 40% of cannulas can result in irritation, injury, infection, and harm ranging from permanent scarring to catastrophic life-changing injuries. Infections from peripheral cannula are listed in the 2019 Top 10 Patient Safety Concerns by the Emergency Care Research Institute (ECRI). ECRI strongly encourages organisations and the research community to identify sources of infection and develop strategies to reduce patient risk. The following are the 5 key PIVC problems that can occur in association with adverse events, incorrect cannula placement and / or dislodgement:

[0008] Infection

[0009] - Infiltration, wherein a collection of IV fluid can leak into the tissue, commonly medium range pH, non-vesicant, materials. Non-vesicants are IV solutions that generally do not cause ischaemia or necrosis, but can result in long-term injury as a result of local inflammatory reactions or compression of the surrounding tissues, resulting in compartment syndrome;

[0010] - Extravasation, wherein leakage of intravenously (IV) infused, and potentially damaging, vesicant materials into the extravascular tissue around the site of infusion, which can cause blistering and potential tissue necrosis. Acidic or alkaline preparations and those with greater osmolarity than plasma may cause extravasation injuries. Cytotoxic drugs commonly cause extravasation injury;

[0011] - Detachment, wherein the IV cannula can be dislodged, leading to spillage of fluid. This can cause local trauma depending on the material, but also causes issue in clinical field in terms of determining drug dosing, for example, as well as wastage of expensive therapeutic agent;

[0012] - Phlebitis (or venous inflammation), which can be broadly classified into Mechanical (when the PIVC moves inside the vein causing friction or is too wide for the vein), Chemical (caused by the medication often associated with the pH range or osmolality, or due to infectious agent (bacterial or the like, which can arise from contamination of the IV tip, hygiene of the medical professionals or inadequate cleaning of the site pre insertion).

[0013] Presently, there is no way to detect issues of cannula placement and / or dislodgement, or other adverse events with cannula presence in a subject; there is no way to detect a dislodged cannula, which can result in medication leaking out of the cannula, wasting critical treatments failure often results in serious adverse events leading to patient discomfort, delays in treatment, increased health care costs and even death. In most cases, the only way to monitor cannula is to inspect them at regular intervals visually. The Visual Infusion Phlebitis scale (VIP) is in place across the UK, however, this still relies on regular manual checks, which are subjective and often miss early signs of harm. Relying on nursing staff to visually inspect cannula (including isolated patients) remains a significant issue of concern. Further, for many patients (such as the elderly or those with dementia), the cannula is often covered with a bandage to reduce dislodgement. This means the cannula insertion site is not easily visible, and signs of damage can go unnoticed. Further, especially amongst elderly and the young, reporting of associated symptoms with incorrect placement or dislodgement may not be reported.

[0014] We therefore herein disclose a device and system for monitoring cannula placement, status, and / or determining cannula dislodgement to address the afore problems associated with conventional monitoring.

[0015] Statements of Invention

[0016] According to a first aspect of the invention there is provided an alert system for detecting incorrect cannula placement and / or dislodgement in a subject, or adverse subject event in relation to cannula status in a subject, said system comprising: i) at least one pad, adapted for adhering to the skin surface and positioning over, or about, a cannula approximate the point at which the cannula is inserted into or under the skin of the subject; and ii) at least one or more sensors associated with said at least one or more pads and configured to detect one or more parameters selected from: pressure, temperature and / or position or movement of the cannula.

[0017] Reference to cannula, or interchangeably a catheter, refers to a hollow tube, used medically, for the introduction or withdrawal of fluid from the body. In a preferred embodiment, the cannula is an intravenous or intraarterial catheter for, but not limited to administering medication, withdrawal of blood samples, hemodialysis treatment; and subcutaneous catheters for delivery of drugs. In a preferred embodiment, the cannula is a peripheral intravenous cannula or catheter (PIVC). As is known in the art, a PIVC, also known as a peripheral venous catheter, peripheral venous line, peripheral venous access catheter, or peripheral intravenous catheter, is a small, flexible tube inserted into a peripheral vein for venous access to administer intravenous therapy such as medication fluids. In use, commonly, lumen is fitted with a sharp pointed trocar to facilitate insertion, which can be subsequently removed while the small plastic cannula remains in place. The cannula is then fixed by taping it to the patient's skin or using an adhesive dressing. In a preferred embodiment, the alert system is for use with a PIVC placed in a vein on the hand or arm.

[0018] As will be appreciated by those skilled in the art, reference to incorrect placement of the cannula refers to the clinical scenario wherein, during or following insertion of the cannula, it is not accurately positioned within the blood vessel to remove or administer fluid, typically instead being located subdermally. In this manner, this can cause issue with infection, infiltration, and / or extravasation as disclosed herein. Further, reference herein to dislodgement refers to the clinical scenario wherein the cannula following insertion, may be inadequately fixed such that it can move within the blood vessel or vein, thus causing issues of phlebitis, or alternatively become displaced such that it is partially or fully removed from the vessel in which it is inserted leading to spillage of fluid.

[0019] Further still, as will be appreciated by those skilled in the art, reference herein to adverse event in relation to cannula status refers to occurrences or complications where status of the cannula require attention of the medical practitioner. As is known, problems can occur with cannulas not necessarily down to cannula insertion issues or dislodgement. For example, microbes (microorganisms including bacteria, viruses, fungi, and parasites) can cause infections; the pH strength of drugs can bum through blood vessels even if the cannula is placed perfectly; vulnerable patients / delicate blood vessels may break / perforate all of which could cause adverse events and / or complications that we can detect with our system. Such events therefore include, but are not limited to, infection, infiltration (leak into the tissue, (medium range pH), extravasation (leaking in the tissue, high or low pH value, more dangerous chemical); phlebitis (inflammation of a vein), or the like as known in the art.

[0020] In a preferred embodiment, said alert system is for detecting incorrect cannula placement and / or dislodgement in a subject.

[0021] As will be appreciated, multiple adhesive pads can be appropriately positioned adjacent or about the insertion point, each one or more pad comprising one or more sensors. Alternative, as is conventionally used to hold a cannula in place, a single adhesive pad, sterile gauze with non-sterile tape or bandage, non-sterile plaster, or transparent dressing is typically employed about the insertion site to attempt to hold in place the cannula. Therefore, according to this alternative embodiment there is therefore provided incorporation of one or more sensors into a single pad, positioned around the cannula, with their precise positioning and configuration allowing detection of dislodgement and / or incorrect placement. In a preferred embodiment, said pad is a dressing, bandage or the like. In yet a further preferred embodiment, said pad(s) comprises an adhesive backing or membrane, such as a strip or the like, with one or more portions for attaching said pad to the skin surface, typically comprising an adhesive coating or compound. Suitable adhesives are known in the art and used routinely in existing medical grade pads used in dressings and include microporous materials, synthetic rubber, acrylate, or silicone pressure sensitive adhesives (PSAs). In yet a further preferred embodiment, said pad(s) are at least partially transparent, or comprise a transparent window, to assist user visualization of the skin surface and / or cannula positioned below. Advantageously, the arrangement of the pad(s) and features of same as disclosed herein allows clear visualization of the cannula window to observe the insertion site.

[0022] Reference herein to “positioned over or about the cannula”, as will be appreciated, refers to placing the pad over the cannula where the cannula pierces the skin surface and into the vessel located beneath. As is known, often with typical use, a cannula is fixed by taping it to the patient's skin or using an adhesive dressing and so, in a preferred embodiment, the pad of the system is used in place of routine fixing means. In this manner, its role as a fixing pad for the cannula also allows it to function as sensing pad. In a preferred embodiment, said pad is positioned over the immediate insertion site, and preferably extends at least over an area 1 -10 cm from the insertion site, and more ideally 1 , 2, 3, 4, 5, 6, 7, 8, 9 or 10 cm and every 0.1 cm therebetween.

[0023] In a preferred embodiment, one or more sensors are integrated into the pad(s) to minimize detachment. Alternatively, said one or more sensors may be detachable, and optionally include a fixing means such as an adhesive layer, which offers the advantage that the sensors can be reused with different pads, for example, on different patients (following sterilization or cleaning) or in the event that the pad or dressing needs to be changed. Accordingly, in this alternative embodiment, said pad(s) comprises one or more marks, labels, or indicators, for determination of the attachment position for one or more sensors.

[0024] In a preferred embodiment, at least one or more sensors comprise or consist of at least one pressure sensor configured to detect a change, most preferably an increase, in pressure. As will be appreciated, such sensors that detect increase in pressure also equivalently detect stretching of the skin surface, such that can commonly occur in cannula adverse events. More preferably, said at least one pressure sensor, associated with said adhesive pad, is positioned in a region distal from the point at which the cannula is inserted into or under the skin of the subject, and about or adjacent the region approximate the position of the end of the cannula under the skin. More preferably, said at least one pressure sensor is positioned approximately along the same longitudinal axis as the cannula when inserted into the skin. In a preferred embodiment, said pressure sensor is positioned approximate the end position of the cannula and up to about 10 cm, more preferably up to 5cm, from the end position of the cannula. It has advantageously been found that when positioned in this location, the sensor is most sensitive to detect pressure changes in the skin surface, in particular swelling, which can provide an early detection of infiltration and leaking of cannula fluid into the tissue surrounding the vessel. In yet a further preferred embodiment, said at least one pressure sensor further comprises a fixing means, such as a dressing or surgical tape, positioned over the at least one pressure sensor whereby in use swelling of the skin surface increases pressure on the pressure sensor, thereby increasing sensitivity and detection thresholds. As will be appreciated by those skilled in the art, numerous pressure sensors, in particular surface pressure sensors, are known in the field that can serve the purpose of detecting swelling of the skin, including but not limited to, a load cell, a resistive pressure sensor, thin film pressure sensor, a capacitive sensor, a piezoelectric sensor, an optical pressure sensor, or Microelectromechanical system (MEMS) sensors.

[0025] Additionally, or alternatively, in yet a further preferred embodiment said at least one sensor comprises or consists of at least one, ideally a plurality, of temperature sensor probes configured to measure the temperature of the skin surface, more preferably a change in the temperature of the skin surface, and most preferably an increase in temperature of the skin surface. In a preferred embodiment, there is provided at least a first temperature sensor probe, associated with at least one adhesive pad, positioned adjacent or about the point at which the cannula is inserted into or under the skin of the subject and / or at least a second temperature sensor probe, associated with at least one adhesive pad, and positioned in a region distal from the point at which the cannula is inserted into or under the skin, most preferably the at least second temperature probe is adjacent a region approximate the position of the end of the cannula under the skin. It has advantageously been found that when positioned in these locations, ideally with a first and second temperature sensor, the temperature sensors are most sensitive to detect temperature changes in the skin surface, in particular an increase, which can provide an early detection of infection and / or extravasation indicating dislodgement or incorrect placement or adverse event. In particular, the first and second temperature sensor are configured such that a relative difference between the first and second sensor represents a local temperature change, indicative of cannula dislodgement or misplacement, or other adverse event associated with cannula function.

[0026] In yet a further preferred embodiment, the system further comprises a control temperature sensor configured to be positioned direct on the skin surface, and away from the pad, to act as control probe to detect baseline body temperature remote from the cannula. In a preferred embodiment, said control temperature sensor is positioned approximately perpendicular to the longitudinal axis of the cannula, more preferably at least 1 cm from the end of the cannula up to about 10 cm from the end of the cannula, and more ideally, 1 cm, 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, or every 0.1 cm therebetween. As will be appreciated, in this manner, the temperature of the one or more temperature sensors associated with the at least one pad can be correlated with the sensor positioned on the skin to more accurately detect a change in temperature of the skin in the region surrounding the cannula. As will be appreciated by those skilled in the art, numerous temperature sensors, in particular surface temperature sensors, are known in the field that can serve the purpose of detecting temperature of the skin, including but not limited to, a resistance temperature sensors that measures changes in voltage and correlates into temperature such as TMP36, resistance based temperature sensors such as thermistors or resistance temperature detectors, optical temperature sensors, thermocouples, or integrated silicon temperature sensors.

[0027] In yet a further additional, or alternative embodiment, said at least one sensor comprises or consists of a mechanical dislodgement sensor and comprises a first part, configured to be attached to the cannula tube, or associated tubing, and a second part associated with the pad, most ideally along the same longitudinal axis as the cannula, and further wherein the first and second parts are in physical and electrical connection with each other and configured such that movement of the first part relative to second part (such as a consequence of the force arising on dislodgement of the cannula) breaks the physical and electrical connection between said first and second parts. As will be appreciated, in this manner, a change in electrical conductivity can be detected, which will indicate dislodgement of the cannula.

[0028] In a preferred embodiment, the first and second part are magnetic sensors such as hall effect sensors, magneto-resistive / inductive sensors, reed switches or opposing magnets. More preferably, said first and second parts are opposing magnets and have a relative magnetic strength, or intensity, of 0.1 -2.5 kg / cm2, more preferably 0.5-1.5 kg / cm2, and more preferably still 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 , 1.2, 1.3, 1.4 or 1.5 kg / cm2More preferably, additionally or alternatively, said first and second part comprise a sensor strip forming an electrical circuit, whereupon dislodgement, the sensor strip is torn breaking the electrical circuit. As will be appreciated, in this manner, a change in electrical conductivity can be detected, which will indicate dislodgement of the cannula. Alternatively, as known in the art, other dislodgement or detachment sensors are equally appropriate. These include: contact-based sensors, that detect direct physical contacts to detect disconnection, such as conductive contacts, pressure sensitive switches, resistive sensors or the like; optical sensors, that use light to detect alignment, such as photo-interrupters, optical sensors, laser distance sensors, or the like; RF-based sensors, such as RFID tags, Bluetooth sensors, ultrawideband sensors, Near field communication, or the like; mechanical sensors, that sense physical changes like movement, such as micro-switches, strain gauges, accelerometers, tactile sensors, or the like.

[0029] In yet a further preferred embodiment, said system further comprises one or more additional sensor types such as, but not limited to, flow sensors, moisture sensors, skin conductance sensors, capacitance sensors, accelerometers, bioimpedance or pH sensors. As will be appreciated, the incorporation of further sensor types can be used to supplement the detection of the primary parameters as defined herein, to further enhance the sensitivity of the system.

[0030] In yet a further preferred embodiment, the system comprises at least one electrical connection or wireless connection by which the sensor(s) receive and transmit an electrical signal and, further, a processor or communication module is provided to process sensing signal(s) from said sensor(s) to generate one or more sensor output signals.

[0031] The processor is adapted to analyse the output signal(s) from said sensor(s) and detect the occurrence of a predetermined change in the signals over time. This sensing may be undertaken either in a continuous monitoring mode or in a point of care mode which involves single or multiple point measurements.

[0032] In yet a further preferred embodiment, said system comprises an information means, display, alert or alarm, relaying to a user, or via a communication module, to a remote station or monitoring device, based on the output signal(s) such that status of the cannula can be determined and, where dislodged or incorrectly placed, or detecting an adverse event, a user is alerted, and appropriate action taken. As will be appreciated, numerous information means or alarm could be utilized, such an audio, visual, optical signal, or the like. This includes visualization and alarms as part of routine hospital monitoring equipment, and also smartphone apps or the like for remote monitoring. Accordingly, the communication module may take the form of numerous data transmission modules as known in the art, such as Bluetooth, radio, or other wireless communication technologies.

[0033] More preferably still, said system comprises an infusion control module, whereupon receiving an output signal correlating with a dislodged or incorrectly placed cannula, or an adverse event, communicates to user, optionally via a display, and / or halts fluid flow through the cannula, preferably through activation of a shut off valve or deactivation of fluid flow, or the like, to cease passage of fluid through the cannula. In this manner, further leak of fluid (relevant in case of expensive therapeutic, or for determining dosing) is prevented.

[0034] In use, as will be apparent, the system provides a simple yet robust alert system, whose careful consideration of key clinical parameters that can arise due to incorrect placement or dislodgement of a cannula, and configuration of the sensors and their position, allows for early detection of a change in one or more of these parameters and to alert a healthcare professional of a potential problem so that appropriate action can be taken. In this manner, downstream complications can be avoided and risk to the patient minimized. As will therefore be appreciated, in a preferred embodiment said sensor system comprises one or more of the different sensor types as disclosed herein according to the one or more parameters to be detected. However, according to a preferred embodiment, for the most accurate and robust alert system, the alert system comprises a combination of at least two and more preferably all of the sensors as disclosed herein to allow multi parameter sensing. According to a second aspect of the invention, there is provided an alert system for detecting cannula dislodgement in a subject, said system comprising: at least one mechanical dislodgement sensor and comprises a first part, configured to be attached to the cannula tube, or associated tubing, and a second part adapted to be attached to the skin surface of the subject, and further wherein the first and second parts are in physical and electrical connection with each other and configured such that movement of the first part relative to second part (such as a consequence of the force arising on dislodgement of the cannula) breaks the physical and electrical connection between said first and second parts. As will be appreciated, in this manner, a change in electrical conductivity can be detected, which will indicate dislodgement of the cannula.

[0035] As will be appreciated, the device according to the second aspect has utility for detecting dislodgement of cannula, including PIVC cannula, central IV, PICC line, IV’s, but also other medical equipment with cannula or catheter lines or with connections from two positions that may involve a patient and a device, such as Electrocardiographs (ECGs). As per the first aspect, the sensor forms part of a system wherein an alert, such as to an app or system, alerts a user of disconnection. Further, ancillary data may be recorded such as the time of disconnection and the patient related number for the staff to be made aware and to log the time of the disconnection. This will alert clinicians, make them aware of the patient involved and the time the disconnection occurred with a counter to show duration of disconnection and if anyone has attended to them. Clinical impact can also be derived for the disconnection time measurement.

[0036] In a preferred embodiment, the first and second part are opposing magnets. More preferably, said first and second parts have a relative magnetic strength, or intensity, of 0.1 -2.5 kg / cm2, more preferably 0.5-1.5 kg / cm2, and more preferably still 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 , 1.2, 1.3, 1 .4 or 1 .5 kg / cm2. More preferably, additionally or alternatively, said first and second part comprise a sensor strip forming an electrical circuit, whereupon dislodgement, the sensor strip is torn breaking the electrical circuit. As will be appreciated, in this manner, a change in electrical conductivity can be detected, which will indicate dislodgement of the cannula.

[0037] In a preferred embodiment of the second aspect, the second part is positioned, in use, on the skin perpendicular to longitudinal axis of the cannula. In this manner the sensor is most sensitive to mechanical dislodgement, and so, separation of the first and second parts.

[0038] According to a third aspect of the invention, there is provided a kit of parts for use as an alert system for detecting incorrect cannula placement and / or dislodgement in a subject, or adverse event in relation to cannula status in a subject, said system comprising: i) at least one pad, adapted for adhering to the skin surface and positioning over, or about, a cannula approximate to the point at which the cannula is inserted into or under the skin of the subject; ii) one or more sensors as disclosed herein, and adapted to be associated with, or associated with, said at least one or more pads and configured to detect one or more parameters selected from: pressure, temperature and / or position or movement of the cannula.

[0039] In a preferred kit, a plurality of pads are provided, preferably each one sized and shaped for use on different parts of the body according to the cannula to be utilized therewith.

[0040] In yet a further preferred kit, said pad(s) comprises one or more marks, labels, or indicators, for determination of the attachment position for one or more sensors.

[0041] In yet a further preferred embodiment, said kit further comprises at least one electrical connection for attaching to the pad and / or sensors by which the sensor(s) receive and transmit an electrical signal and, further, a processor and / or communication module is provided to process sensing signal(s) from said sensor(s) to generate one or more sensor output signals.

[0042] The processor is adapted to analyse the output signal(s) and detect the occurrence of a predetermined change in the signal(s) over time. This sensing may be undertaken either in a continuous monitoring mode or in a point of care mode which involves single or multiple point measurements.

[0043] In yet a further preferred embodiment, said kit comprises an information means, alert or alarm, relaying to a user, or via a communication module, to a remote station or monitoring device, based on the output signal(s) such that status of the cannula can be determined and, where dislodged or incorrectly placed, a user alerted and appropriate action taken.

[0044] More preferably still, said kit comprises an infusion control module, whereupon receiving an output signal correlating with a dislodged or incorrectly placed cannula, or an adverse event, halts fluid flow through the cannula, preferably through activation of a shut off valve or deactivation of fluid flow, or the like, to cease passage of fluid through the cannula. In this manner, further leak of fluid (relevant in case of expensive therapeutic, or for determining dosing) is prevented and further harm to the patient.

[0045] In a preferred embodiment, said kit is for detecting incorrect cannula placement and / or dislodgement in a subject.

[0046] According to a fourth aspect of the invention, there is provided a method for detecting incorrect placement and / or dislodgement, or adverse subject event in relation to cannula status in a subject, of a cannula inserted in a subject, said method comprising: i) providing an alert system comprising: at least one pad, adapted for adhering to the skin surface and positioning over, or about, a cannula approximate to the point at which the cannula is inserted into or under the skin of the subject; and one or more sensors as disclosed herein and associated with said at least one or more pads and configured to detect one or more parameters selected from: pressure, temperature and / or position or movement of the cannula; ii) positioning on the subject at least one pad, over, or about, the cannula approximate to the point at which the cannula is inserted into or under the skin of the subject; iii) detecting, via said sensors, the pressure, temperature and / or position or movement of the cannula, or status of the cannula, whereupon wherein said detected change exceeds a predetermined threshold alerting a user that said cannula is displaced / dislodged or an adverse event has occurred.

[0047] In a preferred method, the detecting according to step iii) optionally comprises sensing, via said sensors, the pressure, temperature and / or position or movement of the cannula, to generate at least one sensing signal from the sensor(s). Yet more preferably, said sensing signal(s) are processed, via a processor, to generate one or more sensor output signals optionally via a communication module.

[0048] In yet a further preferred method, the processor is adapted to detect the occurrence of a predetermined change in the signal(s) over time whereupon wherein said detected change exceeds a pre-determined threshold alerting a user that said cannula is displaced / dislodged. Therefore, accordingly, said method further comprises outputting an alert, or alarm, optionally via a display or information means, to a user.

[0049] In yet a further preferred method, said method further comprises the optional step of cessation of flow of fluid in the cannula on output of an alert, optionally via an infusion control module. As will be appreciated, in this manner, any fluid flow can be stopped, thereby preventing further adverse event, injury, leakage, until the issue is resolved.

[0050] In a preferred embodiment, said method is for detecting incorrect cannula placement and / or dislodgement in a subject.

[0051] Preferred features of each aspect of the invention may be as described in connection with any of the other aspects.

[0052] 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 do not exclude other moieties, additives, components, integers or steps. 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.

[0053] All references, including any patent or patent application, cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. Further, no admission is made that any of the prior art constitutes part of the common general knowledge in the art.

[0054] Other features of the present invention will become apparent from the following examples. Generally speaking, the invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including the accompanying claims and drawings). Thus, features, integers, characteristics, compounds or chemical moieties 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.

[0055] Moreover, unless stated otherwise, any feature disclosed herein may be replaced by an alternative feature serving the same or a similar purpose. The Invention will now be described by way of example only with reference to the Examples below and to the following Figure wherein:

[0056] Figure 1. Shows a cross-sectional perspective view of the alert system according to the invention when in use positioned over a cannula inserted into the skin surface.

[0057] Figure 2. Shows a plan view of the alert system according to the invention visualising approximal sensor / device system locations and adhesive zone for the system in relation to cannula and dressing, and in particular when in wired (figure 2A) or wireless communication (figure 2B) with a communication module.

[0058] Figure 3. Shows a plan view of a variation of the detachment sensor according to a preferred embodiment of the invention, in particular comprising two detachable parts D1 and D2. Left the sensor is shown closed, and so with a complete circuit, and right when separated and so the circuit is broken. .

[0059] Figure 4. Shows a detailed view of a pressure sensor according to a preferred embodiment of the invention that reacts through changes in resistance to swelling and / or pressure. This may identify gradients of sweeling / pressure change.

[0060] Figure 5. Shows a detailed plan view of the temperature sensor according to a preferred embodiment of the invention with (fig 5a) and without (fig 5b) the cannula, and in particular the relative positioning in relation to each temperature probe. A first temperature probe B1 is positioned approximate the insertion point of the cannula into the skin, a second temperature probe positioned approximate the end of the cannula needle when inserted, and a third optional probe B3 is positioned on the skin surface, ideally perpendicular to the first probe. Collectively, in this shown embodiment, the three probes are approximately in a triangulated position with respect to one another. Figure 5c shows a side sectional view of the temperature sensor according to the invention, along with the cannula when inserted into the skin.

[0061] Figure 6. Shows a flow diagram of the collected data, data analysis, data communication and alerting pathway via wired or wireless transfer of data / information in a preferred system of the invention.

[0062] Figure 7 Shows a plan (fig. 7a) and side section (fig. 7b) view of the alert system comprising a cannula when inserted into a patient. As is shown the temperature sensor B2 is placed approximal to the end of the cannula within the blood vessel.

[0063] Referring the figures, specifically figure 1 , there is shown a cross-sectional perspective plan view of an alert system according to the invention, when in use and positioned over a cannula

[0001] , As is typical, the cannula

[0001] may comprise a trocar, or needle [1 a] that is inserted beneath the skin with the aim to deliver and position within a blood vessel located beneath the skin surface. Typically, such cannula may also comprise a valve member [1 b] for stopping and starting flow of fluid within the cannula.

[0064] As disclosed herein, the alert system comprises one or more sensor pads [2] associated with one of more sensors [3, 4, 5], The pad [2] is sterile and may be made from numerous routine surgical materials, tape, gauze or the like. As will also be appreciated, given the purpose of the pad [2] is to position at least one or more sensors [3, 4, 5] , the pad(s) comprise an adhesive backing, such as a strip or the like, with one or more portions for attaching said pad to the skin surface, typically in the form of an adhesive coating. Suitable adhesives are known in the art and include synthetic rubber, acrylate, or silicone pressure sensitive adhesives (PSAs).

[0065] For the purpose of positioning the sensor [3, 4, 5] in the preferred position relative to the cannula

[0001] , via the pad [2], said sensor [3, 4, 5] may be integrated into the pad to minimize detachment. Alternatively, said one or more sensors [3, 4, 5] may be detachable, which offers the advantage that the sensors can be reused with different pads, for example, on different patients (following sterilization) or in the event that the pad or dressing needs to be changed. In the case of detachable sensor(s), it is envisaged that said pad(s) comprises one or more marks, labels, or indicators, for healthcare users to determine the attachment position for one or more sensors [3, 4, 5],

[0066] Turning to the sensor themselves, the premise of the system disclosed herein is the sensing, and so detection, of one or more clinical parameters of importance that can be used to indicate cannula [1] dislodgement or misplacement, or other adverse events, namely through detection of pressure, temperature and / or mechanical dislodgement.

[0067] To this end, according to one preferred arrangement, the sensor may take the form of a pressure sensor [4], Although not shown, in preference, surface pressure sensors are preferred and serve the purpose of detecting swelling of the skin. As will be appreciated, the incorporation of a pressure sensor permits one to detect a change, most preferably an increase, in pressure. This, it has been found, is particularly relevant to allow detection of swelling of the skin surface, which can provide an early detection of infiltration and leaking of cannula fluid into the tissue surrounding the vessel, arising from cannula misplacement or dislodgement or adverse event. As is shown, in preferred arrangements at least one pressure sensor [4] is positioned in a region distal from the point at which the cannula is inserted into or under the skin of the subject, and about or adjacent the region approximate the position of the end of the cannula under the skin [C]. As will be appreciated, especially when positioned approximately along the same longitudinal axis as the cannula when inserted into the skin, early detection of infiltration, and so swelling, can be detected. It has advantageously been found that when positioned in this location, the sensor is most sensitive to detect pressure changes in the skin surface, In yet a further preferred embodiment, said at least one pressure sensor further comprises a fixing means, such as a dressing or surgical tape, positioned over the at least one pressure sensor whereby in use swelling of the skin surface increases pressure on the pressure sensor, thereby increasing sensitivity and detection thresholds. As will be appreciated by those skilled in the art, numerous pressure sensors, in particular surface pressure sensors, are known in the field that can serve the purpose of detecting swelling of the skin, including but not limited to, a load cell, a resistive pressure sensor, thin film pressure sensor, a capacitive sensor, a piezoelectric sensor, an optical pressure sensor, or MEMS sensors. Such a sensor is shown in figure 4.

[0068] Resistive pressure sensors utilise the change in electrical resistance of a strain gauge bonded to the diaphragm that’s exposed to the pressure medium. The strain gauges often comprise a metal resistive element on a flexible backing bonded to the diaphragm or deposited directly using thin-film processes. The metal diaphragm gives high over-pressure and burst-pressure capability. Otherwise, strain gauges can be deposited on a ceramic diaphragm using a thick-film deposition process. Over-pressure and burst-pressure tolerance are typically much lower than for metal-diaphragm devices.

[0069] Piezoresistive sensors take advantage of the change in resistivity of semiconductor materials, when subjected to strain due to diaphragm deflection. The magnitude of the change can be 100 times greater than the resistance change produced in a metal strain gauge. Hence piezoresistive sensors can measure smaller pressure changes than metal or ceramic sensors.

[0070] Capacitive sensors, which display a capacitance change as one plate deflects under applied pressure, can be highly sensitive, can measure pressures below 10 mbar, and withstand large overloads.

[0071] Piezoelectric pressure sensors utilise the property of piezoelectric materials like quartz, to generate a charge on the surface when pressure is applied. The charge magnitude is proportional to the force applied, and the polarity expresses its direction. The charge accumulates and dissipates quickly as pressure changes, allowing measurement of fast-changing dynamic pressures.

[0072] Optical sensors, which utilise interferometry to measure pressure-induced changes in optical fibre, are undisturbed by electromagnetic interference, allowing use in noisy environments or near sources such as radiography equipment. They can be created using tiny components or MEMS technology, can be medically safe for implantation or topical use, and can measure the pressure at multiple points along the fibre.

[0073] MEMS (Micro Electro-Mechanical System) sensors contain a piezo or capacitive pressure-sensing mechanism fabricated on silicon at micron-level resolution. Co-packaged signal-conditioning electronics convert the smallmagnitude MEMS electrical output to an analogue or digital signal. They are tiny surface-mount devices typically only about 2-3mm per side.

[0074] Referring back to figure 1 , as shown, also in addition (although it is equally conceived that a single sensor type is also encompassed), the alert system may comprise a temperature sensor or temperature sensor probe [3], most ideally a plurality of such sensors. Numerous temperature sensors, in particular surface temperature sensors, are plausible, the purpose of which is detecting temperature of the skin, including but not limited to, a resistance temperature sensor such as TMP36, resistance-based temperature sensors such as thermistors or resistance temperature detectors, optical temperature sensors, thermocouples, or integrated silicon temperature sensors.

[0075] The TMP36 is an example of an analogue temperature sensor that measures temperature by translating changes in voltage into temperature readings. Thermistors are temperature-sensitive resistors made of ceramic materials, such as metal oxides, which exhibit a significant change in resistance as a function of temperature. There are two types of thermistors: Negative Temperature Coefficient (NTC) and Positive Temperature Coefficient (PTC). NTC thermistors have a resistance that decreases as temperature increases, while PTC thermistors have a resistance that increases with temperature. When used to measure human skin temperature, thermistors can be placed in contact with the skin, and the change in resistance can be converted into a temperature value using a calibration curve. Resistance Temperature Detectors (RTDs): RTDs are precise temperature sensors made of pure material, typically platinum, nickel, or copper. As temperature increases, the resistance of the material increases in a linear and predictable manner. RTDs can be used for measuring skin temperature by placing them in contact with the skin and measuring the change in resistance. Optical temperature sensors, such Infrared (IR) thermometers: These are non-contact temperature sensors that measure the thermal radiation emitted by an object, such as human skin, in the infrared spectrum. The radiation is focused onto a detector, which converts it into an electrical signal proportional to the temperature. IR thermometers are commonly used to measure forehead temperature, providing a quick and non-invasive way to assess human body temperature. Thermocouples are temperature sensors are made of two dissimilar metals joined together at one end to create a junction. When the junction is heated or cooled, a voltage is generated proportional to the temperature difference between the junction and the other end of the metals. This voltage can be measured and converted into a temperature value. While thermocouples are not as precise as other methods, they can be used for measuring skin temperature. Lastly, integrated Silicon Temperature Sensors, like the TMP36, are based on the temperature-dependent properties of silicon. They produce a voltage output that varies linearly with temperature, allowing for easy conversion to temperature values.

[0076] In this manner, a change in temperature, and in particular an increase, can be detected and can provide an early detection of infection and / or extravasation indicating an adverse event, dislodgement or incorrect placement. As depicted, preferably a plurality of temperature sensors is included; in this manner, relative differences between temperature sensors, including between different regions of the associated pad, can be determined to detect a regional temperature difference. In a preferred arrangement, there is provided at least a first temperature sensor probe, in a region positioned adjacent or about the point at which the cannula is inserted into or under the skin of the subject [B1 ] and at least a second temperature sensor probe positioned in a region distal from the point at which the cannula is inserted into or under the skin [B2], It has advantageously been found that when positioned in these locations, ideally with a first and second temperature sensor, the temperature sensors are most sensitive to detect temperature changes across the skin surface. In particular, the first and second temperature sensor are configured such that a relative difference between the first and second sensor represents a local temperature change, indicative of cannula dislodgement or misplacement. Although not exclusively required, a third temperature sensor [B3] may be included and intended to be placed direct onto the skin surface, thereby service as a control temperature probe to detect baseline body temperature remote from the cannula. In a preferred embodiment, said control temperature sensor is positioned approximately perpendicular to the longitudinal axis of the cannula, more preferably at least 1 cm from the end of the cannula up to about 10 cm from the end of the cannula, and more ideally, 1 cm, 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, or every 0.1 cm therebetween. The relative position of temperature sensors according to a preferred embodiment can also be seen in figure 5a / b, and also when the associated cannula inserted into the skin and into a vein as in figure 5c.

[0077] Further still, in an alternative or additional embodiment, referring back to figure 1 , said system may include at least one sensor acting as a mechanical dislodgement sensor, to detect physical dislodgement of the cannula from its position, for example, should the cannula be accidentally pulled or removed from position. In a preferred arrangement, as shown, the mechanical sensor comprises a first part [D1 ], configured to be attached to the cannula tube and a second part [D2] associated with the pad, as shown in figure 3, most ideally along the same longitudinal axis as the cannula, or alternatively positioned on the skin surface as shown most ideally perpendicular to the longitudinal axis of the cannula. In these arrangements, the first and second parts are in physical and electrical connection with each other and configured such that movement of the first part relative to second part (such as a consequence of the force arising on dislodgement of the cannula) breaks the physical and electrical connection. As will be appreciated, in this manner, a change in electrical conductivity can be detected, which will indicate dislodgement of the cannula. More preferably (though not shown), additionally or alternatively, said first and second part comprise a sensor strip forming an electrical circuit, whereupon dislodgement, the sensor strip is tom breaking the electrical circuit. As will be appreciated, in this manner, a change in electrical conductivity can be detected, which will indicate dislodgement of the cannula. In these arrangements, the system is able to detect when the cannula is removed / dislodged.

[0078] With reference to figure 2a, as will be appreciated by the skilled person, the sensors include at least one electrical connection, or wires [6], by which the sensor(s) receive and transmit an electrical signal and, further, a processor or communication module [7] is provided to process sensing signal(s) from said sensor(s) to generate one or more sensor output signals. Alternatively, communication of signals from the sensors to the processor or communication module may be wireless as shown in figure 2b. The processor is adapted to analyse the output signal(s) and detect the occurrence of a predetermined change in the signals over time. This sensing may be undertaken either in a continuous monitoring mode or in a point of care mode which involves single or multiple point measurements. Ideally, information is relayed to a healthcare professional by means of a visual display, audio alert or the like, including remote means such as smartphones or monitor systems such that status of the cannula can be determined and, where dislodged or incorrectly placed, a user alerted, and appropriate action taken. In such embodiments, said system will include conventional communication means for relaying the signal, such as Bluetooth, radio, or other wireless communication technologies. Further still, in preferred embodiments, the alert system may also comprise an infusion control module (not shown), whereupon receiving an output signal correlating with a dislodged or incorrectly placed cannula, or an adverse event, activates a shut off valve, or the like, or deactivates fluid flow to cease passage of fluid through the cannula. In this manner, further leak of fluid (relevant in case of expensive therapeutic, or for determining dosing) is prevented. As shown, each sensor is ideally positioned in particular regions of the pad, relative to one another and the cannula. In use, as will be apparent, the system provides a simple yet robust alert system, whose careful consideration of key clinical parameters that can arise due to incorrect placement or dislodgement of a cannula, and configuration of the sensors and their position, allows for early detection of a change in one or more of these parameters and to alert a healthcare professional of a potential problem so that appropriate action can be taken. In this manner, downstream complications can be avoided and risk to the patient minimized. As will therefore be appreciated, in a preferred embodiment said sensor system comprises one or more of the different sensor types as disclosed herein according to the one or more parameters to be detected. However, as shown, for the most accurate and robust alert system, the alert system comprises a combination of the sensors as disclosed herein to allow multi parameter or multi modal sensing.

Claims

CLAIMS1. An alert system for detecting incorrect cannula placement and / or dislodgement in a subject, or adverse subject event in relation to cannula status in a subject, said system comprising: i) at least one pad, adapted for adhering to the skin surface and positioning over, or about, a cannula approximate the point at which the cannula is inserted into or under the skin of the subject; and ii) at least one or more sensors associated with said at least one or more pads and configured to detect at least temperature, wherein at least one or more sensors comprise or consist of at least one, and ideally a plurality of, temperature sensor probes configured to measure the temperature of the skin surface, and further wherein there is provided at least a first temperature sensor probe, associated with at least one adhesive pad, positioned adjacent or about the point at which the cannula is inserted into or under the skin of the subject and / or at least a second temperature sensor probe, associated with at least one adhesive pad, and positioned in a region distal from the point at which the cannula is inserted into or under the skin.

2. The alert system according to claim 1 wherein said at least one pad comprises an adhesive backing or membrane, optionally with one or more portions for attaching said at least one pad to the skin surface.

3. The alert system according to any preceding claim wherein said pad is positioned over the immediate insertion site, optionally extending at least over an area 1 -10 cm from the insertion site.

4. The alert system according to any preceding claim wherein said one or more sensors are detachable from said pad or integrated into said pad.

5. The alert system according to any preceding claim wherein at least one or more sensors further comprises or consists of at least one pressure sensor configured to detect a change in pressure.

6. The alert system according to claim 5 wherein said at least one pressure sensor, associated with said adhesive pad, is positioned in a region distal from the point at which the cannula is inserted into or under the skin of the subject, and about or adjacent the region approximate to the position of the end of the cannula under the skin.

7. The alert system according to claim 5 or 6 wherein said at least one pressure sensor is positioned approximately along the same longitudinal axis as the cannula when inserted into the skin.

8. The alert system according to any one of claims 5-7 wherein said at least one pressure sensor further comprises a fixing means, optionally a dressing or surgical tape, positioned over the at least one pressure sensor.

9. The alert system according to any one of claims 5-8 wherein said pressure sensor is a a load cell, a resistive pressure sensor, thin film pressure sensor, a capacitive sensor, a piezoelectric sensor, an optical pressure sensor, or MEMS sensor.

10. The alert system according to any one of claims 1 -9 wherein the at least second temperature probe is adjacent a region approximate to the position of the end of the cannula under the skin.11 . The alert system according to any one of claims 1 -10 wherein the first and second temperature sensor are configured such that a relative difference between the first and second sensor represents a local temperature change.

12. The alert system according to any one of claims 1 -11 wherein the system further comprises a control temperature sensor configured to be positioned direct on the skin surface.

13. The alert system according to claim 12 wherein the control temperature sensors is positioned approximately perpendicular to the longitudinal axis of the cannula, optionally at least 1 cm from the end of the cannula up to about 10 cm from the end of the cannula.

14. The alert system according to any one of claims 1 -13 wherein said temperature sensors are TMP36, resistance based temperature sensors such as thermistors or resistance temperature detectors, optical temperature sensors, thermocouples, or integrated silicon temperature sensors.

15. The alert system according to any preceding claim further comprising or consisting of a mechanical dislodgement sensor and comprises a first part, configured to be attached to the cannula tube, or associated tubing, and a second part associated with the pad, and further wherein the first and second parts are in physical and electrical connection with each other and configured such that movement of the first part relative to second part breaks the physical and electrical connection between said first and second parts.

16. The alert system according to claim 15 wherein are magnetic sensors, contact based sensors, optical sensors, RF-based sensors, mechanical sensors.

17. The alert system according to claim 14 wherein the first and second parts are opposing magnets, optionally wherein said first and second parts have a relative magnetic strength, or intensity, of 0.1 -2.5 kg / cm2.

18. The alert system according to any one of claims 15-17 wherein said first and second part comprise a sensor strip forming an electrical circuit,whereupon dislodgement, the sensor strip is torn breaking the electrical circuit.

19. The alert system according to any preceding claim wherein said system further comprises one or more of: i) at least one electrical connection by which the sensor(s) receive and transmit an electrical signal; and / or ii) a processor to process sensing signal(s) from said sensor(s) to generate one or more sensor output signals; and / or iii) a communication module for transmitting one or more sensor output signals; and / or iv) an information means, display, alert or alarm.

20. A method for detecting incorrect placement and / or dislodgement of a cannula inserted in a subject, or adverse subject event in relation to cannula status in a subject, said method comprising: i) providing an alert system as disclosed in any one of claims 1 -19; ii) positioning on the subject at least one pad, over, or about, the cannula approximate to the point at which the cannula is inserted into or under the skin of the subject; iii) detecting, via said sensors, the pressure, temperature and / or position or movement of the cannula, whereupon wherein said detected change exceeds a pre-determined threshold alerting a user that said cannula is displaced / dislodged.

21. The method according to claim 20 wherein the detecting according to step iii) optionally comprises sensing, via said sensors, the pressure, temperature and / or position or movement of the cannula, to generate at least one sensing signal from the sensor(s).

22. The method according to claim 21 wherein said sensing signal(s) are processed, via a processor, to generate one or more sensor output signals optionally via a communication module.

23. The method according to claim 22 wherein the processor is adapted to detect the occurrence of a predetermined change in the signal(s) over time whereupon wherein said detected change exceeds a predetermined threshold alerting a user that said cannula is displaced / dislodged.

24. The method according to any one of claims 20-24 wherein said method further comprises the optional step of cessation of flow of fluid in the cannula on output of an alert.

25. A kit of parts for use as an alert system for detecting incorrect cannula placement and / or dislodgement in a subject, or adverse subject event in relation to cannula status in a subject, said system comprising: i) at least one pad, adapted for adhering to the skin surface and positioning over, or about, a cannula approximate the point at which the cannula is inserted into or under the skin of the subject; ii) one or more sensors as disclosed herein, and adapted to be associated with, or associated with, said at least one or more pads and configured to detect one or more parameters selected from: pressure, temperature and / or position or movement of the cannula.

26. The kit according to claim 25 wherein a plurality of pads are provided, preferably each one sized and shaped for use on different parts of the body according to the cannula to be utilized therewith.

27. The kit according to claims 25 or 25 wherein, said pad(s) comprises one or more marks, labels, or indicators, for determination of the attachment position for one or more sensors.

28. The kit according to claims 25-27 comprising at least one wireless connection or electrical connection for attaching to the pad and / or sensors by which the sensor(s) receive and transmit an electrical signal and, further, a processor is provided to process sensing signal(s) from said sensor(s) to generate one or more sensor output signals.

29. The kit according to claim 28 wherein the processor is adapted to analyse the output signal(s) and detect the occurrence of a predetermined change in the signal(s) over time. This sensing may be undertaken either in a continuous monitoring mode or in a point of care mode which involves single or multiple point measurements.

30. The kit according to any one of claims 25-29 wherein the kit comprises an information means, alert or alarm, relaying to a user, or via a communication module, to a remote station or monitoring device, based on the output signal(s) such that status of the cannula can be determined and, where dislodged or incorrectly placed, a user alerted and appropriate action taken.

Images