Method for removing blood from an extracorporeal blood circuit under pressure control and apparatuses

Abstract

A method of removing blood from an extracorporeal blood circuit and/or a functional device, each of which is connectable or connected with a blood treatment apparatus for the purpose of a blood treatment of a patient, after concluding a blood treatment session, the method comprising operating a blood pump in a second conveying direction which is opposite to a first conveying direction of the blood pump which is customary during the blood treatment, and an arterial line section of the extracorporeal blood circuit is or will be connected with a venous line section of the extracorporeal blood circuit.

Claims

1. A method of removing blood from an extracorporeal blood circuit connected with a blood treatment apparatus after concluding a blood treatment of a patient, the method comprising: operating a substituate pump of the blood treatment apparatus at a feed rate to introduce a substituate liquid into the extracorporeal blood circuit at a location of a pre-dilution valve, the extracorporeal blood circuit comprising an arterial line in which, during the blood treatment of the patient, blood from the patient flows toward a blood treatment device and a venous line in which treated blood from the blood treatment device flows back toward the patient; and while operating the substituate pump to introduce the substituate liquid into the extracorporeal blood circuit, operating a blood pump of the blood treatment apparatus at a feed rate in a second conveying direction to convey blood within the extracorporeal blood circuit, the second conveying direction being opposite to a first conveying direction in which the blood pump is customarily operated during the blood treatment, and wherein the blood pump is a roller pump and the feed rate of the blood pump is regulated at 75% to 90% of the feed rate of the substituate pump such that blood clots, that may have formed in the extracorporeal blood circuit between the pre-dilution valve and the blood treatment device during the blood treatment of the patient, are prevented from entering the venous line, wherein the feed rate of the blood pump and the feed rate of the substituate pump during the removal of blood from the extracorporeal blood circuit are monitored or controlled or regulated by determining a difference between an actual feed pressure of the blood pump and a target feed pressure of the blood pump, and by increasing the feed rate of the blood pump based on the determined difference between the actual feed pressure of the blood pump and the target feed pressure of the blood pump, and wherein the actual feed pressure of the blood pump is measured or calculated when a pre-determined rotation angle of a pump rotor of the blood pump is reached.

2. The method according to claim 1, wherein the feed rate of the blood pump is 80% to 84% of the feed rate of the substituate pump.

3. The method according to claim 1, wherein the extracorporeal blood circuit is partially formed by a blood cassette.

4. The method according to claim 1, wherein the blood treatment device is a dialyzer.

5. The method according to claim 1, wherein the feed rate of the blood pump is limited to 90 to 110 ml/min.

6. The method according to claim 5, wherein the feed rate of the blood pump is set by a user.

7. The method according to claim 1, further comprising measuring the actual feed pressure of the blood pump using an arterial pressure sensor of the blood treatment apparatus.

8. The method according to claim 1, wherein the feed rate of the blood pump and/or the feed rate (Q5000) of the substituate pump is not further increased after the actual feed pressure has reached or exceeded the target feed pressure, wherein the target feed pressure is determined as follows:
P_art,target=a*P_art,max where: P_art,target is the target feed pressure; a is a constant between 0.85 and 0.95; P_art,max is a pre-set or specified measurement range limit or an admissible maximum value for a pressure measured by an arterial pressure sensor.

9. The method according to claim 1, further comprising: increasing the feed rate of the substituate pump according to the formula:
Q5000_future=Q5000_actual+((P_art,target)(P_art,scan))*b; where: Q5000_future is a feed rate of the substituate pump which is to be set henceforth to a point of time t_future; Q5000_actual is an actual feed rate of the substituate pump at a point of time t_actual, which is to be replaced by Q5000_future and precedes this temporally, wherein t_actual comes before t_future; t_future may be denoted as t(x+1) and t_actual as t(x); P_art,target is a pre-set target value which should be detected by an arterial pressure sensor; P_art,scan is a pressure value which is measured by the arterial pressure sensor during adapting of the actual feed rate Q5000_actual; and b is a constant between 0.10 and 0.15.

10. The method according to claim 1, further comprising: decreasing the feed rate of the substituate pump when the actual feed pressure of the blood pump reaches the target feed pressure of the blood pump or exceeds it, according to the formula:
Q5000_future=Q5000_actual+((P_art,target)(P_art,scan))*c; where: Q5000_future is a feed rate of the substituate pump which is to be set henceforth to a point of time t_future; Q5000_actual is an actual feed rate of the substituate pump at a point of time t_actual, which is to be replaced by Q5000_future and precedes this temporally, wherein t_actual comes before t_future; t_future may be denoted as t(x+1) and t_actual as t(x); P_art,target is a pre-set target value which should be detected by an arterial pressure sensor P_art,scan is a pressure value which is measured by the arterial pressure sensor during the adapting of the actual feed rate_Q5000_actual; and c is a constant between 0.20 and 0.30.

11. The method according to claim 1, further comprising: stopping the blood pump before substituate liquid is introduced into the venous line of the extracorporeal blood circuit at a venous addition point or before substituate liquid reaches a point at which fluid from the venous line and fluid from the arterial line meet.

12. The method according to claim 1, further comprising: stopping the substituate pump before substituate liquid is introduced into the venous line of the extracorporeal blood circuit at a venous addition point, or before substituate liquid reaches a point at which fluid from the venous line section and fluid from the arterial line meet.

13. The method according to claim 1, further comprising: checking a connection of an arterial needle connection of the extracorporeal blood circuit with a venous addition point of the extracorporeal blood circuit.

14. The method according to claim 13, wherein checking the connection comprises: creating a pressure balance or compensation; detecting a diastolic patient pressure; and building up a negative pressure by operating the blood pump in the first conveying direction.

15. The method according to claim 13, wherein the venous addition point of the extracorporeal blood circuit leads into the venous line upstream of a blood chamber and upstream of a clot catcher.

16. A blood treatment apparatus control device arranged and/or configured to execute the method according to claim 1.

17. A computer program product with a program code saved on a machine-readable medium for causing a blood treatment apparatus to carry out the method according to claim 1 when the computer program product runs on a computer.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Hereafter, embodiments of the present invention are exemplarily described with reference to the appended figures. It applies that:

(2) FIG. 1 shows in simplified illustration a medical functional device with an extracorporeal blood circuit, which may be cleared of blood using methods described herein.

(3) FIG. 2 shows the progress of pressure and volume over a period of time which may occur or that may be measured while performing exemplary embodiments of methods described herein using an arrangement shown in FIG. 1.

DETAILED DESCRIPTION

(4) FIG. 1 shows a schematically simplified functional device 1000 with an extracorporeal blood circuit 2000 connected herewith.

(5) The extracorporeal blood circuit 2000 comprises or is connected with a blood treatment device 3000, e.g., a blood filter or dialyzer.

(6) A blood treatment apparatus represented in FIG. 1 shows devices used to carry out the methods described herein to automatically completely or mostly reinfuse blood contained in the extracorporeal blood circuit 2000. The blood treatment apparatus comprises a blood pump 4000 and a second conveying device 5000. Both the blood pump 2000 and the second conveying device 5000 convey fluid through sections of the functional device 1000 and of the extracorporeal blood circuit 2000. The functional device 1000 is exemplarily a blood cassette.

(7) Indicated is a connection diagram as well as flow direction, specified by arrows, of blood and substituate (as an example a second fluid) during removal of blood with a simultaneous reinfusion of the blood. The sole double arrow describes a split of the substituate flow in two partial flows

(8) The extracorporeal blood circuit 2000 comprises an arterial line section 1 as well as a venous line section 3.

(9) The arterial line section 1 comprises a first section. The first section is in the example of FIG. 1 exemplarily embodied as an arterial needle connection 5.

(10) The venous line section 3 comprises a second section. The second section 3 is embodied in FIG. 1 as a venous addition point 7 of the functional device 1000.

(11) The arterial line section 1 comprises an arterial pressure sensor which is coupled to the functional device 1000 at the location denoted with reference numeral 9 without being itself part of the functional device 1000. This pressure sensor serves, amongst others, to measure the pressure or to determine pressure drop during an optional connections test. It is arranged in the arterial line connection 1 of the extracorporeal blood circuit 2000.

(12) The arterial line section 1 comprises an arterial clamp 11.

(13) The arterial line section 1 comprises an arterial septum 13, here, optionally in the shape of an addition device.

(14) The venous line section 3 comprises a venous air bubble detector/optical sensor 15.

(15) The venous line section 3 comprises a venous clamp 17.

(16) The venous line section 3 comprises a venous needle 19 on a venous patient connector 21.

(17) A venous septum 23, here optionally in the shape of an addition device, is arranged between the blood treatment device 3000 and the location of its connection with the section of the extracorporeal blood circuit 2000 present on the functional device 1000.

(18) The functional device 1000 comprises a check valve 24 which allows a fluid supply in a direction shown by means of an arrow in FIG. 1 through the venous addition point 7 into the functional device 1000 and into the venous line section 3, however it prevents a flow out of the venous line section 3 through the venous addition point out of the functional device 1000.

(19) For adding heparin into the line interior of the extracorporeal blood circuit 2000 during an extracorporeal blood treatment, the extracorporeal blood circuit 2000 is connected with a heparin syringe 25 via a corresponding port of the functional device 1000.

(20) The arterial line section 1 comprises an arterial air bubble detector/optical sensor 27.

(21) During the blood treatment, the extracorporeal blood circuit 2000 is, e.g., as is shown in FIG. 1 in the form of a tube system, connected with the vascular system of the patient via two needles (in the case of a double-needle dialysis). For performing the blood treatment, the extracorporeal blood circuit 2000 is filled with blood of the patient and this blood flows through the extracorporeal blood circuit 2000 during the treatment.

(22) Hereafter, removal of blood from the extracorporeal blood circuit by using the venous addition point 7 of the functional device 1000 is described. In the herein described example of an embodiment of the method being executed by the machine, while removing blood, there is a concurrent reinfusion of this blood.

(23) The method may be started automatically, or manually by the doctor.

(24) For this purpose, in certain embodiments, the arterial patient connector is disconnected from the arterial needle connection 5 after the conclusion of the blood treatment and connected in fluid connection with a port of the blood cassette, here the venous addition point 7. As may be taken from the blood cassette shown in FIG. 1, the venous addition point 7 may lead directly (in other embodiments also indirectly, however) into the venous line section 3 of the extracorporeal blood circuit 2000 upstream from a blood chamber 29 and from a clot catcher 31.

(25) In the example of FIG. 1, the functional device 1000 comprises at the location of the clot catcher 31 or near the latter, in any case downstream thereof, however upstream of the venous air bubble sensor 15, a venous pressure sensor not shown in FIG. 1, which may measure the pressure of the flow of venous blood or fluid passing by. In other embodiments the venous pressure sensor is provided at another suitable location of the functional device 1000 or of the extracorporeal blood circuit 2000.

(26) The venous addition point 7 is in the above-named applications of the Applicant with the publication numbers DE 10 2009 018 664 A1 and DE 10 2009 024 468 A2 each in FIGS. 1 and 2 marked with the reference numeral 37. The venous addition point 7 is in connection with the venous filter line via a check valve.

(27) The user may be prompted towards the end of the blood treatment to disconnect the arterial needle connection 5 from the arterial patient connector (not shown in FIG. 1) and screw the arterial needle connection 5 onto the Luer connector of the venous addition point 7 of the functional device 1000. In order to check whether the connection is made correctly, a connection test may be performed by the blood treatment apparatus automatically or upon request. In doing so, the correct connection of the arterial line section 1 with the venous line section 3 is checked. Directly conveying the blood via the arterial line section 1 into the vascular system of the patient may therefore advantageously be prevented.

(28) The venous line section 3 is in certain embodiments provided with a check valve, which is why the blood pump 4000 cannot draw in liquid from the venous line section 3 in the first conveying direction. It may therefore be expected that during performance of the connection test the pressure in the arterial line section 1 decreases. If the arterial pressure decreases as expected, it can be assumed that the patient is no longer arterially connected, at least that the (manual) arterial (tube) clamp 11 is closed.

(29) If, as is the case in certain embodiments, an arterial pressure alarm during conveying is provided in this stage of the method, an error would advantageously be detected also early on, even without a connection test. Thus, it may advantageously be possible to forego explicitly testing the connection state.

(30) The connection test for detecting whether the arterial line section 1, e.g., the arterial needle connection 5 of the arterial line section 1, is connected with the venous line section 3, e.g., the venous addition point 7, may hereby take place in detail as described hereafter: At first, a pressure balance is created, wherein the blood pump 4000 and the second conveying device 5000 are stopped. The arterial clamp 11 is open.

(31) Using a pressure sensor 9, the diastolic patient pressure is detected. Hereby, a minimum value is saved over 2.5 s, for example. Subsequently, a negative pressure is built up, whereby the venous clamp 17 is opened and by means of the blood pump 4000 conveyed in the first conveying direction The pressure has to drop because of the check valve 24 below the diastolic patient pressure as detected before, e.g., by 50 mmHg within 2.1 s, otherwise the connection test is considered to be failed.

(32) A predilution valve or predilution connection, provided for introducing substituate liquid into the blood line between the blood treatment device 3000 and the blood pump 4000 is opened for removing blood. The substituate line is connected with the pre-dilution connection, so that the second conveying device 5000 can introduce substituate solution into a section of the extracorporeal blood circuit 2000 which is located between the blood pump 4000 and the blood treatment device 3000.

(33) In the embodiment illustrated here, the blood pump 4000 starts, at the same time (simultaneously) at which conveying begins by means of the second conveying device 5000, conveying backwards, i.e. in the second conveying direction at a lower feed rate than the second conveying device 5000. In doing so, the substituate flow is split due to the different feed speeds of the two pumpsin the example of FIG. 1one partial flow of the substituate solution moves towards the blood pump 4000, another partial flow of the substituate solution moves in the direction towards the blood treatment device 3000.

(34) The occurring venous and/or arterial pressures are monitored during this process. The set pump rates or feed rates of the conveying devices (blood pump 4000 and second conveying device 5000) may have a considerable effect on the removal of the blood.

(35) In certain embodiments, it is ensured that the feed rate of the blood pump 4000 is not selected to be too high. Thus, it may advantageously be ensured that the blood is not damaged when it flows through the point of introductione.g., provided with a thinner tube and a check valve. For this, a limitation of the maximum feed rate, for example based on experience from in vitro tests or in vivo tests, is possible or provided.

(36) In some embodiments, a limitation and/or monitoring the pressure drop across the addition point and/or the addition line and the check valve is possible with the aid of the arterial pressure sensor 9 during reinfusion.

(37) When setting the venous reinfusion rate, i.e. the speed at which the blood that is extracorporeally present is conveyed towards the patient via the venous line section 3 of the extracorporeal blood circuit 2000, it is in some embodiments ensured that the part of the extracorporeal blood circuit 2000 which extends from the pre-dilution point or the pre-dilution valve to the venous addition point is not emptied earlier than or before the arterial line section 1 of the extracorporeal blood circuit 2000 is also emptied.

(38) Hereby, in certain embodiments, a further commingling of blood (arterial) and substituate liquid (venous) and, along with this, an unnecessary increase of the reinfusion volume with the known unpleasant consequences for the patient may advantageously be prevented.

(39) As the volumes of the individual line sections of an extracorporeal blood circuit (also denoted as tube set) are known, it is in certain embodiments of the present invention provided to calculate the maximum possible or permissible venous feed rate as the feed rate in the venous line section of the extracorporeal blood circuit 2000. The calculation may be carried out as described above.

(40) The venous feed rate is in some embodiments set by the feed rate Q5000 of the second conveying device 5000 (substituate pump) deducting the feed rate Q4000 of the blood pump 4000. For this purpose, reference is made to the formulas above.

(41) As with such a fixed specification of the volume of the blood treatment device 3000 the arterial line section 1 of the extracorporeal blood circuit 2000 may be emptied earlier or faster than the venous line section 3, it is in certain embodiments suggested to stop the blood pump 4000 before substituate liquid is conveyed across the venous addition point 7.

(42) Such stopping of the conveying by the blood pump 4000 is in certain embodiments possible by the corresponding adjustment of the feed rate of the blood pump 4000, if the above-mentioned volume is known. Waiting for the moment in which the blood pump 4000 may be stoppedwhere applicable advantageously more preciseis also possible considering the signals of the arterial air bubble detector or optical sensor 11if existent.

(43) In some embodiments, the feed rate of the second conveying device 5000 is increased from the time of stopping the blood pump 4000 with the advantage of saving time.

(44) If the volume of the utilized blood treatment device 3000 is known, the feed rate is advantageously set individually to the maximum possible feed rate with each reinfusion. This shortens the period of time the patient and the operating personnel have to spend at the blood treatment apparatus until the completion of this measure, due to the faster removal of blood from the extracorporeal blood circuit 2000.

(45) The type of the utilized blood treatment device 3000 may be set by the operating personnel. Alternatively, the utilized type may be automatically determined by means of certain parameters which can be observed when filling the blood treatment device 3000.

(46) If the volume of the blood treatment device 3000 is known, in some embodiments, the feed rate of the second conveying device 5000 is set such that at the point of introduction of the venous addition point 7 (or at a comparable point in the blood circuit) substituate and blood of the same dilution degree from both line sections 1, 3 meet at the same time.

(47) The blood pump 4000 may subsequently either be stopped; alternatively, it continues to run.

(48) In embodiments in which the blood pump 4000 continues to run, the arterial line section 1 of the extracorporeal blood circuit 2000 is advantageously comparatively flushed better; in embodiments in which the blood pump 4000 is stopped, the blood treatment device 3000 is advantageously comparatively flushed better.

(49) In certain embodiments, the individual setting of the feed rates takes place according to the above-named formula (II) and (III) if necessary.

(50) FIG. 2 shows pressure and volume progresses (y-axis, vertical) over the time (x-axis, horizontal), which may occur or may be measured using the arrangement shown in FIG. 1 while performing an embodiment of the method.

(51) The scale on the left indicates a volume in ml/min for curves Q4000 and Q5000, the scales on the right indicate pressure in mmHg and apply for curves P_art for the arterial pressure progress and P_ven for the venous pressure progress, as well as for P_ven_sm, the calculated smoothed progress of the curve P_ven.

(52) FIG. 2 shows a curve Q5000 which is indicated by the conveying volume of the second conveying device 5000 over the time t or the feed rate Q5000. The curve Q5000 is composed of several curve sections Q5000-1 to Q5000-5.

(53) Q5000 shows the conveying line of the second conveying device 5000 during an optional, so-called free rinsing of the pre-dilution valve 33. The conveying line of the second conveying device 5000 which is applied for this purpose, is, based on 0 ml/min, e.g. 100 ml/min. After completion of this free rinsing, the feed capacity may optionally drop to 0 ml/min. The volume conveyed thereby may be 10 ml for example.

(54) Q5000 indicates the feed capacity during the blood-return or emptying. Q5000 has a purely exemplary increasing course in the form of staircase, which however must not be neither in a form of a staircase nor must it comprise the pitches and heights. Q5000-2 shows the gradually increasing conveying capacity Q5000_actual of the second conveying device 5000 which is being successively increased by the control device according to the above formula II.

(55) The increase of Q5000, i.e. the section Q5000-2, starts at the time t=0.

(56) The progress section Q5000 goes in the present example at a time t=1 over a section Q5000-3 presently further increasing. The duration of the section Q5000-3 is thus T=(t=1)(t=0).

(57) The feed capacity Q5000 of the second conveying device 5000 increases from the time t=1 until reaching a specified maximum feed capacity Q5000-4, presently for example 300 ml/min, again in a staircase form.

(58) The maximum feed capacity Q5000-4 may again be reached in steps or staircase form, as exemplary shown in FIG. 2. It may however be reached in a vertical increase (with reference to FIG. 2) or in some other way.

(59) Starting from the time t=1, an increase of Q5000 without considering the arterial pressure is undertaken. The formulas II and III are not considered any further starting from t=1. The increase takes placed from t=1 regardless of the arterial pressure.

(60) After the maximum feed capacity Q5000-4 has been reached and held, the curve Q5000 drops in its section Q5000-5 at the time t=2 to 0 ml/min. The method is concluded at t=2.

(61) FIG. 2 shows further a curve Q4000 which indicates the feed volume of the blood pump 4000 through the time or the feed rate Q4000. The curve Q4000 is formed of several curve sections Q4000-1 to Q4000-4.

(62) Q4000 shows the set feed capacity andduration during an optional connection test. The applied feed capacity is, based on 0 ml/min, e.g. 25 ml/min. After completion of this connection test the feed capacity may optionally drop to 0 ml/min.

(63) Q4000-2 shows the feed capacity during the blood return or emptying. Q4000-2 shows an exemplary increasing progress in a form of a staircase which however must not be neither in a form of a staircase nor must it comprise the indicated width and heights of the steps. Q4000-2 shows the gradually increasing feed capacity of the blood pump 4000 which stands in fixed relation to the feed capacity of the second conveying device 5000.

(64) The increase of Q4000, i.e. its section Q4000-2, begins at the time t=0.

(65) The progress section Q4000-2 passes over at a time t=1 which is between t=0 and t=1 into a plateau, the section Q4000-3. This plateau may correspond to a specified maximum feed capacity of 100 ml/min by way of example.

(66) The feed capacity of the blood pump 4000 drops at the time t=1 to 0 ml/min. The drop is denoted with Q4000-4. FIG. 2 shows further a pressure progress P_art, its scaling is represented on the right edge of FIG. 2 and namely on the left of both adjacent scales.

(67) The pressure P_art, e.g. measured by the arterial pressure sensor 9 of FIG. 1, increases due to the conveyance by the blood pump 4000 starting from the time t=0. The local maximum values P_art-1, P_art-2 and so on denote, respectively, highest pressure which is measured in certain rotary angle by conveyance with the blood pump 4000 which is embodied as a roller pump. This maximum pressure occurs during the intrusion of the roll of the blood pump 4000 with the pump tubing segment. The maximum value is adjustable as FIG. 2 also shows. The last measured maximum value P_art-1, P_art-2, and so on, respectively, enter into controlling. In this way, a first maximum value P_art-1 which occurs immediately after the begin of the method is initially measured and used in the following example as basis for the calculation as P_art,scan.

(68) The blood pump 4000 generates, design-limited, two pressure pulses per rotation (may be more than two in other designs) which are measured at the arterial pressure sensor 9. An algorithm present in the control device determines, by means of the rotation angle of the pump rotor and of the actual pressure present at the pressure sensor, these maximum pressures P_art-1, P_art-2 and so on respectively, and provides this pressure for further processing as P_art, scan as described above.

(69) The blood return begins at t=0, when the second conveying device 5000 preferably at the same time as the blood pump 4000 begins conveying, optionally with the lowest possible rate (the downward limitation is hereby design-limited), in this case 25 ml/min.

(70) Until the time t=1 both the second conveying device 5000 as well as the blood pump 4000 convey.

(71) Thereby the blood pump 4000 is always regulated such that to convey with only a fraction of the feed rate Q5000 of the second conveying device 5000. The exemplary selected relation in this case is Q4000=Q5000*0.82. This value has proven itself particularly advantageous due to the fact that with it, the passing of blood clots from the entry of the blood treatment device, here as a dialyser, on its blood side in the arterial line section 1 is prevented.

(72) It may therefore be intended that starting from a conveyance Q5000 of the second conveying device 5000 of e.g. more the 122 ml/min, the feed rate Q4000 of the blood pump 4000 is limited to e.g. 100 ml/min.

(73) Following each created positive pressure pulse P_art, scan by the blood pump 4000 which is measured in the pressure sensor 9, the feed rate Q5000 of the second conveying device 5000 is increased. It is increased to an upper point which is determined by the user by means of the maximum measurement range limit of the pressure sensor where a specified pressure limit P_art,target is reached.

(74) Therefore, the pressure in the pressure sensor 9 shall reliably not exceed its upper measurement range P_art,max, here 455 mmHg in the present example. P_art,max is in this example, the pressure value starting from which the pressure sensor releases an alarm due to high pressure. Hence, the regulation target P_art,target for the pressure in the pressure sensor 9 is specified to be 90% of the measurement range*0.9, i.e. around 410 mmHg.

(75) In the example of FIG. 2, the first maximum value for the pressure, namely P_art-1 is about 260 mmHg. If measured to the target value P_art,target of about 410 mmHg (corresponds to 455 mmHg.*0.9), the control difference in this example is now about 150 mmHg.

(76) The feed rate Q5000 of the second conveying device 5000 is increased in the section Q5000-2 as follows:
Q5000_future=Q5000_actual+((P_art,target))(P_art,scan))+0.12*ml/min
Q5000_future is thereby the new feed rate to be determined.
Q5000_actual is the last determined. Q5000_future might therefore also be denoted as Q5000(t=x+1) and Q5000_actual might be denoted as Q5000(t=x).

(77) Should the pressure in the pressure sensor 9 exceed the regulation target P_art,target, the following countermeasures are taken:
Q5000_future=Q5000_actual+((P_art,target)(P_art,scan))*0.24*ml/min

(78) Starting form the time t=1 of FIG. 2, the blood pump 4000 ceases to convey, only the second conveying device 5000 still coveys.

(79) Starting from the time t=1 of FIG. 2, the feed rate Q5000 of the second conveying device 5000, presently purely by way of example, is increased each 0.5 s of 10 ml/min until the maximum flow which is determined by the user in the device is reached. Other values are of course encompassed by the present invention as well.

(80) The progress P_ven is measured by means of the venous pressure sensor, the course P_ven_sm corresponds to the smoothing of the first-mentioned.

(81) TABLE-US-00001 Reference Numerals List Reference numerals Description 1000 functional device 2000 extracorporeal blood circuit 3000 blood treatment device 4000 blood pump 5000 second conveying device 1 arterial line section 3 venous line section 5 arterial needle connection 7 venous addition point 9 (arterial) pressure sensor or pressure measurement 11 arterial clamp 13 arterial septum 15 venous air bubble detector/optical sensor 17 venous clamp 19 venous needle 21 venous patient connector 23 venous septum 24 check valve 25 heparin syringe 27 arterial air bubble detector/optical sensor 29 single needle chamber 29a blood chamber or bubble chamber 31 clot catcher 33 pre-dilution valve P_art P_art-1, -2, -3 maximum value P_art, scan P_ven venous pressure P_ven_sm smoothed progress of the curve P_ven Q4000 feed rate of the blood pump Q4000-1 to Q4000-4 sections of curve Q4000 Q5000 feed rate of the second conveying device Q5000-1 to Q5000-5 sections of curve Q5000