WO2011131358A2

WO2011131358A2 - Method and device for determining the fistula flow of a fistula for dialysis treatment

Info

Publication number: WO2011131358A2
Application number: PCT/EP2011/002022
Authority: WO
Inventors: Ulrich Pfeiffer; Reinhold Knoll
Original assignee: Up-Med Gmbh
Priority date: 2010-04-20
Filing date: 2011-04-20
Publication date: 2011-10-27
Also published as: WO2011131358A3; DE102010015664A1

Abstract

The invention relates to a method and device for determining the fistula blood flow of a fistula for dialysis treatment with a dialysis liquid by means of a dialysis machine, wherein the fistula has an arterial fistula outlet and a venous fistula inlet, comprising the following steps: varying the volume flow in the dialysis machine until local recirculation occurs in der fistula; determining the value of the volume flow in the dialysis machine when local recirculation occurs in the fistula as a first value Q_DO,and calculating the fistula blood flow Q_so of the fistula on the basis of the first value Q_DO.

Description

Method and device for determining the fistula flow of a fistula for dialysis treatment

The invention relates to a method and apparatus for determining the fistula of a fistula for the Dialysebe ^¬ treatment. In particular, the invention relates to a method and a device for determining the fistula flow of a fistula for dialysis treatment and to a method and a device for determining the volume of a fistula or a shunt, in particular the local shunt volume and the entire shunt volume.

In methods of chronic blood purification therapy, for example arteriovenous hemodialysis, hemofiltration and hemodiafiltration, blood is delivered via an extracorporeal

Circulated blood. As an outlet or access to the blood vessel system, an arteriovenous fistula or a shunt is often created surgically. Likewise, the use of an implant is possible.

For the functioning of the fistula their perfusion is important. If the fistula flow drops below a critical value, the risk of fistula thrombosis increases with the possible loss of vascular access. In this case, it is thought out to surgically apply a second arteriovenous fistula. Since this fistula is available for dialysis only about six weeks after the procedure, it is important to see this development sufficiently long in advance. If the fistula flow during the dialysis treatment is inadequate and smaller than the extracorporeal blood flow, local fistula recirculations occur, whereby a fraction of the dialyzed blood returned to the fistula via the venous blood line is returned to the dialyzer via the arterial blood line. As the local fistula circulation increases, the effectiveness of the dialysis treatment decreases proportionally. In the prior art, the quality of the fistula perfusion or fistula flow is determined by means of an ultrasound Doppler measurement. Here, the fistula or shunt cross-section and the mean flow velocity in the fistula or the shunt are determined. The shunt blood flow can be calculated from this, compare Schäberle, ultrasound in vascular diagnosis, therapy-oriented textbook and Atlas, Springer, 2nd edition, chapter 4. This ultrasound measurement to determine the fistula perfusion or the fistula flow and thus the quality of the fistula is a time-consuming Measurement that requires experienced personnel.

In addition to fistula perfusion or fistula flow, the fistula volume or shunt volume is also an interesting quantity, since this volume together with the fistula flow for the correct calculation of intrathoracic volumes, such as, for example, the intrathoracic blood volume can be used. Of interest here is the entire shunt volume, which includes the volume of the vascular system from the junction of the main body artery (aorta) to the arterial shunt outlet, the volume of the vascular system from venous shunt access to the central venous system, and the local shunt volume. So far, the shunt volume is calculated by the dimension of the shunt. It results from the product of the cross-sectional area of the shunt with the length of the shunt. These dimensions are u.a. determined by ultrasonic measurement (Schäberle, see above).

The object of the present invention is therefore to provide a method and a device for the easier determination of the fistula flow of a fistula for the dialysis treatment. A further object of the present invention is therefore to provide a method and a device for simplifying the determination of the volume, in particular of the local volume and the total volume of a fistula for the dialysis treatment. The objects are achieved by a method and a device according to the independent claims. Advantageous embodiments can be found in the dependent claims. In particular, the object is achieved by a method for determining the fistula flow ("fistula blood flow" and "fistula flow" are used synonymously in this invention description) of a fistula for dialysis treatment, in particular with a dialysis fluid, solved by means of a dialysis machine, in which the fistula an arterial Fistelabgang and a venous fistula access, comprising the steps of: changing the volume flow of the extracorporeal blood flow Q _D in the dialysis machine to the occurrence of local recirculation in the fistula; Determining the value of the volume flow of the extracorporeal blood flow Q _D in the dialysis machine when local fistula recirculation occurs as the first value Q _D0 and calculating the fistula blood flow Q _S o of the fistula from the first value Q _D0 . The term "fistula flow" or "fistula blood flow" for all embodiments of the invention preferably designates the blood flow through the fistula from arterial to venous direction. Preferably, these terms refer to blood flow through the fistula when the fistula is not attached to a dialysis machine or blood flow is not withdrawn from the fistula in the direction of a dialysis machine (Q _s o) The feature "blood flow through the fistula when no blood for dialysis ", thus preferably denotes the blood flow through the fistula, if it is not connected to a dialysis machine or blood flow is withdrawn in the direction of a dialysis machine from the fistula.This parameter, ie the blood flow through the fistula, if no blood dialysis is an indicator of the quality and fitness of the fistula for dialysis.A method according to the invention and a device according to the invention are therefore preferably provided for determining the fistula flow if no blood flows or flows for dialysis. The dialysis treatment is a method of chronic blood ^¬ purification therapy such as hemodialysis, hemodialysis filtration and hemodiafiltration. Here, blood is passed through ei ^¬ nen extracorporeal blood circulation and there purified using a dialysis liquid. The extracorporeal blood ^¬ circuit is realized by a dialysis machine, through which blood is pumped and is cleaned in combination with the Dialy ^¬ seflüssigkeit. In this case, an arterio-venous fistula or a shunt is created as access of the dialysis machine to the blood vessel system. In this case, an arterial fistula ^¬ disposal is provided, via which removed the arterial blood and the dialysis machine is supplied. Furthermore, a venous fistula access is provided, via which the blood purified in the dialysis machine is returned to the blood vessel system. The fistula flow of a fistula for dialysis treatment is now defined by the flow, in particular the blood flow at the arterial fistula outlet or at the venous fistula access. The area of the blood vessel system between the arterial fistula exit and the venous fistula access is called local fistula or local shunt. Since the individual points of the arterial fistula outlet or venous access to the fistula can vary in the individual dialysis treatment, the local shunt and its volume also vary between arterial and venous fistula access.

In the dialysis machine, a pump device is preferably provided which pumps the blood which has been taken from the arterial fistula outlet in the extracorporeal blood circulation and through the dialysis machine and feeds it back to the blood vessel system at the venous fistula access. By adjusting the flow rate or the flow rate of this dialysis pump results in a corresponding volume flow in the extracorporeal blood circulation. The volume flow in the extracorporeal blood circulation is therefore preferably set via the delivery flow of the dialysis pump. When the flow rate of the dialysis pump is very low, the blood at the venous access to the fistula is slowly supplied to the blood vessel system so that all the supplied blood flows into the venous blood vessel system and forwarded to the heart. When the conveyor ^• Strom dialysis pump is very high, it may happen that the coming from the extracorporeal circulation of blood is not only supplied to the venous Fistelzugang the venous blood vessel system, but is also pressed in the opposite direction and thus in part from venous fistula access is promoted directly back to the arterial fistula exit. It thus flows blood from the extracorporeal blood circulation into the blood vessel system and partly directly through the local shunt or the local fistula from the venous fistula access to the arterial fistula exit. In this case, it is said that a local recirculation occurs. With local recirculation, the direction of blood flow through the local fistula changes. In the case of dialysis treatment, this occurrence of local recirculation is usually monitored because, when local recirculation occurs, the efficiency of dialysis is reduced and this condition is to be avoided. In the present invention, the state of the local recirculation is preferably forced for a short time in order to determine or record or store or store the value of the volume flow of the extracorporeal blood flow Q _D in the dialysis machine precisely at the time of occurrence of the local recirculation. Preferably, it is also possible that by measurements at different volume flows by extrapolation, the volume flow is determined at which a local recirculation would occur, without forcing the local recirculation itself.

By ascertaining the value of the volume flow of the extracorporeal blood flow Q _D in the dialysis machine when local recirculation occurs in the local fistula, a volume flow within the dialysis machine, that is to say in the extracorporeal blood circulation, is determined, which leads to the venous flow in the fistula Fistula access or arterial fistula exit corresponds, which would occur if no dialysis treatment takes place. By varying the volume flow of the extracorporeal blood flow Q _D in the dialysis machine can thus be determined the value Q _D0 , in which just no local recirculation occurs and thus keeps the volume flow in the dialysis machine in equilibrium in such a way that local recirculation does not occur at all and the blood in the extracorporeal blood circulation is supplied in its entirety to the venous blood vessel system. In this condition, blood flow through the local fistula, ie between the arterial fistula exit and venous fistula access, would be zero. Thus, Q _D0 is the dialysis blood flow when the dialysis pump pumps just enough to equal the pressure at the arterial fistula exit at the venous fistula access pressure. Since then no

Pressure difference is more present, no blood flows through the fistula. In a first approximation, Q _D o may also denote the volume flow of the extracorporeal blood flow at which local recirculation takes place or is observed for the first time.

From this external characteristic of the volume flow of the extracorporeal blood flow Q _{D0 of} the dialysis machine when the local recirculation occurs, the fistula flow Q _S o of the fistula can now be determined or determined, which would occur if the dialysis machine were not connected or the dialysis pump were stationary, ie the fistulous flow without extracorporeal blood flow. Qso is caused by the pressure difference between the arterial and venous systems and influenced by fistula geometry.

In this way it is possible to determine the quality of the fistula or the shunt access in a patient even during a dialysis treatment. It is therefore no longer necessary, as in the prior art, to perform a separate measurement with ultrasound, in which the shunt cross-section had to be examined separately, and only then Q _S o could be determined. By simply determining the value of the volume flow to be determined externally in the dialysis machine when local recirculation occurs, it is possible according to the invention to determine the quality of the fistula and thus the functionality of the fistula simply as a by-product in the dialysis treatment. As dialysis treatment usually takes longer, the lower the volume flow of extracorporeal blood flow Q _{D is} in the dialysis machine, it is always a concern of the dialysis treatment to set the maximum volume flow upward. On the other hand, a local recirculation should be avoided because it would reduce the efficiency of the dialysis treatment. In a normal dialysis treatment, therefore, this is always done in a range of the flow rate that is close to the point of occurrence of the local recirculation, so that there is a constant control of the volume flow of the dialysis machine while monitoring the occurrence of the local recirculation. It is therefore generally not necessary in a dialysis treatment that a separate series of measurements for determining the local recirculation according to the present invention is made separately, but these measuring points can also be evaluated during the dialysis treatment in dependence of the volume flow and in this way and The flow rate of the dialysis machine can be detected and determined, in which a local recirculation occurs, without the volume flow having to be varied separately for this measurement.

In a further embodiment of the present invention, changing the volume flow of the extracorporeal blood flow Q _D in the dialysis machine is an increase in the volume flow of the extracorporeal blood flow Q _D in the dialysis machine.

Thus, by increasing the volume flow, the volume flow of the extracorporeal blood flow Q _D is preferably reached at which a local recirculation occurs. The increase in the volume flow may preferably be carried out stepwise. Alternatively, when starting with a high volume flow at which local recirculation has already occurred, the volume flow Q _D can be changed by reducing the volume flow. It is particularly preferred during the dialysis treatment to determine the differently occurring volume flow of the extracorporeal blood flow Q _D together with the occurrence of local recirculation in order to particularly preferably by extrapolation - to determine the volume flow of the extracorporeal blood flow Q _D , occurring at the local recirculation or would occur for the first time. Thus, it is conceivable, for example, to determine the value by which the local recirculation occurs for the first time by measuring the local recirculation to different volume flows in the dialysis machine without actually having to adjust this volume flow and check it separately. In another embodiment of the present invention, calculating the fistula flow Q _s o of the fistula consists of the first value Q _D0 in taking over the first value Q _D0 as the fistula flow Q _S o. By taking over the first value Q _D0 as the fistula flow Qso In a good approximation, the flow Q _D o, in which no local recirculation occurs, has been adopted. As a result, the corresponding blood flow through the fistula can be determined directly from the volume flow of the extracorporeal blood flow in the case of a local occurrence of recirculation Q _D0 , if no blood flows or would flow for dialysis.

In another embodiment of the present invention, the fistula flow Q _S o of the fistula is calculated from the first value Q _D o according to the following formula:

in which

Q _{D0 is} the dialysis blood flow when no blood is flowing through the local fistula;

Qso blood flow through the fistula is when no blood is flowing for dialysis and

k is a correction value between 0 and 1. Preferably, k is calculated according to

in which

AP is the mean central arterial blood pressure;

CVP is the mean central venous blood pressure;

PI is the pressure at the arterial fistula outlet and

P2 is the pressure at the venous fistula access.

PI or P2 preferably designate the pressure at the arterial fistula outlet or at the venous fistula access when no blood flows for dialysis. This preferred calculation of k holds for all k present in the document.

By taking into account the correction factor (1-k) in the determination of Q _s oas Q _D0 , the resistance of the blood vessel system is considered. The difference between the pressures PI and P2 determined at the access points characterizes the pressure drop between these two approaches. The difference between the central arterial blood pressure AP and the central venous blood pressure CVP accounts for the total pressure drop on the way the blood passes through the blood vessel system from the heart to return. By taking this factor into account, a reduction of Q _{D0 is} taken into account in the determination of Qso, which corresponds to the corresponding pressure losses. The pressures PI and P2 can preferably be measured by appropriate pressure sensors on the arterial or venous fistula outlet or access. The mean central arterial pressure AP is almost identical to the mean arterial pressure measured in a larger artery, which can be easily determined in addition to the systolic and diastolic blood pressure. This mean arterial pressure is between systolic and diastolic arterial pressure. He is determined by the fact that the area is averaged over the arterial pressure curve over time. He is preferred over

calculated approximately, where

MAP of the mean arterial pressure,

AP _D or AP _{S is} the diastolic or systolic arterial blood pressure and is preferred. In central blood vessels as well as at high

Heart rates are particularly preferred.

The central venous blood pressure CVP can preferably be estimated and is usually about 5-10 mmHg. Most preferably CVP is measured via a central venous catheter.

Particularly preferably, Q _S o can be determined from Q _D0 with a fixed correction factor (lk) <1. Particularly preferably, the correction factor is 0.8. Most preferably, the correction factor (1-k) is determined via an estimate of the length of the blood vessel system. In this case, the correction value is preferred

in which

Lio _ka i is the distance between arterial fistula access and venous fistula access and

L _t o _ta i is the length of the entire fistula.

Preferably, L _tota i is determined via a measuring tape, particularly preferably via at least one angiographic X-ray image. This particularly preferred calculation of k holds for all k present in the document. In the methods according to the invention and by the devices according to the invention, the occurrence of the local recirculation can be determined by any suitable method. Preferably, the occurrence of the local recirculation is determined by a dilution measurement, for example an indicator dilution measurement, as described, for example, herein in particular in connection with the method according to the invention for determining the local volume of a fistula. For this purpose, a dilution measurement is preferably carried out from the venous fistula access to the arterial fistula outlet. Suitable indicators are, for example, the concentration of chemical substances, such as the concentration of dyes, oxygen, urea, sodium chloride, dextrose, etc., or the temperature, for example in the so-called thermodilution process. An indicator is preferably added on the side of the venous access to the fistula, and an indicator measurement, for example a concentration measurement of an indicator substance or a temperature measurement, is carried out on the side of the arterial fistula outlet.

Preferably, the indicator with temporally variable concentration curve or with temporally variable temperature profile, particularly preferably added as a bolus on the venous side and preferably an indicator concentration curve, eg the concentration of an indicator substance or the temperature profile over time, measured on the arterial side. If there is no local recirculation, the indicator concentration curve, ie the dilution curve, on the arterial side will be a largely one-way curve. Such a dilution curve in the arterial-side indicator concentration curve with no local recirculation in the fistula (referred to herein as the "regular dilution peak" or "regular dilution curve") is expected about one minute after indicator addition on the venous side. The presence or presence of a second dilution peak prior to the regular dilution peak (referred to herein as the "local dilution peak" or "local dilution curve") indicates the presence of local recirculation, as described herein, for example Connection with the method according to the invention for determining the local fistula volume is described (see also Figure 2b, Ai _oka i: recirculation flow, Areguiar: regular systemic blood flow through the cardiopulmonary system). This second local dilution peak in the presence or presence of local recirculation usually occurs within seconds, for example between 0.5 and 15 seconds, after indicator addition (eg bolus addition). When local recirculation occurs, the measured dilution curve can be broken down into several, eg 2, partial curves, the local dilution curve and the regular dilution curve. The division can be carried out, for example, by means of local extreme values or by means of fit algorithms (eg Levenberg-Marquardt algorithm).

Preferably, according to the invention, the occurrence of the local recirculation by dilution measurement, preferably by thermodilution measurement, is preferably determined by the venous fistula access to the arterial fistula outlet, the occurrence or presence of a second local dilution peak (ie a second local dilution curve or local partial curve) in addition to the regular dilution peak (ie the regular dilution curve or regular sub-curve), the occurrence or presence of local recirculation in the fistula indicates. Thus, preferably, a bimodal dilution curve, with preferably a regular peak at about one minute after indicator addition and a local peak a few seconds after indicator addition, indicates the presence of local recirculation. Then, the volume flow of the extracorporeal blood flow Q _{D is} higher than the volume flow of the extracorporeal blood flow Q _D0 , in which just no local recirculation occurs. Preferably, the indicator concentration profile on ar ^¬ terieller side at preferably kept constant, extra-corporeal blood ^¬ flow during a given time interval after indication addition is, for example after Boluszugabe measured. A preferred time interval for the measurement of the indicator concentration profile is between one and five minutes, more preferably between one and two minutes, eg 1, 1.5, or 2 minutes, after indicator addition on the venous side. The measurement is preferably started shortly before or with indicator additions.

In order to determine the volume flow of the extracorporeal blood flow at which no recirculation is occurring (QDO), ie in which just no second local dilution peak in the indicator concentration curve is recognizable, at least one dilution measurement is preferably carried out as described above. In this case, a volume flow of the extracorporeal blood flow Q _D is preferably set at which local recirculation takes place in the fistula, which therefore lies above the volume flow Q _D0 . Such a value can be determined, for example, based on empirical values and / or test measurements, if necessary iteratively. For example, the presence of local recirculation may be recognized by the presence of a second local dilution curve or local sub-curve as set forth above.

For this purpose, more than one dilution measurement is preferably carried out as described above, eg 2, 3, 4 or more dilution measurements, preferably each dilution measurement being carried out at another volume flow Q _D (or Q _D x) which is preferably kept constant during the measurement. which is preferably also above the volume flow Q _D o (which, as stated above, can be recognized from the fact that the dilution curve has a bimodal course). This ensures that each indicator concentration course has two dilution peaks, a local dilution peak, and a regular dilution peak. Thus, for each volume flow of extracorporeal blood flow Q _D x receive local Dilutionsgipfel, the area Aio _k aix proportional ^¬ proportional to the local recirculation flow in the appli ^¬ ed extracorporeal blood flow Q _D x. Thus, the volume flow of the ext rakorporalen blood flow may now, for example by extrapolation be determined at which just no local recirculation occurs (Q _D o) that is, the surface of the second local Dilutionsgipfeis "0" is straight. From the volume flow Q _D0 can then as set forth above, the fistula flow Q _S o or as explained below, the local fistula volume Vi _oka i or the entire fistula volume V _F i _Ste i are determined.

Thus, preferably the volume flow of the extracorporeal blood flow Q _D o (in which just no local recirculation occurs) by a method comprising the following

Steps to Determine: (i) Dilution measurement from venous fistula access (6) to arterial fistula exit (7) for extracorporeal blood flow, where local recirculation occurs, (ii) determination of a regular dilution curve (or a regular sub-curve of the dilution curve) and one local dilution curve (or a local sub-curve of the dilution curve) and thus preferably determination of a bimodal dilution curve with local sub-curve and regular sub-curve, and preferably (iii) determination of the volume flow QDO by evaluating the bimodal dilution curve, preferably by extrapolation of the surface of the local dilution curve the value "0", preferably the

Steps (i) and (ii) are repeated at least once, preferably at a further volume flow of the extracorporeal blood flow, which is also in a region in which local recirculation takes place. Preferably, step (iii) comprises the division of the dilution curve into a local and a regular fraction, so that preferably the local dilution curve (and thus the local recirculation) is not covered by the regular dilution curve (and thus the cardiopulmonary recirculation). This can be done as described below eg by using the superposition principle. It is thus particularly preferred that in the method according to the invention the volume flow of the extracorporeal blood flow at which just no local recirculation occurs (QDO) is determined by an evaluation of the indicator concentration course, preferably a zweigipfligen indicator concentration course in a dilution measurement, as described above. The division into the partial curves of the dilution curve can be carried out, for example, by means of local extreme values or by means of fit algorithms (eg Levenberg-Marquardt algorithm). The evaluation of the bimodal dilution curve for the determination of Q _D0 has the advantage that the cardiopulmonary recirculation (ie the regular systemic blood flow through the cardiopulmonary system), which can partially overlay the fistula recirculation, is separated from the fistula recirculation, and so a very accurate determination of the occurrence of local recirculation and thus the volume flow QDO can be achieved. Such evaluation and separation can be done, for example, by the application of the superposition principle as described herein. From the very precisely determinable value Q _D o, a very exact value for the fistula blood flow (Q _S o) or a very exact value of the local fistula volume (Vio _ka i) or the total fistula volume (V _Fist ei) can then be calculated as described herein , The values determined by the methods according to the invention are thus not falsified by the superimposition of the cardiopulmonary recirculation.

The devices according to the invention are preferably designed to carry out the methods set forth above for determining the occurrence of the local recirculation and for determining the volume flow of the extracorporeal blood flow Q _D o. Thus, the devices according to the invention preferably comprise means for adding an indicator on the venous side, for example a bolus of an indicator. Furthermore, the devices preferably comprise means for indicating on the arterial side an indicator concentration course, such as the course of an indicator substance concentration or the Temperature course to measure, for example, a temperature sensor. Furthermore, the devices according to the invention preferably include an evaluation device in order to be able to detect the occurrence of a second local dilution trigger in the indicator concentration curve. For this purpose, for example, the indicator concentration can be measured over a certain period of time, eg over 1, 2, 3, 4, 5 minutes, as described above, and it can be determined whether several dilution peaks (ie dilution curves), eg two dilution peaks, during the measured Time interval of eg 2 minutes are. The evaluation device can be set up, for example, to detect the occurrence or presence of a second local Dilutionsgipfeis or a zweigipfligen dilution curve by the determination of local extreme values or by fit algorithms (eg Levenberg-Marquardt algorithm). The evaluation device is preferably suitable for this purpose and thus set up by extrapolation of the surface of the local Dilutionsgipfeis to the value "0" the volume flow of extracorporeal blood flow, at the just no recirculation occurs Q _D o, too mittein.

The object of the present invention is also achieved by a method for determination of the local volume of a fistula io _k i and / or the total volume of a fistula V _F i _St ei for dialysis treatment by means of a dialysis machine, said fistula an arterial Fistelabgang and a venous Fistula access, comprising the steps of: adjusting the volume flow rate of extracorporeal blood flow Q _D in the dialysis machine to a value above the value of a volume flow Q _D0 , at the first local recirculation occurs in the fistula; Conducting a dilution measurement from venous fistula access to arterial fistula exit and determination of a regular dilution curve and a local dilution curve; Determining the value of the local mean transit time MTTiokai of the local dilution curve; Calculate local fistula volume V _local between arterial fistula exit (7) and venous fistula access (6). Preferably, the volume flow Q _D o as generally set out above or determined for the method for determining the Fis ^¬ telblutflusses determined, eg by changing the volume flow of the extracorporeal blood flow Q _D in the dialysis machine to the occurrence of local recirculation in the fistula and determining the Value of the volume flow of extracorporeal blood flow Q _D in the dialysis machine when local fistula recirculation occurs as QDO value. The occurrence of local recirculation is preferably as stated above, preferably determined by the evaluation of an indicator concentration curve, preferably a bimodal indicator concentration curve. wherein the occurrence of a second local dilution peak next to a first regular dilution peak indicates the occurrence of local recirculation.

Preferably, in addition to the value of MTTi _oka i, the value of the area Ai _oka i of the dilution curve is also determined. The local volume of a fistula or local shunt volume Vi ₀ _ _ka i is the volume of the fistula between the arterial fistula exit and the venous fistula access. The total volume of a fistula or the entire shunt volume includes the volume of the vascular system from the junction of the main body artery (aorta) to the arterial shunt outlet, the volume of the vascular system from the venous shunt access to the junction with the central venous system and the local shunt volume. The adjustment of the volume flow of the extracorporeal blood flow Q _D in the dialysis machine preferably takes place via the activation of a pump. By means of this pump, the volume flow in the dialysis machine can be set to a predetermined value via the delivery rate or the delivery rate of the pump. Thus, the extracorporeal blood flow Q _{D is set} to a predetermined value. This value is preferably set via a volume flow Q _D o at which local recirculation occurs in the fistula for the first time. At such a value can be assumed that because of the increased volumetric flow and thus the increased extracorporeal blood flow Q _D in the dialysis machine which this extracorporeal blood flow Q _D went to ^¬ at the venous Fistelzugang to a local recirculation in the fistula leads, that is, parts of the Extracorporeal blood supplied at the venous fistula access is returned directly to the arterial fistula outlet via the local fistula, while only a portion of the blood supplied during venous fistula access is passed on into the venous vascular system.

Below this set volume flow, a dilution measurement is now carried out with an indicator (for example, dye or temperature). In this dilution measurement, for example, a bolus is entered on the side of the venous fistula access, and the corresponding concentration profile at the arterial fistula outlet is recorded and evaluated.

The following are preferred for the indicator dilution

Relationships.

The indicator dilution formula is:

The constant is preferably dependent on the chosen definition of indicator and concentration.

For dye dilution, the indicator is dye with the SI unit "kg". The area is formed in the concentration (SI unit kg / m ³ ) time diagram.

For thermodilution the indicator is cold energy with the SI unit "Joule". The area must be the time integral of the energy density [J / m ³ ].

With the abbreviations:

c _b : specific heat capacity of the blood [J / (kg K)]

ro _b : blood density [kg / m ³ ]

AT _b : (blood base temperature - blood temperature) [K]

Ci: specific heat capacity of the indicator [J / (kg K)] roi: indicator density [kg / m ³ ]

Vi: indicator volume [m ³ ]

ΔΤι: (blood base temperature indicator temperature) [K]

The thermodilution formula is then

If the cold is introduced, for example, by cooling the Dialyseblutf1, then the

In such a dilution measurement, a dilution curve is determined as a result of the bolus added correspondingly at the venous fistula access. Since local recirculation was forced at the same time, in addition to a regular dilution curve (without local recirculation), a local dilution curve Ci ₀ kai will also be present which represents the proportion of the blood or injected bolus that is not present at the venous fistula access the venous vasculature was transported via the local shunt directly back to the arterial fistula exit. At this higher delivery rate Q _D than the limiting case Q _D0 , this local dilution curve will occur in addition to the regular dilution curve. This local dilution curve has a local maximum and always occurs well before the regular maximum of the regular dilution curve. As the delivery rate increases, the local maximum becomes higher and appears sooner. The local mean transit time is preferred over

calculated

Particularly preferably, MTTi _oka i is approximately estimated by the value of the time of the local maximum of the local dilution curve. With the help of MTTiokai the local shunt volume or the local fistula volume Viokai can be calculated. This is preferably done by multiplication of

TTiokai with the local shunt volume flow. It can also be the entire shunt volume or total fistula volume

Vristei be calculated. This can be done in accordance with an electrical equivalent circuit, as shown for example in Figure 3. In a further embodiment of the present invention, the local fistula volume Vi _oka i is calculated according to the following formula:

Qio _k ai (parallel to the dialysis machine flowing) blood flow through the local fistula. Qiokai is preferably determinable by solving a system of equations with the following four unknowns:

Qiokai: the blood flow through the local fistula;

Qreguiai: the proportionate blood flow through the heart or the blood flow from the venous fistula access to the central veins;

Ireguiar - the proportion of an indicator used in a dilution measurement (for example, the temperature of the blood in a thermodilution measurement) that reaches the measurement site via the heart; Iiokai: the proportion of the indicator that travels a short distance backwards across the shunt to the measuring point of the dilution measurement without flowing through the heart.

The equation system is:

Cardiac the prior art measured from a measurement without local recirculation of cardiac output (measured for example narrators a reference thermodilution measurement with the indicator ^un _re d with the time integral A feren _Z on the measured Diluti- onskurve) is. Particularly preferably, the CO is determined directly in a previously known manner from the dilution curve c _reg uiar from a measurement with local recirculation. Most notably Preferably, two measurements are carried out with different local recirculations.

Areguiar is the area under the dilution curve c _re guiar (see Fig. 2b) and Aiokai is the area under dilution _curve c ₁₀ kai (see Fig. 2b). The dilution curves c _reg uiär and Ciokai are preferably determined from a dilution measurement course or indicator concentration curve c (t), which is measured with a dialysis flow Q _D at which local recirculation occurs. With a stable circuit, the CO in this measurement is approximately equal to the CO from the reference measurement, preferably at a short time interval. Due to the recirculation, the indicator concentration curve on the arterial shunt side shows two peaks. The first peak is caused by local blood flow. The second peak mainly from the regular systemic blood flow through the cardio-pulmonary system. The measured concentration curve c (t) with recirculation is preferably divided into a regular concentration curve Creguiar (t) and a local concentration curve c _loka i (t). The local concentration curve Ciokai (t) is preferably obtained by fitting (eg Levenberg-Marquardt Fit) a function in the range from the indicator addition to after the first peak and before the second peak. The regular course is preferably obtained from the difference c _re guiar (t) = c (t) - ciokai (). By integrating the concentration curves over time, the areas Ai _oka i and A _reg uiar are obtained.

I total is the total amount of indicator that has been added to the cycle. In the case of thermodilution: the cooling supplied to the blood (amount of cold). The amount of cold is calculated from the blood flow passing through the radiator multiplied by the blood temperature drop in the radiator. The two parts local and regular are considered independently according to the superposition principle. The introduced indicator I _ge together = Iiokai + Ireguiar shares correspond the blood flow Q _D = Qiokai + Qs in the ratio Iiokai / Iregu- lar = Qlocal / Qs.

For Qiokai, after solving the equation system,

.

tems:

From this it is also possible to calculate the ratio of area A _reg uiar to area Aio _k ai: and if

I total = Ireferenz selected:

Furthermore, the following equations can be used, for example to determine Q _s and / or Q _D :

Q _{D is} the extracorporeal blood flow in the dialysis machine and

Q _{s is} the blood flow through the fistula before the arterial fistula exit and after venous fistula access.

In this way, the difference flow Qiokai between the extracorporeal blood flow Q _D in the dialysis machine and the blood flow through the fistula Q _s before the arterial fistula outlet and after the venous fistula access is determined. Qiokai is then multiplied _locally with the corresponding mean mean transit time (MTT). In this way one obtains the local fistula volume V _locally . In a further embodiment of the present invention, the entire Fistelvolumen V _F i _St is additionally ei calculation ^¬ net. In the calculation of the total fistula volume V _Fist, the local fistula volume Viokai is particularly preferably related to the remaining vascular systems on the venous and arterial side. This can be used to directly determine the total fistula volume.

In a further embodiment of the present invention, the total fistula volume V _Fiste i is calculated according to the following formula:

k is a correction value;

Qiokai (parallel to the dialysis machine flowing) blood flow through the local fistula.

With this formula, the pressure ratio of the central arterial blood pressure AP and the central venous blood pressure CVP is particularly preferably set in relation to the pressure prevailing at the arterial fistula outlet (PI) or the pressure prevailing at the venous fistula access (P2). By this ratio it can be estimated how large the total fistula volume V _Fist ei is.

Alternatively, the extrapolated area ratio of local curve and regular curve can also be used for the calculation. For example, if the indicator is well mixed then the total amount of indicator is divided according to the ratio of local to regular blood flow. The transported indicator subsets are obtained by integration of the concentration over time from 0 to oo. Illustratively, these are the extrapolated areas under the curve parts of the regular dilution curve and the local dilution curve. The pressure ratio (PI - P2) / (AP - CVP) used in the formulas can preferably also be estimated on the basis of the geometric conditions. In general, the pressure ratio is approximately equal to the aspect ratio in the shunt or in the fistula. Of course, the method can also be used with walls ^¬ ren indicators as cold or heat. In this way, a more accurate determination of the shunt volume is possible, whereby only one arterial temperature sensor is required when working with the indicators of cold or heat.

In a further embodiment of the present invention, the occurrence of local recirculation in the fistula is determined by the detection and evaluation of a modulation of a physical or chemical characteristic, in particular a characteristic such as the temperature of the blood or the concentration of a substance (eg sodium chloride, dextrose, oxygen , Urea) in the blood before and after the dialyzer. In this way it is possible to determine the local recirculation by means of a thermodilution solution or else by measuring the concentration of a substance in the dialysis fluid which can also be detected in the blood and whose concentration course allows conclusions to be drawn as to the occurrence of local recirculation.

The object of the present invention is further achieved by a device for determining the fistula flow of a fistula for the dialysis treatment with a dialysis fluid by means of a dialysis machine, comprising a conveyor for changing the volume flow of extracorporeal blood flow Q _D in the dialysis machine, a measuring device for detecting the occurrence of local recirculation in the fistula, a storage device for detecting the value of the volume flow of the extracorporeal blood flow Q _D0 in the dialysis machine when local recirculation occurs in the fistula as a first value and an evaluation Direction for calculating the fistula flow of the fistula from the first value.

The conveyor device for varying the volume flow of the extracorporeal blood flow Q _D in the dialysis machine is be ^¬ vorzugt a pump. To the pump is preferably a control ^{¬ device} for changing the flow of the pump added. This control device is preferably controlled in such a way that it permits a measurement for predetermined flow rates, with which it is preferably determined whether a local recirculation occurs. It is particularly preferable to determine to what extent a local recirculation occurs. By means of this device for changing the volume flow, the volume flow in the dialysis machine is preferably infinitely adjustable. It is also conceivable that the volume flow is gradually adjustable.

As a measuring device for detecting the occurrence of local recirculation in the fistula, a device for checking the occurrence of local recirculation on the basis of thermodilution is preferably used. This device for detecting the occurrence of local recirculation can also function by evaluating preferably chemical, particularly preferably physical parameters, in particular a parameter such as concentration of a substance, for example sodium chloride, dextrose, oxygen or urea, preferably in the blood before and after the dialyzer and / or in the dialysis fluid. Preferably, a memory device for detecting the value of the volume flow of the extracorporeal blood flow Q _{D is provided} in the dialysis machine when local recirculation occurs. In this storage device, this limit value of the volume flow of the extracorporeal blood flow Q _{D is} preferably stored as the first value. It can be a volatile memory, random access memory or permanent memory. The value in the memory device is preferably rewritten over and over again with the current value. wrote. Particularly preferably, the value can be stored in the memory device together with further data relating to the dialysis, such as personal data, date time data, type of dialysis machine, time of treatment, etc. In this way, it is preferably possible for a person the quality of To detect fistula perfusion over a longer period of time and thus be able to detect changes in the fistula in advance. Thus, for example, it is possible to determine fistula quality for a particular fistula by measuring at different times - such as different days on which a dialysis treatment is performed - and thus to be able to make predictions as to when the fistula quality falls below a predetermined one Quality will fall off. Particularly preferably, in addition to this first value of the extracorporeal blood flow Q _D , the fistula flow is also stored or only the fistula flow is stored.

In the evaluation device for calculating the fistula flow of the fistula from the first value, a processor or a computing device is preferably provided, which determines the fistula flow of the fistula on the basis of the determined first value. Particularly preferably, the first value is adopted as a fistula flow. Further preferably, the first value is multiplied by a factor which is smaller than 1 as a fistula flow. Most preferably, the first value is multiplied by a factor between 0.7 and 0.9, more preferably 0.8, in order to establish the fistula flow. In a further embodiment of the present invention, a device is provided which further comprises a device for determining the central arterial blood pressure, a device for determining the central venous blood pressure, a device for determining the pressure at the arterial fistula outlet and a device for determining the pressure at the venous Includes fistula access. Preferably, the evaluation device is also for determining or calculating the value of the area Aiokai and / or the local mean transit Time MTTio _k ai the local dilution curve established, for example by a digital and / or analog integrator. The device for determining the central arterial blood pressure is preferably a conventional measuring device for determining the central arterial blood pressure, such as a device for measuring the arterial pressure in the large artery at heart level, which is often measured at the brachial artery of the upper arm. Particularly preferred here is a device is provided which measures the mean arterial pressure, abbreviated MAD or MAP (from English: Mean Arterial Pressure). This arterial pressure is between systolic and diastolic arterial pressure. It is calculated by averaging the area under the arterial pressure curve. Instead of using a device for determining the central arterial blood pressure, preferably a value can also be preset which is either estimated or determined in advance by measurement. This value can either be specified by the operating personnel or be predetermined by the device itself.

The means for determining central venous blood pressure is preferably invasive, i. over the central venous catheter, measured. It can be determined via a manometer or the height of a column of liquid above the zero point determined by means of a chestnut caliper. Preferably, the central venous pressure can also be preset manually or be predetermined as an estimated value in the device, particularly preferably in the range of 1-10 mmHg.

The device for determining the pressure at the arterial fistula outlet or at the venous fistula access is preferably a pressure sensor which is provided at this corresponding outlet or access. These pressures can preferably also be estimated and predefined as values either manually or directly by machine. In a further exemplary embodiment of the present invention, a device is provided which is set up to use the evaluation device for calculating the fistula flow to determine the fistula flow Q _s o of the fistula from the first value Q _D o according to the following formula:

in which

Qso blood flow through the fistula is when no blood is flowing for dialysis and

k is a correction value.

The object of the present invention is also achieved by a device for determining the local volume of a fistula Viokai and / or the entire volume of a fistula V _Fist egg for dialysis treatment by means of a dialysis machine, the fistula having an arterial fistula outlet and a venous fistula access comprising a delivery device for adjusting the volume flow of extracorporeal blood flow Q _D in the dialysis machine to a value above a delivery speed Q _D0 at which local recirculation occurs for the first time in the fistula; a measuring device for performing a dilution measurement from the venous fistula access to the arterial fistula outlet and determining a regular dilution curve and a local dilution curve; an evaluation device for determining the value of the local mean transit time of the local dilution curve Ciokai and for calculating the local fistula volume Vi _oka i- The conveying device for adjusting the conveying speed of the extracorporeal blood flow Q _{D of} the dialysis machine is preferably the feed pump in the dialysis machine. This value is set to a value above the value of a volume flow Q _D o at which local recirculation of the fistula occurs for the first time.

A regular dilution curve and a local dilution curve Ciokai are determined by means of a measuring device for performing a dilution measurement from the venous fistula access to the arterial fistula outlet. Such a measuring device can be a thermo-dilution device.

An evaluation device for determining the value of the time of the local maximum tiokai of the local dilution curve or the local mean transit time can preferably be a processor or a computer. In addition, this evaluation device is used to calculate the local fistula volume Viokai. In this regard, this evaluation device can in particular include a computing device. In a further exemplary embodiment of the invention, the evaluation device is set up to calculate the local fistula volume iokai according to the following formula:

In a further embodiment of the invention the evaluation device is set up, in addition to calculate the entire Fistelvolumen V _Fis tei.

In a further exemplary embodiment of the invention, the evaluation device is set up to calculate the total fistula volume V _Fist according to the following formula:

k is a correction value;

Qiokai (parallel to the dialysis machine flowing) blood flow through the local fistula. In a preferred embodiment, the present invention relates to a device which is set up to carry out both the method according to the invention for determining the fistula flow of a fistula and the method according to the invention for determining the local fistula volume or the entire fistula volume and thus preferably the device features as described above described united.

The invention will be further explained in the following figures. Hereby shows:

Fig. 1 is a schematic representation of the fistula access in a dialysis treatment;

FIG. 2 a is a schematic representation of a local dilution curve and a regular dilution curve with the

Times tiokai and t _reg uiär the maxima of the corresponding dilution curves;

FIG. 2 b is a schematic representation of a local dilution curve and a regular dilution curve with the

Areas Ai _oka i and A are _governed by the corresponding dilution curves;

3 is a schematic representation of an equivalent circuit diagram for illustrating an exemplary embodiment for determining a factor for determining the local fistula volume and the total fistula volume; and FIG. 4 shows an exemplary embodiment of a device according to the invention

Device for determining the fistula flow of a fistula (5) and for determining the local volume of a local fistula (5 ') Viokai and / or the Total volume of a fistula (5) V _Fist egg for the dialysis treatment with a dialysis fluid by means of a dialysis machine (20). FIG. 1 shows a schematic representation of the fistula inlets and outlets during a dialysis treatment.

A fistula 5 has a venous fistula access 6 and an arterial fistula outlet 7. The area of the fistula 5 between the arterial fistula exit 7 and the venous fistula access 6 is referred to as local fistula 5 '. The arterial fistula outlet 7 is connected to a dialysis machine (not shown) and leads via a conveyor 25 within this dialysis machine the blood in the extracorporeal circuit to the venous fistula access 6 where it is returned to the shunt 5.

The blood flow Q _s comes from the heart to the arterial fistula exit 7. There, it is divided into the flow Q _D flowing through the extracorporeal blood circulation and the blood flow Qiokai flowing through the local fistula 5 '. Both blood flows then return after the venous access to the fistula 6 merged. The total flow, which then flows away from the venous access to the fistula 6 to the heart is referred to as Q _re guiar and is in the normal case with the flow Q _s match.

When the conveyor 25 is operating slowly enough, all of the extracorporeal blood at the venous fistula access 6 is delivered to the shunt 5 and completely transmitted to the venous vasculature of the shunt 5. When the delivery flow of the conveyor 25 exceeds a threshold value, the pressure at the venous access to the fistula 6 is so high that parts of the returned blood are also conveyed directly in the direction of the arterial fistula outlet 7 via the local fistula. In this case one speaks of local recirculation.

In FIG. 2 a is a schematic representation of a local dilution curve and a regular dilution curve with the Times tiokai and t _reg uiar the maximums of the corresponding dilution curves represented.

Such an image is detected when the volume flow in the dialysis machine is higher than a specific threshold value of the fistula inflow and therefore local recirculation occurs. It can be seen that in local recirculation, a second dilution curve appears next to the regular dilution curve, which is smaller than the regular dilution curve and appears earlier. This local dilution curve corresponds to the occurrence of local recirculation and has a maximum at a time tiokai- The regular dilution curve has a maximum at c * reguiar _/ while the local dilution curve i comes on ei ^¬ NEN value of c * ₀ kai. The maximum of the regular dilution curve occurs only after the maximum of the local dilution curve and is referred to here as the time t _reg uiar.

By evaluating these times, which are measured after the injected bolus or by evaluating the corresponding mean transit times, the local shunt volume and the regular shunt volume can be calculated.

FIG. 2 b shows a schematic representation of a local dilution curve and a regular dilution curve with the areas Aiokai and A _reg uiar of the corresponding dilution curves.

As in FIG. 2 a, the areas under the local dilution curve and the regular dilution curve can also be determined and used to calculate the local shunt volume flow and the regular shunt volume flow. For this purpose, the corresponding integrals are particularly preferably formed or measured values are determined at a sampling rate of 200 pieces per second, preferably 1000 per second, and thus the area is calculated. 3 shows a schematic illustration of an equivalent ^¬ diagram for illustrating an embodiment for determining a factor for determining the local Fis ^¬ telvolumens and the entire Fistelvolumens is illustrated.

In this equivalent circuit is shown, as in the case that a delivery rate Q _{D is} selected, which is higher than the limit case Q _D o _/ at the just no local recirculation ^¬ occurs, by comparing the time of occurrence of the local maximum tiokai as be an approximation for the average transition period through ^¬ MTTiokai and the local shunt volume Viokai and the entire shunt volume or volume of the fistula V _Fist ei ^¬ be true. For this purpose, a situation is preferably used, as it is present in the electrical equivalent circuit diagram shown here. In this respect, it can be concluded from the prevailing pressures and flows in the local fistula or the local shunt and the entire vascular system or the entire fistula to the corresponding volumes. The following relationships are used for this:

With tiokai as an approximation for ΜΤΊΊ with

FIG. 4 shows an exemplary embodiment of a device according to the invention for determining the fistula flow of a fistula 5 and for determining the local volume of a local fistula 5 'Viokai and / or the entire volume of a fistula 5 VFistei for dialysis treatment with a dialysis fluid by means of a dialysis machine 20 shown.

The fistula 5 has an arterial fistula outlet 7 and a venous fistula access 6. The area of the fistula 5 between the arterial fistula exit 7 and the venous fistula access 6 is referred to as local fistula 5 '. At the arterial fistula outlet 7 a dialysis machine 20 is connected. This dialysis machine 20 includes, among other things, a conveyor 25 for changing the volume flow of the extracorporeal

Blood flow Q _D in the dialysis machine 20. On the dialysis machine 20 and the venous fistula access 6 is connected. In addition, a measuring device 26 for detecting the occurrence of local recirculation in the fistula is connected to the arterial fistula outlet 7. This measuring device 26 is also set up to perform a dilution measurement from the venous fistula access to the arterial fistula outlet and thus to determine a regular dilution curve and a local dilution curve. The measuring device 26 comprises a storage device 27 for detecting the value of the volume flow of the extracorporeal blood flow Q _D in the dialysis machine 20 when local recirculation occurs in the fistula 5 or the local fistula 5 '. Furthermore, an evaluation device 28 is provided. With the evaluation device 28, the fistula flow Q _S o of the fistula can be calculated. Furthermore, it is possible with the evaluation device 28 to determine the value of the time instant of the local maximum tiokai of the local dilution curve or the value of the area Ai _oka i and / or the value of the local mean transit time MTTi _oka i. Furthermore, it is possible via the evaluation unit 28 to calculate the local Fistelvolumen Viokai and also the entire Fistelvolumen V _Fis TEI

In fistula 5, blood is delivered intracorporeally with a volume flow Q _s . At the arterial fistula exit 7 is a

Part of the blood removed and added to the dialysis machine 20. There, the flow rate of the extracorporeal blood flow is changed via a conveyor 25. At a fixed flow of the conveyor 25 is thus enforced a special extracorporeal blood flow Q _D in the dialysis machine 20. This is preferably kept constant. The blood is then supplied from the dialysis machine 20 to the venous fistula access 6, from where it continues to flow into the venous vessels of the fistula 5.

In order to calculate the fistula flow Q _s o of the fistula 5, the delivery flow of the fistula 5 is now determined by the measuring device 26 for detecting the occurrence of local recirculation in the fistula 5

Conveyor 25 is determined in the first time a local recirculation in the fistula 5 or the local fistula 5 ^Λ occurs. This preferably takes place in that the measuring device 26 carries out individual measurements at different delivery flows of the delivery device 25 and determines the extracorporeal blood flow at which no local recirculation in the fistula occurs at the moment. This extracorporeal blood flow is then used to determine the fistula flow Q _S o, the fistula 5, and thus to allow a quality assessment of the fistula. This value is detected in the memory device 27 and serves as a parameter for describing the quality of the fistula. The evaluation device 28 can then accept this value of the extracorporeal blood flow Q _D in the dialysis machine when local recirculation occurs in the fistula 5 as fistula flow Q _s o of the fistula 5 or by taking into account a factor <1, preferably 0.8 from Qoo, determine this fistula flow Q _S o. This is particularly preferably done according to the formula:

where k is a correction value; Q _D o the dialysis blood flow is when no blood flows through the local fistula;

Qso is the blood flow through the fistula when no blood is flowing for dialysis; In a further embodiment of the evaluation device 28, this can be used to determine the value of the time instant of the local maximum ti _oka i of the local dilution curve. By a corresponding dilution measurement, which is performed by the measuring device 26, a local dilution curve can be determined at a correspondingly high flow rate of the conveyor 25. The evaluation device 28 can then determine the maximum of this local dilution curve tiokai and thus also the value of the time at which this local maximum occurs. The evaluation device 28 is particularly preferably oriented so that it can also determine the local fistula volume Vi _oka i from this local maximum.

In a preferred embodiment, the evaluation device 28 is designed such that it can also calculate the total fistula volume V _Fiste i. In this way, a method and a device for determining the fistula flow of a fistula for the dialysis treatment with a dialysis machine on the one hand and a method and a device for determining the local volume of a local fistula Viokai and / or the entire volume of a fistula V _F i _St egg for dialysis treatment with a dialysis machine provided, where the determination of these values can be done much easier and with less effort than was the case in the prior art.

LIST OF REFERENCE NUMBERS

1 device

5 fistula

5 'Local fistula between arterial fistula exit and venous fistula access

6 venous fistula access

7 arterial fistula exit

20 dialysis machine

25 conveying device for changing the volume flow of the extracorporeal blood flow Q _D in the dialysis machine

26 measuring means for detecting the occurrence of local recirculation in the fistula; to perform a dilution measurement from venous fistula access to arterial fistula exit and to determine a regular dilution curve and a local dilution curve

27 memory device for detecting the value of the volume flow of the extracorporeal blood flow Q _D in the dialysis machine in the occurrence of local recirculation in the fistula

28 evaluation device (a) for calculating the fistula flow Qso of the fistula; (b) for determining the value of the time of the local maximum tio _k ai of the local dilution curve or the value of the area Aio _k ai and / or the value of the local mean transit time MTTio _k ai; (c) for calculating the local fistula volume Vi _oka i

40 Establishment of central arterial blood pressure

41 Device for determining central venous blood pressure

45 Device for determining the pressure at the arterial fistula outlet

46 Device for determining the pressure at the venous fistula access

Claims

claims

1. A method for determining the fistula blood flow of a

Fistula (5) for dialysis treatment by means of a dialysis machine (20), the fistula (5) having an arterial fistula outlet (7) and a venous fistula access (6), comprising the steps of: changing the volume flow of the extracorporeal blood flow Q _D in the dialysis machine (20) until the occurrence of local recirculation in the fistula (5);

Determining the value of the volume flow of the extracorporeal blood flow Q _D in the dialysis machine (20) when local recirculation occurs in the fistula (5) as the first value Q _D o

Calculating the fistula blood flow Q _S o of the fistula (5) from the first value Q _D o

2. The method according to claim 1, characterized in that the changing of the volume flow of the extracorporeal blood flow Q _D in the dialysis machine (20) is an increase in the volume flow of the extracorporeal blood flow Q _D in the dialysis machine (20).

3. The method according to any one of the preceding claims, characterized in that the calculation of the Fistelflus ses Qso of the fistula (5) from the first value Q _D0, the acquisition of the first value Q _D0 as the fistula blood flow Q _S o

4. The method according to any one of the preceding claims, characterized in that the calculation of the fistula blood flow Qso of the fistula (5) from the first value according to the following formula:

in which

QDO is the dialysis blood flow when no blood is flowing through the local fistula (5);

Qso is the blood flow through the fistula (5), if not

Blood for dialysis flows and

k is a correction value between 0 and 1.

5. Method according to claim 1, characterized in that the occurrence of local circulation in the fistula (5) is determined by a dilution measurement from the venous fistula access (6) to the arterial fistula outlet (7) second local dilution curve or local sub-curve in addition to the regular dilution curve or the regular sub-curve indicating the occurrence of local recirculation in the fistula.

6. The method according to any one of the preceding claims, characterized in that the volume flow of extracorporeal blood flow Q _{D0 is} determined by a method comprising the steps:

(i) dilution measurement from venous fistula access (6) to arterial fistula exit (7) in extracorporeal blood flow where local recirculation occurs,

(ii) determining a regular dilution curve or regular sub-curve and a local dilution curve or local sub-curve, and

(iii) Determination of the volume flow Q _D o by extrapolation of the area of the local dilution curve (Aiokai) to the value "0".

7. A method for determining the local volume of a local fistula (5 ') Vio _k ai and / or the entire volume of a fistula (5) V _Fist egg for dialysis treatment by means of a dialysis machine (20), the fistula (5) having an arterial fistula outlet (7) and a venous fistula entrance (6), comprising the steps:

Setting the volume flow of the extracorporeal blood flow Q _D in the dialysis machine (20) to a value above the value of a volume flow Q _D0 at which local recirculation occurs for the first time in the fistula (5);

Performing a dilution measurement from the venous access to the fistula (6) to the arterial fistula outlet (7) and determining a regular dilution curve and a local dilution curve;

Determining the value of the local mean transit time MTTi _oka i of the local dilution curve;

Calculation of local fistula volume Vio _k ai between arterial fistula exit (7) and venous fistula access (6)

8. The method of claim 7, wherein the volume flow of extracorporeal blood flow Q _{D0 is} determined by a method comprising the steps of:

(i) changing the volume flow of the extracorporeal blood flow Q _D in the dialysis machine (20) until the occurrence of local recirculation in the fistula (5);

(ii) determining the value of the volume flow of the extracorporeal blood flow Q _D in the dialysis machine (20) upon the occurrence of local recirculation in the fistula (5).

9. The method of claim 7 or 8, wherein the local fistula volume Vio _k ai is calculated according to the following formula:

in which Qiokai is the blood flow through the local fistula and MTTi _oka i- the mean transit time.

10. The method according to any one of claims 7 to 9, wherein additionally the total fistula volume V _Fis tei is calculated

11. The method of claim 10, wherein the entire Fistelvolumen V _Fis tei is calculated according to the following formula:

where k is a correction value;

Qiokai is the blood flow through the local fistula and MTTi _oka i_ the mean transit time.

12. The method according to any one of claims 1 to 11, characterized in that the occurrence of local recirculation tion in the fistula (5) by the detection and evaluation of a modulation of a physical or chemical characteristic is determined, in particular a characteristic such as the temperature of the blood or the concentration of a substance in the blood before and after the dialyzer

13. Device (1) for determining the fistula blood flow ei ner fistula (5) for dialysis treatment by means of a dialysis machine (20) comprising: a conveyor (25) for changing the volume flow of the extracorporeal blood flow Q _D in the dialysis machine (20) a measuring device (26) for detecting the occurrence of local recirculation in the fistula; a storage device (27) for detecting the value of the volume flow of the extracorporeal blood flow Q _D in the dialysis machine (20) when local circulation in the fistula (5) occurs as a first value and an evaluation device (28) for calculating the fistula blood flow Q _s o the fistula (5) from the first value.

14. Device (1) according to claim 13, further comprising a device for determining the central arterial blood pressure (40), a device for determining the central venous blood pressure (41), a device for determining the pressure at the arterial fistula outlet (45) and a device for Determination of pressure at venous fistula access (46).

15. Device (1) according to one of the preceding device claims, wherein the evaluation device (28) is set up to determine the fistula blood flow Q _S o of the fistula (5) from the first value according to the following formula:

in which

Q _{D0 is} the dialysis blood flow when no blood is flowing through the local fistula and Qso is the blood flow through the fistula when no blood is flowing for dialysis;

k is a correction value.

16. A device (1) for determining the local volume of a local fistula (5 ') Vio _k ai and / or the entire volume of a fistula (5) V _Fist egg for dialysis treatment by means of a dialysis machine (20), wherein the fistula (5 ) has an arterial fistula outlet (7) and a venous fistula access (6), comprising: a conveyor (25) for adjusting the volume flow of extracorporeal blood flow Q _D in the dialysis machine to a value above the value of a volume flow Q _{DO /} at the first local Recirculation occurs in the fistula (5);

A measuring device (26) for performing a dilution measurement from the venous fistula access (6) to the arterial fistula outlet (7) and determining a regular dilution curve and a local dilution curve; an evaluation device (28) for determining the value of the local mean transit time MTTi _ok ai of the local dilution curve and for calculating the local fistula volume Vi _oka i.

17. Device (1) according to claim 16, further comprising: a conveying device (25) for changing the volume flow of the extracorporeal blood flow Q _D in the dialysis machine (20), a measuring device (26) for detecting the occurrence of local recirculation in the fistula ( 5); a storage device (27) for detecting the value of the volume flow of extracorporeal blood flow Q _D in the dialysis machine (20) upon the occurrence of local circulation in the fistula (5) Q _D0 .

18. Device (1) according to claim 16 or 17, wherein the value means (28) is adapted to calculate the local fistula volume Vio _k ai according to the following formula:

19. Device (1) according to any one of claims 16 to 18, wherein the evaluation device (28) is arranged to additionally calculate the total fistula volume V _F i _Ste i.

20. Device (1) according to claim 19, wherein the evaluation device (28) is set up to calculate the total fistula volume vpistei according to the following formula:

in which

k is a correction value.

Qiokai is the blood flow through the local fistula and MTTi ₀ k _a i- the mean transit time.