Surgery – Means for introducing or removing material from body for... – Material introduced into and removed from body through...
Reexamination Certificate
2000-09-29
2003-05-06
Maust, Timothy L. (Department: 3751)
Surgery
Means for introducing or removing material from body for...
Material introduced into and removed from body through...
C604S027000, C604S029000
Reexamination Certificate
active
06558343
ABSTRACT:
The present invention relates to the treatment of kidney insufficiency and more particularly to a peritoneal dialysis device.
Peritoneal dialysis uses the peritoneum of the patient as a semi-permeable membrane in order to filter the blood.
During peritoneal dialysis, a sterile aqueous solution (dialysate) is administered into the peritoneal cavity. The cavity is separated from the blood flow by the peritoneum, in particular, so that diffusive and osmotic exchanges can take place between the dialysate and the blood. Those exchanges result in the elimination of harmful substances such as urea, potassium, and creatinine, which are normally excreted by the kidneys. The diffusion of water through the peritoneum during dialysis is called “ultrafiltration”, and the volume of water lost by the patient is called “ultrafiltrate”.
Originally, peritoneal dialysis was characterized by the fact that a given volume of dialysate was initially introduced into the peritoneal cavity, the diffusive and osmotic exchanges were then allowed to take place during a determined period of time, and finally the entire volume of dialysate was removed in order to be replaced by a new volume of dialysate.
Subsequently, peritoneal dialysis became automated resulting in the automated peritoneal dialysis (APD) method in which a machine administers and removes the dialysate. That type of operation may be performed several times and is known as the continuous cycling peritoneal dialysis (CCPD) method.
Automation enables dialysis to be performed during the night, for example, while the patient is asleep.
Patent application EP 402 505 A (A. Peabody) corresponds to a continuous cycling peritoneal dialysis device. The system is equipped with pressure detectors in order to measure volume of ultrafiltrate. By injecting a glucose solution, the osmolarity is varied directly, thereby enabling exchanges to take place and thus enabling harmful substances to be eliminated. That device which is based on varying the osmotic gradient has turned out to be limited in comparison to tidal dialysis.
In addition, patent application DE 33 33 362 A (Fresenius A. G.) also describes a device based on varying the osmotic gradient. Liquid is removed intermittently, but only to measure the osmotic concentration of the active substance.
Tidal peritoneal dialysis (TPD) is characterized by a series of cycles comprising administering dialysate, pausing, and removing dialysate, but in contrast to the methods described above, the volume of dialysate is not completely renewed at each cycle. Only a fraction of the total volume is renewed on each cycle with the exception of the last stage of the cycle in which the entire volume is removed.
Application WO 95/27520 describes, in particular, a device for peritoneal dialysis. The volume changed remains constant while exchange is taking place and can be about 300 ml, i.e. less than 15% of the volume initially administered.
With such volumes, it is possible to achieve high frequency cycles.
The ability to achieve a high frequency has the advantage of enabling the dialysis to be partially renewed often so as to maintain a better quality dialysate, and thus improved purification of the blood.
Patent application EP 498 382 A (A. Peabody) describes a device that can be used for tidal dialysis. The dialysate exchange parameters do not vary. The frequency and the amplitude of the volumes exchanged are constant, only the residual volume in the cavity increases over time. The observed increase in volume can be described as “accidental” since it is not programmed, and results merely from the increase in ultrafiltrate. Thus, that document does not envisage a system for varying the residual volume.
Although prior-art peritoneal dialysis devices are satisfactory to some extent, some drawbacks still exist, however.
Constantly changing the same volume during treatment results in a high consumption of dialysis liquid and in an increase in treatment duration.
In addition, once the initial volume has been administered, although small volumes are changed periodically, the quality of the dialysate in the peritoneal cavity diminishes over time, thereby degrading purification over time.
The present invention seeks to remedy the above-mentioned drawbacks in particular.
It is characterized by the fact that it is essentially constituted by a device that is provided with a system enabling the dialysate exchange parameters to be varied over time so as to maintain an optimum quality of dialysate, while optimizing the exchange volumes so as to minimize the total consumption of dialysis liquid.
In order to achieve this object, the frequency of the exchange cycles can be varied. It can be low at the start of treatment and increase during treatment as the quality of the dialysate in the peritoneal cavity diminishes.
In addition, the volume changed can vary during treatment. It can be relatively small at the start of treatment and increase during treatment as the quality of the dialysate in the peritoneal cavity diminishes.
The present invention also seeks to vary over time the total volume of dialysate in the peritoneal cavity. For example, the volume can increase during treatment. This scenario can be achieved by administering exchange volumes that are greater than the exchange volumes removed.
The pause period, i.e. the time between the administration of an exchange volume and the removal of an exchange volume, can itself be variable. It can be long at the start of treatment and decrease during treatment so as to compensate, at least in part, for the degradation in blood purification due to the lower quality of the dialysate.
The flowrate during an exchange can be variable. It can be low at the start of treatment and increase over time for the same reasons as mentioned above.
Exchange optimization seeks to obtain improved filtration and more ultrafiltrate while reducing the total volume of dialysate required and the length of the treatment.
The variation system of the device of the invention is programmed by using exchange parameters which are established on the basis of optimization that takes account of the parameters specific to each patient (filtration curves). By way of example, the total volume of diaiysate used, or the length of treatment, can be considered during such optimization.
In particular, it is possible to create mathematical models enabling such optimization to be performed by taking account, amongst other things, of the filtration parameters of the patients under consideration.
It is also possible to warm the liquid for administration to the patient during dialysate exchanges by recovering heat from the dialysate liquid removed from the patient by passing it through a heat exchange system (
14
). To do this, the liquid removed can, for example, be passed into a tube which, itself, contains another tube for delivering new dialysate liquid to be warmed.
The heat exchange surface area between the two liquids can also be increased by using a coiled tube which passes into a bag containing the liquid that has been removed from the patient.
A system, e.g. of non-return valves, enables the liquid coming from the patient and the liquid going to the patient to be kept separate through the heat excnange system.
REFERENCES:
patent: 4618343 (1986-10-01), Polaschegg
patent: 5004459 (1991-04-01), Peabody et al.
patent: 5421823 (1995-06-01), Kamen et al.
patent: 33 33 362 (1985-04-01), None
patent: 402505 (1990-12-01), None
patent: 0 498 382 (1992-08-01), None
Debiotech S.A.
Maust Timothy L.
Wolf Greenfield & Sacks P.C.
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