U.S. patent application number 13/604274 was filed with the patent office on 2012-12-27 for implantable medical device with time for therapeutic output replenishment determination and method therefore.
This patent application is currently assigned to Medtronic, Inc.. Invention is credited to Mark J. Bina, David C. Ullestad.
Application Number | 20120330273 13/604274 |
Document ID | / |
Family ID | 34958812 |
Filed Date | 2012-12-27 |
United States Patent
Application |
20120330273 |
Kind Code |
A1 |
Ullestad; David C. ; et
al. |
December 27, 2012 |
IMPLANTABLE MEDICAL DEVICE WITH TIME FOR THERAPEUTIC OUTPUT
REPLENISHMENT DETERMINATION AND METHOD THEREFORE
Abstract
An implantable medical device for producing a variable
therapeutic output to a patient. A therapeutic output delivery
module requires replenishment following delivery of a predetermined
amount of the therapeutic output. A calculator is responsive to a
measure of an amount of the therapeutic output actually delivered
to the patient for determining a parameter representative of a time
at which the therapeutic output delivery module of the implantable
medical device should be replenished with the therapeutic substance
based at least in part upon the amount obtained from the measure. A
method determines a parameter representative of a time at which a
therapeutic output module of an implantable medical device should
be replenished following delivery of a predetermined amount of
therapeutic output. An amount of the therapeutic output actually
delivered to the patient is measured. The parameter is calculated
based at least in part upon the amount obtained in the measuring
step.
Inventors: |
Ullestad; David C.; (Maple
Grove, MN) ; Bina; Mark J.; (Shoreview, MN) |
Assignee: |
Medtronic, Inc.
|
Family ID: |
34958812 |
Appl. No.: |
13/604274 |
Filed: |
September 5, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10836589 |
Apr 30, 2004 |
8282625 |
|
|
13604274 |
|
|
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Current U.S.
Class: |
604/500 |
Current CPC
Class: |
A61M 5/14276 20130101;
A61M 2209/045 20130101; A61M 2205/3379 20130101; A61M 5/1684
20130101; G16H 20/17 20180101 |
Class at
Publication: |
604/500 |
International
Class: |
A61M 5/168 20060101
A61M005/168 |
Claims
1. A device-implemented method of determining a parameter
representative of a time in the future at which a therapeutic
output module of an implantable medical device implanted in a
patient should be replenished following delivery of a predetermined
amount of therapeutic output, comprising the steps of: measuring an
amount of said therapeutic output actually delivered to said
patient; and calculating said parameter based at least in part upon
said amount obtained in said measuring step.
2. A method as in claim 1 further comprising the step of
communicating said parameter to an external device.
3. A method as in claim 1 wherein said therapeutic output delivery
module comprises a reservoir for holding a therapeutic substance
and a pump operatively coupled to said reservoir for delivering
said therapeutic substance to said patient.
4. A method as in claim 3 wherein said measuring step comprises
measuring an amount of delivery of said pump.
5. A method as in claim 3 wherein said measuring step comprises
measuring a volume of said therapeutic substance.
6. A method as in claim 1 wherein said therapeutic output is
delivered to said patient at a variable rate.
7. A method as in claim 6 wherein said variable rate is at least
partially controlled by said patient.
8. A method as in claim 7 wherein said variable rate is at least
partially determined by a patient-controlled bolus.
9. A device-implemented method of determining an adjusted parameter
representative of a time in the future at which a reservoir of an
implantable drug pump implanted in a patient should be replenished
with a therapeutic substance, comprising the steps of: determining
an initial parameter representative of an initially estimated time
at which said reservoir of said implantable drug pump should be
replenished with said therapeutic substance based at least in part
upon a predicted delivery rate of said therapeutic substance to
said patient; measure an amount based at least in part on a
quantity of said therapeutic substance actually delivered to said
patient; comparing said amount with an amount of said therapeutic
substance expected to have been delivered to said patient based
upon said predicted delivery rate; determining said adjusted
parameter based at least in part upon a result of said comparing
step; and communicating said adjusted parameter to an external
device.
10. A method as in claim 9 further comprising the step of
communicating said parameter to an external device.
11. A method as in claim 9 wherein said measuring step comprises
measuring an amount of delivery of said pump.
12. A method as in claim 9 wherein said measuring step comprises
measuring a volume of said therapeutic substance.
13. A method as in claim 9 wherein said calculating step uses
simple arithmetic.
14. A method as in claim 13 wherein said simple arithmetic
comprises addition and subtraction.
15. A method as in claim 9 wherein said adjusted parameter is
determined by subtracting an amount from said adjusted parameter
based at least in part on said result.
16. A method as in claim 15 wherein said subtracting decrements
said adjusted parameter.
17. A method as in claim 9 wherein said therapeutic output is
delivered to said patient at a variable rate.
18. A method as in claim 17 wherein said variable rate is at least
partially controlled by said patient.
19. A method as in claim 18 wherein said variable rate is at least
partially determined by a patient-controlled bolus.
Description
RELATED APPLICATION
[0001] This application is a division of and claims priority to
U.S. patent application Ser. No. 10/836,589, IMPLANTABLE MEDICAL
DEVICE WITH TIME FOR THERAPEUTIC OUTPUT REPLENISHMENT DETERMINATION
AND METHOD THEREFORE, filed Apr. 30, 2004.
[0002] A portion of the disclosure of this patent document contains
material that is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction by anyone of
the patent document or the patent disclosure, as it appears in the
United States Patent and Trademark Office patent file or records,
but otherwise reserves all copyright rights whatsoever.
FIELD OF THE INVENTION
[0003] The present invention relates to implantable medical devices
and, more particularly to implantable medical devices which need to
be replenished following delivery of a therapeutic output to a
patient.
BACKGROUND OF THE INVENTION
[0004] Implantable medical devices for producing a therapeutic
output to a patient are well known. Such devices include
implantable devices that provide that provide an electrical stimuli
to a patient, e.g., for soft tissue stimulation and/or pain
control. Such devices also include implantable therapeutic
substance delivery devices, e.g., devices capable of delivering a
drug or other analgesia. Such implantable medical devices include
implantable drug infusion pumps, implantable neurostimulators,
implantable cardioverters, implantable cardiac pacemakers,
implantable defibrillators and cochlear implants.
[0005] The therapeutic output, whether it is an electrical
stimulus, a therapeutic substance or other therapeutic output, of a
typical implantable medical device is exhaustible. That is, after
having been implanted and providing a therapeutic output for a
period of time, the medical device may need to be replenished in
order to continue to deliver a therapeutic output. For example, a
therapeutic substance delivery device may need a new supply of
therapeutic substance or the therapeutic substance contained in the
medical device for delivery may need to be replenished. If such a
therapeutic substance is contained in a reservoir, the reservoir
may need to be refilled. As another example, implantable medical
devices generally need electrical power to operate. Such electrical
power may be used to power electrical circuitry which operates the
implantable medical device and/or may be used directly to provide
electrical stimuli to a patient.
[0006] Since a typical implantable medical device has exhaustible
resources, it may be important to ensure that the exhaustible
resource is replenished before the resource has been exhausted in
order to ensure continued, uninterrupted operation of the
implantable medical device. To this end, some implantable medical
devices have a mechanism that assists in determining when the
exhaustible resource is close to being expended so that the
resource may be replenished before exhaustion.
[0007] However, since the medical device is implanted
subcutaneously in the patient, replenishment of the exhaustible
resource may involve a surgical procedure to refill, recharge or
even explant and re-implant the medical device. Thus, replenishment
of an exhaustible resource in an implanted medical device may not
be an act that is taken lightly.
[0008] The time at which an exhaustible resource in an implanted
medical device is replenished can be extremely important. If the
exhaustible resource is not replenished soon enough, the implanted
medical device may stop functioning which could lead to deleterious
and, possibly, disastrous, results. If, however, the exhaustible
resource is replenished too soon, a surgical procedure may need to
be performed before the surgical procedure is needed adding
unnecessary risk, inconvenience and cost and, perhaps, requiring
more surgery than otherwise would optimally be required.
[0009] It is typical to utilize a worst case scenario for
determining when to replenish an exhaustible resource in an
implanted medical device. Since it may be imperative not to allow
an implanted medical device to completely exhaust an exhaustible
resource, and possibly allow the implanted medical device to cease
to perform its therapeutic function. The worst case scenario may
depend upon variables in the construction and operation of the
implanted medical device.
[0010] For example, if a chemical battery is an exhaustible
resource of an implanted medical device, batteries employed in the
construction of the medical device may have a tolerance in
capacity. If so, it is typical to assume that the battery of any
particular implantable medical device contains a battery having the
minimum possible capacity within the tolerances allowed. Further,
it may be typical to assume the most unfavorable tolerances of
power consumption of the components of the implantable medical
device. Still further, it may be typical to assume that the
implanted medical device will generate the maximum possible
stimuli. All of these assumptions taken together can ensure that
the implanted medical device is replenished before it ceases to
function. However, all of these assumptions taken together may also
dictate a replenishment time which is substantially earlier than
may be actually required.
[0011] As another example, if the implantable medical device is
adapted to deliver a therapeutic substance to a patient, the amount
of therapeutic substance actually delivered to the patient may
depend upon many construction variables, including motor
tolerances, and may also depend upon the number and amount of
patient boluses delivered by the implanted medical device. It may
be typical to assume the most unfavorable tolerances for medical
device components and to assume the maximum number and volume of
patient boluses in order to ensure that the implanted medical
device is replenished before it ceases to function. Again however,
all of these assumptions taken together may also dictate a
replenishment time which is substantially earlier than may be
actually required.
[0012] Accordingly, there is a need for an implantable medical
device and method that addresses the above issues.
BRIEF SUMMARY OF THE INVENTION
[0013] The present invention solves these problems by providing an
implantable medical device that can determine with greater accuracy
than was previously possible the time at which the implantable
medical device should be replenished. In an embodiment, the present
invention provides an implantable medical that is responsive to the
actual therapeutic output of the implantable medical device in
order to more accurately determine the optimum replenishment
time.
[0014] In an embodiment, the present invention provides an
implantable medical device for producing a variable therapeutic
output to a patient into which the implantable medical device is
adapted to be implanted. A therapeutic output delivery module is
adapted to be coupled to the patient and to deliver the variable
therapeutic output to patient, the therapeutic output delivery
module requiring replenishment following delivery of a
predetermined amount of the therapeutic output. A measure is
representative of an amount of the therapeutic output actually
delivered to the patient. A calculator is responsive to the measure
for determining a parameter representative of a time at which the
therapeutic output delivery module of the implantable medical
device should be replenished with the therapeutic substance based
at least in part upon the amount obtained from the measure.
[0015] In another embodiment, the present invention provides an
implantable drug pump for delivering a variable amount of a
therapeutic substance to a patient into which the implantable drug
pump is adapted to be implanted. A reservoir holds the therapeutic
substance. A pump is operatively coupled to the reservoir and
adapted to be coupled to the patient to deliver the therapeutic
substance to the patient. A measure determines an amount based at
least in part on an amount of the therapeutic substance actually
delivered to the patient. A calculator is responsive to the measure
for determining a time at which the reservoir of the implantable
drug pump should be replenished with the therapeutic substance
based at least in part upon the amount obtained from the
measure.
[0016] In a preferred embodiment, the therapeutic output delivery
module is a reservoir for holding a therapeutic substance and a
pump operatively coupled to the reservoir for delivering the
therapeutic substance to the patient.
[0017] In a preferred embodiment, the replenishment comprises
replacing at least a portion of the therapeutic output delivery
module.
[0018] In a preferred embodiment, the replenishment comprises
replenishing a power source in the therapeutic output delivery
module.
[0019] In another embodiment, the present invention provides an
implantable medical device for producing a variable therapeutic
output to a patient into which the implantable medical device is
implanted. A therapeutic output delivery module is adapted to be
coupled to the patient and to deliver the variable therapeutic
output to patient, the therapeutic output delivery module requiring
replenishment following delivery of a predetermined amount of the
therapeutic output. A predetermined parameter is representative of
a time at which the therapeutic output delivery module should be
replenished based at least in part upon a predicted delivery rate
of the therapeutic output to the patient. A measure determines an
amount of the therapeutic output actually delivered to the patient.
A comparator is operatively coupled to the predetermined parameter
and to the measure for comparing the amount of the therapeutic
output actually delivered to the patient with an amount of the
therapeutic output expected to have been delivered to the patient
based at least in part upon the predicted delivery rate and
producing a result based thereon. An adjusted parameter is
representative of an adjusted time at which the therapeutic output
delivery module should be replenished based at least in part upon
the result from the comparator.
[0020] In another embodiment, the present invention provides an
implantable drug pump for delivering a variable amount of a
therapeutic substance to a patient into which the implantable drug
pump is implanted. A reservoir holds the therapeutic substance. A
pump is operatively coupled to the reservoir and adapted to be
coupled to the patient to deliver the therapeutic substance to the
patient. A predetermined parameter is representative of a time at
which the reservoir of the implantable drug pump should be
replenished based at least in part upon a predicted delivery rate
of the therapeutic substance to the patient. A measure determines
an amount based at least in part on a quantity of the therapeutic
substance actually delivered to the patient. A comparator is
operatively coupled to the predetermined parameter and to the
counter for comparing the amount with an amount of the therapeutic
substance expected to have been delivered to the patient based at
least in part upon the predicted delivery rate and producing a
result based thereon. An adjusted parameter is representative of an
adjusted time at which the reservoir of the implantable drug pump
should be replenished with the therapeutic substance based at least
in part upon the result from the comparator.
[0021] In a preferred embodiment, a communication module is
operatively coupled to the parameter and capable of communicating
the parameter to an external device.
[0022] In a preferred embodiment, the measure comprises a count of
an amount of delivery of the pump.
[0023] In a preferred embodiment, the measure is a volume of the
therapeutic substance.
[0024] In a preferred embodiment, the therapeutic output or
therapeutic substance is delivered to the patient at a variable
rate.
[0025] In a preferred embodiment, the variable rate is at least
partially controlled by the patient.
[0026] In a preferred embodiment, the variable rate is at least
partially determined by a patient-controlled bolus.
[0027] In a preferred embodiment, the determining is accomplished
periodically.
[0028] In a preferred embodiment, the determining is accomplished
daily.
[0029] In a preferred embodiment, the replenishment comprises
refilling a reservoir with a therapeutic substance.
[0030] In a preferred embodiment, the calculator determines the
parameter using simple arithmetic.
[0031] In a preferred embodiment, the simple arithmetic comprises
addition and subtraction.
[0032] In a preferred embodiment, the adjusted parameter is
determined by subtracting an amount from the adjusted parameter
based at least in part on the result.
[0033] In a preferred embodiment, the subtracting decrements the
adjusted parameter.
[0034] The present invention solves these problems by providing a
method of determining a parameter associated with replenishment of
an implantable medical device with greater accuracy than was
previously possible. In an embodiment, the present invention
provides a method of determining the parameter by being responsive
to the actual therapeutic output of an implantable medical device
in order to more accurately determine the optimum replenishment
time.
[0035] In another embodiment, the present invention provides a
method of determining a parameter representative of a time at which
a therapeutic output module of an implantable medical device
implanted in a patient should be replenished following delivery of
a predetermined amount of therapeutic output. An amount of the
therapeutic output actually delivered to the patient is measured.
The parameter is calculated based at least in part upon the amount
obtained in the measuring step.
[0036] In a preferred embodiment, the parameter is communicated to
an external device.
[0037] In a preferred embodiment, the therapeutic output delivery
module is a reservoir for holding a therapeutic substance and a
pump is operatively coupled to the reservoir for delivering the
therapeutic substance to the patient.
[0038] In another embodiment, the present invention provides a
method of determining an adjusted parameter representative of a
time at which a reservoir of an implantable drug pump implanted in
a patient should be replenished with a therapeutic substance. An
initial parameter representative of an initially estimated time at
which the reservoir of the implantable drug pump should be
replenished with the therapeutic substance based at least in part
upon a predicted delivery rate of the therapeutic substance to the
patient is determined. An amount is measured based at least in part
on a quantity of the therapeutic substance actually delivered to
the patient. The amount is compared with an amount of the
therapeutic substance expected to have been delivered to the
patient based upon the predicted delivery rate. The adjusted
parameter is determined based at least in part upon a result of the
comparing step. The adjusted parameters is communicated to an
external device.
[0039] In a preferred embodiment, the measuring step comprises
measuring an amount of delivery of the pump.
[0040] In a preferred embodiment, the measuring step comprises
measuring a volume of the therapeutic substance.
[0041] In a preferred embodiment, wherein the therapeutic output is
delivered to the patient at a variable rate.
[0042] In a preferred embodiment, the variable rate is at least
partially controlled by the patient.
[0043] In a preferred embodiment, the variable rate is at least
partially determined by a patient-controlled bolus.
[0044] In a preferred embodiment, the calculating step uses simple
arithmetic.
[0045] In a preferred embodiment, the simple arithmetic comprises
addition and subtraction.
[0046] In a preferred embodiment, the adjusted parameter is
determined by subtracting an amount from the adjusted parameter
based at least in part on the result.
[0047] In a preferred embodiment, the subtracting decrements the
adjusted parameter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] FIG. 1 is an exemplary embodiment of the external
programming device and the external patient control communicating
with the pump mechanism via telemetry;
[0049] FIG. 2 depicts exemplary functions of the pump
mechanism;
[0050] FIG. 3 is a partial functional block diagram of implantable
medical device and communication components in accordance with an
embodiment of the present invention;
[0051] FIG. 4 is a flow chart illustrating a preferred embodiment
of the present invention;
[0052] FIG. 5 is a flow chart illustrating an alternative
embodiment of the present invention; and
[0053] FIG. 6 is a function schematic illustrating communication
related to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0054] The entire content of U.S. application Ser. No. 10/836,589,
filed Apr. 30, 2004, is hereby incorporated by reference.
[0055] The present invention has applicability of multiple types of
implantable medical devices including implantable medical devices
providing electrical stimuli, e.g., an electrical stimulus to soft
tissue and implantable medical devices that deliver a therapeutic
substance, e.g., a drug delivery device.
[0056] Although the present invention is described primarily in
terms of an implantable therapeutic substance delivery device and
associated method, it is to be recognized and understood that the
present invention may be equally described in terms of an
implantable medical device delivering electrical stimuli to a
patient and associated method. Both devices provide a therapeutic
output to a patient through a delivery module. A therapeutic
substance delivery device is described primarily in terms of the
reservoir of therapeutic substance as an exhaustible resource. It
is to be recognized and understood that the present invention may
be equally described in terms of power, or another resource, of an
electrical tissue stimulator as an exhaustible resource. The common
thread, of course, is an exhaustible resource related to an
implanted medical device and the need to rather accurately predict
the time of replenishment of the exhaustible resource in order, in
part, to ensure the continued operability of the implanted medical
device and conservation of patient inconvenience, expenditure of
medical resources and elimination of unneeded surgery.
[0057] A typical therapeutic substance delivery device has a
therapeutic output delivery module adapted to provide a therapeutic
output to a patient. An exemplary therapeutic output delivery
module could operate by delivering a therapeutic substance to the
patient. The therapeutic output delivery module could have a
reservoir for holding therapeutic substance such as a drug, e.g.,
an analgesic, a pump for controlling the dispensing of the
therapeutic substance, preferably at a controlled and possibly
variable rate, and a catheter for delivering the dispensed
therapeutic substance to a location in the body of the patient. A
control module in the therapeutic substance delivery device is
operably coupled to the therapeutic output delivery module and
specifies the amount and the rate of delivery of the therapeutic
substance. Typically, the control module is capable of being
programmed, usually by a medical professional. The control module
may allow the possibility of patient boluses. For example, the
patient may optionally administer an additional dose or doses, or
an increased dose or doses, e.g., for pain control. A patient who
can administer optional doses of pain medication may actually use
less medication than patient's who do not have such control.
[0058] An exemplary programmable drug delivery system allowing
patient boluses is illustrated in FIG. 1. An implantable,
programmable pump mechanism 10 has a control system that controls
the operation of the pump mechanism. The control system includes a
microprocessor and a memory programmable with selected functions
for controlling the operation of the pump mechanism. The memory
stores the programs and data related to the operation of the pump
mechanism. The memory is coupled to the microprocessor, which in
turn runs the desired operating programs that control the operation
of the pump mechanism.
[0059] Access to the microprocessor is provided through a
communications port located in the pump mechanism. The
communication port receives and transmits information from/to an
external programming device 12 or an external patient control
device 14 via telemetry. FIG. 1 depicts the pump mechanism 10 and
the external programming device 12 and patient control device 14
communicating via telemetry. This feature allows for the
downloading and uploading of any or all information from the memory
of the microprocessor to the programming devices.
[0060] In FIG. 2, exemplary functions of the control system of the
pump mechanism 10 are generally depicted. The function of the
control system 20 generally include infusion prescription history
21, infusion prescription 22, patient configuration 23, patient
configuration history 24, infusion history 25, event history 26,
time-stamped patient activity 27, patient activity counter 28,
patient control status 29, and infusion control status 30. The
infusion prescription history 21, infusion prescription 22, patient
configuration 23, and patient configuration history 24 are entered
via the programmer 12 and downlinked into the pump mechanism. The
infusion history 25, event history 26, patient activity
time-stamped 27, and patient activity counter 28 are functions of
the pump mechanism that are managed by the pump and are accessible
via the programmer 12. These functions are able to be cleared by
the programmer 12. The patient control status 29 and infusion
control status 30 are also functions of the pump mechanism that are
managed by the pump and are accessible via the programmer 12.
However, these functions are not alterable by the programmer
12.
[0061] Initially, the system of the present invention is presented
to a physician in an initial default state where all pump functions
are disabled. Using the external programming device 12, the
physician programs the initial patient infusion prescription. The
prescription may be a fixed rate prescription that does not vary
over time, unless changed by the physician or patient.
Alternatively, the prescription may be multi-step where the
infusion rate automatically adjusts over time. The infusion
prescription history (a record of a given number of past
prescriptions) is stored in the memory of the pump mechanism and
may be managed and retrieved via the external programming device
12.
[0062] The physician also programs the pump mechanism to have a
specific patient configuration by selecting which pump functions
are enabled and selecting the parameters for each enabled pump
function. If the physician enables a pump function, the physician
must specify all of the programmable parameters associated with
that pump function since the pump assumes no default values. The
patient configuration containing the pump functions and related
parameters is stored in the memory of the pump mechanism and can
only be changed by the physician. The patient configuration can be
read, cleared, or adjusted by the physician using the external
programming device 12.
[0063] When the patient configuration is programmed into the pump
mechanism, the patient configuration is time stamped according to
the pump mechanism's current time/date setting contained in the
pump mechanism's memory. As a result, the physician may easily
identify when the patient configuration was entered or programmed
into the pump mechanism. Should the physician need to enter a new
patient configuration into the pump mechanism, the previous or old
patient configuration is copied and recorded in a patient
configuration history stored in the pump mechanism's memory. Each
time the physician downlinks or programs a new patient
configuration into the pump mechanism, the old or previous patient
configuration, including all time/date stamped information, is
automatically stored in the patient configuration history.
[0064] Depending on the patient configuration prescribed by the
physician, certain pump functions may be available to the patient
via the external patient control device 14. Like the external
programming device 12, the external patient control device 14 is a
hand held controller that communicates with the pump mechanism via
telemetry. The pump functions that the physician may make available
to the patient via the patient control device 14 may include: stop
pump; re-start pump; increase current pump rate; decrease current
pump rate; patient bolus, stop/cancel patient bolus, status
summary; test pump alarm; silence pump alarm; and set event. These
pump functions are explained in greater detail below. Some or all
of these functions are available to the patient and may be used by
the patient to vary their therapy based on their current/planned
activity or personal assessment of "how they are feeling."
[0065] FIG. 3 is a partial block diagram of implantable medical
device 40 which is similar to programmable pump mechanism 10
described above. Basic device components such as those described
with respect to FIG. 1 are also contained in implantable medical
device 40. Similarly, most basic functions such as those described
with respect to FIG. 2 are also contained in implantable medical 40
or associated components such as external programmers and
controllers. FIG. 3, however, describes in more detail components
of implantable medical device 40 that are significantly different
in embodiments of the present and that obtain the considerable
advantages of the present invention. Everything to the right of the
vertical line in FIG. 3 is preferably contained subcutaneously and
everything to the left of the vertical line is expected to be
external.
[0066] Therapeutic output delivery module 42 is a portion of
implantable device 40. It is to be recognized and understood that
implantable medical device also includes other components which are
typically required for operation in an implantable medical device
40 including a power source, control circuitry and communication
circuitry. These components are conventional in nature and are not
specifically illustrated here for clarity of illustration.
[0067] Therapeutic output delivery module 42 in this specific
preferred embodiment is a drug infusion delivery module containing
reservoir 44 for storing a supply of therapeutic substance for
subsequent delivery to a patient and pump 46 for pumping the supply
of therapeutic substance from reservoir 44 through catheter 48 to a
delivery site in a patient. Pump 46, of course, is under control of
electronics (not shown). Reservoir 44, pump 46, catheter 48 and the
remainder of therapeutic output delivery module are conventional in
nature and are well known in the art.
[0068] Measure 50 is operatively coupled to therapeutic output
delivery module 42 and is responsible for measuring, in a
reasonably accurate manner, the amount of therapeutic output, e.g.,
therapeutic substance, actually delivered to a patient. The amount
of therapeutic output actually delivered, of course, can vary
significantly from a predicted, an expected or a worst case of an
amount of therapeutic output. As noted above, the predicted,
expected or worst case amount can be determined by a wide variety
of factors and, given the importance of not running short of
therapeutic output, is generally conservatively determined. For
example, it may be assumed that a patient exercises every possible
bolus that the patient can control at every earliest opportunity
for so doing. Such a determined of an amount of therapeutic output
expended is, of course, conservative and is designed to ensure that
implantable medical device 40 does not exhaust therapeutic output.
However, the actual number of boluses elected by the patient is
often quite fewer than the maximum allowed. If this is the case,
then the amount of therapeutic output actual expended may be much
less than the maximum amount allowed.
[0069] The exact mechanism for measuring the amount of therapeutic
output is determined, at least in part, by the type of therapeutic
output being supplied by therapeutic output delivery module 42. In
the preferred embodiment of a therapeutic substance delivery module
using pump 46, a preferred method is to count the number pump
impulses or pumping steps incurred by pump 46. Since it is known
how much therapeutic substance is delivered for each step of pump
46, in fact this is typically a method used to control the amount
of delivery of output module 42, knowing the number of steps
results in knowing the amount of therapeutic substance delivered.
Alternatively, it may be possible to measure the amount of energy
consumed by pump 46 since each pump step consumes are relatively
constant amount of energy. Also alternatively, any type of flow or
volume meter acting directly on the flow of therapeutic substance
from output module 42 could also be utilized. If therapeutic output
delivery module 42 provides an electrical output signal, it is
possible to measure the amount of energy expended by output module
42, similar to measuring the amount of energy consumed by pump 46
in the example above but more direct. Coulomb counters are well
known and are commonly employed for this purpose. Certainly other
measures of measurement are known and expected without departing
from the scope of the invention.
[0070] Calculator and/or comparator 52 receives the amount of
therapeutic output actually delivered to the patient, or a
relatively close approximation thereto, and, in one embodiment,
calculates a time at which the therapeutic output should be
replenished. By time in this instance it is meant a time in the
future, i.e., a point in the future. This point could be identified
by a specific date, for example, by a month and year, by a year or,
perhaps, even a day and time of day. The granularity of the time of
replenishment can vary by many factors including the overall
lifespan of the therapeutic output before exhaustion. That is, if
therapeutic output is expect to last for years, then a calculation
of replenishment time could reasonably be determined by a month and
year, or by a specific date or range of dates, if desired. The time
of replenishment also depends on the safety margin to be employed
which will vary by type of therapeutic output, the purpose of the
therapeutic output, rate of use, lead time in scheduling
replenishment and physician/clinician comfort in the safety margin.
It is preferred that some reasonable safety reserve of therapeutic
output be retained for safety of the patient. Although it could be,
it is not usually contemplated that the time of replenishment would
coincide with the time of exhaustion.
[0071] Many forms of relatively straight forward calculation
methods are contemplated. For example, since the beginning amount
of therapeutic output can be known (when loaded, for example),
knowing an amount of therapeutic output actually used allows
calculator 52 to determine an amount of therapeutic output
remaining by subtraction. Calculator 52 may then calculate a time
to replenishment by dividing the amount of therapeutic output
remaining (adjusting for a reserve, if desired) by the rate at
which the therapeutic output is being used. The rate used in the
calculation can be a real time actual usage rate based on current
consumption, an average or moving average based on consumption over
a predetermined period of time, e.g., last thirty days, or a
maximum rate at which therapeutic output can be consumed, as
examples. The latter, maximum rate, of course, would again result
in a worst case scenario but will have adjusted for the actual
amount previously consumed. This may result in a much more accurate
calculation of replenishment time than having assumed a worst case
scenario over the entire lifetime of therapeutic output supply. It
is to be recognized and understood, however, that other well known
techniques for calculating remaining life of a consumable object
based on knowing the actual amount of consumable remaining, or a
close approximation thereto, can be used and are within the scope
of the present invention.
[0072] Such calculation can occur in continuously in real time as
new data is available, for example both amount of therapeutic
output remaining and usage rate, or could occur periodically,
either on a pure periodic basis such a daily or after a certain
amount or a certain percentage of therapeutic output is consumed.
These are just examples, of course, and other calculation
iterations are also contemplated.
[0073] In an alternative embodiment, calculator/comparator 52 is
supplied with a predetermined parameter 54 representative of an
expected time of replenishment. Such parameter may be established,
for example, when a supply of therapeutic output is loaded or added
to implantable medical device 40. As an example, if reservoir 44 is
filled with 100 milliliters of therapeutic substance and the worst
case known usage rate, assuming all variables such as number and
volume of boluses, pump variations, power variations, etc., is 0.1
milliliters per day, it can be assumed that in the worst case a
1,000 day supply of therapeutic substance is available. If it is
desired that maintain an ten percent (10%) reserve (as an example
only), then 900 days of therapeutic output would be available
before replenishment. This parameter or a parameter determined in
any other fashion can be used as a predetermined parameter. It is
expected that predetermined parameter will, in fact, have some
relationship to the expected lifetime supply of therapeutic
output.
[0074] Predetermined parameter 54 may be characterized in many
formats. As discussed above, predetermined parameter may be
represented as a period of time, e.g., days, until replenishment.
This information may be useful to a patient in determining when to
schedule an appointment for replenishment. It is preferred,
however, that predetermined parameter to converted to a calendar
day (or week or month) for replenishment. This conversion can be
accomplished in implantable medical device 40 or, preferably, can
simply be supplied to implantable medical device 40, preferably at
or around the time of loading or adding therapeutic output. It is
to be recognized and understood that other forms and formats of
predetermined parameter are also contemplated. For example,
predetermined parameter 54 could be determined at the factory upon
or shortly after manufacture. If the maximum capacity of reservoir
44 is known and the maximum pumping rate of pump 46 is known, then
a worst case scenario for implantable medical device can be
pre-established at or near the time of manufacture.
[0075] It is also contemplated that calculator 52 could first
calculate a time for replenishment and that time could then
subsequently be used as predetermined parameter 54.
[0076] If predetermined parameter 54 is available to
calculator/comparator 52, calculator/comparator 52 may operate as a
comparator. Instead of calculating a new time for replenishment,
calculator/comparator 52 may more simply just adjust existing
parameter 54 based upon the usage rate of therapeutic output
delivery module 42. Using the example from above, the time for
replenishment, i.e., predetermined parameter 54, has been set at
900 days. If it is known that this parameter was initially
calculated based upon a maximum usage rate of 0.1 milliliters per
day, then an actual usage rate of less than 0.1 milliliters per day
can result in an adjustment being made to predetermined parameter
54. For example, every time 0.01 milliliters of therapeutic
substance is saved from being delivered, one (1) day of extra time
to replenishment is gained. In a preferred embodiment, the amount
of therapeutic output per unit time, e.g., every day, is determined
and every time a day's worth of therapeutic output is saved beyond
the assumption, then one (1) day is added to the predetermined
parameter 54. If predetermined parameter 54 is kept in a number of
days to replenishment format, then one is simply added. If
predetermined parameter 54 is kept in a date format, for example,
the date is incremented by one day. Other formats and increments
are contemplated.
[0077] The significant advantage of calculating by incrementation
is that a much simpler calculator 52 is required. Since implantable
medical device 40 has very little space and very little resources,
it is much more practical to equip calculator 52 with an
adder/subtractor than with a multiplier/divider.
[0078] The incremented or adjusted parameter 56 can be stored
separately as illustrated in FIG. 3 or, alternatively, the adjusted
parameter 56 can simply write over or otherwise replace
predetermined parameter 54. In this case, adjusted parameter 56
would simply take the place of predetermined parameter 54 for all
subsequent calculations (additions).
[0079] Communications module 58 is used to communicate, for example
by telemetry, with an external device 60 used to inform the patient
or medical professional or care giver of the time for
replenishment. External device 60 could be any sort of conventional
display, for example, or other communication tool. It is also
contemplated that communication could be transcutaneous as, for
example, by audible signals generated directly by communications
module 58 and heard externally. Communication is conventional in
nature and is well known in the art.
[0080] FIG. 4 is a flow chart illustrating an embodiment of the
present invention. Implantable medical device 40 is programmed
(110) with a delivery prescription including a base reference
volume per day. Implantable medical device (112) is also programmed
with a "Next Refill Date" based upon average daily infusion volume.
The actual volume delivered is counted (114), e.g., by counting
steps of pump 46, to determine the actual volume delivered. The
actual volume delivered is compared (116) with a reference volume
based on the average daily rate. The difference is accumulated
(118) is updated on a periodic basis, e.g., continuously or daily.
A comparison is made (120) to see if the accumulated difference is
equal or greater to the reference volume per day. If not, the
actual volume continues to be counted (114). If it is, the "Next
Refill Date" is updated, e.g., incremented (122). The process then
returns to counting (114) the actual volume.
[0081] FIG. 5 is a flow chart illustrating an embodiment of the
present invention in a different format. The amount of therapeutic
output actually delivered to a patient is measured (210). This
measurement (210) can be obtained either from measuring (212) the
operation of pump 46 or from measuring (214) the volume of
therapeutic substance, as examples. A replenishment parameter is
calculated (216) based upon the measured (210) amount. A parameter
representative of a time of replenishment is determined (218). The
parameter is communicated (220) to an external device or an
external person.
[0082] FIG. 6 illustrates functional components beyond implantable
medical device 40 and illustrates the cooperation and communication
between various components and various individuals involved in the
care of the patient. External programming device 12 can be used by
a medical professional, e.g., a physician or clinician, to
initially program implantable medical device 40 establishing a
"Next Refill Date" and a "Reference Volume Per Day" (collectively
62). The patient interacts with implantable medical device 40,
e.g., by self-administering boluses, with external patient control
device 14 using patient activity controls 64. Patient also has
available a patient status display 66 indicating the adjusted
refill date.
[0083] Implantable medical device 40 can communicate with home
computer 68 by any of a variety of well established communication
techniques such as the Blue Tooth communication protocol. Home
computer 68 can update the physician's external programming device
12 through of a number of established communication protocols
including internet and dial-up telephone access using telephones 70
and 72 and telephone network 74. Among the information that can be
transmitted to the physician via external programming device 12 (or
other device capable of communicating with the physician) is pump
status information 76 including the adjusted refill date (so the
physician can contact the patient and schedule a refill
appointment), the accumulated difference volume and the volume
delivered in a unit of time, e.g., volume delivered daily.
[0084] Thus, embodiments of the invention are disclosed. One
skilled in the art will appreciate that the present invention can
be practiced with embodiments other than those disclosed. The
disclosed embodiments are presented for purposes of illustration
and not limitation, and the present invention is limited only by
the claims that follow.
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