Liquid purification or separation – With alarm – indicator – register – recorder – signal or... – Responsive to fluid flow
Patent
1997-08-05
1999-09-21
Drodge, Joseph W.
Liquid purification or separation
With alarm, indicator, register, recorder, signal or...
Responsive to fluid flow
7386302, 210 93, 210101, 2102572, 210929, B01D 1712, B01D 6134
Patent
active
059549513
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a device for collecting a waste liquid sample representative of all the waste liquid discharged at any time from the beginning of a session for blood treatment by extracorporeal circulation. The invention finds a specific application in the treatment of patients suffering from chronic renal deficiency who are subjected, generally three times weekly, to a haemodialysis, haemofiltration or haemodiafiltration session.
DESCRIPTION OF THE RELATED ART
For the record, haemodialysis consists in circulating, on either side of the semi-permeable membrane of a haemodialyser, the blood of a patient and a treatment liquid which is substantially isotonic with the blood, so that, during the diffusive transfer which is established across the membrane for the substances having different concentrations on either side of the membrane, the blood impurities (urea, creatinine, and the like) migrate from the blood towards the treatment liquid. The electrolytic concentration of the treatment liquid is also generally chosen to correct the electrolytic concentration of the blood of the patient.
Haemofiltration consists in extracting from the blood, by ultrafiltration through the semi-permeable membrane of an exchanger, a predetermined volume of plasma water laden with impurities (filtrate). This convective transfer is caused by a pressure difference created on either side of the membrane of the exchanger. The filtrate is compensated for in part by a substitution liquid infused into the patient.
Haemodiafiltration is a combination of the two treatments, the principles of which have just been restated.
In order to evaluate the effectiveness of a treatment session of this type, that is to say in order also to verify the appropriateness of the prescription (electrolytic composition of the treatment liquid, ultrafiltration flow rate, duration of the session, and the like) to the specific requirements of each patient, it is of the greatest advantage to be able to measure the amount of impurities extracted from the blood during the treatment session. In particular, knowledge of the amount of urea removed during a session makes it possible to calculate the purifying efficiency of the exchanger used (true clearance K for urea) and the dialysis dose administered KT/V by solving the equation treatment, C.sub.UR(bef) is the concentration of urea in the blood before treatment, K is the true clearance for urea, T is the duration of the treatment and V is the total volume of water of the patient (Gotch F. A., Sargent S. A., A mechanistic analysis of the National Cooperative Dialysis Study (NCDS). Kidney Int., 1985, 28, 526-34).
Measuring the amount of impurities removed during a treatment session, in particular the amount of urea, poses a practical problem on account of the volume of waste liquid which is produced, approximately one hundred and twenty liters during a haemodialysis session. The storage of such a volume of liquid, for the purpose of analyzing its contents on completion of the treatment session, is in fact ruled out, in particular for health reasons.
Document EP 0,621,046 describes a device which makes it possible to solve this problem. According to this document, a device for collecting a waste liquid sample representative of all the waste liquid discharged during the treatment session comprises: liquid discharge line of an apparatus for treatment of blood by extracorporeal circulation and a second end which can be connected to a collecting container; connection of the withdrawal line to the discharge line; and container as a function of the data supplied by the flowmeter.
It is known that pumps are metering means whose accuracy does not exceed, in particular at low flow rates, 5 to 10% according to the type of pump used. This absence of accuracy naturally has repercussions on the representativeness of the sample collected. Moreover, the method of operation of certain types of apparatuses for extracorporeal treatment of the blood, as well as certain types of treatment, have a furt
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Drodge Joseph W.
Hospal AG
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