U.S. patent application number 14/094470 was filed with the patent office on 2014-03-27 for automated peritoneal dialysis cycler and methods of use.
This patent application is currently assigned to VR MEDICAL TECHNOLOGY, LLC. The applicant listed for this patent is VR MEDICAL TECHNOLOGY, LLC. Invention is credited to LI PAN.
Application Number | 20140088493 14/094470 |
Document ID | / |
Family ID | 43856065 |
Filed Date | 2014-03-27 |
United States Patent
Application |
20140088493 |
Kind Code |
A1 |
PAN; LI |
March 27, 2014 |
AUTOMATED PERITONEAL DIALYSIS CYCLER AND METHODS OF USE
Abstract
Automated peritoneal dialysis (APD) cycler systems and methods
are disclosed. The APD cycler can include a heater tray with load
cells configured to measure the weight of fluid contained within a
heater bag and/or a drain bag. The load cells can be toggleable
between enabled and disabled configurations. The APD cycler can
include a pressure-based volume measurement system, which can be
used to confirm measurements made by the load cells. In some
embodiments, the APD cycler can have algorithms for tracking an
estimated patient volume to prevent overfilling the patient.
Inventors: |
PAN; LI; (ARCADIA,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VR MEDICAL TECHNOLOGY, LLC |
Clearwater |
FL |
US |
|
|
Assignee: |
VR MEDICAL TECHNOLOGY, LLC
Clearwater
FL
|
Family ID: |
43856065 |
Appl. No.: |
14/094470 |
Filed: |
December 2, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12973673 |
Dec 20, 2010 |
8597229 |
|
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14094470 |
|
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|
61284745 |
Dec 24, 2009 |
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Current U.S.
Class: |
604/29 ;
73/37.5 |
Current CPC
Class: |
A61M 1/166 20140204;
G01B 13/00 20130101; A61M 2205/3393 20130101; A61M 1/1643 20140204;
A61M 1/28 20130101; A61M 1/282 20140204; A61M 1/281 20140204 |
Class at
Publication: |
604/29 ;
73/37.5 |
International
Class: |
A61M 1/28 20060101
A61M001/28; G01B 13/00 20060101 G01B013/00 |
Claims
1. A dialysis system comprising: a containment chamber containing a
first volume of gas and configured to receive a fill bag and a
drain bag therein; a first pressure sensor configured to measure
the pressure in the containment chamber; a reference chamber
containing a second volume of gas; a second pressure sensor
configured to measure the pressure in the reference chamber; a
valve configured to selectively open and close a pathway between
the containment chamber and the reference chamber; one or more
pumps configured to apply pressure to the containment chamber and
to the reference chamber; and a controller configured to apply a
first pressure to the containment chamber using the one or more
pumps, to apply a second pressure to the reference chamber using
the one or more pumps, to open the pathway between the containment
chamber and the reference chamber with the valve, and to measure an
equalized pressure in at least one of the containment chamber and
the reference chamber after the pressures of the containment
chamber and the reference chamber have substantially equalized.
2. The dialysis system of claim 1, wherein the controller is
configured to calculate the first volume of gas inside the
containment chamber based at least in part on the measured
equalized pressure.
3. The dialysis system of claim 2, wherein the controller is
configured to determine a volume of an amount of fluid in at least
one of the fill bag and the drain bag based at least in part on the
calculated first volume of gas inside the containment chamber.
4. The dialysis system of claim 3, further comprising a weigh scale
configured to measure the weight of an amount of fluid in at least
one of the fill bag and the drain bag.
5. The dialysis system of claim 4, wherein the controller is
configured to compare the measurement of the weigh scale to the
calculated volume of the amount of fluid in at least one of the
fill bag and the drain bag, and to post an alarm if the calculated
volume differs from the measurement of the weigh scale by more than
a threshold amount.
6. The dialysis system of claim 4, wherein the controller is
configured to calculate the volume of the fluid in at least one of
the fill bag and the drain bag based at least in part on the
measured weight, to compare the volume calculated from the measured
weight to the volume calculated from the equalized pressure, and to
post an alarm if the volume calculated from the measured weight
differs from the volume calculated from the equalized pressure by
more than a threshold amount.
7. The dialysis system of claim 1, wherein the first pressure
applied to the containment chamber is a negative pressure, and
wherein the second pressure applied to the reference chamber is a
negative pressure.
8. The dialysis system of claim 7, wherein the second pressure
applied to the reference chamber is a higher negative pressure than
the first pressure applied to the containment chamber.
9. The dialysis system of claim 1, further comprising one or more
heating elements configured to warm fluid in the fill bag.
10. The dialysis system of claim 1, wherein the controller is
configured to determine a volume of an amount of fluid in at least
one of the fill bag and the drain bag based at least in part on the
measured equalized pressure.
11. A method of determining a volume in a dialysis system,
comprising: providing a containment chamber containing a first
volume of gas and configured to receive a fill bag and a drain bag
therein; providing a reference chamber containing a second volume
of gas; applying a first pressure to the containment chamber using
one or more pumps; applying a second pressure to the reference
chamber using the one or more pumps; opening a pathway between the
containment chamber and the reference chamber; allowing the
pressures of the containment chamber and the reference chamber to
substantially equalize; measuring an equalized pressure in at least
one of the containment chamber and the reference chamber; and
calculating, using one or more computing devices, the first volume
of gas inside the containment chamber based at least in part on the
measured equalized pressure.
12. The method of claim 11, further comprising determining a volume
of an amount of fluid in at least one of the fill bag and the drain
bag based at least in part on the calculated first volume of gas
inside the containment chamber.
13. The method of claim 12, further comprising measuring the weight
of an amount of fluid in at least one of the fill bag and the drain
bag using a weigh scale.
14. The method of claim 13, further comprising: comparing the
measured weight to the calculated volume of the amount of fluid in
at least one of the fill bag and the drain bag; and posting an
alarm if the calculated volume differs from the measurement of the
weigh scale by more than a threshold amount.
15. The method of claim 13, further comprising: calculating the
volume of the fluid in at least one of the fill bag and the drain
bag based at least in part on the measured weight; comparing the
volume calculated from the measured weight to the volume calculated
from the equalized pressure; and posting an alarm if the volume
calculated from the measured weight differs from the volume
calculated from the equalized pressure by more than a threshold
amount.
16. The method of claim 11, wherein the first pressure applied to
the containment chamber is a negative pressure, and wherein the
second pressure applied to the reference chamber is a negative
pressure.
17. The method of claim 16, wherein the second pressure applied to
the reference chamber is a higher negative pressure than the first
pressure applied to the containment chamber.
18. The method of claim 11, further comprising warming fluid in the
fill bag.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 12/973,673, filed on Dec. 20, 2010, and titled AUTOMATED
PERITONEAL DIALYSIS CYCLER AND METHODS OF USE, which claims the
benefit under 35 U.S.C. .sctn.119(e) of U.S. Provisional Patent
Application No. 61/284,745, filed on Dec. 24, 2009, and titled
AUTOMATED PERITONEAL DIALYSIS CYCLER EMPLOYING REDUNDANT FLUID
MEASUREMENT SYSTEMS. Each of the above-identified applications is
hereby incorporated by reference herein and made a part of this
specification for all that it discloses.
INCORPORATION BY REFERENCE
[0002] The following references are hereby incorporated by
reference herein in their entirety and made a part of this
specification for all that they disclose: U.S. Patent Publication
No. 2006/0195064; U.S. Patent Publication No. 2007/0112297; U.S.
Pat. No. 4,560,470; U.S. Pat. No. 4,585,436; U.S. Pat. No.
4,826,482; U.S. Pat. No. 4,976,162; U.S. Pat. No. 5,421,823; U.S.
Pat. No. 5,324,422; U.S. Pat. No. 5,338,293; U.S. Pat. No.
5,350,357; U.S. Pat. No. 5,421,823; U.S. Pat. No. 5,474,683; U.S.
Pat. No. 5,722,947; and chapters 12 and 14 of Aseptic
Pharmaceutical Manufacturing II (ISBN: 0-935184-77-5). The devices,
structures, compositions, methods, and procedures disclosed in
these references are provided as background and can be used in
addition to or instead of those disclosed in various sections of
this application.
BACKGROUND OF THE DISCLOSURE
[0003] 1. Field of the Disclosure
[0004] The present disclosure relates generally to systems and
method for conducting dialysis treatment, and more specifically to
systems and methods for conducting automated peritoneal dialysis
treatment.
[0005] 2. Background
[0006] Although systems and methods for conducting dialysis
treatment exist, there remains a need for improved automated
peritoneal dialysis systems and methods.
SUMMARY OF THE INVENTION
[0007] Some example embodiments are summarized below. In some
embodiments, a dialysis system can have a pressure-based volume
measurement system. The dialysis system can include a containment
chamber and a reference chamber, and one or more pumps configured
to control the pressure within the containment chamber and
reference chamber. The dialysis system can have a controller
configured to set the containment chamber to a first pressure and
to set the reference chamber to a second pressure. The controller
can open a connection between the containment chamber and reference
chamber so that the pressures are allowed to substantially
equalize. The equalized pressure can then be measured in one or
both of the containment chamber and the reference chamber.
[0008] One or both of the first and second pressures can be a
negative pressure. In some embodiments, the second pressure in the
containment chamber can be a higher negative pressure than the
first pressure in the containment chamber. In some embodiments, the
ratio between the pressure of the reference chamber and the
pressure of the containment chamber can be greater than about 2 to
1, 4 to 1, or 10 to 1. In some embodiments, positive pressures may
be used in one or both of the containment chamber and reference
chamber. The reference chamber can have a higher pressure therein
than does the containment chamber. In some embodiments, the first
pressure applied to the containment chamber is a negative pressure
at least about -0.1 psig and/or of less than or equal to -1.0 psig
or -0.5 psig. In some embodiments, a negative pressure of at least
about -5.0 psig and/or less than or equal to about -9.0 psig. In
some embodiments, the containment chamber or the reference chamber
can be set to substantially atmospheric pressure.
[0009] The controller can be configured to calculate the volume of
gas inside the containment chamber based at least in part on the
measured equalized pressure. The controller can be configured to
determine a volume of an amount of fluid in at least one of a
heater bag and a drain bag based at least in part on the calculated
volume of gas inside the containment chamber.
[0010] One or more pressure sensors can be configured to measure
the pressure in the containment chamber and the reference chamber.
The system can also include temperature sensors in some
embodiments, and the controller can be configured to determine the
volume of gas inside the containment chamber at least in part on a
measured change in temperature in one or both of the containment
chamber and the reference chamber.
[0011] The system can have a weigh scale configured to measure the
weight of an amount of fluid in at least one of a heater bag and a
drain bag. The pressure-based volume measurement system can be used
to confirm measurements made using the weigh scale (which can
include, for example, one or more load cells). The controller can
be configured to compare the measurement of the weigh scale to the
calculated volume of the amount of fluid in at least one of the
heater bag and the drain bag, and the controller can post an alarm
if the calculated volume differs from the measurement of the weigh
scale by more than a threshold amount. The controller can use the
weight measured by the weigh scale to determine a volume of fluid
and compare that volume with the volume measured by the
pressure-based volume.
[0012] The volume of the containment chamber can be determined by
applying a first pressure to the containment chamber using one or
more pumps, applying a second pressure to the reference chamber
using the one or more pumps, opening a pathway between the
containment chamber and the reference chamber, allowing the
pressures of the containment chamber and the reference chamber to
substantially equalize, measuring an equalized pressure in at least
one of the containment chamber and the reference chamber, and
calculating, using one or more computing devices, the first volume
of gas inside the containment chamber based at least in part on the
measured equalized pressure.
[0013] A volume of an amount of fluid in at least one of the heater
bag and the drain bag can be determined based at least in part on
the calculated first volume of gas inside the containment
chamber.
[0014] The weight of an amount of fluid in at least one of the
heater bag and the drain bag can be measured using a weigh scale,
and that weight can be compared to the calculated volume of the
amount of fluid in at least one of the heater bag and the drain
bag. An alarm can be posted an alarm if the calculated volume
differs from the measurement of the weigh scale by more than a
threshold amount. The weight can be used to calculate a volume of
fluid to be compared to the volume of fluid that was calculated
from the equalized pressure.
[0015] A load cell can be used to measure the weight applied to a
tray of a dialysis system. The load cell can be toggleable between
an enabled configuration and a disabled configuration. When the
system is moved, or not in use, the load cell can be set to the
disabled configuration so that movement, or vibrations, etc. do not
damage the load cell. The load cell can include a main body and a
sensor configured to generate a signal representative of force
applied to the main body. A tray can be coupled to the main body.
An isolation member (such as a screw) can be moveable between an
enabled position and a disabled position. When the isolation member
is in the enabled position, weight applied to the tray is
transferred to the main body to generate a signal using the sensor
that is representative of the weight applied to the tray. When the
isolation member is in the disabled position, the weight applied to
the tray is transferred through the isolation member such that the
weight is not applied to the main body.
[0016] The load cell can have a support bar, and the isolation
member can be configured to engage the support bar when in the
disabled position such that the weight from the tray is transferred
through the isolation member to the support bar.
[0017] The system can have multiple load cells that can be
configured to operate in parallel such that the measurements of the
plurality of load cells are combined to produce a value
representative of the weight applied to the tray.
[0018] In some embodiments, the dialysis system can be configured
to reduce the pressure applied when draining fluid (e.g., from a
patient) when the drain nears completion. A dialysis system can
have a sealed containment chamber, a drain container positioned
inside the containment chamber, and a patient line in fluid
communication with the drain container. The patient line can
configured to attach to a patient catheter. A controller can be
configured to apply a negative pressure to the containment chamber,
using one of more pumps, such that fluid is drawn through the
patient line into the drain container. The flow rate can be
monitored, and the controller can reduce the negative pressure in
the containment chamber in response to a measured reduction in the
flow rate of fluid into the drain container.
[0019] The controller can be configured to gradually reduce the
negative pressure in the containment chamber as the flow rate of
fluid into the drain bag reduces. The controller can be configured
to maintain the negative pressure in the containment chamber at a
substantially constant level until the flow rate drops below a
first threshold rate, and the controller can be configured to
reduce the negative pressure in response to the flow rate dropping
below the first threshold level. The controller can be configured
to stop the drain of fluid into the drain bag in response to the
flow rate dropping below a second threshold level.
[0020] In some embodiments, the system can be configured to track
an estimated patient volume (e.g., the amount of fluid present in
the patient peritoneum), to prevent overfilling. The system can
drain fluid from a patient, identify an indicator that the drain is
complete, and measure the volume of fluid in the drain bag. The
system can calculate a minimum drain volume as a predetermined
percentage of the expected drain volume. The expected drain volume
can be the infusion volume from the previous fill stage plus an
estimated residual patient volume. In some cases, the expected
drain volume can also include an expected ultrafiltration volume.
The system can determine, using one or more computing devices, if
the measured volume of fluid is less than the minimum drain
volume.
[0021] The system can post an alarm if the measured volume of fluid
is less than the minimum drain volume. The system can continue the
dialysis treatment if the measured volume of fluid is not less than
the minimum drain volume. The system can update the estimated
residual patient volume to be the difference between the expected
drain volume and the measured volume.
[0022] A connector can allow for a sealed container (e.g., a bag)
to be opened without introducing contamination. The connector can
include a port configured to attach to a container for containing
fluid, the port having a septum configured to seal the container, a
tube connector configured to attach to a tubing element, and a
spike attached to the tube connector. The spike can pierce the
septum of the bag port when the tube connector is advanced toward
the port such that a fluid connection if formed from the container
through the port, through a fluid pathway in the spike, through the
tube connector, and into the tube element. A seal member can be
attached at a first end to the port and attached at a second end to
the tube connector. The seal member can provide a seal between the
bag port and the tube connector such that the spike can be advanced
to pierce the septum without exposing the spike or septum to the
outside environment.
[0023] The seal member can be a bellows member. One or more guide
members can be configured to guide the spike toward the septum as
the spike is advanced.
[0024] In some embodiments, one or more protective cover pieces can
be included and can be configured to maintain the tube connector at
distance from the port at which the spike does not pierce the
septum. The one or more protective cover pieces can be removable to
allow the spike to be advanced to pierce the septum.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Certain embodiments of the inventions will now be discussed
in detail with reference to the following figures. These figures
are provided for illustrative purposes only, and the inventions are
not limited to the subject matter illustrated in the figures.
[0026] FIG. 1 is a perspective view of an example embodiment of an
APD cycler.
[0027] FIG. 2 is another perspective view of the APD Cycler of FIG.
1 with the heater/weigh scale cover in an open position.
[0028] FIG. 3 is another perspective view of the APD Cycler of FIG.
1 with the pinch valve access door in an open position.
[0029] FIG. 4 is a perspective view of an example embodiment of a
disposable set for use with the APD cycler of FIG. 1.
[0030] FIG. 5 is a perspective view of an example embodiment of a
disposable set for use with the APD cycler with no heater bag or
drain bag attached thereto.
[0031] FIGS. 6A-E illustrate an example embodiment of a connector
for attaching the heater bag to a tubing element.
[0032] FIG. 7 is another perspective view of the APD Cycler of FIG.
1 with the disposable set of FIG. 4 loaded therein.
[0033] FIG. 8 is a close-up perspective view of the APD Cycler of
FIG. 1 with the pinch valve access door removed to show the tubing
elements aligned with the corresponding pinch valves.
[0034] FIG. 9 is a cross sectional view of the pinch valves and
tubing of FIG. 8.
[0035] FIGS. 10A-C illustrate a heater tray assembly including load
cells that are toggleable between enabled and disabled
configurations.
[0036] FIG. 11 schematically shows how the heater tray can transfer
multiple different values of loads into the multiple load
cells.
[0037] FIG. 12 schematically shows an example embodiment of a
pressure-based volume measurement system that can be used by the
APD cycler of FIG. 1.
[0038] FIG. 13 is a flowchart that shows an example embodiment of a
method of determining a volume of fluid using the pressure-based
measurement system of FIG. 12.
[0039] FIG. 14 is a flowchart that shows an example embodiment of a
method of applying an automated peritoneal dialysis treatment to a
patient.
[0040] FIG. 15 is a flowchart that shows an example embodiment of a
method of handling a drain stage in an automated peritoneal
dialysis treatment.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0041] The following detailed description is now directed to
certain specific embodiments of the disclosure. In this
description, reference is made to the drawings wherein like parts
are designated with like reference numerals throughout the
description and the drawings.
[0042] FIG. 1 is a perspective view of an example embodiment of an
Automated Peritoneal Dialysis (APD) system 10, often referred to
herein as an APD cycler 10. The APD cycler 10 can include a housing
5. A cover 2, such as a heater/weigh scale cover, can be attached
to the housing 5 (e.g., using one or more hinges) so that the
heater/weigh scale cover 2 can open and close like a door. In FIG.
1, the heater/weigh scale cover 2 is shown in the closed position.
An access region, such as pinch valve access door 52, can be
attached to the housing 5 (e.g., using one or more hinges) so that
the pinch valve access door 52 can open and close. The pinch valve
access door 52 is shown in the closed configuration in FIG. 1. A
closure, such as latch 54, can be used to maintain the pinch valve
access door 52 in the closed position. A closure, such as a latch
(not shown in FIG. 1), can also be used to maintain the
heater/weigh scale cover 2 in the closed position. The heater/weigh
scale cover 2 and/or the pinch valve access door 52 can be
maintained closed using closures such as pins, or a snap or
friction fit structure, or in any other suitable manner.
[0043] The APD cycler 10 can include a user output, such as display
12, and a user input, such as control buttons 15, which can be
recessed and/or fully contained within the profile of the housing
5, to prevent the display 12 and buttons 15 from being damaged, for
example, during movement of the APD cycler 10. The display 12 can
be configured to provide information to the user and to request
information from the user, as described herein. The buttons 15 can
be configured to receive user input as described herein. In some
embodiments, the display 12 can be a touch screen, thereby reducing
the number of buttons 15, or allowing for the buttons 15 to be
omitted.
[0044] FIG. 2 is a perspective view of the APD cycler 10 with the
heater/weigh scale cover 2 in the open position. A heater tray
assembly 70 can be positioned in a recess formed in the housing 5
so that it is protected from unintentional forces that can cause
errors in weight measurements taken using the heater tray 72. In
some embodiments, the heater tray assembly 70 can be removable from
the recess, for example to provide access to components of the
weigh scale. The heater tray assembly 70 can be substantially
enclosed on the bottom and sides by walls 71 and the top of the
heater tray assembly 70 can be open so that components of a
disposable set 30 can be placed therein, as shown in FIG. 5. The
housing 5 can include a housing lip 3 that extends up to receive a
cover lip 4 formed on the underside of heater/weigh scale cover 2.
The cover lip 4 can mate with the housing lip 3 to form a
containment chamber 6 therebetween, and these components can be
configured to form a seal, for example, so that negative pressure
can be maintained inside the containment chamber 6, as described
herein. The housing 5 can have a channel 74 leading away from the
heater tray assembly 70, and the housing lip 3 can extend
substantially around the channel 74. Grooves 7 and 8 can be formed
in the housing lip 3. Many alternatives are possible. For example,
the heater/weigh scale cover 2 can be configured to seal directly
with the walls 71 of the heater tray assembly 70.
[0045] FIG. 3 is a perspective view of the APD cycler with the
pinch valve access door 52 in the open position. For example, the
user can disengage the latch 54 to open the pinch valve access door
52, thereby exposing the pinch valve actuators 60. In the
embodiment shown in FIG. 3, the APD cycler 10 can be configured to
receive a disposable set 30.
[0046] FIG. 4 is a perspective view of an example embodiment of a
disposable set 30 that includes an fill container, such as a heater
bag 20, and a drain container, such as a drain bag 22. The heater
bag 20 can be filled with fluid to be warmed before being introduce
to the patient, and the drain bag 22 can be used to receive fluids
drained from the patient. The disposable set 30 can include
multiple supply lines 31 and 32 for introducing fluid into the
heater bag, although in some embodiments a single supply line can
be used. A patient line 34 can direct fluid from the heater bag 20
to the patient, and then from the patient to the drain bag 22. A
drain line 36 can be used to remove fluid from the drain bag 22.
Branch connections, such as Y connections 33, 35 and 37, and tubing
elements 28, 29, 38, and 39 can be positioned as shown in FIG. 4 to
connect the components of the disposable 30 to each other to
provide a suitable flow path for fluid through the system. In some
embodiments, all or portions of the tubing elements 27, 28, 29, 38,
and 39 and/or portions of the supply lines 31 and 32, patient line
34, and drain line 36 can be flexible such that the pinch valve
actuators 60 can pinch the tubing elements 27, 28, 29, 38, 39 to
close off fluid passageways to direct the flow of fluid through the
system, as described herein. Connectors (not shown) can be included
on the ends of the supply line lines 31 and 32, on the end of
patient line 34, and/or on the end of the drain line 36. Various
suitable connectors can be used to connect these lines to a fluid
source, patient catheter, or waste receptacle as appropriate. A
sterile connector 40 can be used to provide access to the heater
bag 20, as shown in greater detail in FIGS. 6A to 6D.
[0047] A low recirculation volume set can be created by providing
long tubing lines 28 and 29 (e.g., in some cases at least about 25
cm or 50 cm or more in length) thereby moving Y connection 35 close
to the patient connector on patient line 34. Fresh dialysis
solution flows down line 28 and spent dialysis and ultrafiltration
are fluids drained through line 29. Line 34, wherein both fresh
dialysis solution and spent dialysis fluids flow, can be shortened
(e.g., to less than or equal to about 10 cm, 5 cm, 1 cm, or less)
so that the recirculation volume would be low or generally
negligible. (Note: A 4 mm ID tube contains 1 ml of fluid for each 8
cm of length.) In some embodiments, lines 28 and 29 could remain as
they are shown and patient line 34 be replaced by a double D
extrusion that terminates at the patient connection limiting the
recirculation volume to the volume within the catheter itself.
[0048] FIG. 5 is a perspective view of an example embodiment of a
disposable set 30 that does not include the heater bag 20 or the
drain bag 22. In some embodiments, the heater bag 20 and/or the
drain bag 22 can be reusable, while the tubing and other components
shown in FIG. 5 can be disposable. In some embodiments, the entire
heater bag 20 and/or the drain bag 22 can be disposable as well.
The disposable set 30 can be a low cost unit. In some embodiments,
the disposable set 30 can include multiple (e.g., four) Y
connections 33, 35, and 37; multiple (e.g., nine) lengths of
tubing; and multiple (e.g., six) connectors, which can have tip
protectors. Many alternatives are possible. For example a 4-way
connection can be used instead of a Y connection, thereby reducing
the number of connections and lengths of tubing (e.g., one less
connection and one less length of tubing than shown in FIG. 5).
[0049] FIGS. 6a-e illustrate an example embodiment of the connector
40 that is configured to provide a fluid connection between the
heater bag 20 and the tubing 38. In some embodiments, the connector
40 can be attached to the heater bag 20 and/or to the tube 38 when
the disposable set is manufactured.
[0050] FIG. 6a is a perspective view of the connector 40 with
protective covers 41 and 42 in place. A heater bag port 21 can be
attached to the heater bag 20 and a tube connector 43 can be
attached to the tubing 38. When engaged, the protective covers 41
and 42 can substantially secure and constrain the tube connector 43
from moving relative to heater bag port 21. FIG. 6b is a cross
sectional view of the connector 40 with the protective covers 41,
42 engaged. The protective covers 41, 42 can include tabs that abut
against the heater bag port 21 and against the tube connector 43 to
prevent them from being advance towards each other. A port adapter
18 can be bonded to the inside surface of heater bag 20 using heat
welding, ultrasonic welding, RF welding, solvent welding, adhesive
welding, or other suitable manner. Adapter port 18 can be bonded to
the inside surface of the heater bag 20 rather than the outside
surface of the heater bag 20 to reduce the likelihood that the
adapter port may be dislodged during shipping and handling. The
heater bag port piece 21 can be bonded to the adapter port 18 using
an adhesive or other suitable manner. In some embodiments, the
heater bag adapter 21 and the adapter port 18 can be integrally
formed as a single piece. The heater bag port 21 can have a septum
19 that prevents fluid from transferring between the heater bag 20
and the tube 38.
[0051] FIG. 6c shows the connector 40 with the protective cover 42
removed, exposing the flexible bellows member 45 that connects the
heater bag port 21 to the tube connector 43. The bellows member 45
can be bonded on a first end to the heater bag port 21 and on a
second end to the tube connector 43, using an adhesive or any other
suitable manner. FIG. 6d shows connector 40 with both protective
covers 41 and 42 removed. FIG. 6e is a cross sectional view of the
connector 40 with the protective covers 41 and 42 removed. With the
protective covers 41 and 42 removed, the tube connector 43 can be
pushed towards the heater bag port 21, thereby collapsing the
bellows member 45. The bellows member 45 can be made from a
flexible, elastomeric, and/or resilient material, such as silicone.
The tube connector 43 can have a spike 47 connected thereto. As the
tube connector 43 moves toward bag port 21, the spike 47 can
penetrate the septum 19, thereby aseptically initiating a fluid
connection between the tube 38 and the interior of the heater bag
20. In some embodiments, the tube connector 43 and spike 47 can
retract after the septum 19 is penetrated, but a fluid connection
can continue to exist between the heater bag 20 and the tube 38
because fluid may pass through the hole in the pieced septum 19
formed by the spike 47. In some embodiments, the tube connector 43
and spike 47 can be retained in the advanced position (not shown)
with the tip of the spike 47 protruding through the septum 19,
thereby allowing fluid to flow through the septum 19 via the fluid
pathway formed on the inside of the spike 47. The heater bag port
21 can include guide walls 49 that generally surround the tip of
the spike 47, and the guide walls 49 can direct the spike 47
through the septum 19 to reduce the risk that the spike 47 would
unintentionally puncture the bellows member 45 or another wall in
the heater bag 20, or that the heater bag port 21 would dislodge,
thereby generating a fluid leak.
[0052] Thus, the connector 40 can provide a barrier that seals off
the interior of the heater bag 20 until the spike 47 is advanced to
puncture the septum 19, for example when the user is ready to begin
a dialysis procedure. In some embodiments, the heater bag 20 can be
prefilled with a fluid for delivery to a patient, and the septum 19
can provide a barrier to maintain that fluid inside the heater bag
20 until the septum 19 is punctured. The connector can also prevent
bacteria or other contaminants from entering the heater bag 20 or
other components of the disposable set 30. The connector 40 can
allow for the seal to the heater bag 20 to be broken without
introducing any bacteria or other contaminants, thereby maintaining
the sterile environment inside the disposable set 30. For example,
the user can advance the spike 47 to pierce the septum 19 without
touching the spike 47, and the bellows member 45 can function to
seal off the inside of the connector 40 in both the advanced and
retracted positioned discussed above. The connector 40 can be
designed so that it is permanently connected to the heater bag 20
and tube 38 and not designed to be disconnection therefrom during
normal use. For example, the bellows member 45 can be adhered to
the heater bag port 21 and to the tube connector 43, which can be
adhered to the heater bag 20 and the tube 38, respectively. Thus,
in some embodiments, the connector 40 does not allow for
disconnection of the tube 38 from the heater bag 20. Rather, the
connector 40 remains connected thereto during use, and can be
transitioned from a closed state to an open state by advancing the
spike 47 through the septum 19 without opening the connector 40 or
otherwise exposing the interior of the connector 40 to the
surrounding environment. Also, the connector 40 can be configured
to remain open after it has been initially opened (e.g., advanced
to pierce the septum 19), and not reseal or close if the connector
is later set to the retracted position. Thus, the connector 40 may
be designed to not be capable of repeated transitions between open
and closed configurations.
[0053] Various alternative connectors can be used to connect the
tube 38 to the heater bag 20. For example, in some embodiments, the
heater bag 20 can have a male or female luer connector attached
thereto and can be configured to selectively attach to a
corresponding male or female luer attached to the tube 38. This
embodiment may be advantageous if the heater bag is intended to be
reused and if the tubing is intended to be disposable, because the
male luer can be disengaged from the female luer to allow the
heater bag to be disconnected from the tube 38. In some
embodiments, the tube 38 can be connected directly to the adapter
port 18 of the heater bag 20 with no septum or other barrier to
seal the heater bag 20. This configuration can be used, for
example, if the heater bag is not prefilled, so that it is inserted
empty into the ADP cycler 10 and is thereafter filled with fluid
via the supply lines 31, 32. In some cases, user can mix two or
more fluids (e.g., having different dextrose concentrations) to
form a mixture (e.g., having an intermittent dextrose
concentration), which can allow for better ultrafiltration control.
A prefilled heater bag can be used, thereby reducing the cost of
the therapy. In some embodiments, the supply lines 31 and 32 can be
omitted, for example, if the prefilled heater bag is sufficiently
large to contain the full volume of treatment fluid (e.g., for
pediatric or small-mass patient use, or using a large volume heater
bag.)
[0054] With reference now to FIG. 6c, the tube 39 can be directly
connected to an adapter port 17, which can be bonded to the inside
of the drain bag 22 in a manner similar to that described in
connection with the adapter port 18 above. Thus, in some
embodiments, no septum or other barrier is provided between the
tube 39 and the drain bag 22. In some embodiments, a connector
similar to the connector 40 can be used to seal the drain bag 22
until the use. Also, detachable connectors (e.g., male and female
luer connectors) can be used so that the drain bag 22 is removable
from the tube 39.
[0055] The disposable set 30 can be sterilized. For example, the
heater bag 20 can be prefilled and then steam sterilized. The
prefilled heater bag 20 can be referred to as the wet side of the
disposable set 30. The dry side of the disposable set 30 can
include the lines 31, 32, 34, 36; tubing 27, 28, 29, 38, 39;
multi-line connections, such as Y connections 33, 35, 37; empty
drain bag 22; and end connections (not shown). The dry side of the
disposable set 30 can be assembled and sterilized, such as by using
ethylene oxide gas, Gamma radiation, or Electron Beam
sterilization. The wet side and the dry side of the disposable set
30 can exit their respective sterilizers in a sterile barrier
"isolation" environment and can be aseptically joined by the
connector 40. Some suitable sterile barrier "isolation"
environments, and other details relating to the sterilization are
described in chapters 12 and 14 of Aseptic Pharmaceutical
Manufacturing II (ISBN: 0-935184-77-5). Many alternatives are
possible. For example, the wet side and dry side of the disposable
set 30 can be joined in a clean room environment while an Electron
Beam sterilizes the connection. In embodiments in which the heater
bag 20 is not prefilled, the entire disposable set 30 can be
assembled as the dry side and can be sterilized after assembly
using any of the suitable sterilization techniques described
herein.
[0056] In some embodiments, the bags 20 and 22 can have ports
located on the side. The side port location can allow the cycler to
be designed such that its overall dimensions are compact (e.g., to
better fit into an airplane overhead storage bin).
[0057] FIG. 7 is a perspective view of the APD cycler 10 with the
disposable set 30 positioned therein. The heater bag 20 can be
positioned, for example, at the bottom of the heater tray assembly,
near one or more heating elements (not shown) such that fluid
introduce into the heater bag 20 can be warmed before delivery to
the patient. The drain bag 22 can also be placed into the
containment chamber 6 along with the heater bag 20, as shown. The Y
connections 33 can fit into the grooves 7 and 8, and can be
configured to form a substantially vacuum tight seal when the
heater/weigh scale cover 2 is closed. For example, the Y
connections 33 can include O-rings that are sized larger than the
grooves 7 and 8 such that the O-rings are compressed when inserted
into the grooves 7 and 8 to form the seal. The connector 40 and
portions of the tubing elements 38 and 39 can be positioned in the
channel 74. The disposable set 30 can be positioned such that pinch
valves 60 are located directly beneath flexible portions of the
tubing such that the pinch valves 60 can resiliently deform
portions of the tubing to prevent the flow of fluid therethrough,
to thereby direct the flow of fluid through the system. The APD
cycler 10 can be configured to hold the flexible pieces of tubing
in position over the corresponding pinch valves 60 during use. In
some embodiments, the underside of the pinch valve access door 52
can have grooves or slots (not shown) configured to receive the
tubing therein to position the pieces of tubing above the pinch
valves 60 when the pinch valve access door 52 is closed. A series
of clamps (not shown) can be included to position the pieces of
tubing above the corresponding pinch valves 60.
[0058] FIG. 8 is a partial perspective view of the APD cycler 10
with the pinch valve access door 52 omitted from view. The supply
lines 31 and 32 are positioned above the pinch valves 60d and 60e,
respectively, such that the pinch valves 60d and 60e can control
the flow of fluid through the supply lines 31 and 32, such as when
a fresh volume of fluid is transferred into the heater bag 20. The
tubing element 28 that interconnects the patient line 34 to the
heater bag 20 can be positioned above the pinch valves 60c and 60g
such that the pinch valves 60c and 60g can control the flow of
fluid through the tubing element 28, such as when the fresh, heated
fluid is transferred from the heating bag 20 to the patient line 34
for delivery to the patient. The tubing element 27 that
interconnects the patient line 34 to the drain bag 22 is positioned
above the pinch valves 60b and 60f such that the pinch valves 60b
and 60f can control the flow of fluid through the tubing element
27, such as when fluid is drained from the patient via the patient
line 34 to the drain bag 22. The drain line 36 can be positioned
over pinch valve 60a such that the pinch valve 60a can control the
flow of fluid through the drain line 36, such as when fluid that
was drained from the patient is transported from the drain bag 22
out via the drain line 36. In the illustrated embodiment, the
tubing elements 27 and 28 that connect to the patient line 34 can
have multiple (e.g., two) pinch valves 60b and 60f or 60c and 60g
associated therewith, so that if one pinch (e.g., 60c) valve fails
or malfunctions, another pinch valve (e.g., 60g) can still close
the tubing, thereby reducing the likelihood that a valve
malfunction would adversely affect the patient (e.g., overfilling
or excess drainage).
[0059] FIG. 9 is a partial cross sectional view taken through the
pinch valve 60c and 60g which are used to control the flow of fluid
through the tubing element 28. The other pinch valves 60 can be
similar to the pinch valves 60c and 60g in construction and
operation. The pinch valves 60 can be spring close/vacuum open
pinch valves, which are biased toward a closed position (as shown
in FIG. 9) by a spring 64, and can be retracted to an open position
by negative pressure. This configuration can reduce the amount of
noise produced by the pinch valves as compared to a system in which
the valves are biased open by one or more biasing members, (e.g.,
springs) and forced to a closed position by pressure (negative or
positive pressure). In some embodiments, a rigid plate 61 can have
holes for receiving the pinch valve plungers 60, so that only the
tips of the plungers are visible to the user above the plate 61. A
flexible, resilient diaphragm 62 can create a seal between the
plate 61 and the actuator housing 68. Retainers, such as nuts 66,
can attach the diaphragm 62 to the plungers 60, creating a seal
around the guide stems 65, which can be integrally formed with the
plungers 60. The springs 64 can bias the pinch valve plungers 60
towards the closed position, for example by pressing against the
underside of the retainer nuts 66. The actuator housings 68 can be
configured to have negative pressure selectively applied to them,
for example, by a pump (not shown). When sufficient negative
pressure is applied to an actuator housing 68, the biasing force of
the spring 64 can be overcome and a portion of the flexible,
resilient diaphragm 62 can be pulled down into the actuator housing
68, thereby compressing the spring 64 and retracting the pinch
valve plunger 60 down into the open position in which fluid is
allowed to flow through the corresponding tubing.
[0060] In some embodiments, the pinch valves 60 can be configured
so that, when in the closed position, they can occlude PVC tubing
that has an internal diameter of about 4 mm and an outer diameter
of about 6 mm when fluid that has a temperature of about 10.degree.
C. is present in the tubing. The pinch valves 60 can be configured
such that negative pressure of about -7 psig is able to retract the
pinch valve plungers 60 to the open position. For example, the
internal diameter of the actuator housings can be at least about
0.62 inches and/or less than or equal to about 0.75 inches,
although values outside these ranges may also be used. By using a
stronger spring 64, the pinch valve 60 can be biased more strongly
toward the closed position and can be capable of occluding stronger
tubing. However, if a stronger spring is used, the amount of
negative pressure that is used to retract the plunger 60 also
increases. If a weaker spring 64 is used than that shown in the
illustrated embodiment, the less negative pressure would be needed
to retract the plunger 60 but the pinch valve 60 would also have
less force to occlude the tubing in the closed position. For
example, springs can be selected so that the pinch valves 60 can
retract under a negative pressure of at least about -7.0 psig
and/or less than or equal to about -10.0 psig.
[0061] Both pinch valves 60c and 60g can isolate the patient so
that replenish fluid from supply line 31 is not inadvertently
delivered to the patient during the replenish phase even in the
event of a failure of a single pinch valve. Similarly, both pinch
valves 60b and 60f (not shown in FIG. 9) can isolate the patient
when fluid is being transferred to the drain line from the interim
drain bag, even in the event of a failure of a single pinch
valve.
[0062] FIG. 10A is a perspective view of an example embodiment of a
heater tray assembly 70. The heater tray 72 can have walls 71 that
substantially enclosed the sides and bottom of the heater tray 72,
and a cutout 73 that provides a pathway to the channel 74 when the
tray 72 is inserted into the APD cycler 10 as shown in FIG. 3. The
bottom of the heater tray 72 can slope toward the side with cutout
73 such that when the bags 20 and 22 are placed in the heater tray
72, the fluid is urged to run towards the side with the cutout 73.
The heater tray 72 can be supported by multiple (e.g., three or
more) load cells 75, which can be located at the corners of a
triangle such that two of the load cells are located on the lower
side of the sloped bottom of the heater tray 72, since more weight
would generally be applied to the lower side. Other numbers of load
cells 75 can be used. For example, a single load cell 75 can be
used, but would generally be exposed to more extremes in load
conditions than the set of three load cells 75 shown in the
illustrated embodiment. Other numbers of load cells 75 can be used,
such as at least 2 load cells, 4 load cells, or 5 load cells, or
more. The load cells can operate in parallel such that the
measurements taken from each of the load cells is combined to
provide a total weight measurement.
[0063] On or more of the load calls 75 can be toggleable between a
disabled configuration in which the load cell 75 is not configured
to measure weight applied to the tray 72 and an enabled
configuration in which the load cell 75 is capable of measuring
weight applied to the tray 72. Thus, when the APD cycler 10 is not
in use, the load cells 75 can be set to the disabled configuration
to prevent the load cells 75 from being damaged, for example, by
relatively extreme forced that can be unintentionally applied
during transportation of the APD cycler 10. When in use, the user
can transition the load cells 75 to the enabled configuration.
[0064] FIG. 10B is a close-up cross sectional view taken through
the center of the load cell 75 on the high end of the heater tray
72. The load cell 75 can include a support bar 76 located, for
example, on the underside of the load cell 75. The load cell can
have a main body 80 that can be movable with respect to the support
bar 76, such that when force is applied to the load cell 75, the
movement of the main body 80 can apply force to a sensor, such as a
strain gauge (not shown), that generates data corresponding to the
force applied to the load cell 75. The support bar 76 can be
secured directly to the housing 5 of the APD cycler 10 by
connectors, such as screws 77. The screws 77 can have sealing
members, such as O-Rings or elastomeric washers (not shown), that
create a seal between the heads of the screws 77 and the housing 5
to prevent air from leaking into the containment chamber when it is
evacuated to generate a negative pressure as described herein. A
connector, such as screw 78, can pass through a hole 83 in the
heater tray 72 and can engage a threaded bore 82 formed in the load
cell 75, thereby attaching the heater tray 72 to the load cell 75.
The load cell 75 can be secured to tray 72 in any other suitable
manner, such as using an adhesive or snap fitting. The hole 83 can
be threaded to secure the tray 72 to the load cell 75, or the hole
83 can be unthreaded and tray 72 can be secured to the load cell 75
by the head of the screw 78 abutting against the step of the recess
81 formed in the base of the heater tray 72.
[0065] A connector, such as an isolation screw 79 can be used to
set the load cell to the enabled or disabled configurations. In
some embodiments, the head of the isolation screw 79 can fit under
the head of the screw 78. The recess 81 can be large enough to
receive the isolation screw 79 in addition to the screw 78, and a
channel 86 that is wide enough to receive the head of the isolation
screw can be formed below the recess 81 so that the isolation screw
79 can be tightened and loosened (advanced and retracted) to toggle
the load cell between the enabled and disabled configurations. In
FIG. 10B, the isolation screw 79 is set to the enabled position. To
set the isolation screw to the enabled position, the isolation
screw can be turned in the loosening (e.g., counter-clockwise)
direction. The head of the isolation screw 79 can abut against the
underside of the head of the screw 78, thereby preventing the user
from unintentionally loosening the isolation screw 79 to the point
where it would disengage from the load cell 75. The isolation screw
79 is thus retracted to a position in which it does not engage the
support bar 76. Thus, when a force is applied to the heater tray
72, the isolation screw 79 does not prevent the force from being
applied to the sensor to generate a reading of the weight applied
to the tray 72.
[0066] FIG. 10C is a close-up cross sectional view of the load cell
75 with the isolation screw 79 in the disabled position. The
isolation screw 79 can be tightened (e.g., turned in the clock-wise
direction) so that the isolation screw 79 is advanced until it
engages the support bar 76. The hole 85 can either be threaded or
unthreaded. In some embodiments, the hole 85 is not required to be
threaded. For example, the isolation screw 79 can be advance
through a threaded bore 84 formed in the load cell 75 until the
isolation screw is engaged with both the support bar 76 and the
main body 80 portion of the load cell 75 to prevent movement
therebetween and to insulate the sensor from force applied to the
load cell 75. When force is applied to the heating tray 72, it is
transferred though the isolation screw 79 into the support bar 76
instead of to the sensor. In some embodiments, an O-ring can be
positioned between the head of the isolation screw 79 and the inner
surface of the channel 86. In some embodiments, the isolation screw
79 can cause the O-ring to press tightly against the inner surface
of the channel 86 to seal off the interior of the heater tray 72
from the area below the heater tray 72. Thus, if liquid is spilled
into the heater tray 72, it will not leak down into the load cells
75. The screw 78 can have an O-ring or other seal, or because it is
not intended to be moved during use (as is the isolation screw 79),
the threads of the screw 78 can form a seal with the bore 83. The
user can insert a tool (e.g. a hex screwdriver) through the recess
81 and into the channel 86 to engage the head of the isolation
screw 79 to transition the isolation screw 79 between the enabled
and disabled positions.
[0067] In some embodiments, during the manufacturing process, the
left end of the support bar 76 is initially formed connected to
left end of the main body 80 and is separated from main body 80
after the threaded bore 84 for isolation screw 79 has been drilled
and tapped. Thus, the threads formed in the bore 84 in the support
bar 76 can mate with the isolation screw 79 without putting any
load on load cell 75.
[0068] Many alternatives are possible. For example, in some
embodiments, the hole 85 at the base of the channel 86 can be
threaded to secure the heater tray 72 to the isolation screw 79.
Thus, when the isolation screw 79 is in the disabled position,
force applied to the tray 72 is transferred through the isolation
screw 79 and to the support bar 76 instead of to the sensor. In
some embodiments, the isolation screw 79 can engage threads of the
support bar 76 to secure the isolation screw 79 to the support bar
76 when in the disabled position, thereby preventing the isolation
screw 79 (or the tray 72 which is secured to the isolation screw
79) from moving with respect to the support bar 76. In some
embodiments, the isolation screw 79 is not required engage the
support bar 76 but is advanced to a point where the isolation screw
79 abuts against the support bar 76, or against the housing 5, or
other rigid, stationary portion of the APD cycler 10 so that force
on the tray 72 does not move the tray 72 toward the load cell 75
because the force is transferred through the isolation screw 79 to
the support bar 76, housing 5, or other rigid, stationary portion
of the APD cycler 10. Thus, in some embodiments, the hole 85 is
threaded, but the bore 84 through the load cell 75 is not required
to be threaded. Also, in some embodiments, the isolation screw 79
can be displaced from the load cell 75. For example, the isolation
screw 79 can pass through a threaded hole in the base of the tray
72 that is not associated with the load cell 75 (e.g., positioned
adjacent to the load cell). The isolation screw 79 can be advanced
until it abuts against the housing 5 below the tray 72. Thus, when
a force is applied to the tray 72, the force will be carried
through the isolation screw 79 to the housing 5 and not to the load
cell 75.
[0069] FIG. 11 schematically shows how the heater tray 72 can
transfer multiple (e.g., three) different values of loads into the
three load cells 75 that support the tray 72, the heater bag 20,
and the interim drain bag 22. The weight of the heater tray 72 and
the bags 20, 22 that it contains are represented by weight W in
FIG. 11. The loads that are transmitted into the load cells 75 are
represented by L.sub.1, L.sub.2, and L.sub.3. The dimensions
X.sub.1 and Y.sub.1 represent the distance that the center of
gravity of weight W is away from the centerlines that run through
the three load cells. The sum of the loads and weights equals zero
and the sum of the moments about each of the centerlines through
the load cells equal zero. This yields 3 equations with 3
unknowns.
.SIGMA.F=W-L.sub.1-L.sub.2-L.sub.3=0 Equation 1
.SIGMA.M.sub.X-Axis=W*Y.sub.1-L.sub.1Y.sub.2=0 Equation 2
.SIGMA.M.sub.Y-Axis=W*X.sub.1+L.sub.3X.sub.2-L.sub.2X.sub.2=0
Equation 3
These 3 equations can be solved for L.sub.1, L.sub.2, and L.sub.3.
Equation 2 can be solved directly for L.sub.1.
L.sub.1=(Y.sub.1/Y.sub.2)*W Equation 4
This expression for L.sub.1 can then be substituted in Equation 1
for L.sub.1 so that L.sub.2 can be expressed in terms of W and
L.sub.3 yielding the following:
L.sub.2=W-W*(Y.sub.1/Y.sub.2)-L.sub.3 Equation 5
This expression for L.sub.2 can then be substituted for L.sub.2 in
Equation 3 yielding
W*X.sub.1+L.sub.3*X.sub.2-W*X.sub.2+W*X.sub.2*(Y.sub.1/Y.sub.2)*+L.sub.3*-
X.sub.2=0. Solving for L.sub.3 yields the following:
L.sub.3=W*(X.sub.2-X.sub.1)/(2*X.sub.2)-W/2*(Y.sub.1/Y.sub.2)
Equation 6
The expression for L3 in Equation 6 can be substituted for L3 in
Equation 5 yielding the following:
L.sub.2=W*(X.sub.2+X.sub.1)/(2*X.sub.2)+W/2*(Y.sub.1/Y.sub.2)
Equation 7
[0070] The geometry of the containment chamber 6 and of the
solution bags 20, 22 can prevent all of the weight of the heater
and drain bags 20, 22 from being placed on a single load cell. Each
of load cells 75 can have a capacity of at least about 5 Kg and/or
less than or equal to about 20 Kg, although other values outside
these ranges may also be used. In some embodiments, the load cells
75 can each have a nominal capacity of about 10 Kg with a safe
overload of about 15 Kg and be suitable for use in this
application. In some examples, a maximum fluid volume that would
fit into the containment chamber can occur at after the initial
drain stage at the start of the therapy. For example, the patient
may have an initial drain volume of twice their prescribed fill
volume (e.g., 3000 ml) resulting in an initial drain of 6000 ml,
and a full 6 liter heater bag may be present in the APD cycler 10
as well. This 12 liter (about 12 kg) load would be distributed
across the three load cells per equations 4, 6, and 7 based upon
the location of the combined center of gravity of the heater tray
72, the heater bag 20 and the interim drain bag 22.
[0071] In some embodiments, the APD cycler can use the load cells
75 to measure the amount of the fluid contained within the heater
bag 20 and/or the drain bag 22. Thus, as the heater bag 20 is
filled with fresh dialysis solution, the load cells 75 can measure
the amount of fluid in the heater bag 20 and the system can cease
filling the heater bag 20 when the desired volume of fluid is
contained therein. The load cells 75 can also measure the weight of
the fluid as it is transferred from the heater bag 20 to the
patient, and the patient fill stage can end when the desired volume
of fluid is transferred to the patient. Similarly, the load cells
75 can measure the weight of the spent dialysate and accompanying
ultrafiltration fluid that is from the patient into the drain bag
22, and when the drain stage is complete, the system can measure
the amount of fluid drained from the patient. Thus, the amount of
ultrafiltration can be measured. Then the fluid can be drained from
the drain bag 22 to exit the ADP cycler 10. Thus, the drain bag 22
can be an intermediate drain bag 22 since the fluid is first
drained to the intermediate drain bag 22 to be measured, and it is
then drained from the system after measurement. Likewise, the
heater bag 20 can serve not only the purpose of providing a
reservoir for heating the fluid, but can also serve as an
intermediate fill bag for measuring the fresh fluid before it is
delivered to the patient.
[0072] In some embodiments, the APD cycler 10 can use a backup
volume monitor to measure the volumes of fluid that are delivered
to the patient and/or drained from the patient. The backup volume
monitor can be used to confirm measurements made by load cells 75.
In some embodiments, the backup volume monitor can use negative
(sub-atmospheric) pressure and make calculations based on the ideal
gas law. In some embodiments, the accuracy of the backup volume
monitor has a lower level of accuracy as compared to primary
monitoring system (e.g, load cells 75), and the backup volume
monitor can be used to verify that the primary monitoring system
(e.g., load cells 75) are functioning properly.
[0073] FIG. 12 is schematic representation of an example embodiment
of an implementation of the pressure-based volume measurement
system that can be used by the APD cycler 10. As described herein,
the containment chamber 6 can be sealed so that a negative pressure
can be maintained therein. The containment chamber can have a total
volume V.sub.cont. The heater bag 20 and drain bag 22 can be
positioned inside the containment chamber 6. The heater bag 20 can
contain a volume of fluid V.sub.heater, and the drain bag 22 can
contain a volume of fluid V.sub.drain, so that the volume of air
inside the containment chamber 6 V.sub.cont air is equal to
V.sub.cont-V.sub.heater-V.sub.drain. A reference chamber 90 can
have a volume V.sub.ref and can also be sealable to maintain
negative pressure therein. The reference chamber 90 can be
connected to the containment chamber 6 by a pathway 92. A valve 94
can be positioned on the pathway 92 such that the pathway can be
selectively opened and closed. A vacuum pump 96 can be connected to
the reference chamber 90 via a pathway 98. A valve 99 can
selectively open and close the pathway 98.
[0074] Negative pressure can be applied to the containment chamber
6 by opening the valves 94 and 99 and running the vacuum pump 96
until the desired negative pressure is achieved. Then the valve 94
can be closed sealing the negative pressure within the containment
chamber 6. Negative pressure can be applied to the reference
chamber 90 by closing the valve 94 and opening the valve 99 and
running the vacuum pump 96 until the desired negative pressure is
achieved. Then the valve 99 can be closed to seal the negative
pressure within the reference chamber 90. Thus, the containment
chamber 6 and the reference chamber 90 can be independently set to
different negative pressures. The containment chamber 6 and the
reference chamber 90 can each have one or more pressure sensors to
measure the pressure contained therein. Various suitable pressure
sensors can be used. For example, Motorola's Freescale MPX2053 and
MPX2010 differential pressure sensors or Fujikura's XFDM
differential pressure sensors can be used measuring the pressure of
the containment chamber 6 and the reference chamber 90 during
pressure measurements.
[0075] Many alternatives are possible. For example, a separate
pathway can connect the vacuum pump 96 to the containment chamber 6
and a valve can selectively open and close that separate pathway.
In this embodiment, negative pressure can applied to the
containment chamber 6 without opening the reference chamber 90. In
some embodiments, the reference chamber 90 and containment chamber
6 can have independent vacuum pumps. Although much of the
description herein describes negative (sub-atmospheric) pressure
being applied to the containment chamber 6 and reference chamber
90, in some embodiments, the pump 96 can be used to apply positive
pressure to the containment chamber 6 and/or to the reference
chamber 90.
[0076] FIG. 13 is a flowchart that shows and example embodiment of
a method 1300 for determining the volume of the fluid contained in
the heater bag 20 or drain bag 22. At block 1302, a first pressure
P.sub.1cont is applied to the containment chamber. In some
embodiments, the pressure P.sub.1cont can be at least about -0.1
psig and/or less than or equal to about -1.0 psig. An example of a
suitable pressure is about -0.5 psig. Other values outside these
ranges may also be used. Although several examples provided herein
are described using a pressure of -0.5 psig to the containment
chamber 6, other pressures can be used. In some cases, the pressure
P.sub.1cont can be set to about 0.0 psig, by, for example, venting
the containment chamber to the pressure outside the APD cycler 10.
In some embodiments, a positive or negative pressure is used for
P.sub.1cont so test whether the containment chamber 6 is sealed
properly. For example, if P.sub.1cont were intentionally set to
atmospheric pressure, the system would not be able to detect
leakage from the containment chamber. Thus, in some embodiments,
the containment chamber 6 is maintained as a non-atmospheric
pressure (e.g., a negative pressure such as -0.1 psig or more)
during the use. At block 1304, a second pressure P.sub.1ref is
applied to the reference chamber 90. The pressure P.sub.1ref can be
al east about -5.0 psig and/or less than or equal to about -9.0
psig, and can be about -7.0 psig, although other pressures outside
these ranges can be used. In some embodiments, the pressure
P.sub.1ref is set to a more negative pressure than P.sub.1cont. For
example, P.sub.1ref can be set to a negative pressure value that is
5 times or 10 time or 20 times greater (in the negative direction)
than P.sub.1cont. Other multipliers can be used.
[0077] At block 1306, the valve 94 is opened and, at block 1308,
the pressures in the containment chamber 6 and the reference
chamber 90 equalize through the pathway 92. At block 1310, the
substantially equalized pressure is measured. The equalized
pressure can be recorded in some embodiments. For example, the APD
cycler 10 can include a controller that comprises a computer
readable storage medium (non-transitory storage medium). The
equalized pressure can be recorded in the computer readable medium.
In some cases, the equalized pressure is stored for later
reference, and in some cases the equalized pressure can be stored
for only as long as needed to make the other calculations, as
described herein.
[0078] At block 1312, the volume of air inside the containment
chamber is calculated based on the equalized pressure. When the
pressure P.sub.1ref is set to a more negative pressure than
P.sub.1cont, generally, after pressure equalization, the equalized
pressure will generally be lower as the volume V.sub.cont air
increases, because a larger volume of air inside the containment
chamber 6 will have more air available to move into the reference
chamber 90 to compensate for the higher negative pressure therein.
In some cases, the computer readable medium can contain a lookup
table that includes air volume values that correspond to equalized
pressure values. The controller can use the lookup table to
identify the V.sub.cont air value that corresponds to the measured
equalized pressure. In some embodiments, the controller can
comprise a formula or algorithm for calculating the V.sub.cont air
from the measured equalized pressure. The lookup table and/or
formula can be generated from or confirmed with actually measured
values previously made. One example formula that can be used is as
follows:
V.sub.cont
air=((P.sub.2Ref-P.sub.1Ref)/(P.sub.1Cont-P.sub.2Cont))*V.sub.Ref
[0079] The measurement can be performed substantially isothermally
with the air temperatures maintained at a constant value. Thus, the
APD cycler 10 can have a temperature sensor and heating and/or
cooling elements for controlling the temperature inside the APD
cycler 10. In some embodiments, the temperature sensor and heating
element used for heating fluid inside the heating bag 20 can be
used, although other dedicated sensors and heating and/or cooling
elements can be used. It is noted that the temperature is not
required to remain substantially constant during the entire
process, so long as the temperature is substantially the same at
block 1310 (when the equalized pressure is measured) as it is at
blocks 1302 and 1304 when the pressures of the containment chamber
6 and reference chamber 90 are set. In some embodiments, a
threshold level of temperature difference is considered acceptable,
such as, for example, about 2.degree. C., 1.degree. C., 0.5.degree.
C., or less. Other threshold acceptable temperature differences may
be used as well. In some cases, the process can be performed
quickly (substantially adiabatically) so that essentially no
thermal energy is transferred from the gases being used. Thus, in
some embodiments, the calculations can be based on Boyle's law in
which temperature is substantially constant. In some embodiments,
the temperature is not controlled and is not assumed to be
constant. Rather, temperature measurements can be taken (e.g.,
using one or more temperature sensors configured to measure the
temperature in the containment chamber 6 and/or the reference
chamber 90) and considered in making the calculation of the
V.sub.cont air. One example formula that can be used is as
follows:
V cont air = V Ref ( ( P 2 Ref T 2 Ref - P 1 Ref T 1 Ref ) / ( P 1
Cont T 1 Cont - P 2 Cont T 2 Cont ) ) ##EQU00001##
[0080] At block 1314, the volume of fluid in the heater bag 20 or
the drain bag 22 can be determined from the calculated volume of
air inside the containment chamber 6 V.sub.cont air using the
equation V.sub.cont air=V.sub.cont-V.sub.heater-V.sub.drain. If
V.sub.heater is known, then V.sub.drain can be determined, and if
V.sub.drain is known, then V.sub.heater can be determined. Thus, in
some embodiments, during the operation of the APD cycler, the
volume of fluid inside the heater bag 20 and the volume of fluid
inside the drain bag 22 are not both changed in between sequential
pressure measurements made using the pressure-based volume
monitoring system.
[0081] In some embodiments, the volume V.sub.ref of the reference
chamber 90 can be at least about 0.25 liters and/or less than or
equal to about 5.0 liters. Some examples of V.sub.ref can be about
0.5 liters, 1.0 liter, 2.0 liters, or 3.0 liters. Other values
outside of these ranges can be used. In some embodiments, a low
volume reference volume can be used to keep the size of the APD
cycler 10 relatively compact in size so that it can be easily
transported (e.g., fitting into an airplane overhead compartment to
facilitate travel by the user). The maximum volume of the heater
bag 20 and the drain bag 22 can be of the same size or of different
sizes, and each be at least about 2 liters and/or less than or
equal to about 10 liters, and can be about 6 liters, although
values outside these ranges may also be used. For example, if the
heater bag 20 is not configured to be replenished (e.g., supply
lines 31 and 32 omitted), then the maximum volume of the heater bag
20 may be larger than 10 liters. The volume of the containment
chamber 6 can be at least about 5 liters and/or less than or equal
to about 20 liters, and can be about 16 liters in some cases,
although other values outside these ranges can be used.
[0082] Table 1 contains calculations made using embodiments having
the reference chambers 90 of volumes of 0.5 liters, 1.0 liter, 2.0
liters, and 3.0 liters in which the reference chamber was evacuated
to -7.0 psig. The containment chamber 6 having a volume of 16
liters was used and measurements were made with both the heater bag
20 and drain bag having 3 liters of fluid therein, resulting in a
V.sub.cont air value of 10 liters, and also with the heater bag 20
empty with 3 liters of fluid in the drain bag, resulting in a
V.sub.cont air of 13 liters. The containment chamber 6 was
evacuated to about -0.5 psig. The two pressures were allowed to
equilibrate as described herein, and the pressure changes are shown
in Table 1. Using a reference volume of 3 liters, the difference in
equalized pressure for an empty heater bag 20 versus a heater bag
20 containing 3.0 liters of fluid is 1.5 psi-1.2188 psi=0.2812 psi.
This indicates that an inaccuracy in pressure reading of 0.001 psi
now corresponds to a fluid measurement error of about 10 grams, or
about 10 ml. The volumes and pressures can be adjusted to provide a
system which is more or less sensitive to error and/or which
exposes the APD cycler 10 to more or less negative pressure.
TABLE-US-00001 TABLE 1 Boyle's Law with -7 psig Vacuum Applied to
the Reference Chamber Delta Pref Delta PCont VairCont P2ref P1ref
P1Cont P2Cont Vref 6.1905 -0.3095 10.0000 -0.8095 -7.0000 -0.5000
-0.8095 0.5000 5.9091 -0.5909 10.0000 -1.0909 -7.0000 -0.5000
-1.0909 1.0000 5.4167 -1.0833 10.0000 -1.5833 -7.0000 -0.5000
-1.5833 2.0000 5.0000 -1.5000 10.0000 -2.0000 -7.0000 -0.5000
-2.0000 3.0000 6.2593 -0.2407 13.0000 -0.7407 -7.0000 -0.5000
-0.7407 0.5000 6.0357 -0.4643 13.0000 -0.9643 -7.0000 -0.5000
-0.9643 1.0000 5.6333 -0.8667 13.0000 -1.3667 -7.0000 -0.5000
-1.3667 2.0000 5.2813 -1.2188 13.0000 -1.7188 -7.0000 -0.5000
-1.7188 3.0000
[0083] In some embodiments, the negative pressure inside the
containment chamber does not exceed a maximum negative value of
about -2.0 psig. Thus, the containment chamber 6 does not need to
be constructed to withstand high negative pressures larger than
-2.0 psig, thereby reducing the size, and weight, and cost of
manufacturing for the APD cycler 10, and allowing the APD cycler 10
to be used as a gravity/vacuum APD cycler 10 in which the
containment chamber 10 has O-rings and/or seals which may not be
capable of reliably withstanding extreme negative pressures, for
example, as described herein. Other configurations of APD cyclers
can be used. In some embodiments, the reference chamber 90 can be
exposed to high levels of negative pressure (e.g., -7.0 psig), and
the reference chamber 90 can be constructed to more easily
withstand high negative pressure than can the containment chamber 6
because the reference chamber is a simpler structure (e.g., not
having a hinging cover to allow the user access to the interior,
and/or not having flexible tubes and bolts exiting the chamber with
O-rings and seals). Applying a relatively low negative pressure to
the containment chamber can also result in less noise during
operation of the APD cycler 10, as compared to a system that
applies a higher negative pressure therein.
[0084] Table 2 contains calculations made using reference chambers
90 of volumes of 0.5 liters, 1.0 liter, 2.0 liters, and 3.0 liters
in which the reference chamber 90 was vented to atmospheric
pressure instead of being brought to a negative pressure. A
containment chamber 6 with a volume of 16 liters was used and
measurements were made with both the heater bag 20 and drain bag
having 3 liters of fluid therein, resulting in a V.sub.cont air
value of 10 liters, and also with the heater bag 20 empty with 3
liters of fluid in the drain bag, resulting in a V.sub.cont air of
13 liters. The containment chamber 6 was evacuated to about -1.5
psig. The two pressures were allowed to equilibrate, and the
pressure changes are shown in Table 2. Using a reference volume of
3 liters, the difference in equalized pressure for an empty heater
bag 20 versus a heater bag 20 containing 3.0 liters of fluid is
0.3462 psi-0.2813 psi=0.0649 psi. This indicates that an inaccuracy
in pressure reading of 0.001 psi now corresponds to a fluid
measurement error of about 50 grams (or about 50 ml), which in some
cases may be unacceptable to the dialysis community. However, this
embodiment does not expose the APD cycler to negative pressures of
over 1.5 psig.
TABLE-US-00002 TABLE 2 Boyle's Law with -1.5 psig Vacuum in the
Containment Chamber Delta Pref Delta PCont VairCont P2ref P1ref
P1Cont P2Cont Vref -1.4286 0.0714 10.0000 -1.4286 0.0000 -1.5000
-1.4286 0.5000 -1.3636 0.1364 10.0000 -1.3636 0.0000 -1.5000
-1.3636 1.0000 -1.2500 0.2500 10.0000 -1.2500 0.0000 -1.5000
-1.2500 2.0000 -1.1538 0.3462 10.0000 -1.1538 0.0000 -1.5000
-1.1538 3.0000 -1.4444 0.0556 13.0000 -1.4444 0.0000 -1.5000
-1.4444 0.5000 -1.3929 0.1071 13.0000 -1.3929 0.0000 -1.5000
-1.3929 1.0000 -1.3000 0.2000 13.0000 1.3000 0.0000 1.5000 1.3000
2.0000 -1.2188 0.2813 13.0000 1.2188 0.0000 1.5000 1.2188
3.0000
[0085] Table 3 contains calculations made using reference chambers
90 of volumes of 0.5 liters, 1.0 liter, 2.0 liters, and 3.0 liters
in which the reference chamber 90 was vented to atmospheric
pressure instead of being brought to a negative pressure. The
containment chamber 6 had a volume of 16 liters was used and
measurements were made with both the heater bag 20 and drain bag
having 3 liters of fluid therein, resulting in a V.sub.cont air
value of 10 liters, and also with the heater bag 20 empty with 3
liters of fluid in the drain bag, resulting in a V.sub.cont air of
13 liters. The containment chamber 6 was evacuated to about -7.0
psig. The two pressures were allowed to equilibrate, and the
pressure changes are shown in Table 3. Using a reference volume of
3 liters, the difference in equalized pressure for an empty heater
bag 20 versus a heater bag 20 containing 3.0 liters of fluid is
1.6154 psi-1.3125 psi=0.3029 psi. This indicates that an inaccuracy
in pressure reading of 0.001 psi now corresponds to a fluid
measurement error of about 10 grams (about 10 ml).
TABLE-US-00003 TABLE 3 Boyle's Law with -7 psig Vacuum in
Containment Chamber Delta Pref Delta PCont VairCont P2ref P1ref
P1Cont P2Cont Vref -6.6667 0.3333 10.0000 -6.6667 0.0000 -7.0000
-6.6667 0.5000 -6.3636 0.6364 10.0000 -6.3636 0.0000 -7.0000
-6.3636 1.0000 -5.8333 1.1667 10.0000 -5.8333 0.0000 -7.0000
-5.8333 2.0000 -5.3846 1.6154 10.0000 -5.3846 0.0000 -7.0000
-5.3846 3.0000 -6.7407 0.2593 13.0000 -6.7407 0.0000 -7.0000
-6.7407 0.5000 -6.5000 0.5000 13.0000 -6.5000 0.0000 -7.0000
-6.5000 1.0000 -6.0667 0.9333 13.0000 -6.0667 0.0000 -7.0000
-6.0667 2.0000 -5.6875 1.3125 13.0000 -5.6875 0.0000 -7.0000
-5.6875 3.0000
[0086] Although many of the example embodiments described herein
disclose the use of negative pressure applied to the containment
chamber 6 and/or to the reference chamber 90, in some embodiments,
positive pressure may be used. In some embodiments, the negative
pressure applied to the containment chamber 6 can be used not only
for determining the volume of fluid being transferred, but also to
draw fluid into the containment chamber 6, such as when draining
fluid from a patient, as described herein. In some cases, the use
of negative pressure, instead of positive pressure, can reduce
occurrence of problems during treatment, such as air being pushed
into the bags 20 and 22 by positive pressure or unintentional
overfilling due to force applied on the bags 20 and 22 by positive
pressure.
[0087] FIG. 14 is a flowchart that schematically illustrates an
example embodiment of a method 1400 of treating a patient, for
example, by performing automated peritoneal dialysis (APD). At
block 1402, the APD cycler 10 is set up. The heater bag 20 and the
interim drain bag 22 can be placed into the heater tray 72, and the
disposable set 30 can be loaded, for example, as described herein.
The system can perform line priming and integrity testing of the
disposable set 30 and any other suitable preliminary set up
procedures. In some cases, a filled heater bag 20 is placed on the
heater tray 72 in order to reduce therapy costs and to minimize the
time before the therapy can begin. However, a partially filed, or
even an empty bag can be placed on the heater bag when two or more
solutions are mixed (e.g., introduce through the supply lines 31
and 32) to form a solution that has, for example, an intermediate
Dextrose concentration.
[0088] At block 1404, the system can determine the initial volume
of air in the containment camber. The containment chamber can be
set to a first pressure (e.g, about -0.5 psig). The reference
chamber can be set to a second pressure (e.g., about -7 psig). The
pressures can be allowed to equalize and the initial volume of the
air in the containment chamber can be calculated as described
herein (e.g., using Boyle's Law). This can be used to determine the
initial volume of fluid, if any, in the heater bag 20.
[0089] In some embodiments, the equalized pressure in the
containment chamber 6 is at a negative pressure (e.g., about -1.5
psig) after equalization. The negative pressure can be used to draw
fluid into the drain bag 20 for the initial drain at block 1406.
Pinch valves 60b and 60f are opened and fluid is drain through
patient line coil 34 past open pinch valve 60b, past open pinch
valve 60f, through tubing 27, through sealing Y connector 33a,
through tubing 39, and into the interim drain bag 22. In some
embodiments, the negative pressure in the containment chamber 6 can
be adjusted before or during the drain to regulate the drainage of
fluid.
[0090] The load cells 75, under the heater tray 72, can measure the
change in weight of the interim drain bag 20 and provide continuous
feedback to the controller of the APD cycler 10. The controller can
calculate the flow rate of fluid into the drain bag 22. The fluid
flow rate typically can initially be generally between about 125
and 250 ml/min, or can be less than or equal to about 200 ml/min,
for example, and can generally start to slow down as the patient's
peritoneum empties of fluid. At block 1408, the controller can
recognize when the flow rate has dropped below a threshold value,
or some other indicator that the drain of the patient's peritoneum
is nearing completion, and in response the controller can reduce
the negative pressure inside the containment chamber 6 towards the
end of the drain when the flow rate slows and approaches the "no
flow" state. The negative pressure can be released gradually as the
flow rate slow or can be released relatively quickly. In some
embodiments, the negative pressure can be reduced to a value of at
least about -0.5 and/or less than or equal to -1.2 when the flow
rate drops below a "low flow" rate. The pressure can be set to
values outside these ranges when the "low flow" rate is reached.
Reducing the pressure at the end of the drain can reduce the level
of pain or discomfort experienced by the patient when negative
pressure is applied to the patient's peritoneum when little or no
fluid is left to drain. The negative pressure can be maintained
substantially constant until the fluid flow naturally slows, at
which time the negative pressure can be reduced to further slow the
flow rate until the lowest pressure is applied at the end of the
drain as the flow rate stops. This differs from the gradual
reduction in suction pressure that naturally occurs with gravity
based drainage as the fluid level in the interim drain bag
gradually rises as it fills, gradually reducing the drain suction
throughout the entire drain phase.
[0091] A "slow flow" threshold can be set to trigger the reduction
of the negative pressure. A "slow flow" event can be triggered
(causing a reduction in pressure) if the flow rate remains below
the "slow flow" rate for a predetermined time, such as at least
about 1 minute and/or less than or equal to about 10 minutes; or at
least about 3 minutes and/or less than or equal to about 6 minutes.
A "no flow" threshold can be set to trigger the stop of the drain
stage (e.g., by closing the pinch valves 60b and 60f. A "no flow"
event can be triggered (causing a termination of the drain stage)
if the flow rate remains below the "slow flow" rate for a
predetermined time, such as at least about 1 minute and/or less
than or equal to about 10 minutes; or at least about 3 minutes
and/or less than or equal to about 6 minutes. In some embodiments,
the "slow flow" and "no flow" thresholds are adjustable. For
example, the default "slow flow" flow rate threshold for an adult
patient with a 2000 ml fill volume could be 2% of the fill volume
or 40 ml/min and the default flow rate threshold for "no flow"
could be 0.5% of the 2000 ml fill volume or 10 ml/min. These values
could be decreased to 32 ml/min and 8 ml/min, 20 ml/min and 5
ml/min, or 16 ml/min and 4 ml/min if the patient drained slower
than normal. The same is true for non-adult patients wherein, for
example, the default "slow flow" flow rate threshold for an
adolescent patient with 1000 ml fill volume could be 2% of the fill
volume or 20 ml/min and the default flow rate threshold for "no
flow" could be 0.5% of the 1000 ml fill volume or 5 ml/min. These
values could be decreased to 16 ml/min and 4 ml/min, 12 ml/min and
3 ml/min, or 8 ml/min and 2 ml/min if the patient drained slower
than normal. In some embodiments, the "slow flow" threshold can be
at least about 5 ml/min and/or less than or equal to about 50
ml/min. Values outside these ranges can be used. In some
embodiments, the "no flow" rate can be at least about 1 ml/min
and/or less than or equal to about 15 ml/min. Values outside these
ranges can be used.
[0092] When the drain phase ends, pinch valves 60a and 60f can
close and the volume of fluid drained, as measured by the load
cells, can be recorded. At block 1410, the volume of fluid in the
drain bag 22 can be determined using the pressure-based system. The
vacuum in containment chamber 6 can be set to a first value (e.g.,
decreased to about -0.5 psig) and the vacuum in the reference
chamber 90 (3 liter size) can be set to a second value (e.g.,
increased to about -7 psig). After the two pressures are recorded,
the two chambers can be connected and the pressure within can be
allowed to equalize. The new pressure readings can be recorded and
used along with the previous pressure readings and the previously
calculated pre-drain containment chamber air volume to calculate
the volume of fluid that was drawn into the containment chamber 6
during drain. If the fluid volume as measured by the load cells
differs by more than a threshold amount or percentage (e.g., 10%)
from that calculated using the pressure-based system, an alarm will
be posted. Thus, if the volume measured by the pressure-based
system is between 90% and 110% of the value that was reported by
the load cell system, the therapy can continue. If it is not, an
alarm can be posted. Other error tolerance percentages may be used,
such as, for example, any suitable value that is at least about 3%
and/or less than or equal to about 15%.
[0093] If no alarm was posted, the post drain containment chamber
air volume can be recorded and fluid can be delivered to the
patient from the heater bag at block 1412. In some embodiments, the
temperature is measured to determine if the fluid is of a suitable
temperature for delivery to the patient, and the temperature of the
fluid may be adjusted if needed. The vacuum in containment chamber
6 can be set to about -0.1 psig or to any other suitable pressure,
or it can be vented to the surrounding pressure. Pinch valves 60g
and 60c can be opened and fluid can flow out of heater bag 20,
through tube 38, through a sealing Y connection 33b, through tube
28, through Y connection 35, and into patient line 34. Because
gravity propels the fluid as it flows, air does not enter the
patient line. For example, the air can simply remain in the heater
bag 20. In some embodiments, a small positive pressure can be
applied to facilitate the flow of fluid out of the heater bag 20,
or a small negative pressure (e.g., -0.1 psig) can be used to
prevent air from entering the patient.
[0094] The load cells 75 can measure the change in weight of the
heater bag 20 and provide continuous feedback to the controller.
The fluid flow rate typically will be between about 125 and 250
ml/min and will generally not slow down unless the patient line 34
is restricted. Pinch valves 60g and 60c can close when the volume
delivered reaches the programmed fill volume. The volume delivered,
as measured by the load cells can be recorded in a
computer-readable medium.
[0095] At block 1414, the volume of fluid in the heater bag, and
thus the volume of fluid delivered to the patient, can be
determined. The vacuum in containment chamber 6 will be set to a
first value (e.g., increased to about -0.5 psig) and the vacuum in
the reference chamber 90 can be set to a second value (e.g., about
-7 psig). After the two pressures are recorded, the two chambers
are connected and the pressure within can be allowed to
substantially equalize. The new pressure reading(s) are recorded
and used along with the previous pressure readings and the
previously calculated post drain/pre-fill containment chamber air
volume to calculate the volume of fluid that was delivered to the
patient. If the fluid volume as measured by the load cells differs
by more than a threshold value (e.g., 10%) from that calculated
using the pressure-based system, an alarm will be posted. The
calculated post fill air volume of containment chamber 6 can be
recorded.
[0096] The fluid can be left in the peritoneum of the patient for a
time known as the dwell period. At block 1416, during the dwell
period, the vacuum in containment chamber 6 can be set to about
-0.1 psig, or to any other suitable pressure (e.g., at least about
-0.05 and/or less than or equal to about -0.2), or vented to
atmospheric pressure, and pinch valve 60a can be opened. Gravity
can cause the interim drain bag 22 to empty through line 39,
through sealing Y connection 33, and into and through drain line
36. The load cells 75 can measure the change in weight of interim
drain bag 22 and provide continuous feedback to the controller. The
fluid flow rate typically will be between about 125 and about 250
ml/min and will generally not slow down unless the interim drain
bag 22 is empty. Pinch valve 60a can close when the flow rates
stops and the transfer ended if the volume moved is within a
threshold value (e.g., 100 ml) of the volume previously drained
from the patient. The volume that was transferred from the drain
bag 22, as measured by the load cells, can be recorded.
[0097] At block 1418, the volume of fluid drained from the drain
bag 22 is determined using the pressure system. The pressure in
containment chamber 6 can be set to a first value (e.g., about -0.5
psig) and the pressure in the reference chamber can be set to a
second value (e.g., about -7 psig). After the two pressures are
recorded, the two chambers can be connected and the pressure within
can be allowed to substantially equalize. The new pressure readings
can be recorded and used along with the previous pressure readings
and the previously calculated post fill containment chamber air
volume to calculate the volume of fluid that was transferred out of
the drain bag 22. If the fluid volume as measured by the load cells
differs by more than a threshold value (e.g., 10%) from that
calculated using Boyle's Law, an alarm will be posted. The
calculated post drain transfer air volume of containment chamber 6
can be recorded.
[0098] If the heater bag needs to be replenished prior to the next
fill, fluid can be transferred into the heater bag at block 1420.
The containment chamber can be evacuated to about -1.5 psig, or to
any other suitable value. Pinch valves 60d or 60e are opened as
appropriate and fluid flows from the supply or last bag through
lines 31 or 32, through Y connection 37, through tube 27, through
sealing Y connection 33, through line 38, and into heater bag 20.
Load cells 75 measure the change in weight of the heater bag 20 and
provide continuous feedback to the controller. The fluid flow rate
typically will initially be between about 125 ml/min and 250
ml/min, or can be less than or equal to about 200 ml/min. The flow
rate may start to slow down if the reservoir (e.g., supply bag)
empties of fluid. In some embodiments, gravity can be used to
transfer the fluid into the heater bag 20. The pressure in
containment chamber 6 can be allowed to reduce (e.g., to a value
that is at least about -0.5 psig and/or less than or equal to about
-1.2 psig, or to any other suitable value) towards the end of the
replenish phase if flow slows substantially.
[0099] When the replenish phase ends, pinch valve 60d or 60e can
close and the volume of fluid replenished, as measured by the load
cells, is recorded. At block 1422, the system can determine the
volume of fluid in the heater bag 20 using the pressure system. The
pressure in containment chamber 6 can be set to a first value
(e.g., about -0.5 psig) and the pressure in the reference chamber
90 can be set to a second value (e.g., about -7 psig). After the
two pressures are recorded, the two chambers can be connected and
the pressure within can be allowed to substantially equalize. The
new pressure reading(s) can be recorded and used along with the
previous pressure readings and the previously calculated
pre-replenish containment chamber air volume to calculate the
volume of fluid that was drawn in to the containment chamber 6. If
the fluid volume as measured by the load cells differs by more than
a threshold value (e.g., about 10%) from that calculated using the
pressure-based system, an alarm can be posted. The system can then
return to block 1406 and repeat the cycle if needed.
[0100] Many variations to the method 1400 are possible. For
example, blocks 1420 and 1422 may be omitted if the heater bag 20
contains enough fluid for the next patient fill stage. Also, block
1408 can be an optional feature, not present in all embodiments.
The order of certain described events may be changed. For example,
the heater bag 20 could be replenished at blocks 1420 and 1422
before the drain bag 22 is drained at blocks 1416 and 1418 if space
permits. The treatment can begin with a drain stage, as described
above, in order to drain fluid that was left in the patient after
the final fill stage of the previous treatment session. The
treatment session can have a fill stage (near the end of the
treatment) that is not drained, so that the fluid (e.g., high
density dextrose solution) is left in the patient during the time
between treatments (e.g., which can be performed daily). In some
cases, the treatment session can have a fill stage before the first
drain stage, for example, if the patient did not receive an
undrained fill stage at a previous treatment. In some cases, the
treatment session can begin with a drain stage even if there was no
undrained fill stage at a previous treatment (which may result in a
low volume initial drain), thereby ensuring that the patient has
been cleared before the first fill to reduce the risk of
overfilling a patient. Other variations are possible.
[0101] In some embodiments, the load cells and/or the
pressure-based measurement system are able to determine when the
interim drain bag 22 and the heater bag 20 contain fluid. If fluid
does not flow from the bags when they contain fluid as expected, an
alarm can be posted. If the flow rate unexpectedly drops or stops,
an alarm can be posted.
[0102] The APD cycler 10 can include a controller configured to
controller the APD process. The controller can control the pinch
valves 60, the vacuum pump 96, the valves 94 and 99, the heating
elements, the alarms, etc. If fluid flow slows or stop during a
drain, an alarm, such as a low level, continuously sounding audible
alarm can be posted for a time (e.g., at least about 1 second
and/or less than or equal to about 10 seconds, or any other
suitable time) so that the patient can roll over or otherwise
change position. The system can automatically resume the drain for
an additional time (e.g., at least about 1 minute and/or less than
about 10 minutes) during which time the condition that caused the
alarm may be addressed by the user. If the fluid flow remains slow
or stopped after the 5 minute delay, a slightly higher level,
continuously sounding audible alarm can be posted for a suitable
time (e.g., at least about 1 second and/or less than or equal to
about 10 seconds, or any other suitable time) so that the patient
can roll over or otherwise change position. The system will
automatically resume the drain for an additional time (e.g., at
least about 1 minute and/or less than about 10 minutes) during
which time the condition that caused the alarm may be addressed by
the user. If the fluid flow remains slow or stopped after the 5
minute delay, an even higher level, continuously sounding audible
alarm can be posted, and can continue until the STOP button is
pressed to silence the alarm. The system can automatically resume
drain after the STOP button is pushed and can continue without
posting an additional alarm for a time (e.g., at least about 1
minute and/or less than about 10 minutes) during which time the
condition that caused the alarm may be addressed. Many variations
are possible. A beeping alarm may be used. In some cases, a
continuous alarm, instead of a beeping alarm, is used as it can be
detected by devices used by hearing-impaired individuals to alert
them when their phone is ringing or the door bell is sounding. In
some cases, the beeping alarms would be ignored by these devices as
are doors closing, cars backfiring, etc. In some embodiments, the
alarms can sound for 3 seconds, and the system can delay 5 minutes
between alarms, although other times may be used, as described
above.
[0103] In some embodiments, the audible alarm can be suppressed by
plugging a suppression device into the parallel output device port.
The suppression device can signal a parent, or caregiver (e.g., via
a pager or text message or email or other notification). The
suppression device can also signal a light signaling device, a bed
shaker, or a vibrating pager in the event the patient is
hearing-impaired. The suppression device could be incorporated into
the cycler itself and turned ON or OFF using the operator
interface, or it may be an external device.
[0104] The APD cycler 10 can post an alarm when less fluid than
expected is drained from the patient to the drain bag 22, possibly
indicating a kink or other obstruction in the line (e.g., if the
patient rolls onto the line while sleeping). In some embodiments,
the system will not post the alarm if close to the full expected
amount of fluid was drained. The amount of fluid that failed to
drain can be recorded and the volume of fluid to be delivered in
later fill stages may be reduced to reduce the risk of overfilling
the patient. For example, if several drain stages end prematurely
without fully draining the patient's peritoneum and if the full
fill volumes are delivered to the patient, the residual fluid left
by each incomplete drain can add up resulting in overfilling and
discomfort and potential injury to the patient. This may be the
case for a system that sets the patient volume to zero for each
cycle.
[0105] Thus, in some embodiments, the APD cycler 10 can track the
volume of fluid in the patient across multiple fill and drain
cycles and does not set the patient volume to zero, unless the
measured drained volume exceeded the expected drain volume (e.g.,
volume delivered at the last fill stage, plus expected
ultrafiltration (UF) from the patient, plus residual volume left
from previous cycles). In some embodiments, the system may also set
the patient volume to zero after the initial drain, regardless the
measured drain volume. In some embodiments, an expected drain
volume can be calculated using fill information from the previous
treatment session and the patient volume is automatically set to
zero after the initial drain. In some embodiments, the user can
input an expected UF value that indicates how much extra fluid is
expected to be removed from the patient's body at each drain stage
(in excess of the infused fluid from the fill stage).
[0106] The system can be configured to determine whether to post an
alarm when a drain stops before the expected amount of fluid is
drained. In some embodiments, the system can post an alarm if less
than a threshold amount of fluid was successfully drained, but if
the amount of drained fluid is deemed generally close to the full
expected drain value, no alarm is posted and the treatment
continues. The threshold amount can be calculated as a percentage
(e.g., at least about 75% and/or less than or equal to about 95%,
or about 85%) of the full expected patient volume at the start of
the drain (e.g., the volume of fluid delivered at the previous fill
stage plus any residual fluid remaining from previous cycles), or
of the full expected drain volume (e.g., the volume of fluid
delivered at the previous fill stage plus any residual fluid
remaining from previous cycles plus the expected UF volume).
[0107] Table 4 contains a comparison between two systems when
consecutive incomplete drains occur during a therapy. In the first
example show, the system is configured to continue treatment
instead of posting an "incomplete drain" alarm if about 85% of the
previously filled fluid was drained, regardless of whether residual
fluid remains in the patient from previous cycles. In the second
example shown, the system is configured to continue treatment
instead of posting an "incomplete drain" alarm if about 85% of the
current expected patient volume is successfully drained.
TABLE-US-00004 TABLE 4 (values in milliliters) First Example Second
Example Phase Per Cycler Actual Per Cycler Actual Initial Drain
Start 2000 2000 2000 2000 End 0 0 0 0 Fill 1 Start 0 0 0 0 End 3000
3000 3000 3000 Dwell 1 Start 3000 3000 3000 3000 End 3000
3300(110%) 3300 3300(110%) Drain 1 Start 3000 3300 3300 3300 Ends
@85% End 450 750 495 495 Fill 2 Start 0 750 495 495 End 3000 3750
3495 3495 Dwell 2 Start 3000 3750 3495 3495 End 3000 4050(135%)
3795 3795(127%) Drain 2 Start 3000 4050 3795 3795 Ends @85% End 450
1500 569 569 Fill 3 Start 0 1500 569 569 End 3000 4500 3569 3569
Dwell 3 Start 3000 4500 3569 3569 End 3000 4800(160%) 3869
3869(129%) Drain 3 Start 3000 4800 3869 3869 Ends @85% End 450 2250
580 580 Fill 4 Start 0 2250 580 580 End 3000 5250 3580 3580 Dwell 4
Start 3000 5550 3580 3580 End 3000 5950(185%) 3880 3880(129%)
[0108] As shown in Table 4, in the first example, the patient can
be overfilled by about 10% after one incomplete drain, by about 35%
after two incomplete drains, by about 60% after three incomplete
drains, and by about 85% after four incomplete drains. In the
second example, the patient is overfilled by about 10% after one
incomplete drain, by about 27% after two incomplete drains, by
about 29% after three incomplete drains, and again by about 29%
after four incomplete drains. In the second example, the system
tracks of the expected patient volume and limits the magnitude of
any potential overfills.
[0109] FIG. 15 is a flowchart that illustrates an example
embodiment of a method 1500 for handling a drain stage. If the
system receives an indicator that the drain may be completed (e.g.,
the flow rate stops or drops below a threshold "slow flow" or "no
flow" level), the system can perform the method 1500. At block
1502, the amount of fluid drained from the patient is measured. The
measurement can be made by the load cells 75, other weight scale,
and/or by the pressure-based system described herein. At block
1504, the minimum drain volume can be calculated. For example, the
minimum drain volume can be the expected drain volume (e.g., the
volume of fluid delivered at the previous fill stage plus any
residual fluid remaining from previous cycles plus the expected UF
volume) multiplied by a minimum drain percentage (e.g., about 85%).
At block 1506, the system can determine whether the measured drain
volume is less than the minimum threshold drain volume. If the
measured drain volume is less than the minimum threshold drain
volume, the process 1500 can proceed to block 1508 and post an
"incomplete drain" alarm. The alarm can be designed to awaken the
patient so that the patient can shift position to unblock the drain
line or take other appropriate action. If the measured drain volume
is not less than the minimum threshold drain volume, the process
1500 proceeds to block 1510, and updates the expected patient
volume. If the measured volume of drained fluid exceeds the
expected drain amount, the estimated patient volume can be set to
zero. If the measured drained fluid is less than the expected drain
volume, the system can add the difference to the estimated patient
volume, at block 1514, which may be used for future
calculations.
[0110] The overfill limit can be calculated from the prescribed
fill volume, the minimum drain percentage and the expected per
cycle UF as follows:
Fill Limit=(Prescribed Fill Volume+Per Cycle UF)/Min Drain %
In the embodiment shown in the second example of Table 1, the fill
limit is calculated to be (3000+300)/0.85=3882 ml.
[0111] Conversely, the minimum drain % can be calculated from a
selected fill limit, the prescribed fill volume and the per cycle
UF as follows:
Min Drain %=(Prescribed Fill Volume+Per Cycle UF)/Fill Limit
In the embodiment shown in the second example of Table 1, the min
drain percentage is calculated to be (3000+300)/3882=0.85=85%. If
the user wishes to limit the amount of potential overfilling to a
different number (e.g., 3500 ml), the appropriate drain percentage
can be calculated (e.g., (3000+300)/3500=0.94=94%). The user can
input the desired over fill limit, the expected UF, and the per
cycle fill volume, and the system can select an appropriate minimum
drain percentage. If the user selects a low maximum fill limit,
then the system will be more sensitive to incomplete drains (e.g.,
posting an alarm if only a small amount of fluid fails to drain),
and if the use selects a relatively high maximum fill limit, then
the system will only post an alarm is a relatively large amount of
fluid fails to drain.
[0112] In some embodiments, bypassing a minimum drain volume alarm
can cause the system to deliver less fluid in later fill stages,
thereby further preventing patient overfilling. In some
embodiments, an additional cycle can be added to the treatment
session to compensate for the amount of fluid that is reduced from
the fill stages. The new fill volume can be determined by dividing
the remaining therapy volume, excluding last fill volume, by the
number of remaining cycles (including the newly added cycle). If
needed, multiple additional cycles can be added, for example, if
the predicted patient volume at the end of the dwell would still
exceed a desired volume after one additional cycle is added. This
method of reducing the later fill volumes can result in all of the
available therapy volume being used while preventing the patient
from being filled to a volume that is greater than a desired
limit.
[0113] In some embodiments, the system can record the
ultrafiltration values for each therapy and calculate an average UF
for the patient. If the programmed expected UF varies by more than
a threshold amount (e.g., about 50%) from this average value the
system can notify the user that the inputted expected UF may be
inappropriate. The system can display the average UF value to the
patient and ask the patient to confirm the original value or input
a new expected UF value. If a patient uses different Dextrose
solutions, the UF can be recorded and an average can be calculated
for multiple (e.g., 2 or 3 or more) different Dextrose
concentrations. The UF target for a therapy can then be
programmable for each of the different Dextrose concentrations. In
some embodiments, the system can use the average UF value if no
expected UF value is provided by the user.
[0114] The APD cycler 10 can operate on 100-250V 50/60 Hz AC. A
universal voltage power supply can be used. In some cases the
heating elements can be powered by a dedicated power supply. A
single heating element may be used, or multiple heading elements
(e.g., 2 or 3 or more) can be used. When the system is powered "ON"
the heating elements can be configured in series. A comparator
circuit can check the voltage drop across a circuit to determine
whether the input power was 90-132 volts or 180-275 volts or some
other value. If the input power is 180-275VAC, the heaters can
continue to operate in series. If the power is 90-132VAC the
heaters can be switched to operate in parallel. The system can
retain the heater configuration after momentary power glitches.
[0115] The system can use pulse width modulation (PWM) techniques
to further refine the power output by the heater elements. For
example, a 400 watt heater could be powered "ON" for 50 msec and
"OFF" for 50 msec to produce an output of 200 watts. This technique
could also be used in lieu of the series/parallel configuring of
the heater elements to allow the system to operate throughout the
100-250 V 50/60 Hz AC range.
[0116] The heater elements can be isolated from the heater tray by
at least two layers of electrical insulators rather than one layer
of insulation so that a "pin hole" in one layer would not
compromise the effectiveness of the insulation and compromise
patient safety.
[0117] Some aspects of the systems and methods described herein can
be implemented using, for example, computer software, hardware,
firmware, or any combination of computer software, hardware, and
firmware. Computer software can include computer executable code
stored in computer readable medium (e.g., non-transitory computer
readable medium) that, when executed, causes one or more computing
devices to perform the functions described herein. In some
embodiments, computer-executable code is executed by one or more
general purpose computers. It will be appreciated, in light of this
disclosure, that any feature or function that can be implemented
using software to be executed on one or more general purpose
computers can also be implemented using a different combination of
hardware, software, and/or firmware. For example, such a feature of
function can be implemented completely in hardware using a
combination of integrated circuits. Alternatively or additionally,
such a feature or function can be implemented completely or
partially using one or more specialized computers designed to
perform the particular functions described herein rather than by
general purpose computers.
[0118] Multiple distributed computing devices can be substituted
for any computing device described herein. In such distributed
embodiments, the functions of the one computing device are
distributed (e.g., over a network) such that some functions are
performed on each of the distributed computing devices.
[0119] Some features of this disclosure may be described with
reference to equations, algorithms, and/or flowcharts. These
methods may be implemented using computer program instructions
executable on one or more computing devices, using one or more
computer processors. These methods may also be implemented as
computer software either separately from, or as a component of, an
apparatus or system. In this regard, each equation, algorithm, or
block or step of a flowchart, and combinations thereof, may be
implemented by hardware, firmware, and/or software including
computer program instructions embodied in computer-readable medium.
As will be appreciated, any such computer program instructions may
be loaded onto one or more computers, including without limitation
a general purpose computer or special purpose computer, or other
programmable processing apparatus to produce a machine, such that
the computer program instructions which execute on the computer(s)
or other programmable processing device(s) implement the functions
specified in the equations, algorithms, and/or flowcharts. It will
also be understood that each equation, algorithm, and/or block in
flowchart illustrations, and combinations thereof, may be
implemented by special purpose hardware-based computer systems
which perform the specified functions or steps, or by combinations
of special purpose hardware and computer-readable program code
logic means.
[0120] Any features of the embodiments shown and/or described in
the figures that have not been expressly described in this text,
such as distances, proportions of components, etc. are also
intended to form part of this disclosure. Additionally, although
these inventions have been disclosed in the context of various
embodiments, features, aspects, and examples, it will be understood
by those skilled in the art that the present inventions extend
beyond the specifically disclosed embodiments to other alternative
embodiments and/or uses of the inventions and obvious modifications
and equivalents thereof. Accordingly, it should be understood that
various features and aspects of the disclosed embodiments can be
combined with, or substituted for, one another in order to perform
varying modes of the disclosed inventions. The present disclosure
describes various features, no single one of which is solely
responsible for the benefits described herein. It will be
understood that various features described herein may be combined,
modified, or omitted, as would be apparent to one of ordinary
skill. Other combinations and sub-combinations than those
specifically described herein will be apparent to one of ordinary
skill, and are intended to form a part of this disclosure. Various
methods are described herein in connection with various flowchart
blocks. It will be understood that in many cases, certain steps may
be combined together such that multiple steps shown in the
flowcharts can be performed as a single step. Also, certain steps
can be broken in to additional sub-steps to be performed
separately. In many instances, the order of the steps can be
rearranged and certain steps may be omitted entirely. Also, the
methods described herein are to be understood to be open-ended,
such that additional steps to those shown and described herein can
also be performed. Thus, it is intended that the scope of the
present inventions disclosed herein should not be limited by the
particular disclosed embodiments described herein.
* * * * *