U.S. patent application number 15/723231 was filed with the patent office on 2018-02-15 for method and system for closed-loop control of an artificial pancreas.
The applicant listed for this patent is Animas Corporation. Invention is credited to Daniel FINAN, Thomas MCCANN.
Application Number | 20180043095 15/723231 |
Document ID | / |
Family ID | 50473758 |
Filed Date | 2018-02-15 |
United States Patent
Application |
20180043095 |
Kind Code |
A1 |
FINAN; Daniel ; et
al. |
February 15, 2018 |
METHOD AND SYSTEM FOR CLOSED-LOOP CONTROL OF AN ARTIFICIAL
PANCREAS
Abstract
Methods and systems for controlling an insulin pump in response
to glucose measurements are responsive to a base insulin delivery
profile and a temporary insulin delivery profile. These can be
used, e.g., to control blood glucose level of a subject using a
continuous glucose monitor and an insulin infusion pump. During a
selected time range, an insulin amount for the pump to supply is
determined using the temporary insulin delivery profile. Outside
that time range, the insulin amount is determined using the base
insulin delivery profile. The temporary insulin delivery profile
can specify an exact amount to be supplied (a "hard" profile), a
nominal amount to be supplied if doing so does not drive glucose
out of a desired zone ("soft"), or a soft profile with a minimum
amount of insulin to be delivered ("semi-soft").
Inventors: |
FINAN; Daniel;
(Philadelphia, PA) ; MCCANN; Thomas; (Horsham,
PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Animas Corporation |
West Chester |
PA |
US |
|
|
Family ID: |
50473758 |
Appl. No.: |
15/723231 |
Filed: |
October 3, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13834571 |
Mar 15, 2013 |
9795737 |
|
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15723231 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 2205/3592 20130101;
A61M 2209/01 20130101; A61B 5/14532 20130101; A61M 2205/50
20130101; A61M 2205/3561 20130101; G16H 40/67 20180101; G16H 50/50
20180101; A61M 5/1723 20130101; A61M 2205/3553 20130101; A61M
2205/502 20130101; A61M 2230/201 20130101; A61M 2005/14296
20130101; A61M 5/14244 20130101; A61M 2205/52 20130101; A61M
2205/3584 20130101; G16H 20/17 20180101; A61B 5/4839 20130101; G06F
19/3468 20130101 |
International
Class: |
A61M 5/172 20060101
A61M005/172; G06F 19/00 20110101 G06F019/00; A61B 5/145 20060101
A61B005/145; A61B 5/00 20060101 A61B005/00; A61M 5/142 20060101
A61M005/142 |
Claims
1. A method to control an insulin infusion pump responsive to a
controller that receives data from a glucose sensor, the method
comprising: measuring a glucose level of a physiological fluid from
a user with the glucose sensor; and via the controller,
automatically: receiving, from the glucose sensor, respective
glucose level measurements for each time interval of a series of
discrete time intervals; receiving a temporary insulin delivery
profile extending over a selected time range of the time intervals;
providing a signal indicating receipt of the temporary insulin
delivery profile; determining a candidate insulin delivery amount
for a selected one of the time intervals based on a model
predictive controller that: predicts an excursion of the glucose
level from a selected target glucose range using at least some of
the glucose measurements; computes an estimated insulin delivery
amount; and adjusts the estimated insulin delivery amount to
provide the candidate insulin delivery amount, the adjustment
performed in accordance with the predicted excursion a base insulin
delivery profile when the selected time interval is outside of the
selected range, and in accordance with the predicted excursion and
with the temporary insulin delivery profile when the selected time
interval is within the selected range; determining an approved
insulin delivery amount from the candidate insulin delivery amount;
and commanding the infusion pump to deliver the approved insulin
delivery amount.
2.-21. (canceled)
22. The method of claim 1, wherein receiving the temporary insulin
delivery profile comprises receiving a profile modifier and
applying the profile modifier to the base insulin delivery profile
to produce the temporary insulin delivery profile.
23. The method of claim 1, wherein the adjustment comprises
adjusting the estimated delivery amount in accordance with the
predicted excursion and the temporary insulin delivery profile and
constraining the calculated insulin delivery amount to be at least
a difference between the temporary insulin delivery profile and the
base insulin delivery profile in the selected time interval when
the selected time interval is within the selected range.
24. The method of claim 1, wherein determining the approved insulin
delivery amount comprises providing the candidate insulin delivery
amount as the approved insulin delivery amount.
25. The method of claim 1, wherein determining the approved insulin
delivery amount comprises reducing the candidate delivery amount to
provide the approved insulin delivery amount according to a safety
model.
26. The method of claim 1, wherein the temporary insulin delivery
amount defines a first subrange and a second subrange of the
selected time range and specifies a higher rate of insulin delivery
in the first subrange and a lower rate of insulin delivery in the
second subrange.
27. The method of claim 1, further comprising receiving an
activation signal and, in response to the activation signal,
retrieving the stored base insulin delivery profile and retrieving
or determining the insulin delivery amount.
28. A method to control an insulin infusion pump responsive to a
controller that receives data from a glucose sensor, the method
comprising: measuring a glucose level of a physiological fluid from
a user with the glucose sensor; and via the controller,
automatically: receiving, from the glucose sensor, respective
glucose level measurements for each time interval of a series of
discrete time intervals; receiving a temporary insulin delivery
profile extending over a selected time range of the time intervals;
calculating a candidate insulin delivery amount for a selected one
of the time intervals based on a model predictive controller that:
when the selected time interval is outside the selected range,
predicts an excursion of the glucose level from a selected target
glucose range using at least some of the glucose measurements;
computes an estimated insulin delivery amount; and adjusts the
estimated insulin delivery amount to provide the candidate insulin
delivery amount, the adjustment performed in accordance with the
predicted excursion and a base insulin delivery profile; and when
the selected time interval is in the selected range, retrieves the
candidate insulin delivery amount for the selected time interval
from the temporary insulin delivery profile; determining an
approved insulin delivery amount based on the candidate insulin
delivery amount; and commanding the infusion pump to deliver the
approved insulin delivery amount.
29. The method of claim 28, wherein determining the approved
insulin delivery amount comprises using a safety model to determine
whether a hypoglycemic excursion is predicted and, if so, reducing
the candidate delivery amount to provide the approved insulin
delivery amount.
Description
BACKGROUND
[0001] Diabetes mellitus is a chronic metabolic disorder caused by
an inability of the pancreas to produce sufficient amounts of the
hormone insulin, resulting in the decreased ability of the body to
metabolize glucose. This failure leads to hyperglycemia, i.e. the
presence of an excessive amount of glucose in the blood plasma.
Persistent hyperglycemia and/or hypoinsulinemia has been associated
with a variety of serious symptoms and life-threatening long-term
complications such as dehydration, ketoacidosis, diabetic coma,
cardiovascular diseases, chronic renal failure, retinal damage and
nerve damages with the risk of amputation of extremities. Because
restoration of endogenous insulin production is not yet possible, a
permanent therapy is necessary which provides constant glycemic
control in order to always maintain the level of blood glucose
within normal limits. Such glycemic control is achieved by
regularly supplying external insulin to the body of the patient to
thereby reduce the elevated levels of blood glucose.
[0002] External biologic agents such as insulin have commonly been
administered as multiple daily injections of a mixture of rapid-
and intermediate-acting drugs via a hypodermic syringe. It has been
found that the degree of glycemic control achievable in this way is
suboptimal because the delivery is unlike physiological hormone
production, according to which hormone enters the bloodstream at a
lower rate and over a more extended period of time. Improved
glycemic control may be achieved by the so-called intensive hormone
therapy which is based on multiple daily injections, including one
or two injections per day of a long acting hormone for providing
basal hormone and additional injections of rapidly acting hormone
before each meal in an amount proportional to the size of the meal.
Although traditional syringes have at least partly been replaced by
insulin pens, the frequent injections are nevertheless very
inconvenient for the patient, particularly those who are incapable
of reliably self-administering injections.
[0003] Substantial improvements in diabetes therapy have been
achieved by the development of drug delivery devices that relieve
the patient of the need for syringes or drug pens and the need to
administer multiple daily injections. The drug delivery device
allows for the delivery of a drug in a manner that bears greater
similarity to the naturally occurring physiological processes and
can be controlled to follow standard or individually-modified
protocols to give the patient better glycemic control.
[0004] In addition, delivery directly into the intraperitoneal
space or intravenously can be achieved by drug delivery devices.
Drug delivery devices can be constructed as an implantable device
for subcutaneous arrangement or can be constructed as an external
device with an infusion set for subcutaneous infusion to the
patient via the transcutaneous insertion of a catheter, cannula or
a transdermal drug transport such as through a patch. External drug
delivery devices are mounted on clothing, hidden beneath or inside
clothing, or mounted on the body, and are generally controlled via
a user interface built in to the device or arranged on a separate
remote device.
[0005] Blood or interstitial glucose monitoring is required to
achieve acceptable glycemic control. For example, delivery of
suitable amounts of insulin by the drug delivery device requires
that the patient frequently determine his or her blood glucose
level and manually input this value into a user interface for the
external pumps. The user interface or a corresponding controller
then calculates a suitable modification to the default or currently
in-use insulin delivery protocol, i.e., dosage and timing, and
subsequently communicates with the drug delivery device to adjust
its operation accordingly. The determination of blood glucose
concentration is typically performed by means of an episodic
measuring device such as a hand-held electronic meter which
receives blood samples via enzyme-based test strips and calculates
the blood glucose value based on the enzymatic reaction. Throughout
this disclosure, the terms "patient," "subject," and "user" (i.e.,
user of a drug delivery device) are used interchangeably.
[0006] Continuous glucose monitoring (CGM) has also been utilized
over the last twenty years with drug delivery devices to allow for
closed loop control of the insulin(s) being infused into the
diabetic patients. To allow for closed-loop control of the infused
insulins, proportional-integral-derivative ("PID") controllers have
been utilized with mathematical model of the metabolic interactions
between glucose and insulin in a person. The PID controllers can be
tuned based on simple rules of the metabolic models. However, when
the PID controllers are tuned or configured to aggressively
regulate the blood glucose levels of a user, overshooting of the
set level can occur, which is often followed by oscillations, which
is highly undesirable in the context of regulation of blood
glucose. Model predictive controllers ("MPC") have also been used.
The MPC controller has been demonstrated to be more robust than PID
because MPC considers the near future effects of control changes
and constraints in determining the output of the MPC, whereas PID
typically involves only past outputs in determining future changes.
MPC therefore is more effective than PID in view of the complex
interplay between insulin, glucagon, and blood glucose. Constraints
can be implemented in the MPC controller such that MPC prevents the
system from running away when a control limit has been reached. For
example, some schemes do not deliver any glucose during a
hypoglycemic excursion. Another benefit of MPC controllers is that
the model in the MPC can, in some cases, theoretically compensate
for dynamic system changes whereas a feedback control, such as PID
control, such dynamic compensation would not be possible.
[0007] Additional details of the MPC controllers, variations on the
MPC and mathematical models representing the complex interaction of
glucose and insulin are shown and described in the following
documents: [0008] U.S. Pat. No. 7,060,059; [0009] US Patent
Application Nos. 2011/0313680 and 2011/0257627, [0010]
International Publication WO 2012/051344, [0011] Percival et al.,
"Closed-Loop Control and Advisory Mode Evaluation of an Artificial
Pancreatic .beta. Cell: Use of Proportional-Integral-Derivative
Equivalent Model-Based Controllers" Journal of Diabetes Science and
Technology, Vol. 2, Issue 4, July 2008. [0012] Paola Soru et al.,
"MPC Based Artificial Pancreas; Strategies for Individualization
and Meal Compensation" Annual Reviews in Control 36, p. 118-128
(2012), [0013] Cobelli et al., "Artificial Pancreas: Past, Present,
Future" Diabetes Vol. 60, November 2011; [0014] Magni et al.,
"Run-to-Run Tuning of Model Predictive Control for Type 1 Diabetes
Subjects: In Silico Trial" Journal of Diabetes Science and
Technology, Vol. 3, Issue 5, September 2009. [0015] Lee et al., "A
Closed-Loop Artificial Pancreas Using Model Predictive Control and
a Sliding Meal Size Estimator" Journal of Diabetes Science and
Technology, Vol. 3, Issue 5, September 2009; [0016] Lee et al., "A
Closed-Loop Artificial Pancreas based on MPC: Human Friendly
Identification and Automatic Meal Disturbance Rejection"
Proceedings of the 17.sup.th World Congress, The International
Federation of Automatic Control, Seoul Korea Jul. 6-11, 2008;
[0017] Magni et al., "Model Predictive Control of Type 1 Diabetes:
An in Silico Trial" Journal of Diabetes Science and Technology,
Vol. 1, Issue 6, November 2007; [0018] Wang et al., "Automatic
Bolus and Adaptive Basal Algorithm for the Artificial Pancreatic
.beta.-Cell" Diabetes Technology and Therapeutics, Vol. 12, No. 11,
2010; and [0019] Percival et al., "Closed-Loop Control of an
Artificial Pancreatic .beta.-Cell Using Multi-Parametric Model
Predictive Control" Diabetes Research 2008.
[0020] All articles or documents cited in this application are
hereby incorporated by reference into this application as if fully
set forth herein.
[0021] Drug delivery devices generally provide insulin at a "basal
rate," i.e., provide a certain amount of insulin every few minutes
in a pre-programmed, daily pattern. Some drug delivery devices also
permit the user to specify a "temporary basal," in which the normal
daily cycle is altered for a selected length of time.
[0022] Some drug delivery devices permit the user to manually
request that a "bolus," a specified amount of insulin, be delivered
at a specified time. For example, before a meal, the user can
request a bolus of additional insulin be delivered to process the
glucose produced by digestion of the meal. Some drug delivery
devices permit the specified amount to be delivered over a period
of time rather than all at once; time-extended delivery is referred
to as an "extended bolus."
SUMMARY OF THE DISCLOSURE
[0023] However, in prior schemes, temporary basals and extended
boluses are manually-requested and manually-controlled. In order to
obtain the desired benefit from these schemes, users are required
to: (a) measure their blood glucose, (b) know the effect of insulin
on blood glucose ("insulin sensitivity factor" or "ISF"), (c) know
how many grams of carbohydrates they are eating, (d) know how much
insulin is required for a given amount of carbohydrate
("insulin-to-carbohydrate ratio"), (e) know the effects of exercise
and other activities on their blood glucose, and (f) program the
pump correspondingly. These five factors are merely one example
that users of insulin therapy have to contend with. Inaccurate
information in any of these categories can lead to glucose
excursions if, e.g., the user specifies too large or too small a
bolus for a given meal.
[0024] Moreover, glucose measurements in the body show significant
variability due to frequent changes in the glucose level and
variability in the measurement instruments. Control techniques
tuned to appropriately respond to this variability may not be able
to respond correctly in the presence of glucose transients (high or
low) resulting from temporary basals or extended boluses.
Accordingly, there is a continuing need for a way of delivering an
appropriate amount of insulin based on continuous glucose
measurements, and of providing temporary-basal and extended-bolus
functionality that does not negatively affect the controller while
maintaining safeguards on blood glucose level.
[0025] In one aspect, therefore, applicants have devised a method
to control an infusion pump responsive to a controller that
receives data from a glucose sensor. The method can be achieved by
measuring a glucose level of a physiological fluid from a user with
the glucose sensor and automatically performing the following steps
using the controller: [0026] receiving from the glucose sensor
respective glucose level measurements for each time interval of a
series of discrete time intervals; [0027] receiving a temporary
insulin delivery profile extending over a selected time range of
the time intervals; [0028] calculating a candidate insulin delivery
amount for a selected one of the time intervals based on a model
predictive controller that: [0029] predicts an excursion of the
glucose level from a selected target glucose range using at least
some of the glucose measurements; [0030] computes an estimated
insulin delivery amount; and [0031] adjusts the estimated insulin
delivery amount to provide the candidate insulin delivery amount,
the adjustment performed in accordance with the predicted
excursion, the base insulin delivery profile, or, if the selected
time interval is in the selected range, the temporary insulin
delivery profile; [0032] determining an approved insulin delivery
amount from the candidate insulin delivery amount; and [0033]
commanding the infusion pump to deliver the approved insulin
delivery amount.
[0034] In another aspect, applicants have also devised a method to
control an infusion pump responsive to a controller that receives
data from a glucose sensor. The method can be achieved by measuring
a glucose level of physiological fluid from a user with the glucose
sensor and performing the following steps using the controller:
[0035] receiving from the glucose sensor respective glucose level
measurements for each time interval of a series of discrete time
intervals; [0036] receiving a temporary insulin delivery profile
extending over a selected time range of the time intervals; [0037]
calculating a candidate insulin delivery amount for a selected one
of the time intervals based on a model predictive controller that:
[0038] if the selected time interval is outside the selected range,
[0039] predicts an excursion of the glucose level from a selected
target glucose range using at least some of the glucose
measurements; [0040] computes an estimated insulin delivery amount;
and [0041] adjusts the estimated insulin delivery amount to provide
the candidate insulin delivery amount, the adjustment performed in
accordance with the predicted excursion and the base insulin
delivery profile; and [0042] if the selected time interval is in
the selected range, retrieves the candidate insulin delivery amount
for the selected time interval from the temporary insulin delivery
profile; [0043] determining an approved insulin delivery amount
from the candidate insulin delivery amount; and [0044] commanding
the infusion pump to deliver the approved insulin delivery
amount.
[0045] In yet a further aspect, applicants have also devised an
apparatus for the delivery of insulin. The apparatus may include
the following components: [0046] a) a glucose monitor adapted to
measure respective glucose levels of a subject at discrete time
intervals and provide respective glucose measurement data
indicating each measured glucose level; [0047] b) an insulin
infusion pump configured to deliver insulin in response to a
delivery control signal; [0048] c) a memory configured to store a
base insulin delivery profile; [0049] d) an interface adapted to
selectively receive a temporary insulin delivery profile extending
over a selected time range of the time intervals and to provide a
first signal indicating whether the temporary insulin delivery
profile was received; and [0050] e) a controller adapted to, for
each of a plurality of the discrete time intervals: [0051] i)
receive the glucose measurement data for that time interval from
the glucose monitor; [0052] ii) determine an insulin delivery
amount for that time interval using model predictive control based
on a selected target glucose concentration range, the received
glucose measurement data, the stored base insulin delivery profile,
or, in response to the first signal and if that time interval is in
the selected time range, the received temporary insulin delivery
profile; and [0053] iii) provide to the insulin infusion pump a
delivery control signal corresponding to the determined insulin
delivery amount, whereby a corresponding amount of insulin is
delivered.
[0054] In another aspect, there is provided apparatus for the
delivery of insulin, the apparatus. The apparatus may include the
following components: [0055] a) a glucose monitor adapted to
measure respective glucose levels of a subject at discrete time
intervals and provide respective glucose measurement data
indicating each measured glucose level; [0056] b) an insulin
infusion pump configured to deliver insulin in response to a
delivery control signal; [0057] c) a memory configured to store a
base insulin delivery profile; [0058] d) an interface adapted to
receive a temporary insulin delivery profile extending over a
selected time range of the time intervals; and [0059] e) a
controller adapted to, for each of a plurality of the discrete time
intervals: [0060] i) receive the glucose measurement data for that
time interval from the glucose monitor; [0061] ii) if that time
interval is in the selected time range, retrieve a corresponding
insulin delivery amount from the temporary insulin delivery
profile, or else determine an insulin delivery amount for that time
interval using model predictive control based on a selected target
glucose concentration range, the received glucose measurement data,
and the base insulin delivery profile; and [0062] iii) provide to
the insulin infusion pump a delivery control signal corresponding
to the insulin delivery amount, whereby a corresponding amount of
insulin is delivered.
[0063] These aspects provide increased user control over insulin
level by permitting temporary basals and extended boluses to be
specified without requiring complex insulin- and glucose-level
calculations. In various aspects, temporary basals and extended
boluses are handled by a model predictive controller just as
standard basals are, reducing the likelihood of model-induced
insulin transients.
[0064] Accordingly, in any of the aspects described earlier, the
following features may also be utilized in various combinations
with the previously disclosed aspects. For example, the step of
receiving a temporary insulin delivery profile may include
receiving a profile modifier and applying the profile modifier to
the base insulin delivery profile to produce the temporary insulin
delivery profile; the adjustment may include: if the selected time
interval is in the selected range, adjusting the estimated delivery
amount in accordance with the predicted excursion and the temporary
insulin delivery profile; and if the selected time interval is not
in the selected range, adjusting the estimated delivery amount in
accordance with the predicted excursion and the base insulin
delivery profile; alternatively, the adjustment may include: if the
selected time interval is in the selected range, adjusting the
estimated delivery amount in accordance with the predicted
excursion and the temporary insulin delivery profile and
constraining the calculated insulin delivery amount to be at least
a difference between the temporary insulin delivery profile and the
base insulin delivery profile in the selected time interval; and if
the selected time interval is not in the selected range, adjusting
the estimated delivery amount in accordance with the predicted
excursion and the base insulin delivery profile; the
determining-approved-amount step may include providing the
candidate insulin delivery amount as the approved insulin delivery
amount; alternatively, the determining-approved-amount step may
include reducing the candidate delivery amount to provide the
approved insulin delivery amount according to a safety model; the
temporary insulin delivery profile may include former and latter
subranges of the selected time range and specifies higher amounts
or rates of insulin delivery in the former subrange than in the
latter subrange; the determining-approved-amount step may include
using a safety model to determine whether a hypoglycemic excursion
is predicted and, if so, reducing the candidate delivery amount to
provide the approved insulin delivery amount. Furthermore, the
interface can be adapted to receive the temporary insulin delivery
profile by receiving change information and modifying the stored
base insulin delivery profile in the selected time range according
to the change information to provide the temporary insulin delivery
profile; the controller may be adapted to determine the insulin
delivery amount for a selected time interval using: (a) if the
temporary insulin delivery profile was not received or the selected
time interval is outside the selected time range, the selected
target glucose concentration range, the received glucose
measurement data, the stored base insulin delivery profile; (b)
otherwise, the selected target glucose concentration range, the
received glucose measurement data, and the received temporary
insulin delivery profile; the controller can further be adapted to,
in response to the first signal and if a selected time interval is
in the selected time range, constrain the determined insulin
delivery amount for the selected time interval to be at least a
difference between respective values of the temporary insulin
delivery profile and the stored base insulin delivery profile for
the selected time interval; the controller can further be adapted
to: a) predict an excursion of a glucose level of the subject from
the selected target glucose range using a safety model and at least
some of the glucose measurement data for a plurality of the time
intervals; and b) reduce the determined insulin delivery amount
according to the predicted excursion; the temporary insulin
delivery profile may include former and latter subranges of the
selected time range and specifies higher amounts or rates of
insulin delivery in the former subrange than in the latter
subrange; the glucose monitor may include a plurality of glucose
sensors; the interface can further be adapted to provide an
activation signal and the controller, in response to the activation
signal, retrieves the stored base insulin delivery profile and
retrieves or determines the insulin delivery amount; the controller
can further be adapted to: a) predict an excursion of a glucose
level of the subject from the selected target glucose range using a
safety model and at least some of the glucose measurement data for
a plurality of the time intervals; and b) reduce the determined
insulin delivery amount according to the predicted excursion; the
glucose monitor may include a plurality of glucose sensors; and the
interface can further be adapted to provide an activation signal
and the controller, in response to the received activation signal,
to retrieve the stored base insulin delivery profile and retrieve
or determine the insulin delivery amount.
[0065] These and other embodiments, features and advantages will
become apparent to those skilled in the art when taken with
reference to the following more detailed description of various
exemplary embodiments of the invention in conjunction with the
accompanying drawings that are first briefly described.
BRIEF DESCRIPTION OF THE DRAWINGS
[0066] The accompanying drawings, which are incorporated herein and
constitute part of this specification, illustrate presently
preferred embodiments of the invention, and, together with the
general description given above and the detailed description given
below, serve to explain features of the invention (wherein like
numerals represent like elements).
[0067] FIG. 1 illustrates the system in which a controller for the
pump or glucose monitor(s) is separate from both the infusion pump
and the glucose monitor(s) and in which a network can be coupled to
the controller to provide near real-time monitoring.
[0068] FIG. 2 is a schematic of a control system for managing blood
glucose using an insulin pump.
[0069] FIGS. 3 and 4 are examples of insulin delivery profiles
according to various aspects.
[0070] FIG. 5 is a flowchart illustrating exemplary methods of
controlling an infusion pump.
[0071] FIG. 6 is an example of insulin delivery profiles according
to various aspects.
[0072] FIG. 7 is a flowchart of ways of controlling an infusion
pump according to various aspects.
[0073] FIG. 8 shows various embodiments of apparatus for the
delivery of insulin.
MODES FOR CARRYING OUT THE INVENTION
[0074] The following detailed description should be read with
reference to the drawings, in which like elements in different
drawings are identically numbered. The drawings, which are not
necessarily to scale, depict selected embodiments and are not
intended to limit the scope of the invention or the attached
claims.
[0075] As used herein, the terms "about" or "approximately" for any
numerical values or ranges indicate a suitable dimensional
tolerance that allows the part or collection of components to
function for its intended purpose as described herein. In addition,
as used herein, the terms "patient," "host," "user," and "subject"
refer to any human or animal subject and are not intended to limit
the systems or methods to human use, although use of the subject
invention in a human patient represents a preferred embodiment.
Furthermore, the term "user" includes not only the patient using a
drug infusion device but also the caretakers (e.g., parent or
guardian, nursing staff or home care employee). The term "drug" may
include hormone, biologically active materials, pharmaceuticals or
other chemicals that cause a biological response (e.g., glycemic
response) in the body of a user or patient.
[0076] FIG. 1 illustrates a drug delivery system 100 according to
an exemplary embodiment that utilizes the principles of the
invention. Drug delivery system 100 includes a drug delivery device
102 and a remote controller 104. Drug delivery device 102 is
connected to an infusion set 106 via flexible tubing 108.
[0077] Drug delivery device 102 is configured to transmit and
receive data to and from remote controller 104 by, for example,
radio frequency communication 112. Drug delivery device 102 may
also function as a stand-alone device with its own built in
controller. In one embodiment, drug delivery device 102 is an
insulin infusion device and remote controller 104 is a hand-held
portable controller. In such an embodiment, data transmitted from
drug delivery device 102 to remote controller 104 may include
information such as, for example, insulin delivery data, blood
glucose information, basal, bolus, insulin to carbohydrates ratio
or insulin sensitivity factor, to name a few. The controller 104 is
configured to include an MPC controller 10 that has been programmed
to receive continuous glucose readings from a CGM sensor 112. Data
transmitted from remote controller 104 to insulin delivery device
102 may include glucose test results and a food database to allow
the drug delivery device 102 to calculate the amount of insulin to
be delivered by drug delivery device 102. Alternatively, the remote
controller 104 may perform basal dosing or bolus calculation and
send the results of such calculations to the drug delivery device.
In an alternative embodiment, an episodic blood glucose meter 114
may be used alone or in conjunction with the CGM sensor 112 to
provide data to either or both of the controller 104 and drug
delivery device 102. Alternatively, the remote controller 104 may
be combined with the meter 114 into either (a) an integrated
monolithic device; or (b) two separable devices that are dockable
with each other to form an integrated device. Each of the devices
102, 104, and 114 has a suitable micro-controller (not shown for
brevity) programmed to carry out various functionalities. Examples
of micro-controllers that can be used are discussed below with
reference to data processing system 1110 (FIG. 8).
[0078] Drug delivery device 102 may also be configured for
bi-directional wireless communication with a remote health
monitoring station 116 through, for example, a wireless
communication network 118. Remote controller 104 and remote
monitoring station 116 may be configured for bi-directional wired
communication through, for example, a telephone land based
communication network. Remote monitoring station 116 may be used,
for example, to download upgraded software to drug delivery device
102 and to process information from drug delivery device 102.
Examples of remote monitoring station 116 may include, but are not
limited to, a personal or networked computer 126, a server 128 to a
memory storage, a personal digital assistant, a mobile telephone, a
hospital base monitoring station or a dedicated remote clinical
monitoring station.
[0079] Drug delivery device 102 includes electronic signal
processing components including a central processing unit and
memory elements for storing control programs and operation data, a
radio frequency module 116 for sending and receiving communication
signals (i.e., messages) to/from remote controller 104, a display
for providing operational information to the user, a plurality of
navigational buttons for the user to input information, a battery
for providing power to the system, an alarm (e.g., visual, auditory
or tactile) for providing feedback to the user, a vibrator for
providing feedback to the user, a drug delivery mechanism (e.g. a
drug pump and drive mechanism) for forcing a insulin from a insulin
reservoir (e.g., a insulin cartridge) through a side port connected
to an infusion set 108/106 and into the body of the user.
[0080] Glucose levels or concentrations in physiological fluid
(e.g., blood, saliva, or interstitial fluid) of a user can be
determined by the use of the CGM sensor 112. The CGM sensor 112
utilizes amperometric electrochemical sensor technology to measure
glucose with three electrodes operably connected to the sensor
electronics and are covered by a sensing membrane and a
biointerface membrane, which are attached by a clip.
[0081] The top ends of the electrodes are in contact with an
electrolyte phase (not shown), which is a free-flowing fluid phase
disposed between the sensing membrane and the electrodes. The
sensing membrane may include an enzyme, e.g., glucose oxidase,
which covers the electrolyte phase. In this exemplary sensor, the
counter electrode is provided to balance the current generated by
the species being measured at the working electrode. In the case of
a glucose oxidase based glucose sensor, the species being measured
at the working electrode is H.sub.2O.sub.2. The current that is
produced at the working electrode (and flows through the circuitry
to the counter electrode) is proportional to the diffusional flux
of H.sub.2O.sub.2. Accordingly, a raw signal may be produced that
is representative of the concentration of glucose in the user's
body, and therefore may be utilized to estimate a meaningful
glucose value. Details of the sensor and associated components are
shown and described in U.S. Pat. No. 7,276,029, which is
incorporated by reference herein as if fully set forth herein this
application. In one embodiment, a continuous glucose sensor from
the Dexcom Seven System.RTM. (manufactured by Dexcom Inc.) can also
be utilized with the exemplary embodiments described herein.
[0082] In one embodiment of the invention, the following components
can be utilized as a system for management of diabetes that is akin
to an artificial pancreas: OneTouch Ping.RTM. Glucose Management
System by Animas Corporation that includes at least an infusion
pump and an episodic glucose sensor; and DexCom.RTM. SEVEN
PLUS.RTM. CGM by DexCom Corporation with interface to connect these
components and programmed in the MATLAB.RTM. language and accessory
hardware to connect the components together; and control algorithms
in the form of an MPC that regulates the rate of insulin delivery
based on the glucose level of the patient, historical glucose
measurement and anticipated future glucose trends, and patient
specific information.
[0083] FIG. 2 is a schematic of a control system according to
various embodiments for managing blood glucose using an insulin
pump. In particular, FIG. 2 provides for an MPC programmed into a
control logic module 10 that is utilized in controller 104 (FIG.
1). MPC logic module 10 receives a desired glucose concentration or
range of glucose concentration 12 (along with any modification from
an update filter 28 so that it is able to maintain the output
(i.e., glucose level) of the subject within the desired range of
glucose levels.
[0084] Referring to FIG. 2, the first output 14 of the MPC-enabled
control logic 10 can be a control signal to an insulin pump 16 to
deliver a desired quantity of insulin 18 into a subject 20 at
predetermined time intervals, which can be indexed, e.g., every 5
minutes using time interval index k. A second output in the form of
a predicted glucose value 15 can be utilized in control junction B.
A glucose sensor 22 (or 112 in FIG. 1) measures the glucose levels
in the subject 20 in order to provide signals 24 representative of
the actual or measured glucose levels to control junction B, which
takes the difference between measured glucose concentration 24 and
the WC predictions of that measured glucose concentration. This
difference provides input for the update filter 26 of state
variables of the model. The difference 26 is provided to an
estimator (also known as an update filter 28) that provides for
estimate of state variables of the model that cannot be measured
directly. The update filter 28 is preferably a recursive filter in
the form of a Kalman filter with tuning parameters for the model.
The output of the update or recursive filter 28 is provided to
control junction A whose output is utilized by the MPC in the
control logic 10 to further refine the control signal 14 to the
pump 16 (or 102 in FIG. 1). A tuning factor can be used with the WC
controller 10 to "tune" the controller in its delivery of the
insulin, as discussed below. In various aspects, signals from
interface 210 are used by MPC controller 10, as will be discussed.
Interface 210 can include one or more touchscreens, buttons,
network connections, keyboards, pointing devices, or other devices
for receiving data or instructions from humans (e.g., subjects or
medical professionals) or other computer systems.
[0085] The MPC logic used in controller 10 controls a subject
glucose level to a safe glucose zone, e.g., with the lower blood
glucose limit of the zone varying between 80-100 mg/dL or set to 90
mg/dL and the upper blood glucose limit varying between about
140-180 mg/dL or set to 180 mg/dL; the algorithm will henceforth be
referred to as the "zone MPC". Controlling to a target zone is, in
general, applied to controlled systems that lack a specific set
point with the controller's goal being to keep the controlled
variable, (CV), for example the glucose values, in a predefined
zone. Control to a desired, normal-blood-sugar-level ("euglycemic")
zone as opposed to a single aim level is highly suitable for the
artificial pancreas because of the absence of a natural glycemic
set point. Moreover, an inherent benefit of control to zone is the
ability to limit pump actuation/activity in a way that if glucose
levels are within the zone then no extra correction shall be
suggested.
[0086] In real-time, the insulin delivery rate I.sub.D from the
zone MPC law is calculated by an on-line mathematical optimization
(e.g., an operation to find minima or maxima of a function), which
evaluates at each sampling time the next insulin delivery rate. The
optimization at each sampling time is based on the estimated
metabolic state (plasma glucose, subcutaneous insulin) obtained
from the dynamic model stored in module 10.
[0087] The MPC of control logic 10 incorporates an explicit model
of human T1DM glucose-insulin dynamics. The model is used to
predict future glucose values and to calculate future controller
moves that will bring the glucose profile to the desired range. MPC
in controllers can be formulated for both discrete- and
continuous-time systems; the controller is set in discrete time,
with the discrete time (stage) index k referring to the epoch of
the k.sup.th sample occurring at continuous time t=kT.sub.s, where
T.sub.s=5 min is the sampling period. Software constraints ensure
that insulin delivery rates are constrained between minimum (i.e.,
zero) and maximum values. The first insulin infusion (out of N
steps) is then implemented. At the next time step, k+1 based on the
new measured glucose value and the last insulin rate, the process
is repeated.
[0088] Specifically, we start with the original linear difference
model used for zone MPC:
G'(k)=a.sub.1G'(k-1)+a.sub.2G'(k-2)+a.sub.3G'(k-3)+a.sub.4G'(k-4)+a.sub.-
5G'(k-5)+bI.sub.M(k-4)
I.sub.M(k)=c.sub.1I.sub.M(k-1)+c.sub.2I.sub.M(k-2)+d.sub.1I'.sub.D(k-1)+-
d.sub.2I'.sub.D(k-2) (1)
where: [0089] k is the discrete time interval index having a series
of indexing counters where k=1, 2, 3 . . . . [0090] G' is the
measured glucose concentration [0091] I.sub.M is the "mapped
insulin" which is not a measured quantity [0092] I'.sub.D is the
delivered insulin or a manipulated variable [0093] and coefficients
a.sub.1.about.2.993; a.sub.2.about.(-3.775); a.sub.3.about.2.568;
a.sub.4.about.(-0.886); a.sub.5.about.0.09776; b.about.(-1.5);
c.sub.1.about.1.665; c.sub.2.about.(-0.693); d.sub.1.about.0.01476;
d.sub.2.about.0.01306.
[0094] Using an FDA-accepted metabolic simulator, as known to those
skilled in the art, Eq. (1) can be reduced to the following linear
difference model in Equation (2):
( a ) G ' ( k ) = 2.993 G ' ( k - 1 ) - 3.775 G ' ( k - 2 ) + 2.568
G ' ( k - 3 ) - 0.886 G ' ( k - 4 ) + 0.09776 G ' ( k - 5 ) - 1.5 I
M ( k - 4 ) + 0.1401 Meal M ( k - 2 ) + 1.933 Meal M ( k - 3 ) ( b
) I M ( k ) = 1.665 I M ( k - 1 ) - 0.693 I M ( k - 2 ) + 0.01476 I
D ' ( k - 1 ) + 0.01306 I D ' ( k - 2 ) ( c ) Meal M ( k ) = 1.501
Meal M ( k - 1 ) + 0.5427 Meal M ( k - 2 ) + 0.02279 Meal ( k - 1 )
+ 0.01859 Meal ( k - 2 ) ( 2 ) ##EQU00001##
where: [0095] G' is the glucose concentration output (G) deviation
variable (mg/dL), i.e., G'.ident.G-110 mg/dL, [0096] I.sub.D' is
the insulin infusion rate input (I.sub.D) deviation variable (U/h),
i.e., I.sub.D'.ident.I.sub.D-basal U/h, [0097] Meal is the CHO
ingestion input (gram-CHO), [0098] I.sub.M is the mapped
subcutaneous insulin infusion rates (U/h), and [0099] Meal.sub.M is
the mapped CHO ingestion input (gram-CHO).
[0100] The dynamic model in Eq. (2) relates the effects of insulin
infusion rate (I.sub.D), and CHO ingestion input (Meal) on plasma
glucose. The model represents a single average model for the total
population of subjects. The model and its parameters are fixed.
[0101] The second-order input transfer functions described by parts
(b) and (c) in Eq. (2) are used to generate an artificial input
memory in the zone MPC schema to prevent insulin over-dosing, and
consequently prevent hypoglycemia. In order to avoid over-delivery
of insulin, the evaluation of any sequential insulin delivery must
take into consideration the past administered insulin against the
length of the insulin action. However, a one-state linear
difference model with a relatively low order uses the output
(glycemia) as the main source of past administered input (insulin)
"memory." In the face of the model mismatch, noise, or change in
the subject's insulin sensitivity, this may result in under- or
over-delivery of insulin. This is mitigated by adding two
additional states (I.sub.M and Meal.sub.M) for the mapped insulin
and meal inputs that carry a longer insulin memory.
[0102] Zone MPC is applied when the specific set point value of a
controlled variable (CV) is of low relevance compared to a zone
that is defined by upper and lower boundaries. Moreover, in the
presence of noise and model mismatch there is no practical value
using a fixed set point. Other details of the derivation for the
Zone MPC technique are shown and described in Benyamin Grosman,
Ph.D., Eyal Dassau, Ph.D., Howard C. Zisser, M.D., Lois
Jovanovi{hacek over (c)}, M.D., and Francis J. Doyle III, Ph.D.
"Zone Model Predictive Control: A Strategy to Minimize Hyper and
Hypoglycemic Events" Journal of Diabetes Science and Technology,
Vol. 4, Issue 4, July 2010, and US Patent Application Publication
No. 2011/0208156 to Doyle et al., entitled "Systems, Devices, and
Methods to Deliver Biological Factors or Drugs to a Subject," with
the publication date of Aug. 25, 2011, all which are incorporated
by reference as if set forth herein. Additional details of the Zone
MPC are shown and described in US Patent Application Publication
No. 20110208156, which is incorporated by reference as if set forth
herein. A related derivation of zone MPC was presented in
Maciejowski J M., "Predictive Control with Constraints" Harlow, UK:
Prentice-Hall, Pearson Education Limited, 2002.
[0103] Zone MPC typically divides the range of the controlled
variable into three different zones. The permitted range is the
control target and it is defined by upper and lower bounds. The
upper, hyperglycemic zone represents undesirably-high predicted
glucose levels. The lower, hypoglycemic or low alarm zone
represents undesirably-low predicted glycemic values. The lower
zone can be a hypoglycemic zone or a low alarm zone, which is a
pre-hypoglycemic protective zone. The zone MPC optimizes the
predicted glycemia by manipulating the near-future insulin control
moves to stay in the permitted zone under specified constraints.
The predicted residuals are defined as the difference between the
CV that is out of the desired zone and the nearest bound.
[0104] In various aspects, zone MPC is implemented by defining
fixed upper and lower bounds as soft constraints. A mathematical
optimization process uses weights that switch between zero and some
final values when the predicted CVs are in or out of the desired
zone, respectively.
[0105] Model predictive control operates by mathematically
minimizing a cost function. For example, future glucose levels are
predicted from past glucose levels and insulin amounts and from the
candidate insulin amounts to be delivered in the future, e.g.,
using linear difference models of insulin-glucose dynamics. A cost
is assigned to these predicted glucose levels. For zone MPC, the
cost function defines the zone of control by setting cost much
lower (e.g., 0) within the zone than out of the zone. Therefore,
the cost of future glucose levels causes the optimization to select
future I'.sub.D values that will tend to keep the predicted outputs
within the zone of control (e.g., a zone defined by upper and lower
bounds), rather than future values that will move the predicted
outputs towards a specific set point. Optimizing using such a cost
function can reduce hypo- and hyper-glycemic excursions from the
zone of control. The aggressiveness of the controller in reducing
excursions is influenced by the cost function, e.g., weights
contained therein.
[0106] The zone MPC cost function J is:
J ( I D ' ) = Q j = 1 P G zone ( k + j ) + R j = 0 M - 1 I D ' ( k
+ j ) s . t . G ( k + j ) = f [ G ( k + j - 1 ) , I D ' ( k + j - 1
) ] .A-inverted. j = 1 , P - basal ( k + j ) .ltoreq. I D ' ( k + j
) .ltoreq. 72 .A-inverted. j = 0 , M - 1 ( 3 ) ##EQU00002##
In various embodiments, I'.sub.D is expanded:
J(I.sub.D')=.SIGMA..parallel.G.sup.zone(k+j).parallel.+R.SIGMA..parallel-
.I.sub.D(k+j)-basal(k+j).parallel. (4)
where: [0107] Q is a weighting factor on the predicted glucose
term; [0108] R is a tuning factor on the future proposed inputs in
the cost function; [0109] f is the prediction function (in Eq.
(2)); [0110] vector I.sub.D contains the set of proposed
near-future insulin infusion amounts. It is the "manipulated
variable" because it is manipulated in order to find the minimum in
J; [0111] basal(t) is the basal delivery rate at time interval t;
and [0112] G.sup.zone is a variable quantifying the deviation of
future model-predicted CGM values G outside a specified glycemic
zone. In various embodiments, G.sup.zone is:
[0112] G zone = { 0 if G ZL .ltoreq. G .ltoreq. G ZH G - G ZH if G
> G ZH G ZL - G if G < G ZL ( 5 ) ##EQU00003##
where the glycemic zone is defined by the upper limit G.sub.ZH and
the lower limit G.sub.ZL.
[0113] Thus, if all the predicted glucose values are within the
zone, then every element of G.sup.zone is equal to 0, and
consequently J is minimized with I.sub.D=basal for that time of
day, i.e., the algorithm "defaults" to the patient's current basal
insulin infusion rate. On the other hand, if any of the predicted
glucose values are outside the zone, then G.sup.zone>0 and thus
contributes to the cost function. In this case, the near-future
proposed insulin infusion amounts I.sub.D will deviate from the
basal in order to prevent out-of-zone deviation in G.sup.zone from
ever happening, which will also "contribute" to the cost function.
Then, a quantitative balance is found in the optimization, based on
the weighting factor R.
[0114] In order to solve optimization problem of Equations (2)-(5),
a commercially available software (e.g., MATLAB's "fmincon.m"
function) can be used. For this function, the following parameters
are used for each optimization: [0115] Initial guess for the
insulin delivery rates, I.sub.D'(0), is the null vector {right
arrow over (0)}.epsilon.R.sup.M, e.g., if M=5 the initial guess for
each optimization is I.sub.D'=[0 0 0 0 0]. This implies that the
initial guess is equivalent to the basal rate. [0116] Maximum
number of function evaluations allowed is Max f=100*M, where M is
control horizon as described earlier. [0117] Maximum number of
iterations is Max_i=400, which is fixed. [0118] Termination on the
cost function values Term_cost=1e-6, which is fixed. [0119]
Termination tolerance Term_tol on the manipulated variables
I.sub.D' is 1e-6.
[0120] The following hard constraints are implemented on the
manipulated variables I.sub.D'(t):
-basal(t).ltoreq.I.sub.D'(t).ltoreq.72 U/h (6)
where basal is the subject's basal rate as set by the subject or
his/her physician, e.g., in the range 0.6-1.8 U/hr.
[0121] Although the values of control horizontal parameter M and
prediction horizon parameter P have significant effects on the
controller performance, and are normally used to tune an MPC based
controller, they can be heuristically tuned based on knowledge of
the system. Tuning rules are known to those skilled in the field.
According to these rules M and P may vary between:
2.ltoreq.M.ltoreq.10
20.ltoreq.P.ltoreq.120. (7)
In various embodiments, M=5 and P=108.
[0122] The ratio of the output error weighting factor Q and the
input change weighting matrix or tuning factor R may vary
between:
10 .ltoreq. R Q .ltoreq. 1000 ( 8 ) ##EQU00004##
In various embodiments, R/Q=500 or 250.
[0123] Once the controller is initialized and switched on,
real-time calculations take place every five minutes, corresponding
to the sample time for the glucose sensor. The first element of
I.sub.D is delivered as an insulin dose to the patient through the
insulin pump, five minutes elapse, a new CGM reading becomes
available, and the process repeats. In various aspects, the
controller delivers the basal rate until M samples have been taken;
this is sometimes referred to as a "burn-in" period. It is noted
that the future control moves are hard-constrained, set by the
insulin pump's ability to deliver a maximum rate of insulin and the
inability to deliver negative insulin values. Other details of
related subject matter including state estimator, and other MPC are
provided by Rachel Gillis et al., "Glucose Estimation and
Prediction through Meal Responses Using Ambulatory Subject Data for
Advisory Mode Model Predictive Control" Journal of Diabetes Science
and Technology Vol. 1, Issue 6, November 2007 and by Youqing Wang
et al., "Closed-Loop Control of Artificial Pancreatic .beta.--Cell
in Type 1 Diabetes Mellitus Using Model Predictive Iterative
Learning Control" IEEE Transactions on Biomedical Engineering, Vol.
57, No. 2, February 2010, which are hereby incorporated by
reference into this application as if fully set forth herein.
[0124] It is known that the tuning parameter (designated here as
"R") can have a significant effect on the quality of the glucose
control. The parameter--known as the aggressiveness factor, gain,
and other names--determines the speed of response of the algorithm
to changes in glucose concentration. A relatively conservative
value of R results in a controller that is slow to adjust insulin
infusion amounts (relative to basal) in response to changes in
glucose; on the other hand, a relatively aggressive value of R
results in a controller that is quick to respond to changes in
glucose. In principle, an aggressive controller would result in the
best glucose control if 1) the available glucose measurements are
accurate, and moreover 2) the model predictions of future glucose
trends are accurate. If these conditions are not true, then it may
be safer to use a conservative controller.
[0125] In various aspects, basal rate basal(t) changes over time.
For example, the basal rate can be lower at night (e.g., 0.5 U/h),
when metabolism is low, and higher during the day. The cost
function J above includes an I.sub.D-basal term, so there is a cost
to deviating from basal. The Zone MPC controller is driven to keep
I.sub.D close to basal unless doing so raises the G.sup.zone term
in J more than a deviation from basal would.
[0126] Normally, MPC-controlled insulin pumps deliver insulin
according to a base insulin delivery profile (basal(t)), suitably
adjusted to maintain glucose within the euglycemic zone as
described above. Described herein are three examples of temporary
insulin delivery profiles patients can use to tune their insulin
supply without requiring extensive hand computations, and without
concern for a hypo- or hyperglycemic excursion. These examples are
referred to as "soft," "semi-soft," and "hard." These three can be
used together or separately, and features of the various
embodiments herein can be combined. These aspects can be used to
provide temporary basals or extended boluses, or extended boluses
contemporaneously with temporary basals. In various aspects, an
insulin-pump controller operates at any given time with one of a
base, soft, semi-soft, or hard insulin delivery profile; the
profiles are not used simultaneously in these aspects.
[0127] FIG. 3 shows an example of a soft temporary insulin delivery
profile. The abscissa is time, e.g., in hours, from the beginning
of the temporary insulin delivery profile (t=0). The ordinate is
insulin delivery rate in U/h. Note that the ordinate is in the
physical units of U/h, and thus 0 on the ordinate means no insulin
(as opposed to deviation units, which would mean that 0 is actually
the basal rate). Other units can be used for either axis, and the
ranges of values shown on each axis are not limiting. This is also
the case for FIGS. 4 and 6.
[0128] Base insulin delivery profile 310 is an example of a basal
function that specifies constant insulin delivery. In this example,
the patient's base insulin delivery rate is 1.2 U/h. The temporary
insulin delivery profile 320 (dashed line) specifies the base
insulin delivery profile plus 50%, or 1.8 U/h, for 1 h, starting at
time zero. Therefore, in the time range 330 between times 0 and 1 h
on this figure, basal is 1.8 U/h. Outside time range 330, basal is
1.2 U/h. The value of basal at a time interval k is the base
insulin delivery profile value at time k outside the time range
330, or the temporary insulin delivery profile value inside the
time range 330. The temporary insulin delivery profile can be
received directly, or can be produced by modifying the base insulin
delivery profile value according to a received profile
modifier.
[0129] Continuing this example, although basal is higher in the 0 .
. . 1 h time range 330 than outside it, the zone MPC controller
module is not required to increase delivery in the time range 330.
The I.sub.D amount computed depends on values of the cost function
J In general, as long as the predicted glucose level is within the
MPC zone [G.sub.ZL, G.sub.ZH], J will be lowest when I.sub.D
follows basal, which is the temporary insulin delivery profile
inside time range 330. Therefore, the temporary insulin delivery
profile is likely to recommend higher-than-base insulin amounts for
at least part of the time range 330. However, if the predicted
glucose level exits the zone, the MPC algorithm will select
whatever I.sub.D values are necessary to bring glucose back into
the zone. This is represented graphically by the block arrows: the
controller has the full range of possible I.sub.D values available
whether inside or outside time range 330.
[0130] Patients might, for example, program soft temporary basals
or soft extended boluses if they believe they will need an atypical
amount of insulin in the near future but are not sure how much.
Soft delivery profiles provide confidence that zone controllers
will still act to protect patients from glycemic excursions.
[0131] FIG. 4 shows an example of a "semi-soft" or "hybrid"
temporary insulin delivery profile. The base insulin delivery
profile 410 in this example is 1.2 U/h. As in the example of FIG.
3, the temporary insulin delivery profile 420 (dashed line), which
corresponds to the application of a temporary basal or extended
bolus, specifies 50% over base profile 410, or 1.8 U/h, in time
range 430 (0-1 h). Outside time range 430, the controller can
specify any amount I.sub.D of insulin, down to zero, as represented
by the block arrows 415. Inside time range 430, the controller
module is constrained to recommend at least the additional
programmed insulin (temporary minus base), but can deliver more as
it sees fit. This range of possible I.sub.D values is represented
by block arrows 425. Region 440 is empty, indicating that the zone
controller cannot select an I.sub.D value in this range during this
time. Region 440 can be kept empty by constraining I.sub.D for the
present time interval to be no less than temporary minus base,
implemented by adjusting Eq. (6) appropriately.
[0132] In various aspects, if the additional programmed amount
.DELTA.(t)=(temporary-base)
is too much insulin, driving the blood glucose down, a safety
module can reduce this dose in order to reduce the probability or
severity of a hypoglycemic excursion. In other aspects, safety
modules are not required because of patient biochemistry or other
factors. Safety modules are discussed further below.
[0133] In an example, patients might program semi-soft temporary
basals or semi-soft extended boluses if they believe they will need
some additional insulin to offset anticipated carbohydrate intake,
e.g., at a cocktail party. The MPC controller will still provide
more insulin as necessary to reduce the probability of a
hyperglycemic excursion, and can reduce insulin subject to the
.DELTA.(t) limit to reduce the probability of a hypoglycemic
excursion.
[0134] In various examples, the temporary insulin delivery profile
is used to provide an extended bolus. The temporary insulin
delivery profile includes former and latter subranges of the
selected time range and specifies higher amounts or rates of
insulin delivery in the former subrange than in the latter
subrange. For example, instead of a 10 U bolus administered at t=0,
5 U can be administered immediately and 5 U over the remainder of
an hour. The first 5 U are administered starting from t=0 for as
long as the pump takes to deliver 5 U. If the pump is limited to a
maximum delivery rate of 1 U/min., the first 5 U will take 5 min.
The period from t=0 to 5 min is the former subrange. The remaining
5 U of the bolus are spread over remainder of an hour, i.e., from
t=5 min to 60 min. This time range is the latter subrange. The
delivery rate in the latter subrange is thus 0.091 U/min, much less
than the 1 U/min rate in the first subrange. Each subrange can be
continuous or include multiple separated segments of time.
[0135] FIG. 5 is a flowchart illustrating exemplary methods of
controlling an infusion pump. Various aspects shown here implement
soft or semi-soft control schemes. Solid arrows connect subsequent
steps and dashed arrows connect steps to their substeps. The
infusion pump (e.g., insulin pump 16, FIG. 2) is responsive to a
controller (e.g., controller 10, FIG. 2) that receives data from at
least one glucose sensor (e.g., glucose sensor 22). In various
embodiments, the steps of the method are automatically performed
using the controller. Processing begins with step 510.
[0136] In step 510, a base insulin delivery profile is received. As
discussed above, the base profile (e.g., profile 410, FIG. 4) is
not always basal(k) as used in the Zone MPC algorithm. Step 510 is
followed by step 520, but can be performed simultaneously or after
step 520.
[0137] In step 520, the controller receives one or more respective
glucose level measurements for each time interval of a series of
discrete time intervals. The measurements are received from the
glucose sensor(s). The measurements can be measurements of a
patient or subject, e.g., a human. The time intervals can be evenly
spaced or not, and can skip in the middle. Step 520 is followed by
step 530.
[0138] In step 530, a temporary insulin delivery profile is
received. The temporary profile extends over a selected time range
of the time intervals. The range does not have to be continuous and
can include separated subranges. Step 530 is followed by step
540.
[0139] In step 540, the controller calculates a candidate insulin
delivery amount for a selected one of the time intervals based on a
model predictive controller. The model predictive controller, e.g.,
as discussed above, predicts an excursion of the glucose level from
a selected target glucose range (e.g., G.sup.zone(k+j)) using at
least some of the glucose measurements, and optionally using
estimates of a metabolic state of the subject. The model predictive
controller then computes an estimated insulin delivery amount
(e.g., I.sub.D). In various examples, determining the estimated
insulin delivery amount includes making an initial guess of
I.sub.D:=basal, as discussed above. The model predictive controller
then adjusts the estimated insulin delivery amount, e.g., by
mathematical minimization of J, to provide the candidate insulin
delivery amount. The adjustment is performed in accordance with the
predicted excursion, the base insulin delivery profile, or, if the
selected time interval is in the selected range, the temporary
insulin delivery profile. Step 540 is followed by step 550.
[0140] In step 550, an approved insulin delivery amount is
determined from the candidate insulin delivery amount. In an
example, the approved amount is set equal to the candidate amount.
In another example, a safety module determines the approved amount.
Specifically, in this example, the candidate delivery amount is
reduced according to a hypoglycemia safety model to provide the
approved insulin delivery amount. The hypoglycemia safety model can
be the glucose model used by the model predictive controller, or
can be a different model. If the hypoglycemic safety model
indicates the candidate insulin delivery amount will not lead to
hypoglycemia, the candidate insulin delivery amount is approved
unchanged, i.e., with a reduction of zero (0). If the hypoglycemic
safety model indicates the candidate insulin delivery amount may
lead to hypoglycemia, the candidate insulin delivery amount is
reduced to an amount that does not lead to hypoglycemia according
to the hypoglycemic safety model. In various aspects, the Safety
Supervision Model from the University of Virginia can be used. Step
550 is followed by step 560.
[0141] In step 560, the controller commands the infusion pump to
deliver the approved insulin delivery amount. In this way, insulin
can be delivered to a patient to maintain the patient's blood
glucose within the desired glycemic zone.
[0142] The temporary insulin profile can be provided as new
amounts, or as changes to existing amounts in the base insulin
delivery profile. For example, in various embodiments, step 530 of
receiving a temporary insulin delivery profile includes step 533 of
receiving a profile modifier. The profile modifier can be, e.g., +1
U/h or +50%. Step 533 is followed by step 536, in which the profile
modifier is applied to the base insulin delivery profile to produce
the temporary insulin delivery profile. Application can include
adding or multiplying the profile modifier with values of the base
insulin delivery profile (e.g., 1 U/h+0.5 U/h, or 1 U/h*150%). The
temporary insulin profile can also be provided as changes to
existing amounts in the base insulin delivery profile as modified
by a prior-applied temporary insulin delivery profile. For example,
in a given time interval k, a first-applied temporary insulin
delivery profile can specify +50% insulin. Additionally, a
second-applied temporary insulin delivery profile, e.g., for an
extended bolus, can specify +0.5 U/h. The insulin delivery for time
interval k is then (base(k).times.1.5)+0.5 for base insulin
delivery profile base(k).
[0143] In various aspects, a soft profile is used. Specifically,
step 540 includes step 543. In step 543, if the selected time
interval is in the selected range (e.g., time range 330, FIG. 3),
the estimated delivery amount is adjusted in accordance with the
predicted excursion and the temporary insulin delivery profile. If
the selected time interval is not in the selected range, the
estimated delivery amount is adjusted in accordance with the
predicted excursion and the base insulin delivery profile. The
controller can have the full range of adjustment available, but
using different profiles, i.e., different basal(k) values, inside
versus outside the selected time range.
[0144] In other aspects, a semi-soft profile is used, and step 540
includes step 546. In step 546, if the selected time interval is in
the selected range (e.g., time range 430, FIG. 4), the estimated
delivery amount is adjusted in accordance with the predicted
excursion and the temporary insulin delivery profile. The
calculated insulin delivery amount at time t is constrained to be
at least a difference .DELTA.(t) between the temporary insulin
delivery profile and the base insulin delivery profile in the
selected time interval, e.g.,
estimated:=max(estimated,.DELTA.(t)).
[0145] If the selected time interval is not in the selected range,
the estimated delivery amount is adjusted in accordance with the
predicted excursion and the base insulin delivery profile.
[0146] FIG. 6 shows an example of a "hard" temporary basal or
extended bolus. The base insulin delivery profile 610 specifies a
rate of 1.2 U/h. The hard temporary insulin delivery profile 620 is
50% higher, or 1.8 U/h, for 1 h, starting at time zero (time range
630). Before and after time range 630, the controller module can
recommend delivery away from the base insulin delivery profile 610
as necessary to maintain blood glucose level within the zone. This
is represented graphically by block arrows 615. During time range
630, the controller module simply provides the amount of insulin
specified in temporary insulin delivery profile 620. As discussed
above, in some embodiments, a safety module can reduce insulin dose
if necessary. Not all configurations require a safety module.
[0147] In an example, a hard temporary basal or extended bolus can
be applied if a patient or doctor has determined that a specific
insulin amount is required. During a hard temporary insulin
delivery profile 620, the controller still measures glucose levels
G(k-1, k-2 . . . ) and records the measurements, but the controller
does not need to predict glucose levels G(k) unless such prediction
is required by a safety module or another processing function.
Since all data are available, at the end of the time range 630,
normal MPC control of I.sub.D can resume without an M-cycle
delay.
[0148] FIG. 7 is a flowchart illustrating exemplary methods of
controlling an infusion pump. Various aspects shown here implement
soft or semi-soft control schemes. Solid arrows connect subsequent
steps and dashed arrows connect steps to their substeps. The
infusion pump (e.g., insulin pump 16, FIG. 2) is responsive to a
controller (e.g., controller 10, FIG. 2) that receives data from at
least one glucose sensor (e.g., glucose sensor 22). In various
embodiments, the steps of the method are automatically performed
using the controller. Processing begins with step 510. Steps 510,
520, 530, 533, and 536 can be as shown in FIG. 5. The hard profile
is applied very differently than a soft or semi-soft profile. Step
530 is followed by step 740.
[0149] In step 740, a candidate insulin delivery amount for a
selected one of the time intervals is calculated. A model
predictive controller determines whether the selected time interval
is outside the selected range (e.g., time range 630, FIG. 6). If
so, the model predictive controller predicts an excursion of the
glucose level from a selected target glucose range using at least
some of the glucose measurements, as discussed above. The model
predictive controller computes an estimated insulin delivery amount
and adjusts the estimated insulin delivery amount to provide the
candidate insulin delivery amount. The adjustment is performed in
accordance with the predicted excursion and the base insulin
delivery profile. This is represented by sub-step 743.
[0150] If the selected time interval is in the selected range,
however, the controller or model predictive controller retrieves
the candidate insulin delivery amount for the selected time
interval from the temporary insulin delivery profile
(I.sub.D(k):=basal(k), where basal is the temporary insulin
delivery profile or the base insulin delivery profile modified by a
profile modifier, as discussed above). This is represented by
sub-step 746. Step 740 is followed by step 550.
[0151] Steps 550 and 560 can be as shown in FIG. 5: determining an
approved insulin delivery amount and commanding the infusion pump
to deliver the approved insulin delivery amount. In various
embodiments of step 550, as discussed above, a hypoglycemia safety
model is used to determine whether a hypoglycemic excursion is
predicted and, if so, the candidate delivery amount is reduced to
provide the approved insulin delivery amount.
[0152] To recap, the system of FIG. 2 is provided to manage
diabetes of a subject. In this system, the following components are
utilized: continuous glucose sensor 22, pump 16, and controller 10.
The continuous glucose monitor continuously measures glucose level
of the subject at discrete generally uniform time intervals
(indexed "k", e.g., approximately every 30 seconds or every minute,
or every five minutes) and provides the glucose level at each
interval in the form of glucose measurement data. The insulin
infusion pump is controlled by the controller 10 to deliver insulin
to the subject 20. The controller 10 is programmed with the
appropriate MPC program to control the pump and communicate with
the glucose meter and the glucose monitor. In this aspect, the
controller determines an insulin delivery rate for each time
interval in the time interval index (k) from the model predictive
control based on desired glucose concentration 12 and glucose
concentration 24 measured by the monitor 22 at each interval of the
interval index (k).
[0153] FIG. 8 shows various embodiments of apparatus for the
delivery of insulin, including data-processing components for
analyzing data and performing other analyses and functions
described herein, and related components. Subject 1138 is not part
of the apparatus but is shown for context. Glucose monitor 1121 is
adapted to continually measure respective glucose levels of subject
1138 at discrete time intervals and provide respective glucose
measurement data indicating each measured glucose level. Glucose
monitor 1121 can include one or more glucose sensor(s) 1122, e.g.,
including glucose oxidase or glucose dehydrogenase, to transduce
glucose concentration to a signal that can be measured
electrochemically. Examples of glucose sensors are discussed above.
Insulin infusion pump 1125 is configured to deliver insulin, e.g.,
to subject 1138, in response to a delivery control signal. The
apparatus includes a controller, e.g., data processing system 1110,
that receives glucose measurement data from the glucose monitor
1121 and commands the pump 1125 to deliver insulin.
[0154] A peripheral system 1120, a user interface system 1130, and
a data storage system 1140 are communicatively connected to the
data processing system 1110. Data processing system 1110 can be
communicatively connected to network 1150, e.g., the Internet or an
X.25 network, as discussed below.
[0155] The data processing system 1110 includes one or more data
processor(s) that implement processes of various aspects described
herein. A "data processor" is a device for processing data and can
include a central processing unit (CPU), a desktop computer, a
laptop computer, a mainframe computer, a personal digital
assistant, a digital camera, a cellular phone, a smartphone, or any
other device for processing data, managing data, or handling data,
whether implemented with electrical, magnetic, optical, biological
components, or otherwise.
[0156] The phrase "communicatively connected" includes any type of
connection, wired or wireless, between devices, data processors, or
programs in which data can be communicated. Subsystems such as
peripheral system 1120, user interface system 1130, and data
storage system 1140 are shown separately from the data processing
system 1110 but can be stored completely or partially within the
data processing system 1110.
[0157] The data storage system 1140 includes or is communicatively
connected with one or more tangible non-transitory
computer-readable storage medium(s) configured to store
information, including the information needed to execute processes
according to various aspects. A "tangible non-transitory
computer-readable storage medium" as used herein refers to any
non-transitory device or article of manufacture that participates
in storing instructions which may be provided to the data
processing system 1110 for execution. Such a non-transitory medium
can be non-volatile or volatile. Examples of non-volatile media
include floppy disks, flexible disks, or other portable computer
diskettes, hard disks, magnetic tape or other magnetic media,
Compact Discs and compact-disc read-only memory (CD-ROM), DVDs,
BLU-RAY disks, HD-DVD disks, other optical storage media, Flash
memories, read-only memories (ROM), and erasable programmable
read-only memories (EPROM or EEPROM). Examples of volatile media
include dynamic memory, such as registers and random access
memories (RAM). Storage media can store data electronically,
magnetically, optically, chemically, mechanically, or otherwise,
and can include electronic, magnetic, optical, electromagnetic,
infrared, or semiconductor components.
[0158] Aspects of the present invention can take the form of a
computer program product embodied in one or more tangible
non-transitory computer readable medium(s) having computer readable
program code embodied thereon. Such medium(s) can be manufactured
as is conventional for such articles, e.g., by pressing a CD-ROM.
The program embodied in the medium(s) includes computer program
instructions that can direct data processing system 1110 to perform
a particular series of operational steps when loaded, thereby
implementing functions or acts specified herein.
[0159] In an example, data storage system 1140 includes memory
1141, e.g., a random-access memory, and disk 1142, e.g., a tangible
computer-readable storage device such as a hard drive or a
solid-state flash drive. Computer program instructions are read
into memory 1141 from disk 1142, or a wireless, wired, optical
fiber, or other connection. Data processing system 1110 then
executes one or more sequences of the computer program instructions
loaded into memory 1141, as a result performing process steps
described herein. In this way, data processing system 1110 carries
out a computer implemented process that provides for a technical
effect of controlling insulin output based on inputs to a model of
a biological system. For example, blocks of the flowchart
illustrations or block diagrams herein, and combinations of those,
can be implemented by computer program instructions. Memory 1141
can also store data used by running programs. In this example,
memory 1141 (or other components in data storage system 1140)
stores a base insulin delivery profile.
[0160] Computer program code can be written in any combination of
one or more programming languages, e.g., Java, Smalltalk, C++, C,
or an appropriate assembly language. Program code to carry out
methods described herein can execute entirely on a single data
processing system 1110 or on multiple communicatively-connected
data processing systems 1110. For example, code can execute wholly
or partly on a user's computer and wholly or partly on a remote
computer, e.g., a server. The remote computer can be connected to
the user's computer through network 1150. The user's computer or
the remote computer can be non-portable computers, such as
conventional desktop personal computers (PCs), or can be portable
computers such as tablets, cellular telephones, smartphones, or
laptops.
[0161] The peripheral system 1120 can include one or more devices
configured to provide digital content records or other data to the
data processing system 1110. In this example, glucose monitor 1121
and glucose pump 1125 are connected to data processing system 1110
via peripheral system 1120. The monitor 1121 and the pump 1125 can
also be directly connected to data processing system 1110. The
peripheral system 1120 can also include digital still cameras,
digital video cameras, cellular phones, biosensors such as activity
sensors, heart rate monitors, pulse oximeters, or other data
processors. The peripheral system 1120 can also include one or more
bus bridge(s), e.g., to operatively connect devices having USB,
FIREWIRE, RS-232, or other interfaces to data processing system
1110. The data processing system 1110, upon receipt of data from a
device in the peripheral system 1120, can store that data in the
data storage system 1140.
[0162] Data processing system 1110 is communicatively connected to
interface 1131, which can include user interface system 1130 or
network 1150. For example, the interface 1131 can include one or
more touchscreen(s), button(s), switch(es), or network
connection(s). Interface 1131 selectively receives a temporary
insulin delivery profile extending over a selected time range of
the time intervals and provides a first signal to data processing
system 1110 indicating whether the temporary insulin delivery
profile was received. This signal can be a flag set in memory in
data storage system 1140 or a specific logic level or voltage on a
wire or other electrical connection between interface 1131 and data
processing system 1110. The signal can indicate whether or not the
temporary insulin delivery profile was received using respective,
different values of the signal (e.g., logic low or logic high) or
by the presence or absence of the signal (e.g., a pulse is
transmitted when the profile is received, so if no pulse has been
transmitted, the profile has not been received). In at least one
embodiment, the interface 1131 can be operated by the subject 1138,
as represented graphically by the dashed line.
[0163] The user interface system 1130 can include a mouse, a
keyboard, another computer (connected, e.g., via a network or a
null-modem cable), a microphone and speech processor or other
device(s) for receiving voice commands, a camera and image
processor or other device(s) for receiving visual commands, e.g.,
gestures, or any device or combination of devices from which data
is input to the data processing system 1110. In this regard,
although the peripheral system 1120 is shown separately from the
user interface system 1130, the peripheral system 1120 can be
included as part of the user interface system 1130.
[0164] The user interface system 1130 also can include a display
device, a processor-accessible memory, or any device or combination
of devices to which data is output by the data processing system
1110. In this regard, if the user interface system 1130 includes a
processor-accessible memory, such memory can be part of the data
storage system 1140 even though the user interface system 1130 and
the data storage system 1140 are shown separately in FIG. 8.
[0165] In various aspects, interface 1131 includes communication
interface 1115 that is coupled via network link 1116 to network
1150. For example, communication interface 1115 can be an
integrated services digital network (ISDN) card or a modem to
provide a data communication connection to a corresponding type of
telephone line. As another example, communication interface 1115
can be a network card to provide a data communication connection to
a compatible local-area network (LAN), e.g., an Ethernet LAN, or
wide-area network (WAN). Wireless links, e.g., WiFi or GSM, can
also be used. Communication interface 1115 sends and receives
electrical, electromagnetic or optical signals that carry digital
data streams representing various types of information across
network link 1116 to network 1150. Network link 1116 can be
connected to network 1150 via a switch, gateway, hub, router, or
other networking device.
[0166] Network link 1116 can provide data communication through one
or more networks to other data devices. For example, network link
1116 can provide a connection through a local network to a host
computer or to data equipment operated by an Internet Service
Provider (ISP).
[0167] Data processing system 1110 can send messages and receive
data, including program code, through network 1150, network link
1116 and communication interface 1115. For example, a server can
store requested code for an application program (e.g., a JAVA
applet) on a tangible non-volatile computer-readable storage medium
to which it is connected. The server can retrieve the code from the
medium and transmit it through the Internet, thence a local ISP,
thence a local network, thence communication interface 1115. The
received code can be executed by data processing system 1110 as it
is received, or stored in data storage system 1140 for later
execution.
[0168] The controller, e.g., data processing system 1110, is
adapted to perform specific processing for each of a plurality of
the discrete time intervals. Memory 1141 can store program
instructions that cause data processing system 1110 to perform
these processes. The data processing system 1110 receives the
glucose measurement data for that time interval from the glucose
monitor 1121 via the peripheral system 1120. The data processing
system 1110 then determines an insulin delivery amount for that
time interval using model predictive control based on a selected
target glucose concentration range, the received glucose
measurement data, the stored base insulin delivery profile, or, in
response to the first signal and if that time interval is in the
selected time range, the received temporary insulin delivery
profile. This was discussed above, e.g., with reference to FIGS.
3-5 (soft and semi-soft profiles). The data processing system 1110
then provides to the insulin infusion pump 1125 a delivery control
signal corresponding to the determined insulin delivery amount. The
insulin infusion pump 1125 then delivers a corresponding amount of
insulin, e.g., to subject 1138.
[0169] According to at least one aspect, the interface 1131 is
adapted to receive the temporary insulin delivery profile by
receiving change information, e.g., +1 U/h, and modifying the
stored base insulin delivery profile (in data storage system 1140)
in the selected time range according to the change information to
provide the temporary insulin delivery profile. The interface 1131
can perform this modification by notifying data processing system
1110 about the modification to be performed, in response to which
data processing system 1110 executes instructions that perform the
modification.
[0170] In various embodiments, the interface 1131 is further
adapted to provide an activation signal, e.g., when the subject
1138 pushes a button on the interface 1131. The data processing
system 1110, in response to the activation signal, retrieves the
stored base insulin delivery profile and retrieves or determines
the insulin delivery amount.
[0171] In an example of using a soft profile, data processing
system 1110 is programmed to determine the insulin delivery amount
for a selected time interval using the selected target glucose
concentration range, the received glucose measurement data, the
stored base insulin delivery profile if the temporary insulin
delivery profile was not received (as indicated by the signal from
interface 1131 or lack thereof) or the selected time interval is
outside the selected time range. Otherwise, the data processing
system uses the selected target glucose concentration range, the
received glucose measurement data, and the received temporary
insulin delivery profile.
[0172] In an example of using a semi-soft profile, in response to
the first signal and if a selected time interval is in the selected
time range, the data processing system 1110 constrains the
determined insulin delivery amount for the selected time interval
to be at least a difference between respective values of the
temporary insulin delivery profile and the stored base insulin
delivery profile for the selected time interval.
[0173] In an example of using a hard profile, the data processing
system 1110 is programmed to, for each of a plurality of the
discrete time intervals, receive the glucose measurement data for
that time interval from the glucose monitor. If that time interval
is in the selected time range, the data processing system 110
retrieves a corresponding insulin delivery amount from the
temporary insulin delivery profile. This is the "hard" action, as
discussed above with reference to FIGS. 6 and 7. If the time
interval is not in the selected time range, the data processing
system 1110 determines an insulin delivery amount for that time
interval using model predictive control based on a selected target
glucose concentration range, the received glucose measurement data,
and the base insulin delivery profile. The data processing system
1110 then provides to the insulin infusion pump 1125 a delivery
control signal corresponding to the insulin delivery amount, and
the pump 1125 delivers a corresponding amount of insulin. The model
predictive controller can be but does not have to be operated to
make predictions during the selected time range. Glucose
measurements are preferably still taken and recorded in data
storage system 1140 during the selected time range so that the
model predictive controller will not have a burn-in period
(discussed above) at the end of the selected time range.
[0174] In some embodiments, the data processing system 1110, or a
safety subsystem thereof or safety component attached thereto, is
programmed to predict an excursion of a glucose level of the
subject 1138 from the selected target glucose range. This is done
using a safety model, e.g., a hypoglycemia safety model, and at
least some of the glucose measurement data for a plurality of the
time intervals. The system or component then reduces the determined
insulin delivery amount according to the predicted excursion.
[0175] In an example of using an extended bolus, the temporary
insulin delivery profile (which can be stored in data storage
system 1140) includes former and latter subranges of the selected
time range. The temporary insulin delivery profile specifies higher
amounts or rates of insulin delivery in the former subrange than in
the latter subrange, as discussed above.
[0176] In view of the foregoing, embodiments of the invention
provide improved control of temporary basals and extended boluses
in glucose pumping systems. A technical effect of soft and
semi-soft profiles is to provide increased control of pump
operation while still maintaining the ability to correct for some
deviations of blood glucose outside a desired glucose zone. A
technical effect of hard profiles is to provide determined amounts
of insulin for limited times without disturbing insulin delivery
outside those times.
[0177] While the invention has been described in terms of
particular variations and illustrative figures, those of ordinary
skill in the art will recognize that the invention is not limited
to the variations or figures described. For example, the
closed-loop controller need not be an MPC controller but can be,
with appropriate modifications by those skilled in the art, a PID
controller, a PID controller with internal model control (IMC), a
model-algorithmic-control (MAC) that are discussed by Percival et
al., in "Closed-Loop Control and Advisory Mode Evaluation of an
Artificial Pancreatic .beta. Cell: Use of
Proportional-Integral-Derivative Equivalent Model-Based
Controllers" Journal of Diabetes Science and Technology, Vol. 2,
Issue 4, July 2008. In addition, where methods and steps described
above indicate certain events occurring in certain order, those of
ordinary skill in the art will recognize that the ordering of
certain steps may be modified and that such modifications are in
accordance with the variations of the invention. Additionally,
certain of the steps may be performed concurrently in a parallel
process when possible, as well as performed sequentially as
described above. Therefore, to the extent there are variations of
the invention, which are within the spirit of the disclosure or
equivalent to the inventions found in the claims, it is the intent
that this patent will cover those variations as well.
* * * * *