EP3122309A1

EP3122309A1 - Device for adjusting and determining the blood flow plateau

Info

Publication number: EP3122309A1
Application number: EP15708106.8A
Authority: EP
Inventors: Graeme EISENHOFER; Christina PAMPORAKI; Angelos Filippatos
Original assignee: Technische Universitaet Dresden
Current assignee: Technische Universitaet Dresden
Priority date: 2014-03-26
Filing date: 2015-01-30
Publication date: 2017-02-01
Also published as: DE102014104167A1; US10219710B2; US20170127953A1; WO2015144125A1; DE102014104167B4

Abstract

The invention relates to a device for adjusting and determining the blood flow plateau in an extremity of a patient, wherein the device (1) has a chamber (2) whose wall (3) encloses an interior (4), and the chamber (3) has at least one opening (5), for inserting at least part of the extremity (6, 7) into the interior (4), and at least one recess (13) which permits access to the part of the extremity (6, 7) located in the interior (4), and wherein the device (1) has at least one heating element (27), which is in thermal contact with the interior (4). Provision is made that the device (1) furthermore has a means (23) for determining the blood flow plateau in the part of the extremity (6, 7) located in the interior (4).

Description

description

The invention relates to a device for adjusting and determining the blood flow plateau, in particular on a limb of a patient.

Phaeochromocytomas are dangerous tumors. These tumors usually produce certain hormones, the so-called monoamines, in large quantities. Among other things, the concentration of metabolites of the monoamines produced in the blood plasma can be used to diagnose the tumors. These metabolites include normetanephrine and metanephrine, collectively referred to as metanephrines and, when determined in blood plasma, as plasma metanephrines. However, the proportion of false-positive findings is high, especially if only the measurement of normetanephrine in plasma would be used for the diagnosis. Nevertheless, normetanephrine is the more important of the two metabolites for the diagnosis of pheochromocytomas.

In the following, the term "plasma metanephrines" refers to both metabolites together, while the terms "metanephrine" and "normetanephrine" respectively refer to the individual metabolite.

It is known from the prior art that the arterial blood is better suited for the determination of the concentration of the plasma metanephrine. However, measurement in arterial blood is not easy to perform in clinical practice. For this reason, it has not become relevant to practice. The measurement is usually carried out on a hand of the patient, by the heating of which a vasodilation is to be achieved. This results in a reduced extraction of the arterial blood and a lower response of the sympathetic nervous system. This not only allows the hormones from the arterial to venous blood to pass without significant losses, but also eliminates the local norm etanephrine release. The achievement of the highest possible vasodilation level is for the determination of the Normetanephrine concentration is crucial. When this level of vasodilation is reached and the normetanephrine concentration is then measured, false-positive plasma-metanephrine measurements can be reduced.

In practice, blood has been taken from the patients so far mostly at room temperature. However, there is a dependency between the room temperature and the measured laboratory values, which leads to an increase of false-positive findings, for example at low room temperatures. The warming of the place of blood collection, usually the hand, causes a change in the local sympathetic norepinephrine release and a change in the local blood flow. Such heating is typically done with a heating pad. From EP 1 929 980 B1 a device for adapting the blood circulation is known, which may be a glove or a cuff. The device has a chamber into which the hand can be inserted. The chamber wall consists of two layers of a collapsible and compliant material. Between the two layers, a fluid chamber is formed through which a heat exchange fluid is to flow. Finally, a pump is provided with the vacuum in the chamber to be generated. The negative pressure should ensure that the chamber wall rests directly against the palm of the hand.

WO 2011/085268 A9 is a further development of the device known from EP 1 929 980 B1. The device may additionally have sealed openings in the chamber walls which provide access to the hand surface and through which, for example, catheters may be inserted. The device described in WO 2011/085268 A9 is intended to increase the blood flow and to control the vasodilation of the vascular structures of a patient. WO 2013/143444 A1 discloses a method and a device which serve for detecting vasodilation data. To heat the Hautob erfläche a heating element is provided. By means of a laser Doppler measuring device, blood flow values are determined, from which vasodilation data are to be calculated.

However, according to the prior art, it is not possible to determine the appropriate time for a blood collection beyond doubt. In practice, therefore, a warming of the skin over a predetermined period, usually 30 to 45 minutes, performed. However, such prolonged heating can cause pain for patients, and in some cases even burns. On the other hand, the optimal time for blood sampling may have already been reached earlier, so that heating takes unnecessarily long or a deterioration of the withdrawal conditions has already occurred again. The object of the invention is to eliminate the disadvantages of the prior art. In particular, a device is to be specified which allows a blood sampling on a limb of a patient at the time when the vasodilation has reached the highest possible level. The duration of the heating and its maximum temperature should be as low as possible in order to minimize stress on the patient.

This object is solved by the features of claims 1, 12 and 15. Advantageous embodiments of the invention will become apparent from the features of the dependent claims.

According to the invention, a device for adjusting and determining the blood flow plateau is provided on a limb of a patient, wherein the device has a chamber whose wall encloses an interior space. At least one opening is provided in the chamber for the introduction of at least part of the extra feature into the interior. Furthermore, at least one recess is formed in the chamber, which allows access to the part of the extremity which is in the Interior is located. The device additionally has at least one heating element which is in thermal contact with the interior. In addition, the device has a device for determining the blood flow plateau on the part of the limb which is located in the interior.

The invention allows the local heating of a limb of the patient, whereby the maximum vasodilation is achieved. This arterialization of the patient's blood is achieved especially in the outer areas of the limb. At the same time, the extent of vasodilation can be determined by means of the device for determining the blood flow plateau. Once the highest possible vasodilation level has been reached, the patient can be provided with a blood sample at the recess provided according to the invention, which is suitable for determining the concentration of the plasma metanephrine. Such a blood sample allows a much more reliable diagnosis of pheochromocytoma. The number of false positives is considerably reduced. In addition, the blood sample can be used for the diagnosis of paraganglioma, but not always produce hormones that can be measured in the blood sample.

The device according to the invention makes it possible to determine the maximum vasodilation on a limb of a patient in a comparatively short time. This effect can be used to advantage in patients who are in an intensive care unit. In such patients, maximum vasodilation can be used to deliver medication faster and / or in greater quantities through the blood.

The determination of the maximum vasodilation in a shorter time is also of considerable economic importance. In clinical practice, it has been difficult to ensure that for a period of 30 minutes or longer, patients could be placed on a local heating pad with a heating pad, keeping the hand and forearm steady. This usually lacks both the required space, especially in an outpatient Treatment, as well as the necessary time to monitor the patient. Shortening the duration of local heating also reduces the cost of treatment. The term "blood flow plateau" describes a range of substantially constant flow velocity of the peripheral blood in the limb after the onset of heat.If heat is applied to an extremity, the peripheral blood flow rate first rises to a relative maximum for 2 to 3 minutes and drops Then, until a relative minimum is reached (Phase 1 in Figure 1), the relative minimum is above the flow rate prior to the onset of heat, after which, the blood's flow rate increases again until it reaches a substantially constant flow rate The flow rate at the blood flow plateau is generally above the flow rate at the relative maximum. For the purposes of the present invention, it may be provided that the blood flow plateau is located at the blood flow plateau eau is reached when the measured flow rate of the blood for at least one minute, preferably for at least two minutes at a constant value with a tolerance of +/- 10%, preferably +/- 5%. The actual value of blood flow rate at the blood flow plateau depends on both the patient and the method of measurement.

The device preferably has at least one measuring element for determining the temperature prevailing in the interior space. In the following, this measuring element is also referred to as a measuring element for determining the interior temperature. Furthermore, a control device may be provided for controlling the heating element. The control device may have a data input for measured values from the measuring element for determining the temperature and for measured values from the device for determining the blood flow plateau. The control device can be connected, for example, via data lines, in particular cables, to the heating element, to the measuring element for determining the temperature and to the device for determining the temperature. Be associated with mood of the blood flow plateau. The indoor temperature corresponds to the surface temperature of the limb or part thereof located in the interior of the device. It can be provided that the heating element has at least one separate, second measuring element for determining the temperature, which prevails in the wall of the chamber directly on the heating element. This temperature is hereinafter also referred to as the temperature of the heating element or heating element temperature, the second measuring element as a second measuring element for determining the heating element temperature. The temperature determined by means of the second measuring element for determining the heating element temperature can be used to control the heating element, namely alternatively or additionally to the interior temperature, which is determined by means of the measuring element for determining the temperature in the interior. For this purpose, the regulating device can furthermore have a data input for the measured values of the second measuring element for determining the temperature and can be connected to the latter via a data line, in particular a cable. At the same time, a power supply can be provided via the cable. The term "regulation of the heating element" is understood to mean the regulation of the heating power of the heating element.

The device may further comprise an evaluation unit which enables an evaluation of the measured values which are supplied by the device for determining the blood flow plateau. The evaluation unit may be part of the control device. The evaluation unit checks whether the flow velocity of the peripheral blood has reached the blood flow plateau, based on the measured values supplied by the device for determining the blood flow plateau. If this is the case, then a signal unit may be provided which outputs a signal, for example an optical or acoustic signal or both. This signal indicates to the operator of the device that the conditions - namely the highest possible vasodilation level - have been reached for a blood sample now and that the patient should now be taken the blood sample. The evaluation unit may be part of the control device. The heating element is to continuously supply heat to the limb located in the interior. The heating element is preferably an electrical heating element that converts electrical energy into heat energy. The heating element may be a heating pad. About the control device, a maximum temperature can be specified, which is to be achieved in the interior. The maximum temperature may be, for example, 44 ° C. With the beginning of the heating, the temperature in the interior is preferably increased evenly. At the same time the blood flow is measured. Once the blood flow plateau is reached, the warming can be stopped or reduced. According to the findings of the inventors, the Blutflussplateau, compared with the prior art, in less time and at low temperatures, ie temperatures below 44 ° C, achieved. According to the prior art, heating was provided for at least 30 minutes, usually 45 minutes. By means of the device according to the invention thus simultaneously reduces the burden associated with the preparation of blood collection. Pain and burns on the extremity are prevented. The device according to the invention may comprise a plurality of heating elements. Each heating element may comprise one or more thermocouples. Such a thermocouple may be a wire that heats up when supplied in electrical energy. The wire may be a metallic wire or a carbon fiber wire. Such wires generate infrared heat, whereby a warming of the interior and thus the surface of the limb can be achieved quickly, safely and efficiently. The operating voltage for supplying the heating element with electrical energy is preferably 24 V, which is considered as "non-hazardous low voltage".

The control device, which may comprise the evaluation unit and the signal unit, processes both the measured values for the interior temperature and also for the blood flow, and regulates the heating element in such a way that a uniform temperature is achieved. turanstieg the indoor temperature to the maximum value, for example, a maximum of 45 ° C, is achieved.

The control device may further comprise a power supply to supply devices and elements of the device, if necessary, with electric current.

It can be provided that the heating element, the device for determining the blood flow plateau and the measuring elements for determining the interior temperature and / or the heating element temperature are integrated into the wall of the chamber. In one embodiment of the invention it is provided that the wall of the chamber is constructed in multiple layers with a first, inner layer, which faces the interior, and a second, outer layer, wherein between the first layer and the second layer, the heating element, the device for determining the blood flow plateau and the measuring element for determining the interior temperature and, if present, the second measuring element for determining the heating element temperature are arranged.

Preferably, the chamber is formed of a flexible material. This has the advantage that the device can be pulled over the extremity of the patient, for example, his hand and forearm, by inserting the extremity into the opening formed in the chamber. A pump or other means for adjusting a negative pressure in the interior of the chamber is therefore not required. Because no negative pressure must be generated, it is also not necessary to pressure-tight seal the opening through which the limb is inserted into the interior, or the recesses formed in the wall of the chamber against the environment. However, there may be provided a fastening means for fixing the device to the extremity of the patient, for example a belt or a belt, wherein quite a number of such fastening devices can be used. The first layer and the second layer should both be made of a flexible material. Preferably, they are made of the same material. The wall of the chamber of the device according to the invention may be one or more layers. The layers should each consist of a flexible material. The flexible material may be, for example, a plastic or a textile material. The plastic may be selected from the group comprising polyurethanes, polypropylenes, polystyrene, polyethylene, for example, high density polyethylene (HDPE) or low density polyethylene (LDPE), polyvinyl chloride, and mixtures thereof. The textile material is preferably a nonwoven, more preferably a polyester-based nonwoven.

The flexible material may be an elastic material. The elastic material allows the coating chamber to be widened over the extremity and then contracted so that it fits snugly against the surface of the part of the limb located in the interior space. But it can also be used other materials that are not or only to a limited extent elastic, for example, textile materials such as nonwovens. Such materials are referred to below as "non-elastic materials", although they may have some elasticity, although such non-elastic materials can only be widened to a small extent and also contract only to the same extent. Elastic materials have the advantage that they exert no pressure on the surface of the extremity or part thereof located in the interior of the device according to the invention Such pressure could affect the quality of the measurement or the composition of the blood, which is undesirable For fixing the device according to the invention to the extemity of the patient, the fastening means are sufficient Non-elastic materials are preferred However, in the case of a multi-layered wall, it can be provided that some of the layers are made of non-elastic materials and the conductive part is made of elastic materials , wherein the wall i not altogether or - compared to elastic materials - only to a small extent elastic. If the wall of the chamber has a first, inner layer and a second, outer layer, then the first layer should consist of an allergy-tested flexible material, ie a material that does not cause any allergic reactions to the skin of the limb that is present in the interior the chamber is located. The second layer should consist in particular of a waterproof flexible material. The first and the second layer preferably consist of a textile material, for example a fleece.

Between the first layer and the second layer, in one embodiment of the invention, the heating element, the device for determining the blood flow plateau and the measuring element for determining the temperature in the interior are arranged. It can be provided that the device for determining the blood flow plateau and the measuring element for determining the temperature in the interior adjacent to the first layer. The measuring element for determining the temperature in the interior should be thermally insulated against the heating element by means of an insulating material. It can be provided that the device for determining the blood flow plateau is also arranged insulated by means of an insulating material in a manner insulated against the heating element. The sensor of the measuring element for determining the temperature in the interior should be in contact with the surface of the extra when it is inserted into the interior of the chamber. For this purpose, an opening may be formed in the first position, which surrounds the sensor. The device for determining the blood flow plateau and the measuring element for determining the temperature in the internal space are preferably jointly embedded in a third layer of the chamber, which, apart from the region of skin contact of the measuring sensor, is adjacent to the first layer. The third layer can likewise be formed from a nonwoven, for example the same nonwoven as the first and / or second layer. The heating element and, if present, the second measuring element for determining the temperature of the heating element may be formed as a fourth layer adjacent to the third layer. The measuring element for determining the temperature in the interior is preferably a temperature sensor. The device may comprise a plurality of measuring elements for determining the interior temperature, in particular a plurality of temperature sensors. The second measuring element for determining the temperature of the heating element is preferably also a temperature sensor. The device may comprise a plurality of second measuring elements for determining the heating element temperature, in particular a plurality of temperature sensors.

The fourth layer may be followed by a fifth layer which consists of an insulating material which thermally insulates the second layer from the fourth layer. The insulation material may be a plastic. It may be the same plastic from which the insulation material of the third layer consists.

The insulating material can be aluminum or silicone, with only one type of insulating material being suitably chosen for the device. In addition to the thermal insulation, the insulating material also serves to shield the measuring element for determining the interior temperature and the device for determining the blood flow. The second outer layer adjoins the fifth layer. The layers that make up the wall of the chamber are preferably permanently connected to each other, for example, they can be welded or glued together.

The device for determining the blood flow plateau can be any device that is used according to the prior art for determining the blood flow plateau. The device for determining the blood flow plateau is preferably a laser Doppler anemometer or a strain gauze plethysmography device, with a laser Doppler anemometer being particularly preferred. Laser Doppler anemometers are sometimes referred to in medical practice as a laser Doppler blood flow meter or laser Doppler flow meter, the associated measurement method as laser Doppler flowmetry. Strain-gauge Plethysmography devices, sometimes referred to as strain gauge plethysmography devices, use occlusion plethysmography as a method of measuring blood flow. By means of the device for determining the blood flow plateau, the peripheral blood flow, that is to say the flow velocity of the blood in peripheral blood vessels, is expediently measured continuously. If the laser Doppler flowmetry is used, the flow rate of the blood is measured in so-called "perfusion units", PU for short, where 1 PU is equal to 10 mV The unit of flow rate for the strain gauge plethysmography is the blood flow BF where 1 BF is equal to 1 ml / 100 ml / min.

The device is provided according to the invention for setting and determining the blood flow plateau on a limb of a patient. In particular, the limb may be a hand, a forearm, a hand and the whole forearm or part of the forearm, a foot, a lower leg, a foot and all the adjacent lower leg or part of the lower leg , In a preferred embodiment, the device for adjusting and determining the blood flow plateau is determined on a hand and the adjacent forearm or a part of the forearm. In this case, the chamber of the device may be in the form of a glove, the interior of which is adapted to receive a patient's hand and forearm or a part thereof.

If the device according to the invention for adjusting and determining the blood flow plateau is in the form of a glove into which the hand and forearm of a patient are to be inserted, then the sensor of the measuring element for determining the interior temperature should be located in an area on the forearm adjacent to the wrist.

Preferably, two recesses are formed in the chamber, which allow access to the part of the limb, which is located in the interior thereof. The recess may be adapted to include a catheter, such as a venous catheter Hose, a cannula, such as a venous cannula, or a measuring device, such as a thermostat probe, each alone or together through the recess to the extremity, which is located in the interior of the chamber, can be performed. Preferably, the recess is adapted so that a cannula, in particular a venous cannula, can be guided together with a thermostatic probe to the extremity. Conveniently, covers are provided for the recesses with which the recesses can be sealed heat-resistant. This is intended to minimize or completely prevent the heat exchange between the interior and the surroundings via the recesses, thereby ensuring homogeneous temperature distribution within the interior.

If the chamber has the form of a glove into the interior of which the hand of a patient and his forearm can be wholly or partially inserted, it can be provided that the interior contains a first part for receiving the hand and a second part for receiving the forearm or a part of it. In this case, a first recess may be formed in a portion of the wall surrounding the first part of the interior. A second recess may be formed in a portion of the wall surrounding the second part of the interior. Preferably, the first recess is formed in a region of the wall which forms the palm of the glove, while the second recess is formed in a region adjacent to the opening for introducing at least a portion of the extremity. Both recesses should lie on a straight line that is parallel to the longitudinal axis of the glove. Thus, with the hand and forearm inserted into the glove through the opening, the first recess is at the distal end of the glove, whereas the second recess is at the proximal end adjacent the patient's elbow.

According to the invention, a method for setting and determining the blood flow plateau on a limb of a patient by means of a device according to the invention is also provided, comprising the steps (a) inserting a limb into the interior of the chamber such that at least a portion of the limb is in the interior of the chamber;

(b) applying thermal energy to the part of the limb by means of the heating element and continuously determining the temperature in the interior and the blood flow at the part of the limb; and

(c) outputting a signal when the blood flow has reached the blood flow plateau. The output of the signal informs the user of the device according to the invention that optimal conditions exist for taking a blood sample from the patient. This sample is particularly suitable for the determination of the concentration of plasma metanephrines if a pheochromocytoma is to be detected or excluded on the basis of the measured values.

It is preferably provided that the time of reaching the blood flow plateau, starting from the beginning of the heating in step (b), and the temperature in the interior, at which the blood flow reaches the blood flow plateau, are detected. It may further be provided that the supply of thermal energy by means of the heating element is reduced or stopped as soon as the blood flow plateau is reached.

In accordance with the invention, moreover, the use of a device according to the invention for adjusting and determining the blood flow plateau is provided on a limb of a patient. The apparatus and method of the present invention are not limited to the setting of conditions suitable for taking a blood sample to be used for the diagnosis of pheochromocytoma or paraganglioma. It is also possible to set conditions, in particular temperature and blood flow, which are advantageous for other purposes. The invention is based inter alia on the following considerations. The perfusion of the skin can be measured by means of laser Doppler flow measurement (English: Laser Doppler Flowmetry). In this way, the peripheral blood flow can be detected. Previous studies show that local skin warming of the lower arm causes an increase in the flow of the skin's blood in two phases. A first rapid increase in blood flow is observed within 2 to 3 minutes after the onset of warming. Followed by a short blood flow descent, which lasts for 20 to 30 minutes on a certain plateau, the blood flow plateau (see Fig. 1). Essential here is the recognition that this plateau depends on vascular factors. For example, in patients with peripheral microvascular dysfunctions, which may occur, inter alia, in the case of cardiovascular diseases, decreased vasodilation. It should be noted that patients treated with statins showed a lower blood flow plateau. In the case of prolonged warming, a phenomenon known as "the away" is sometimes observed.This phenomenon, in which the blood flow slowly returns to its starting point, usually occurs 45 minutes after the onset of warming, so the warming protocols have a duration of 30-45 However, there are no available research results for patients with marked peripheral dysfunction or impaired vasodilating ability, as these patients are often seen to have a lower plateau of blood flow, possibly before the expected time, usually 45 minutes a premature "away" phenomenon may appear, compromising the validity of a blood sample taken after the onset of "the away." The inventors have therefore come to the realization that it is not sufficient just a conventional heater to use, because in this way e can not be determined if and when the desired vasodilation occurs. Furthermore, the vasodilation level can not be determined, and also the exact time of the blood flow plateau remains unknown. In view of the above, simultaneous limb warming and blood flow evaluation are critical in diagnosing or excluding a pheochromocytoma or paraganglioma. experi- The experiments carried out by the inventors using conventional heaters using laser Doppler flowmetry or gauge plethysmography equipment confirmed that arterialization can generally be achieved with local warming of the forearm, but also showed that substantial limitations existed. which made the development of a new device, namely the device according to the invention, necessary.

There are different heating protocols for local application of heat to the surface of a limb, where a temperature of 42 to 44 ° C is usually recommended. At this temperature, as shown in Figure 1, vasodilation is induced in two phases, a first phase comprising the increase in flow rate from the start of heating to the relative maximum and the decrease in flow rate to the relative minimum, and a second phase, which involves the increase in flow velocity from the relative mini- mum to reaching the blood flow plateau.

The heating pads used in the prior art for local heating of the Hautob erfläche with temperatures of 42 to 44 ° C could lead to a heating of the main surface to temperatures above the temperature of the heating pad. The temperature of the skin surface was not measured. Although local warming to a temperature of 42-44 ° C, as well as prolonged warming to these temperatures, is well tolerated by most subjects, it sometimes causes discomfort, such as pain or burns, in patients with abnormal microvascular function, especially if the tempe Temperature on the Hautob erfläche was still above the temperature of the heating pad. Therefore, such patients are so far excluded from the arterialization by heating. The device according to the invention can also be used in such patients, because the time of heating is considerably shortened, because the highest possible vasodilation level in these patients sets earlier and at lower temperatures. When using the device according to the invention it is determined when the Blutfluss- plateau is reached. The device according to the invention can for this purpose output the exact time and the temperature of the interior. Warming of the limb for 30 minutes or longer is thus avoided. If the blood flow plateau is reached at an interior temperature of less than 44 ° C., then the device according to the invention heats the limb only to this temperature level, wherein it subsequently keeps the temperature at this temperature level.

The inventors have found that conventional warming devices, even in combination with laser Doppler flowmetry, can achieve and measure arterialization in many cases. However, such a combination does not have the capability of simultaneously heating and arithmetic determination of the blood flow plateau, since there is a consequent lack of controlled limb temperature control.

Based on these findings, the device according to the invention has been developed, which determines the exact time and the exact temperature of the blood flow plateau in each patient during the local heating of a limb, especially the forearm. By means of the control device of the device according to the invention, the temperature of the interior can be stably set to a temperature of less than or equal to 44 ° C. in order to avoid an unnecessary higher heating of the limb and thus possible side effects. The device according to the invention can inform the operator by means of a signal, for example with a characteristic tone, as soon as the blood flow level has been reached and thus there are conditions which are suitable for taking a blood sample. This avoids unnecessary prolonged heating and thus eliminates the risk of the "away" phenomenon.

Ideally controlled blood flow temperature measurements reduce the side effects of prolonged heating. By means of the invention, the diagnostic performance and diagnostic reliability can be increased because the blood sample can be taken at a time when optimum conditions are in place, so that the concentration of the plasma metanephrine in that blood sample reliably indicates the presence or absence of a plasma metanephrine Pheochromocytoma can be closed. The analysis of the blood sample is facilitated because both the temperature at sampling and the blood flow are known and set to ideal values.

The control device of the device according to the invention can ensure that the arterialization of the blood and thus the maximum vasodilation can be realized with an optimized temperature regime. Sampling, which used to take 30 to 45 minutes, can now be done in less time because the blood flow plateau is reached faster. This prevents discomfort such as pain and burns. Furthermore, the temperature prevailing in the interior of the chamber is determined when the blood flow plateau is reached.

The invention will be explained in more detail below with reference to embodiments, which are not intended to limit the invention, with reference to the drawings. Show

Fig. 1 is a diagram schematically showing the change in blood flow as a function of the duration of heating;

2 shows a view of an embodiment of a device according to the invention for adjusting and determining the blood flow plateau on the hand and forearm of a patient;

Fig. 3 is a detail view of the embodiment shown in Fig. 2;

Fig. 4 is a schematic sectional view taken along line A - A in Fig. 3; and 5 shows an exemplary signal flow diagram for controlling the heating element of the embodiment of the device according to the invention shown in FIGS. 1 to 4.

The embodiment of a device 1 according to the invention shown in FIGS. 2 to 4 has a chamber 2 which has the shape of a glove. The chamber 2 can therefore also be referred to as a glove. The wall 3 of the chamber 2 surrounds an interior space 4. In the wall, an opening 5 is formed, via which the hand 6 and the forearm 7 of a patient can be inserted into the interior 3 up to the elbow thereof. In FIGS. 2 to 4, the hand 6 and the forearm 7 of the patient are located in the interior 4 of the chamber 2. The wall 3 extends as far as the elbow 8 of the patient so that its upper arm 9 is exposed. In this case, the glove-shaped chamber 2 is fixed by means of belts 10 on the lower arm 7 of the patient. A first belt 10 is attached to the elbow 8 of the patient, a second belt 10 above the wrist of the hand. 6

The interior 4 has a first part 11 and a second part 12. In the first part 11 of the inner space 4 is the hand 6, in the second part 12 of the inner space 4 of the lower arm 7. In the wall 3 of the glove-shaped chamber 2 recesses 13, 14 are formed access to the hand 6 and the lower arm. 7 allow. It can be seen in FIG. 2 that the first recess 13 is formed in a region of the wall 3 which surrounds the first part 11 of the inner space 4. In this case, the first recess 13 is arranged such that it is located in the region of the palm of the glove-shaped chamber 2. The palm of the glove-shaped chamber 2 is the part of the wall 3, which rests against the palm of the hand 6. The second recess 14 is formed in a region of the wall 3, which adjoins the opening 5. Both recesses 13, 14 lie on a straight line which runs parallel to the longitudinal axis of the glove-shaped chamber. The first recess 13 is thus located at the distal end of the glove-shaped chamber 3, whereas the second recess 14 is located at the proximal end of the glove-shaped chamber Chamber 3, which is adjacent to the elbow 8 of the patient. At the edge of the recesses 13, 14 are each covers 15 which should close the recesses 13, 14 heat-tight. When the covers can be the part of the wall 3, which had to be separated from the rest of the wall 3 to create the recesses 13, 14.

The recesses 13, 14 provide access to the extremity, in this case the hand 6 and the forearm 7. Via the recesses 13, 14, for example, a venous cannula 16 can be guided to the extremity which is located in the interior 4 of the chamber 2 , In Fig. 3, the second recess 14 is shown, which grants access to the lower arm 7. Through the second recess 14, a venous cannula 16 is guided. The venous cannulae 16 may each be connected to a fluid conduit means, for example a tube 17.

2, a venous cannula 16 is shown in both recesses 13, 14. As a rule, however, only one venous cannula 16 is required for taking a blood sample. It is convenient to insert the venous cannula 16 into one of the recesses 14 before starting to apply heat via the heating element 27 in order to be able to take the blood sample immediately after the signal has been output. For most patients, the second recess 14 should be used to attach a venous cannula 16 to the blood sample. In some cases, however, it may be appropriate to use the first recess 13 thereto. After insertion of the venous cannula 16 into one of the recesses 13, 14, both recesses should be closed by means of the covers 15. Only then should be started with the supply of heat through the heating element 27.

As shown in FIG. 4, the wall 3 of the chamber 2 has a first, inner layer 21 and a second, outer layer 22. The first layer 21, which delimits the inner space 4 and bears against the hand 6 and the lower arm 7, which are located in the interior 4, consists of an allergy-tested flexible material. The second layer 22 is made of a waterproof flexible material. It forms the outside of the Wall 3. The first layer 21 and the second layer 22 are preferably made of a nonwoven fabric, particularly preferably of the same nonwoven fabric. The nonwoven fabric can be a polyester-based nonwoven fabric. Between the first layer 21 and the second layer 22, a third layer 25 made of a nonwoven fabric is arranged. The third layer may consist of the same nonwoven fabric as the first layer 21 and / or the second layer 22. Embedded in the third layer 25 are the laser Doppler blood flow meter 23 (or other means of determining blood flow, such as a strain gauge plethysmography apparatus) and a first temperature sensor 24. The first temperature sensor 24 is in contact with the inner space 4 so that it can detect the indoor temperature and thus the surface temperature of the lower arm. The laser Doppler blood flow meter 23 is arranged so that it can emit light through the first layer 21 into the lower arm 7 and receive the light reflected there. Within the third layer, layers of insulating material are provided, which include the Laser Doppler blood flow meter 23 and the first temperature sensor 24 for determining the indoor temperature of an electric heating element 27 in a fourth layer 26 together with a second temperature sensor 28 is arranged to determine the temperature of the heating element 27, thermally isolate. The insulating material 30 may be aluminum or silicone. The fourth layer 26 adjoins the third layer 25. Finally, between the fourth layer 26 and the second, outer layer 22, a fifth layer 29 of an insulating material, for example aluminum or silicone, is formed, which insulates the second layer 22 against the heating element 27. The heating element comprises a plurality of thermoelements, for example wires made of metal or carbon.

To receive the measured values from the first temperature sensor 24, the second temperature sensor 28 and the laser Doppler blood flow meter 23 and to control the heating element 27, a control device 28 is provided. The regulating device is connected via an electrical cable 19 to the first temperature sensor 24, the second temperature sensor 28, the laser Doppler blood flow meter 23, the heating element 27 and the thermostat sensors on the recesses 13, 14 are connected. The control device 18 comprises the evaluation unit and the signal unit (both not shown). The signal flow diagram shown in Fig. 5 is an example of the control of the heating element of a device according to the invention. Input variables for the control of the heating element are the actual temperature of the limb or the part thereof, which are located in the inner space 4, the target temperature of the limb or the part thereof, which are located in the inner space 4, and the temperature of the thermocouples of the heating element 27. The actual temperature of the limb or the part thereof, which are located in the inner space 4, is determined by means of the first temperature sensor 24. The target temperature of the limb or the part thereof, which are located in the interior 4, is specified by the user of the inventive device. The temperature of the thermocouples of the heating element 27 is determined by means of the second temperature sensor 28. The values for these three input variables, which are detected by the controller 31, are combined at the addition point with the voltage value of the heating element as the fourth input variable. Output variable is the voltage value of the heating element. The voltage value is also detected and fed back to the controller 31 at the branch point. The regulation should be automatic.

Another input variable is the flow velocity of the blood, which, however, does not enter into the regulation of the heating element 27. The flow rate of the blood is detected to be able to deliver a signal when the blood flow plateau is reached. LIST OF REFERENCE NUMBERS

1 device

2 chamber

3 wall

4 interior

5 opening

6 hand

7 forearm

8 elbows

9 upper arm

10 belts

11 first part of the interior

12 second part of the interior 13 first recess

14 second recess

15 cover

16 venous cannula

17 hose

18 control device

19 cables

21 first, inner situation

22 second, outer layer

23 Laser Doppler blood flow meter

24 first temperature sensor

25 third location

26 fourth location

27 heating element

28 second temperature sensor

29 fifth position Insulation material regulator

Claims

claims

1. A device for adjusting and determining the blood flow plateau on a limb of a patient, wherein the device (1) has a chamber (2) whose wall (3) encloses an interior space (4), and in the chamber (3) at least one opening (5) for the introduction of at least part of the limb (6, 7) in the interior (4) and at least one recess (13) is formed, which allows access to the part of the limb (6, 7) located in the interior (4), and wherein the device (1) comprises at least one heating element (27) in thermal contact with the internal space (4), characterized in that the device (1) further comprises means (23) for determining of the blood flow plateau at the part of the limb (6, 7) located in the internal space (4).

2. Apparatus according to claim 1, characterized in that it comprises at least one measuring element (24) for determining the temperature in the interior space (4).

3. A device according to claim 2, characterized in that it comprises a control device (18) for controlling the heating element (27), wherein the control device (18) has a data input for measured values of the measuring element (24) for determining the temperature in the interior ( 4) and for readings from the means (23) for determining the blood flow plateau.

4. Device according to one of the preceding claims, characterized in that it comprises an evaluation unit, which allows an evaluation of the measured values of the device (23) for determining the Blutflussplateaus, and a signal unit which enables the output of a signal when the Blutfluss- plateau is reached.

5. Device according to one of the preceding claims, characterized in that the heating element (27), the device (23) for determining the Blutfluss- plateau and the measuring element (24) for determining the temperature in the interior space (4) in the wall ( 3) of the chamber (2) are integrated.

6. Device according to one of the preceding claims, characterized in that the wall (3) of the chamber (2) is constructed in multiple layers with a first, inner layer (21) facing the interior (4), and a second, outer Layer (22), wherein between the first layer (21) and the second layer (22), the heating element (27), the device (23) for determining the Blutfluss- plateau and the measuring element (24) for determining the temperature in the interior (4) are arranged.

7. Device according to one of the preceding claims, characterized in that the device (23) for determining the blood flow plateau is a laser Doppler anemometer or a strain gauge plethysmography device.

8. Device according to one of the preceding claims, characterized in that it comprises at least one fastening device (10) for fixing the device (1) on the extremity (6, 7) of the patient.

9. Device according to one of the preceding claims, characterized in that the chamber (2) is a glove whose interior (4) is adapted to the hand (6) of a patient and his forearm (7) or a part thereof can record.

10. The device according to claim 9, characterized in that the interior (4) of the glove (2) has a first part (11) for receiving the hand (6) and a second part (12) for receiving the forearm (7) or a Part thereof, wherein a first recess (13) in a portion of the wall (3) is formed, which surrounds the first part (11) of the inner space (4), and a second recess (14) is formed in a portion of the wall (3) which surrounds the second part (12) of the inner space (4), the first recess (13) being formed in a region forming the palm of the glove (2 ), and the second recess (14) is formed in a region adjacent to the opening (5) for introducing at least part of the limb (6, 7).

11. Device according to one of the preceding claims, characterized in that on the recess (13, 14) a thermostat probe is arranged.

12. A method for adjusting and determining the blood flow plateau on a limb of a patient by means of a device according to one of claims 1 to 7, comprising the steps

(A) introducing a limb (6, 7) in the interior (4) of the chamber (2), so that at least a part of the limb (6, 7) in the interior (4) of the chamber (2) is located;

(b) applying thermal energy to the portion of the limb (6, 7) by means of the heating element (27) and continuously determining the temperature in the internal space and the blood flow at the portion of the limb (6, 7); and

(c) outputting a signal when the blood flow has reached the blood flow plateau.

13. The method according to claim 12, characterized in that the time of reaching the Blutflussplateaus and the temperature in the interior, at which the blood flow reaches the Blutflussplateau, are detected.

14. The method according to claim 12 or claim 13, characterized in that the supply of thermal energy in step (b) is reduced or stopped as soon as the Blutflussplateau is reached.

15. Use of a device according to one of claims 1 to 11 for setting and determining the blood flow plateau on a limb (6, 7) of a patient.