U.S. patent application number 12/262777 was filed with the patent office on 2009-02-26 for occlusion system and method for a flow control apparatus.
This patent application is currently assigned to SHERWOOD SERVICES AG. Invention is credited to Joseph A. Hudson, Christopher A. Knauper.
Application Number | 20090055107 12/262777 |
Document ID | / |
Family ID | 35451522 |
Filed Date | 2009-02-26 |
United States Patent
Application |
20090055107 |
Kind Code |
A1 |
Knauper; Christopher A. ; et
al. |
February 26, 2009 |
OCCLUSION SYSTEM AND METHOD FOR A FLOW CONTROL APPARATUS
Abstract
A flow control apparatus having a flow monitoring system capable
of detecting and identifying a downstream occlusion present within
an administration feeding set loaded to the flow control apparatus
is disclosed. A software subsystem is associated with the flow
control apparatus and administration feeding set, the software
system plots at least one discrete date point against a standard
occlusion profile to detect if a downstream occlusion present
within the administration feeding set.
Inventors: |
Knauper; Christopher A.;
(O'Fallon, MO) ; Hudson; Joseph A.; (O'Fallon,
MO) |
Correspondence
Address: |
TYCO HEALTHCARE - EDWARD S. JARMOLOWICZ
15 HAMPSHIRE STREET
MANSFIELD
MA
02048
US
|
Assignee: |
SHERWOOD SERVICES AG
Schaffhausen
CH
|
Family ID: |
35451522 |
Appl. No.: |
12/262777 |
Filed: |
October 31, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11464429 |
Aug 14, 2006 |
7447566 |
|
|
12262777 |
|
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|
10853926 |
May 25, 2004 |
7092797 |
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11464429 |
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Current U.S.
Class: |
702/48 ;
340/608 |
Current CPC
Class: |
A61M 2205/3351 20130101;
A61M 5/14232 20130101; A61M 5/16831 20130101; A61M 2005/16872
20130101; A61M 2005/16868 20130101; G05D 7/0688 20130101; A61M
2205/3375 20130101; Y10S 128/13 20130101 |
Class at
Publication: |
702/48 ;
340/608 |
International
Class: |
G01F 1/00 20060101
G01F001/00; G08B 21/00 20060101 G08B021/00 |
Claims
1. A flow control apparatus comprising: a) a flow control apparatus
adapted to be loaded with an administration feeding set having an
upstream side and a downstream side, b) a software subsystem in
operative association with the flow control apparatus, the software
subsystem is capable of identifying a downstream occlusion present
within the administration feeding set; and c) the software
subsystem plotting at least one discrete data point against a
standard occlusion profile for providing an occlusion detected
condition.
2. The flow control apparatus according to claim 1, further
comprising a single sensor for determining an absence and presence
of fluid in the feeding set.
3. The flow control apparatus according to claim 2, wherein said
single sensor comprises an ultrasonic transmitter assembly that
transmits an ultrasonic signal through said administration feeding
set.
4. The flow control apparatus according to claim 1, wherein the
occlusion detected condition sounds an alarm.
5. A method of monitoring fluid flow comprising: a) loading the
administration feeding set on a flow control apparatus; b)
determining an average rotor revolution time; c) plotting at least
one discrete data point against a standard occlusion profile; and
d) identifying a downstream occlusion.
6. The method according to claim 5, wherein the step of plotting is
calculating the discrete data point as NewTime less the average
rotor revolution time.
7. The method according to claim 5, wherein the step of identifying
is the at least one discrete data point matching the standard
occlusion profile for at least one rotor revolution.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a flow control apparatus
capable of identifying a downstream occlusion condition within an
administration feeding set.
BACKGROUND OF THE INVENTION
[0002] Administering fluids containing medicine or nutrition to a
patient is generally well known in the art. Typically, fluid is
delivered to the patient by an administration feeding set loaded to
a flow control apparatus, such as a pump, connected to a source of
fluid which delivers fluid to a patient.
[0003] A flow control apparatus of the prior art may also be
capable of monitoring and detecting fluid flow conditions that can
occur within the loaded administration feeding set during operation
of the flow control apparatus. Generally, prior art flow monitoring
systems that are capable of monitoring and detecting flow
conditions may rely on separate sensors being placed at the
upstream and downstream sides of the administration feeding set in
order to distinguish between an upstream or a downstream flow
condition.
[0004] Therefore, there is a need in the art for an improved flow
control apparatus having a flow monitoring system capable of
identifying between an upstream flow condition and a downstream
flow condition using a single sensor, thereby making it possible to
monitor the flow of the fluid and recognize any problem that has
occurred in the delivery of the fluid.
SUMMARY OF THE INVENTION
[0005] The present invention relates to a flow control apparatus
comprising a flow control apparatus adapted to be loaded with an
administration feeding set having an upstream side and a downstream
side, a single sensor for detecting the presence or absence of
fluid in the upstream side of the administration feeding set, and a
software subsystem in operative association with the single sensor,
wherein the software subsystem is capable of identifying between an
upstream flow condition and a downstream flow condition present
within the administration feeding set.
[0006] The present invention also relates to a flow control
apparatus comprising a flow control apparatus adapted to be loaded
with an administration feeding set, an administration feeding set
having an upstream side and a downstream side with the
administration feeding set loaded to the flow control apparatus, a
single sensor for detecting the presence or absence of fluid in the
upstream side of the administration feeding set, and a software
subsystem in operative association with the single sensor, wherein
the software subsystem is capable of identifying between an
upstream flow condition and downstream flow condition present
within the administration feeding set loaded to the flow control
apparatus.
[0007] The present invention further relates to a method for
monitoring fluid flow comprising engaging one end of an
administration feeding set to at least one fluid source, loading
the administration feeding set to a flow control apparatus,
engaging another end of the administration feeding set, and
identifying between an upstream flow condition and a downstream
flow condition present within the administration feeding set loaded
to the flow control apparatus.
[0008] The system and method is a downstream occlusion (DSO)
triggering test that incorporates a standard occlusion profile to
determine an occluded feeding tube. The DSO triggering test is
invoked through software or user initiated. The DSO triggering test
is based on relative rotor turn durations, in milli-seconds (ms),
and consecutive rotor turns, measured in turns, as compared against
a standard profile for the flow control apparatus.
[0009] As the flow control apparatus is running, the system is
determining the time of a rotor revolution until the microprocessor
receives the required number of encoder signals, which is
representative of one complete rotor turn. The system tracks a
number of relative revolution durations over apparatus' period of
operation, as discrete data points and each data point is compared
against the standard occlusion profile, as shown in FIG. 6B or FIG.
6C. The system can set an alarm based on an occlusion detected
condition, or control will pass to step 289 in FIG. 4 to determine
an occlusion, when the system determines an increase in the
relative rotor revolution duration time over one or more rotor
turns, or if the duration time matches a standard occlusion
profile.
[0010] In the first embodiment, a number of revolution times are
stored in a revolution history buffer. The buffer, when filled, is
averaged and compared against the next NewTime to determine an
actual relative rotor duration time difference. This time
difference or discrete data point is compared against the standard
profile over one or more rotor turns. If compared over a number of
rotor turns, and the system is trending higher, the occlusion
detected sets the occlusion alarm, or the main control loop exits
to step 289 in FIG. 4, to determine the occlusion. If the duration
time selected to be a single discrete data point and is meets the
standard profile at a single rotor turn, the occlusion detected
condition sets the alarm on, to sound.
[0011] The next NewTime or rotor revolution time can be filtered
(as described in the detailed specification). The DSO Triggering
test is used to identify an occlusion state or condition sooner
than the procedure, described in FIG. 4, and DOS Triggering
operates as a stand alone occlusion detection (as shown in FIG.
10), or the main control loop can exit to step 289 at FIG. 4, as
described in an alternative embodiment below in FIG. 11.
[0012] The standard profile is stored as computer instructions. The
instructions can be a quadratic equation or a data table of points.
The profile is loaded into flash memory at the start of the pump.
Alternatively the standard profile may be constructed during a
pumping operation, such as flushing, by tallying a series of
relative rotor durations by consecutive rotor turns and storing
them in an array or buffer location. The program may also save this
alternative standard profile to an EEPROM for later use.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a perspective view of an exemplary flow control
apparatus having a flow monitoring system according to the present
invention;
[0014] FIG. 2 is a side view of the flow control apparatus with an
administration feeding set loaded thereto according to the present
invention;
[0015] FIG. 3 is a simplified block diagram illustrating the
elements of the flow control apparatus comprising a flow monitoring
system according to the present invention;
[0016] FIG. 4 is a flow chart of the flow monitoring system
according to the present invention;
[0017] FIG. 4A is a sub-routine of the flow chart shown in FIG. 4
according to the present invention;
[0018] FIG. 5A is a graph illustrating the signal strength over
time for a bag empty condition detected by the sensor according to
the present invention; and
[0019] FIG. 5B is a graph illustrating the signal strength over
time for an upstream occlusion detected by the sensor according to
the present invention.
[0020] FIG. 6A is a plot of the relative rotor turn duration,
operating within a tolerance band, versus the consecutive rotor
turns, along with a standard occlusion profile.
[0021] FIG. 6B is a plot representative of a standard occlusion
profile similar to FIG. 6A, with a number of relative rotor turn
durations computed during the flow apparatus operation.
[0022] FIG. 6C is a temporary occlusion plotted against the
standard occlusion profile similar to FIG. 6A.
[0023] FIG. 7 is a flow chart of the main control loop of the
downstream occlusion trigger test illustrated in FIG. 6B or FIG.
6C.
[0024] FIG. 8 is a flow chart of the start rotor routine at step
760 of FIG. 7.
[0025] FIG. 9 is a flow chart of the stop rotor routine at step 770
of FIG. 7.
[0026] FIG. 10 is a flow chart of the occlusion found at step 960
of FIG. 9, for the first embodiment.
[0027] FIG. 11 is a flow chart of an occlusion found at step 960 of
FIG. 9, for the alternative embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0028] Referring to the drawings, an embodiment of the flow control
apparatus according to the present invention is illustrated and
generally indicated as 10 in FIGS. 1-5. Flow control apparatus 10
comprises a flow monitoring system 12 that is capable of detecting
and identifying between upstream and downstream flow conditions
present within an administration feeding set 14. The administration
feeding set 14 includes tubing 56 that is loaded to the flow
control apparatus 10 for delivery of fluid to a patient by engaging
a valve mechanism 26 and mounting member 74 of the administration
feeding set 14 to the flow control apparatus 10. As used herein,
the term load means that the valve mechanism 28 and mounting member
74 are engaged to the flow control apparatus 10 and tubing 56 is
placed in a stretched condition between the valve mechanism 28 and
mounting member 74 such that the administration feeding set 14 is
ready for operation with flow control apparatus 10.
[0029] Referring to FIGS. 1 and 2, an exemplary flow control
apparatus 10 according to the present invention comprises a housing
20 adapted for loading administration feeding set 14 to the flow
control apparatus 10. Flow control apparatus 10 comprises a main
recess 124 covered by a main door 136 and includes first and second
recesses 58 and 60 for providing sites that are adapted to load the
administration feeding set 14 to the flow control apparatus 10 when
engaging the valve mechanism 28 and mounting member 74 to first and
second recesses 58, 60, respectively. Preferably, a means for
driving fluid, such as a rotor 26, is rotatably engaged through
housing 20 and adapted to engage tubing 56 such that tubing 56 is
placed in a stretched condition between first and second recesses
58, 60 when the administration feeding set 14 is loaded to the flow
control apparatus 10.
[0030] As used herein, the portion of tubing 56 of administration
feeding set 14 leading to rotor 26 is termed upstream, while the
portion of tubing 56 leading away from rotor 26 is termed
downstream. Accordingly, rotation of rotor 26 compresses tubing 56
and provides a means for driving fluid from the upstream to the
downstream side of the administration feeding set 14 for delivery
to a patient. The present invention contemplates that any flow
control apparatus having a means for driving fluid may be used,
such as a linear peristaltic pump, bellows pump, turbine pump,
rotary peristaltic pump, and displacement pump. In addition, the
present invention contemplates that a means for preventing fluid
flow in the administration feeding set 14 is preferably valve
mechanism 28; however any means that can prevent fluid flow through
the administration feeding set 14 may be used.
[0031] Referring to FIG. 1, flow control apparatus 10 further
comprises a user interface 40 that assists the user to operatively
interface with the flow control apparatus 10. A display 70, in
operative association with a plurality of buttons 138 positioned
along an overlay 66, assist the user to interact with a
microprocessor 62 to operate the flow monitoring system 12
according to the present invention.
[0032] Referring to FIG. 3, flow control apparatus 10 further
comprises a microprocessor 62 in operative association with a
single sensor 32. A software subsystem 36 is operatively associated
with microprocessor 62 and is further associated with flow
monitoring system 12 and a means for preventing fluid flow, such as
valve mechanism 28, that provides a means for the flow control
apparatus 10 to detect and identify between upstream and downstream
flow conditions present in the administration feeding set 14 during
operation of the flow control apparatus 10. As noted above, flow
control apparatus 10 includes single sensor 32 for detecting
whether fluid is present or absent in tubing 56 at the upstream
side of the administration feeding set 14. The single sensor 32 is
located on housing 20 of the flow control apparatus 10 and is
positioned to detect the presence or absence of fluid in the
upstream side of the administration feeding set 14.
[0033] In an embodiment shown in FIG. 2, single sensor 32 is
incorporated in a recessed sensor track 42 and is adapted to
securely receive tubing 56 therein when the administration feeding
set 14 is loaded to the flow control apparatus 10.
[0034] In order for single sensor 32 to detect the presence or
absence of fluid in the tubing 56 of the administration feeding set
14 it is required that tubing 56 be engaged and retained within
sensor track 42. In one embodiment, the engagement and retention of
tubing 56 within sensor track 42 is achieved by activating flow
control apparatus 10 when tubing 56 is empty of fluid and engaged
around the flow control apparatus 10 such that a vacuum is created
that decreases the outer diameter of tubing 56 as air is evacuated
from the administration feeding set 14, thereby placing tubing 56
in a deflated state. In this deflated state, the user may easily
insert tubing 56 within sensor track 42 when loading the
administration feeding set 14 to the flow control apparatus 10.
[0035] Further, with tubing 56 empty of any fluid, a valve
mechanism 28 connected to tubing 56 is engaged to the first recess
58, the tubing 56 then wrapped around rotor 26, and a mounting
member 74 engaged to second recess 60 such that administration
feeding set 14 is loaded to flow control apparatus 10 and the
portion of tubing 56 between first and second recesses 58 and 60 is
in a stretched condition. Valve mechanism 28 is then operated to
allow fluid flow communication through tubing 56 such that air is
evacuated from the administration feeding set 14. Thus, when the
rotor 26 is made operational during this priming procedure a vacuum
is created within tubing 56 forcing it to collapse due to the
flexible nature of tubing 56 and lack of fluid contained in the
administration feeding set 14. This temporary collapse of tubing 56
coupled with the tensile forces applied from operating rotor 26
allows tubing 56 to be easily retained within sensor track 42.
[0036] In addition, when the flow control apparatus 10 is
operational and the tubing 56 engaged within sensor track 42, fluid
flow through tubing 56 increases the outer diameter of tubing 56
relative to the inner diameter of the sensor track 42. Once the
tubing 56 is engaged within sensor track 42 and the remaining
portions of the administration feeding set 14 are engaged to flow
control apparatus 10, the flow monitoring system 16 becomes
operational.
[0037] Microprocessor 62 controls and manages the operation of the
various components of the flow control apparatus 10. Preferably,
single sensor 32 comprises an ultrasonic transmitter assembly 90
that transmits an ultrasonic signal through the portion of tubing
56 seated in the sensor track 42 to provide a means for detecting
the presence or absence of fluid in the upstream side of the
administration feeding set 14 when the signal is received by a
receiver assembly 92. Upon receipt of the ultrasonic signal,
receiver assembly 92 detects whether fluid is present or absent
within tubing 56 along sensor track 42 based on the characteristics
of the ultrasonic signal received by the microprocessor 62. The
receiver assembly 92 then communicates with the microprocessor 62.
Based on the characteristics of the received ultrasonic signal
communicated to microprocessor 62 software subsystem 36 determines
whether fluid flow within the administration feeding set 14 is
normal or a flow abnormality exists.
[0038] Software subsystem 36 determines through a series of
decision points and steps whether normal flow or abnormal flow
conditions exist within tubing 56, and if an abnormal flow
condition does exist, whether it is a bag empty condition, upstream
occlusion, or a downstream occlusion.
[0039] Referring to the flow charts in FIGS. 4 and 4A, the various
decision points and steps executed by software subsystem 36 to
perform an intermittent test procedure A by flow monitoring system
12 are illustrated. Software subsystem 36 directs flow control
apparatus 10 to perform various operations related to detecting and
distinguishing between upstream and downstream flow conditions
present in the administration feeding set 14. During normal
operation, single sensor 32 transmits ultrasonic signals through
tubing 56 engaged within sensor track 42 for detecting the presence
or absence of fluid in the administration feeding set 14. During
operation of flow control apparatus 10 software subsystem 36
decides at predetermined times whether to initiate an intermittent
test procedure A to determine whether a downstream occlusion
exists. Intermittent test procedure A comprises terminating fluid
flow communication through the administration feeding set 14 by
valve mechanism 28, transmitting and detecting an ultrasonic wave
for determining the presence or absence of fluid by single sensor
32 and a repetition of these steps, if necessary.
[0040] In particular, at step 289 software subsystem 36 decides
whether to perform the intermittent test procedure A as illustrated
in FIG. 4A. If so, the microprocessor 62 instructs flow control
apparatus 10 to the OFF condition at step 290 in order to terminate
operation of flow control apparatus 10 such that rotor 26 no longer
drives fluid through tubing 56. At step 292, microprocessor 62 then
places valve mechanism 28 in the blocking position that prevents
fluid flow through tubing 56.
[0041] After fluid flow has been prevented through the
administration feeding set 14 by valve mechanism 28, a baseline
signal is taken by the single sensor 32 at step 294 for providing
microprocessor 62 with a reading of the signal when the flow
control apparatus 10 is reactivated at step 296. After
re-activation, any fluid present within tubing 56 should be driven
through tubing 56 by operation of rotor 26 and delivered to the
patient as long as no occlusion is present along the downstream
side of the administration feeding set 14. After a short period of
time placement of valve mechanism 28 in the blocking position that
terminates fluid flow should cause tubing 56 to run dry of any
remaining fluid unless a downstream occlusion is present which
would effectively prevent fluid from being delivered to the patient
as fluid is forced to remain within tubing 56 due to the occlusion.
Software subsystem 36, after a predetermined amount of time,
permits any excess fluid to drain from tubing 56 at step 298. At
step 300, single sensor 32 then transmits another ultrasonic signal
through tubing 56 and takes a second reading to determine if fluid
is present or absent within the administration feeding set 14. If
fluid remains within the administration feeding set 14, software
subsystem 36 then determines that a downstream occlusion is present
and sounds an alarm.
[0042] Once intermittent test procedure A is completed, software
subsystem 36 reaches a decision point 302 which determines whether
or not a downstream flow condition, such as an occlusion along the
downstream side of the administration feeding set 14 is present
within tubing 56. If no fluid remains in tubing 56 at decision
point 302, software subsystem 36 determines that no downstream
occlusion is present. At step 304, microprocessor 62 re-sets the
counter and places flow control apparatus 10 in an OFF condition at
step 306. Valve mechanism 28 is then placed in either a feeding or
flushing position that permits fluid flow through tubing 56 at step
308. After actuation of valve mechanism 28 to the feed or flush
position flow control apparatus 10 is placed in the ON condition at
step 310 and the flow monitoring system 12 has software subsystem
36 return to step 289.
[0043] If at decision point 302 an occlusion along the downstream
side of the administration feeding set 14 is possible then decision
point 312 is reached. Decision point 312 counts the number of
occurrences that single sensor 32 detects the presence of fluid
within tubing 56 which is referred to as D.sub.o, while a pre-set
maximum number of occurrences that flow monitoring system 12 allows
for detection of a possible downstream occlusion being referred to
as D.sub.o(max). If the D.sub.o is not greater than D.sub.o(max) at
decision point 312 software subsystem 36 will determine that no
downstream occlusion exists and valve mechanism 28 is placed in a
position that permits fluid flow through the administration feeding
set 14 in a manner as previously described above in steps 304, 306,
308, and 310. However, if D.sub.o is greater than D.sub.o(max) a
downstream occlusion may exist and software subsystem 36 will
direct microprocessor 62 to activate an alarm 68.
[0044] Preferably, alarm 68 may be audible, visual, vibratory or
any combination thereof. In an embodiment of the present invention
it is anticipated that a certain type of alarm 68 may represent a
specific abnormal flow condition being present within
administration feeding set 14 and identifiable to the user by its
own unique visual, audible and/or vibratory alarm 68. For example,
alarm 68 having different sounds could indicate different types of
upstream and downstream flow conditions, such as a downstream
occlusion, a bag empty condition, or an upstream occlusion. These
unique alarms 68 allow for flow monitoring system 12 to signal the
presence of several different abnormal flow conditions.
[0045] The detection of the upstream flow conditions present within
administration feeding set 14, such as upstream occlusion or a bag
empty condition, is determined by the presence or absence of fluid
within tubing 56 by single sensor 32 at a detection point
positioned on the upstream side of administration feeding set 14.
However, unlike the detection of a downstream occlusion along the
administration feeding set 14 the detection of an upstream flow
condition, such as an upstream occlusion or bag empty condition, in
the administration feeding set 14 does not require that the
intermittent test procedure A be performed. Instead, the detection
of these upstream flow conditions is accomplished during the normal
operation of flow control apparatus 10 while valve mechanism 28 is
in the feeding or flushing position that permits fluid flow through
the administration feeding set 14.
[0046] Flow monitoring system 12 also detects and distinguishes
between upstream flow conditions, such as normal flow, bag empty,
and upstream occlusion conditions when the intermittent testing
procedure A is not being performed by software subsystem 36.
Specifically, at decision point 289 if software subsystem 36 does
not initiate intermittent test procedure A for detecting downstream
flow conditions software subsystem 36 will function to detect and
distinguish between the conditions of normal flow, bag empty, and
upstream occlusion.
[0047] Software subsystem 36 in operative association with flow
monitoring system 12 determines whether or not a normal upstream
flow condition exists within administration feeding set 14 during
operation of flow control apparatus 10. This operation occurs at a
decision point 314 and is determined based upon the presence or
absence of fluid as detected by the single sensor 32. Specifically,
if single sensor 32 detects the presence of fluid within tubing 56
then the flow is detected by software subsystem 36 at decision
point 314. A normal upstream flow condition exists because a flow
condition is not present that would occlude or obstruct fluid flow
on the upstream side of the administration feeding set 14 that
would cause fluid to become absent as detected by the single sensor
32. If flow is present at decision point 314 this normal flow
condition would be displayed on user interface 40 at step 315.
Accordingly, alarm 68 would not be activated since the patient
would receive the correct dosage of fluid during flow
conditions.
[0048] Flow monitoring system 12 only activates alarm 68 at
decision point 314 if a bag empty condition or an occlusion along
the upstream side of the administration feeding set 14 is detected
as evidenced by the absence of fluid in tubing 56 during operation
of the flow control apparatus 10. Software subsystem 36
distinguishes between bag empty condition and an upstream occlusion
at decision point 316. As depicted in FIGS. 5A and 5B, a comparison
is performed at decision point 316 in order to ascertain whether a
bag empty condition or an upstream occlusion is present within
administration feeding set 14.
[0049] As further shown, the graphs illustrated in FIGS. 5A and 5B
provide predetermined baselines that represent the relative signal
strengths of the ultrasonic signal received by the receiver
assembly 30B for a bag empty condition and upstream occlusion,
respectively, which provide a basis for distinguishing between
these two upstream flow conditions based upon a comparison of a
plurality of readings taken by single sensor 32 against the
respective predetermined baseline criteria representative of these
two flow abnormalities. In particular, software subsystem 36
compares the change of the signal strength from the plurality of
sensor readings generated by single sensor 32 over time against the
predetermined baseline criteria for these particular flow
conditions. This provides a comparison with readings taken by
single sensor 32 that permits the software subsystem 36 to
distinguish between a bag empty and an upstream occlusion. For
example, in a bag empty condition, the change between the
subsequent readings would decrease more rapidly over time, while in
an upstream occlusion the signal change would decrease more slowly
over time. It should be noted that while the graphs in FIGS. 5A and
5B depict an example of a preferred baseline criteria, other
baseline criteria which may distinguish these two flow
abnormalities may be utilized.
[0050] Upon the determination that a bag empty condition is present
at decision point 316 based upon signal comparison against the
predetermined criteria as described above, software subsystem 36
activates alarm 68. If the software subsystem 36 determines at
decision point 316 that an upstream occlusion is present, software
subsystem 36 would also direct the activation of an alarm 68
indicative of such a flow abnormality.
[0051] Accordingly, the flow monitoring system 12 is capable of
detecting and distinguishing between upstream and downstream flow
conditions including at least four separate flow conditions that
occur within an administration feeding set 14. The ability of the
flow monitoring system 12 to detect and distinguish between
upstream and downstream flow conditions is accomplished preferably
by a single detection point by single sensor 32 positioned at the
upstream side of the administration feeding set 14.
[0052] FIG. 6A illustrates the flow control apparatus 10 operating
within a proper tolerance. The discrete data points (described
below) are the stars (`*`). The data points varying above and below
a set point of 100 ms of the flow control apparatus 10. A tolerance
band of +/-30 ms, for example, represents system noise, which can
falsely trigger an occlusion indicator within the tolerance band.
The tolerance band can be set other values depending on the motor
or the required sensitivity. A sensitive application can be a
syringe pump, requiring a tighter or lower tolerance. The standard
occlusion profile is a straight line; however, a profile can be
different to match the flow control apparatus 10 pumping
characteristics.
[0053] To determine an occlusion or predict the occurrence of an
occlusion, at least one discrete date point (described below), must
be above the higher or lower limit of the tolerance band. The
dashed line is the normal operation of the flow control apparatus
10 varying above and below the horizontal line at a 100 ms set
point. The set point can change resulting in a change in the normal
operation, tolerance band, and even the standard occlusion profile
changes.
[0054] The concept of the present invention is monitoring, in
software, the drag on the motor through a series of software
calculations. Other prior art systems monitor directly the current
or voltage use of the motor with software, to indicate an
occlusion. These prior art systems suffer from not be flexible or
accurate, in some high performance cases such as medical, to
properly determine the presence or absence of an occlusion. The
term consecutive rotor turns is meant to be one or more discrete
data points in succession, as determined by the program or user
input (always possible with the LED screen at FIG. 1 at element
138). In other words, a rotor revolution turn can be skipped;
however, the test will continue using the next available rotor
revolution turn. The rotor revolution turn information could use
rotor turn 1, 3, 5, and 6 to determine the presence of a downstream
occlusion. The DSO Trigger test can cause the downstream occlusion
test in FIG. 4 or sound an occlusion alarm 68.
[0055] FIG. 6B illustrates the standard occlusion profile plot. The
plot is relative rotor turn duration, typically in mill-seconds
(ms), plotted against the consecutive rotor turns measured in
turns. The profile is independent of flow rate or the flow of a
material or substance through the administration feeding set 14.
Generally, a flow rate is based on the time between rotor turns and
is dependent on the rotor 26 shaft speed and encoder counts.
[0056] An encoder (not shown) is attached to the rotor 26 shaft
(not shown) and measured by the microprocessor 62. The number of
signals from the encoder to the microprocessor 62, overtime
indicates the speed. The number of encoder counts indicates a
complete rotor turn. The DSO triggering test is measuring the
relative revolution duration time of a rotor turn against a
standard occlusion profile for the purpose of identifying an
occlusion condition, not the flow rate. Once an occlusion detected
condition is identified, the system sets the DSO Trigger variable
(not shown), to TRUE and sets an occlusion alarm 68, or in the
alternative embodiment exits to step 286 in FIG. 4 at step 1130A
(described below), to perform the downstream occlusion test.
[0057] FIG. 6C shows a temporary occlusion. The rotor revolution
measured is plotted against the standard profile and compared
against the rotor history of previous turns, filtered or otherwise,
as shown in FIG. 6C. An increase in relative rotor revolution over
one rotor turn may reduce at the next rotor turn at or near the
tolerance band. This would represent a solid temporarily becoming
lodged in the tubing, and if the number of NewTime readings is set
at 1, the system may false alarm 68. Solids exist in formulae fed
to a patient. The scale in FIG. 6C has been changed. This
illustrates a design choice depending on the motor and other
factors, such as sensitivity, accuracy and frequency of alarming
required.
[0058] Referring to FIG. 7, the preferred embodiment of the
invention for the flow control apparatus 10 is shown. This
embodiment uses, among other things, an average of the rotor
history file (determined at step 940C), to obtain the necessary
repeatability and sensitivity required. An exemplary operation of
the main control loop 720 is shown for the downstream occlusion
trigger test or DSO Triggering test. A positive DSO Triggering
without chaining (described below) triggers an occlusion alarm
68.
[0059] At step 700, the DOS trigger test is started. The test
operates concurrently with the occlusion routine shown in FIG. 4.
At step 710, the rotor history file is reset. The rotor history
buffer or array is set to zero. The rotor history file or buffer
has a number of, filterer or unfiltered, rotor revolution times,
called NewTime below. At step 730, the user may manually invoke the
DOSTriggering test. This is accomplished by depressing a key on the
front of the flow control apparatus 10, or just entering the
Running Mode screen in FIG. 1 at 138.
[0060] The DOCInterval time (not shown) sets the frequency at which
the DSO Triggering test is run. For example, a DOCInterval set at
30 seconds means every 30 seconds the downstream occlusion test is
executed. At step 740, the main control loop 720 determines if the
flow control apparatus 10 is priming and resets the rotor history
buffer to zero at step 740A. This means the main control loop can
execute an occlusion check more quickly or less frequently, than
the occlusion detection in FIG. 4 above.
[0061] At step 750, the main control loop 720 stops the flushing
750 activity, if flushing, and skips one rotor revolution because
flushing occurs at high rate of speed. The one rotor revolution
allows the system to stabilize. NewTime is the time of a rotor
revolution, as discussed below. At 750A, the rotor revolution
information is skipped, not the revolution itself.
[0062] At step 760, a stopped rotor is started at step 810 (FIG.
8). At step 830, a rotor revolution timer is started to measure the
rotor revolution time, which is stored in NewTime. A rotor
revolution time is measured using the system clock (not shown). The
clock duration is measured after a fixed number of encoded signals
are received at the microprocessor for a rotor revolution or a
number of rotor revolutions, as specified in the DSO Triggering
test. The clock duration is independent of the rotor turn.
[0063] An occlusion will drag the rotor, which will take the rotor
26 longer to make a revolution, as measured by the number of
encoder signals returned to the microprocessor 62. The number of
encoder signals is fixed at the time of manufacture for the flow
control apparatus 10. So if a hundred encoder signals are needed
per a rotor revolution, once the microprocessor receives the
hundredth signal, the system clock time is measured and stored in
memory. The difference of the start time, at step 830 and stop time
at step 910 is stored in NewTime. This NewTime represents the rotor
revolution duration for one rotor revolution. At step 820A, the
system can still proceed to measure the rotor revolution time or
NewTime, if the system overrides the failed conditions at step
820.
[0064] At step 820, a set of pre-existing conditions can be checked
to determine if the current rotor turn is appropriate to measure
for a rotor revolution time. This improves accuracy and helps avoid
false occlusion alarms. The critical conditions may be the flow
control apparatus 10 is not flushing, not priming, in a normal flow
as opposed to super bolus mode, or no other system error exists.
Once the conditions 820 are satisfied, the revolution timer 830 is
started. The microprocessor 62 runs the timer 830, until the
required number of encoder signals (as discussed in the preceding
paragraph) are received.
[0065] At step 770, the end of a rotor 26 revolution is determined,
and if YES, the program exits to step 900 in FIG. 9. The command to
stop the rotor is given at step 910. At step 920, a set of
pre-existing conditions may be checked. The conditions are the same
as in step 820. Additional conditions are rotor is off, or the
current rotor revolution is not immediately following the
downstream occlusion test because the measure is not reliable for
averaging. If YES, the conditions are verified and control passes
to step 930. If NO, at step 920A it is determined if the there is
an override (Still Continue?), to use the rotor revolution for a
NewTime, otherwise the rotor revolution information is discarded at
step 920B and control returns to the main control loop at step
720.
[0066] At step 930, a NewTime is computed. The Revolution timer is
stopped and stored in NewTime. Alternatively, the system clock time
is stored in a buffer or temporary memory position. Then the clock
time, at step 830, is subtracted from the clock time at step 930
and this difference is stored in NewTime, as discussed above in
step 910.
[0067] At step 940, if the rotor history is filled, control passes
to step 950. Otherwise, control is passed to step 940A and the
buffer position is incremented. The rotor history position is
updated with NewTime and control passes to step 940B. At 940B, if
the rotor history array is filled, control passes to step 940C. At
step 940C, a rotor history average is determined. The average is
used to determine a discrete data point plotted on FIG. 6B, as
shown. The discrete data point is NewTime less the rotor history
average, provided the different is not greater than a Filter Error
for NewTime (described below in step 950A). The discrete data point
is the actual relative rotor revolution duration time, during flow
control apparatus 10 operation. The data point is plotted on, FIG.
6B, to determine if an occlusion is happening.
[0068] Returning to step 940B, in this embodiment, the array is
updated if there are still unfilled positions, which means the
HistoryCount variable (not shown) is not zero. The HistoryCount
variable is preset, when the history buffer is reset. The
HistoryCount is not necessarily reset every time the downstream
occlusion test is run.
[0069] The HistoryCount variable is counted down to determine the
number of non-zero rotor revolution NewTimes' are stored in the
history buffer, for averaging. The average of the rotor history
buffer or file is used to determine if the system is trending in
relative rotor revolutions. Trending higher indicates the system is
occluded downstream, as illustrated in FIG. 6B. At step 940D, the
rotor history buffer or array is not full, so exit to step 720.
[0070] An occlusion can occur for a variety of conditions. Material
may settle from the feed solution at low feed rates. The sediment
may collect and occlude the feeding set 14. The set 14 may become
pinched as the patient rolls or moves.
[0071] After the rotor history buffer is full at step 950, the
NewTime is filtered for an abnormal condition. An abnormal
condition can occur if a person interferes with the rotor 26 or the
rotor 26 jams. A person pinching the tubing 14 will cause an
occlusion alarm 68
[0072] If the system is filtering (at step 950A), the filter switch
is the absolute value of NewTime less the average of the rotor
history buffer (AvgRotorHistory) greater than a Filter error. The
Filter error is set in the program to be about 100 ms, and the
Filter error depends on the flow control apparatus 10. The Filter
error can be varied depending on the sensitivity of the flow
control apparatus 10. At step 950B, an error or abnormal condition
sets the NewTime to the current average of the rotor history file,
previously determined at step 940A. No error or abnormal condition,
the program determines the average history, at step 960, and passes
controls to FIG. 10.
[0073] In FIG. 10, the system is identifying at least one NewTime
that meets the standard profile in FIG. 6B. For improved accuracy,
three NewTime values that meet the standard profile over three
consecutive rotor turns will result in an occlusion detected
condition. The first test step is to ensure the system is not
chaining at step 1000.
[0074] At step 1000 in FIG. 10, the system is checked for chaining.
Chaining is too many downstream occlusion checks within DOCInterval
is occurring. For example, five downstream occlusion tests are
caused within ten minutes, the system is chaining. At step 1000A,
the downstream occlusion is disabled the system is reset and
control passes to the main control loop at step 720.
[0075] At step 1010, the NewTime is determined to be consistent
with the standard downstream occlusion profile and NewTime is above
the upper tolerance, in FIG. 6B. At step 1060, step 1010 is not
True or NO. At step 1010, the current rotor revolution is not
matching the standard profile, so step 1010 exits to step 1060. At
step 1060, the main control loop determines if the previous rotor
revolution, to the current rotor revolution or NewTime, is
consistent with the standard occlusion profile. If YES, then the
main control loop detected two inconsistent rotor revolutions and
will reset the rotor history file at step 1020. This is shown in
FIG. 6C, with the temporary occlusion.
[0076] One skilled in the art will recognize, one inconsistent
reading may introduce too many alarms, but a higher number may not
alarm quickly enough. The number of inconsistent rotor revolutions,
at step 1060 may be set with a counter, incremented or decremented,
after step 1060. If the counter condition is meet, then the rotor
history file is reset a step 1020.
[0077] At step 1040, NewTime, is converted to a discrete data point
as NewTime less AvgRotorHistory. At step 1050, the discrete data
point is compared to the standard occlusion profile, at FIG. 6B,
over one or more consecutive rotor turns, as determined by the
system Until the number of consecutive discrete data points are
plotted, the system will exit to the main control loop at step
1050A.
[0078] At step 1030, the standard occlusion profile is complete, if
at least one or more NewTime data points match the standard
occlusion profile, for the one or more consecutive rotor turns.
Referring to FIG. 6B, at rotor revolution turn one (1), the
discrete data point at step 1040 matches the relative duration for
the rotor turn at 110 ms or, outside of the tolerance band. The
system does not consider this point possibly occluding. If a second
discrete data point is used, this point is plotted at approximately
135 ms, at the second consecutive rotor turn. This point falls
outside the tolerance band and indicates a possible occlusion is
occurring. A third consecutive rotor turn may be required, at 140
ms, to set the DSO Triggering test to TRUE and to sound the
occlusion alarm at step 1030A. The number of discrete data point
matched to the standard occlusion profile, of FIG. 6, is dependent
on the accuracy or number of false occlusion alarms, the user will
tolerate for the flow control apparatus.
[0079] In an alternative embodiment in FIG. 11, the standard
profile is determined complete at step 1130 and the main control
loop exits to step 289 in FIG. 4, at step 1130A. This provides for
another level of occlusion detection, which uses the standard
profile, but actually determines the occlusion condition based on
FIG. 4. Like steps have not been described between FIG. 10 and FIG.
11. For example, step 1020 is the same as step 1120. The reader is
requested to refer to the description of the corresponding step in
FIG. 10, for FIG. 11
[0080] Although flow control apparatus 10 described above is an
exemplary embodiment, the present invention contemplates that the
flow monitoring system 12 may be used with any suitable flow
control apparatus.
[0081] It should be understood from the foregoing that, while
particular embodiments of the invention have been illustrated and
described, various modifications can be made thereto without
departing from the spirit and scope of the invention.
* * * * *