Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
2002-03-18
2004-06-29
Kim, John (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S232000, C210S240000, C210S321710, C210S645000
Reexamination Certificate
active
06755976
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a holder for a powder cartridge in a dialysis machine and in particular to safety considerations in connection with such a holder and the use of such a powder cartridge. More particularly, the present invention relates to an improved conduit layout in connection with such a holder in order to increase safety.
The term “dialysis machine” is intended to cover not only a machine intended for hemodialysis but also machines for hemofiltration and for hemodiafiltration, as well as for peritoneal dialysis.
BACKGROUND OF THE INVENTION
European Patent Application No. 278,100 describes a dialysis machine of the type to which the present invention may be applied. This application thus describes a dialysis machine which includes a preparation unit for dialysis solutions where the preparation occurs on-line starting from concentrates in liquid and powder form positioned in separate cartridges or vessels.
A dialysis machine comprises basically two parts; namely, a first blood part for transport of blood from a patient through an extracorporeal circuit comprising a dialyzer, and a second liquid part for preparing a dialysis solution and transporting this solution to the dialyzer, and then to a drain.
The dialyzer generally comprises a semi-permeable membrane which divides the dialyzer into a blood-containing part and a dialysate-containing part. The transport of molecules and substances occurs through the membrane for conditioning the blood, in order to replace the function of the kidney.
The present invention relates to the liquid part of the dialysis machine which prepares the dialysis solution. In this part of the dialysis machine, purified water is supplied from an external source such as an RO-unit, and is mixed with concentrate in suitable proportions so that a dialysis solution is prepared. The dialysis solution comprises sodium-, bicarbonate, potassium, calcium, magnesium, chloride and acetate ions in suitable concentrations, as well as possibly glucose and other ions, all dissolved in water. The concentrations of the ions in the dialysis solution are generally mirror-images of the concentrations in blood, where the mirror line is the normal concentration in blood of the ions. Thus, if an ion concentration is increased in the blood over the normal concentration, the ion concentration in the dialysis solution is decreased in relation to the normal concentration. The pH of the solution is adjusted to about 7.1-7.4.
With the most common form of treatment occurring today, bicarbonate dialysis, the dialysis solution is prepared by mixing two liquid concentrates into the main flow of water; i.e., a B-concentrate comprising substantially bicarbonate and an A-concentrate comprising the remaining components. The B-concentrate can also contain sodium chloride. These concentrates are metered in ratios of between about 1:25 and 1:40 depending on the concentration and the desired content of the dialysate, respectively. The metering occurs either volumetrically or by measuring the conductivity and controlling metering pumps so that the correct conductivity is obtained, i.e. feedback control of the metering pumps.
The reason for the division into A- and B-concentrates is that calcium precipitates to form calcium carbonate in the presence of bicarbonate, meaning that these two substances cannot be mixed until immediately before use, and then only in low concentrations. Magnesium also causes similar problems.
European Patent Application No. 278,100 describes the use of one or more powder cartridges as a replacement for the aforementioned concentrate. The powder cartridges are coupled into the dialysis machine and water is allowed to pass through the cartridges in order to form substantially saturated solutions of the powder contents at the outlets. These saturated solutions are metered into the main flow of water instead of the above-mentioned concentrates. For a little less than 10 years, there has been a bicarbonate cartridge on the market which is sold under the trademark BiCart® by GAMBRO AB, as a replacement for the B-concentrate. The B-concentrate was the concentrate which was the most difficult to handle, since the bicarbonate solution was close to its saturation limit, and when storing in cold spaces easily formed precipitates. Additionally, containers were required which were sealed against carbon dioxide, since otherwise decomposition into sodium carbonate occurred, with subsequent pH increase.
Now there is also another type of cartridge on the market which contains sodium chloride. This cartridge replaces the larger amount of ions in the A-concentrate. The remaining ions and substances are contained in a little bag of only about half a liter, called an ion bag.
A dialysis machine which is adapted to use these three components must also have the possibility of using the still generally occurring liquid-formed concentrates. For this purpose there are two hollow rods which are removable and can be fitted into an A-concentrate canister or a B-concentrate canister, respectively. The machine then includes sensors which detect if the rods are positioned in the machine or not. Also there are separate holders for the above-mentioned cartridges. If the holders are folded out and contain a cartridge, this condition is detected by sensors.
One problem which arises with dialysis machines of this type, which are intended to be used for a plurality of different types of concentrates, is that it is possible to mix up the rods and to put the rod for the B-concentrate into the A-concentrate canister and vice versa. This error condition is detected by the electronics in the dialysis machine in that the conductivity value which is expected after the mixing-in does not occur. Thus, the conductivity for the A-concentrate is significantly higher than the conductivity for the B-concentrate.
Another potential for error is the case where the dialysis machine is provided with both cartridges of the powder type and the corresponding rod is put into a container with concentrate. In order to resolve this error condition, the liquid is taken to the bicarbonate cartridge through the rod, to the upper end of the cartridge. If the rod is put into a container with bicarbonate this has no great practical significance, and the only thing that happens is that an additional amount of bicarbonate, is dissolved in the cartridge so that the outgoing solution is substantially saturated. Normally the machine detects this in that the rotational speed for the B-metering pump is lower than when using normal B-concentrate. If, however, A-concentrate comes into a bicarbonate cartridge, gas formation (carbon dioxide) occurs which rapidly results in an alarm condition.
The same or similar conditions exist with the use of a sodium bicarbonate cartridge. If the corresponding A-rod is put into a B-canister, gas formation occurs (carbon dioxide) which rapidly results in an alarm condition.
However, the situation is different if the A-rod corresponding to the A-cartridge is put into a concentrate container containing A-concentrate. The A-concentrate contains substantially sodium chloride and in this respect the situation is the same as with bicarbonate. The A-concentrate however also contains magnesium, potassium, calcium, acetic acid and possibly glucose. Magnesium, potassium and calcium are present in only relatively small amounts, such that they do not have a noticeable effect on the conductivity measurements. If the machine is now adjusted for dialysis with a bicarbonate cartridge, a sodium chloride cartridge and a small bag containing other ions, the machine meters the necessary amount of ions from the small bag, i.e. magnesium, potassium and calcium. This means that the dialysis solution in principle contains double the amount of magnesium, potassium and calcium than was intended. Apart from the fact that this gives rise to incorrect treatment, it can be life-threatening for certain patients. A construction which makes this error condition impossible would be desirable.
One object o
Ericson Björn
Linderup Erik
Rosenqvist Anders
Gambro Lundia AB
Kim John
Lerner David Littenberg Krumholz & Mentlik LLP
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