DIALYSIS MACHINE

Abstract

The present invention relates to a dialysis machine having an extracorporeal circuit in which a dialyzer is located which has a chamber on the blood side which is flowed through by blood and a first pressure sensor, which is located upstream of the chamber on the blood side in the direction of flow of the blood, for determining a first pressure value and a second pressure sensor, which is located downstream of the chamber on the blood side in the direction of flow of the blood, for determining a second pressure value, wherein the dialysis machine has first means for determining the pressure difference between the second pressure value and the first pressure value, second means for determining the dynamic viscosity of the blood on the basis of the determined pressure difference, of the blood flow rate through the chamber on the blood side and of one or more characteristic properties of the dialyzer and third means for determining the hematocrit or the hemoglobin value of the blood on the basis of the determined viscosity, and wherein the dialysis machine has a control or regulation unit which is configured such that it sets the blood flow rate and/or the dilution rate and/or the ultrafiltration rate such that the time change of the hematocrit and/or of the hemoglobin value does not exceed a limit value or lies in a desired value range.

Claims

1. A dialysis machine having an extracorporeal circuit in which a dialyzer is located which has a chamber on the blood side which is flowed through by blood and a first pressure sensor, which is located upstream of the chamber on the blood side in the direction of flow of the blood, for determining a first pressure value and a second pressure sensor, which is located downstream of the chamber on the blood side in the direction of flow of the blood, for determining a second pressure value, characterized in that the dialysis machine has first means for determining the pressure difference between the second pressure value and the first pressure value; the dialysis machine has second means for determining the dynamic viscosity of the blood on the basis of the determined pressure difference, of the blood flow rate through the chamber on the blood side and of one or more characteristic properties of the dialyzer; the dialysis machine has third means for determining the hematocrit or the hemoglobin value of the blood on the basis of the determined viscosity; and the dialysis machine has a control or regulation unit which is configured such that it sets the blood flow rate and/or the dilution rate and/or the ultrafiltration rate such that the time change of the hematocrit and/or of the hemoglobin value does not exceed a limit value or lies within a desired value range.

2. A dialysis machine in accordance with claim 1, characterized in that the control or regulation unit is configured such that the ultrafiltration rate is not used to set the change of the hematocrit and/or of the hemoglobin value.

3. A dialysis machine in accordance with claim 1, characterized in that the limit value or the desired value range is fixedly predefined or is determined experimentally.

4. A dialysis machine in accordance with claim 1, characterized in that the properties of the dialyzer comprise the flow resistance of the dialyzer which results with a laminar flow.

5. A dialysis machine in accordance with claim 1, characterized in that the dialyzer chamber on the blood side comprises the lumen of a plurality of capillaries; and in that the properties of the dialyzer comprise the length of the capillaries and/or their inner dimensions and/or their number and/or their shape and/or their wall structure and/or the roughness of the capillary wall.

6. A dialysis machine in accordance with claim 1, characterized in that the third means have a memory in which a relationship between the hematocrit or hemoglobin value of the blood and the viscosity is stored and that the third means are configured such that the hematocrit or the hemoglobin value of the blood is determined on the basis of this relationship.

7. A dialysis machine in accordance with claim 6, characterized in that the relationship is fixedly preset.

8. A dialysis machine in accordance with claim 6, characterized in that the relationship is determined by means of a correction factor on an individual patient basis.

9. A dialysis machine in accordance with claim 6, characterized in that the third means are configured such that the hematocrit or hemoglobin value is determined by interpolation or by extrapolation.

10. A dialysis machine in accordance with claim 1, characterized in that the dialysis machine has means for reading in the characteristic properties of the dialyzer which are in communication with the second means for determining the viscosity.

11. A dialysis machine in accordance with claim 1, characterized in that the first to third means are components of a dialysis machine anyway present so that no additional elements are required to carry out the measures carried out by the first to third means.

12. A dialysis machine in accordance with claim 1, characterized in that the characteristic properties of the dialyzer are obtained by measurement with blood or by measurement with another fluid, in particular by measurement with a flushing liquid.

13. A dialysis machine in accordance with claim 1, characterized in that the dialysis machine has a chamber flowed through by dialysis solution on the dialyzate side and a third pressure sensor, which is located upstream of the chamber at the dialyzate side in the direction of flow of the dialysis solution, for determining a third pressure value and a fourth pressure sensor, located downstream of the chamber at the dialyzate side in the direction of flow of the dialysis solution, for determining a fourth pressure value.

14. A dialysis machine in accordance with claim 1, characterized in that the dialyzer is a hemodialyzer or a hemofilter.

15. A dialysis machine in accordance with claim 1, characterized in that the dialysis machine has a predilution line which opens into the extracorporeal circuit upstream of the dialyzer in the direction of flow of the dialyzer; and in that the dilution rate is the infusion rate of a substitution fluid supplied through the predilution line.

Description

[0055] Further details and advantages of the invention will be explained in more detail with reference to an embodiment shown in the drawing. There are shown:

[0056] FIG. 1: different schematic longitudinal sectional views through different membrane types; and

[0057] FIG. 2: a schematic representation of the dependence of the blood viscosity on the hematocrit.

[0058] The flow resistance on the blood side is measured before the start of the dialysis treatment via the pressure sensors present in the hemodialysis device, i.e. the “calibration” does not take place in the works. This measurement can be carried out automatically during, or also after the priming of the dialysis machine.

[0059] During priming, the measurement takes place e.g. by means of a flushing solution such as a physiological saline solution. After the priming, the measurement takes place by means of the patient's blood.

[0060] There is the advantage in the first case that the patient does not have to be present; however, there is the disadvantage that only the flow resistance is measured using the saline solution, which only represents an approximation for the blood resistance on being flowed through by blood.

[0061] Alternatively to this procedure, the “calibration” can take place at the production site of the dialyzer and a transfer of the result to the dialysis machine can take place.

[0062] The geometry of the dialyzer such as the number of capillaries, their lengths, their inner capillary radius, the design of the membrane (such as the number, the size and the geometry of the pores) and optionally the properties of the materials used (such as the elasticity, hardness, compliance) inter alia enter into the resistance on the blood side.

[0063] It is conceivable that the first and last dialyzers are measured after the production of a lot of dialyzers and the dialyzers of the total lot are provided with the value or mean value of the determined flow resistance (e.g. on an RFID chip, barcode or in another suitable data store). This value can be read in by the dialysis machine for the treatment, preferable before the treatment.

[0064] If the dialyzer has been calibrated in this manner, i.e. if its properties and in particular its flow resistance are known, the dynamic viscosity can be determined by the measurement of the pressure loss over the length of the dialyzer.

[0065] The hematocrit and/or the hemoglobin value can be determined from the viscosity on this basis. Provision can be made to improve the precision of this determination that the blood flow resistance is measured for the individual patient at the start of the treatment and a correction factor is calculated by a comparison with the hematocrit and/or the hemoglobin value known from the laboratory which improves the precision of the blood viscosity and hematocrit curves shown by way of example in FIG. 2 on an individual patient basis.

[0066] The determination of the hematocrit and/or the hemoglobin value can take place using means of the dialysis machine, i.e. no additional elements separately provided therefor are preferably present.

[0067] The concentration of the blood, i.e. the increase in the hematocrit ΔHKT over time takes place constantly in a first approximation with unchanged treatment parameters during the dialysis treatment.

[0068] If the measured hematocrit increases unexpectedly and abruptly or more steeply in a smooth transition, that is if ΔHKT/Δt exceeds a limit value, this can be interpreted as an increase in the viscosity due to the non-Newtonian effects at the capillary surface. If it is found during the treatment that the time increase exceeds a limit value, the blood flow rate and/or the dilution rate, preferably the predilution rate, is varied by means of a control or regulation unit of the dialysis machine such that the expected ΔHKT/Δt is again adopted or lies in a specific desired value range which can e.g. be present as a window around a desired value. The blood flow rate and/or the ultrafiltration rate is/are preferably reduced on a falling below of the limit value and/or the dilution rate is increased.

[0069] A regulation of the ΔHKT/Δt preferably takes place, with the blood flow rate and/or the dilution rate and/or the ultrafiltration rate being able to serve as control variables.

[0070] A change of the ultrafiltration range for setting the ΔHKT/Δt is admittedly generally conceivable and covered by the invention. It is, however, preferred if it remains constant or follows a predefined profile to be able to achieve the desired weight loss at the end of the treatment.