U.S. patent application number 13/709731 was filed with the patent office on 2013-04-18 for systems and methods for optical access disconnection.
This patent application is currently assigned to Baxter Healthcare S.A.. The applicant listed for this patent is Baxter Healthcare S.A., Baxter International Inc.. Invention is credited to Robert Childers, Rodolfo Roger, Joel Tejedor.
Application Number | 20130096481 13/709731 |
Document ID | / |
Family ID | 39535140 |
Filed Date | 2013-04-18 |
United States Patent
Application |
20130096481 |
Kind Code |
A1 |
Roger; Rodolfo ; et
al. |
April 18, 2013 |
SYSTEMS AND METHODS FOR OPTICAL ACCESS DISCONNECTION
Abstract
An access disconnection system includes: a material capable of
absorbing blood from a patient, a light emitter positioned to emit
light onto a first portion of the material, the first portion
spaced at least a threshold distance from a second portion of the
material, the second portion located so as to cover arterial line
and venous line access points to the patient, the threshold
distance including a distance from the access points to provide for
an allowable amount of blood seepage from either access point due
to a needle stick, a receiver positioned adjacent to the light
emitter to receive light reflected off of the first portion of the
material, and circuitry coupled to the light emitter and receiver
and configured to provide an output (i) when light received by the
receiver reaches a particular level or (ii) indicative of an amount
of light received by the receiver.
Inventors: |
Roger; Rodolfo; (Clearwater,
FL) ; Tejedor; Joel; (Largo, FL) ; Childers;
Robert; (Trinity, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Baxter International Inc.;
Baxter Healthcare S.A.; |
Deerfield
Glattpark (Opfikon) |
IL |
US
CH |
|
|
Assignee: |
Baxter Healthcare S.A.
Glattpark (Opfikon)
IL
Baxter International Inc.
Deerfield
|
Family ID: |
39535140 |
Appl. No.: |
13/709731 |
Filed: |
December 10, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11673395 |
Feb 9, 2007 |
8376978 |
|
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13709731 |
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Current U.S.
Class: |
604/6.09 ;
604/6.16 |
Current CPC
Class: |
A61M 2205/15 20130101;
A61M 2205/3569 20130101; A61M 1/3656 20140204; A61M 2205/13
20130101; A61M 2205/3313 20130101; A61M 1/30 20130101; A61M
2205/8206 20130101; A61M 1/3661 20140204; A61M 2205/17 20130101;
A61M 2205/3592 20130101; A61M 2230/65 20130101; A61M 1/3653
20130101 |
Class at
Publication: |
604/6.09 ;
604/6.16 |
International
Class: |
A61M 1/30 20060101
A61M001/30 |
Claims
1. An access disconnection system comprising: a material capable of
absorbing blood from a patient; a light emitter positioned to emit
light onto a first portion of the material, the first portion
spaced at least a threshold distance from a second portion of the
material, the second portion located so as to cover arterial line
and venous line access points to the patient, the threshold
distance including a distance from the access points to provide for
an allowable amount of blood seepage from either access point due
to a needle stick; a light receiver positioned adjacent to the
light emitter to receive light reflected off of the first portion
of the material; and electronic circuitry operably coupled to at
least one of the light emitter and receiver, the circuitry
configured to provide an output (i) when light received by the
light receiver reaches a particular level or (ii) indicative of an
amount of light received by the light receiver.
2. The access disconnection system of claim 1, wherein the
threshold distance is between approximately one inch (2.54 cm) and
three inches (7.62 cm).
3. The access disconnection system of claim 1, wherein the
threshold distance corresponds to a distance from the access points
such that blood from either access point reaching the first portion
of the material is indicative of a line disconnection.
4. The access disconnection system of claim 1, wherein the light
emitter and the light receiver are a first light emitter and a
first light receiver, and which includes: a second light emitter
positioned to emit light onto a third portion of the material that
is at least the threshold distance from the second portion of the
material; and a second light receiver positioned adjacent to the
second light emitter to receive light reflected off of the third
portion of the material.
5. The access disconnection system of claim 4, wherein the
electronic circuitry is operably coupled to at least one of the
second light emitter and second light receiver, the circuitry
configured to provide the output (i) when light received by at
least one of the first light receiver or the second light receiver
reaches the particular level or (ii) indicative of the amount of
light received by the first light receiver and the second light
receiver.
6. The access disconnection system of claim 4, wherein the
electronic circuitry is configured to provide the output when light
received by both the first light receiver and the second light
receiver reaches the particular level.
7. The access disconnection system of claim 4, wherein the third
portion of the material is located on an opposite side of the
access points from the first portion of the material.
8. The access disconnection system of claim 4, wherein the second
light emitter is positioned to be closer to the access points than
the first light emitter.
9. The access disconnection system of claim 1, which includes an
attachment mechanism operable to attach the material to an arm of
the patient.
10. The access disconnection system of claim 1, wherein the light
emitter emits light having a wavelength causing the light to be
absorbed by blood.
11. The access disconnection system of claim 1, which includes at
least one of: (i) the material being gauze; (ii) the light emitter
being a light emitting diode; and (iii) the light receiver being a
photocell or phototransistor.
12. The access disconnection system of claim 1, which includes a
film positioned between the material and the light
emitter/receiver, the material selected to allow light to pass
through the material.
13. The access disconnection system of claim 1, wherein the
electronic circuitry is configured to provide the output when light
received by the receiver falls below the particular level.
14. The access disconnection system of claim 1, wherein the
particular level is an at least substantially no-light received
level.
15. The access disconnection system of claim 1, wherein the output
is of a type selected from the group consisting of: an electrical
output and a radio frequency output.
16. The access disconnection system of claim 1, which includes a
blood treatment unit, the output sent to the blood treatment
unit.
17. The access disconnection system of claim 16, wherein the blood
treatment unit performs at least one of: (i) determines if the
amount of light received warrants an access disconnection
condition; (ii) alarms the patient upon receiving the output; and
(iii) shuts down at least one of a blood pump and a dialysate pump
upon receiving the output.
18. The access disconnection system of claim 1, which includes at
least one of: (i) a plurality of light emitters; (ii) a plurality
of light receivers; and (iii) a battery supply to at least one of
the light emitter(s) and light receiver(s).
19. The access disconnection system of claim 1, which is a
redundant system that combines one of: (i) an electrical impedance
access disconnection detector, (ii) an ultrasound access
disconnection detector, (iii) an acoustic access disconnection
detector and (iv) a bioimpedance access disconnection detector with
the light emitter, light receiver and electronic circuitry.
20. An access disconnection system comprising: a material capable
of absorbing blood from a patient; a plurality of light emitters
positioned to emit light onto respective portions of the material,
each portion spaced at least a threshold distance from an access
portion of the material, the access portion located so as to cover
arterial and venous line access points to the patient, the
threshold distance being defined as a distance from the access
points that provides for an allowable amount of blood seepage from
either of the access points due to a needle stick; a plurality of
light receivers positioned adjacent to the respective light
emitters to receive light reflected off of the respective portions
of the material; and electronic circuitry operably coupled to at
least one of the plurality light emitters and light receivers, the
circuitry configured to provide an output (i) when light received
by at least one of the light receivers reaches a particular level
or (ii) indicative of an amount of light received by at least one
of the light receivers.
21. The access disconnection system of claim 20, wherein the
electronic circuitry is configured to provide the access
disconnection output when light received by the at least one of the
light receivers falls below the particular level.
22. The access disconnection system of claim 20, wherein the
threshold distance corresponds to a distance from the access points
such that blood from the access points reaching one of the emitter
portions of the material is indicative of a line disconnection.
23. The access disconnection system of claim 20, wherein the
plurality of light emitters are located different distances from
the access points.
24. The access disconnection system of claim 23, wherein the
electronic circuitry is configured to calculate a rate of blood
loss based upon when the light received by each of the light
receivers reaches the particular level.
25. The access disconnection system of claim 24, wherein the
electronic circuitry is configured to transmit an output to trigger
an alarm if the rate of blood loss is greater than a predetermined
threshold.
26. The access disconnection system of claim 20, wherein the
threshold distance is at least approximately one inch (2.54
cm).
27. An access disconnection detection method comprising:
positioning a light emitter to emit light onto a first portion of a
material capable of absorbing blood from a patient, the first
portion being spaced at least a threshold distance from a second
portion of the material, the second portion located so as to cover
arterial line and venous line access points to the patient, the
threshold distance including a distance from the access points to
provide for an allowable amount of blood seepage from either access
point due to a needle stick; positioning a light receiver adjacent
to the light emitter to receive light reflected off of the first
portion of the material; and providing an output (i) when light
received by the light receiver reaches a particular level or (ii)
indicative of an amount of light received by the light receiver.
Description
PRIORITY CLAIM
[0001] This application claims priority to and the benefit as a
continuation application of U.S. patent application Ser. No.
11/673,395, filed Feb. 9, 2007, entitled, "Optical Access
Disconnection Systems and Methods", the entire contents of which
are hereby incorporated by reference and relied upon.
BACKGROUND
[0002] The present disclosure relates generally to patient access
disconnection systems and methods for medical treatments. More
specifically, the present disclosure relates to the detection of a
patient access disconnection, such as the detection of needle or
catheter dislodgment during dialysis therapy.
[0003] FIG. 1 illustrates a known access disconnection
configuration. Blood is drawn from an arm 12 of a patient through
an arterial line 14 connected the patient via an arterial needle
16. Blood is returned to the patient, after it has been treated,
via a venous line 18 and venous needle 20. Needles 16 and 20
actually connect to a shunt 22, which is placed in fluid
communication with one of the patient's arteries and veins.
Accidental disconnection of the arterial line 14 during treatment
is not as serious an issue as this simply eliminates the source of
blood to the blood pump. Access disconnection of venous line 18
during treatment is a serious concern because arterial line 14
keeps feeding blood to the blood pump, while venous line 18 returns
blood to a location outside of the patient.
[0004] A variety of different medical treatments relate to the
delivery of fluid to, through and/or from a patient, such as the
delivery of blood between a patient and an extracorporeal system
connected to the patient via a needle or needles inserted within
the patient. For example, plasmapherisis, hemodialysis,
hemofiltration and hemodiafiltration are all treatments that remove
waste, toxins and excess water directly from the patient's blood.
During these treatments, the patient is connected to an
extracorporeal circuit and machine, and the patient's blood is
pumped through the circuit and machine. Waste, toxins and excess
water are removed from the patient's blood, and the blood is
infused back into the patient.
[0005] In these treatments, needles or similar access devices are
inserted into the patient's vascular system so that the patient's
blood can be transported to and from the extracorporeal machine.
Traditional hemodialysis, hemofiltration and hemodiafiltration
treatments can last several hours and are generally performed in a
treatment center about three to four times per week. In in-center
treatments, patients undergoing hemodialysis, for example, are
monitored visually to detect needle dislodgment. However, the
needle may not be in plain view of the patient or medical staff
(e.g., it may be covered by a blanket) such that it could delay
detection and timely response.
[0006] Moreover, in view of the increased quality of life, observed
reductions in both morbidity and mortality and lower costs with
respect to in-center treatments, a renewed interest has arisen for
self-care and home therapies, such as home hemodialysis. Such home
therapies (whether hemodialysis, hemofiltration or
hemodiafiltration) can be done during the day, evening or
nocturnally. If unsupervised or asleep, dislodgment risks increase
because a caregiver is not present and perhaps even the patient is
not aware of a dislodgment.
[0007] Various systems exist for detecting needle dislodgement in
hemodialysis. For example, U.S. Pat. Nos. 7,022,098 ("the '098
patent") and 7,052,480 ("the '480 patent"), both entitled Access
Disconnection Systems And Methods, and assigned to the eventual
assignee of the present application, disclose access disconnection
systems that measure an electrical impedance of the extracorporeal
dialysis circuit connected to the vascular access needles. An
external voltage or current source is used to inject a small
current (e.g., less that 2.5 .mu.-Amp) into the blood flow. While
this external current is small compared to other systems, the
source still requires that measures be taken to ensure that the
current does not exceed 10 .mu.-Amp, which is considered in the art
to be a safety limit for intercardiac devices. Further, sensitivity
of the impedance system can be decreased when the patient is
connected to earth ground (e.g., through grounding devices found in
clinics and homes).
[0008] Another problem with systems that inject current into the
extracorporeal circuits occurs if the dislodged needle
reestablishes contact with the other needle through leaked blood.
Here, the electrical parameter being sensed, e.g., impedance, may
not change or not change enough to signal an access disconnection
even though one has occurred.
[0009] A further obstacle involves the addition of contacts to the
disposable portion of the blood treatment system. Metal or
otherwise conductive members placed in the disposable add a certain
amount of manufacturing difficulty and cost.
[0010] A need accordingly exists for improved blood access
disconnection systems.
SUMMARY
[0011] The examples described herein disclose access disconnection
systems and methods applicable for example to: plasmapherisis,
hemodialysis ("HD"), hemofiltration ("HF") and hemodiafiltration
("HDF"). The access disconnection systems may also be used with
continuous renal replacement therapy ("CRRT") treatments requiring
vascular access. The access disconnection examples below operate
with systems having a diffusion membrane or filter, such as a
dialyzer, e.g., for HD or HDF, or a hemofiliter, e.g., for HF.
[0012] Moreover, each of the systems described herein may be used
with clinical or home setting machines. For example, the systems
may be employed in an in-center HD, HF or HDF machine, which runs
virtually continuously throughout the day. Alternatively, the
systems may be used in a home HD, HF or HDF machine, which is run
at the patient's convenience. One such home system is described in
U.S. Pat. No. 8,029,454 ("the '454 patent"), entitled "High
Convection Home Hemodialysis/Hemofiltration And Sorbent System,"
filed Nov. 4, 2004, assigned to the eventual assignee of the
present application, the entire contents of which are incorporated
herein expressly by reference.
[0013] The access disconnection examples below operate with systems
having a dialysate (infusate) supply, which can be a single bag or
multiple bags of dialysate supply ganged together and used one
after another. Further alternatively, each of the access
disconnection systems shown below can be used with a machine having
an on-line source, such as one or more concentrate pump configured
to combine one or more concentrate with water to form dialysate
on-line. On-line sources are used commonly with HD systems for
example.
[0014] Various non-invasive access disconnection systems are
described herein. The systems by and large do not inject a voltage
or current into the patient. This illuminates problems with patient
grounding inherent in current inducing systems. Because the systems
do not rely on the connection or disconnection of an electrical
loop, they tend to be immune from the reestablishment of a
conductive path with a dislodged needle and lost blood. The
disclosed systems in various embodiments communicate with the
dialysis machine wirelessly, e.g., through a radio frequency
signal. In this manner, the systems do not add to the disposable
tubing and/or cassette that the machine uses, increasing
manufacturing feasibility and reducing cost.
[0015] A first system uses a piezoelectric or electromagnetic
transducer (referred to hereafter generally as piezoelectric for
convenience) operating for example in the Mega-Hertz frequency
range, which transmits ultrasound waves into tissue. The
transducer's body is parallel to the tissue in one embodiment while
the piezoelectric itself is at an angle to produce ultrasound
components aligned with blood flow direction.
[0016] Red cells in the blood stream act as reflectors for the
ultrasound, echoing the wave back into the transducer. Another
piezoelectric or electromagnetic crystal (referred to hereafter
generally as piezoelectric for convenience) can be used to receive
the echoes. Ultrasound frequency is changed as the wave reflects on
the blood cells via the Doppler effect. The changes in frequency of
the ultrasound signal are an indication of the speed of the
reflecting cells. The first system processes the received echoes
and extracts flow rate information.
[0017] The first system as mentioned uses a piezoelectric
transmitter and a piezoelectric receiver or a single transducer
that performs both functions. Electronic circuitry is connected to
the transducers or transducer to produce the excitation signals and
to process the echoes. In one implementation, the electronics also
include a radio frequency ("RF") link to the hemodialysis
instrument. Once the treatment has started, the ultrasound device
gathers information from the blood stream. Peak speed of
reflectors, pulsatile characteristics of the blood flow, turbulence
in the access are some of the parameters that are monitored as
described in more detail below. The access disconnection system
exchanges such information with the dialysis instrument via the RF
link. Venous needle dislodgement will necessarily introduce a
radical change in the sensed parameters, allowing access disconnect
detection.
[0018] In one implementation of the first access disconnection
system, the ultrasound transducer is held in place with a band via
a hook and loop assembly, magnetic coupling or other buckle
mechanism. The band offers tube restraining to mechanically prevent
needle dislodgement.
[0019] A second access disconnection system uses the propagation
properties of sound in blood within the extracorporeal circuit to
determine for example if the venous section of the extracorporeal
circuit is connected to the patient. The second system uses at
least one acoustic transducer, which generates a sound wave signal
that is processed by the dialysis unit, which has access to other
parameters of the treatment such as blood flow, dialysis flow,
valve sequencing etc. The sound waves can be sonic, subsonic or a
pressure wave emitted into the blood stream. The signals can be of
any suitable frequency, could be a single frequency or multiple
frequencies, it could be continuous, pulsed, modulated in
amplitude, frequency or phase. The acoustic transducer can be
piezoelectric, electromagnetic or any suitable type capable of
converting electrical excitation into pressure waves and/or vice
versa.
[0020] The second access disconnection system can be implemented in
at least three ways. One implementation uses two acoustic
transducers, one coupled to the venous section of the
extracorporeal circuit, while the other is coupled to the arterial
section of the extracorporeal circuit. One of the transducers
transmits an acoustic signal into the blood stream, while the other
transducer receives the signal. If any of the sections becomes
disconnected, the receiver no longer detects the emitted signal,
triggering an alarm. The dual acoustic transducers can each perform
both functions, transmit and receive, making possible an embodiment
in which the dual transducers switch functions with each other.
[0021] A second implementation uses either one acoustic transducer,
doubling as transmitter and receiver, or two transducers, one
dedicated to transmit and the other to receive. Here, both emitter
and receiver are coupled to the venous section of the
extracorporeal circuit. In this implementation the transmitter
sends an acoustic pulse into the blood. The pulse reflects in the
extracorporeal circuit interface producing a signature response.
The system monitors, processes and analyzes the signature of the
echo produced when the venous line is connected and yields a
baseline acoustic signature response. The acoustic signature
response produced when the venous line is disconnected is different
from the stored pattern. Processing of the received signal detects
such change and generates an alarm, pump and/or valve shutdown or
occlusion as desired.
[0022] A third implementation of the second access disconnection
system uses passive sonar. The blood stream in the extracorporeal
circuit is subjected to a series of operations that introduce
acoustic waves into it. Blood pump, drip chamber, interaction with
the dialyzer and the patient each create an acoustic pattern. This
sound pattern constitutes an acoustic signature, e.g., in the
venous line when the needle is lodged, will be different from the
one when it is dislodged. The passive sonar implementation uses an
acoustic transducer coupled to the venous line, which acts as a
receiver. The receiver transducer monitors, processes and analyzes
acoustic signals in the blood to create a baseline acoustic
signature. When the pattern changes due to a venous needle
dislodgement, the processing of the received signal detects this
change and generates an alarm, etc.
[0023] A third access disconnection/blood leak detection system
uses optical sensors. It is not uncommon that a small blood leak is
present around the areas at which the access needles connect to the
patient's arm. This effect, however, should be limited to a small
area around the access points. If the blood leak extends to a
larger area, it likely indicates needle partial or full
dislodgement, which must be addressed immediately.
[0024] The optical system in one embodiment uses a flexible circuit
having distributed optically reflective sensors. Here, flexible
circuit wraps around the arm of the patient in one embodiment. In
another implementation, the optical system incorporates either a
rigid or semi-rigid circuit mounted on a flexible arm band made of
plastic, rubber or cloth, for example. The arm band can also be
disposable. In any case, the attachment mechanism can be sized and
configured to be attached alternatively for blood access with
another body area, such as a patient's leg, or for catheter access,
e.g., in the patient's neck.
[0025] The flexible circuit can be in contact with a piece of gauze
covering the needle recess. For sterility the contact surface is
cleaned with a disinfectant. Alternatively, the contact area is
covered with a sterile disposable transparent film, which can be
self-adhesive. The film is discarded after the treatment is
completed.
[0026] The flexible circuit can be attached to the patient using a
hook and loop type of mechanism, magnetic straps, magnetic buckle
or other type of releasably securable and cleanable apparatus.
[0027] The reflective optical sensors in one embodiment use of a
light emitting diode, such as a light source, and a photocell or
phototransistor, as receiver. The emitted light has a wavelength
that has is chosen so that the color of blood absorbs its energy.
As long as the light illuminates a white gauze, a percentage of the
light's energy is reflected towards the receiver. On the other
hand, if blood on the gauze absorbs most of all of light energy,
the receiver detects a considerable loss of signal and signals or
alarm, etc.
[0028] A local micro-controller in one embodiment gathers data from
the optical sensors and reports this data via, e.g., a radio
frequency link, to the dialysis instrument. In one implementation,
the micro-controller remains in a sleep mode or power-save mode,
which turns the optical sensors off until the dialysis instrument
requests data via the radio frequency link. The micro-controller
then "wakes up", energizes the light sources, reads the optical
receivers and transmits the status back to the dialysis instrument.
If one (or perhaps more than one) of the sensors does not receive
enough light, the processor issues a distress call and,
additionally or alternatively, energizes an audible alarm. The
machine takes any other appropriate action, such as shutting down a
pump or clamping a line or valve.
[0029] In a fourth access disconnection embodiment, the dialysis
system uses the patient's cardiovascular electrical system to
detect an access disconnection. Humans have an internal electrical
system that controls the timing of heartbeats by regulating: heart
rate and heart rhythm. Generally, the body's electrical system
maintains a steady heart rate of sixty to one hundred beats per
minute at rest. The heart's electrical system also increases this
rate to meet the body's needs during physical activity and lowers
it during sleep.
[0030] In particular, the heart's electrical system controls the
timing of the body's heartbeat by sending an electrical signal
through cells in the heart, namely, conducting cells that carry the
heart's electrical signal and muscle cells that enable the heart's
chambers to contract. The generated electrical signal travels
through a network of conducting cell pathways by means of a
reaction that allows each cell to activate the one next to it,
passing along the electrical signal in an orderly manner. As cell
after cell rapidly transmits the electrical charge, the entire
heart contracts in one coordinated motion, creating a
heartbeat.
[0031] The system of the present disclosure uses an
electrocardiogram or electrogram ("ECG") setup. In one
implementation, a first electrode is attached to the venous line
and a second electrode is attached to the patient. The electrodes
are connected electrically to signal conditioning circuitry. The
signal conditioning circuitry produces ECG signals when the
arterial and venous connections are made properly. When a partial
or complete access disconnection occurs with either the arterial or
venous needles, electrical communication with the body's electrical
system through the extracorporeal path is lost as is the ECG
signal. Additional circuitry detects this dropout and sends an
access disconnection signal to the blood treatment machine.
[0032] Alternative ECG embodiments include the attachment of both
first and second electrodes to the extracorporeal circuit. Also,
blood access can be made at or close to the patient's heart,
increasing sensitivity to the ECG signals, as opposed to access at
the patient's arm. To that end, disclosed herein is an embodiment
for a dialysis needle equipped with the electrodes used for
accessing the patient's blood at or near the heart. Also disclosed
herein are various embodiments for tubing having electrodes
implanted either inside the tubing, within the tubing or outside
the tubing. Depending on the electrode configuration, the
electrodes communicate electrically with the blood directly,
capacitively, inductively, or wirelessly, e.g., through radio
frequency.
[0033] The ECG system is also adaptable for other uses besides the
detection of vascular access disconnection. The ECG signals may be
further processed to calculate other physiological parameters such
as heart rate variability, respiration, stroke volume, cardiac
output and central blood volume. To this end, an electrical source
can be added to the ECG system to measure bioimpedance. Further, a
solution can be injected into the patient's body to assist in one
or more of the above parameters. The ECG system can also be used to
assist control of patients with heart rhythm management devices
(pacemakers) via cardiac electrophysiology measurements to change
cardiovascular parameters beneficially during dialysis.
[0034] In a fifth system, a blood leak device using capacitive
sensors is provided. The device includes outer layers of
insulation, e.g., plastic layers. Inside, the device includes an
array of capacitors. A layer of shielding is also provided inside
the shielding. If a blood leak develops beneath the capacitive
device, the region of capacitors sensing a dielectric change grows.
If the region stops growing, a system using the capacitive device
assumes a normal amount of seepage has occurred, which is
distinguishable from a blood leak or needle dislodgement. If the
blood leak grows large enough, the system using the capacitive
device assumes that a partial or full access disconnection has
occurred and causes an alarm.
[0035] In any of the above described access disconnection
embodiments, the circuitry for the access disconnection systems can
be located locally at the patient or sensing site, remotely within
the machine, or some combination thereof. Depending on the location
of the circuitry, the signal sent from the access disconnection
system to the dialysis machine can be a steady, e.g., conditioned
digital signal, an intermittent signal, a signal sent on command or
some combination thereof. The signal can be sent via wires or
wirelessly.
[0036] Further, any of the above described access
disconnection/blood leak detection embodiments can be used
alternatively in a redundant system with another, different type of
access disconnection/blood leak system. For example, any system
that looks for an electrical connection to be broken (described
loosely as an access disconnection system for ease of description
but in know way intending to limit the meaning of the term) can be
combined with a system that looks for an electrical connection to
be made (described loosely as a blood leak detection system for
ease of description but in know way intending to limit the meaning
of the term) to capitalize on benefits inherent with each type of
system.
[0037] It is therefore an advantage of the present disclosure to
provide an improved access disconnection system for blood treatment
machines.
[0038] It is another advantage of the present disclosure to provide
non-invasive access disconnection systems.
[0039] It is a further advantage of the present disclosure to
provide access disconnection systems that do not induce current
into the patient's blood.
[0040] It is still another advantage of the present disclosure to
provide access disconnection systems that do not add to disposable
cost or manufacture.
[0041] It is still a further advantage of the present disclosure to
provide access disconnection systems that circumvent problems from
to electrical reconnection due to lost blood.
[0042] It is yet another advantage of the present disclosure to
provide an access disconnection system that yields other valuable
blood parameter information.
[0043] It is yet a further advantage of the present disclosure to
provide access disconnection systems that are compatible with blood
needle and catheter applications.
[0044] Additional features and advantages are described herein, and
will be apparent from, the following Detailed Description and the
figures.
BRIEF DESCRIPTION OF THE FIGURES
[0045] FIG. 1 illustrates a known arterial and venous access
configuration.
[0046] FIG. 2 is a sectioned elevation view showing one embodiment
of an access disconnection system using ultrasound.
[0047] FIG. 3 is a perspective view showing the system of FIG. 2
and one embodiment for it to communicate with a blood treatment
machine.
[0048] FIG. 4 is a schematic view of one embodiment of the
electronics associated with the system of FIG. 2.
[0049] FIG. 5 is a schematic view of one simulation of the
ultrasound access disconnection system of FIG. 2.
[0050] FIG. 6 is a chart illustrating results from testing done on
the simulation of FIG. 5.
[0051] FIG. 7 is a perspective view showing one embodiment of an
acoustic access disconnection system, which employs two acoustic
transducers.
[0052] FIG. 8 is a perspective view showing an additional
embodiment of an acoustic access disconnection system, which
employs active sonar, and which is system is depicted in a transmit
phase.
[0053] FIG. 9 is a perspective view showing either (i) a receive
phase of the active sonar system of FIG. 8 or (ii) an alternative
embodiment employing a passive sonar system, wherein both systems
"listen" to either (i) an echo of the active transmitted signal or
(ii) the acoustic signature of the extracorporeal circuit in the
passive system.
[0054] FIG. 10 is a perspective view showing one embodiment of an
optical access disconnection system.
[0055] FIG. 11 is a perspective view showing one embodiment of a
flexible circuit used with the optical access disconnection system
of FIG. 10.
[0056] FIG. 12 is a schematic elevation view representing the
optical access disconnection system of FIG. 10 in a normal
state.
[0057] FIG. 13 is a schematic elevation view representing the
optical access disconnection system of FIG. 10 in an access
disconnection state.
[0058] FIG. 14 is a perspective view showing the optical system of
FIG. 10 and one embodiment for it to communicate with a blood
treatment machine.
[0059] FIG. 15 is a schematic view of one embodiment of a system
that uses electrocardiogram ("ECG") signals to detect an access
disconnection.
[0060] FIG. 16 is a schematic view of another embodiment of a
system that uses electrocardiogram ("ECG") signals to detect an
access disconnection.
[0061] FIG. 17 is a plan view of one embodiment for a cardiac
catheter used with the ECG system of FIG. 16.
[0062] FIGS. 18A to 18C illustrate various embodiments for coupling
an electrical contact with the patient's blood, the embodiments
capable of being used with the systems of FIGS. 16 and 17.
[0063] FIGS. 19A and 19B are top and side views of a capacitive
sensing blood leak detection device.
DETAILED DESCRIPTION
[0064] The examples described herein are applicable to any medical
fluid therapy system requiring vascular access. The examples are
particularly well suited for the control of kidney failure
therapies, such as all forms of hemodialysis ("HD"), hemofiltration
("HF"), hemodiafiltration ("HDF") and continuous renal replacement
therapies ("CRRT") requiring vascular access.
Ultrasound Remote Access Disconnection Sensor
[0065] Referring now to the drawings and in particular to FIGS. 2
to 4, an ultrasound access disconnection system 10 is illustrated.
FIG. 2 shows the details of system 10. FIG. 3 shows one apparatus
for attaching system 10 to patient 12. FIG. 3 also shows one
embodiment for interfacing system 10 with blood treatment or
dialysis machine 100. While system 10 refers generally to the
remote apparatus connected to the patient as seen in FIG. 2, system
10 and indeed each of the systems described herein also includes
the machine or instrument, such as a dialysis machine. FIG. 4 shows
an embodiment of the electronics (either onboard or remote
electronics) associated with system 10. FIGS. 5 and 6 provide test
results.
[0066] Any of the vascular disconnection examples described herein,
including system 10, is operable with machine 100, which can
include a diffusion membrane or filter, such as a dialyzer, e.g.,
for HD or HDF, or a hemofiliter, e.g., for HF. Moreover, machine
100 and any of the access disconnection systems described herein
may be used in clinical or home settings. For example, machine 100
and the access disconnection systems may be employed in an
in-center HD machine, which runs virtually continuously throughout
the day. Alternatively, they may be used in a home HD machine,
which can for example be run at night while the patient is
sleeping.
[0067] Machine 100 in one embodiment has a dialysate (infusate)
supply. Alternatively, multiple bags of dialysate supply are ganged
together and used one after another. In such a case, the emptied
supply bags can serve as drain or spent fluid bags. Further
alternatively, machine 100 can be used with an on-line source, such
as one or more concentrate pump configured to combine one or more
concentrate with water to form dialysate on-line. On-line sources
are used commonly with HD systems for example.
[0068] Although not illustrated, machine 100 can operate with an
in-line or batch heater that heats the dialysate or infusate to a
desired temperature. The heater can be located upstream or
downstream of a fresh supply pump for example. Machine 100 includes
a dialysate air trap, which can be located at or near the heater to
capture air egression from the dialysate due to heating. Likewise,
the extracorporeal circuit operable with blood pump 102 also
includes one or more air detector and air removal apparatus (e.g.,
air trap).
[0069] HD, HF, HDF or CRRT machine 100 also includes blood pumping
systems, shown below, which are known generally in the art, e.g.,
the use of one or more peristaltic blood pump. HD, HF, HDF or CRRT
machine 100 also includes dialysate proportioning systems,
mentioned above, which are also known and need not be described
here. The '534 patent, incorporated herein by reference, describes
a proportioning system for example.
[0070] Machine 100 also includes an apparatus and method for
knowing how much dialysate has been used for clearance and how much
ultrafiltration volume has been removed. This apparatus controls
and knows how much ultrafiltrate has been removed from the patient
and controls the flowrate of dialysate to and from the dialyzer,
extracorporeal circuit and/or hemofilter. The apparatus also
ensures that the necessary amount of ultrafiltrate is removed from
the patient by the end of treatment.
[0071] Machine 100 includes an enclosure 104 as seen in FIG. 3.
Enclosure 104 varies depending on the type of treatment, whether
the treatment is in-center or a home treatment, and whether the
dialysate/infusate supply is a batch-type (e.g., bagged) or
on-line. An in-center, on-line enclosure 104 tends to be bigger and
more robust due to the additional dialysate producing equipment and
the frequency of use of such machines. A home therapy enclosure 104
is desirably smaller and built so that machine 100 can be moved
about one's home or for travel.
[0072] FIG. 2 illustrates that system 10 includes a transducer 24.
Transducer 24 in the illustrated embodiment includes a housing 26,
which houses a piezoelectric crystal 28. Transducer 24 transmits
power from one type of system to another. In the piezoelectric
embodiment, transducer 24 power is provided in the form of
electricity from a piezoelectric material acted upon. System 10
includes a transducer excitation apparatus 42 as seen in FIG. 4,
which applies an electrical field to piezoelectric crystal 28.
Piezoelectric crystal 28 undergoes mechanical deformation due to
the electric field. In this manner, crystal 28 is induced to
resonate (vibrate) at a certain frequency to produce ultrasonic
waves. In an embodiment, the ultrasonic waves are produced in the
Mega-Hertz frequency range. A layer of gel couples the waves to the
patient in one embodiment. The ultrasound waves in the presence of
human tissue travel through the tissue to a depth that depends on
the power and frequency of the excitation.
[0073] Housing 26 of transducer 24 in the illustrated embodiment is
positioned in parallel with the arm and tissue of patient 12.
Crystal 28 on the other hand is placed at an angle, e.g.,
forty-five degrees, relative to the arm and tissue of patient 12 to
produce ultrasound waves 30a having directional components both
aligned with and perpendicular to the direction of blood flow.
[0074] Blood cells 32, e.g., red blood cells, within the blood
stream serve as reflectors for the ultrasound waves, echoing waves
30b back towards a second piezoelectric crystal 34. It should be
appreciated however that first piezoelectric crystal 28 could
perform both emitter and receiver functions, in which case second
crystal 34 is not needed. In the illustrated embodiment, receiver
crystal 34 is located in the same housing 26 of the same transducer
24 as is emitter crystal 28. Alternatively, receiver crystal 34 is
located in a separate transducer housing. In the illustrated
embodiment, receiver crystal 34 is also mounted at an angle, e.g.,
forty-five degrees, relative to the arm and tissue of patient
12.
[0075] For receiver piezoelectric crystal 34, reflected waves 30b
apply mechanical stress to receiver crystal 34, causing crystal 34
to become electrically charged and to vibrate at its resonant
frequency creating an ultrasound wave. The reflected ultrasound
waves 30b have a different frequency than do the emitted ultrasound
waves 30a, an effect known as the Doppler effect. The change in
frequency is dependent on the speed and direction of movement of
blood cells 32 flowing though the access site. The electronics in
system 10 stores software that processes the received echoes 30b to
determine blood parameters, such as, blood flowrate of the red
blood cells, peak flowrate of the reflectors, changes in blood
flowrate, e.g., pulsatile characteristics of the blood flow,
turbulence in the access line as described in more detail
below.
[0076] In the embodiment illustrated in FIG. 3, transducer 24 and
the electronics described below are held in place via bands 36.
Bands 36 have suitable fasteners, such as Velcro.TM. fasteners or
other type of frictionally engaging fastener, buttoned or
snap-fitted fastener. Bands 36 serve a second function, namely,
FIG. 2 shows that band 36 holds transducer 24 against patient 12
via a gel 38. Gel 38 couples the ultrasound wave into the patient's
tissue.
[0077] FIG. 4 shows an embodiment of the electronics associated
with system 10. A digital signal processor ("DSP") 44, which can
include onboard random access memory ("RAM") and read only memory
("ROM"), sends an output signal to transducer excitation appratus
42. Excitation apparatus 42 excites emitter crystal 28 of
transducer 24 as described above. Reflected waves 30b cause
receiver crystal 34 (or crystal 28 operating as both emitter and
receiver) to vibrate and create an ultrasound wave, which is sent
to signal conditioning 40. Signal conditioning 40 in one embodiment
includes an analog to digital ("A/D") converter, which digitizes
the reflected wave into a form that DSP 44 can process. Signal
conditioning 40 may, in another embodiment, contain demodulation
circuitry to separate the signal components in a manner useful for
Doppler calculations, for example.
[0078] DSP using onboard software in one embodiment detects a flow
or access condition, a no-flow or full-access disconnection
condition or a partial-flow or partial access diconnection
condition. DSP 44 also uses the conditioned signals to detect blood
flowrate, e.g., by equating a particular frequency to a particular
blood flowrate. The correlation can be determined empirically and
checked for repeatability. A peak frequency corresponds to peak
blood flowrate. DSP 44 also detects changes in blood flowrate even
when they do not rise to the level indicating an access
disconnection. This information can be used to determine blood flow
turbulence for example, which in turn can be used for example
diagnostically to monitor or determine therapy efficiency or
effectiveness.
[0079] DSP 44 communicates back and forth with a remote or wireless
emitter/receiver 46, such as a radio frequency ("RF")
emitter/receiver. Other remote signals may be used alternatively,
such as a microwave signal. Further alternatively, system 10 is
hard-wired to machine 100 and communicates via electrical signals,
e.g., 4 to 20 mA or 0 to 5 VDC signals.
[0080] Machine 100 includes a wireless transmitter/receiver 48,
such as an RF transceiver. In system 10, communicator 48 instrument
100 sends messages to and receives messages from the remote unit
via communicator 46. Communicator 48 in turn communicates back and
forth with a central processing unit ("CPU") 50 located within 100.
CPU 50 in an embodiment includes a supervisory processor that
communicates via signals 56 with one or more delegate processor and
circuit board or controller located within machine 100. Transducer
24, signal conditioning 40, excitation apparatus 42, DSP 44 and
emitter 46 are located on a printed circuit board ("PCB") 52 in the
illustrated embodiment. PCB 52 can be located within transducer
housing 26, within a separate housing (not illustrated), or within
a housing that also houses one or more transducer 24. In an
alternative embodiment, DSP 44 and its associated functionality are
located and performed, respectively, at CPU 50 of machine 100.
[0081] PCB 52 also includes a battery, a power supply or a
combination of both, referred to generally herein as power supply
54. Supply 54 can be a rechargeable battery, for example. Supply 54
powers the components of PCB 52, such as, signal conditioning, DSP
44 and wireless communicator 46. Power supply 54 is rechargeable in
an embodiment and can be coupled to an audio, visual or audiovisual
alarm that alerts the patient when the power supply needs to be
recharged or replaced.
[0082] In the embodiment illustrated in FIG. 4, remote wireless
communicator or transceiver 46 communicates with instrument
communicator 48 via an RF signal 58. Signal 58 can be any of the
following types: an electrical signal, a radio frequency signal, a
microwave signal, a continuous signal, an intermittent signal, a
signal sent only upon the sensing of the change and any suitable
combination thereof. FIG. 3 shows that in an embodiment signal 58
is a continuous e.g., digitalized, data stream, which CPU 50 (via
RAM 42 and DSP 44 and associated functions located in machine 100)
uses to determine blood flowrate, peak flowrate, pulsatile
characteristics of the blood flow, turbulence and the like. If an
access disconnection occurs, the frequency of reflected ultrasonic
waves 30b changes significantly enough as does the output of
corresponding signal 58 that the software within buffering RAM 42
detects a partial or full access disconnection. When the access
disconnection is detected, CPU 50 via signals 56 causes other
components within machine 100 to take appropriate action, e.g.,
causes an audio, visual or audiovisual alarm to appear on and/or be
sounded from graphical user interface 106 of machine 100. CPU also
likely causes blood pump 102 to shut down.
[0083] In an alternative embodiment, the processing of reflected
waves 30b is done on PCB 52. Here, onboard DSP 44 determines blood
flowrate, peak flowrate, pulsatile characteristics of the blood
flow, turbulence and the like. DSP 44 sends this information
wirelessly via transceiver 46 to CPU 50 at predetermined intervals
or when CPU 50 requests such information. When an access
disconnection is detected, DSP via transceiver 46 sends an alarm
signal 58 to CPU 50, which causes other components within
instrument 100 to take appropriate action as described above. Thus
wireless signal 58 can be a continuous signal, an intermittent
signal or a signal sent only upon the sensing of the change and any
suitable combination thereof.
[0084] In a further alternative embodiment, PCB 52 includes an
audio, visual or audiovisual alarm, which alarms a patient of an
access disconnection. In this embodiment, system 10 may or may not
communicate with machine 100. For example, PCB 52 can sound an
alarm, while machine 100 shuts down one or more pump and occludes
or closes one or more line or valve.
[0085] FIG. 5 illustrates schematically a test that has been
performed using an ultrasound sensor, such as transducer 24 shown
in FIG. 2, placed at the blood vessel of patient 12 downstream from
venous needle 20 as also seen in FIG. 2. It should be appreciated
that the systems described herein are opeable with standard access
needles 16 and 20 or with subclavian type catheters. As seen in
FIG. 5, the patient's arm is modeled by a tube. The ultrasound
sensor is placed over the tube. The patient's blood is modeled
using saline, which an access pump pumps at approximately one liter
per minute through a five hundred cubic centimeter compliance
chamber, through tube (modeling the patient) and back into a source
of the saline. Arterial and venous needles 16 and 20 shown
schemtically in FIG. 5 are inserted or connected to the tube
representing the patient's arm. The simulated extracorporeal
circuit includes a blood pump, drip chamber, in combination with a
pressure sensor, dialyzer and venous side pressure sensor.
[0086] FIG. 6 illustrates that when the venous access 20 was
disloged from the tube, the ultrasound sensor noticed a discernable
drop in flowrate of about 300 ml per minute. That is, the one liter
per minute being pumped by the access pump in FIG. 5 returned at
only 700 ml per minute as sensed by the ultrasound sensor.
Acoustic Access Disconnection Sensor
[0087] Referring now to FIGS. 7 to 9, various embodiments for
acoustic access disconnection systems are illustrated by systems
60a to 60c (referred to herein collectively as acoustic access
disconnection systems 60 or generally as acoustic access
disconnection system 60). Access disconnection systems 60 have many
similarities with ultrasound access disconnection system 10. Both
are used with machine 100 (and each of its alternative
configurations discussed above), have remote signaling capability,
are non-invasive, do not circulate current through the patient's
blood, do not add components to the disposable cassette or tubing
set, saving cost, and have additional blood parameter measurement
capability. Both systems 10 and 60 use sound waves.
[0088] One primary difference with systems 60 is that the
transducers and associated electronics are coupled to the arterial
and venous lines 14 and 18 instead of to patient 12. This
configuration may be advantageous from the standpoint that a
disconnection of one of the lines 14 and 18 should produce a
relatively dramatic change in reflected waves. Additional blood
parameter measurements will reflect blood flow characteristics in
the extracorporeal circuit rather than blood flow characteristics
in the patient as with system 10, which may be advantageous or
disadvantageous.
[0089] Referring now to FIG. 7, a dual transducer transmit/receive
acoustic access system 60a is illustrated. Acoustic access system
60a includes a printed circuit board 66, which carries transducers
62 and 64, signal conditioning 40, excitation apparatus 42, DSP 44
(including onboard memory) wireless transceiver 46 and power supply
54 described above. Power supply 54 as above powers excitation
apparatus 42, DSP 44 and wireless transceiver 46, which operate as
described above for system 10. DSP 44 communicates back and forth
with remote transceiver 46, which communicates back and forth with
machine transceiver 48. In an alternative embodiment, as with
system 10 above, one or more of the apparatus and associated
functionality of DSP 44 is located within machine 100. Machine 100
as before inlcudes wireless, e.g., RF transceiver 48 to send and to
receive signals 58 to and from wireless transceiver 46.
Alternaitvely, machine 100 is hardwired to system 60a for
electrical communication.
[0090] In the illustrated embodiment, acoustic emitter transducer
62 through excitation apparatus 42 transmits an acoustical signal
into arterial line 14, while receiver transducer 64 receives an
acoustical signal from venous line 18. Alternatively, emitter
transducer 62 transmits an acoustical signal into venous line 18,
while receiver transducer 64 receives an acoustical signal from
arterial line 14. Tranducers 62 and 64 can be of a type in which
each is constructed to be one of an emitter or a receiver.
Alternatively, tranducers 62 and 64 are each both transmitters and
receivers. Here, the roles of tranducers 62 and 64 upon an access
disconnection event can be reversed to provide a redundant check.
The roles of tranducers 62 and 64 can also be switched under normal
operation to test that the transducers are working properly and
also to provide redundancy for other parameters for which system
60a detects.
[0091] In an embodiment, tranducers 62 and 64 transmit and receive
waves that are sonic, subsonic or pressure waves, for example, the
signal can be sent in a single or in multiple frequencies.
Transducer 62 can emit waves in a continuous, intermittent or
pulsed manner. Further, the emitted signal can be modulated in any
one or more combination of amplitude, frequencty or phase. In a
preferred embodiment, the signal is distinct from naturally
occurring waves that receiver transducer 64 may also detect.
[0092] Excitation apparatus 42 excites acoustic emitter transducer
62 to emit sound waves in a direction towards patient 12. Acoustic
receiver transducer 64 is likewise configured to receive sound
waves from the patient. In this manner, the likelihood that sound
waves will travel from emitter transducer 62, around blood pump
102, to receiver transducer 64 is minimized. Further, a drip
chamber located in one or both of the arterial or venous lines
provides an air barrier disconnect within the extracorporeal
circuit, which should minimize sound wave coupling towards the
blood pump. This directional configuration also maximizes the
difference in signal reception when an access disconnection.
[0093] Signal conditioning 40 (e.g., an A/D converter) conditions
the signal for DSP 44. It should be appreciated that the signal
conditioning can be located alternatively within DSP 44. DSP 44
processes the conditioned signals using an onboard or a separate
buffering RAM. DSP connunciates with transceiver 46, which in turn
sends and receives data from instrument transceiver 48. Transceiver
46 can alternatively be located onboard DSP 44. In any case, DSP 44
can be configured to detect a dislodgement by measuring a loss in
power of the acoustic signal during disconnection. DSP 44 could
also calculate blood flowrate, peak flowrate and any of the other
parameters discussed herein.
[0094] If either arterial line 14 or venous line 18 becomes
partially or completely disloged from patient 12, communication
between tranducers 62 and 64 is broken or altered significantly
enough that an access disconnection determination is made and any
of the protective actions discussed herein, e.g., alarm, pump
shutdown, valve closing, line occluding is carried out. In the
illustrated embodiment, the processing of the breaking or
interruption of communication between tranducers 62 and 64 is done
on PCB 66. Here, under normal operation, PCB 66 determines the
power and frequency of the received signal, and potentially, blood
flowrate, peak flowrate, pulsatile characteristics of the blood
flow, turbulence and the like as described above. This information
is sent wirelessly via transceiver 46 to CPU 50 of instrument 100
on a continuous basis, at predetermined intervals, or when CPU 50
requests such information. When an access disconnection is
detected, DSP via emitter 46 sends an alarm signal 58 to CPU 50,
which causes other components within machine 100 to take
appropriate action as described above. The wireless signal 58 can
accordingly be a continuous signal, an intermittent signal, a
signal sent only upon the sensing of the change and any suitable
combination thereof.
[0095] In an alternative embodiment, the various components of PCB
66 are provided in machine 100 such as DSP 44. Here, the RF signal
58 is a continuous data stream, which can be conditioned e.g.,
digitized, locally and sent to CPU 50 of machine 100. DSP 44 now
within instrument 100 uses data stream 58 to determine the power
and frequency of the received signal, and potentially, blood
flowrate, peak flowrate, pulsatile characteristics of the blood
flow, turbulence and the like within machine 100. If an access
disconnection occurs, the data contained in the RF signal 58
changes enough so that the software within instrument 100 detects a
partial or full access disconnection. When the access disconnection
is detected, CPU 50 causes, e.g., through a delegate controller,
other components within machine 100 to take appropriate protective
action as described above.
[0096] In a further alternative embodiment, PCB 66 includes an
audio, visual or audiovisual alarm, which alarms a patient of an
access disconnection. In this embodiment, system 10 may or may not
communicate with machine 100.
[0097] Referring now to FIGS. 8 and 9, an active sonar or echo
system 60b employs either a single acoustic transducer 68, doubling
as transmitter and receiver (as illustrated), or dual transducers,
one emmitting and one receiving. In either case, the single or dual
transducers are coupled to a single one of the extracorporeal
lines, e.g, venous line 18 in one preferred embodiment (as
described above venous access dislodgmenent is potentially more
dangerous than arterial access dislosdgement).
[0098] Active sonar or echo system 60b includes a printed circuit
board 70, which carries signal conditioning 40, excitation
apparatus 42, DSP 44, wireless remote transceiver 46 and power
supply 54 described above. Power supply 54 powers signal
conditioning 40, DSP 44 and transceiver 46. In an alternative
embodiment, as with system 10 above, one DSP 44 is located within
machine 100. Machine 100 as before inlcudes wireless, e.g., RF,
transceiver 48 to receive signals from RF emitter 46.
Alternatively, machine 100 is hardwired to system 60b for
electrical communiucation.
[0099] In the illustrated embodiment, acoustic emitter transducer
68 transmits an acoustical signal into the blood of venous line 18.
The signal reflects in the extracorporeal circuit lines 14, 18 and
graft 22, producing a signature response. Signal conditioning 40
processes the signalure response, e.g., digitizes it, and sends a
digital signal to DSP 44 (which can include RAM, ROM, onboard
signal conditioning and/or onboard transceiver) located either
locally at PCB 70 or at machine 100. DSP 44 analyzes the signal
using onboard software in one embodiment. DSP 44 formulates a
baseline acoustic signature of the reflected acoustical wave and
stores such baseline signal in RAM 42.
[0100] Acoustic emitter/receiver transducer 68 is configured to
emit sound waves in a direction towards patient 12. Transducer 68
is likewise configured to receive sound waves from the patient. The
likelihood that sound waves will travel from transducer 68, around
blood pump 102, back to transducer 68 is minimal due at least in
part to a drip chamber that is located between the transducer and
the blood pump in the arterial blood line. This directional
configuration also maximizes the difference in signal reception
when an access disconnection occurs.
[0101] If either arterial line 14 or venous line 18 becomes
partially or completely disloged from patient 12, the signature
response back to tranducer 68 is broken or altered significantly
enough compared to the baseline acoustic signature, that an access
disconnection determination is made and any of the actions
discussed herein is performed, e.g., alarm, pump shutdown, valve
closing, line occluding.
[0102] In the illustrated embodiment, the processing of the
difference between the received response and the baseline response
is done at PCB 70. Here, under normal operation, onboard DSP 44
determines the power, frequency and shape of the envelope of the
received signal, and potentially, blood flowrate, peak flowrate,
pulsatile characteristics of the blood flow, turbulence and the
like. This information is sent wirelessly via DSP 44 and
communicator 46 to CPU 50 continuously, at predetermined intervals,
or when CPU 50 requests such information. When an access
disconnection is detected, DSP 44 via communicator 46 sends an
alarm signal to CPU 50, which causes other components within
machine 100 to take appropriate action as described above. The
wireless signal can accordingly be a continuous signal, an
intermittent signal, a signal sent only upon the sensing of the
change and any suitable combination thereof.
[0103] In an alternative embodiment, the majority of the components
of PCB 70 are provided in machine 100. Here, the RF signal 58 is a
continuous data stream, which can be conditioned, e.g., digitized,
locally and sent to the CPU of machine 100, which operates with DSP
44 and their associated functions. Data stream 58 is used to
determine blood flowrate, peak flowrate, pulsatile characteristics
of the blood flow, turbulence and the like within machine 100. If
an access disconnection occurs, the RF signal 58 is interrupted or
is otherwise reduced enough that the software within buffering DSP
44 detects a partial or full access disconnection. When the access
disconnection is detected, CPU 50 causes other components within
machine 100 to take appropriate action as described herein.
[0104] In a further alternative embodiment, PCB 70 includes an
audio, visual or audiovisual alarm, which alarms a patient of an
access disconnection. In this embodiment, system 10 may or may not
communicate with machine 100.
[0105] Referring again to FIG. 9, a passive sonar or acoustic
signature system 60c employs a single receiver transducer 64.
Transducer 64 is coupled to a single one of the extracorporeal
lines, e.g, venous line 18 in one preferred embodiment (as
described above venous access dislodgmenent is potentially more
dangerous than an arterial access dislodgement).
[0106] Passive sonar or acoustic signature system 60c includes
printed circuit board 70, which carries signal conditioning 40,
excitation apparatus 42, DSP 44, wireless communicator 46 and power
supply 54 described above. In an alternative embodiment, as with
the systems above, one or more of the apparatuses and associated
functionality of DSP 44 is located within machine 100.
[0107] Passive sonar system 60c uses pulses generated by the
system's blood pump, drip chamber, interaction with the dialyzer or
other extracorporeal device. These devices create an acousitcal
pattern or signature response at receiver transducer 64, similar to
the signature response discussed above. Signal conditioning 40
processes the signalure response, e.g., digitalizes it, and sends a
digital signal to DSP 44, located either locally at PCB 70 or at
machine 100. DSP 44 analyzes the signal using onboard software in
one embodiment. DSP 44 formulates a baseline acoustic signature of
the reflected acoustical wave and stores such baseline signal in
memory.
[0108] If in the illustrated embodiment, venous line 18 becomes
partially or completely disloged from patient 12, the signature
response back to tranducer 68 is broken or altered significantly
enough compared to the baseline acoustic signature, that an access
disconnection determination is made. Any of the actions discussed
herein is then performed, e.g., alarm, pump shutdown, valve
closing, line occluding is carried out.
[0109] In the illustrated embodiment, the processing of the
difference between the received response and the baseline response
is done on PCB 70 of system 60c. Here again, under normal
operation, onboard DSP 44 determines blood flowrate, peak flowrate,
pulsatile characteristics of the blood flow, turbulence and the
like. This information is sent wirelessly via DSP 44 and
transceiver 46 to CPU 50 continuously, at predetermined intervals,
or when CPU 50 requests such information. When an access
disconnection is detected, DSP via transceiver 46 sends an alarm
signal to CPU 50, which causes other components within machine 100
to take appropriate action as described herein.
[0110] In an alternative embodiment, DSP 44 is provided in machine
100. Here, the RF signal 58 is a continuous data stream, which can
be conditioned, e.g., digitized, locally and sent to the CPU of
machine 100 via RF communication. Again, data stream 58 can be used
to determine blood flowrate, peak flowrate, pulsatile
characteristics of the blood flow, turbulence and the like within
machine 100. If an access disconnection occurs, the RF signal 58 is
interrupted or is otherwise reduced enough that the software within
buffering DSP 44 detects a partial or full access disconnection.
When an access disconnection is detected, CPU 50 causes, e.g., via
a delegate controller, other components within machine 100 to take
appropriate protective action as described above.
[0111] In a further alternative embodiment, PCB 70 of system 60c
includes an audio, visual or audiovisual alarm, which alarms a
patient of an access disconnection. In this embodiment, system 10
may or may not communicate with machine 100.
Optical Access Disconnection/Blood Leak Detector
[0112] Referring now to FIGS. 10 to 14, an embodiment of an optical
access disconnection/blood leak detection system 80 is illustrated.
Optical access disconnection/blood leak detection system 80 takes
advantage of the gauze that is normally applied to patient 12 over
access needles 16 and 20. It is not uncommon that under normal
operation a small leak is present around the access points in which
needles 16 and 20 connect to patient's arm 12. The normal blood
leakage however should be limited to a small area around access
needles 16 and 20. If the blood leak extends to a larger area, it
likely indicates a needle dislodgement that needs to be addressed
immediately.
[0113] FIG. 10 illustrates that optical access disconnection/blood
leak detection system 80 provides a flexible circuit 90. Flexible
circuit 90 wraps around arm 12 of the patient. In an embodiment,
flexible circuit 90 is placed over the gauze pad 82 shown in FIG.
10, which as mentioned is placed over access needles 16 and 20.
Because the flex circuit 90 contacts gauze 82, sterility needs to
be considered. In one embodiment, flexible circuit 90 is cleaned
with a disinfectant prior to being placed over gauze 82. In an
alternative embodiment, gauze 82 is covered with a sterile
disposable film 84, which can be self-adhesive. Here, film 84 is
discarded after treatment is completed. Film 84, isolates flexible
circuit 90 from the contact area.
[0114] Arm band system 90 provides preventive action against needle
dislodgement. By wrapping around the needles and tubing, flexible
circuit 90 secures the needles and tubing in position and
accordingly tends to prevent dislodgement. Arm band system 90
confines the connections between the fistulas and associated tubing
to an area covered by flexible circuit 90, so that the system can
also detect a disconnection between the fistula and the tubing.
[0115] FIG. 11 illustrates that flexible circuit 90 in one
embodiment includes hooks 86a to 86c, which loop around flex
circuit 90 and attach, e.g., frictionally and/or adhesively, to
mating pads 88a to 88c, respectively. For example, hooks 86
(referring collectively to hooks 86a to 86c) can attach to pads 88
(referring collectively to pads 88a to 88c) via a Velcro.TM. type
attachment, buttons, slits, folds or other types of releasibly
secureable mechanisms. If it is found that hooks 86 and pads 88 are
dificult to clean, they can be replaced in one embodiment with a
more hygenic attach mechanism, such as magnetic straps and
buckles.
[0116] As seen in FIGS. 10 and 11, flexible circuit 90 includes a
plurality of reflective photo sensors 92a to 92e, which are each
powered via leads 94a to 94e, respectively, connecting to a power
source 54, such as a coin battery. Optical sensors 92 (referring
collectively to sensors 92a to 92e) in an embodiment include a
light emitting diode ("LED") acting as the light source, and a
photocell or phototransistor, acting as a light receiver. The LED
and photosensor are configured for a specific wavelength that
allows maximum absorption when reflected in blood. LED/Photosensor
combinations such as ones used in hemodialysis blood leak detectors
have been used successfully in a prototype of optical system
80.
[0117] Leads 94 (referring collectively to leads 94a to 94d) in an
embodiment are trace, e.g., copper traces, that are applied in a
known process to flexible circuit 90. In an embodiment, flexible
circuit 90 uses an electrically insulative material, such as a
polyamide or Kapton.TM. film 96. Film 96 in an embodiment is
provided in multiple plies, with leads 94 and photosensors 92
sandwiched between the multiple pliers 96.
[0118] Power supply 54 in an embodiment is also sandwiched between
the multiple dielectric films 96. Power supply 54 in one embodiment
also powers a microcontroller 98, which can include any one or more
of signal conditioning 40, RAM 52, DSP 44 and RF emitter 46
described previously herein. Microcontroller 98 can also include an
audible alarm and/or a video status indicator, such as an LED,
which signals whether electronics of optical access
disconnection/blood leak detection system 80 are performing
properly.
[0119] FIGS. 12 and 13 illustrate one embodiment for operating
photoelectric system 80. In an embodiment, light emitted from the
LED of photosensor 92 has a wave length for example in the range of
the blue to green of the ultraviolet wave spectrum, which is
absorbed by the color of blood collected on gauze 82. When light
from sensor 92 illuminates non-bloodied or white gauze 82 shown in
FIG. 12, a percentage of its energy reflects towards a receiver,
e.g., photocell or phototransister, of photosensor 92. In FIG. 13
on the other hand, the presence of blood on gauze 82 absorbs most
of all light energy emitted from sensor 92, such that sensor 92
receives and detects considerably less light, e.g., a loss of
signal. Accordingly, in FIG. 13 the arrow from gauze 82 back to
photosensor 92 indicating reflected light is not shown.
[0120] In the embodiment illustrated in FIG. 11, sensors 92a to 92e
are spaced a relatively far distance from access needles 16 and 20,
e.g., on the order of one inch to three inches from the needles,
such that if blood reaches sensors 92, it has traveled a distance
sufficient from the access points to signal an access disconnection
rather than a normal amount of blood leakage. Further, using
multiple sensors 92a to 92e allows redundency to be built into the
software, in which for example the software looks for multiple ones
of sensors 92 to show a lack of reflection before determining that
an access disconnection has occurred. Alternatively, a single
sensor 92 sensing blood can be taken to indicate an access
disconnection.
[0121] In one implementation, two or more concentric rings of
optical sensors of different diameters form a sensor array that
allows the system to monitor the progress of a blood leak. One of
the sensors of the internal ring (small diamter sensors) looks for
a lack of reflection that, due to the sensor's small diamter, is
considered insignificant. If the next ring of (larger diameter)
sensors does not lose reflected light, the system determines that
the leak is not serious. Should the leak become serious, it reaches
the outer ring of larger diameter sensors. The system uses the time
between detections in successive rings to determine the flow of the
blood leakage. The spacing between rings allows estimation of the
volume of blood leakage.
[0122] Microcontroller 98 gathers data from optical sensors 92 and
reports this data in an embodiment via RF signal 58 to dialysis
machine 100. Machine 100 can include at least one of signal
conditioning 40, DSP 44 (which can have onboard RAM and ROM as well
as other apparatus and functionality as described herein), which
are used to analyze signal 58. In an alternative embodiment,
microcontroller 98 includes signal conditioning, such as an analog
to digital converter and/or signal summing circuitry, which can
combine the outputs from each of the photosensors 92 to yield a
single digitized signal 58, which is representative of entire flex
circuit 90. In a further alternative embodiment, the software and
processing is stored in microcontroller 98, in which case signal 58
tells the machine 100 whether or not an access disconnection takes
place. Again, signal 58 can be continuous, intermittent, sent only
when commanded, etc.
[0123] To save the power of supply 54, microcontroller 98 in one
embodiment is maintained in a sleeve or power save mode and optical
sensors 92 are off until dialysis instrument 100 requests data from
the radio frequency link. At this point, microcontroller 98 "wakes
up", energizes light sensors 92, reads signals from optical
receivers of sensors 92 and transmits status information back to
dialysis instrument 100. In one embodiment, again, if any of
sensors 92a to 92e does not receive enough light, DSP 94 issues a
distress call to machine 100 and simultaneously energizes an audio
alarm. Machine 100 can cause any other suitable protective action
described herein to be taken.
Electrocardiogram ("ECG") Remote Access Disconnection Sensor
[0124] Referring now to FIGS. 15, 16, 17 and 18A to 18C, various
systems are shown that detect an access disconnection using signals
form an electrocardiogram ("ECG"). Generally, an ECG is a test that
measures electrical signals that control the rhythm of a person's
heartbeat. The heart is a muscular pump made up of four chambers,
two upper chambers called atria and two lower chambers are called
ventricles. A natural electrical system causes the heart muscle to
contract and pump blood through the heart to the lungs and the rest
of the body.
[0125] Electrodes for the ECG are placed on a patient's skin to
detect this natural electrical activity of the heart. In system 120
of FIG. 15, during dialysis therapy, a first electrode 122 is
attached to venous line 18, while a second electrode 124 is
attached to the patient's skin, for example, at leg 12a (as shown
here), arm 12b, or chest 12c of patient 12 or is alternatively
connected to arterial line 14. Electrodes 122 and 124 can be
connected at venous line 18 and arterial line 14 through direct
contact, capacitive coupling, inductive coupling, wireless or
otherwise. Alternatively, multiple body electrodes 124 can be
placed at different locations 12a, 12b, 12c of patient 12.
[0126] FIGS. 18A to 18C show three possible arrangements for
contact/blood coupling. In FIG. 18A, electrode 122 is placed inside
venous line 18 and contacts blood directly. In FIG. 18B, electrode
122 is embedded within the wall of venous line 18 and couples to
the blood, e.g., capacitively or inductively. In FIG. 18C,
electrode 122 is placed outside of venous line 18 and likewise
couples to the blood, e.g., capacitively or inductively. The
electrodes can be metal or of a conductive polymer material.
[0127] System 120 of FIG. 15 shows a blood pump 102 and dialyzer
108 connected to arterial line 14 and venous line 18. The
extracorporeal circuit includes other components not illustrated
here for convenience. Also, dialyzer 108 communicates with a
dialysate source, e.g., bagged or on-line, an pumps that deliver
dialysate to the dialyzer 108, which again are not shown for
convenience. The '454 patent referenced above discloses further
details concerning the extracorporeal and dialysate circuits, which
are applicable to each of the systems described herein. The
teachings of each of the systems described herein are also
applicable to access disconnection in hemofiltration and
hemodialfiltration systems.
[0128] Electrodes 122 and 124 are connected electrically to signal
conditioning 40 and signal processing, which can include RAM 42 and
DSP 44 as has been discussed herein. Any of signal conditioning 40,
RAM 42 and DSP 44 can be located locally or remotely as desired and
as discussed herein.
[0129] Electrodes 122 and 124 can alternatively or additionally be
connected to a machine that translates the electrical activity into
an electrocardiogram, which may show: evidence of heart
enlargement, signs of insufficient blood flow to the heart, signs
of a new or previous injury to the heart (e.g., due to a heart
attack), heart rhythm problems (arrhythmias), changes in the
electrical activity of the heart caused by an electrolyte imbalance
in the body, and signs of inflammation of the sac surrounding the
heart (pericarditis). These parameters may be useful during
dialysis as discussed in more detail below.
[0130] Under normal conditions, the natural electrical signals that
control the rhythm of a person's heartbeat create a signal 126
shown figuratively in FIG. 15. Upon an access disconnection of
venous line 18 in the illustrated embodiment, signal 126 is no
longer sensed because electrical communication with the body
through the blood is lost. Machine 100 sees the lack of signal 126
as an access disconnection and causes any of the measures discussed
herein to be taken.
[0131] FIGS. 16 and 17 illustrate an alternative system 140 and
catheter assembly 142 used in system 140, respectively. In system
140 of FIG. 16, a cardiac catheter access at chest 12c of patient
12 using cardiac catheter assembly 142 is used. Cardiac access and
catheter assembly 142 provide a more direct access to the heart and
its associated signals than does needle access at the arm 126 of
patient 12. Cardiac access and catheter assembly 142 may be better
suited for acute treatments. Here, the doctor can more directly
monitor electrograms from the blood pool inside the heart and
provide more or better information about the cardiac function than
with typical arterial and venous access, while still dialyzing
patient 12.
[0132] Catheter 146 of assembly 142 is equipped with electrodes,
such as electrodes 122 and 124, via any of the configurations shown
in connection with FIGS. 18A to 18C. Catheter assembly 142 includes
an arterial access section 114 and a venous access section 118,
which connect respectively to arterial line 14 and venous line 18
of the extracorporeal circuit. Catheter assembly 142 also includes
a guide wire 144 for directing catheter 146 to a desired location,
e.g., directly into the patient's heart or to a desired local vein,
artery or graft.
[0133] In systems 120 and 140, signal processing via DSP 44
additionally or alternatively processes signal 126 to calculate any
one or more of heart rate variability, respiration, stroke volume,
cardiac output and central blood volume. Further, a bioimpedance
source 130 is connected to the patient, so that system 120 may make
bioimpedance measurements. Additionally or alternatively, systems
120 and 140 allow for the injection of a solution into the
extracorporeal circuit, which is used for pacing control for
patients having implanted cardiac rhythm management devices
(pacemakers). System 120 and 140 allow for key cardiovascular
parameters to be monitored during dialysis, which may have
beneficial effects on the dialysis therapy or be used for other
purposes.
[0134] Bioimpedance in general is a measure of changes in the
electrical conductivity of the thorax or heart. It can for example
be a measure based on pulsatile blood volume changes in the aorta.
Bioimpedance is relevant to the measurment of cardiac output and
circulating blood volume.
[0135] In particular, thoracic electrical bioimpedance (also
referred to as impedance cardiography) has been investigated as a
noninvasive way to assess cardiac output and other cardiovascular
functions. Changes in cardiac output are used to identify a change
in the hemodynamic status of a patient or to ascertain the need
for, or response to, treatment, e.g., for critically ill patients
and patients at high risk for morbidity and mortality.
[0136] Thoracic bioimpedance has been investigated for a variety of
indications, including, evaluation of the hemodynamics of patients
with suspected or known cardiovascular disease, differentiation of
cardiogenic from pulmonary causes of acute dyspnea, optimization of
atrioventricular interval for patients with A/V sequential
pacemakers, and optimization of drug therapy in patients with
congestive heart failure.
[0137] Any of the above parameters may be monitored either in
connection with dialysis or as an additional benefit of the
treatment.
Capacitive Blood Leak Detection System
[0138] FIGS. 19A and 19B illustrate an alternative blood leak
detection device 150, which wraps around a patient's arm in any of
the manners discussed above with system 80 and covers access
needles 16 and 20. Device 150 includes an array of mini-capacitors
152 as seen best in FIG. 19A. Waterproof, e.g., plastic, insulators
154a to 154c are placed around both sides of the capacitors. A
ground or shield 156 is placed between the backside of capacitors
152 and rear insulator 154c.
[0139] Device 150 does not have to absorb blood to detect a blood
leak. The presence of blood beneath mini-capacitors 152 results in
a change in the dielectric field surrounding the capacitors. That
is, if a wet spot develops beneath device 150, the region of
capacitors 152 sensing a dielectric change would grow. If the
region stops growing, the system using device 150 (which can be any
of the remote or wired systems discussed herein) assumes a normal
amount of seepage has occurred, which is distinguishable from a
blood leak or needle dislodgement. A small amount of seepage is a
common occurrence at "needle sticks" and should not produce an
alarm. If the blood leak grows large enough, the system using
device 110 assumes that a partial or full access disconnection has
occurred and sounds an alarm.
Redundant Access Disconnection/Blood Leak Detection System
[0140] Certain known access disconnection systems rely on the
breaking of an electrical circuit to detect an access problem. One
problem with these systems is that a needle dislodging from the
patient does not always break the electrical circuit. A needle can
for example dislodge from the patient but direct the flow of blood
over the access from which the needle has been dislodged or over
the other (e.g., arterial) needle to complete or re-complete the
electrical circuit. Here, blood would not be returned to the
patient but no alarm would sound.
[0141] Other known systems assume that a dislodged needle will
direct the flow of blood onto a part of the device or system. Here,
if the needle is dislodged completely and quickly from under the
device, the flow of blood that is supposed to seep onto a part of
the system may not (or not enough) and again no alarm is
sounded.
[0142] To address the above described problems, any of the
above-described systems can be used in combination with one another
or in combination with other types of access disconnection or blood
leak detection systems. In particular, a dislodgement type system
can be combined with a blood leak detection system. Optical system
80 for example is a blood leak detection system, which is
particularly adept at detecting blood leaking at the access site.
Another type of blood leak detection system is a conductive blanket
or pad, which covers the access site in a manner similar to system
80 of FIGS. 10 to 14. The conductive blanket or pad includes
contacts which form a closed electrical loop when contacted by
blood seeping from the patient access. An additional blood leak
detection system 150 is disclosed above in connection with FIGS.
19A and 19B.
[0143] Dislodgement systems, such as impedance sensing systems
described in the '098 and '480 patents discussed above, are
particularly adept at detecting when a needle or other access
instrument has become fully dislodged from the patient. Ultrasound
access disconnection system 10, acoustic systems 60a to 60c and
bioimpedance system 120 are also dislodgement type systems that
adeptly detect a full needle dislodgement.
[0144] Accordingly, it is contemplated to combine one of each of
the blood leak detection systems and needle dislodgement systems in
a hybrid or redundant system, which adeptly detects either failure
mode. For example, any one of the impedance systems of the '098 and
'480 patents, ultrasound access disconnection system 10, acoustic
systems 60a to 60c and bioimpedance system 120 (full dislodgement)
can be combined with any one of the optical (system 80), conductive
blanket or capacitive (device 150) blood leak detection systems, so
that the manner in which the venous needle has been dislodged does
not matter. The access disconnection system causes an alarm if the
venous needle is dislodged quickly and falls off of the patient.
The blood leak detection system causes an alarm if the venous
needle is partially of fully dislodged and directs blood flow over
the venous or arterial needle.
[0145] It should be understood that various changes and
modifications to the presently preferred embodiments described
herein will be apparent to those skilled in the art. Such changes
and modifications can be made without departing from the spirit and
scope of the present subject matter and without diminishing its
intended advantages. It is therefore intended that such changes and
modifications be covered by the appended claims.
* * * * *