Patent Application
20190137372
The present invention relates to a method for testing the rigidity of a particular volumetric balancing disposable for a blood treatment device.
The present invention further relates to a blood treatment device.
From the state of the art, it is known that blood treatment devices not only carry out blood purification or other treatments, such as separation into different components, for instance, but also, in a further essential task, balance fluid volumes. Haemodialysis, peritoneal dialysis, plasma separation devices, liver support systems and devices used in the context of sepsis may be mentioned as examples of such devices.
Haemodialysis apparatuses thus perform blood treatment by way of the dialyzer, with quantification made of the dialysis fluid volumes supplied to and discharged from the dialysis by means of a balancing system.
For this, volume balance systems are used that have a chamber with a fixed volume in which a flexible membrane is located. The membrane separates the chamber into two areas. If a region is filled with a liquid, the same volume is displaced out of the other chamber. The rigid vessel forming the chamber ensures the desired accuracy, since its volume does not change, due to the rigid chamber walls.
In order to build compact, highly integrated systems, it is desirable to implement similar systems in a disposable, i.e. with a disposable unit.
The volume of the disposable acts as a micro batch, i.e. it can be used for volumetric balancing without being provided a balancing chamber specifically formed for this purpose. For example, the flow paths including the pre-filter of a cartridge, i.e. of the disposable, can together form the batch volume used for balancing.
This type of disposable usually consists of plastic material.
To be able provide the required balancing accuracy, the convolutions of the disposable must exhibit sufficient rigidity, i.e. inflexibility. This is taken to mean that the convolutions of the disposable are designed so that the volume delimited by it is constant, or lies within the range of certain limits.
Systems and disposables whose rigidity is constant, or within a certain tolerable range, are thus advantageous.
The objective of the present invention is to provide a method by which the rigidity of wall portions of a disposable, or parts thereof, can be measured.
This objective is resolved by a method with the characteristics of claim 1.
According to this, it is envisaged that the method comprises the following steps: filling the disposable or part thereof with a fluid; enclosing the fluid filled, so that in the disposable unit, or in part of it, a certain fluid volume is present; supplying and/or removing of a certain fluid volume; and measuring the pressure change caused by the supply and/or discharge of said fluid volume.
According to the invention, a certain volume of the disposable, hereinafter also referred to as cartridge, is occluded, i.e. stopped up, which can be done by clamps or valves, for example. One or more short pump pulsations are then carried out, by means of a pump, for example. The more rigid the cartridge, the greater the pressure increase or decrease in the volume enclosed by the cartridge, which is caused by the pump pulsations.
If the cartridge is very rigid, i.e. a constant volume, larger increases or decreases in the measured pressure result than with a cartridge whose walls are flexible, thereby allowing a greater volume change.
The rigidity measurement is influenced by many factors that can per se produce a volume change, such as air unduly present in the disposable after filling with fluid. If the test results in a low rigidity, the filling/flushing process can be repeated as an initial remedial measure, so that any air pocket interference can be excluded. If, in one or more repetitions of the test, or of the method according to the invention, the rigidity threshold value is not achieved, then it can be concluded that the condition of the cartridge wall or disposable is defective.
The rigidity threshold can be selected so that small volume changes, due to air pockets, or defective cartridge walls, or disposable conditions not exceeding the tolerated margin of error are still accepted. This may be the case, for example, when the error with respect to the total fluid volume conducted over the treatment period through the cassette or disposable is <10 or <2 parts per thousand. In this case, the cassette or disposable can nevertheless be described as working.
The method according to the invention is carried out prior to patient treatment with the blood treatment device, preferably directly after filling the disposable. The patient's fluid is connected with the blood treatment device during the implementation of the method. The patient is preferably not connected to the blood treatment device during the procedure.
A case also covered by the invention is that where no fluid volume can be supplied or discharged, i.e. the cartridge is completely rigid, and thereby does not allow for any volume change.
In order to pass the test according to the inventive method, the pressure measured thereby must change in amplitude, i.e. the measured pressure rise or drop must be greater than a reference value. This reference value has been determined in advance as a volumetric balancing with a sufficient value.
The term “measurement of a change in pressure” is also understood as the case where the pressure change per se is not measured, but rather, pressure values are measured and the difference, i.e. the pressure change, is determined. The same applies to terms concerning measurement of a pressure increase or decrease.
It is possible for the supply and removal of fluid volume to occur by means of one or more pumps, which are in fluid communication with the disposable, so that the fluid volume can be supplied or removed from inside the disposable.
For the pump or pumps, these are preferably pumps that already form part of a blood treatment device, which thereby provides the advantage of not having to provide pumps specially intended for carrying out the process.
It is possible for this pump to be the ultrafiltration pump or dialysate pump of a dialysis device.
However, the invention is not limited to dialysis devices. Any other blood treatment devices are encompassed by the invention, such as plasma separation devices, liver support systems, systems for the treatment of sepsis, and so on.
In one possible embodiment of the invention, the method is carried out so that the supply and/or removal of further fluid volume, as well as measurement of the pressure increase or decrease, is carried out several times.
It is possible thereby that the same fluid volume, or also different fluid volumes are always supplied and discharged. In this way, interference effects can be avoided.
Occlusion, that is, impingement of the fluid, can take place by closing valves or clamps, for example. The valves or clamps are preferably those of the blood treatment device.
A further embodiment of the invention provides for the disposable comprising at least two balancing chambers, with at least one channel connecting the balancing chambers provided. Thereby, though the method according to the invention, the chambers, in operation, separated from each other, can simultaneously be tested for rigidity.
In a further embodiment of the invention, the pressure is measured at the pump or in a region of the disposable.
Basically, pressure measurement can take place at any position at which the supply or removal of the fluid volume leads to a pressure change correlating with the rigidity of the disposable.
The present invention further relates to a blood treatment device having at least one receptacle for a disposable intended for volumetric balancing, whereby the blood treatment device includes one or more actuators, which are designed to act on the disposable, whereby the blood treatment device has one or more pumps, which are designed to promote a certain fluid volume in and/or out, and whereby the blood treatment device comprises one or more pressure sensors formed so as to measure the fluid pressure contained in the disposable, whereby the blood treatment device has at least one processor activating the actuator or actuators and one or more pumps, and is programmed to carry out a method according to one of claims 1 to 8.
As stated above, the blood treatment device may be a dialyzer or plasma separation device, for example, or a liver support system or a device for the treatment of sepsis.
The pump may be the ultrafiltration pump, or dialysate pump or any other blood treatment device pump.
The use of a separate pump, that is, of a pump that does not form part of the blood treatment device is also possible and covered by the invention.
The pressure sensor serving to detect pressure changes is preferably located in or on the pump, or in or on the disposable.
It is further possible for the blood treatment device to include one or more valves, by means of which a certain fluid volume in the disposable can be shut off.
In a further embodiment of the invention, the blood treatment device has an evaluation unit, which is designed to compare the measured pressure increase or decrease with a threshold value.
In this, it is also possible for the blood treatment device to includes a display unit, which is adapted to indicate whether the pressure change measured exceeds a threshold value, or not.
Alternatively or additionally, the blood treatment device can include a locking unit, which is configured to prevent the blood treatment device from operating if the pressure change measured does not reach or exceed the threshold.
In this way, blood treatment with a disposable that does not meet the desired rigidity requirements can be restricted.
Further details and advantages of the invention will be explained with reference to the embodiment displayed in the Figures.
These display:
In the figures, identical or functionally identical parts are designated by identical reference characters.
For the dialysis device, the dialyzer is shown by reference number 10, the interior of which is divided by a membrane consisting of a hollow fibre bundle in a dialysate compartment and a blood chamber. The blood chamber comprises the interior spaces of the hollow fibres.
The blood flow through dialyzer 10 is identified by reference B and the dialysate through cassette 1 and through dialyzer 10 is identified by reference D.
The dialyzer can be a haemodialysis, hemofiltration or haemodiafiltration device, for example. However, any other blood treatment devices are included for the invention.
Cartridge 1 includes Channels 2 and 3, and chambers for directing and balancing fresh and spent dialysis fluids.
The chambers of cartridge 1, serving for balancing, are together characterized as reference 20. The balancing system, 20, is configured such that the volume displaced from one chamber corresponds with the dialysis fluid volume supplied to the other chamber. The confirmation of the chambers is performed by dialysis device actuators. Furthermore, the dialysis device features plungers, clamps or other actuators that act as valves, and are able to lock the cartridge channels.
To carry out a rigidity test rigidity test according to the present invention, a volume of Cartridge 1 is shut off by closing the valves, i.e. by disconnecting the cartridge 1 channels, for example.
A specific fluid volume is thus occluded.
For example, valves in feed channels and discharge ports 2 and 3 for the dialysis fluid and between balancing system 20 and dialyzer 10, as well as on the side facing away from the dialyzer of the balancing system will be closed, so that the volume located in between is occluded.
Such a situation results in
The channel not shut off, or connecting line 4, connects input and output channels 2 and 3 together.
The ultrafiltration pump of the dialysis device is identified by reference number 30.
This is associated with the interior of the cartridge 1 via an open channel, such that the dialysate used in operating the dialysis device is removed from cartridge 1.
To carry out the rigidity tests according to the invention, the ultrafiltration pump 30 is used to carry out a known volume displacement in the occluded hydraulic system of cartridge 1. This volume displacement may consist of a supply and/or withdrawal of liquid to or from cartridge 1.
The rigidity of the walls of cartridge 1 are indicated by measurement of the pressure inside cartridge 1.
The more yielding the cartridge, 1, i.e. the lower the rigidity of cartridge 1, the lower the pressure changes, which are caused by a volume displacement. The stiffer the cartridge, 1, i.e. the higher the rigidity of cartridge 1, the greater the pressure changes, which are due to a volume displacement.
The measured pressure change is thus a measure of the rigidity of the part of cartridge 1 in which the volume is occluded.
In the case outlined in
Further deviating from the arrangement, according to
A comparison between
Furthermore, pressure sensors are indicated by reference P, which measure the pressure in the occluded volume of cartridge 1. As can be seen from
Other locations for pressure measurement are also possible, and encompassed by the invention. It is thus possible, for example, to measure pressure in the balancing system 20.
The one or more pressure sensors have the task of measuring the volume shift induced pressure change in the occluded fluid volume.
In the example illustrated in
When the pressure exceeds a defined limit within the test time, such as the value of 80 mbar within 1 s, the rigidity test is passed and the cartridge 1 is found to be good. If the limit is not reached at all or exceeded only after expiry of the test period, the rigidity test is failed and the cartridge 1 is discarded.
The pressure curve shown in
A displacement volume of 1.5 ml is then made into and out of the closed system of cartridge 1.
As seen in
The above values are examples, and not limitative.
The changing volume shift (change from fluid supply and fluid discharge) excludes disruptive effects.
The rigidity test according to the invention is combined with a pressure holding test, according to
After performing the rigidity tests, no further fluid volume is supplied or removed, and the pressure is further measured.
If the pressure drop over time is below a threshold (here, 20 mbar/min), the pressure holding test is passed. The pressure holding test is based on a certain rigidity of the cartridge. If this this more flexible, the test time and permissible threshold should be adjusted
The method according to the invention, i.e. the rigidity test, can be carried out before treatment or by commissioning the dialysis device. It can also be carried out during treatment and be triggered by one or more different circumstances.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2015 015 636.5 | Dec 2015 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/002033 | 12/1/2016 | WO | 00 |
