Surgery – Means for introducing or removing material from body for... – Material introduced into and removed from body through...
Reexamination Certificate
2002-02-14
2003-07-15
Jacyna, J. Casimer (Department: 3751)
Surgery
Means for introducing or removing material from body for...
Material introduced into and removed from body through...
C604S005010, C604S005040
Reexamination Certificate
active
06592542
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the treatment of end stage renal disease. More specifically, the present invention relates to methods and apparatus for monitoring the performance of peritoneal dialysis.
Using dialysis to support a patient whose renal function has decreased to the point where the kidneys no longer sufficiently function is known. Two principal dialysis methods are utilized: hemodialysis; and peritoneal dialysis.
In hemodialysis, the patient's blood is passed through an artificial kidney dialysis machine. A membrane in the machine acts as an artificial kidney for cleansing the blood. Because it is an extracorporeal treatment that requires special machinery, certain inherent disadvantages exist with hemodialysis.
To overcome the disadvantages associated with hemodialysis, peritoneal dialysis was developed. Peritoneal dialysis utilizes the patient's own peritoneum as a semi-permeable membrane. The peritoneum is a membranous lining of the abdominal body cavity. Due to good perfusion, the peritoneum is capable of acting as a natural semi-permeable membrane.
Peritoneal dialysis periodically infuses sterile aqueous solution into the peritoneal cavity. This solution is called peritoneal dialysis solution, or dialysate. Diffusion and osmosis exchanges take place between the solution and the blood stream across the natural body membranes. These exchanges remove the waste products that the kidneys normally excrete. The waste products typically consist of solutes like urea and creatinine. The kidneys also maintain the levels of other substances such as sodium and water which need to be regulated by dialysis. The diffusion of water and solutes across the peritoneal membrane during dialysis is called ultrafiltration.
In continuous ambulatory peritoneal dialysis, a dialysis solution is introduced into the peritoneal cavity utilizing a catheter. An exchange of solutes between the dialysate and the blood is achieved by diffusion. Further removal is achieved by providing a suitable osmotic gradient from the blood to the dialysate to permit water outflow from the blood. This allows a proper acid-base, electrolyte and fluid balance to be achieved in the body. The dialysis solution is simply drained from the body cavity through the catheter.
Peritoneal dialysis raises a number of concerns including: the danger of peritonitis; a lower efficiency and therefore increased duration of dialysis hours compared to hemodialysis; and costs incurred when automated equipment is utilized.
A number of variations on peritoneal dialysis have been explored. One such variation is automated peritoneal dialysis (“APD”). APD uses a machine, called a cycler, to automatically infuse, dwell, and drain peritoneal dialysis solution to and from the patient's peritoneal cavity. APD is particularly attractive to a peritoneal dialysis patient, because it can be performed at night while the patient is asleep. This frees the patient from the day-to-day demands of continuous ambulatory peritoneal dialysis during his/her waking and working hours.
The APD sequence typically lasts for several hours. It often begins with an initial drain cycle to empty the peritoneal cavity of spent dialysate. The APD sequence then proceeds through a succession of fill, dwell, and drain phases that follow one after the other. Each fill/dwell/drain sequence is called a cycle. APD can be and is practiced in a number of different ways.
Current APD systems do not monitor the patient intraperitoneal pressure during a therapy session. Current systems simply limit the external pressure (or suction) that a pump can apply to the line or lumen that is attached to the patient catheter. If the patient is located below the system, sometimes referred to as a cycler, a gravity head will add to the positive fill pressure that the cycler can apply to the patient catheter. Conversely, if the patient is located above the cycler, the gravity head will decrease from the positive fill pressure that the cycler can apply to the patient catheter.
The monitoring of intraperitoneal pressure would be useful because cyclers will sometimes not fully drain a patient between cycles. Specifically, currently-available cyclers are unable to determine whether a patient absorbed some fluid or whether some fluid is simply not able to be drained out because of the position of the patient or the catheter.
As a result, some currently-available systems utilize a minimum drain threshold to determine the amount of fluid that should be delivered to the patient during the next fill. For example, if 85% of the fill volume has been drained when the cycler determines that the patient is “empty”, the next fill volume will be 100%. If only 80% were drained, the next fill volume would be limited to 95%.
A negative ultra filtrate (uF) alarm will sound when the patient has retained more than a predetermined percentage of the fill volume. The predetermined percentage can typically be either 50% or 100% of the fill volume. However, the patient can override this alarm if he/she does not feel overfull. The number of times the patients can override the uF alarm during a single therapy may be limited by the software of the cycler. However, the uF alarm typically does not consider the actual ultra filtrate that may also accumulate in the peritoneal cavity along with the dialysate.
Currently-available cyclers fill the patient to a specific, preprogrammed volume during each cycle. The doctor prescribes this fill volume based upon the patient's size, weight and other factors. However, because currently-available cyclers cannot monitor intraperitoneal pressure, the doctor cannot take this factor into account when formulating the prescription. It is also known that intraperitoneal pressure (IPP) has an effect on ultrafiltration (UF).
FIGS. 1-3
provide schematic illustrations of current APD cyclers. None of them attempt to monitor intraperitoneal pressure.
Referring to
FIG. 1
, a cycler
10
a
is illustrated which includes a dialysate container
11
, a patient
12
and a drain container
13
are illustrated schematically. The infusion of dialysate from the container
11
into the patient
12
is caused by the gravitational head indicated at
14
while the draining of used dialysate from the patient
12
to the drain container
13
is caused by the drain head indicated at
15
. The cycler
10
a
includes no sensors for monitoring the pressure inside the peritoneum of the patient
12
. A single lumen
16
connects both the dialysate container
11
and drain container
13
to the patient
12
. Valves
17
,
18
operated by the cycler
10
a
control the flow of either dialysate from the container
11
to the patient
12
or waste material from the patient
12
to the drain container
13
.
Turning to
FIG. 2
, in the cycler
10
b,
the drain container
13
and dialysate container
11
are contained within a pressurized chamber
19
. The chamber
19
can be pressurized or evacuated to either fill or drain the patient. Again, the selective operation of valves
17
,
18
control whether dialysate is being transferred to or from the patient
12
. Again, no sensors are provided for detecting or monitoring intraperitoneal pressure of the patient
12
.
Turning to
FIG. 3
, in the system
10
c,
a dialysate container
11
is connected to a pump
21
which, in turn, connects the dialysate container
11
to a common lumen or catheter
16
which is connected to the patient. A fluid flow control valve is provided at
23
and is controlled by the cycler
10
c.
The drain container
13
is also connected to a pump
24
which, in turn, connects the drain container
13
to the lumen
16
. A control valve is again provided at
25
.
The drain and fill rates of the cyclers
10
a
-
10
c
illustrated in
FIGS. 1-3
are determined by the gravitational head (see
FIG. 1
) or the suction or pressure (see
FIGS. 2 and 3
) applied to the patient line
16
. Typically, the cyclers
10
a
-
10
c
fail to optimize either the fill rate or the drain rate because the pressure is
Balteau Patrick
Belongie Duane
Childers Robert Warren
Eerlingen Vital
Barrett Robert M.
Baxter International Inc.
Choi Jane J.
Jacyna J. Casimer
Reagen Joseph F.
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