U.S. patent application number 09/773228 was filed with the patent office on 2001-09-27 for method and apparatus for automatically controlling the level of medication.
Invention is credited to Axel, Stephen L., Bui, Tuan, Levitas, Doron.
Application Number | 20010025156 09/773228 |
Document ID | / |
Family ID | 22939384 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010025156 |
Kind Code |
A1 |
Bui, Tuan ; et al. |
September 27, 2001 |
Method and apparatus for automatically controlling the level of
medication
Abstract
A method and apparatus which captures relevant information
pertaining to a patient's physiological conditions, automatically
adjusts the amount of medication to optimize the treatment of pain
and improve the patient's quality of life is described.
Inventors: |
Bui, Tuan; (Green Oaks,
IL) ; Levitas, Doron; (Chicago, IL) ; Axel,
Stephen L.; (Deerfield, IL) |
Correspondence
Address: |
Francis C. Kowalik, Esq.
Corporate Counsel, Law Department
Baxter International Inc.
One Baxter Parkway, DF2-2E
Deerfield
IL
60015
US
|
Family ID: |
22939384 |
Appl. No.: |
09/773228 |
Filed: |
January 31, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09773228 |
Jan 31, 2001 |
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09248492 |
Feb 10, 1999 |
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6231560 |
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Current U.S.
Class: |
604/66 ;
604/503 |
Current CPC
Class: |
A61M 2005/1405 20130101;
A61M 5/1723 20130101; A61M 2205/581 20130101 |
Class at
Publication: |
604/66 ;
604/503 |
International
Class: |
A61M 031/00 |
Claims
What is claimed is:
1. A method for automatically controlling the level of a patient's
medication administered from a programmable infusion pump,
comprising: programming the infusion pump with a set of
patient-specific, predetermined ranges of medication; initiating an
evaluation of the patient's current medication; obtaining
information pertaining to the patient's pain level; obtaining
information pertaining to the patient's side effects; obtaining
information pertaining to the patient's impairment of
functionalities; obtaining information pertaining to the patient's
current medication; evaluating the patient's current medication,
pain level, side effects and impaired functionalities with the set
of patient-specific, predetermined ranges of medication; and
controlling administration of the patient's medication based on the
evaluation.
2. The method of claim 1, wherein the step of obtaining information
pertaining to the patient's current medication comprises storing
information pertaining to the amount of medication administered to
the patient over a predetermined period of time.
3. The method of claim 1, wherein the controlling administration of
the patient's medication includes modification of a basal delivery
rate, a bolus dose and a number of bolus allowed within a certain
time frame.
4. The method of claim 1, wherein the step of obtaining information
pertaining to the patient's pain level further comprises storing
the number of bolus requests made by the patient which exceed the
maximum number of permitted boluses.
5. The method of claim 2, wherein the obtaining information
pertaining to the patient's pain level, side effects and impairment
of functionalities steps further comprise the steps of querying the
patient regarding the patient's pain level, side effects and
impairment of functionalities.
6. The method of claim 2, wherein the step of obtaining information
pertaining to the patient's side effects further comprises the step
of providing an independent evaluation of the patient's side
effects.
7. The method of claim 2, wherein the step of obtaining information
pertaining to the patient's impairment of functionalities further
comprises the step of providing an independent evaluation of the
patient's impairment of functionalities.
8. A routine for operating an infusion pump to automatically
control the level of a patient's medication, the infusion pump
comprising a controller for executing the routine and a memory for
storing the routine, responsive to a request for an evaluation of
the patient's current medication; comprising: a set of
patient-specific, predetermined ranges of medication stored in the
memory; a procedure for obtaining information pertaining to the
patient's pain level; a procedure for obtaining information
pertaining to the patient's side effects; a procedure for obtaining
information pertaining to the patient's impairment of
functionalities; a procedure for obtaining information pertaining
to the patient's current medication; a procedure for evaluating the
patient's current medication, pain level, side effects and impaired
functionalities with the set of patient-specific, predetermined
ranges of medication; and a procedure for modifying the patient's
medication based on the evaluation.
9. An infusion pump for administering a liquid medicant to a
patient, comprising: a liquid injection device adapted to be
connected to the patient; a conduit connected to the liquid
injection device; a pumping mechanism for pumping the liquid
medicant through the conduit and into the patient via the liquid
injection device; a controller for controlling the pumping
mechanism, wherein the controller controls the amount of liquid
medicant administered to the patient; a memory storing a set of
patient-specific, predetermined rates and amounts of liquid
medicant to be administered to the patient; a data acquiring
routine for obtaining information pertaining to the patient's pain
level, side effects and impairment of functionalities; and a
control routine for processing the data pertaining to the patient's
pain level, the patient's side effects, the patient's impairment of
functionalities, and a current rate and amount of liquid medicant
being administered to the patient and for automatically changing
the rate and amount of the liquid medicant to be administered to
the patient in accordance with the set of patient-specific,
predetermined ranges of medication.
10. The infusion pump of claim 9 further wherein the memory stores
data regarding the liquid medicant administered to the patient over
a predetermined period of time and wherein the modification routine
processes the data regarding liquid medicant administered to the
patient.
11. The infusion pump of claim 10 wherein the current rate and
amount of liquid medicant being administered to the patient
comprises a basal delivery rate, a bolus dose and a number of bolus
allowed within a certain time frame.
12. The infusion pump of claim 11 wherein data pertaining to the
patient's pain level comprises the number of bolus requests made by
the patient which exceed the maximum number of boluses.
13. The infusion pump of claim 11 wherein data pertaining to the
patient's pain level, side effects and impairment of
functionalities comprises data stored in response to querying the
patient regarding the patient's pain level, side effects and
impairment of functionalities.
14. The infusion pump of claim 11 wherein data pertaining to the
patient's side effects comprises data stored from an independent
evaluation of the patient's side effects.
15. The infusion pump of claim 11 wherein data pertaining to the
patient's impairment of functionalities comprises data stored from
an independent evaluation of the patient's impairment of
functionalities.
16. A method for automatically controlling the level of a patient's
medication administered from a programmable infusion pump,
comprising: programming the infusion pump with a set of patient
specific, predetermined ranges of medication; evaluating the
patient's current medication; evaluating the patient's
physiological conditions; and controlling administration of the
patient's medication within the predetermined range of medication
based on the evaluation.
17. The method of claim 16, wherein the evaluating the patient's
physiological conditions step includes evaluating the patient's
pain level, the patient's side effects and the patient's impairment
of functionalities.
18. The method of claim 16, further comprising querying the patient
about his physiological conditions; and storing the patient's
responses.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention is directed to a method and apparatus
for automatically adjusting the medication level for a patient, and
more particularly to adjusting the basal rate and the bolus rate of
administration in a patient control analgesia mode based on the
patient's pain intensity.
[0002] Infusion pumps are used to automatically administer liquid
medicants to patients. The liquid medicant is supplied from a
source of medicant and delivered to the patient via a catheter or
other injection device. The manner in which the liquid medicant is
infused is controlled by the infusion pump, which may have various
modes of infusion. An infusion pump typically can operate in five
basic modes of infusion: 1) a continuous mode in which the pump
delivers a single volume at a single rate; 2) an auto-ramp mode in
which the pump delivers liquid medicant at a rate that gradually
increases to a threshold rate, remains at the threshold rate for a
period of time, and then gradually decreases; 3) an intermittent
mode in which the pump delivers discrete liquid volumes spaced over
relatively long periods of time, such as a liquid volume every
three hours; 4) a custom mode in which the pump can be programmed
to deliver a unique infusion rate during each of 25 different time
periods; and 5) a pain controlled analgesic (PCA) mode during which
the pump will periodically infuse boluses of an analgesic in
response to requests by the patient.
[0003] In pain control analgesia, a pain relief medication or
analgesic is delivered to the patient via an infusion pump into a
patient's intravenous line, or to the epidural space or an
interthecal space. Usually the medication is delivered at a
constant rate, called the basal rate. The physician programs the
basal rate into the pump. However, the patient is allowed, within
bounds, to give himself additional medication, to reduce the pain
level, if desired. This is done via a bolus cord. The patient
presses a button on the bolus cord and the pump delivers a small
bolus of medication to the patient. The maximum level of medication
given in response to each press of the bolus cord button, is
programmed into the pump by the physician. The maximum number of
button presses which will result in a discharge of a bolus is also
programmed into the pump by the physician. Once the pump is
programmed by the physician, the patient can give himself a bolus
whenever he needs it, regardless of time between requests. However,
if the patient exceeds the maximum number of boluses programmed,
any additional requested boluses will not be successful and will
not result in the delivery of medication.
[0004] The physician limits the amount of medication given to the
patient at any one time, and over a period of time, to reduce the
level of side effects. Some pain relief medications have highly
undesirable side effects, such as nausea, vomiting, itching and
confusion, cardiac and respiratory depression or in sufficient
quantity, may result in death. Patient functionality, e.g.,
mobility and awareness, is affected by pain and side effects.
[0005] Controlling of the amount of pain medication, i.e., the
basal rate, the bolus dose and the maximum number of bolus doses
available to the patient is a delicate balance of competing
requirements. To increase pain relief, a physician will prescribe
greater medication. However, large doses of some pain medication
can increase the side effects and can impair patient
functionalities. Using a pain medication may reduce pain
sufficiently to enable the patient to move about. Using a level of
pain medication which produces confusion detracts from the
patient's mobility.
[0006] During acute care, when the patient is in greater need of
additional pain medication, it is important to be able to adjust
the PCA basal rate, the bolus rate and the bolus amount more
frequently, always taking into account the effect of side effects
and impairment of patient functionalities.
[0007] Infusion modes are programmed into the infusion pump by the
caregiver or physician. In a hospital or other caregiver facility,
a physician or caregiver can visit a patient once or twice a day to
check if the programmed infusion mode, dose and frequency are
providing appropriate relief to the patient. If the patient is
receiving medication at home or away from a caregiver facility,
such visits may be less frequent. In most of the pre-programmed
modes, rechecking the mode, dose and frequency once or twice a day
may be sufficient. If the patient is in the PCA mode, however, the
patient's condition may vary more, requiring more frequent
adjustment and more frequent visits by the physician or caregiver.
If the patient is not able to receive additional adjustments or
visits from the physician or caregiver, whether in the home or the
hospital, the patient may be in extreme pain and may not receive
appropriate pain relief for many hours.
[0008] U.S. Pat. No. 5,643,212 to Coutre et al. discloses an
infusion pump management system in which the patient's
physiological signs are used in a biofeedback loop. The system
evaluates the patient's physiological signs and suggests alternate
infusion treatment based on those signs. The proposed modifications
are then sent to the operator for confirmation. Delivery rate
changes are made by the operator (physician or caregiver), so the
patient must wait until the operator can evaluate the proposed
changes before the patient can receive any relief.
[0009] There is a need for an automatic method of adjusting the
medication level in patient control analgesia taking into account
the patient's pain level, side effects and any impairment of
functionalities. There is a need for an apparatus for automatically
adjusting the medication level in response to input from a patient
regarding his pain level, side effects and impairment of
functionalities, without having to contact the caregiver or
physician. There is a need for a method of automatically adjusting
the medication level in patient control analgesia using a
predetermined set of criteria which is patient specific, yet
provides the patient the ability to have his medication adjusted
without having to contact a caregiver or physician.
SUMMARY OF THE INVENTION
[0010] A preferred embodiment of the invention is directed to a
method and apparatus which captures relevant information pertaining
to pain level, side effects and patient impairment and
automatically adjusts the amount of medication, within a
pre-determined level selected by the patient's physician, to
optimize the treatment of pain and improve the patient's quality of
life.
[0011] Prior to prescribing pain medication to be provided via a
programmable infusion pump, the physician or caregiver must program
the pump for the specific patient. In addition to programming in
the specifics of a PCA treatment, by programming in basal rate,
maximum number of bolus doses and volume amount of each bolus dose,
in accordance with the preferred embodiment of the invention, the
programmable infusion pump includes a routine for modifying the PCA
treatment. The PCA modification routine stores preprogrammed values
of basal rate, bolus number and amounts for the specific patient,
which are input the by physician or caregiver. The routine also
includes a pain relief algorithm which modifies the PCA treatment
in response to input regarding the patient's pain level, side
effects and function impairment.
[0012] Pain level can be determined using either of two methods, or
by a combination of the two methods. In a first method, the
programmable infusion pump stores the number of bolus requests by
the patient and whether or not they resulted in delivery of a bolus
over a prescribed period of time. If the patient makes a
significant number of bolus requests over the maximum permitted in
a short period of time, this is used as an indication that the
patient's pain level is high. A second method of determining pain
level is to query the patient directly and evaluate the patient's
responses. A combination of both methods can also be used.
[0013] Side effect information can be determined in either of two
ways, or by using a combination of the two. In the first method,
the patient is asked various questions about specific side effects.
In a second method, if the patient is in a hospital or other
facility with a caregiver, the caregiver records the patient's
responses to inquiries about side effects on the patient's chart.
The caregiver may also record his observations about the patient's
side effects onto the patient's chart. Data recorded on the
patient's chart can later be input to the programmable infusion
pump. A combination of both methods can also be used.
[0014] Similarly, information regarding impairment of patient
functionality can be input by the patient in response to specific
queries prompted by the infusion pump, or by a caregiver or by a
combination of both.
[0015] After completion of inputting all data, the data is
processed by the algorithm, and the patient's PCA medication rate
is conformed to the algorithm or adjusted if indicated by the
algorithm.
[0016] In an alternative embodiment of the invention, if the
patient's vital signs are being monitored, they can be used to
provide data regarding the side effects and patient
functionalities. Vital sign data can be input to the programmable
infusion pump via a data port, processed by the algorithm and the
patient's PCA medication adjusted.
[0017] These and other features and advantages of the present
invention will be apparent to those of ordinary skill in the art in
view of the detailed description of the preferred embodiment, which
is made with reference to the drawings, a brief description of
which is provided below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a perspective view of an infusion pump embodying
the present invention and a cassette which is insertable into the
pump;
[0019] FIG. 1A is a block diagram showing the connection of the
infusion pump of FIG. 1 to a patient;
[0020] FIG. 2 is a block diagram of the electronic and electrical
components of the infusion pump shown in FIG. 1;
[0021] FIG. 3 is a flowchart of the overall operation of the
infusion pump shown in FIG. 1;
[0022] FIG. 4 is a flowchart of the operating system used by the
infusion pump shown in FIG. 1;
[0023] FIG. 5 is a flowchart of the operation to modify the PCA
programming of the infusion pump shown in FIG. 1;
[0024] FIG. 6 shows sample pain intensity scales suggested by the
Acute Pain Management Guideline Panel;
[0025] FIG. 7 is a flowchart of the operation of the program PCA
mode of the infusion pump shown in FIG. 1; and
[0026] FIG. 8 is a flowchart of the operation of an on-off control
routine of the infusion pump shown in FIG. 1;
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0027] Referring now to the drawings and specifically to FIGS. 1
and 1A, a portable infusion pump embodying the present invention is
shown therein and generally identified by reference numeral 10. The
infusion pump 10 provides liquid medicant to patient 11 via
catheter 13. Bolus cord 15 is connected to pump 10. Patient 11
makes a bolus request by pressing bolus button 17. A signal from
bolus button 17 travels down bolus cord 15 to bolus infusion
request switch 332 (see FIG. 2) where the request is processed by
controller 200 (see FIG. 2).
[0028] The infusion pump 10 provides automatic adjustment of a
patient's pain medication. A cassette 12 is insertable into the
pump 10. The portable pump 10 may be carried in a pouch or other
device (not shown) attached to a patient so that the pump 10 may be
carried wherever the patient goes.
[0029] The infusion pump 10 has a keypad 14 via which a user may
input data and commands, a selectively backlighted, dot matrix or
LCD display 16 for displaying textual-messages to the user, a light
sensor 18 for detecting the level of ambient light, and a pair of
light-emitting diodes (LED) 20, a green LED for indicating the
normal operation of the pump 10 and a red LED for indicating an
alarm or abnormal operating condition of the pump 10. As described
below, the level of the light sensed by the ambient light sensor 18
is used to control when the display 16 is backlighted. A data port
22, which is preferably an RS-232 port, is used to download and
upload data between the pump 10 and a remote controller or other
device. Data port 22 would be used to upload vital sign data from a
vital sign monitor, such as heart rate, respiration rate, for
example.
[0030] A door 30 is pivotally attached to the upper portion of the
infusion pump 10 via a plurality of hinges 32. An underside 33 of
the door 30, which is shown in FIG. 1, has a pair of slots 34
formed therein in which a pair of metal rods 35 are fixed. Each of
the metal rods 35 selectively engages a pair of slidable latching
members (not shown) to retain the door 30 in the closed position
during operation of the pump 10.
[0031] An arcuate metal leaf spring 36 is disposed on the underside
of the door 30. The two ends 37 of the leaf spring 36 are anchored
by a pair of retaining elements 38 fixed to the door 30. When the
cassette 12, in which a flexible silicone tube 40 is disposed, is
inserted into the pump 10 and the door 30 is closed, the leaf
spring 36 makes contact with and applies a downward force on an
upper surface 42 of a vertically movable platen 44. As shown in
FIG. 1, the upper surface 42 of the platen 44 is disposed within an
elongated slot or aperture 43 disposed in the upper surface of the
cassette housing 12. The platen 44 has a lower curved surface 46
against which the flexible tube 40 is pressed by a number of
rollers disposed on a conventional rotary pump wheel (not shown) to
effect peristaltic pumping of liquid through the tube 40.
[0032] The cassette 12 has a flow-stop mechanism 60 that
automatically clamps the flexible tube 40 shut when the cassette 12
is not disposed in the pump 10 with the silicone tube 40 in its
fully engaged position or when the pump door 30 is open. This
prevents an open or uncontrolled liquid path being made available
between the medicant source and the patient. The flow-stop
mechanism 60 has a housing 62.
Infusion Pump Electronics
[0033] Referring to FIG. 2, the infusion pump 10 includes a
controller 200 with a built-in analog-to-digital (A/D) converter
200A, an electrically programmable read-only memory (EPROM) 204
having a built-in input/output (I/O) interface 204A, a
random-access memory (RAM) 208, a real-time clock 210 and the
display 16, all of which are interconnected by a communications bus
212. The display 16 has a backlight 220 which is selectively
activated by an enable signal generated on a line 222
interconnecting the controller 200 and the backlight 220. Both the
RAM 208 and the real-time clock 210 are connected to a battery 214
which supplies power to them only in the absence of system power
(generated by a second battery 282). Since it is always powered,
the RAM 208 is a non-volatile memory.
[0034] The controller 200, which may be a conventional
microcontroller such as an 80C196KB commercially available from
Intel Corporation, controls an audible alarm generator 230 via a
line 232, the LED's 20 via a line 234, and a pump motor signal
amplifier circuit 236 via a line 238. The pump motor signal
amplifier circuit 236 is connected to drive the pump motor 51 which
drives the rotary pump wheel. During normal operation, the
controller 200 also sends a periodic signal to a conventional
watchdog timer 250 via a line 252. If the controller 200 should
fail to transmit the periodic signal to the watchdog timer 250,
which would indicate failure or malfunction of the controller 200,
the watchdog timer 250 transmits a signal via a line 260 to cause
the alarm 230 to sound, transmits a signal via a line 262 to cause
the red LED to be illuminated, and transmits a signal via a line
264 to the amplifier circuit 236 to cause the pump motor 51 to
stop.
[0035] The pump 10 has a number of sensors which sense various
conditions relating to the operation of the pump. These sensors
include an input pressure sensor 270 for detecting the liquid
pressure within the flexible tube 40 at a point upstream of the
rotary pump wheel and an output pressure sensor 272 for detecting
the liquid pressure within the flexible tube 40 at a point
downstream of the rotary pump wheel. The input pressure sensor 270
generates an analog signal, indicative of the input pressure, which
is transmitted to the A/D converter 200A via a line 274. The output
pressure sensor 272 generates an analog signal, indicative of the
output pressure, which is transmitted to the A/D converter 200A via
a line 276. Each of the pressure sensors 270, 272, which detect
occlusions with the flexible tube 40 or the tubing 52, 54 connected
thereto, may be provided in the form of a strain gauge or beam (not
show) which is in contact with the exterior of the flexible tube 40
and a high-gain amplifier (not shown) connected to the strain
beam.
[0036] The pressure sensors 270, 272 are connected to, and receive
power from, a power switch 280 which is connected to a battery 282
through a system power switch 284, a voltage regulator 286, and a
system power line 287. The system power switch 284 selectively
supplies power from the battery 282 to the voltage regulator 286
based on the state of a pump on/off switch 288 connected to the
system power switch 284. The power switch 280 is controlled by the
controller 200 via the bus 212, the I/O interface 204A, and a line
294 which interconnects the I/O interface 204A and the power switch
280.
[0037] The pump 10 has an air-in-line sensor 300, which may be
provided in the form of a conventional piezoelectric transmitter
and receiver (not shown) coupled to a sensing circuit (not shown),
to detect the presence of any significant air bubbles within the
flexible tube 40. The air-in-line sensor 300 receives power from a
power switch 302 which is connected to the system power line 287
and controlled by the controller 200 via a line 304 connected to
the I/O interface 204a.
[0038] The pump 10 has a shaft encoder sensor 308 and a Hall-effect
sensor 310 which receive power from a power switch 312 coupled to
the system power line 287 and controlled by the controller 200 via
a line 314. The shaft encoder sensor 308, which is disposed on the
shaft of the motor 51, may be a two-phase motion sensing encoder
which provides two signal outputs to the controller 200. The
rotational speed of the motor 51 and its direction of rotation are
determined by the controller 200 based upon the rate and phase
relationship between the two signal outputs. The Hall-effect sensor
310 is disposed adjacent the rotary pump wheel and detects magnetic
encoding on the pump wheel for detecting rotation of the wheel. A
cassette sensor 320, which is also connected to the power switch
312, detects the type of cassette which is inserted into the pump
10.
[0039] Referring to FIG. 2, the ambient light sensor 18 is
connected to a power switch 326 which is controlled by the
controller 200 via a line 328 from the I/O interface 204A. Signals
generated by a door-open sensor 330, a bolus infusion request
switch 332, the keypad 14 and the data port 22 are transmitted to
the controller 200 via the I/O interface 204A. Although not shown
in FIG. 2 for purposes of simplicity, the controller 200, the EPROM
204, the RAM 208, and the display 16 are also connected to and
receive power from the system power line 287.
Overall Pump Program Operation
[0040] The operation of the infusion pump 10 is controlled by a
computer program stored in the EPROM 204 and executed by the
controller 200. The programming of the pump is usually performed by
a caregiver following a prescription described by the patient's
physician. In some cases, the patient is allowed to alter certain
parameters of the pump. A flowchart of the overall operation is
illustrated in FIG. 3. Referring to FIG. 3, when the pump 10 is
turned on via the on/off switch 288, at step 402 the pump is
initialized and a test of the pump operation is performed. The pump
10 may be turned off temporarily during an infusion, in which case
the pump 10 may continue the infusion when it is turned back on, as
described below. At step 404, if there is any remaining volume of
liquid to be infused by the pump or any additional time remaining
for an infusion, which would be the case where the pump was
temporarily turned off during an infusion, the program branches to
step 406, where the caregiver is asked, via a message displayed on
the display 16, whether the previous infusion should be resumed. If
the caregiver answers yes (via the keyboard 14), the program
branches to a ready-to-run step 410. If the previous infusion is
not to be resumed, the program branches to step 412.
[0041] The infusion pump 10 has a lockout mode in which the patient
may be prevented from programming the infusion parameters, such as
the volume to be infused or the rate of infusion. For example, the
pump 10 could be programmed by a caregiver to deliver a particular
infusion having a particular flow profile, flow rate, and volume to
be infused. After programming that infusion, the caregiver could
place the pump in lockout mode, which would prevent the patient
from changing any of the infusion parameters. At step 412, if the
pump 10 has been previously placed in lockout mode, the program
branches directly to the ready-to-run step 410, bypassing all
programming steps.
[0042] At step 412, if the pump is not in lockout mode, the program
branches to step 414, at which point the program prompts the
caregiver, via the display 16, to input whether the patient should
be allowed to program the pump during the subsequent infusion. If
the pump is not to be programmable, the program branches to step
416 where a lockout sequence is performed by requesting the
caregiver to input which infusion modes should be locked out. If
the pump is to be programmable by the patient, the program bypasses
step 416.
[0043] The infusion pump 10 has five basic modes of infusion: 1) a
continuous mode in which the pump delivers a single volume at a
single rate; 2) an auto-ramp mode in which the pump delivers liquid
at a rate that gradually increases to a threshold rate, stays
constant at the threshold rate, and then gradually decreases; 3) an
intermittent mode in which the pump delivers discrete liquid
volumes spaced over relatively long periods of time, such as a
liquid volume every three hours; 4) a custom mode in which the pump
can be programmed to deliver a unique infusion rate during each of
25 different time periods; and 5) a pain-controlled analgesic (PCA)
mode during which the pump will periodically infuse boluses of
analgesic in response to periodic requests by the patient, which
requests are made via the bolus-request key 332.
[0044] At step 418, the pump 10 generates on the display 16 the
prompt "Continuous?" to the caregiver. If the caregiver desires to
use the pump in its continuous mode, the caregiver answers "yes"
via the keypad 14, and the program branches to step 420 at which
the continuous mode is programmed by the caregiver by entering a
number of infusion parameters, such as the desired infusion rate,
the volume to be infused, etc. At step 418, if the caregiver does
not want to use the continuous mode, the caregiver answers "No",
and the program branches to step 422. Steps 422-436 are generally
the same as steps 418 and 420, except that the caregiver may be
prompted for different infusion parameters, depending on which of
the five possible infusion modes is selected.
Program PCA Mode
[0045] A flowchart of the operation of the Program PCA mode 436 is
shown in FIG. 7. In Pain Control Analgesic (PCA) mode, the
caregiver programs the patient's algorithm as provided by the
physician (described below), a basal rate which is a continuous
basic rate of drug delivery and a bolus amount which is the
additional drug that can be delivered on top of, or in addition to,
the basal rate at specific time intervals. In step 702, the program
prompts the caregiver to program patient algorithm. In step 704,
the program prompts the caregiver to program the basal rate. The
caregiver inputs an amount to be infused to the patient
continuously. After entering the desired rate, e.g. 10 mg/hr, the
caregiver then enters the total volume and selects "Limit Med. by #
of Dose/hour". The program then prompts the caregiver for the basal
amount in step 706. the caregiver enters the desired value. Then
the program prompts the caregiver for the maximum number of boluses
at step 710. After the caregiver inputs the desired number, the
program stores the programmed values at step 714 and returns to the
main program at step 716.
[0046] Referring back to FIG. 3, after the completion of one of the
steps 420, 424, 428, 432 or 436, the program branches to the
ready-to-run step 410. During the run mode 460, the pump 10 infuses
the patient with a liquid medicant in accordance with the infusion
mode selected at one of steps 418, 422, 426, 430, 434 and the
infusion parameters entered at one of steps 420, 424, 428, 432,
436. The pump 10 remains in the run mode 460 until the hold key is
pressed, as determined at step 462. Upon the occurrence of an alarm
condition, an alarm is reported at step 464.
[0047] At step 462, if the hold key is pressed, the infusion is
stopped at step 466, and the pump 10 waits for the run key to be
pressed at step 468 or the on/off switch to be turned off at step
470.
[0048] Summarizing the operation described above, if the pump is to
be utilized in lockout mode, a caregiver turns the pump on,
programs the desired infusion mode at one of steps 420, 424, 428,
432, 436, and then turns the pump off. The programmed infusion
parameters will be retained in the nonvolatile memory 208. The
caregiver would then turn the pump back on, press the "No" key in
response to the "Programmable?" prompt at step 414, enter the
lockout information at step 416, and then turn the pump off again.
When the patient subsequently turned on the pump to perform the
infusion (after a cassette 12 is primed with the liquid to be
infused and inserted into the pump), the program would proceed from
step 412 directly to the ready-to-run step 410, which would prevent
the patient from altering the infusion parameters.
[0049] If the lockout mode was not utilized, the caregiver or the
patient could turn the pump on, program the desired infusion mode,
and then press the "Run" key to start the infusion without every
turning the pump off.
Pump Operating System
[0050] A flowchart of the operating system 500 of the infusion pump
10 is illustrated in FIG. 4. The operating system 500 determines
how the operations and tasks shown in the flowchart of FIG. 3 are
performed. Referring to FIG. 4, if the pump is not operating in the
run mode 460 as determined at step 502, the program branches to
step 504 where any of the processing tasks of steps 402-436
(including called subroutines) of FIG. 3 may be performed. As
described above, these tasks relate to the initial programming of
the infusion pump 10 and are user-interactive. When there are no
more of such tasks to be performed, for example, when the user has
paused during the programming of the pump or has completed the pump
programming, the program branches to step 506, where the controller
200 is placed in its idle mode, described above, via a software
command. The controller 200 exits the idle mode upon the generation
of an interrupt that is generated at step 508. The interrupt is
periodically generated by the controller 200, for example, every 20
milliseconds.
[0051] Thus, when the pump is not in the run mode 460, the program
cycles through steps 502-508 where it alternately performs at step
504 one or more of the processing tasks shown at steps 402-436 in
FIG. 3 and is idled at step 506 to conserve battery power.
[0052] Under certain conditions, the pump may operate in the sleep
mode described above. The pump may operate in the sleep mode when
it is in the run mode 460 (FIG. 3) and is pumping below a
relatively low infusion rate threshold, such as five
milliliters/hour.
[0053] To deliver such a low infusion rate, the motor 51 is not
activated continuously, but is instead turned on periodically (the
motor 51 has a minimum rate at which it must be driven or else it
will stall) to deliver a relatively small volume of liquid
medicant, 50 microliters for example, and then is turned off. It is
when the motor 51 is turned off when the controller 200 is placed
in the sleep mode. When the programmed infusion rate is below the
threshold, the frequency with which the motor turns on and off is
determined by the programmed infusion rate. If the programmed
infusion rate is above the threshold, the motor 51 will pump
continuously.
[0054] Referring to FIG. 4, at step 510, if the pump is not in a
stealth mode (described below), the program branches to a step 512
where a number of processing tasks relating to the infusion may be
performed. At step 514, the watchdog timer 250 is strobed, and at
step 516 the program determines whether the controller 200 may be
placed in the sleep mode. As described above, the controller 200
may be placed in the sleep mode if the selected infusion rate is
less than a predetermined threshold rate. There are also other
conditions which must be satisfied. For example, the motor 51
cannot be active, an audio beep (in response to a key being
pressed, for example) cannot be active, no timed functions can be
active (such as a timed LED illumination), the backlight 220 cannot
be on, and the display 16 cannot be scrolling text. If these
conditions are satisfied, the program branches to a step 520 where
the power to a number of sensors is turned off, and to step 522
where the controller 200 is placed in its sleep mode.
[0055] The controller 200 remains in the sleep mode until it is
"awakened" by any of three occurrences: 1) any key being pressed,
including the bolus-request key 332; 2) the watchdog timer timing
out; or 3) a one-second strobe generated by the real-time clock
210. In the absence of conditions 1) and 2), the controller 200
will be awakened every second by the strobe from the real-time
clock 210. Upon being awakened, the internal clocks of the
controller 200 are started at step 524, and the program branches to
step 508 where it waits for the next interrupt generated by the
controller 200.
[0056] The infusion pump 10 also has a stealth mode relating to the
intermittent infusion mode of FIG. 3. In this mode, the pump 10
delivers an infusion spaced at relatively large time intervals,
such as minutes or hours. Between infusions, the pump is placed in
a stealth mode in which the controller 200 is put to sleep.
[0057] FIG. 8 illustrates an off-control routine 530 that is
periodically invoked to determine whether the on/off switch 288
(FIG. 2) of the infusion pump 10 has been turned off. In that case,
as determined at step 532, the program branches to a step 534 where
it determines if it is okay to turn the pump off (it is okay to
turn the pump off as long as it is not in the run mode 460). If it
is okay to turn the power off, the program branches to a step 536.
If the pump 10 is not in the intermittent mode as determined at
step 536, the power is turned off. If the pump is in the
intermittent mode, the program branches to step 538, which
determines whether there are any more periodic doses (infusions) to
be made. If there are no more doses, the power is turned off.
[0058] If there is at least one additional dose, the pump 10 is
placed in the stealth mode at step 540. Referring back to step 510
of FIG. 4, if the pump is in the stealth mode, the program branches
to a step 550, which determines whether the next dose in the
intermittent mode is scheduled within the next 30 minutes. If not,
the program branches to steps 520-522 where the controller 200 is
put to sleep.
[0059] If the next dose is within 30 minutes as determined at step
550, the program branches to step 552, where it determines whether
the time until the next dose, or the time after that dose if not
given, is a multiple of ten minutes. If it is, then the program
branches to step 554, where the pump 10 generates an audible beep
to the user as a reminder that the next dose is a multiple of ten
minutes away. Thus, when the intermittent infusion mode is being
used and the pump is in the stealth mode, the patient is given
three audible warnings to reassure or warn the patient that the
next dose is imminent, a first warning at 30 minutes prior to the
dose, a second warning at 20 minutes prior to the dose, and a third
warning at 10 minutes prior to the dose. If the next dose is not
given on schedule, a fourth warning is generated at the time of the
dose, and three additional warnings, spaced 10 minutes apart, are
given after the time for the dose.
Data Storage and Recording
[0060] During programming and operation, the infusion pump 10
automatically records in the memory 204 all significant infusion
data to generate a complete historical data record which can be
later retrieved from the memory 204 and used for various purposes,
including clinical purposes to aid in determining how effective a
particular infusion therapy was and treatment purposes to confirm
that the prescribed infusion was actually delivered.
[0061] The infusion data recorded in the memory 204 is set forth in
Table 1 below. A number of events which trigger the storage of data
are listed in the left-hand column of Table 1, and the infusion
data that is recorded upon the occurrence of each event is listed
in the right-hand column of Table 1. The time at which the infusion
data is recorded, which is determined by the real-time clock 210,
is also stored along with the infusion data.
1 TABLE 1 EVENT DATA RECORDED Power On Date and Time Program
Infusion parameters. See Table 2. Run Infusion parameters. See
Table 2. Hold Total Volume Infused Restart Time of Restart Rate
Changes Total Volume Infused, Rate, Volume Alarms Total Volume
Infused, Alarm Type Infusion Complete Total Volume Infused
Malfunctions Total Volume Infused, Malfunction Type Resume Infusion
parameters. See Table 2. Maintenance Date Date Patient ID Patient
ID Number Serial No. Serial Number Language Change New Language
Lockout Modes Locked Out Pressure Select New Pressure Setting Bolus
Request Given/Not Given, Bolus Amount Titration New Parameters
Power Off Time of Power Off Version No. Software Version Number
[0062] Referring to Table 1, when the power to the infusion pump 10
is turned on, the date and time of the power turn-on is recorded.
When the pump is completely programmed pursuant to one of steps
420, 424, 428, 432, or 436 (FIG. 3), the programmed infusion
parameters are stored along with the time of such storage. The
particular parameters that are stored depend upon which infusion
mode was programmed. Examples of infusion parameters that are
stored for the PCA infusion mode is illustrated in Table 2
below.
2TABLE 2 INFUSION MODE INFUSION PARAMETERS PCA Infusion Mode Basal
Infusion Rate Volume To Be Infused Delay Time Total Bag Volume
Bolus Dose amount Max. No. of Bolus Doses Number of Doses Dose Time
Dose Volume KVO Rate
[0063] When the pump enters the run mode at step 460 (FIG. 3), the
time at which the run mode was begun, along with the parameters
pursuant to which the infusion is performed, are stored. The pump
also stores the time at which the hold key was pressed along with
the total volume infused at the time the hold key was pressed. The
pump stores any infusion rate changes, such as changes caused by
switching from a continuous rate to a keep-vein-open (KVO) rate, or
in the intermittent mode, changing from a KVO rate to a higher
infusion rate, the new rate and the time at which the new rate
started.
[0064] If any alarms are generated, the alarm type, the time at
which the alarm occurred, and the total volume infused at the time
of the alarm are recorded. If the infusion is completed, the
program stores the time at which the infusion was completed along
with the total volume infused. If there is a malfunction, the
malfunction type, the time at which the malfunction occurred, and
the total volume infused at the time of the malfunction are
recorded.
[0065] If the infusion is resumed, when the pump is turned back on
after having been turned off during an infusion, the time at which
the infusion is resumed along with the infusion parameters are
stored. Upon the completion of the programming of a lockout
sequence, the time at which the programming of the lockout was
completed is stored along with the infusion modes that were locked
out. Upon the detection of a bolus request, the time at which the
bolus was requested is stored, along with an indication whether the
bolus was actually given and the amount of the bolus.
Patient Algorithm
[0066] Prior to assigning a particular infusion pump to a patient,
the physician or caregiver programs in the patient's algorithm for
automatically changing his PCA dose. The patient's algorithm
defines the range of values for the basal dose, the bolus dose, the
maximum amount of drug to be administered. The patient algorithm
can increase or reduce the amount or duration of any of the PCA
elements, depending on the patient's pain level, side effects and
any impairment of the patient's functionalities.
[0067] The physician takes into account the patient's condition,
the pain medication being provided and the range of medication to
be provided based on the patient's pain level, side effects and
impairment of functionality. The physician determines the course of
therapy for the individual patient by changing the patient
algorithm. For PCA, the patient algorithm includes a number of
input parameters to control the basal rate and the bolus dose. The
input parameters could include: a) pain level which could be
captured by querying the patient directly or indirectly measuring
the percentage of successful bolus request as discussed below; b)
level of side effect including the frequency and intensity of
vomiting and/or constipation; c) the restoration of physical
function such as the limb movement and d) the effective time when
the algorithm becomes active. The effective time is required to
ensure that the system has adequate time to capture relevant
information about the patient pain level, side effect and the
restoration of bodily functions.
[0068] One embodiment of a patient algorithm for controlling basal
rate and bolus dose is shown in Table 3 and Table 4 below.
3TABLE 3 Input % of Output Successful Restora- % Change % Change
Bolus Side tion of to Basal to Bolus Request Effects Function Rate
Dose 100 No No -30 0 100 No Yes -30 -20 100 Yes No -30 0 100 Yes
Yes -50 -20 50 No No +10 +20 50 No Yes +20 +20 50 Yes No 0 +10 50
Yes Yes 0 +20
[0069]
4TABLE 4 Input Output Restora- % Change % Change Pain Side tion of
to Basal to Bolus Level Effects Function Rate Dose 2 No No -30 0 2
No Yes -30 -20 2 Yes No -30 0 2 Yes Yes -50 -20 10 No No +10 +20 10
No Yes +20 +20 10 Yes No 0 +10 10 Yes Yes 0 +20
[0070] Other values for increasing or decreasing the basal rate may
be used depending on the particular pain medication and other
factors.
Capturing Pain Level Data
[0071] Table 3 requires input on Percent of Successful Bolus
Request, Side Effects and Restoration of Function. As described
below, Percent of Successful Bolus Request data is stored by the
pump along with other pump information. This data can be accessed
from memory. Percent of Successful Bolus Request information is
used as an indirect measure of pain level. If the patient requests
bolus requests after the maximum number has already been
administered, this is an indication that the patient is in pain and
needs either a higher basal rate, higher bolus dose or greater
number of bolus doses, or a combination thereof.
[0072] Alternatively, pain level information can be determined by
querying the patient directly. For example, the patient can be
queried at specific intervals, or whenever the patient requests a
bolus dose, about pain level using a pain scale. Every hour the
pump prompts the patient to enter a pain scale into the pump, based
on a scale of from 0 to 10, with 10 being the highest level of
pain. Instead of the 0 to 10 pain scale, an alternate pain scale
suggested by the Acute Pain Management Guideline Panel is shown in
FIG. 6. The information is stored in pump memory for use by the PCA
mode modification routine. An attending caregiver may also ask the
patient about pain level at regular or other intervals and enter
the information into the patient's chart (for later input into the
pump) or directly into the pump.
Capturing Data on Side Effects
[0073] Information for patient side effects is preferably acquired
by prompting the patient to input responses to a series of specific
questions. For example, for a patient receiving intravenous
medication, the patient could be prompted to answer Yes or No to
questions such as:
[0074] Cognitive Impairment
[0075] Nausea
[0076] For neuraxial medication, the patient could be prompted to
answer Yes or No to questions such as:
[0077] Motor Impairment
[0078] Dizziness
[0079] This information can be requested each time the patient
presses the bolus cord. Alternative methods of acquiring side
effect data can be employed, such as, after a Yes response, asking
the patient to expand on a scale of 0 to 10 for that side effect.
The pump stores the results for use by the PCA mode modification
routine.
Capturing Data on Function Impairment
[0080] As with data on side effects, data pertaining to the
patient's function impairment can be obtained by prompting the
patient to respond to a series of questions. Each time the patient
requests a bolus dose, the pump with respond with a series of
questions that the patient responds to with a Yes or No answer, and
optionally, a rating of from 0 to 10. Examples of questions
include:
[0081] Ability to move lower limbs
[0082] Restoration of bowel motility.
Automatically Modifying the PCA Program
[0083] FIG. 5 shows the routine to modify the PCA programming of
the infusion pump 10. Referring to FIG. 5, the PCA programmed
values can be modified in one of two methods. In the first method,
the PCA programmed values are modified by a patient initiated
request while the pump is in the run mode at step 460. While in the
run mode, the pump controller 200 periodically checks to see if the
patient has initiated a request through bolus cord 15 and bolus
button 17 (applied to bolus request switch 332) at step 180. If the
answer is no, the pump controller 200 checks if a PCA time has
expired. The pump may be programmed to check to see if the PCA
programmed values should be modified on a periodic basis, say every
hour, at step 182. If the answer is no, the routine loops back to
step 460.
[0084] If the answer to step 180 or step 182 is yes, the routine
branches to block 186, the PCA modification routine. In this
preferred routine, the patient is queried at a step 188 on pain
level, side effects and function impairment. Data is stored for use
by the patient algorithm in evaluating whether or not the PCA
programmed values should be changed. At step 190 the routine also
checks stored historical values, such as number of successful bolus
requests over time. At step 192 the routine processes the data
according the patient algorithm and at step 194 modifies the PCA
programmed values and returns to the Run Mode.
[0085] The invention allows the pump to automatically adjust basal
rate and/or bolus rate to alleviate patient pain in the absence of
the caregiver's intervention. The invention also adjusts the basal
rate and quantity of boluses to reduce side effects and restore
patient functionalities, improving the patient's overall quality of
life. Calls to the caregiver by patients in pain can be reduced,
reducing work load on caregivers.
[0086] Modifications and alternative embodiments of the invention
will be apparent to those skilled in the art in view of the
foregoing description. This description is to be construed as
illustrative only, and is for the purpose of teaching those skilled
in the art the best mode of carrying out the invention. The details
of the structure and method may be varied substantially without
departing from the spirit of the invention, and the exclusive use
of all modifications which come within the scope of the appended
claims is reserved.
* * * * *