Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
1999-12-21
2001-12-11
Larkin, Daniel S. (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
C073S04050R, C073S037000, C604S029000
Reexamination Certificate
active
06327895
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and an arrangement in a machine for carrying out peritoneal dialysis. More specifically, the invention relates to a method and arrangement for integrity-testing of a tube-set for use in a cycler for peritoneal dialysis
PRIOR ART
Peritoneal dialysis, hereinafter abbreviated to PD, can be carried out more or less manually in a so-called CAPD treatment, where CAPD stands for “continues ambulatory peritoneal dialysis” or with help of a machine in a so-called APD treatment, where APD stands for “automated peritoneal dialysis”.
Liquid for PD is delivered in a sterile form in supply bags which are connected to the patient via a tubeset and a catheter which terminates in the abdominal cavity of the patient. When used in connection with APD, the tube-set comprises a heat bag to which the PD liquid is initially conveyed in order to be heated to body temperature. The liquid has a composition which is suitable for PD. Normally, it includes glucose as an osmotic agent.
A machine which is commonly termed a cycler is used during APD for regulating the supply and removal of liquid to and from the peritoneal cavity in the patient's abdominal cavity via the catheter.
Such a cycler is described in WO 95/20985 and comprises a casing which encases said heat bag as well as a discharge bag. An underpressure and an overpressure respectively can be created in the casing via an air pump to thereby drive the liquid into and out of the bags. Inlets and outlets to the bags pass through respective bushings in the wall of the casing.
A problem which arises in connection with a cycler of the type which is described in WO 95/20985 is the following. If there is a hole in that portion of the tube-set which is located within the casing, i.e. a leak in the bag, the connection between tube and bag or the tube from the bag to or in the bushing, there is a risk that PD liquid can leak out of the bag and collect at the base of the casing.
Such a hole may arise due to faulty material, because the welding between the bag and the tube is unsatisfactory or due to the effect of a sharp object in connection with the use or other careless handling of the bag.
U.S. Pat. No. 5,350,357 discloses a cycler comprising leak testing of the disposable set. Such leak testing is performed as a one step procedure at low or high pressure. This leak testing procedure requires access to the interior of the disposable set.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to provide a method and an arrangement which permits checking if there is a risk of leakage.
In accordance with the invention, the portion of the tube-set which is located within the casing is subjected to an integrity-test before the machine is allowed to commence the dialysis treatment.
The machine is started and performs its normal function test in which all of the essential functions and safety systems of the machine are tested. During this function test, the machine is attired with the sterile tube-set. Supply bags are connected to the inlet tubes. The patient connection is placed in a special priming position. When the function test has been performed, the machine adopts a stand-by condition. When the patient has attached the tube-set, the patient presses a pre-rinse button. Before the actual pre-rinse or priming of the tube-set, an integrity-test according to the invention is performed.
By means of an air pump, an overpressure of a predetermined amount is created in the casing outside the tube-set, whereby the outlets from the tube-set are open. When the predetermined air pressure has been reached, the pump is stopped and the clamp arrangements are closed. The air can thus exit the casing via a possible leakage which is always present in such a construction, for example between the cover and base of the casing or via the bushings. A “normal” leakage implies that the pressure slowly reduces. The pressure sequence is recorded using a pressure meter for a predetermined interval of time.
Thereafter, the pressure is once more increased in the casing to said predetermined pressure and the outlets via the tube-set are opened by means of clamps. The pressure sequence is once more recorded using the pressure meter for a predetermined interval of time.
If the pressure sequences are substantially identical for the first two tests, it is an indication that the tube-set has passed the integrity-test. The tube-set is thereafter filled with liquid in a so-called priming stage.
If, on the other hand, the second pressure sequence leads to a more rapid reduction of the pressure than the first pressure sequence, it is an indication that there is a fault present. Thus, the machine can emit an alarm signal. Furthermore, the machine can be placed in a condition which renders impossible continued use until a new tube-set is mounted and a new integrity-test has been executed.
Alternatively, the integrity-test can be performed with underpressure in the casing or underpressure and overpressure in combination. Other alternatives will be apparent from the following description.
According to the invention, the difference in final pressure is not allowed to be greater than the predetermined pressure differential value for the machine to be able to recognise that the integrity-test has been executed in a satisfactory manner. Other methods of calculation can also be used.
The integrity-test can be combined with devices for sensing whether liquid has leaked onto the base of the casing.
Thus, it is apparent that the invention makes possible a leak test without intervening into the interior of the tube-set, which is sterilised before use and should be kept sterile. The invention discriminates between a “normal” leakage and a leakage through a hole, which cannot be tolerated.
The invention will be described in greater detail below with reference to an embodiment of the invention shown in the drawings.
REFERENCES:
patent: 5350357 (1994-09-01), Kamen et al.
patent: 5411682 (1995-05-01), Nagashima
patent: 5624551 (1997-04-01), Baumann et al.
patent: 5674404 (1997-10-01), Kenley et al.
patent: 5711883 (1998-01-01), Folden et al.
patent: 6044691 (2000-04-01), Kenley et al.
patent: 6187207 (2001-02-01), Brauer
patent: WO 95/20985 (1995-08-01), None
patent: 96/40322 (1996-12-01), None
patent: WO 97/11770 (1997-04-01), None
Jeppsson Jan-Bertil
Thell Bengt-Olov
Gambro Lundia AB
Garber Charles D.
Larkin Daniel S.
Lerner David Littenberg Krumholz & Mentlik LLP
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