Apparatus, system and method for a pressure-based detection of a clot

Abstract

The present invention relates to an apparatus for a pressure-based detection of a clot in an extracorporeal blood circuit, wherein the apparatus comprises at least one cyclically operating pump for conveying the fluid located in the extracorporeal circuit and at least one pressure sensor which is arranged to determine the current pressure development over time in the fluid conveyed by the pump in a current conveying cycle of the pump, wherein the apparatus has at least one memory in which at least one reference pressure development is stored which is based on at least one pressure development over time which was determined in a conveying cycle of the pump preceding the current conveying cycle of the pump, and wherein the apparatus comprises at least one evaluation unit which is configured such that it compares the current pressure development with the reference pressure development over a corresponding time.

Claims

1. An apparatus for a pressure-based detection of a clot in an extracorporeal blood circuit, wherein the apparatus comprises at least one cyclically operating pump for conveying the fluid located in the extracorporeal circuit and at least one pressure sensor which is arranged to determine the current pressure development over time in the fluid conveyed by the pump in a current conveying cycle of the pump, wherein the apparatus has at least one memory in which at least one reference pressure development is stored which is based on at least one pressure development over time which was determined in a conveying cycle of the pump preceding the current conveying cycle of the pump, wherein the apparatus comprises at least one sensor for detecting the position of the conveying member or members of the pump, with the sensor being connected to the evaluation unit for a comparison corresponding in time between the current pressure development and the reference pressure development, and wherein the apparatus comprises at least one evaluation unit which is configured such that it compares the current pressure development with the reference pressure development over a corresponding time.

2. An apparatus in accordance with claim 1, characterized in that the evaluation unit or another unit of the apparatus is configured such that it carries out at least one measure when the current pressure development reaches or exceeds the reference pressure development.

3. An apparatus in accordance with claim 2, characterized in that the evaluation unit or the other unit is configured such that as a measure it closes at least one valve located in the extracorporeal circuit and/or stops the pump and/or outputs a signal to the user of the system.

4. An apparatus in accordance with claim 1, characterized in that the pump is pump which has a periodically fluctuating conveying rate so that a cyclic pressure development results in the fluid conveyed by the pump, with provision preferably being made that the pump is a peristaltic pump or a membrane pump.

5. An apparatus in accordance with claim 1, characterized in that the reference pressure development is based on a pressure development phase-shifted with respect to the current pressure development; and/or in that the reference pressure development is based on the pressure development directly preceding the current pressure development and/or on a pressure development further in the past.

6. An apparatus in accordance with claim 1, characterized in that the reference pressure development is formed by a pressure development determined in a preceding conveying cycle of the pump, plus a supplement on this pressure development.

7. An apparatus in accordance with claim 1, characterized in that the extracorporeal circuit has at least one arterial line and at least one venous line; and in that the pressure sensor is arranged in the arterial line and/or in the venous line.

8. An apparatus in accordance with claim 7, characterized in that no clot catcher is arranged in the arterial line or in the venous line in which the pressure sensor is arranged; or in that a clot catcher is located in the arterial line and/or in the venous line.

9. A system comprising at least one blood treatment unit which has the extracorporeal circuit and comprising at least one apparatus for a pressure-based detection of a clot in accordance with claim 1.

10. A system in accordance with claim 9, characterized in that the extracorporeal circuit is provided with at least one connector for connecting the extracorporeal circuit to a patient.

11. A system in accordance with claim 9, characterized in that the blood treatment unit is a hemofiltration unit, a hemodialysis unit, a hemodiafiltration unit, an apheresis unit or an apparatus for medicating.

12. A hose set for use in an apparatus in accordance with claim 1 or for use in a system having at least one blood treatment unit which has the extracorporeal circuit and at least one apparatus for a pressure-based detection of a clot in accordance with claim 1, wherein the hose set forms the extracorporeal circuit or a section thereof, wherein the hose set is provided with at least one connector for connecting the extracorporeal circuit to a patient, and wherein the hose set has an arterial line and a venous line, and wherein no clot catcher is arranged in the arterial line or in the venous line or in either line.

13. A method for a pressure-based detection of a clot, wherein the method comprises the cyclic conveying of fluid from an extracorporeal circuit of a blood treatment unit carried out by at least one pump, wherein in a current conveying cycle of the pump the current pressure development is determined over time in the fluid conveyed by the pump, and wherein this current pressure development is compared with a reference pressure development over a corresponding time which is based on an earlier pressure development over time which was measured in at least one conveying cycle of the pump preceding the current pressure development, characterized in that the pump is operated in the opposite direction to the direction in which it runs during the blood treatment for carrying out the method.

14. A method in accordance with claim 13, characterized in that at least one measure is carried out when the current pressure development reaches or exceeds the reference pressure development.

15. A method in accordance with claim 14, characterized in that the measure is the blocking of the extracorporeal circuit and/or the stopping of the pump and/or the outputting of a signal to the user.

16. A method in accordance with claim 13, characterized in that the extracorporeal circuit has at least one arterial line and at least one venous line; and in that the pressure measurement takes place in the arterial line and/or in the venous line.

17. A method in accordance with claim 13, characterized in that the fluid which is conveyed out of the extracorporeal circuit and whose pressure development is measured is not conducted through a clot catcher.

18. A method in accordance with claim 13, characterized in that the reference pressure development is based on a pressure development phase-shifted with respect to the current pressure development; and/or in that the reference pressure development is formed by a pressure development determined in a preceding conveying cycle of the pump, plus a supplement on this pressure development.

Description

(1) Further details and advantages of the invention will be explained in more detail with reference to an embodiment described in the drawing.

(2) There are shown:

(3) FIG. 1: a very simplified schematic view of a blood treatment unit with an extracorporeal blood circuit;

(4) FIG. 2: a further view of a blood treatment unit with an extracorporeal blood circuit; and

(5) FIG. 3: a view of the pressure development over time for a plurality of conveying cycles.

(6) Figure shows by the reference symbol A1 the arterial patient connection of an extra-corporeal blood circuit through which blood enters into the arterial line A by means of the pump B during the blood treatment. The blood is pumped through this arterial patient connection during the treatment by means of the pump B in the direction of the treatment apparatus D which can be a dialyzer. The treatment apparatus can provide substitution fluid. After the treatment, the blood moves in accordance with the direction of the arrow through the clot catcher C via the venous line V to the venous patient connection A2.

(7) Reference symbol F denotes an electrically actuated clamp by means of which the arterial line A is blockable.

(8) Reference numeral P denotes a pressure sensor which is located between this clamp F and the blood pump B.

(9) An evaluation unit is marked by the reference symbol E which determines from the output signals of the pressure sensor and of an angle of rotation sensor which delivers the output signal a whether a pressure increase is present which could be caused by a clot; in this case it immediately closes the clamp F.

(10) During the reinfusion of blood from the extracorporeal blood circuit which is subsequent to the blood treatment, blood is conveyed back into the patient from the treatment apparatus via the patent connections A1 and A2.

(11) For this purpose, the pump B is operated in a direction (here: clockwise) opposite to the normal direction. This has the result that blood or the substitute fluid is not conveyed as during the treatment from the connection A1 to the pump B, but conversely from the pump B to the connection A1. The blood in the venous line V is likewise conducted back to the patient, and indeed via the connection A2, by means of displacement by a substitution fluid. There is thus no change of the direction of flow at the venous side in comparison with the direction of flow during the blood treatment.

(12) As can be seen from FIG. 1, the clot catcher C is located only in the venous line V. The supply of a clot to the patient through the connection A2 is thus improbable at this side of the extracorporeal circuit. Such a clot catcher is not located at the arterial side, as can be seen from FIG. 1. To ensure that entry of a clot into the patient's blood circulation also does not take place at the arterial side, the method in accordance with the invention is carried out at the arterial side.

(13) The present invention is, however, not restricted to the use of the method in accordance with the invention in the arterial side. Alternatively or additionally, the invention can also be used in the venous side of the extracorporeal blood circuit.

(14) The embodiment in accordance with FIG. 1 describes a conceivable, but very simplified apparatus and mode of operation for the reinfusion.

(15) A detailed description of a possible reinfusion can be found in DE 10 2009 024 606 A1, to which reference is herewith made in full. FIG. 2 shows an embodiment of DE 10 2009 024 606 A1 with reference to which an example for the reinfusion can be described as follows:

(16) Reference numerals 5, 7 denote the arterial (5) and the venous (7) port to the patient. Reference numeral 1 denotes the arterial line and reference numeral 3 the venous line. A dialyzer or another blood treatment unit is denoted by reference numeral 15.

(17) The arterial line 1 is blockable by the hose clamp 9 and the venous line 3 is blockable by the hose clamp 11.

(18) To conduct the blood back into the patient from the extracorporeal blood circuit after the end of the blood treatment, the clamps 9, 11 are opened and the blood pump 13 and the substituate pump 23 are operated. The blood pump 13 rotates clockwise in accordance with FIG. 2 and thus against its conveying direction in which it conveys during the blood treatment and the substituate pump 23 rotates counter-clockwise and thus in its conveying direction in which it also conveys during the blood treatment. Substitution solution is introduced via the line 27. For this purpose, the predilution addition valve 291 of the predilution addition port 29 is. Alternatively or additionally, an addition at a postdilution addition port 31 is also conceivable. The postdilution addition valve 311 is closed in the embodiment shown here.

(19) Due to the operation of the blood pump 13 against its conveying direction which it has during the blood treatment, the blood pump 13 pumps the blood back into the patient during the reinfusion, the blood being located in the section 1 of the extracorporeal circuit between the blood pump and the port 5. The substituate pump 23 conveys substitution fluid through the remaining part of the extracorporeal blood circuit, including the dialyzer 15, and in so doing displaces the blood located in this part. It moves back to the patient via the venous port.

(20) FIG. 3 shows a pressure development with a pressure increase which is measured by the sensor, P at the point in time t.sub.0 and which is caused by a clot.

(21) The time periods t.sub.0-t.sub.1, t.sub.1-t.sub.2, t.sub.2-t.sub.3 etc. each describe the activity period of a conveying element, i.e. a respective conveying cycle, i.e. a conveying period, of the pump B. As can be seen from FIG. 3, the development of the pressure is a decreasing one overall since the mixture of blood and substitute fluid has a blood content which decreases in the course of the reinfusion, with the viscosity of the fluid falling and with a falling pressure being adopted in the system hose with an unchanging conveying performance of the pump.

(22) The method in accordance with the invention starts at the start of the reinfusion, i.e. at the point in time t.sub.0. The pump B conveys from the treatment apparatus D to the patient connection A1. In this respect, a typical pressure arises in the arterial line A which is continuously recorded in the evaluation unit E.

(23) At the point in time t.sub.1, a complete conveying cycle or activity cycle of an individual conveying element was recorded.

(24) The evaluation unit E detects the end of a conveying cycle using the data of the angle of rotation sensor a of the pump B which is mechanically connected to the pump B or which forms an element of the pump B. Alternatively, a detection of the end of a conveying cycle by a detection of the pressure development or by calculation by means of pump speed and the time or the angle of rotation of the rotor and the gear ratio of the gearbox is conceivable and is covered by the invention.

(25) The pressure value recorded in the first conveying cycle, optionally plus a supplement, is defined as an alarm threshold for the next following conveying cycle in the time period t.sub.1-t.sub.2.

(26) In FIG. 1, the measured arterial pressure is denoted by the reference numeral 1, the arterial pressure in the respective preceding roller passage or conveying cycle is denoted by the reference numeral 2 and the threshold value or the alarm threshold is denoted by the reference numeral 3. Reference numeral 3 thus denote the reference pressure development with which the current pressure development 1 is compared.

(27) An alarm threshold 3 is thus now present for the interval t.sub.1-t.sub.2 which is respectively compared with the current pressure 1 in this time interval. The respective current pressure 1, which is typically in the range from 0-150 mmHG, is compared with the alarm threshold 3 which typically lies in the range from 0-225 mmHg.

(28) If the current pressure 1 exceeds the alarm threshold, i.e. the reference pressure development 3, the conveying of the fluid in the arterial line A is stopped immediately by closing the clamp F.

(29) The alarm threshold 3 is calculated by the evaluation unit E such that the pressure is used at the same time within the activity cycle of the preceding conveying element or conveying cycle and is optionally additionally displaced by a factor toward the higher pressure (offset). This factor can be in the range from 5% to 50%. This makes it possible that differences between the two conveying elements do not generate any false alarms.

(30) A negative offset is generally also possible and covered by the invention to adapt the threshold value accordingly on a large drop of pressure between the individual cycles.

(31) The alarm threshold 3 for the interval t.sub.1-t.sub.2 is thus calculated from the pressure development of the preceding interval t.sub.0-t.sub.1 plus a supplement with respect to the embodiment in FIG. 3.

(32) As can furthermore be seen from FIG. 3, the curves 2 and 3 for the time interval t.sub.0-t.sub.1 start offset in time. In order also to be able to define a reference value for this starting range t.sub.0-t.sub.1, the reference value is set in an embodiment of the invention to a fixed value or value development to an experience value from earlier measurements.

(33) The embodiment relates to a hose roller pump having two conveying elements, i.e. having two rollers which are arranged opposite relative to the axis of rotation. The invention is generally not limited to this, but rather covers every cyclically operating pump such as also a peristaltic pump having more than two conveying elements.

(34) The pressure measurement can be carried out in any patient line of the extracorporeal circuit, for example also after the clot filter in the venous line in order to recognize clots which have grown there.

(35) However, the arrangement shown in FIG. 1 with the pressure detection and the clamp in the arterial line is particularly advantageous.

(36) As stated above, some few mmHG are added to the pressure curve from the preceding roller passage or roller cycle in order to fix the actual alarm threshold, i.e. the reference pressure development.

(37) If the measured pressure value 1 is at or above the reference pressure value 3, possible measures which can be considered are e.g. the closing of the clamp F, the stopping of the pump B, the continuation of the reinfusion by means of a method in which a container with substitute fluid is connected to connection A1 and said substitute fluid is subsequently conveyed by the pump B (forward) in the direction of the treatment device, such as the continuation of the reinfusion of only NaCl and the prevention of the backward conveying of the pump B or a combination of these measures.