U.S. patent application number 17/244684 was filed with the patent office on 2021-08-19 for dialysis system and methods.
The applicant listed for this patent is OUTSET MEDICAL, INC.. Invention is credited to Shih-Paul CHEN, James R. CURTIS, Michael Edward HOGARD, Dean HU, Gopi K. LINGAM, Steven M. MILLER, Peter Velasco OBICO, James RITSON.
Application Number | 20210252204 17/244684 |
Document ID | / |
Family ID | 1000005564769 |
Filed Date | 2021-08-19 |
United States Patent
Application |
20210252204 |
Kind Code |
A1 |
HOGARD; Michael Edward ; et
al. |
August 19, 2021 |
DIALYSIS SYSTEM AND METHODS
Abstract
Dialysis systems and methods are described which can include a
number of features. The dialysis systems described can be to
provide dialysis therapy to a patient in the comfort of their own
home. The dialysis system can be configured to prepare purified
water from a tap water source in real-time that is used for
creating a dialysate solution. The dialysis systems described also
include features that make it easy for a patient to self-administer
therapy. For example, the dialysis systems include disposable
cartridge and patient tubing sets that are easily installed on the
dialysis system and automatically align the tubing set, sensors,
venous drip chamber, and other features with the corresponding
components on the dialysis system. Methods of use are also
provided, including automated priming sequences, blood return
sequences, and dynamic balancing methods for controlling a rate of
fluid transfer during different types of dialysis, including
hemodialysis, ultrafiltration, and hemodiafiltration.
Inventors: |
HOGARD; Michael Edward;
(Odessa, FL) ; HU; Dean; (San Leandro, CA)
; CHEN; Shih-Paul; (Los Altos, CA) ; RITSON;
James; (San Jose, CA) ; LINGAM; Gopi K.; (San
Jose, CA) ; OBICO; Peter Velasco; (Santa Clara,
CA) ; CURTIS; James R.; (Portland, OR) ;
MILLER; Steven M.; (Palo Alto, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OUTSET MEDICAL, INC. |
San Jose |
CA |
US |
|
|
Family ID: |
1000005564769 |
Appl. No.: |
17/244684 |
Filed: |
April 29, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16550042 |
Aug 23, 2019 |
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17244684 |
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62722119 |
Aug 23, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 1/1621 20140204;
A61M 1/1696 20130101; A61M 2205/3331 20130101; A61M 1/1601
20140204; A61M 1/288 20140204; A61M 1/1656 20130101 |
International
Class: |
A61M 1/28 20060101
A61M001/28; A61M 1/16 20060101 A61M001/16 |
Claims
1. A method of priming a tubing set of a dialysis system,
comprising: removing the tubing set from a sterile shipping
receptacle; attaching the tubing set to the dialysis system;
priming the tubing set with a flow of fluid from the dialysis
system to remove air from the tubing set; and draining the fluid
from the tubing set into the shipping receptacle.
2. The method of claim 1, further comprising attaching the shipping
receptacle to the dialysis system.
3. The method of claim 2, wherein attaching the shipping receptacle
further comprises engaging attachment features of the shipping
receptacle with corresponding mechanical features on the dialysis
system.
4. The method of claim 3, wherein the mechanical features on the
dialysis system are angled with respect to another so as to impose
a curvature on one or more surfaces of the shipping receptacle to
enlarge an opening of the shipping receptacle.
5. The method of claim 1, further comprising draining the fluid
from the tubing set into the shipping receptacle through a junction
fitting that connects an arterial line of the tubing set to a
venous line of the tubing set.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of U.S. application Ser. No.
16/550,042, filed Aug. 23, 2019, which application claims the
benefit of U.S. Provisional Appln. No. 62/722,119, filed Aug. 23,
2018, titled "Dialysis System and Methods", incorporated herein by
reference in their entirety. This application is related to U.S.
Pat. No. 9,504,777, titled "Dialysis System and Methods", which is
incorporated herein by reference.
INCORPORATION BY REFERENCE
[0002] All publications and patent applications mentioned in this
specification are herein incorporated by reference to the same
extent as if each individual publication or patent application was
specifically and individually indicated to be incorporated by
reference.
FIELD
[0003] This disclosure generally relates to dialysis systems. More
specifically, this disclosure relates to dialysis systems that
include many features that reduce the need for technician
involvement in the preparation and administration of dialysis
treatment.
BACKGROUND
[0004] There are, at present, hundreds of thousands of patients in
the United States with end-stage renal disease. Most of those
require dialysis to survive. Many patients receive dialysis
treatment at a dialysis center, which can place a demanding,
restrictive and tiring schedule on a patient. Patients who receive
in-center dialysis typically must travel to the center at least
three times a week and sit in a chair for 3 to 4 hours each time
while toxins and excess fluids are filtered from their blood. After
the treatment, the patient must wait for the needle site to stop
bleeding and blood pressure to return to normal, which requires
even more time taken away from other, more fulfilling activities in
their daily lives. Moreover, in-center patients must follow an
uncompromising schedule as a typical center treats three to five
shifts of patients in the course of a day. As a result, many people
who dialyze three times a week complain of feeling exhausted for at
least a few hours after a session.
[0005] Many dialysis systems on the market require significant
input and attention from technicians prior to, during, and after
the dialysis therapy. Before therapy, the technicians are often
required to manually install patient blood tubing sets onto the
dialysis system, connect the tubing sets to the patient, and to the
dialyzer, and manually prime the tubing sets to remove air from the
tubing set before therapy. During therapy, the technicians are
typically required to monitor venous pressure and fluid levels, and
administer boluses of saline and/or heparin to the patient. After
therapy, the technicians are often required to return blood in the
tubing set to the patient and drain the dialysis system. The
inefficiencies of most dialysis systems and the need for
significant technician involvement in the process make it even more
difficult for patients to receive dialysis therapy away from large
treatment centers.
[0006] Given the demanding nature of in-center dialysis, many
patients have turned to home dialysis as an option. Home dialysis
provides the patient with scheduling flexibility as it permits the
patient to choose treatment times to fit other activities, such as
going to work or caring for a family member. Unfortunately, current
dialysis systems are generally unsuitable for use in a patient's
home. One reason for this is that current systems are too large and
bulky to fit within a typical home. Current dialysis systems are
also energy-inefficient in that they use large amounts of energy to
heat large amounts of water for proper use. Although some home
dialysis systems are available, they generally are difficult to set
up and use. As a result, most dialysis treatments for chronic
patients are performed at dialysis centers.
[0007] Hemodialysis is also performed in the acute hospital
setting, either for current dialysis patients who have been
hospitalized, or for patients suffering from acute kidney injury.
In these care settings, typically a hospital room, water of
sufficient purity to create dialysate is not readily available.
Therefore, hemodialysis machines in the acute setting rely on large
quantities of pre-mixed dialysate, which are typically provided in
large bags and are cumbersome for staff to handle. Alternatively,
hemodialysis machines may be connected to a portable RO (reverse
osmosis) machine, or other similar water purification device. This
introduces another independent piece of equipment that must be
managed, transported and disinfected.
SUMMARY
[0008] A method of priming a tubing set and a dialyzer of a
dialysis system is provided, comprising the steps of connecting an
arterial line of a tubing set to a venous line of the tubing set to
form a continuous loop in the tubing set, pumping air out of the
tubing set with an air pump, pulling a flow of fluid from a fluid
source into the tubing set with the air pump, operating a blood
pump of the dialysis system in a forward operating mode to flow
fluid from the fluid source into the tubing set in a first
direction, and operating the blood pump in a reverse operating mode
to flow fluid through the tubing set in a second direction opposite
to the first direction.
[0009] In some examples, the pulling step further comprises pulling
the fluid into the tubing set with the air pump until the fluid is
detected by a first level sensor in a venous drip chamber.
[0010] In one embodiment, operating the blood pump in the forward
operating mode further comprises operating the blood pump in a
forward operating mode to flow fluid from the fluid source into the
tubing set until the fluid is detected by a second level sensor in
the venous drip chamber.
[0011] In some examples the method can include, after the pulling
step, allowing a fluid level in the venous drip chamber to fall
below the first level sensor.
[0012] In one embodiment, operating the blood pump in the forward
operating mode further comprises operating the blood pump in a
forward operating mode to flow fluid from the fluid source into the
tubing set until the fluid is detected by the first level sensor in
the venous drip chamber.
[0013] In another example, the method can comprise pumping air out
of the tubing set with an air pump during the operating steps.
[0014] A dialysis system is also provided, comprising a fluid
source, a patient tubing set fluidly coupled to the fluid source,
the patient tubing set including a venous drip chamber, an air pump
coupled to the venous drip chamber, the air pump being configured
to pump air into or out of the venous drip chamber, a blood pump
coupled to the patient tubing set, the blood pump being configured
to flow fluid through the patient tubing set, at least one sensor
coupled to the venous drip chamber and being configured to monitor
a fluid level in the venous drip chamber, and an electronic
controller in communication with the at least one sensor, the blood
pump, and the air pump, the electronic controller being configured
to control the air pump to pump air out of the tubing set, control
the air pump to pull a flow of fluid from the fluid source into the
patient tubing set, control the blood pump in a forward direction
to flow fluid from the fluid source into the tubing set, and
control the blood pump in a reverse direction to flow fluid through
the tubing set.
[0015] A method of testing for leaks in a tubing set of a dialysis
system is provided, comprising pressurizing a first segment of the
tubing set, measuring a baseline pressure of the first segment
tubing set, exposing a second segment of the tubing set to the
pressurized first segment, measuring a pressure of the second
segment of the tubing set, and comparing the measured pressure of
the second segment to the baseline pressure of the tubing set to
identify a leak in the second segment.
[0016] In some embodiments, exposing the second segment further
comprises opening one or more pinch valves of the tubing set.
[0017] In one example, the method can include monitoring the
pressure of the second segment for a pressure decay rate that
exceeds a pressure decay threshold to identify a leak in the second
segment.
[0018] A method of priming a tubing set of a dialysis system is
provided, comprising removing the tubing set from a sterile
shipping receptacle, attaching the tubing set to the dialysis
system, priming the tubing set with a flow of fluid from the
dialysis system to remove air from the tubing set, and draining the
fluid from the tubing set into the shipping receptacle.
[0019] In some examples, the method further comprises attaching the
shipping receptacle to the dialysis system.
[0020] In one embodiment, attaching the shipping receptacle further
comprises engaging attachment features of the shipping receptacle
with corresponding mechanical features on the dialysis system.
[0021] In some examples, the mechanical features on the dialysis
system are angled with respect to another so as to impose a
curvature on one or more surfaces of the shipping receptacle to
enlarge an opening of the shipping receptacle.
[0022] In another embodiment, the method includes draining the
fluid from the tubing set into the shipping receptacle through a
junction fitting that connects an arterial line of the tubing set
to a venous line of the tubing set.
[0023] A method of improving durability and operation of one or
more displacement pumps is provided, comprising connecting one or
more displacement pumps to a pump burn-in fixture to form a
closed-loop fluidic path between the one or more displacement pumps
and the pump burn-in fixture, increasing a temperature and pressure
of fluid within the closed-loop fluidic path, operating the one or
more displacement pumps to flow the fluid through the closed-loop
fluidic path for a predetermined period of time to reduce surface
imperfections internal to the one or more displacement pumps.
[0024] In one embodiment, the increasing step further comprises
increasing the temperature and pressure of the fluid to levels that
are above what the one or more displacement pumps encounter during
normal operation.
[0025] In another embodiment, the method comprises increasing the
temperature of the fluid above 25 deg C.
[0026] In another embodiment, the method comprises increasing the
pressure of the fluid above 100 psi.
[0027] A pump burn-in fixture is provided, comprising a housing, a
fluid source, one or more connection ports in or on the housing,
one or more displacement pumps coupled to the one or more
connection ports so as to form a closed-loop fluidic path between
the fluid source, the one or more displacement pumps, and the one
or more connection ports, a heating element configured to heat a
fluid within the closed-loop fluidic path to an elevated
temperature above a normal operating temperature of the one or more
displacement pumps, and an electronic controller configured to
control operation of the one or more displacement pumps with the
elevated temperature fluid for a predetermined time to reduce
surface imperfections internal to the one or more displacement
pumps.
[0028] In some examples, a method of providing dialysis therapy to
a patient is provided, comprising combining a dialysate concentrate
and water with a dialysate system to produce a dialysate in
real-time, providing a first flow of the dialysate through the
dialysis system at a first dialysate flow rate, monitoring
consumption of the dialysate concentrate by the dialysis system,
determining if enough dialysate concentrate remains to complete the
dialysis therapy at the first dialysate flow rate, and if there is
not enough dialysate concentrate to complete the dialysis therapy
at the first dialysate flow rate providing a second flow of the
dialysate through the dialysis system at a second dialysate flow
rate that allows for completion of the dialysis therapy.
[0029] In one embodiment, the method includes, before providing the
second flow, calculating the second dialysate flow rate that allows
for completion of the dialysis therapy.
[0030] In some embodiments, the dialysis system houses a finite
supply of dialysate concentrate.
[0031] In one embodiment, the second dialysate flow rate is lower
than the first dialysate flow rate.
[0032] In one example, the first dialysis flow rate is
approximately 300 ml/min, and the second dialysis flow rate is
approximately 100 ml/min.
[0033] In another embodiment, the determining step further
comprises determining if enough dialysate concentrate remains based
on the first dialysate flow rate, an amount of dialysate
concentrate remaining, and a total treatment time.
[0034] In one example, the method further comprises maintaining a
pressure within the dialysis system when the second flow of
dialysate is provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] The novel features of the invention are set forth with
particularity in the claims that follow. A better understanding of
the features and advantages of the present invention will be
obtained by reference to the following detailed description that
sets forth illustrative embodiments, in which the principles of the
invention are utilized, and the accompanying drawings of which:
[0036] FIG. 1 shows one embodiment of a dialysis system.
[0037] FIG. 2 illustrates one embodiment of a water purification
system of the dialysis system.
[0038] FIG. 3 illustrates one embodiment of a dialysis delivery
system of the dialysis system.
[0039] FIG. 4 shows one example of a front panel of the dialysis
delivery system.
[0040] FIGS. 5 and 6 illustrate one embodiment of a cartridge
including a tubing set attached to an organizer.
[0041] FIG. 7 shows a flow diagram of the water purification system
contained within the dialysis system.
[0042] FIG. 8 is a schematic diagram showing a water supply
subsystem, a filtration subsystem, a pre-heating subsystem, an RO
filtration subsystem, and a pasteurization subsystem of the water
purification system of the dialysis system.
[0043] FIG. 9 shows the features of the water supply subsystem of
the water purification system.
[0044] FIG. 10 shows one embodiment of a filtration subsystem of
the water purification system.
[0045] FIG. 11 shows one embodiment of a pre-heating subsystem of
the water purification system.
[0046] FIG. 12 shows one embodiment of a RO filtration subsystem of
the water purification system.
[0047] FIG. 13 illustrates one embodiment of a pasteurization
subsystem of the water preparation system.
[0048] FIG. 14 illustrates a schematic of a mixing subsystem of the
dialysis delivery system.
[0049] FIG. 15 shows one embodiment of a mixing chamber.
[0050] FIG. 16 illustrates an ultrafiltration subsystem of the
dialysis delivery system which can receive the prepared dialysate
from the mixing subsystem.
[0051] FIG. 17 shows a schematic diagram illustrating the flow of
saline through tubing set during blood return to the user.
[0052] FIG. 18 shows one embodiment of a union joint adapted to
connect venous and arterial lines of a patient tubing set during a
priming sequence.
[0053] FIGS. 19A, 19B and 19C illustrate one embodiment of a
discard receptacle for discarding of priming saline following a
priming sequence.
[0054] FIG. 20 is a flowchart describing an example of a method for
conserving dialysate during therapy.
[0055] FIGS. 21, 22, 23, 24 and 25 show an example of a pump
burn-in system to prevent particulates from the pumps from entering
the dialysis system.
[0056] FIGS. 26 and 27 show embodiments of a receptacle for
discarding the priming fluid.
[0057] FIG. 28 is a schematic drawing of an ultrafiltration system
that can be implemented in place of the pasteurization subsystem of
FIG. 13.
[0058] FIGS. 29A, 29B, 29C, 29D, 29E, 29F, 29G, 29H, 29I, 29J, 29K
and 29L illustrate another sequence of priming a patient tubing set
prior to dialysis therapy.
[0059] FIG. 30 is a flowchart describing one method for
automatically controlling a fluid level within a venous drip
chamber during dialysis therapy.
DETAILED DESCRIPTION
[0060] This disclosure describes systems, devices, and methods
related to dialysis therapy, including a dialysis system that is
simple to use and includes automated features that eliminate or
reduce the need for technician involvement during dialysis therapy.
In some embodiments, the dialysis system can be a home dialysis
system. Embodiments of the dialysis system can include various
features that automate and improve the performance, efficiency, and
safety of dialysis therapy.
[0061] In some embodiments, a dialysis system is described that can
provide acute and chronic dialysis therapy to users. The system can
include a water purification system configured to prepare water for
use in dialysis therapy in real-time using available water sources,
and a dialysis delivery system configured to prepare the dialysate
for dialysis therapy. The dialysis system can include a disposable
cartridge and tubing set for connecting to the user during dialysis
therapy to retrieve and deliver blood from the user.
[0062] FIG. 1 illustrates one embodiment of a dialysis system 100
configured to provide dialysis treatment to a user in either a
clinical or non-clinical setting, such as the user's home. The
dialysis system 100 can comprise a water purification system 102
and a dialysis delivery system 104 disposed within a housing 106.
The water purification system 102 can be configured to purify a
water source in real-time for dialysis therapy. For example, the
water purification system can be connected to a residential water
source (e.g., tap water) and prepare pasteurized water in
real-time. The pasteurized water can then be used for dialysis
therapy (e.g., with the dialysis delivery system) without the need
to heat and cool large batched quantities of water typically
associated with water purification methodologies.
[0063] Dialysis system 100 can also include a cartridge 120 which
can be removably coupled to the housing 106 of the system. The
cartridge can include a patient tubing set attached to an
organizer, which will be described in more detail below. The
cartridge and tubing set, which can be sterile, disposable,
one-time use components, are configured to connect to the dialysis
system prior to therapy. This connection correctly aligns
corresponding components between the cartridge, tubing set, and
dialysis system prior to dialysis therapy. For example, the tubing
set is automatically associated with one or more pumps (e.g.,
peristaltic pumps), clamps and sensors for drawing and pumping the
user's blood through the tubing set when the cartridge is coupled
to the dialysis system. The tubing set can also be associated with
a saline source of the dialysis system for automated priming and
air removal prior to therapy. In some embodiments, the cartridge
and tubing set can be connected to a dialyzer 126 of the dialysis
system. In other embodiments, the cartridge and tubing set can
include a built-in dialyzer that is pre-attached to the tubing set.
A user or patient can interact with the dialysis system via a user
interface 113 including a display.
[0064] FIGS. 2 and 3 illustrate the water purification system 102
and the dialysis delivery system 104, respectively, of one
embodiment of the dialysis system 100. The two systems are
illustrated and described separately for ease of explanation, but
it should be understood that both systems can be included in a
single housing 106 of the dialysis system. FIG. 2 illustrates one
embodiment of the water purification system 102 contained within
housing 106 that can include a front door 105 (shown in the open
position). The front door 105 can provide access to features
associated with the water purification system such as one or more
filters, including sediment filter(s) 108, carbon filter(s) 110,
and reverse osmosis (RO) filter(s) 112. The filters can be
configured to assist in purifying water from a water source (such
as tap water) in fluid communication with the water purification
system 102. The water purification system can further include
heating and cooling elements, including heat exchangers, configured
to pasteurize and control fluid temperatures in the system, as will
be described in more detail below. The system can optionally
include a chlorine sample port 195 to provide samples of the fluid
for measuring chlorine content.
[0065] In FIG. 3, the dialysis delivery system 104 contained within
housing 106 can include an upper lid 109 and front door 111, both
shown in the open position. The upper lid 109 can open to allow
access to various features of the dialysis system, such as user
interface 113 (e.g., a computing device including an electronic
controller and a display such as a touch screen) and dialysate
containers 117. Front door 111 can open and close to allow access
to front panel 210, which can include a variety of features
configured to interact with cartridge 120 and its associated tubing
set, including alignment and attachment features configured to
couple the cartridge 120 to the dialysis system 100. Dialyzer 126
can be mounted in front door 111 or on the front panel, and can
include lines or ports connecting the dialyzer to the prepared
dialysate as well as to the tubing set of the cartridge.
[0066] In some embodiments, the dialysis system 100 can also
include a blood pressure cuff to provide for real-time monitoring
of user blood pressure. The system (i.e., the electronic controller
of the system) can be configured to monitor the blood pressure of
the user during dialysis therapy. If the blood pressure of the user
drops below a threshold value (e.g., a blood pressure threshold
that indicates the user is hypotonic), the system can alert the
user with a low blood pressure alarm and the dialysis therapy can
be stopped. In the event that the user ignores a configurable
number of low blood pressure alarms from the system, the system can
be configured to automatically stop the dialysis therapy, at which
point the system can inform the user that return of the user's
blood (the blood that remains in the tubing set and dialyzer) back
to the user's body is necessary. For example, the system can be
pre-programmed to automatically stop therapy if the user ignores
three low blood pressure alarms. In other embodiments, the system
can give the user a bolus of saline to bring user fluid levels back
up before resuming dialysis therapy. The amount of saline delivered
to the patient can be tracked and accounted for during
ultrafiltration fluid removal.
[0067] The dialysis delivery system 104 of FIG. 3 can be configured
to automatically prepare dialysate fluid with purified water
supplied by the water purification system 102 of FIG. 2.
Furthermore, the dialysis delivery system can de-aerate the
purified water, and proportion and mix in acid and bicarbonate
concentrates from dialysate containers 117. The resulting dialysate
fluid can be passed through one or more ultrafilters (described
below) to ensure the dialysate fluid meets certain regulatory
limits for microbial and endotoxin contaminants.
[0068] Dialysis can be performed in the dialysis delivery system
104 of the dialysis system 100 by passing a user's blood and
dialysate through dialyzer 126. The dialysis system 100 can include
an electronic controller configured to manage various flow control
devices and features for regulating the flow of dialysate and blood
to and from the dialyzer in order to achieve different types of
dialysis, including hemodialysis, ultrafiltration, and
hemodiafiltration.
[0069] FIG. 4 shows one example of front panel 210 of the dialysis
delivery system 104 of FIG. 3, which can include a number of
features that assist with positioning and attaching cartridge 120
and its associated tubing set to the dialysis system 100, and for
monitoring and controlling fluid flow along the tubing set of the
cartridge. During installation of a new sterile cartridge onto the
dialysis system, alignment features on the cartridge (e.g., holes
125 through the cartridge, shown in FIG. 5) can be lined up with
locator pegs 260. The locator pegs also serve to align the
cartridge and the tubing set with features on the front panel used
for dialysis treatment, including blood pump 213 and spring wire
22, positioning features 212, venous and arterial pressure
sensor(s) 182a and 182b, venous air sensor 2161, arterial air
sensor 216, pinch valve(s) 180a-d, and venous drip chamber holder
179. Blood pump 213 can be a peristaltic pump, for example. A
holder or slot 215 for an infusion pump or syringe is also
shown.
[0070] The cartridge can be pressed into place on the front panel
using these locator pegs 260 to ensure that all the features of the
cartridge and tubing set line up and are installed properly with
the corresponding features of the front panel 210. In some
embodiments, the cartridge can be easily installed with a single
hand, and closing the door of the system can seat the cartridge
onto the system. As shown in FIG. 1, the dialysis system can
include wheels for ease of transport. In one specific embodiment, a
force applied to seat the cartridge horizontally onto the front
panel 210 by closing the door with a downward rotating motion of a
lever on the door does not tend to move the dialysis system 100 on
its wheels.
[0071] The pinch valves can be used for a number of functions
before, during, and after dialysis therapy. The pinch valves 180a-d
can be controlled by the electronic controller of the dialysis
delivery system. Pinch valves 180a and 180b can be configured to
control the flow of saline from a saline source (such as a saline
bag) to the tubing set. In some embodiments, the pinch valves can
be opened and the blood pump 213 can be operated to draw saline
into the tubing set to remove air during a priming sequence, to
flush impurities from the dialyzer before treatment, and to
displace blood back to the user at the end of a treatment. The
pinch valves 180a and 180b can also be used to deliver therapeutic
boluses of saline to the user during therapy to maintain blood
pressure or adjust electrolytes or fluid levels of the patient. In
other embodiments, pumps such as peristaltic pumps may be
configured to deliver therapeutic boluses of saline to the
user.
[0072] Pinch valves 180c and 180d can be configured to close the
arterial and venous lines of the tubing set that connect to the
user. They can also be opened and closed multiple times before,
during, and after treatment to facilitate actions such as tubing
set pre-conditioning tubing to achieve proper compliance, priming,
discarding of priming saline, blood return to the patient, and/or
draining the dialyzer after treatment. In one embodiment, the
system can incorporate information from venous air sensor 2161,
arterial air sensor 216, or other air sensors in the system to
close pinch valves 180c and 180d in the event that air bubbles are
found in the lines, particularly in the venous line. In a further
embodiment, the system can be configured to remove the detected air
bubble(s) by reversing the operation of the blood pump to attempt
to clear the air bubble(s) through the venous drip chamber.
[0073] Pinch valves 180a-d can also be actuated to perform a series
of self-tests on the tubing set prior to each treatment. The tubing
set can be pressurized with the blood pump, and the pressure can be
held in the tubing set by closing the pinch valves. The arterial
and venous pressure sensors can then be used to look for pressure
decay in the tubing set.
[0074] FIG. 4 also illustrates venous drip chamber holder 179,
which can include a pair of venous level sensors 181a and 181b.
When the cartridge is coupled to the dialysis delivery system, the
venous drip chamber (described in more detail below) can engage the
venous drip chamber holder 179. During dialysis therapy, the venous
level sensors 181a and 181b can monitor the fluid level in the
venous drip chamber. If the fluid level rises above sensor 181a,
then the dialysis delivery system can automatically pump air into
the venous drip chamber to lower the fluid level. Alternatively, if
the fluid level dips below sensor 181b, then the dialysis delivery
system can automatically pump air out of the venous drip chamber
(or alternatively, vent air out of the chamber) to raise the fluid
level. Automatic level control reduces labor, as periodic
adjustments to the level can be made by the machine instead of by
clinic staff or the patient.
[0075] In other embodiments, the system may comprise algorithmic
features to protect itself from the failure of one or more of the
venous level sensors 181a or 181b and still allow automatic level
control. During treatment, the venous drip chamber 361 will be
filled with blood. Detecting blood level in a drip chamber can be
hindered by the tendency of blood to clot. These conditions can
cause venous level sensors to not accurately sense the true level
of the blood, causing the system to raise or lower the level
incorrectly. This could lead to the fluid level to drop
excessively, resulting in the air detector creating an alarm, or
for the fluid level to raise excessively, which can cause blood to
enter line 363 and foul venous transducer protector 371, hindering
pressure readings.
[0076] In these embodiments, algorithmically improved automatic
level control within the venous drip chamber can be maintained
under the adverse conditions of clots and foam. The algorithmically
improved automatic level control may utilize the ideal gas law to
determine a set amount ("air budget") of air for air pump 250 to
either inject or remove to lower or raise the level, based on
pressure detected within the chamber by venous pressure sensor
182a. This is possible because the geometric gas volumes of drip
chamber and tubing connections are known. At high pressure, air is
volumetrically compressed, and therefore the linear distance that a
level within a substantially straight-walled chamber is raised or
lowered will be smaller, for a given amount of air injected or
removed. If the lower level sensor 181b detects air (or a clot
forms that is sensed as air), the algorithm will begin raising the
level. For a given venous pressure, the pump removes air up until
the budget of air has been reached. The budget is determined to
place the fluid level between the two level sensors, and is
dynamically calculated using the ideal gas law as described above.
In the event that the system is actually detecting air as opposed
to a clot, the fluid rises and as a result the lower level 181b
sensor will again detect fluid. At this point the algorithm resets
the air budget available to be used the next time lower level
sensor 181b detects air. If, however, lower level sensor 181b
incorrectly detects air because it is confounded by a clot or other
phenomena, it will still not detect air after the air pump removes
air and raises the level. At this point, the algorithm begins
controlling the level dynamically based on the pressure in the drip
chamber. If the pressure increases, the gas space above the fluid
compresses, causing the fluid level to rise. Conversely, if the
pressure decreases, the gas space above the fluid expands, causing
the fluid level to drop. A pressure increase or decrease will be
detected by venous pressure sensor 182a. If a pressure change of
sufficient magnitude is detected, the control algorithm uses the
pressure/volume relationship of the ideal gas law and calculates an
amount of air to add or remove using the air pump 250 to counteract
the rise or drop in level. In some embodiments, the pressure change
threshold is 20 mmHg. In some embodiments, the pressure change
threshold is 50 mmHg. In some embodiments, the pressure change
threshold is 100 mmHg. The amount of air to be removed or injected
is calculated dynamically using the both the magnitude and change
in venous pressure. In further embodiments, if pressure in the
chamber is not changed, and the upper level sensor 181a senses
fluid, the control algorithm will cause air pump 250 to inject a
calculated budget of air into the chamber to drive the level
down.
[0077] FIG. 30 illustrates a flowchart 3000 that describes the
automatic level control process described above. At step 3002 of
flowchart 3000, the dialysis system can automatically control the
fluid level in the venous drip chamber during therapy as described
above (e.g., but measuring the fluid level with a low level sensor
and a high level sensor in the venous drip chamber and
automatically raising or lowering the fluid level based on the
sensed fluid level). During the dialysis therapy, at step 3004, if
the lower level sensor detects air (instead of fluid), then at step
3006 the dialysis system can determine an "air budget" of air for
the air pump of the system to either inject or remove from the
venous drip chamber. This "air budget" can be based on a measured
pressure within the venous drip chamber and is dynamically
calculated so as to place the fluid level between the upper level
sensor and the lower level sensor. In some embodiments, the
pressure within the venous drip chamber is measured with a venous
pressure sensor of the dialysis system. Next, at step 3008, the
dialysis system can raise the fluid level by removing a volume air
from the venous drip chamber with air pump that is equal to the
calculated "air budget". After the volume of air has been removed
from the venous drip chamber, if at step 3010 the lower level
sensor detects fluid, then the "air budget" can be reset at step
3012.
[0078] Referring to step 3010 again, in some instances the lower
level sensor will still detect air, even after removing the
budgeted air in step 3008. This could be caused, for example, by a
clot or other phenomena in the venous drip chamber. In this event,
at step 3014, a fault is detected and the dialysis system can
switch to controlling the fluid level in the venous drip chamber
based on measured pressure. At step 3016, the system will
continuously measure the pressure within the venous drip chamber.
If a pressure change above a pressure threshold is detected (e.g.,
a pressure change greater than 20-50 mmHg) then at steps 3018/3022,
the system can determine an "air budget" based on the pressure
change and pressure magnitude. At step 3020, the fluid level can be
lowered by adding the budgeted air, and at step 3024, the fluid
level can be raised by adding the budgeted air.
[0079] In other embodiments, the system may comprise a single
analog or non-binary digital level sensor in the place of the two
venous level sensors to detect the actual level within the drip
chamber. The dialysis delivery system can then be configured to
perform analogous adjustments as described above based on the level
detected by this single sensor. The single sensor can comprise, for
example, an ultrasonic, optical, or capacitive level sensor.
[0080] Still referring to FIG. 4, in one embodiment, attaching the
cartridge onto the front panel 210 properly will engage cartridge
presence detector 214, which can be a switch or a sensor configured
to communicate to the dialysis system (e.g., to a controller of the
system) that a cartridge is installed on the front panel. As a
safety precaution, the system will not allow pinch valves 180a-d to
be closed until the cartridge presence detector 214 indicates that
the cartridge is installed properly. The presence detector can also
initiate automatic loading of a blood pump portion of the tubing
set into the blood pump. In one embodiment, the blood pump can
include a spring wire 22 that is actuated to grasp and pull the
blood pump portion of the tubing set into the blood pump when the
presence detector 214 is depressed. Furthermore, the connection of
the cartridge and tubing set to the front panel can also initiate a
self-check in each portion of the tubing set to identify any leaks
in the tubing.
[0081] FIGS. 5 and 6 illustrate one embodiment of a cartridge 120
including tubing set 122 attached to an organizer 124. Although the
majority of the tubing set 122 is blocked from view in FIG. 5 by
the organizer, arterial line 230, venous line 232, saline line 233,
and infusion line 234 can be seen. Referring to FIG. 5, a user can
ensure proper placement of the cartridge relative to the front
panel with organizer 124 by aligning holes 125 of the organizer
with the locator pegs 260 of the front panel. FIG. 5 shows a
plurality of aligning holes 125 near the top of the organizer, but
it should be understood that any number and location of aligning
holes and locator pegs can be used to align and mount the cartridge
120. In addition, the organizer 124 can ensure proper placement of
the tubing set 122 relative to one or more features of the dialysis
system, including valves (such as pinch valves 180a-d described
above), sensors (such as pressure and air sensors) the blood pump,
the venous drip chamber, etc. Also shown in FIG. 5, the cartridge
can include a number of access holes 2165 for gaining access to
features on the dialysis delivery system, such as gaining access to
pinch valves or the blood pump when the cartridge is installed on
the system.
[0082] FIG. 6 shows the back side of the cartridge 120 and
organizer 124 which is configured to interface with the front panel
210 of the dialysis delivery system, including the tubing set 122.
The tubing set 122 of the cartridge 120 can include an arterial
line 230, a venous line 232, and a blood pump portion 2167
configured to interface with the blood pump 213 on the front panel
210. The blood pump 213 can be configured to draw blood from a user
through arterial line 230, pass the blood through a dialyzer, and
return the treated blood to the patient through venous line 232.
The tubing set 122 can also be connected to venous drip chamber 361
for the removal of air from the lines during therapy and priming. A
continuous pathway through which blood can circulate and dialyze
can be created by connecting one end of the arterial line 230 and
one end of the venous line 232 of the tubing set 122 to the user's
blood vessels, such as via an access point (e.g., fistula needles
or catheter). Opposite ends of the arterial and venous lines can be
attached to the dialyzer (described below), such as via color coded
connectors (e.g., red for arterial and blue for venous).
[0083] The tubing set can further include saline connections 353a
and 353b to a saline solution, such as a saline bag, via a saline
line 233. As shown in FIG. 6, saline connection 353a can connect to
the tubing set proximal to the blood pump portion of the tubing
set. Tubing set 353b can exit the cartridge and connect to the
tubing set on arterial line 230 near where the arterial line is
connected to the user. Connecting the saline connection 353b near
the arterial connection to the user improves blood return after a
dialysis treatment since all the blood in the arterial line can be
flushed back into the user. The tubing set can also include a
connection to an infusion pump or syringe via the infusion line
234. The infusion pump and infusion line can connect to the tubing
set at a non-pulsatile location, such as at the top of the venous
drip chamber, to prevent back-streaming of blood up into the
heparin line. In some embodiments, the infusion pump is integral to
the system. In other embodiments, the infusion pump is separate
from the system. The connection at the top of the venous drip
chamber can be a non-pulsatile location due to the air gap created
between the heparin line and fluid in the venous drip chamber.
[0084] Flow of fluid, such as blood, through the tubing set 122
will now be described. As described above, the blood pump that
interacts with blood pump portion 2167 of tubing set 122 can be a
peristaltic pump. The blood pump can operate in two modes of
operation. One mode of operation can be a "forward" operating mode
of the blood pump that can be used during dialysis therapy to move
blood from the patient into the tubing set and back to the patient.
Another mode of operation can be a "reverse" operating mode of the
blood pump that can be used during a priming sequence to move
saline through the tubing set. Fluid flows through the tubing set
in the "forward" operating mode in a direction opposite to fluid
flowing through the tubing set in the "reverse" operating mode.
During dialysis therapy, blood can be drawn from the patient into
the tubing set 122 through arterial line 230, due to the blood pump
213 interacting with the tubing set in the "forward" operating
mode. Arterial pressure pod 355 can mate with a pressure sensor
(arterial pressure sensor 182b of FIG. 4) or transducer on the
front panel of the dialysis delivery system to measure the pressure
on the arterial line during therapy. The arterial pressure pod 355
comprises a diaphragm that allows for pressure to be transmitted
without the transmission of blood into the system. The blood can
continue through the tubing set, past saline connection 353a and
through the blood pump portion of the tubing set, and through
tubing portion 357 towards the dialyzer. Once the blood has
traveled through the dialyzer, it can continue in the tubing set
122 through tubing portion 359 back into the cartridge, where it
enters venous drip chamber 361 at the bottom of the drip chamber at
entry port 365. Blood flows into the venous drip chamber 361, where
air is separated from the blood into the venous drip chamber and
removed from the system (e.g., such as from a vent or port at the
top of the drip chamber). The venous drip chamber can be connected
to a venous pressure sensor or transducer on the dialysis delivery
system via line 363 and venous transducer protector 371, which
prevents blood or other fluids from contaminating the pressure
sensor. Blood that has entered the venous drip chamber can then
exit the chamber via exit port 367 and continue to flow through the
tubing set until it is returned to the patient through venous line
232.
[0085] As shown in FIG. 6, the venous drip chamber includes entry
and exit ports 365 and 367 that allows blood to enter and exit the
venous drip chamber from the bottom of the venous drip chamber. Any
air bubbles caught in the line or the blood percolate into the
chamber and are removed from the blood before it is returned to the
patient. This configuration allows for fluid flow through the
tubing set to be reversed during priming of the dialyzer to push
air up and out of the dialyzer. It also allows for the flow of
blood to be reversed in the tubing set in the event that air is
detected in the venous line of the tubing set.
[0086] Priming and Prime Discard
[0087] Before treatment, the tubing set can be primed with saline
to remove air from the line and prepare the system for dialysis
therapy. During a priming sequence, the arterial and venous lines
of the tubing set can be connected together to form a continuous
loop in the tubing set. FIG. 18 shows one embodiment of a union
joint 256 configured to attach arterial line 230 to venous line
232. In some embodiments, the union joint 256 may be shaped like a
"T" or "Y" or other configuration that has at least three connected
tubing paths: 1) the arterial line, 2) the venous line, and 3) a
conduit for priming fluid to exit the tubing set. This third tubing
path may be selectively opened or closed, i.e., with an external
cap 258. This junction fitting will be the only exposed open
surface during the prime discard procedure, which provides improved
infection control over having two exposed patient connection
points.
[0088] During a priming sequence to remove air from the tubing set
and prepare the system for therapy, saline can be drawn into the
tubing set through saline connections 353a and/or 353b by
activating the blood pump in the "forward" and "reverse" operating
modes to cause the blood pump to interact with the tubing set and
move saline into the tubing set from the saline source. When the
pump operates in this "reverse" operating mode, the saline moves
from the saline source into the tubing set and the blood-side of
the dialyzer to fill the tubing set and the dialyzer with fluid and
remove air from the tubing set via the venous drip chamber. In this
"reverse" operating mode, saline flows through the tubing set in
the opposite direction of blood flow during dialysis therapy. Thus,
the saline flows through the venous drip chamber before flowing
through the blood-side of the dialyzer. Air in the venous drip
chamber can be monitored with the venous level sensors. Any air in
the system can be pushed by the saline into the venous drip
chamber.
[0089] When the venous level sensors no longer detect any changes
to the fluid level in the venous drip chamber, or when air sensors
no longer detect air circulating through the tubing set, then the
tubing set is primed and ready for treatment. The blood pump can
then be operated in the "forward" operating mode to move the saline
in the other direction than described above and out of the tubing
set. In the "forward" operating mode, the saline travels through
the blood-side of the dialyzer before passing through the venous
drip chamber and into the patient through venous line 232. In some
embodiments, the saline used during the priming sequence is
delivered into the patient at the start of dialysis therapy. The
amount of saline delivered is tracked and accounted for during
dialysis therapy depending on the patient's individual fluid
removal requirements. In another embodiment, some or all of the
saline is pumped or drained out of the tubing set prior to
therapy.
[0090] To complete the priming sequence, dialysate can be pumped or
moved through the dialysate-side of the dialyzer with a dialysate
pump (described below). The dialysate is pumped through the
dialysate-side of the dialyzer in the same direction that saline is
pumped through the blood-side of the dialyzer. The direction of the
saline and dialysate through the dialyzer can be in the direction
of bottom to top through the dialyzer, which allows the bubbles to
naturally purge through the top of the dialyzer. Thus, the priming
sequence of the present disclosure can remove air from both the
blood-side and dialysate-sides of the dialyzer without physically
manipulating or "flipping" an orientation of the dialyzer, as is
required by other conventional systems, since the priming sequence
moves fluid through both sides of the dialyzer in the same
direction.
[0091] During therapy, blood in the tubing set normally passes
through the blood-side of the dialyzer in the top down direction.
However, during priming, the blood pump can be operated in the
"reverse" direction to push saline through the dialyzer in the
bottom to top direction to more effectively remove air from the
dialyzer. The unique configuration of the tubing set and venous
drip chamber allows for the flow of saline in the "reverse"
direction through the tubing set because fluid both enters and
exits the venous drip chamber at connections on the bottom of the
venous drip chamber. Conventional venous drip chambers, in which
tubing connections are made at the top and bottom of the venous
drip chamber, only allow for fluid flow through the venous drip
chamber in one direction. The unique configuration of this
disclosure allows for priming of both the blood and dialysate sides
of the dialyzer without having to physically flip the dialyzer. Any
air generated in the venous drip chamber during priming can be
removed by either venting out of the system, or pumping out of the
system. In one embodiment, the pinch valves of the system can be
periodically actuated to open and close the saline lines of the
tubing set depending on the timing of the priming sequence to
"bang" bubbles loose in the dialyzer. For example, the pinch valves
can be opened and closed every 4-8 seconds to create a pulsing
effect of the saline in the lines.
[0092] FIGS. 29A-29L illustrate another sequence of priming a
patient tubing set prior to dialysis therapy. As shown in FIG. 29A,
the patient tubing set and dialysis system 2900 can include a blood
pump 2902, a dialyzer 2904, a venous drip chamber 2906, an arterial
line 2908, a venous line 2910, and a saline source 2912. The tubing
set can further include an arterial pressure sensor 2914 configured
to sense a pressure in the arterial line, and one or more level
sensors 2916 and 2918 coupled to the venous drip chamber. The one
or more level sensors can be configured to detect fluid within the
venous drip chamber during priming and during dialysis therapy. In
the illustrated embodiment, two level sensors are shown, but it
should be understood that one, or more than two, sensor(s) can be
implemented to achieve the same or similar functionality described
herein. The system can further include a plurality of valves, such
as pinch valves, including first and second saline pinch valves
2920 and 2922, arterial pinch valve 2924, and venous pinch valve
2926, which can be actuated by an electronic controller (not shown
but described herein) to change and adapt flow paths of fluid
within the tubing set. Finally, the patient tubing set and dialysis
system can include an air pump 2928 and a pressure sensor 2930,
both of which are disposed upstream of the venous drip chamber.
[0093] FIG. 29B illustrates the initial conditions of the tubing
set and dialysis system prior to beginning a priming sequence. In
FIG. 29, first and second saline pinch valves 2920 and 2922 can be
closed, and arterial pinch valve 2924 and venous pinch valve 2926
can be opened. Also, connector 2932 can be used to connect the
arterial line with the venous line to create a closed-loop flow
path in the patient tubing set. In this initial state, the blood
pump 2902 can turned off, and the air pump 2928 can be operated to
begin to pull air out of the tubing set. Since the first and second
saline pinch valves are closed at this step, the patient tubing set
forms a closed-loop and the air pump can begin to form a vacuum in
the tubing set.
[0094] Next, as shown in FIG. 29C, the first saline pinch valve
2920 can be opened while the air pump 2928 continues to operate,
which pulls saline into the patient tubing set from the saline
source. This step can be performed for a predetermined time period.
For example, the air pump can be used to pull saline into the
tubing set for 2-20 seconds. In the illustrated example, the saline
level rises to the arterial pressure sensor during this step.
[0095] Next, as shown in FIG. 29D, the first saline pinch valve
2920 can be closed, the second saline pinch valve 2922 can be
opened, and the air pump 2928 can continue to pull saline into the
tubing set. This operation can be continued until the fluid level
in the tubing set reaches a predetermined level. In one example,
the air pump can pull saline into the tubing set until the saline
or fluid level is detected in the venous drip chamber by one or
more level sensors. In the illustrated embodiment, this operation
ceases when fluid is detected by the lower level sensor 2916.
However, it should be understood that this operation could continue
until detection by the upper level sensor 2918. In embodiments with
a single level sensor, the operation can cease when the fluid is
detected by that single sensor.
[0096] Referring now to FIG. 29E, the first and second saline pinch
valves can both be closed, and the blood pump 2902 can be operated
in a "forward" direction (e.g., the same direction as during
dialysis therapy) while the air pump 2928 continues to operate.
This causes the fluid level to go down in the venous drip chamber,
as indicted by arrow 2901. Next, as shown in FIG. 29F, the first
saline pinch valve 2920 can be opened and the venous pinch valve
2926 can be closed, while the blood pump and air pump continue to
operate, to cause the fluid level to rise again in the patient
tubing set. This operation can continue until one or more of the
level sensors detects fluid in the venous drip chamber. In the
illustrated example, this operation continues until the upper level
sensor 2918 detects fluid in the venous drip chamber. At FIG. 29G,
the blood pump and air pump can continue to operate as in FIG. 29F,
but the patient tubing set can be vented through vent 2930. This
allows air bubbles to percolate out of the patient tubing set
through the venous drip chamber.
[0097] Next, as shown in FIG. 29H, the blood pump 2902 can be
operated in a "reverse" direction (e.g., the opposite direction as
during dialysis therapy) while the air pump 2928 continues to
operate. This continues the process of priming the tubing set and
filling every aspect of the tubing set with saline while removing
and dislodging air bubbles from the tubing set.
[0098] FIGS. 29I-29L illustrate one embodiment that includes
pressure testing individual segments of the patient tubing set
after the priming sequence to identify localized leaks in the
patient tubing set. The pressure testing sequence can include the
steps of sequentially opening and closing various pinch valves and
changing the operation of the blood pump to evaluate different
segments of the patient tubing set. For example, in FIG. 29I, all
pinch valves can be closed, and the blood pump can continue to
operate in the "forward" operating mode. This pressurizes the
segment of the patient tubing set between the blood pump 2902 and
the venous pinch valve 2926. Once the patient tubing set segment
has been pressurized, the pressure within the patient tubing set
segment can be measured and stored as a baseline pressurized value.
Next referring to FIG. 29J, the blood pump 2902 can be turned off
and the arterial pinch valve 2924 can be opened. Opening the
arterial pinch valve 2924 exposes a new segment of the patient
tubing set, between the blood pump and the venous pinch valve 2926,
to the pressurized fluid from the first tubing set segment. The
pressure within the patient tubing set can be measured again, and
compared against the baseline pressurized value and have a pressure
decay rate calculated. If the measured pressure at this step is
lower than the baseline pressurized value, or exhibits a pressure
decay rate above a certain threshold, it can indicate a leak in the
patient tubing set between the blood pump and the venous pinch
valve, including through saline pinch valve 2922. In FIG. 29K, the
blood pump can be turned off and venous pinch valve 2926 can be
opened. Opening the venous pinch valve 2926 exposes a new segment
of the patient tubing set, between the venous pinch valve and the
arterial pinch valve, to the pressurized fluid from the first
tubing set segment. The pressure within this patient tubing set
segment can be measured again, and compared against the baseline
pressurized value or have a pressure decay rate calculated. If the
measured pressure at this step is lower than the baseline
pressurized value or exhibits a pressure decay rate above a certain
threshold, it can indicate a leak in the patient tubing set between
the venous pinch valve and the arterial pinch valve, including
through saline pinch valve 2920. Finally, in FIG. 29L, the arterial
pinch valve can be opened and the blood pump can be operated again.
The measured pressure at this step can be compared to the baseline
pressure, or be determined to exhibit a pressure decay rate above a
certain threshold, to indicate a leak through saline pinch valve
2922.
[0099] After a priming sequence when saline is in the tubing set,
the system can further run self-tests to check for leaks in the
tubing set. In one embodiment, the pinch valve on the venous line
can be closed with the blood pump running, and air can be pumped
into the venous drip chamber. Next, the arterial pinch valve can be
closed, and the venous pinch valve can be opened, and the system
can check for pressure stabilization. If there is no pressure
decay, it can be confirmed that there are no leaks in the
system.
[0100] In one embodiment, the dialyzer can be flushed prior to
beginning dialysis therapy with a patient. The system can be
configured to flush the dialyzer with up to 500 ml of saline. Upon
completion of the priming procedure, the used priming fluid may be
discarded. Typically there have been two different types of
destinations for the used priming fluid: 1) a receptacle or fluidic
connection that leads to the inside the dialysis machine itself,
which routes to a drain, or 2) an external receptacle, which is
typically reusable and manually dumped into a sink and cleaned.
Both of these approaches present challenges in terms of maintaining
cleanliness and disinfection of surfaces, either internal or
external. Additionally, often times the open end(s) of the tubing
set that are used to interface with the disposal receptacle are the
same ends which will later be connected to the patient during
treatment. Infection control is of critical importance while
performing hemodialysis treatments and setups, and exposing the
open ends of the tubing set during the prime discard procedure
presents an infection risk, especially since the tubing set must be
handled by a user to position it correctly for discarding the
fluid.
[0101] As described above, the tubing set is filled with saline
during the priming sequence. During this priming, the arterial and
venous lines are attached to each other with union joint 256 as
illustrated in FIG. 18. In a first prime discard embodiment, after
the tubing set is primed, the patient can remove cap 258 from the
union joint 256 and position the union joint over a waste bucket.
The dialysis system can then be placed into a prime discard
sequence, which first confirms that valves 180b and 180c (from FIG.
17) are closed, and that valves 180a and 180d (from FIG. 17) are
open. The blood pump can be operated in a forward direction to draw
saline into the tubing set until the desired prime discard amount
is pumped through the system and drained though the union joint 256
of FIG. 18. Next, valve 180d is closed, valve 180C is opened, and
the saline is allowed to be gravity drained through the union joint
until the proper amount of saline feeds out of the union joint
(e.g., 40 ml of saline in one embodiment).
[0102] In another prime discard embodiment, the sterile packaging
for the cartridge and tubing set can also be used as a discard
receptacle after priming. The cartridge and tubing set is supplied
sterile, and is typically packaged in a disposable pouch which
serves as a sterile barrier. In a first configuration, shown in
FIG. 19A, a sterile receptacle 1900 is used as the sterile
packaging to ship and maintain sterility of the cartridge and
tubing set prior to treatment. In a second configuration, shown in
FIG. 19B, the sterile receptacle 1900 serves as a disposable prime
discard receptacle for drainage of priming saline. In operation, a
user removes the cartridge and tubing set from the sterile pouch,
which will later serve as the prime discard receptacle. The
cartridge and tubing set can be connected the dialysis machine,
including to a saline source and dialyzer, as described above. The
arterial and venous lines of the cartridge and tubing set can be
pre-connected to the union joint, and the cartridge and tubing set
are primed with saline, as described above. After priming the
tubing set, the user can attach the sterile receptacle to the
dialysis system, remove the cap from the union joint, and allow the
dialysis system to displace saline from the tubing set into the
sterile receptacle 1900. Saline is allowed to flow through both the
arterial and venous lines into the receptacle since they both meet
at the union joint. After the prime discard is completed, the user
removes the sterile receptacle and for disposal. Finally, the user
disconnects the union joint from the arterial/venous lines,
connects the lines to the patient's access site(s), and disposes of
the union joint. At this point, dialysis treatment is ready to
begin.
[0103] The sterile receptacle 1900 can include mounting features
1902, shown in FIG. 19B, such as cutouts, tabs, or other mounting
features to interface with the dialysis system to hold the
receptacle in place during prime discard. For example, in one
embodiment the mounting features 1902 comprise cutouts, and the
dialysis system comprises tabs that extend through the cutouts to
hold the receptacle on the dialysis system.
[0104] Additionally, the dialysis system can include mounting
features to hold the union joint in place on the dialysis system
relative to the mounted receptacle. The mounting features on the
dialysis system may include snap fit features, spring grip
features, semicircular cup features, hole and shaft features, or
any other similar mounting features. For example, the receptacle
may include linear slits cut into one of the sheets which interface
with linear extrusions which are hook-shaped in cross section
located on the dialysis system. In one specific example, these
hook-shaped features may be mounted on surfaces which are not
co-planar with one another but meet at a slight angle, such that
the hook-shaped features impose a slight curvature on of the sheets
on the pouch. This would force the other sheet that is welded to
the first sheet at its edges into an opposite curvature, enlarging
the opening between the sheets at the top of the pouch.
[0105] In some embodiments, the sterile receptacle may be
constructed of two thin sheets welded together at the edges, which
may be opened by de-laminating the weld at one edge of the pouch.
If a user were to completely delaminate both sheets, the pouch
could not be used as a prime discard receptacle because it would
not be able to hold any liquid volume. FIG. 19C shows an
engineering drawing of the sterile receptacle 1900, including
mounting features 1902, first welds 1904, and second welds 1906. In
this embodiment, the welding of the two sheets is configured such
that the user is able to open the pouch to remove its contents
while preventing the user from opening the pouch to such an extent
that it would not be able to hold enough volume to serve as a
discard receptacle. As shown, the first welds 1904 along the side
of the receptacle may be thin up until a point, and then becomes
much thicker, as shown by second welds 1906, such that the
resistance to opening the pouch past the resistance point may be
much higher. This ensures that the user is able to open the
receptacle to remove the cartridge and tubing set, but still be
able to use the receptacle for the prime discard saline.
[0106] An alternative embodiment, as shown in FIG. 26, can include
a cartridge and tubing set that has a receptacle that is
pre-attached to the tubing set (i.e., not the sterile receptacle
that it ships in). The embodiment can include a union joint 256, as
described above, that includes connections to the patient lines as
described above. The embodiment can optionally include a clip as
shown to secure the receptacle and patient lines onto the console
during treatment. In this embodiment, the user can attach and
detach the patient lines to vascular access without needing to
manage the other side of the tubing.
[0107] In yet another example as shown in FIG. 27, the union joint
256 can comprise a 3-way stopcock that includes two female luers
that connect to the patient arterial and venous lines and a male
luer that connects to a pre-attached discard receptacle. The union
joint can be used to direct the flow of saline into the discard
receptacle after a priming sequence. The receptacle can optionally
include a floating cap on the bag to close and seal the bag after
use.
[0108] In another embodiment, the pre-attached receptacle
interfaces with a prime discard valve that is controlled by the
dialysis system. In this embodiment, priming is performed as
described above, and upon completion of priming the dialysis system
can control the prime discard valve to route the priming saline
into the pre-attached receptacle. Alternatively, the dialysis
system itself could include a discard receptacle, and the tubing
set could be configured to automatically discard into the discard
receptacle via the prime discard valve at the completion of a
priming sequence. In some embodiments, the connection between the
discard receptacle on the dialysis system and the blood tubing set
is automatically made when the blood tubing set is mounted onto the
system, as is enabled by the organizer configuration described
above. In these embodiments, flow from the blood tubing set into
the discard receptacle can be controlled automatically by a pinch
valve that engages the tubing of the blood tubing set connector. In
further embodiments, the discard receptacle of the dialysis system
is disinfected by the system's automatic disinfection
sequences.
[0109] At the completion of a dialysis treatment, blood still
remains inside the tubing set. The blood pump 213 can be controlled
to draw saline into the tubing set to push the remaining blood back
into the patient. This blood return mechanism can be highly
controlled by the controller and blood pump of the system. For
example, during dialysis therapy and blood return, the controller
of the system can monitor and track the exact number of revolutions
made by the blood pump when the pinch valves that control saline
administration are open to know exactly how much saline has been
pushed into the tubing set. The blood pump can then be stopped or
de-activated when the desired volume of saline is drawn into the
tubing set. This allows the system to know exactly how much saline
has been used, and how much remains in the saline source or bag. At
the end of the dialysis therapy, the amount of blood in the tubing
set is known (typically around 250 ml), so the system can precisely
meter the correct amount of saline into the tubing set to push the
blood back into the user. The anticipated amount of saline to use
for blood return (typically 300-600 ml depending on the varying
degree of thoroughness of the blood return) can be integrated into
the overall fluid removal target for ultrafiltration so that after
the blood return the patient target weight is attained. If the
needed amount of saline does not remain in the saline source prior
to blood return, the system can alert the user that the saline
source needs to be refilled or replaced.
[0110] In one embodiment, the dialyzer can be flushed prior to
beginning dialysis therapy with a patient. In some cases, clinics
ignore this labeling and do not flush the dialyzer. The system can
be configured to flush the dialyzer with up to 1000 ml of
saline.
[0111] The system can also automatically drain any fluid out of the
dialyzer after a dialysis treatment. In one embodiment, the blood
pump can be run in the reverse direction with the venous line
clamped to pull fluid from the dialysate chamber of the dialyzer
through the dialyzer microtube walls against gravity through the
dialyzer and into the saline source or bag.
[0112] FIG. 7 shows a flow diagram of the water purification system
102 contained within the dialysis system 100. Incoming water, such
as from the tap, can flow through a number of filters, including
one or more sediment filters 108 and one or more carbon filters
110. A chlorine sample port 195 can be placed between the carbon
filters 110 to provide samples of the fluid for measuring chlorine
content. Redundant or dual carbon filters can be used to protect
the system and the user in the event of a carbon filter failure.
The water can then pass through a reverse osmosis (RO) feed heater
140, a RO feed pump 142, one or more RO filters 112 (shown as RO1
and RO2), and a heat exchanger (HEX) 144. Permeate from the RO
filters 112 can be delivered to the HEX 144, while excess permeate
can be passively recirculated to pass through the RO feed pump and
RO filters again. The recirculation helps with operating of the
water purification system by diluting the incoming tap water with
RO water to achieve higher rejection of salts from incoming water.
After passing through the HEX 144, the purified water can be sent
to the dialysis delivery system 104 for preparing dialysate and
assisting with dialysis treatments. Additionally, concentrate from
the RO filters during the water purification process can be sent to
drain 152.
[0113] Referring to FIG. 8, the water purification system 102 of
the dialysis system can include one or more subsystems as described
above in FIG. 7, including a water supply subsystem 150, a
filtration subsystem 154, a pre-heating subsystem 156, an RO
filtration subsystem 158, and a pasteurization or ultrafiltration
subsystem 160. Each of the subsystems above can produce output to a
drain 152. The water purification system 102 can be configured to
purify a water source in real-time for dialysis therapy. For
example, the water purification system can be connected to a
residential water source (e.g., tap water) and prepare purified
water in real-time. The purified water can then be used for
dialysis therapy (e.g., with the dialysis delivery system) without
the need to heat and cool large batched quantities of water
typically associated with water purification methodologies.
[0114] FIG. 9 shows the features of the water supply subsystem 150
of the water purification system, which can include a variety of
valves (e.g., three-way valves, control valves, etc.) for
controlling fluid flow through the water purification system. For
example, at least one valve 2169 can be opened to allow water to
flow into the water purification system for purification. The
incoming water can flow in from a tap water source 2171, for
example. Fluid returning from the water purification system can be
directed to drain 152 through one or more of the valves.
Furthermore, the subsystem can include a supply regulator 183 that
can adjust the water supply pressure to a set value. A drain
pressure sensor 153 can measure the pressure at the drain. Water
can flow from the water supply subsystem 150 on to the filtration
subsystem, described next.
[0115] FIG. 10 shows one embodiment of a filtration subsystem 154
of the water purification system. The filtration subsystem can
receive water from the water supply subsystem 150 described in FIG.
9. Water can first pass through a supply pressure sensor 2173
configured to measure the water pressure and a supply temperature
sensor 2175 configured to sense the temperature of the incoming
water supply. The filtration subsystem can include a sediment
filter 155, for example, a 5-micron polypropylene cartridge filter.
The filter typically requires replacement every 6 months. Based on
the high capacity of the sediment filter and the relatively low
flow rate through the filter, the life expectancy is estimated to
be over 1 year based on the average municipal water quality in the
US. A replacement interval of 6 months provides high assurance that
premature sediment filter fouling should be rare. Also, expected to
be a rare occurrence based on the construction and materials of the
filter is a failure that results in unfiltered water passing
through the filter. A post-sediment pressure sensor 2177 can
measure the pressure drop across the sediment filter to monitor and
identify when the sediment filter needs to be replaced. Should the
sediment filter allow unfiltered water to pass the result would be
fouling of the carbon filters which would be detected by a pressure
drop at post-sediment pressure sensor 2177. If this pressure drop
is the significant factor when the sensor drops to 5 psig, the
system will require replacement of both the carbon filters and the
sediment filters prior to initiating therapy.
[0116] The water can then flow through one or more carbon filters
110 (shown as CF-1 and CF-2) configured to filter materials such as
organic chemicals, chlorine, and chloramines from the water. For
example, the carbon filters 110 can include granulated carbon block
cartridges having 10-micron filters. The carbon filters can be
connected in series with a chlorine sample port 195 positioned in
the flow path between the carbon filters. The chlorine sample port
can provide a user with access (such as through the front panel of
the system) to the flowing water such as for quality control
purposes to ensure the total chlorine concentration level of the
water is below a certain threshold (e.g., below 0.1 ppm).
Additionally, a post-carbon pressure sensor 2179 can be placed
after the carbon filter(s) to monitor the fluid pressure in the
line after the sediment and carbon filtration. As is also shown in
FIG. 10, an optional air separator 187 can be placed between the
sediment filter and the carbon filter(s) to remove excess air and
bubbles from the line. In some embodiments, each carbon filter can
specified to have a service life of 2500 gallons producing water
that has less than 0.5 ppm of free chlorine and chloramine when
operating in high chlorine conditions and at a higher flow rate
than the instrument supports so an expected life of greater than
2500 gallons is expected. Based on a maximum treatment flow rate of
400 mL/min through the carbon filters the expected for a single
carbon filter is approximately 6 months to a year or more depending
on incoming water quality. The system typically requires
replacement of both filters every 6 months. Most carbon filters
cannot tolerate heat or chemical disinfection, therefore a
recirculation/disinfection fluid path, implemented by the water
supply and drain systems, does not include the carbon filters (or
the sediment filters). Since the chlorine absorption capacity of
carbon filters is finite and dependent on the incoming water
quality, a water sample from the chlorine sample port 195 can be
taken to verify that the water has a free chlorine concentration
level of less than 0.1 ppm. Using the two stage carbon filtration
and verifying the "equivalent absence" of free chlorine after the
first carbon filter ensures that the second carbon filter remains
at full capacity in complete redundancy to the first. When the
first carbon filter does expire, both filters are typically
replaced. Water can flow from the filtration subsystem to the
pre-heating subsystem, described next.
[0117] FIG. 11 shows one embodiment of a pre-heating subsystem 156
of the water purification system. The pre-heating subsystem can be
configured to control the temperature of water in the line to
optimize RO filtration performance. The pre-heating subsystem can
include one or more RO feed heaters 186, which can comprise, for
example a thermoelectric device such as a Peltier heater/cooler.
The RO feed heater 186 can be configured to regulate or adjust the
temperature of the water before RO filtration. In one embodiment,
the target temperature for reverse osmosis is 25 degrees C. for
optimal RO filter performance. If the water is too cold the RO
filters will have insufficient flow and the system will not make
enough water. If the water is too warm the RO filters will allow
more flow but also have reduced salt rejection. In one embodiment,
25.degree. C. is the point at which flow and rejection are balanced
to provide sufficient water volume with adequate rejection. The RO
feed heater can be used to both heat or cool the fluid flowing
through the heater. For example, in some embodiments, the RO feed
heater can recover heat from waste water or used dialysate by way
of the Peltier effect. In other embodiments, such as during a heat
disinfect cycle, the RO feed heater can be placed in opposing
polarity to negate Peltier effects. During water treatment, the
incoming water flows through a titanium plate attached to the hot
side of two thermoelectric wafers of the RO feed heater. Waste
water can be directed through a separate titanium plate attached to
the cold side of the wafers. Heat is therefore pumped from the
waste water to the incoming water via the Peltier effect. At
maximum power when the preheating system achieves a coefficient of
performance of two, meaning half of the power heating the incoming
water is recovered from waste water and the other half is from the
electrical heating of the wafers. At lower power levels the
coefficient of performance is higher meaning a higher percentage of
the heat is recovered from the waste stream. During heat disinfect
the thermoelectric wafers of the RO feed heater can be placed in
opposing polarity. In this way both titanium plates are heated and
the Peltier effect is negated. This ensures that the water is
heated only and is always above the incoming temp on either side of
the heater.
[0118] As shown in FIG. 11, the pre-heating subsystem 156 can
include a process supply valve 188 in the line between the
filtration subsystem and the RO feed heater, and a used dialysate
return valve 190 for routing used dialysate to the drain. The RO
feed heater can include a pair of temperature sensors 192 and 194
to measure the temperature of the fluid on either side of the
heater. Water can flow from the pre-heating subsystem to the RO
filtration subsystem, described next.
[0119] FIG. 12 shows one embodiment of a RO filtration subsystem
158 of the water purification system. The RO filtration subsystem
can receive pre-heated water from the pre-heating subsystem
described above. The RO filtration subsystem can include a RO feed
pump 142 that can drive water across one or more RO filters 112
(shown as RO-1 and RO-2) to produce a permeate flow and a
concentrate flow. The concentrate flow can be filtered by more than
one RO filter. In addition, the permeate flow can be combined with
excess permeate and be recirculated back to blend with incoming
water. In addition, each RO filter 112 can include a recirculation
pump 200 to keep fluidic line flow velocity high over the RO
filters. The recirculation pumps can run at a constant velocity,
driving any flow emanating from the concentrate flow back into the
inlet of the RO filters. Using a separate recirculation pump
instead of recirculating through the RO feed pump lowers overall
power consumption and keeps flow velocity over the RO membranes
high to reducing fouling and allow for high water production rates.
In some embodiments, the RO feed pump can be high pressure but
relatively low flow pumps compared to the recirculation pump(s),
which can be low pressure but high flow pumps.
[0120] The pressure created by the RO feed pump and a RO
concentrate flow restrictor 2181 can control the flow rate of waste
to the drain. To ensure that the restriction does not become fouled
or plugged, the flow through the RO concentrate flow restrictor can
be periodically reversed by actuating valves 180. In addition, to
improve filter life and performance, recirculation pumps can be
used to increase fluid flow rate in the RO filter housings. This
increase in flow rate can serve to reduce a boundary layer effect
that can occur near the surface of RO filters where water near the
filter membrane may not flow. The boundary layer can create an area
with a higher concentration of total dissolved solids that can
build up over the surface of the RO filter and may collect and foul
the RO filter.
[0121] The RO filtration subsystem can include on or more
conductivity sensors 196 configured to measure the conductivity of
water flowing through the subsystem to measure solute clearance, or
per, pressure sensors 198 configured to monitor fluid pressures,
and air separators 187 configured to separate and remove air and
air bubbles from the fluid. Additionally, the RO filtration
subsystem can include a variety of valves 180, including check
valves, and fluid pumps for controlling flow through the RO filters
and on to the pasteurization subsystem, back through the RO
filtration subsystem for further filtration, or to the drain. Water
can flow from the RO filtration subsystem to the pasteurization
subsystem, described next.
[0122] FIG. 13 illustrates one embodiment of a pasteurization
subsystem 160 of the water preparation system. The pasteurization
subsystem can be configured to minimize patient exposure to
microbiological contamination by heating the fluid to eliminate
microbiological contamination and endotoxins from the system. The
pasteurization subsystem can include a heat exchanger (HEX) 145
configured to heat water to pasteurization temperature, allow the
water to dwell at the high temperature, and then cool the water
back to a safe temperature for the creation of dialysate.
[0123] In some embodiments, the HEX 145 can heat water received by
the pasteurization subsystem to a temperature of approximately 148
degrees Celsius. The heated water can be held in a dwell chamber of
the HEX for a time period sufficient to eliminate and kill bacteria
and denature endotoxins. Endotoxins can be described as the
carcasses of dead bacteria, characterized by long lipid chains.
During water and dialysate preparation, endotoxins can be monitored
along with bacteria to judge the purity of the dialysate.
Endotoxins in dialysate can cause an undesirable inflammatory
response in users. Therefore, it is desirable to minimize the
levels of endotoxin in the dialysate. Endotoxins are not readily
trapped by the pore size of typical ultrafilters. Instead, the
endotoxins are stopped by ultrafilters through surface adsorption
which can become saturated with endotoxins to the point that
additional endotoxin will start to pass through. Heating endotoxins
in superheated water to temperatures as low as 130 degrees C. have
been demonstrated to denature endotoxins but the required dwell
time is very long (many minutes). At these elevated temperatures,
where the water remains in the liquid phase, water which is
typically considered a polar solvent and begins to behave like a
non-polar solvent to denature the lipid chains of the endotoxin. As
the temperature increases to 220 degrees C. or higher, the
denaturing of endotoxins occurs in seconds. The HEX of the present
disclosure can run at 220 degrees C. or higher while maintaining a
pressure (approximately 340 psi for 220 degrees C., but the HEX can
withstand pressures of over 1000 psi) that keeps the water in
liquid form. In one embodiment, a preferred temperature and
pressure range of the HEX is 180-220 degrees C. and 145-340 psi.
The water can then be cooled as it exits the dwell chamber. The HEX
145 is a self-contained counterflow heat exchanger that
simultaneously heats incoming water and cools outgoing water to
reduce energy consumption.
[0124] The pasteurization subsystem can include a HEX pump 193
configured to maintain a fluid pressure in the fluid line, to
prevent the water from boiling. After the water passes through the
HEX 145, a water regulator 197 can reduce the pressure of the water
for use in the dialysis delivery system. One or more pressure
sensors 182 or temperature sensors 184 can be included for
measuring pressure and temperature, respectively, of the water
flowing through the pasteurization subsystem. Furthermore, an air
separator 187 can further remove air and air bubbles from the
water. In one embodiment, a flow restrictor 189 and valve 180 can
be used to limit water dumped to the drain when the HEX 145 is
heating up. Once the water has passed through the pasteurization
subsystem, it has traveled through the entire water purification
system and is clean and pure enough to be used in dialysate
preparation and delivery by the dialysis delivery system.
[0125] FIG. 28 illustrates a different embodiment of an
ultrafiltration subsystem that may be used in place of
pasteurization subsystem of FIG. 13. This ultrafiltration subsystem
uses a nanometer scale filter (ultrafilter) to remove
microbiological contamination and endotoxins from the system. In
some embodiments, the pore size of the ultrafilter is 5 nanometers.
In some embodiments, the material of the ultrafilter is
polysulfone, although the ultrafilter may comprise any material
known in the art that may be fashioned into a filter structure of
sufficient porosity. The ultrafiltration subsystem can include a
booster pump to provide enough pressure to drive the flow of water
through the ultrafilter. The pressure across the filter can be
monitored by an upstream pressure sensor and a downstream pressure
sensor, which can alert the user of the filter has been clogged and
needs to be changed. Flow maybe diverted to drain through a drain
valve and restrictor if needed. The ultrafiltration subsystem also
comprises a sample port accessible from the exterior of the system
for drawing water to confirm proper functionality of the
ultrafilter. In some embodiments, the ultrafiltration subsystem may
comprise flow through a heat exchanger to facilitate cooling or
heating of fluid paths elsewhere in the system architecture.
[0126] FIG. 14 illustrates a schematic of a mixing subsystem 162 of
the dialysis delivery system. Purified water from the water
purification system can be routed into the dialysis delivery
system, where it can flow through heater 220 in preparation for
final de-aeration in de-aeration chamber 221. In one embodiment,
water flowing into the heater 220 can be approximately 43-47
degrees C., and the heater can heat the water up to 50 degrees C.
or higher. The de-aeration chamber can be, for example, a spray
chamber including a pump sprayer 222. During de-aeration, spray
chamber recirculation pump 225 draws fluid at a high flow rate from
the bottom of the de-aeration chamber. Heated water entering from
the heater 220 then enters the de-aeration chamber above the fluid
level through a pump sprayer 222. The temperature of the water as
it enters and exits the heater can be monitored with temperature
sensors 184. This restrictive spray head in combination with the
high flow rate of the spray chamber recirculation pump 225 creates
a vacuum in the de-aeration chamber ranging from -7 psig to -11
psig. The vacuum pressure and heat combine to effectively de-aerate
the incoming water. As air collects in the top of the de-aeration
chamber and the water level drops below level sensor 2183, the
degas pump 191 can turn on or run faster to remove the collected
air from the top of the de-aeration chamber. The degas pump 191 can
remove a combination of air and liquid from the de-aeration
chamber.
[0127] After de-aeration and subsequent cooling with the heater 220
to approximately body temperature, acid and bicarbonate
concentrates can be volumetrically proportioned into the fluid path
by way of concentrate pumps 223 in order to reach the desired
dialysate composition. The water and concentrates can be mixed in a
series of mixing chambers 224 that utilize a time delay or
volumetric mixing instead of in-line mixing to smooth the
introduction of fluids. FIG. 15 shows one embodiment of a mixing
chamber 224, which can include an inlet portion 236a and an outlet
portion 236b. The mixing chamber can include a plurality of
channels 238 connecting the inlet portion to the outlet portion.
The channels can be arranged so that some of the channels include
longer paths from the inlet portion to the outlet portion than
other channels. Thus, fluid traveling through the channels of the
mixing chamber can be separated and divided along the varying
channel lengths before being recombined to achieve more complete
mixing of "lumpy" incoming fluid by the time it exits the mixing
chamber.
[0128] Smart Flow
[0129] During dialysis therapy, the user has the ability to change
the dialysate flow rate from the dialysis system to suit the
patient's prescription. Oftentimes, this setting is toggled once at
the beginning of the treatment, and the flow rate is held
throughout the entire treatment. Dialysis providers typically set
the maximum dialysate flow rate to maximize the waste clearances,
although studies show that clearance rates witness diminishing
returns at higher flow rates. As most dialysis machines run on a
central water loop, with central dialysis concentrates, there is
typically little incentive to conserve dialysate during
treatment.
[0130] The dialysis system of the present disclosure is unique as
it uses a finite volume of concentrates to proportion dialysate
on-the-fly, as described above. In one embodiment, the dialysis
system of the present disclosure can conserve dialysate concentrate
by actively monitoring the amount of dialysate used during therapy
and modulating the dialysate flow rate to lower the consumption of
acid and bicarbonate concentrates. The ratio of pressures across
the dialyzer (e.g., patient venous pressure, dialysate pressure,
etc.) can be automatically maintained by the dialysis system while
the dialysate flow is lowered, ensuring the appropriate
ultrafiltration profile.
[0131] Depending on treatment goal, running at a lower dialysate
flow rate may be appropriate. For example, running a longer
treatment at lower dialysate and blood flow rates has a gentler
physiological effect on the body, and may be appropriate for
patients dialyzing at night or who have compromised physiology. The
onboard monitoring of dialysate consumption, and real-time
dialysate flow rate control, allows for laissez faire dialysis
treatments while retaining appropriate device efficiency.
[0132] FIG. 20 is a flowchart 2000 showing one example of a method
of monitoring dialysate consumption during therapy and adjusting
dialysate flow rates to conserve dialysate. At step 2002 of
flowchart 2000, a dialysis treatment can be started with the
dialysis system. At step 2004 of flowchart 2000, the dialysis
system can include an option to run a "smartflow" configuration in
which the dialysis system monitors dialysis consumption during
therapy. If smartflow is not selected, or is turned off, then the
treatment or therapy runs as normal at the selected dialysate flow
rate for the course of the treatment, shown by step 2006 of
flowchart 2000.
[0133] If, however, the "smartflow" option is enabled at step 2004,
then at step 2008 of flowchart 2000 the treatment can initially
begin at a selected dialysate flow rate (e.g., 300 ml/min). The
dialysis system can monitor dialysate consumption in real-time, and
at step 2010 of flowchart 2000, the dialysis system can calculate
and determine if the amount of remaining dialysate (or dialysate
concentrates) are enough to complete the scheduled treatment. Step
2010 can be performed constantly during treatment, or can be
performed and repeated at scheduled intervals during the therapy
(e.g., every 30 seconds, every minute, every 5 minutes, etc.).
[0134] If there is enough dialysate remaining to complete the
treatment at step 2010, then at step 2012 the dialysis system can
complete the treatment at the original dialysate flow rate (e.g.,
300 ml/min). If, however, there is not enough dialysate to complete
the treatment, then at step 2014 of flowchart 2000, the dialysate
flow rate can be reduced to a flow rate that permits completion of
treatment with the amount of dialysate on hand (e.g., a flow rate
of 100 ml/min). The dialysis system can be configured to maintain a
pressure within the dialysis system when the flow rate is reduced.
The therapy can continue at the flow rates of steps 2006, 2012, or
2014 until completion of the treatment at step 2016.
[0135] The smartflow calculations of the dialysis system are
determined by comparing the potential dialysate remaining in the
concentrate bottles to the dialysate consumed by a single dialysis
treatment. As the dialysis system operates from dialysate
concentrates of fixed volume, the dialysis system can, in
real-time, calculate the amount of concentrates consumed and adjust
the dialysate flow rate accordingly to conserve concentrate fluids.
The calculation of dialysate used versus dialysate remaining is
determined as following:
[0136] The total dialysate needed for a treatment is calculated by
multiplying the sum of the concentrate and water flow rates by the
total treatment time.
Total Dialysate Needed=(Acid Flow Rate+Bicarb Flow Rate+Water Flow
Rate)*Total Treatment Time (eq. 1)
[0137] Typically, bicarbonate concentrate is the limiting factor,
as it has a higher consumption rate than acid concentrate. As such,
the total dialysate available in any given treatment is dependent
on bicarbonate volume and flow rate:
Amount of Available Time For Bicarbonate=Total Bicarb Volume/Bicarb
Flow Rate (eq. 2)
Dialysate Available=Dialysate Flow Rate*Amount of Available Time
For Bicarbonate (eq. 3)
[0138] The amount of dialysate consumed during a treatment is
calculated real-time.
Dialysate Used=Dialysate Flow Rate*Elapsed Time in Treatment (eq.
4)
[0139] From here, the dialysis system actively calculates the
dialysate flow rate necessary to completely deplete the
concentrates, thus completing the treatment without user
intervention.
Time Remaining in Treatment=Total Treatment Time-Elapsed Time in
Treatment (eq. 5)
Dialysate Flow Rate Necessary=(Dialysate Available-Dialysate
Used)/Time Remaining in Treatment (eq. 6)
[0140] The Dialysate Flow Rate Necessary (eq. 6) for treatment
completion will drop from the initial flow rate over the course of
a treatment. If the calculated Dialysate Flow Rate Necessary falls
to a predetermined set point, the system will immediately modulate
the flow rate to the appropriate, lower, dialysate flow rate in
order to complete the treatment.
[0141] In one embodiment, the concentrate pumps can run at an
elevated rate to push out any air bubbles in the pumping mechanism
(e.g., can run at upwards of 30 ml/min compared to .about.7 ml/min
during normal operation). Once the dialysate is mixed, a dialysate
pump 226 can control the flow of dialysate through the dialysis
delivery system. The mixing subsystem 162 can include various
pressure sensors 182, temperature sensors 184, and conductivity
sensors 196 to monitor the fluid during the dialysate preparation.
The conductivity sensors can be used to measure the fluid ionic
properties to confirm that the composition is correct.
[0142] The flow path within the dialysate delivery system can
include one or more bypass or circulation routes that permit
circulation of cleaning and/or sterilization fluid through the flow
path. The circulation route may be an open flow loop wherein fluid
flowing through the circulation route can be dischargeable from the
system after use. In another embodiment, the circulation route may
be a closed flow loop wherein fluid flowing through the circulation
route is not dischargeable from the system.
[0143] A method of providing dialysis therapy to a patient is
provided, comprising combining a dialysate concentrate and water
with a dialysate system to produce a dialysate on-demand, providing
a first flow of the dialysate through the dialysis system at a
first dialysate flow rate, monitoring consumption of the dialysate
concentrate by the dialysis system, determining if enough dialysate
concentrate remains to complete the dialysis therapy at the first
dialysate flow rate, and if there is not enough dialysate
concentrate to complete the dialysis therapy at the first dialysate
flow rate, calculating a second dialysate flow rate that allows for
completion of the dialysis therapy, and providing a second flow of
the dialysate through the dialysis system at the second dialysate
flow rate.
[0144] In some examples, the dialysis system houses a finite supply
of dialysate concentrate. In another example, the second dialysate
flow rate is lower than the first dialysate flow rate. In one
example, the first dialysis flow rate is approximately 300 ml/min,
and the second dialysis flow rate is approximately 100 ml/min.
[0145] In one example, the determining step further comprises
determining if enough dialysate concentrate remains based on the
first dialysate flow rate, an amount of dialysate concentrate
remaining, and a total treatment time. In one example, the method
further includes maintaining a pressure within the dialysis system
when the second flow of dialysate is provided.
[0146] FIG. 16 illustrates an ultrafiltration subsystem 164 of the
dialysis delivery system which can receive the prepared dialysate
from the mixing subsystem. The ultrafiltration subsystem is
configured to receive prepared dialysate from the mixing subsystem
162. Dialysate pump 226 and used dialysate pump 227 can be operated
to control the flow of dialysate through the ultrafiltration
subsystem. The pumps 226 and 227 can control the flow of dialysate
to pass through an ultrafilter 228 and a dialysate heater 230
before entering dialyzer 126. Temperature sensors 184 can measure
the temperature of the dialysate before and after passing through
the dialysate heater 230. The dialysate heater can be user
configurable to heat the dialysate based on the user's preference,
typically between 35-39 degrees C. After passing through the
dialyzer, the used dialysate can flow through a used dialysate pump
230 and back through the dialysate heater 228 before returning to
drain. In one embodiment, the degas pump from FIG. 14 can be used
to wet the back of the used dialysate pump 227. The ultrafiltration
subsystem can include one or more actuators or valves 177 that can
be controlled to allow dialysate to pass through the dialyzer 126,
or alternatively, to prevent dialysate from passing through the
dialyzer in a "bypass mode". A pressure sensor 182c disposed
between the dialysate pump 226 and the used dialysate pump 227 can
be configured to measure a pressure of the dialysate between the
pumps when dialysate is prevented from passing through the dialyzer
in the "bypass mode".
[0147] FIG. 17 illustrates a blood circuit subsystem 166 which is
configured to pull blood from the patient and create a flow of
blood through the dialyzer during dialysis therapy to pass fluid
from the blood-side of the dialyzer to the dialysate-side of the
dialyzer or vice versa. As described above, the blood circuit
subsystem 166 can include, among other features described herein,
the tubing set 122, blood pump 213, pinch valves 180a-d, venous
drip chamber 361, venous level sensor(s) 181, arterial line 230,
and venous line 232, saline source 240, and infusion pump 242. The
blood pump 213 can be controlled to operate in first and second
modes of operation. During dialysis therapy, the blood pump 213 can
be operated in a first operating mode in which the pump pulls blood
from the patient through arterial line 230, flows through the
tubing set in the direction of arrow 244, flows through the
dialyzer 126, flows through the venous drip chamber 361, and is
returned to the patient through venous line 232. The blood pump can
also be operated in a second operating mode in which the pump
direction is reversed to cause fluid in the lines to flow in the
direction of arrow 246 (for example, during a priming sequence as
described above.
[0148] The blood circuit subsystem can also include a venting
circuit 248 adapted to automatically control the fluid level in
venous level chamber 361, as described above. The venting circuit
can include a bi-directional peristaltic pump 250. The venous
pressure sensor 182a of the system can also be located in the
venting circuit 248. During dialysis therapy, the venous level
sensor(s) 181 can monitor a fluid level of blood in the venous drip
chamber 361. The electronic controller can receive the fluid level
information from the sensor(s) and automatically maintaining the
fluid level of the blood in the venous drip chamber by pumping or
venting air out of the venous drip chamber with bi-directional
peristaltic pump 250 and/or venting valves 252 if sensor(s) detect
the fluid level dropping below a lower threshold, and by pumping
air into the venous drip chamber with bi-directional peristaltic
pump 250 if the sensor(s) detect the fluid level rising above an
upper threshold.
[0149] Still referring to FIG. 17, a method of returning blood in
the tubing set to the patient after dialysis therapy will be
described. First, the user can clamp the line on their arterial
needle (not shown in diagram) at the point where the arterial line
230 enters their body. This clamp can be located in between saline
connection 353b and the user's body. The user can then confirm
ACLMP is open, which is another clamp on the arterial line distal
to the saline connection 353b. Next, the electronic controller of
the dialysis system can open pinch valves 180b and 180c, and close
pinch valve 180a. Next, the electronic controller can direct blood
pump 213 to operate in the "forward direction" to draw saline from
the saline source (e.g., a saline bag) into the arterial line 230
at saline connection 353b through pinch valve 180b, which is very
close to where the arterial line connects to the patient. The blood
pump can operate for a specified time, or can run until a
predetermined volume of saline (e.g., 300-600 ml) is drawn into the
tubing set, to return the blood in the tubing set and dialyzer into
the patient through venous line 232. In some embodiments, the blood
return process can be manually stopped based on the color of the
saline in the tubing set (i.e., stopping the blood pump when the
color of the saline becomes clear or a light-pink color).
[0150] The dialysate pump and used dialysate pump described above
can be part of an electronic circuit in communication with the
electronic controller of the dialysis system to achieve a
controlled ultrafiltration rate, and can also be adjusted to
precisely control the addition or removal of fluid to or from the
patient.
[0151] The dialysate pump and used dialysate pump can be controlled
with a high degree of precision to achieve dynamic balancing,
periodic balancing, and continuous correction. Referring to FIGS.
16-17, dialysate pump 226 and used dialysate pump 227 can be
configured to pump dialysate through the dialysis delivery system.
The dialysate pump can be controlled to push the dialysate through
the ultrafilter and the dialysate heater to get heated.
[0152] To calibrate the flow of the system, the system can be
controlled to enter a bypass mode in which valves 177 are actuated
to prevent dialysate flow through the dialyzer. This isolates the
patient tubing set on the blood side of the dialyzer from the
dialysate flow and creates a closed system for dialysate flow that
will not allow ultrafiltration. Whenever the system is in bypass
the used dialysate pump can be servoed to maintain constant
pressure as measured by pressure sensor 182c, which is positioned
between the dialysate pump 226 and used dialysate pump 227. The
pump speed of the used dialysate can be adjusted while the pump
speed of the dialysate pump is maintained at a constant speed until
the pressure measured by pressure sensor 182c stabilizes. Once the
pressure is stabilized, the pump speed of the used dialysate pump
vs the pump speed of the dialysate pump can be recorded as the pump
speed ratio that results in zero ultrafiltration. When the systems
exits bypass and returns to dialysis therapy, the used dialysate
pump speed can be adjusted based on the desired ultrafiltration
rate.
[0153] When dialyzer is bypassed, pressure measurements of the
dialysate can be made independent of influences or pressures from
the blood-side of the dialyzer (e.g., isolated from the blood
tubing set). When the dialysate and used dialysate pumps operate at
the same rate there is no pressure change at pressure sensor 182c
positioned between the two pumps, so there is no flow imbalance
between the pumps. However, if the dialysate and used dialysate
pumps operate at different rates then a flow imbalance is created
between the pumps, and a pressure change representing this flow
imbalance can be measured at pressure sensor 182c. In some
embodiments, the flow imbalance can be controlled based on the pump
strokes of the respective pumps. In other embodiments, the flow
imbalance can be controlled based on lookup tables that determine
the optimal pump speeds based on the measured venous pressure. The
electronic controller of the system can be configured to
automatically control the flow of fluid across the dialyzer (i.e.,
ultrafiltration) by adjusting a pump speed of the used dialysate
pump 227 with respect to dialysate pump 226 (or alternatively, of
the dialysate pump 226 with respect to used dialysate pump 227) to
create a flow imbalance between the dialysate-side and blood-side
of the dialyzer. When a flow imbalance is created on the
dialysate-side of the dialyzer by operating the pumps 226 and 227
at different speeds, then fluid can flow across the dialyzer
membranes from the blood-side to the dialysate-side, and vice
versa, to equalize that flow imbalance.
[0154] The pump speeds of the dialysate pump 226 and used dialysate
pump 227 can be locked in by the system based on a desired rate of
ultrafiltration, and valve 180 can be opened for normal operation
during dialysis therapy. During therapy, the system can continue to
monitor venous pressure on user side at pressure sensor 182a. If
the venous pressure changes (e.g., greater than 30 mm-Hg mercury in
change), the system can be configured to automatically rebalance
the pumps with the same technique described above. This allows the
pumps to be balanced to achieve the desired amount of fluid
transfer through the dialyzer, or alternatively, to achieve no
fluid transfer through the dialyzer. In one specific embodiment,
the system can detect changes in the venous pressure of the user
and automatically adjust the speed of the used dialysate pump 227
based on a look-up table of speeds against venous pressure to
maintain ultrafiltration balance in the user. Once the system has
been calibrated, the used dialysate pump speed can be modulated to
adjust the rate of fluid removal from the patient. In some
embodiments, a pump speed of the used dialysate pump can be
alternatively increased or decreased relative to the dialysate pump
to enable hemodiafiltration (e.g., pushing/pulling fluid onto the
patient).
[0155] In some embodiments, there are two phases of operation of
the dialysate pump and the used dialysate pump. In the first phase
of operation, the speed of the used dialysate pump is greater than
the speed of the dialysate pump, resulting in net fluid flux from
the blood side of the dialyzer and into the dialysate side of the
dialyzer. The speed differential may be set such that fluid is
removed from the patient's blood at a rate that is physiologically
tolerable over a short duration, perhaps up to a rate of 100
mL/min. To achieve this, for example, the dialysate pump may be set
to run at 300 mL/min, and the used dialysate pump may be set to run
at 400 mL/min. In this phase, convective clearance of solutes is
increased. However, because of a limited volume of fluid in the
patient's circulation, indefinite application of this first phase
of operation is not sustainable, as it would hemo-concentrate the
blood in the dialyzer. In the second phase of operation, the speed
of the dialysate pump is greater than the speed of the used
dialysate pump, resulting in net fluid flux from the dialysate side
of the dialyzer into the blood side of the dialyzer. In this second
phase, at least some of the fluid removed from the patient's
circulation during the first phase is replaced, allowing the first
phase to be repeated. Convective clearance of solutes is reduced
during the second phase, although diffusive clearance would still
take place. Current systems that are used for hemodiafiltration
typically inject replacement fluid into the patient's
extracorporeal circuit directly, which requires extremely high
standards for microbiological purity. These replacement fluids are
typically pre-manufactured and provided in large bags, which are
cumbersome to handle and add considerable cost. In the disclosed
invention, the replacement fluid is produced on-line and is
additionally filtered by the dialyzer before coming into contact
with the patient's blood, obviating the need for pre-manufactured
fluids and direct connections into the patient's extracorporeal
circuit. In some embodiments, the duration and/or net fluid flux of
the first phase of the second phase are equal. In some embodiments,
the duration and/or net fluid flux of the first phase and the
second phase are not equal. In further embodiments, the net fluid
flux produced by the two phases sum up to equal the total fluid
removal goal during the treatment. In further embodiments, the
invention comprises a plurality of any number of operating phases
with varying durations and/or net fluid fluxes, or a continuum
thereof.
[0156] Pump Burn-in
[0157] The dialysis system described herein includes a number of
pumps, including pumps that may interact directly with fluids such
as dialysate, saline, or blood that are delivered to the patient. A
vane pump can include internal graphite components whereas the gear
pump can include of PEEK materials which shed off during normal
pump operations. These particles may enter components such as
filters or regulators of the dialysis system which may result in
premature failures. By design, vane pumps and gear pumps operate
under a positive displacement principle, where internal pump
components will grind against one another to move fluid. As such,
surface imperfections on the internal pump components will continue
to shed over use. Under high temperature and/or pressure
conditions, the stress on the internal pump components will
increase, thereby increasing the amount of shedding observed. This
disclosure provides a vane and gear pump burn in process designed
to reduce particulate shedding amounts during dialysis system
operation.
[0158] The intent of a burn-in process is to remove loose
particulates present in the pumps by running the pumps at elevated
temperatures and/or elevated pressures during the first few hours
of the pumps lifetime. For example, the process can include running
the pumps at temperatures and/or pressures that are higher than the
temperatures and pressures that the pumps will encounter during
normal operation. In running these pumps in an extreme condition,
the surface imperfections on the internal pump will be sanded down,
thus making a more flush interface between components. Smooth to
smooth surface contact on internal vanes and gears yields fewer
particulates shed, thereby preventing premature failure of other
components in the system. In one example, running these pumps at 70
deg C. and 100 psi for 8 hours maximizes the amount of infant
shedding, thus leading to reduced shedding during normal operation
modes (25 deg C. and 100 psi).
[0159] FIG. 21 illustrates a fluidic schematic of a pump burn-in
fixture. The pump burn-in fixture can be used to burn in vane
and/or gear pumps to remove loose particulates prior to installing
the pumps in a dialysis system. Several vane pumps and gear pumps
may be run in parallel in the pump burn-in fixture. In one
embodiment, the fixture can include a computer running an embedded
program to control the pumps. In another embodiment, the burn-in
fixture may be controlled by a voltage control potentiometer. The
pump burn-in fixture can form a closed-loop fluidic path with one
or more pumps under test when the pumps are connected to the pump
burn-in fixture. In some embodiments, the pump burn-in fixture can
include one or more heating elements configured to heat a fluid
within the pump burn-in fixture to temperatures higher than what
the pumps are exposed to during normal operation. For example, the
heating elements can be configured to heat a fluid within the pump
burn-in fixture to temperatures up to and including 100 deg C. In
one example, a preferred temperature for the fluid within the pump
burn-in fixture is 70 deg C.
[0160] FIGS. 22 and 24 are pictures of the pump burn-in fixture
from FIG. 21, including the closed-loop fluidic path between the
pumps and the fixture. FIG. 22 also illustrates a computer or
electronic controller (e.g., a laptop) controlling the software
which controls operation of the pump burn-in fixture.
[0161] FIGS. 23 and 25 are pictures showing additional electronics
that drive the burn-in fixture, including a power supply that can
toggle 24 VDC and 48 VDC, and provide power to the microcontrollers
and motor drivers to actuate the pumps.
[0162] A method of improving durability and operation of one or
more displacement pumps, can comprise connecting one or more
displacement pumps to a pump burn-in fixture to form a closed-loop
fluidic path between the one or more displacement pumps and the
pump burn-in fixture, increasing a temperature and pressure of
fluid within the closed-loop fluidic path, and operating the one or
more displacement pumps to flow the fluid through the closed-loop
fluidic path for a predetermined period of time to reduce surface
imperfections internal to the one or more displacement pumps.
[0163] In some embodiments, the increasing step further comprises
increasing the temperature and pressure of the fluid to levels that
are above what the one or more displacement pumps encounter during
normal operation. For example, this can include increasing the
temperature of the fluid above 25 deg C. In another example, the
method can include increasing the pressure of the fluid above 100
psi.
[0164] As described above, the water purification system and the
dialysate delivery system can both include a variety of pumps,
valves, sensors, air separators, air sensors, heat exchangers, and
other safety features. All of these features can be controlled
electronically and automatically by the electronic controller of
the dialysis system.
[0165] Automated Conductivity Calibration
[0166] The dialysis system described herein includes a number of
conductivity sensors to monitor the quality of the incoming water,
the effectiveness of the water purification system and to ensure
proper proportioning of the dialysate fluid generated. As with many
sensors, it can necessary to perform periodic re-calibration of
these sensors to ensure accuracy. Typically, each conductivity
sensor is calibrated in isolation, where the fluid connections to
the rest of the system on either side of the sensor are broken, and
then re-connected to a source of conductivity calibration fluid and
a calibrated external conductivity meter. This conductivity
calibration fluid which has a known conductivity, is passed through
the sensor, and additionally verified by the external conductivity
meter, which verifies that the sensor under test is properly
calibrated, or allows for adjustment of its calibration constants
if it is out of calibration. The type of calibration fluid used may
be different for each sensor, as the conductivity range it is meant
to read could be different from other conductivity sensors in the
system. Disclosed herein is a method to perform automated
calibration of all the conductivity sensors within the system that
does not require breaking the fluidic path. In some embodiments,
the automatic conductivity calibration method comprises connecting
a calibration fluid concentrate to the acid or bicarbonate pumps.
Optionally, an external conductivity meter may be connected to the
fluidic circuit of the system, for example using the inlet and
outlet connectors that are used to connect to a dialyzer. Using the
proportioning pumps, the system will mix the calibration fluid
concentrate and purified water produced by the water purification
module to produce a calibration fluid of a nominally known
conductivity. In this state, the fluidic path of the system is a
single-pass flow through, where the mixed fluid is sent to drain.
Once the conductivity of the mixed calibration fluid has
stabilized, the proportioning pump(s) can be stopped, and the
fluidic path of the system is automatically reconfigured to
recirculate the fluid instead of sending it to drain. The
recirculation path of the system can be configured to include all
the conductivity sensors within the system, including the optional
external conductivity meter, which will now all be exposed to the
same recirculating fluid. Measurements from any or all of the
conductivity sensors can then be compared with other sensors,
including the optional external conductivity sensor, and
calibration constants may be adjusted as needed. In some
embodiments, the this process can be automatically repeated
multiple times, with different mixing ratios of calibration fluid
producing final mixed fluids of different conductivities. As such a
multi-point calibration curve can be generated. Furthermore,
conductivity sensors in different portions of the fluid path
typically sense fluids of different conductivity ranges. The
calibration fluid can be sequentially proportioned to cover the
different typical operating ranges of the different conductivity
sensors. Calibration of the each of the conductivity sensors can be
more heavily weighted, or done exclusively, with calibration fluid
representative of its native operating range.
* * * * *