Peritoneal dialysis sensor apparatus systems, devices and methods
A sensor apparatus and sensor apparatus system for use in conjunction with a cassette-based peritoneal dialysis system is described, including a disposable cassette. In some embodiments, the cassette includes a thermal well for permitting the sensing of various properties of a dialysate. The thermal well includes a hollow housing of a thermally conductive material. In other embodiments, the cassette includes sensor leads for sensing of various properties of a dialysate. The thermal well has an inner surface shaped so as to form a mating relationship with a sensing probe. The mating thermally couples the inner surface with a sensing probe. In some embodiments, the thermal well is located on a disposable portion and the sensing probe on a reusable portion.
1. A method for determining temperature and conductivity of a dialysate in a peritoneal dialysis pump cassette, said pump cassette comprising a first region formed of a flexible membrane and a second region formed of a rigid material and not comprising a flexible membrane, said second region having at least two thermal wells formed in the rigid material and extending into a liquid flow path in the cassette, at least one of said thermal wells having at least a portion comprising an electrically conductive material configured for contacting a liquid contained in said liquid flow path, said method comprising the steps of:
placing the cassette in a dialysis machine having at least two sensing probes, each sensing probe adapted to mate with one of the thermal wells;
thermally coupling each thermal well with a sensing probe such that temperature and conductivity can be determined;
transferring thermal and conductivity signals through at least 3 leads from at least one of said sensing probes; and
determining temperature and conductivity of a liquid contained in the liquid flow path using said signals.
2. The method of claim 1 , wherein the pump cassette comprises a first side comprising the first region formed of the flexible membrane, a second side opposite the first side, and a third side comprising the second region having the at least two thermal wells.
3. A method for determining the temperature and conductivity of dialysate in a peritoneal dialysis pump cassette, said pump cassette comprising a first region formed of a flexible membrane and a second region formed of a rigid material and not comprising a flexible membrane, said second region having at least two thermal wells formed in the rigid material and extending into a liquid flow path in the cassette, at least one of said thermal wells having at least a portion comprising an electrically conductive material configured for contacting a liquid contained in said liquid flow path, said method comprising the steps of:
placing the cassette in a dialysis machine having at least two sensing probes, each sensing probe adapted to mate with one of the thermal wells;
thermally coupling each thermal well with a sensing probe such that temperature and conductivity can be determined;
transferring thermal and conductivity signals through at least 3 leads from at least one of said sensing probes;
determining temperature and conductivity of a liquid contained in the liquid flow path using said signals; and
comparing the conductivity determined to a preset conductivity level.
4. A method according to claim 3 , wherein said method further comprises the step of sending a signal to the dialysis machine if the determined conductivity is not within a specified range of the preset conductivity level.
5. A method according to claim 4 , wherein said method further comprises the step of suspending peritoneal dialysis treatment if the determined conductivity is not within the specified range of the preset conductivity level.
6. The method of claim 3 , wherein the pump cassette comprises a first side comprising the first region formed of the flexible membrane, a second side opposite the first side, and a third side comprising the second region having the at least two thermal wells.
7. A disposable pump cassette for performing peritoneal dialysis comprising:
a) a first side comprising a flexible membrane for pumping or directing liquid in the cassette;
b) an opposing second side adapted and configured to receive a force urging at least a portion of the cassette against the flexible membrane when the cassette is mounted in a dialysis machine; and
c) a third side not comprising a flexible membrane, wherein at least a portion of said third side:
is not parallel to said first side;
is not parallel to said opposing second side;
spans at least a portion of the distance separating said first side from said opposing second side; and
comprises a thermal well extending into a liquid path in the cassette, wherein
the thermal well has a liquid side for making contact with liquid in the cassette and an opposing probe side for reversible mating with a sensing probe, said thermal well being thermally conductive between the liquid side and the probe side.
8. A cassette according to claim 7 , wherein the cassette comprises at least one pump chamber.
9. A cassette according to claim 7 , wherein the cassette comprises at least one valving station.
10. A cassette according to claim 7 , wherein the cassette comprises at least one pump chamber and one valving station.
11. A cassette according to claim 7 , wherein the thermal well is a first thermal well, and the cassette comprises a second thermal well spaced apart from the first thermal well, wherein the liquid side of the first thermal well is in fluid communication with the liquid side of the second thermal well through a liquid flow path in the cassette.
12. A cassette according to claim 11 , wherein the first thermal well can be reversibly coupled with a first sensing probe, the second thermal well can be reversibly coupled with a second sensing probe, and at least a portion of each thermal well is electrically conductive, said couplings permitting conductivity sensing of a liquid in the liquid flow path in the cassette.
13. A cassette according to claim 12 , wherein at least one of the first sensing probe and the second sensing probe has three leads for transmitting thermal and electrical conductivity signals.
14. A cassette according to claim 7 , wherein the well is secured to the cassette using at least one of press fit connection, flexible tabs, adhesive, ultrasonic weld, and a retaining plate with fastener.
15. A disposable pump cassette for performing peritoneal dialysis comprising:
a) a first region formed of a flexible membrane; and
b) a second region, not co-planar with said first region, that is formed of a rigid material, does not comprise a flexible membrane and has at least two thermal wells formed in the rigid material and extending into a liquid flow path in the cassette; wherein
each thermal well has a liquid side for making contact with liquid in the cassette and an opposing probe side for reversible mating with a sensing probe, each thermal well being thermally conductive between the liquid side and the probe side.
16. A cassette according to claim 15 , wherein the cassette comprises at least one pump chamber.
17. A cassette according to claim 15 , wherein the cassette comprises at least one valving station.
18. A cassette according to claim 15 , wherein the cassette comprises at least one pump chamber and one valving station.
19. A cassette according to claim 15 , wherein the thermal wells are spaced apart from each other and wherein the liquid side of each thermal well is in fluid communication with the liquid side of each other thermal well through the liquid flow path in the cassette.
20. A cassette according to claim 19 , wherein a first thermal well can be reversibly coupled with a first sensing probe, a second thermal well can be reversibly coupled with a second sensing probe, and at least a portion of each thermal well is electrically conductive, said couplings permitting conductivity sensing of a liquid in the liquid flow path.
21. A cassette according to claim 20 , wherein at least one of the first sensing probe and the second sensing probe has three leads for transmitting thermal and electrical conductivity signals.
22. A cassette according to claim 15 , wherein the at least two wells are secured to the cassette using at least one of press fit connection, flexible tabs, adhesive, ultrasonic weld, and a retaining plate with fastener.