Description

The invention relates to an extravasation detection device according to claim 1 , and to a method of detecting an extravasation according to claim 14.

Extravasation detection devices typically employ a cuff comprising an elastic material. The cuff is typically adapted to be worn around a limb of a patient and is adapted to deform to accommodate for changes in the size of the limb.

The term “Extravasation” is commonly used in the medical field to refer to an accidental infusion or leakage of an injection fluid such as a therapeutic agent or a contrast medium into tissue surrounding a blood vessel rather than to an infusion into the blood vessel itself. Extravasation can cause serious injury to patients. For example, an accidental infusion of a cytostatic agent administered to stop the growth of cancer cells in normal tissue will damage the normal tissue and cause adverse effects including cell cycle arrest, senescence, mitotic catastrophe, and inflammatory responses and fibrosis at the tissue level.

When injecting a fluid, extravasation is often caused by rupture or dissection of fragile vasculature, inappropriate needle placement, or patient movement resulting in the infusing needle being pulled from the intended vessel or causing the needle to be pushed through the wall of the vessel. Furthermore, high rates of injection pressure can further increase the extravasation risk.

It is, therefore, important when performing fluid injections to detect extravasation as soon as possible after it occurs, ideally while it is still occurring, and to immediately discontinue the injection upon a corresponding detection. For example, EP 2 012 670 A2 describes a device to detect extravasation of a contrast medium from a patient during a medical injection procedure. The device can be attached to the patient's hand or other injection site. When extravasation begins to occur, a swelling starts to form on the patient near the injection site. For detecting the swelling, the extravasation detection device comprises a force sensor that is encased in a plastic housing with a sensor load platform that is exposed to atmosphere and enclosed in a flexible rubber housing.

Unfortunately, employing a device comprising rigid components such as a force sensor encased in a plastic housing is uncomfortable to wear for the patient. Also, rigid components may exert further pressure on the swelling caused by the extravasation, and hence can cause further damage.

It is an object of the invention to provide an extravasation detection device that is comfortable to wear, that accurately detects an extravasation, and that is simple to manufacture.

This object is achieved by means of an extravasation detection device comprising the features of claim 1 .

Accordingly, the device comprises: a cuff comprising an elastic material adapted to be worn around a limb of a patient, wherein the cuff is adapted to deform to accommodate changes in the size of the limb, and at least one measuring means connected to a section of the elastic material and adapted to deform with the section of the elastic material to detect an expansion of the section of the elastic material.

The cuff can be an encircling strip or bracelet-like band of elastic material worn around the limb of the patient and can have the shape of a Tourniquet. Also, the cuff can be made from a single-piece of elastic material forming a seamless loop, or can have two end sections on opposite ends of a strip of elastic material that can be removably joined together. The limb of the patient can be the patient’s head, arm, leg, or other portions of the patient’s body. Herein, the term “limb” can be substituted with the term “extremity”. The cuff can fit tightly around the limb and can be in contact with the skin of the patient so that a swelling of the limp caused by an extravasation causes an elastic deformation of the cuff, wherein the circumference of the cuff can increase with the swelling.

The measuring means can be adhesively attached to a section of the elastic material or can be enclosed by the elastic material, for example by casting the elastic material around the measuring means. The measuring means is adapted to deform by a same or similar degree as the section of the elastic material it is attached to. Deformation can take place in at least one degree of freedom. The measuring means can be adapted to change an intrinsic property, such as an electrical resistance, for deducing the degree of deformation by monitoring the change in value of the intrinsic property, such as the resistance value, over time. The section of the elastic material can essentially correspond to the outer geometry of the measuring means, for example to an area of the elastic material the measuring means is in contact with.

Since the measuring means can deform by a same or similar degree as the section of the elastic material it is attached to, the utilization of rigid components can be avoided making wearing it more comfortable for the patient while receiving an infusion. Advantageously, there is a continuous contact zone between a surface of the cuff and the skin of the patient. Also, the device can be advantageously manufactured in a straightforward manner, for example in a single-stage casting process.

In an example, the elastic material comprises a silicone material, a rubber material, or a stretchable fabric material.

For example, the cuff can have a rectangular or circular cross-section. The cuff can be shaped from cheap and readily available elastic material such as silicone or rubber using a moulding process in a variety of sizes and colours. Alternatively, the cuff can be realized with an elastic fabric material, such as for example a spandex material.

In an example, the extravasation detection comprises at least one further measuring means connected to a further section of the elastic material and adapted to deform with the further section of the elastic material to detect an expansion of the further section of the elastic material.

The further measuring means can be identical or similar to the measuring means and can be arranged, in a circumferential direction of the cuff, opposite to the measuring means on a further section of the elastic material. Alternatively, the further measuring means can be arranged, in a circumferential direction of the cuff, near the measuring means and separated from the measuring means by a predetermined space. The cuff can then be arranged on the limb of the patient so that the measuring means are located on either side of the infusions site, i.e. left and right from the infusion site. For example, position markers can be arranged on the material of the cuff, e.g. printed on the material of the cuff, so that the measuring means can be accurately arranged around the infusion site.

Advantageously, by employing two measuring means on a single cuff an extravasation can be detected more accurately.

In an example the extravasation detection device comprises a plurality of further measuring means connected to respective further sections of the elastic material and which are adapted to deform with the further sections of the elastic material to detect an expansion of the further sections of the elastic material.

Advantageously, by employing a plurality of measuring means on the cuffs an extravasation can be detected even more accurately. Also, when employing a plurality of measuring means, e.g. more than 4 measuring means, the utilization of position markers, as described above, to enable medical staff to accurately place the cuff on the patient’s limb can be made redundant.

In an example, the measuring means comprises at least one strain gauge, in particular a resistive foil strain gauge, a fiber optic Bragg sensor, and/or a piezoelectric sensor.

Advantageously, the above-mentioned sensors offer high measurement sensitivity and precision, allow measurement over a wide measurement range, have a small form factor, are light weight, and are inexpensive.

In an example, the measuring means is at least partly, in particularly fully, embedded in the elastic material.

The term “embedded” can be used to refer to a situation where the measuring means is enclosed or encapsuled by the elastic material. For example, the measuring means can be arranged between two layers of the elastic material. Advantageously, the same expansion characteristic can be achieved for the elastic material and the measuring means making detection of an extravasation yet more accurate. In an example, the extravasation device comprises a processing means coupled to the measuring means which is adapted to: compare the detected expansion to at least one threshold value at subsequent time instances, and trigger an alarm event if the detected expansion exceeds the threshold value at one or at a predefined number of subsequent time instances.

The processing means can be realized as a processor that obtains in regular time instances data samples, for example resistance values, from the measuring means and stores the data samples in an associated memory. The resistance values can be equivalent to a certain degree of deformation caused by a swelling of the patient’s limb. The threshold value can be a predetermined parameter indicating the occurrence of an extravasation. Here, the threshold value can be a fixed value, or can be determined as a certain deviation of an intrinsic property of the measuring means. For example, if strain gauges are used as measuring means a change in their intrinsic electric resistance value can be seen as a deviation of an intrinsic property, i.e. deviation from the electric resistance value of the strain gauge before the infusion starts. Advantageously, to achieve a high detection reliability for all patients, the initial resistance value can be used as a start value and a value reflecting an error margin can be added to the start value to obtain the threshold value. The error margin can be a certain percentage of the start value that is added to the start value to avoid false alarms.

Alternatively, or in addition to connecting the measuring means to the processing means, the measuring means can be also connected to each other in one example.

By continuously comparing the obtained data samples with threshold values, an alarm event can be triggered more reliably. Also, by not immediately triggering an alarm event when the detected expansion exceeds the threshold at one single time instance, but instead triggering the alarm event when the detected expansion exceeds the threshold value for a number of subsequent time instances, i.e. for a certain time period, prevents triggering false alarm events, which could be otherwise trigged by patient movement, muscle relaxation/tension or the like.

In an example, the processing means is adapted to provide the alarm event to an associated device, in particular to an infusion pump for infusing fluids into the patient. Advantageously, the processing means can be directly connected to an infusion pump and can immediately, i.e. after the alarm event was triggered, provide the alarm event to the infusion pump, so that the infusion can stop infusing fluid into the patient to not cause any further damage to the patient.

In an example, the extravasation detection device comprises an alarm means coupled to the processing means and comprises an acoustic element and/or an optical element adapted to output an alarm based on receiving the alarm event from the processing means.

The processing means and the alarm means can be both realized as one single component or as separate components that are connected to each other. The acoustic element can be, for example, realized as an acoustic element generating a buzzing noise and can be adapted to produce a clearly noticeable sound upon an alarm event is being triggered to notify medical staff that an extravasation has occurred I is presently occurring. Alternatively, or in addition to the acoustic element, the alarm means can also comprise an optical element, such as for example at least one display or a light emitting diode, LED, to optically indicate the occurrence of the alarm event to the medical staff. In an example, the optical element can comprise a plurality of LED’s that can all have a same colour or can have different colours to indicate the severity of the extravasation, i.e. the detected swelling. For example, depending on the number of subsequent time instances the threshold value is surpassed and/or by how far the detected expansion exceeds the threshold value, LED’s may subsequently light up to indicate the build-up of an extravasation. For example, the following colour scheme can be employed to indicate the build-up of an extravasation:

1. Green (ok): threshold value not exceeded I not close to exceed threshold value for certain number of time instances;

2. Yellow (intermediate): close to exceeding threshold value for certain number of time instances or threshold value is exceeded for short time;

3. Red (alarm): threshold value is exceeded for certain number of time instances.

Advantageously, by informing the patient and/or medical staff early during an intermediate state that there is a risk of an extravasation to occur, the patient can be sensibilized to hold still, etc. In the latter case, the status might go back from the intermediate to the ok status, i.e. in case the threshold value is no longer exceeded. Therefore, the device is not only able to detect an extravasation but also to prevent the occurrence of an extravasation. Advantageously, by employing an alarm means as described herein, an alarm event can be reliably provided to the medical staff.

In an example, the processing means, and the alarm means are arranged on the circumference of the cuff.

For example, the processing means and the alarm means can be realized on a printed circuit board, PCB, comprised within a housing that is arranged on the circumference of the cuff. Alternatively, the processing means and the alarm means can be also comprised, at least partly, within the elastic material of the cuff.

Advantageously, by arranging the processing means and the alarm means on the circumference of the cuff, no further components need to be employed for indicating an alarm event and the alarm event is indicated on the location where the extravasation occurs.

In an example, the extravasation detection device comprises power means, in particular a battery.

Advantageously, no external power source is necessary if the extravasation device comprises a power means.

In an example, the measuring means comprises a scale arranged, in particular printed, at least partially on the circumference of the cuff.

For example, the scale may have a number of evenly spaced markings. In an example the spacing between two markings is 1 mm and a value in cm or inch is given every 10 markings.

Advantageously, by means of the scale the occurrence of an extravasation can even be detected in case of a malfunction of one of the electronic components of the extravasation detection device, or can be used instead of employing electronic components for extravasation detection.

In an example, the cuff comprising two end sections, a buckle to join the end sections, and quick release means for unbuckling the end sections. Advantageously, a corresponding cuff can be quickly placed around the patient’s limb and can be adjusted to accommodate different limbs / differently sized limbs.

The invention also relates to method of detecting an extravasation, the method comprising the steps of: arranging a cuff comprising an elastic material around a limb of a patient, wherein the cuff is adapted to deform to accommodate changes in the size of the limb, and detecting, by at least one measuring means connected to a section of the elastic material and adapted to deform with the section of the elastic material, an expansion of the section of the elastic material.

The method can be conducted using an extravasation detection device as described herein. The cuff and measuring means described herein can be components of the herein described extravasation device. Also, the extravasation device used by the method can employ some or all components of the extravasation device described herein.

In an example, the method further comprises the steps of: comparing, by a processing means, the detected expansion to at least one threshold value at subsequent time instances, and triggering, by the processing means, an alarm event if the detected expansion exceeds the threshold value at one or at a predefined number of subsequent time instances.

The idea underlying the invention shall subsequently be described in more detail by referring to the embodiments shown in the figures. Herein:

Fig. 1 shows a schematic drawing of an extravasation detection device according to an embodiment of the invention;

Fig. 2 shows a schematic drawing of an extravasation detection device according to another embodiment of the invention; and

Fig. 3 shows a method flow according to an embodiment of the invention.

Figure 1 shows a schematic drawing of an extravasation detection device 1. The shown extravasation device 1 comprises a cuff 3 comprising an elastic material adapted to be worn around a limb of the patient and adapted to deform to accommodate for changes in the size of the limb. In the shown embodiment, the cuff 3 comprises a silicone material as elastic material. However, in other embodiments the cuff can alternatively comprise a rubber material or a stretchable fabric material.

In the shown embodiment, the cuff 3 comprises two end sections on opposite ends of a strip forming the cuff. The two end sections can be removably joined together by a buckle 7. The buckle 7 comprises quick release means 9 for unbuckling the end sections. However, in other embodiments the cuff can be also made from a single-piece elastic material. Therefore, the buckle should be regarded as merely optional.

As shown, the extravasation detection device 1 further comprises four measuring means 5A - 5D each connected to a section of the elastic material and adapted to deform with the section of the elastic material to detect an expansion of the section of the elastic material. In the shown embodiment four measuring means 5A - 5D are employed. However, the skilled person would understand that the invention would also work with just one of the shown measuring means 5A connected to a section of the elastic material.

The measuring means 5A - 5D are realized in the shown embodiment as strain gauges that are located inside the elastic material, for example between layers of the elastic material. In other embodiments the strain gauges can be also attached to a surface of the elastic material, for example by means of an adhesive material. Also, the measuring means 5A - 5D can be alternatively or additionally realized as fiber optic Bragg sensors, and/or piezoelectric sensors.

Furthermore, the shown extravasation detection device 1 comprises a processing means 11 which is realized as a processor and which is coupled to the measuring means 5A - 5D. The processing means 11 is adapted to compare detected expansion values obtained from the measuring means 5A - 5D to at least one threshold value at subsequent time instances and trigger an alarm event if the detected expansion values exceed the threshold value at one or at a predefined number of subsequent time instances.

Also, shown in figure 1 is an alarm means 13 coupled to the processing means 11 which comprises an acoustic element 131 to produce a sound upon triggering an alarm event to notify medical staff of the extravasation event. The alarm means 13 further comprises optical elements 133A - 133N realized as LED lamps to optically indicate the occurrence of the alarm event to the medical staff. In the shown embodiment, the extravasation detection device 1 also comprises power means 15 realized as a battery.

Also, as it can be seen from figure 1 , a scale 17 is printed on a surface on the circumference of the cuff 3 to enable medical staff to optically determine the occurrence of an extravasation by identifying an increasing distance of the otherwise regular spaced markings.

Figure 2 shows a schematic drawing of an extravasation detection device 1 according to another embodiment of the invention. The shown extravasation detection device 1 comprises a cuff 3 comprising an elastic material adapted to be worn around a limb of the patient and adapted to deform to accommodate for changes in the size of the limb such as the cuff 3 of the extravasation detection device 1 shown in figure 1.

However, in contrast to the embodiment of figure 1 , the embodiment shown in figure 2 does not employ any electronic means such as strain gauges, etc. for detecting an extravasation. Instead, the measuring means of the shown extravasation detection device is realized as a scale 17 that is printed on the circumference of the cuff 3. As shown in figure 2, the scale 17 comprises a number of evenly spaced markings. By means of the shown embodiment, the occurrence of an extravasation can be optically detected when the distance between at least two of the shown markings of the scale 17 increases while fluid is injected into the patient.

Also, in the embodiment shown in figure 2, the cuff 3 optionally comprises two end sections on opposite ends of a strip forming the cuff. As shown, the two end sections are joined together by a buckle 7, which comprises quick release means 9 for unbuckling the end sections.

Figure 3 shows a method flow according to an embodiment of the invention. The method 1000 comprises the following steps:

Arranging 1001 a cuff comprising an elastic material around a limb of a patient, wherein the cuff is adapted to deform to accommodate changes in the size of the limb, and Measuring 1003, by at least one measuring means connected to a section of the elastic material and adapted to deform with the section of the elastic material, an expansion of the section of the elastic material. The method can also comprise further optional steps that are not essential for the invention, and which are therefore depicted in boxes delimitated by a dashed line:

In an example, the method further comprises the steps of: Comparing 1005, by a processing means, the detected expansion to at least one threshold value at subsequent time instances, and Triggering 1007, by the processing means, an alarm event if the detected expansion exceeds the threshold value at one or at a predefined number of subsequent time instances.

List of Reference Numerals

1 Extravasation Detection Device

3 Cuff

5A - 5D Measuring Means

7 Buckle

9 Quick Release Means

11 Processing Means

13 Alarm Means

131 Acoustic Element

133A - 133N Optical Element

15 Power Means

17 Scale

1000 Method of Detecting an Extravasation

1001 Arranging

1003 Detecting

1005 Comparing

1007 Triggering