Patent Publication Number: US-11660394-B2

Title: Fluid infusion system that automatically determines and delivers a correction bolus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 16/275,290, which was filed on Feb. 13, 2019 and claims the benefit of U.S. provisional patent application Ser. No. 62/739,009, filed Sep. 28, 2018, the entire content of each of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments of the subject matter described herein relate generally to drug delivery systems and, more specifically, to systems for controlling the operation of an insulin infusion device that delivers insulin to the body of a patient. 
     BACKGROUND 
     Infusion pump devices and systems are relatively well known in the medical arts, for use in delivering or dispensing an agent, such as insulin or another prescribed medication, to a patient. A typical infusion pump includes a pump drive system which typically includes a small motor and drive train components that convert rotational motor motion to a translational displacement of a plunger (or stopper) in a fluid reservoir that delivers medication from the reservoir to the body of a patient via a fluid path created between the reservoir and the body of a patient. Use of infusion pump therapy has been increasing, especially for delivering insulin for diabetics. 
     Control schemes have been developed to allow insulin infusion pumps to monitor and regulate a patient&#39;s blood glucose level in a substantially continuous and autonomous manner. Managing a diabetic&#39;s blood glucose level is complicated by variations in a patient&#39;s daily activities (e.g., exercise, carbohydrate consumption, and the like) in addition to variations in the patient&#39;s individual insulin response and potentially other factors. Some control schemes may attempt to proactively account for daily activities to minimize glucose excursions. At the same time, patients may manually initiate delivery of insulin prior to or contemporaneously with consuming a meal (e.g., a meal bolus or correction bolus) to prevent spikes or swings in the patient&#39;s blood glucose level that could otherwise result from the impending consumption of carbohydrates and the response time of the control scheme. That said, a manually-initiated bolus could introduce a risk of a postprandial glucose excursion if preceding insulin deliveries are not accounted for. 
     An insulin infusion pump can be operated in an automatic mode wherein basal insulin is delivered at a rate that is automatically adjusted for the user. While controlling the delivery of basal insulin in this manner, the pump can also control the delivery of correction boluses to account for rising glucose trends, a sudden spike in detected blood glucose, etc. Ideally, the amount of a correction bolus should be accurately calculated and administered to maintain the user&#39;s blood glucose within the desired range. In particular, an automatically generated and delivered correction bolus should safely manage the user&#39;s blood glucose level and keep it above a defined threshold level. Accordingly, there is a need to improve the handling of correction boluses that are delivered during an automatic mode of an insulin infusion pump. 
     BRIEF SUMMARY 
     A method of controlling operation of an insulin infusion device is disclosed here. The insulin infusion device includes a fluid reservoir for insulin to be delivered from the insulin infusion device to a body of a user, and has at least one processor device to perform the method. The method involves the steps of: controlling the insulin infusion device to operate in an automatic basal insulin delivery mode; obtaining a blood glucose measurement that indicates a current blood glucose level of the user; and initiating a correction bolus procedure when: (1) the blood glucose measurement exceeds a correction bolus threshold value; and (2) a maximum allowable basal insulin infusion rate (Umax) has been reached during operation in the automatic basal insulin delivery mode. The correction bolus procedure involves the steps of: calculating an initial correction bolus amount for the user; scaling the initial correction bolus amount to obtain a final correction bolus amount for the user, such that a predicted future blood glucose level of the user resulting from simulated delivery of the final correction bolus amount exceeds a low blood glucose threshold level; and delivering the final correction bolus amount to the body of the user during operation in the automatic basal insulin delivery mode. 
     An insulin infusion device is also disclosed here. The insulin infusion device includes: a fluid reservoir for insulin to be delivered from the insulin infusion device to a user; at least one processor device; and at least one memory element associated with the at least one processor device. The at least one memory element stores processor-executable instructions configurable to be executed by the at least one processor device to perform the method summarized in the preceding paragraph. 
     Also disclosed here is a tangible and non-transitory electronic storage medium having processor-executable instructions configurable to be executed by at least one processor device to perform the method summarized above. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the subject matter may be derived by referring to the detailed description and claims when considered in conjunction with the following figures, wherein like reference numbers refer to similar elements throughout the figures. 
         FIG.  1    depicts an exemplary embodiment of an infusion system; 
         FIG.  2    depicts a plan view of an exemplary embodiment of a fluid infusion device suitable for use in the infusion system of  FIG.  1   ; 
         FIG.  3    is an exploded perspective view of the fluid infusion device of  FIG.  2   ; 
         FIG.  4    is a cross-sectional view of the fluid infusion device of  FIGS.  2 - 3    as viewed along line  4 - 4  in  FIG.  3    when assembled with a reservoir inserted in the infusion device; 
         FIG.  5    is a block diagram of an exemplary infusion system suitable for use with a fluid infusion device in one or more embodiments; 
         FIG.  6    is a block diagram of an exemplary pump control system suitable for use in the infusion device in the infusion system of  FIG.  5    in one or more embodiments; 
         FIG.  7    is a block diagram of a closed-loop control system that may be implemented or otherwise supported by the pump control system in the fluid infusion device of  FIGS.  5 - 6    in one or more exemplary embodiments; 
         FIG.  8    is a block diagram of an exemplary patient monitoring system; 
         FIG.  9    is a diagram that illustrates a scenario where an automatic correction bolus can be delivered; 
         FIG.  10    is a flow diagram that illustrates an exemplary embodiment of a process for controlling the operation of an insulin infusion device; and 
         FIG.  11    is a flow diagram that illustrates an exemplary embodiment of a process for calculating an automatic correction bolus. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely illustrative in nature and is not intended to limit the embodiments of the subject matter or the application and uses of such embodiments. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Any implementation described herein as exemplary is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     Exemplary embodiments of the subject matter described herein are implemented in conjunction with medical devices, such as portable electronic medical devices. Although many different applications are possible, the following description focuses on embodiments that incorporate a fluid infusion device (or infusion pump) as part of an infusion system deployment. That said, the subject matter may be implemented in an equivalent manner in the context of other medical devices, such as continuous glucose monitoring (CGM) devices, injection pens (e.g., smart injection pens), and the like. For the sake of brevity, conventional techniques related to infusion system operation, insulin pump and/or infusion set operation, and other functional aspects of the systems (and the individual operating components of the systems) may not be described in detail here. Examples of infusion pumps may be of the type described in, but not limited to, U.S. Pat. Nos. 4,562,751; 4,685,903; 5,080,653; 5,505,709; 5,097,122; 6,485,465; 6,554,798; 6,558,320; 6,558,351; 6,641,533; 6,659,980; 6,752,787; 6,817,990; 6,932,584; and 7,621,893; each of which are herein incorporated by reference. That said, the subject matter described herein can be utilized more generally in the context of overall diabetes management or other physiological conditions independent of or without the use of an infusion device or other medical device (e.g., when oral medication is utilized), and the subject matter described herein is not limited to any particular type of medication. 
     Generally, a fluid infusion device includes a motor or other actuation arrangement that is operable to linearly displace a plunger (or stopper) of a fluid reservoir provided within the fluid infusion device to deliver a dosage of fluid, such as insulin, to the body of a user. Dosage commands that govern operation of the motor may be generated in an automated manner in accordance with the delivery control scheme associated with a particular operating mode, and the dosage commands may be generated in a manner that is influenced by a current (or most recent) measurement of a physiological condition in the body of the user. For example, in a closed-loop or automatic operating mode, dosage commands may be generated based on a difference between a current (or most recent) measurement of the interstitial fluid glucose level in the body of the user and a target (or reference) glucose value. In this regard, the rate of infusion may vary as the difference between a current measurement value and the target measurement value fluctuates. For purposes of explanation, the subject matter is described herein in the context of the infused fluid being insulin for regulating a glucose level of a user (or patient); however, it should be appreciated that many other fluids may be administered through infusion, and the subject matter described herein is not necessarily limited to use with insulin. 
     Exemplary embodiments of the subject matter described herein generally relate to proactively adjusting correction bolus amounts that are administered during automated operation of an insulin infusion device. As described in greater detail below, in exemplary embodiments, one or more mathematical models for the patient&#39;s physiological response are utilized to predict or forecast future glucose levels for a patient based on the patient&#39;s current and/or recent glucose measurements, preceding insulin deliveries, manually-input carbohydrate amounts, meal boluses, and a calculated correction bolus amount. When the patient&#39;s predicted future glucose level using the initial correction bolus amount is below a threshold value within a specified time window, the initial correction bolus amount is reduced to an amount that results in the patient&#39;s predicted future glucose level being maintained above that threshold value. In exemplary embodiments, the initial correction bolus value is progressively or iteratively scaled down to reduce the bolus amount as needed. In certain exemplary embodiments, the scaling methodology attempts to maximize the correction bolus dosage within the search space defined by the initial correction bolus amount while maintaining a predicted future glucose level for the patient that satisfies the designated hypoglycemic threshold during the time period of interest. 
     By virtue of the physiological model for the patient&#39;s predicted future glucose level accounting for the preceding automated or autonomous insulin deliveries along with the patient&#39;s current glucose level and the current trend in the patient&#39;s glucose level, the adjusted correction bolus amount reduces the risk of a post-bolus hypoglycemic event. For example, in some embodiments, closed-loop control information may be automatically adjusted in advance of an anticipated event likely to influence the patient&#39;s glucose levels or insulin response. In this regard, prospective closed-loop control adjustments account for the relatively slow action of long-acting subcutaneously administered insulin by adjusting insulin delivery in advance of an event to increase or decrease the amount of yet to be metabolized insulin on board prior to start of the event. Thus, the adjusted bolus amount accounts for prospective closed-loop insulin deliveries in a manner that reduces the risk of a post-bolus glucose excursion. 
     Turning now to  FIG.  1   , one exemplary embodiment of an infusion system  100  includes, without limitation, a fluid infusion device (or infusion pump)  102 , a sensing arrangement  104 , a command control device (CCD)  106 , and a computer  108 . The components of an infusion system  100  may be realized using different platforms, designs, and configurations, and the embodiment shown in  FIG.  1    is not exhaustive or limiting. In practice, the infusion device  102  and the sensing arrangement  104  are secured at desired locations on the body of a user (or patient), as illustrated in  FIG.  1   . In this regard, the locations at which the infusion device  102  and the sensing arrangement  104  are secured to the body of the user in  FIG.  1    are provided only as a representative, non-limiting, example. The elements of the infusion system  100  may be similar to those described in U.S. Pat. No. 8,674,288, the subject matter of which is hereby incorporated by reference in its entirety. 
     In the illustrated embodiment of  FIG.  1   , the infusion device  102  is designed as a portable medical device suitable for infusing a fluid, a liquid, a gel, or other medicament into the body of a user. In exemplary embodiments, the infused fluid is insulin, although many other fluids may be administered through infusion such as, but not limited to, HIV drugs, drugs to treat pulmonary hypertension, iron chelation drugs, pain medications, anti-cancer treatments, medications, vitamins, hormones, or the like. In some embodiments, the fluid may include a nutritional supplement, a dye, a tracing medium, a saline medium, a hydration medium, or the like. 
     The sensing arrangement  104  generally represents the components of the infusion system  100  configured to sense, detect, measure or otherwise quantify a condition of the user, and may include a sensor, a monitor, or the like, for providing data indicative of the condition that is sensed, detected, measured or otherwise monitored by the sensing arrangement. In this regard, the sensing arrangement  104  may include electronics and enzymes reactive to a biological condition, such as a blood glucose level, or the like, of the user, and provide data indicative of the blood glucose level to the infusion device  102 , the CCD  106  and/or the computer  108 . For example, the infusion device  102 , the CCD  106  and/or the computer  108  may include a display for presenting information or data to the user based on the sensor data received from the sensing arrangement  104 , such as, for example, a current glucose level of the user, a graph or chart of the user&#39;s glucose level versus time, device status indicators, alert messages, or the like. In other embodiments, the infusion device  102 , the CCD  106  and/or the computer  108  may include electronics and software that are configured to analyze sensor data and operate the infusion device  102  to deliver fluid to the body of the user based on the sensor data and/or preprogrammed delivery routines. Thus, in exemplary embodiments, one or more of the infusion device  102 , the sensing arrangement  104 , the CCD  106 , and/or the computer  108  includes a transmitter, a receiver, and/or other transceiver electronics that allow for communication with other components of the infusion system  100 , so that the sensing arrangement  104  may transmit sensor data or monitor data to one or more of the infusion device  102 , the CCD  106  and/or the computer  108 . 
     Still referring to  FIG.  1   , in various embodiments, the sensing arrangement  104  may be secured to the body of the user or embedded in the body of the user at a location that is remote from the location at which the infusion device  102  is secured to the body of the user. In various other embodiments, the sensing arrangement  104  may be incorporated within the infusion device  102 . In other embodiments, the sensing arrangement  104  may be separate and apart from the infusion device  102 , and may be, for example, part of the CCD  106 . In such embodiments, the sensing arrangement  104  may be configured to receive a biological sample, analyte, or the like, to measure a condition of the user. 
     In some embodiments, the CCD  106  and/or the computer  108  may include electronics and other components configured to perform processing, delivery routine storage, and to control the infusion device  102  in a manner that is influenced by sensor data measured by and/or received from the sensing arrangement  104 . By including control functions in the CCD  106  and/or the computer  108 , the infusion device  102  may be made with more simplified electronics. However, in other embodiments, the infusion device  102  may include all control functions, and may operate without the CCD  106  and/or the computer  108 . In various embodiments, the CCD  106  may be a portable electronic device. In addition, in various embodiments, the infusion device  102  and/or the sensing arrangement  104  may be configured to transmit data to the CCD  106  and/or the computer  108  for display or processing of the data by the CCD  106  and/or the computer  108 . 
     In some embodiments, the CCD  106  and/or the computer  108  may provide information to the user that facilitates the user&#39;s subsequent use of the infusion device  102 . For example, the CCD  106  may provide information to the user to allow the user to determine the rate or dose of medication to be administered into the user&#39;s body. In other embodiments, the CCD  106  may provide information to the infusion device  102  to autonomously control the rate or dose of medication administered into the body of the user. In some embodiments, the sensing arrangement  104  may be integrated into the CCD  106 . Such embodiments may allow the user to monitor a condition by providing, for example, a sample of his or her blood to the sensing arrangement  104  to assess his or her condition. In some embodiments, the sensing arrangement  104  and the CCD  106  may be used for determining glucose levels in the blood and/or body fluids of the user without the use of, or necessity of, a wire or cable connection between the infusion device  102  and the sensing arrangement  104  and/or the CCD  106 . 
     In some embodiments, the sensing arrangement  104  and/or the infusion device  102  are cooperatively configured to utilize a closed-loop system for delivering fluid to the user. Examples of sensing devices and/or infusion pumps utilizing closed-loop systems may be found at, but are not limited to, the following U.S. Pat. Nos. 6,088,608, 6,119,028, 6,589,229, 6,740,072, 6,827,702, 7,323,142, and 7,402,153 or United States Patent Application Publication No. 2014/0066889, all of which are incorporated herein by reference in their entirety. In such embodiments, the sensing arrangement  104  is configured to sense or measure a condition of the user, such as, blood glucose level or the like. The infusion device  102  is configured to deliver fluid in response to the condition sensed by the sensing arrangement  104 . In turn, the sensing arrangement  104  continues to sense or otherwise quantify a current condition of the user, thereby allowing the infusion device  102  to deliver fluid continuously in response to the condition currently (or most recently) sensed by the sensing arrangement  104  indefinitely. In some embodiments, the sensing arrangement  104  and/or the infusion device  102  may be configured to utilize the closed-loop system only for a portion of the day, for example only when the user is asleep or awake. 
       FIGS.  2 - 4    depict one exemplary embodiment of a fluid infusion device  200  (or alternatively, infusion pump) suitable for use in an infusion system, such as, for example, as infusion device  102  in the infusion system  100  of  FIG.  1   . The fluid infusion device  200  is a portable medical device designed to be carried or worn by a patient (or user), and the fluid infusion device  200  may leverage any number of conventional features, components, elements, and characteristics of existing fluid infusion devices, such as, for example, some of the features, components, elements, and/or characteristics described in U.S. Pat. Nos. 6,485,465 and 7,621,893. It should be appreciated that  FIGS.  2 - 4    depict some aspects of the infusion device  200  in a simplified manner; in practice, the infusion device  200  could include additional elements, features, or components that are not shown or described in detail herein. 
     As best illustrated in  FIGS.  2 - 3   , the illustrated embodiment of the fluid infusion device  200  includes a housing  202  adapted to receive a fluid-containing reservoir  205 . An opening  220  in the housing  202  accommodates a fitting  223  (or cap) for the reservoir  205 , with the fitting  223  being configured to mate or otherwise interface with tubing  221  of an infusion set  225  that provides a fluid path to/from the body of the user. In this manner, fluid communication from the interior of the reservoir  205  to the user is established via the tubing  221 . The illustrated fluid infusion device  200  includes a human-machine interface (HMI)  230  (or user interface) that includes elements  232 ,  234  that can be manipulated by the user to administer a bolus of fluid (e.g., insulin), to change therapy settings, to change user preferences, to select display features, and the like. The infusion device also includes a display element  226 , such as a liquid crystal display (LCD) or another suitable display element, that can be used to present various types of information or data to the user, such as, without limitation: the current glucose level of the patient; the time; a graph or chart of the patient&#39;s glucose level versus time; device status indicators; etc. 
     The housing  202  is formed from a substantially rigid material having a hollow interior  214  adapted to allow an electronics assembly  204 , a sliding member (or slide)  206 , a drive system  208 , a sensor assembly  210 , and a drive system capping member  212  to be disposed therein in addition to the reservoir  205 , with the contents of the housing  202  being enclosed by a housing capping member  216 . The opening  220 , the slide  206 , and the drive system  208  are coaxially aligned in an axial direction (indicated by arrow  218 ), whereby the drive system  208  facilitates linear displacement of the slide  206  in the axial direction  218  to dispense fluid from the reservoir  205  (after the reservoir  205  has been inserted into opening  220 ), with the sensor assembly  210  being configured to measure axial forces (e.g., forces aligned with the axial direction  218 ) exerted on the sensor assembly  210  responsive to operating the drive system  208  to displace the slide  206 . In various embodiments, the sensor assembly  210  may be utilized to detect one or more of the following: an occlusion in a fluid path that slows, prevents, or otherwise degrades fluid delivery from the reservoir  205  to a user&#39;s body; when the reservoir  205  is empty; when the slide  206  is properly seated with the reservoir  205 ; when a fluid dose has been delivered; when the infusion device  200  is subjected to shock or vibration; when the infusion device  200  requires maintenance. 
     Depending on the embodiment, the fluid-containing reservoir  205  may be realized as a syringe, a vial, a cartridge, a bag, or the like. In certain embodiments, the infused fluid is insulin, although many other fluids may be administered through infusion such as, but not limited to, HIV drugs, drugs to treat pulmonary hypertension, iron chelation drugs, pain medications, anti-cancer treatments, medications, vitamins, hormones, or the like. As best illustrated in  FIGS.  3 - 4   , the reservoir  205  typically includes a reservoir barrel  219  that contains the fluid and is concentrically and/or coaxially aligned with the slide  206  (e.g., in the axial direction  218 ) when the reservoir  205  is inserted into the infusion device  200 . The end of the reservoir  205  proximate the opening  220  may include or otherwise mate with the fitting  223 , which secures the reservoir  205  in the housing  202  and prevents displacement of the reservoir  205  in the axial direction  218  with respect to the housing  202  after the reservoir  205  is inserted into the housing  202 . As described above, the fitting  223  extends from (or through) the opening  220  of the housing  202  and mates with tubing  221  to establish fluid communication from the interior of the reservoir  205  (e.g., reservoir barrel  219 ) to the user via the tubing  221  and infusion set  225 . The opposing end of the reservoir  205  proximate the slide  206  includes a plunger  217  (or stopper) positioned to push fluid from inside the barrel  219  of the reservoir  205  along a fluid path through tubing  221  to a user. The slide  206  is configured to mechanically couple or otherwise engage with the plunger  217 , thereby becoming seated with the plunger  217  and/or reservoir  205 . Fluid is forced from the reservoir  205  via tubing  221  as the drive system  208  is operated to displace the slide  206  in the axial direction  218  toward the opening  220  in the housing  202 . 
     In the illustrated embodiment of  FIGS.  3 - 4   , the drive system  208  includes a motor assembly  207  and a drive screw  209 . The motor assembly  207  includes a motor that is coupled to drive train components of the drive system  208  that are configured to convert rotational motor motion to a translational displacement of the slide  206  in the axial direction  218 , and thereby engaging and displacing the plunger  217  of the reservoir  205  in the axial direction  218 . In some embodiments, the motor assembly  207  may also be powered to translate the slide  206  in the opposing direction (e.g., the direction opposite direction  218 ) to retract and/or detach from the reservoir  205  to allow the reservoir  205  to be replaced. In exemplary embodiments, the motor assembly  207  includes a brushless DC (BLDC) motor having one or more permanent magnets mounted, affixed, or otherwise disposed on its rotor. However, the subject matter described herein is not necessarily limited to use with BLDC motors, and in alternative embodiments, the motor may be realized as a solenoid motor, an AC motor, a stepper motor, a piezoelectric caterpillar drive, a shape memory actuator drive, an electrochemical gas cell, a thermally driven gas cell, a bimetallic actuator, or the like. The drive train components may comprise one or more lead screws, cams, ratchets, jacks, pulleys, pawls, clamps, gears, nuts, slides, bearings, levers, beams, stoppers, plungers, sliders, brackets, guides, bearings, supports, bellows, caps, diaphragms, bags, heaters, or the like. In this regard, although the illustrated embodiment of the infusion pump utilizes a coaxially aligned drive train, the motor could be arranged in an offset or otherwise non-coaxial manner, relative to the longitudinal axis of the reservoir  205 . 
     As best shown in  FIG.  4   , the drive screw  209  mates with threads  402  internal to the slide  206 . When the motor assembly  207  is powered and operated, the drive screw  209  rotates, and the slide  206  is forced to translate in the axial direction  218 . In an exemplary embodiment, the infusion device  200  includes a sleeve  211  to prevent the slide  206  from rotating when the drive screw  209  of the drive system  208  rotates. Thus, rotation of the drive screw  209  causes the slide  206  to extend or retract relative to the drive motor assembly  207 . When the fluid infusion device is assembled and operational, the slide  206  contacts the plunger  217  to engage the reservoir  205  and control delivery of fluid from the infusion device  200 . In an exemplary embodiment, the shoulder portion  215  of the slide  206  contacts or otherwise engages the plunger  217  to displace the plunger  217  in the axial direction  218 . In alternative embodiments, the slide  206  may include a threaded tip  213  capable of being detachably engaged with internal threads  404  on the plunger  217  of the reservoir  205 , as described in detail in U.S. Pat. Nos. 6,248,093 and 6,485,465, which are incorporated by reference herein. 
     As illustrated in  FIG.  3   , the electronics assembly  204  includes control electronics  224  coupled to the display element  226 , with the housing  202  including a transparent window portion  228  that is aligned with the display element  226  to allow the display  226  to be viewed by the user when the electronics assembly  204  is disposed within the interior  214  of the housing  202 . The control electronics  224  generally represent the hardware, firmware, processing logic and/or software (or combinations thereof) configured to control operation of the motor assembly  207  and/or drive system  208 , as described in greater detail below in the context of  FIG.  5   . Whether such functionality is implemented as hardware, firmware, a state machine, or software depends upon the particular application and design constraints imposed on the embodiment. Those familiar with the concepts described here may implement such functionality in a suitable manner for each particular application, but such implementation decisions should not be interpreted as being restrictive or limiting. In an exemplary embodiment, the control electronics  224  includes one or more programmable controllers that may be programmed to control operation of the infusion device  200 . 
     The motor assembly  207  includes one or more electrical leads  236  adapted to be electrically coupled to the electronics assembly  204  to establish communication between the control electronics  224  and the motor assembly  207 . In response to command signals from the control electronics  224  that operate a motor driver (e.g., a power converter) to regulate the amount of power supplied to the motor from a power supply, the motor actuates the drive train components of the drive system  208  to displace the slide  206  in the axial direction  218  to force fluid from the reservoir  205  along a fluid path (including tubing  221  and an infusion set), thereby administering doses of the fluid contained in the reservoir  205  into the user&#39;s body. Preferably, the power supply is realized one or more batteries contained within the housing  202 . Alternatively, the power supply may be a solar panel, capacitor, AC or DC power supplied through a power cord, or the like. In some embodiments, the control electronics  224  may operate the motor of the motor assembly  207  and/or drive system  208  in a stepwise manner, typically on an intermittent basis; to administer discrete precise doses of the fluid to the user according to programmed delivery profiles. 
     Referring to  FIGS.  2 - 4   , as described above, the user interface  230  includes HMI elements, such as buttons  232  and a directional pad  234 , that are formed on a graphic keypad overlay  231  that overlies a keypad assembly  233 , which includes features corresponding to the buttons  232 , directional pad  234  or other user interface items indicated by the graphic keypad overlay  231 . When assembled, the keypad assembly  233  is coupled to the control electronics  224 , thereby allowing the HMI elements  232 ,  234  to be manipulated by the user to interact with the control electronics  224  and control operation of the infusion device  200 , for example, to administer a bolus of insulin, to change therapy settings, to change user preferences, to select display features, to set or disable alarms and reminders, and the like. In this regard, the control electronics  224  maintains and/or provides information to the display  226  regarding program parameters, delivery profiles, pump operation, alarms, warnings, statuses, or the like, which may be adjusted using the HMI elements  232 ,  234 . In various embodiments, the HMI elements  232 ,  234  may be realized as physical objects (e.g., buttons, knobs, joysticks, and the like) or virtual objects (e.g., using touch-sensing and/or proximity-sensing technologies). For example, in some embodiments, the display  226  may be realized as a touch screen or touch-sensitive display, and in such embodiments, the features and/or functionality of the HMI elements  232 ,  234  may be integrated into the display  226  and the HMI  230  may not be present. In some embodiments, the electronics assembly  204  may also include alert generating elements coupled to the control electronics  224  and suitably configured to generate one or more types of feedback, such as, without limitation: audible feedback; visual feedback; haptic (physical) feedback; or the like. 
     Referring to  FIGS.  3 - 4   , in accordance with one or more embodiments, the sensor assembly  210  includes a back plate structure  250  and a loading element  260 . The loading element  260  is disposed between the capping member  212  and a beam structure  270  that includes one or more beams having sensing elements disposed thereon that are influenced by compressive force applied to the sensor assembly  210  that deflects the one or more beams, as described in greater detail in U.S. Pat. No. 8,474,332, which is incorporated by reference herein. In exemplary embodiments, the back plate structure  250  is affixed, adhered, mounted, or otherwise mechanically coupled to the bottom surface  238  of the drive system  208  such that the back plate structure  250  resides between the bottom surface  238  of the drive system  208  and the housing cap  216 . The drive system capping member  212  is contoured to accommodate and conform to the bottom of the sensor assembly  210  and the drive system  208 . The drive system capping member  212  may be affixed to the interior of the housing  202  to prevent displacement of the sensor assembly  210  in the direction opposite the direction of force provided by the drive system  208  (e.g., the direction opposite direction  218 ). Thus, the sensor assembly  210  is positioned between the motor assembly  207  and secured by the capping member  212 , which prevents displacement of the sensor assembly  210  in a downward direction opposite the direction of the arrow that represents the axial direction  218 , such that the sensor assembly  210  is subjected to a reactionary compressive force when the drive system  208  and/or motor assembly  207  is operated to displace the slide  206  in the axial direction  218  in opposition to the fluid pressure in the reservoir  205 . Under normal operating conditions, the compressive force applied to the sensor assembly  210  is correlated with the fluid pressure in the reservoir  205 . As shown, electrical leads  240  are adapted to electrically couple the sensing elements of the sensor assembly  210  to the electronics assembly  204  to establish communication to the control electronics  224 , wherein the control electronics  224  are configured to measure, receive, or otherwise obtain electrical signals from the sensing elements of the sensor assembly  210  that are indicative of the force applied by the drive system  208  in the axial direction  218 . 
       FIG.  5    depicts an exemplary embodiment of an infusion system  500  suitable for use with an infusion device  502 , such as any one of the infusion devices  102 ,  200  described above. The infusion system  500  is capable of controlling or otherwise regulating a physiological condition in the body  501  of a patient to a desired (or target) value or otherwise maintain the condition within a range of acceptable values in an automated or autonomous manner. In one or more exemplary embodiments, the condition being regulated is sensed, detected, measured or otherwise quantified by a sensing arrangement  504  (e.g., a blood glucose sensing arrangement  504 ) communicatively coupled to the infusion device  502 . However, it should be noted that in alternative embodiments, the condition being regulated by the infusion system  500  may be correlative to the measured values obtained by the sensing arrangement  504 . That said, for clarity and purposes of explanation, the subject matter may be described herein in the context of the sensing arrangement  504  being realized as a glucose sensing arrangement that senses, detects, measures or otherwise quantifies the patient&#39;s glucose level, which is being regulated in the body  501  of the patient by the infusion system  500 . 
     In exemplary embodiments, the sensing arrangement  504  includes one or more interstitial glucose sensing elements that generate or otherwise output electrical signals (alternatively referred to herein as measurement signals) having a signal characteristic that is correlative to, influenced by, or otherwise indicative of the relative interstitial fluid glucose level in the body  501  of the patient. The output electrical signals are filtered or otherwise processed to obtain a measurement value indicative of the patient&#39;s interstitial fluid glucose level. In exemplary embodiments, a blood glucose meter  530 , such as a finger stick device, is utilized to directly sense, detect, measure or otherwise quantify the blood glucose in the body  501  of the patient. In this regard, the blood glucose meter  530  outputs or otherwise provides a measured blood glucose value that may be utilized as a reference measurement for calibrating the sensing arrangement  504  and converting a measurement value indicative of the patient&#39;s interstitial fluid glucose level into a corresponding calibrated blood glucose value. For purposes of explanation, the calibrated blood glucose value calculated based on the electrical signals output by the sensing element(s) of the sensing arrangement  504  may alternatively be referred to herein as the sensor glucose value, the sensed glucose value, or variants thereof. 
     In exemplary embodiments, the infusion system  500  also includes one or more additional sensing arrangements  506 ,  508  configured to sense, detect, measure or otherwise quantify a characteristic of the body  501  of the patient that is indicative of a condition in the body  501  of the patient. In this regard, in addition to the glucose sensing arrangement  504 , one or more auxiliary sensing arrangements  506  may be worn, carried, or otherwise associated with the body  501  of the patient to measure characteristics or conditions of the patient (or the patient&#39;s activity) that may influence the patient&#39;s glucose levels or insulin sensitivity. For example, a heart rate sensing arrangement  506  could be worn on or otherwise associated with the patient&#39;s body  501  to sense, detect, measure or otherwise quantify the patient&#39;s heart rate, which, in turn, may be indicative of exercise (and the intensity thereof) that is likely to influence the patient&#39;s glucose levels or insulin response in the body  501 . In yet another embodiment, another invasive, interstitial, or subcutaneous sensing arrangement  506  may be inserted into the body  501  of the patient to obtain measurements of another physiological condition that may be indicative of exercise (and the intensity thereof), such as, for example, a lactate sensor, a ketone sensor, or the like. Depending on the embodiment, the auxiliary sensing arrangement(s)  506  could be realized as a standalone component worn by the patient, or alternatively, the auxiliary sensing arrangement(s)  506  may be integrated with the infusion device  502  or the glucose sensing arrangement  504 . 
     The illustrated infusion system  500  also includes an acceleration sensing arrangement  508  (or accelerometer) that may be worn on or otherwise associated with the patient&#39;s body  501  to sense, detect, measure or otherwise quantify an acceleration of the patient&#39;s body  501 , which, in turn, may be indicative of exercise or some other condition in the body  501  that is likely to influence the patient&#39;s insulin response. While the acceleration sensing arrangement  508  is depicted as being integrated into the infusion device  502  in  FIG.  5   , in alternative embodiments, the acceleration sensing arrangement  508  may be integrated with another sensing arrangement  504 ,  506  on the body  501  of the patient, or the acceleration sensing arrangement  508  may be realized as a separate standalone component that is worn by the patient. 
     In the illustrated embodiment, the pump control system  520  generally represents the electronics and other components of the infusion device  502  that control operation of the fluid infusion device  502  according to a desired infusion delivery program in a manner that is influenced by the sensed glucose value indicating the current glucose level in the body  501  of the patient. For example, to support a closed-loop operating mode, the pump control system  520  maintains, receives, or otherwise obtains a target or commanded glucose value, and automatically generates or otherwise determines dosage commands for operating an actuation arrangement, such as a motor  532 , to displace the plunger  517  and deliver insulin to the body  501  of the patient based on the difference between the sensed glucose value and the target glucose value. In other operating modes, the pump control system  520  may generate or otherwise determine dosage commands configured to maintain the sensed glucose value below an upper glucose limit, above a lower glucose limit, or otherwise within a desired range of glucose values. In practice, the infusion device  502  may store or otherwise maintain the target value, upper and/or lower glucose limit(s), insulin delivery limit(s), and/or other glucose threshold value(s) in a data storage element accessible to the pump control system  520 . As described in greater detail, in one or more exemplary embodiments, the pump control system  520  automatically adjusts or adapts one or more parameters or other control information used to generate commands for operating the motor  532  in a manner that accounts for a likely change in the patient&#39;s glucose level or insulin response resulting from a meal, exercise, or other activity. 
     Still referring to  FIG.  5   , the target glucose value and other threshold glucose values utilized by the pump control system  520  may be received from an external component (e.g., CCD  106  and/or computing device  108 ) or be input by a patient via a user interface element  540  associated with the infusion device  502 . In practice, the one or more user interface element(s)  540  associated with the infusion device  502  typically include at least one input user interface element, such as, for example, a button, a keypad, a keyboard, a knob, a joystick, a mouse, a touch panel, a touchscreen, a microphone or another audio input device, and/or the like. Additionally, the one or more user interface element(s)  540  include at least one output user interface element, such as, for example, a display element (e.g., a light-emitting diode or the like), a display device (e.g., a liquid crystal display or the like), a speaker or another audio output device, a haptic feedback device, or the like, for providing notifications or other information to the patient. It should be noted that although  FIG.  5    depicts the user interface element(s)  540  as being separate from the infusion device  502 , in practice, one or more of the user interface element(s)  540  may be integrated with the infusion device  502 . Furthermore, in some embodiments, one or more user interface element(s)  540  are integrated with the sensing arrangement  504  in addition to and/or in alternative to the user interface element(s)  540  integrated with the infusion device  502 . The user interface element(s)  540  may be manipulated by the patient to operate the infusion device  502  to deliver correction boluses, adjust target and/or threshold values, modify the delivery control scheme or operating mode, and the like, as desired. 
     Still referring to  FIG.  5   , in the illustrated embodiment, the infusion device  502  includes a motor control module  512  coupled to a motor  532  (e.g., motor assembly  207 ) that is operable to displace a plunger  517  (e.g., plunger  217 ) in a reservoir (e.g., reservoir  205 ) and provide a desired amount of fluid to the body  501  of a patient. In this regard, displacement of the plunger  517  results in the delivery of a fluid, such as insulin, that is capable of influencing the patient&#39;s physiological condition to the body  501  of the patient via a fluid delivery path (e.g., via tubing  221  of an infusion set  225 ). A motor driver module  514  is coupled between an energy source  518  and the motor  532 . The motor control module  512  is coupled to the motor driver module  514 , and the motor control module  512  generates or otherwise provides command signals that operate the motor driver module  514  to provide current (or power) from the energy source  518  to the motor  532  to displace the plunger  517  in response to receiving, from a pump control system  520 , a dosage command indicative of the desired amount of fluid to be delivered. 
     In exemplary embodiments, the energy source  518  is realized as a battery housed within the infusion device  502  (e.g., within housing  202 ) that provides direct current (DC) power. In this regard, the motor driver module  514  generally represents the combination of circuitry, hardware and/or other electrical components configured to convert or otherwise transfer DC power provided by the energy source  518  into alternating electrical signals applied to respective phases of the stator windings of the motor  532  that result in current flowing through the stator windings that generates a stator magnetic field and causes the rotor of the motor  532  to rotate. The motor control module  512  is configured to receive or otherwise obtain a commanded dosage from the pump control system  520 , convert the commanded dosage to a commanded translational displacement of the plunger  517 , and command, signal, or otherwise operate the motor driver module  514  to cause the rotor of the motor  532  to rotate by an amount that produces the commanded translational displacement of the plunger  517 . For example, the motor control module  512  may determine an amount of rotation of the rotor required to produce translational displacement of the plunger  517  that achieves the commanded dosage received from the pump control system  520 . Based on the current rotational position (or orientation) of the rotor with respect to the stator that is indicated by the output of the rotor sensing arrangement  516 , the motor control module  512  determines the appropriate sequence of alternating electrical signals to be applied to the respective phases of the stator windings that should rotate the rotor by the determined amount of rotation from its current position (or orientation). In embodiments where the motor  532  is realized as a BLDC motor, the alternating electrical signals commutate the respective phases of the stator windings at the appropriate orientation of the rotor magnetic poles with respect to the stator and in the appropriate order to provide a rotating stator magnetic field that rotates the rotor in the desired direction. Thereafter, the motor control module  512  operates the motor driver module  514  to apply the determined alternating electrical signals (e.g., the command signals) to the stator windings of the motor  532  to achieve the desired delivery of fluid to the patient. 
     When the motor control module  512  is operating the motor driver module  514 , current flows from the energy source  518  through the stator windings of the motor  532  to produce a stator magnetic field that interacts with the rotor magnetic field. In some embodiments, after the motor control module  512  operates the motor driver module  514  and/or motor  532  to achieve the commanded dosage, the motor control module  512  ceases operating the motor driver module  514  and/or motor  532  until a subsequent dosage command is received. In this regard, the motor driver module  514  and the motor  532  enter an idle state during which the motor driver module  514  effectively disconnects or isolates the stator windings of the motor  532  from the energy source  518 . In other words, current does not flow from the energy source  518  through the stator windings of the motor  532  when the motor  532  is idle, and thus, the motor  532  does not consume power from the energy source  518  in the idle state, thereby improving efficiency. 
     Depending on the embodiment, the motor control module  512  may be implemented or realized with a general purpose processor, a microprocessor, a controller, a microcontroller, a state machine, a content addressable memory, an application specific integrated circuit, a field programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. In exemplary embodiments, the motor control module  512  includes or otherwise accesses a data storage element or memory, including any sort of random access memory (RAM), read only memory (ROM), flash memory, registers, hard disks, removable disks, magnetic or optical mass storage, or any other short or long term storage media or other non-transitory computer-readable medium, which is capable of storing programming instructions for execution by the motor control module  512 . The computer-executable programming instructions, when read and executed by the motor control module  512 , cause the motor control module  512  to perform or otherwise support the tasks, operations, functions, and processes described herein. 
     It should be appreciated that  FIG.  5    is a simplified representation of the infusion device  502  for purposes of explanation and is not intended to limit the subject matter described herein in any way. In this regard, depending on the embodiment, some features and/or functionality of the sensing arrangement  504  may implemented by or otherwise integrated into the pump control system  520 , or vice versa. Similarly, in practice, the features and/or functionality of the motor control module  512  may implemented by or otherwise integrated into the pump control system  520 , or vice versa. Furthermore, the features and/or functionality of the pump control system  520  may be implemented by control electronics  224  located in the fluid infusion device  502 , while in alternative embodiments, the pump control system  520  may be implemented by a remote computing device that is physically distinct and/or separate from the infusion device  502 , such as, for example, the CCD  106  or the computing device  108 . 
       FIG.  6    depicts an exemplary embodiment of a pump control system  600  suitable for use as the pump control system  520  in  FIG.  5    in accordance with one or more embodiments. The illustrated pump control system  600  includes, without limitation, a pump control module  602 , a communications interface  604 , and a data storage element (or memory)  606 . The pump control module  602  is coupled to the communications interface  604  and the memory  606 , and the pump control module  602  is suitably configured to support the operations, tasks, and/or processes described herein. In various embodiments, the pump control module  602  is also coupled to one or more user interface elements (e.g., user interface  230 ,  540 ) for receiving user inputs (e.g., target glucose values or other glucose thresholds) and providing notifications, alerts, or other therapy information to the patient. 
     The communications interface  604  generally represents the hardware, circuitry, logic, firmware and/or other components of the pump control system  600  that are coupled to the pump control module  602  and configured to support communications between the pump control system  600  and the various sensing arrangements  504 ,  506 ,  508 . In this regard, the communications interface  604  may include or otherwise be coupled to one or more transceiver modules capable of supporting wireless communications between the pump control system  520 ,  600  and the sensing arrangement  504 ,  506 ,  508 . For example, the communications interface  604  may be utilized to receive sensor measurement values or other measurement data from each sensing arrangement  504 ,  506 ,  508  in an infusion system  500 . In other embodiments, the communications interface  604  may be configured to support wired communications to/from the sensing arrangement(s)  504 ,  506 ,  508 . In various embodiments, the communications interface  604  may also support communications with another electronic device (e.g., CCD  106  and/or computer  108 ) in an infusion system (e.g., to upload sensor measurement values to a server or other computing device, receive control information from a server or other computing device, and the like). 
     The pump control module  602  generally represents the hardware, circuitry, logic, firmware and/or other component of the pump control system  600  that is coupled to the communications interface  604  and configured to determine dosage commands for operating the motor  532  to deliver fluid to the body  501  based on measurement data received from the sensing arrangements  504 ,  506 ,  508  and perform various additional tasks, operations, functions and/or operations described herein. For example, in exemplary embodiments, pump control module  602  implements or otherwise executes a command generation application  610  that supports one or more autonomous operating modes and calculates or otherwise determines dosage commands for operating the motor  532  of the infusion device  502  in an autonomous operating mode based at least in part on a current measurement value for a condition in the body  501  of the patient. For example, in a closed-loop operating mode, the command generation application  610  may determine a dosage command for operating the motor  532  to deliver insulin to the body  501  of the patient based at least in part on the current glucose measurement value most recently received from the sensing arrangement  504  to regulate the patient&#39;s blood glucose level to a target reference glucose value. Additionally, the command generation application  610  may generate dosage commands for boluses that are manually-initiated or otherwise instructed by a patient via a user interface element. 
     In exemplary embodiments, the pump control module  602  also implements or otherwise executes a personalization application  608  that is cooperatively configured to interact with the command generation application  610  to support adjusting dosage commands or control information dictating the manner in which dosage commands are generated in a personalized, patient-specific manner. In this regard, in some embodiments, based on correlations between current or recent measurement data and the current operational context relative to historical data associated with the patient, the personalization application  608  may adjust or otherwise modify values for one or more parameters utilized by the command generation application  610  when determining dosage commands, for example, by modifying a parameter value at a register or location in memory  606  referenced by the command generation application  610 . In yet other embodiments, the personalization application  608  may predict meals or other events or activities that are likely to be engaged in by the patient and output or otherwise provide an indication of the predicted patient behavior for confirmation or modification by the patient, which, in turn, may then be utilized to adjust the manner in which dosage commands are generated to regulate glucose in a manner that accounts for the patient&#39;s behavior in a personalized manner. 
     Still referring to  FIG.  6   , depending on the embodiment, the pump control module  602  may be implemented or realized with at least one general purpose processor device, a microprocessor, a controller, a microcontroller, a state machine, a content addressable memory, an application specific integrated circuit, a field programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. In this regard, the steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in firmware, in a software module executed by the pump control module  602 , or in any practical combination thereof. In exemplary embodiments, the pump control module  602  includes or otherwise accesses the data storage element or memory  606 , which may be realized using any sort of non-transitory computer-readable medium capable of storing programming instructions for execution by the pump control module  602 . The computer-executable programming instructions, when read and executed by the pump control module  602 , cause the pump control module  602  to implement or otherwise generate the applications  608 ,  610  and perform tasks, operations, functions, and processes described herein. 
     It should be understood that  FIG.  6    is a simplified representation of a pump control system  600  for purposes of explanation and is not intended to limit the subject matter described herein in any way. For example, in some embodiments, the features and/or functionality of the motor control module  512  may be implemented by or otherwise integrated into the pump control system  600  and/or the pump control module  602 , for example, by the command generation application  610  converting the dosage command into a corresponding motor command, in which case, the separate motor control module  512  may be absent from an embodiment of the infusion device  502 . 
       FIG.  7    depicts an exemplary closed-loop control system  700  that may be implemented by a pump control system  520 ,  600  to provide a closed-loop operating mode that autonomously regulates a condition in the body of a patient to a reference (or target) value. It should be appreciated that  FIG.  7    is a simplified representation of the control system  700  for purposes of explanation and is not intended to limit the subject matter described herein in any way. 
     In exemplary embodiments, the control system  700  receives or otherwise obtains a target glucose value at input  702 . In some embodiments, the target glucose value may be stored or otherwise maintained by the infusion device  502  (e.g., in memory  606 ), however, in some alternative embodiments, the target value may be received from an external component (e.g., CCD  106  and/or computer  108 ). In one or more embodiments, the target glucose value may be calculated or otherwise determined prior to entering the closed-loop operating mode based on one or more patient-specific control parameters. For example, the target blood glucose value may be calculated based at least in part on a patient-specific reference basal rate and a patient-specific daily insulin requirement, which are determined based on historical delivery information over a preceding interval of time (e.g., the amount of insulin delivered over the preceding 24 hours). The control system  700  also receives or otherwise obtains a current glucose measurement value (e.g., the most recently obtained sensor glucose value) from the sensing arrangement  504  at input  704 . The illustrated control system  700  implements or otherwise provides proportional-integral-derivative (PID) control to determine or otherwise generate delivery commands for operating the motor  532  based at least in part on the difference between the target glucose value and the current glucose measurement value. In this regard, the PID control attempts to minimize the difference between the measured value and the target value, and thereby regulates the measured value to the desired value. PID control parameters are applied to the difference between the target glucose level at input  702  and the measured glucose level at input  704  to generate or otherwise determine a dosage (or delivery) command provided at output  730 . Based on that delivery command, the motor control module  512  operates the motor  532  to deliver insulin to the body of the patient to influence the patient&#39;s glucose level, and thereby reduce the difference between a subsequently measured glucose level and the target glucose level. 
     The illustrated control system  700  includes or otherwise implements a summation block  706  configured to determine a difference between the target value obtained at input  702  and the measured value obtained from the sensing arrangement  504  at input  704 , for example, by subtracting the target value from the measured value. The output of the summation block  706  represents the difference between the measured and target values, which is then provided to each of a proportional term path, an integral term path, and a derivative term path. The proportional term path includes a gain block  720  that multiplies the difference by a proportional gain coefficient, K P , to obtain the proportional term. The integral term path includes an integration block  708  that integrates the difference and a gain block  722  that multiplies the integrated difference by an integral gain coefficient, K I , to obtain the integral term. The derivative term path includes a derivative block  710  that determines the derivative of the difference and a gain block  724  that multiplies the derivative of the difference by a derivative gain coefficient, K D , to obtain the derivative term. The proportional term, the integral term, and the derivative term are then added or otherwise combined to obtain a delivery command that is utilized to operate the motor at output  730 . Various implementation details pertaining to closed-loop PID control and determining gain coefficients are described in greater detail in U.S. Pat. No. 7,402,153, which is incorporated by reference. 
     In one or more exemplary embodiments, the PID gain coefficients are patient-specific and dynamically calculated or otherwise determined prior to entering the closed-loop operating mode based on historical insulin delivery information (e.g., amounts and/or timings of previous dosages, historical correction bolus information, or the like), historical sensor measurement values, historical reference blood glucose measurement values, user-reported or user-input events (e.g., meals, exercise, and the like), and the like. In this regard, one or more patient-specific control parameters (e.g., an insulin sensitivity factor, a daily insulin requirement, an insulin limit, a reference basal rate, a reference fasting glucose, an active insulin action duration, pharmodynamical time constants, or the like) may be utilized to compensate, correct, or otherwise adjust the PID gain coefficients to account for various operating conditions experienced and/or exhibited by the infusion device  502 . The PID gain coefficients may be maintained by the memory  606  accessible to the pump control module  602 . In this regard, the memory  606  may include a plurality of registers associated with the control parameters for the PID control. For example, a first parameter register may store the target glucose value and be accessed by or otherwise coupled to the summation block  706  at input  702 , and similarly, a second parameter register accessed by the proportional gain block  720  may store the proportional gain coefficient, a third parameter register accessed by the integration gain block  722  may store the integration gain coefficient, and a fourth parameter register accessed by the derivative gain block  724  may store the derivative gain coefficient. 
     In one or more exemplary embodiments, one or more parameters of the closed-loop control system  700  are automatically adjusted or adapted in a personalized manner to account for potential changes in the patient&#39;s glucose level or insulin sensitivity resulting from meals, exercise, or other events or activities. For example, in one or more embodiments, the target glucose value may be decreased in advance of a predicted meal event to achieve an increase in the insulin infusion rate to effectively pre-bolus a meal, and thereby reduce the likelihood of postprandial hyperglycemia. Additionally or alternatively, the time constant or gain coefficient associated with one or more paths of the closed-loop control system  700  may be adjusted to tune the responsiveness to deviations between the measured glucose value and the target glucose value. For example, based on the particular type of meal being consumed or the particular time of day during which the meal is consumed, the time constant associated with the derivative block  710  or derivative term path may be adjusted to make the closed-loop control more or less aggressive in response to an increase in the patient&#39;s glucose level based on the patient&#39;s historical glycemic response to the particular type of meal. 
       FIG.  8    depicts an exemplary embodiment of a patient monitoring system  800 . The patient monitoring system  800  includes a medical device  802  that is communicatively coupled to a sensing element  804  that is inserted into the body of a patient or otherwise worn by the patient to obtain measurement data indicative of a physiological condition in the body of the patient, such as a sensed glucose level. The medical device  802  is communicatively coupled to a client device  806  via a communications network  810 , with the client device  806  being communicatively coupled to a remote device  814  via another communications network  812 . In this regard, the client device  806  may function as an intermediary for uploading or otherwise providing measurement data from the medical device  802  to the remote device  814 . It should be appreciated that  FIG.  8    depicts a simplified representation of a patient monitoring system  800  for purposes of explanation and is not intended to limit the subject matter described herein in any way. 
     In exemplary embodiments, the client device  806  is realized as a mobile phone, a smartphone, a tablet computer, or other similar mobile electronic device; however, in other embodiments, the client device  806  may be realized as any sort of electronic device capable of communicating with the medical device  802  via network  810 , such as a laptop or notebook computer, a desktop computer, or the like. In exemplary embodiments, the network  810  is realized as a Bluetooth network, a ZigBee network, or another suitable personal area network. That said, in other embodiments, the network  810  could be realized as a wireless ad hoc network, a wireless local area network (WLAN), or local area network (LAN). The client device  806  includes or is coupled to a display device, such as a monitor, screen, or another conventional electronic display, capable of graphically presenting data and/or information pertaining to the physiological condition of the patient. The client device  806  also includes or is otherwise associated with a user input device, such as a keyboard, a mouse, a touchscreen, or the like, capable of receiving input data and/or other information from the user of the client device  806 . 
     In exemplary embodiments, a user, such as the patient, the patient&#39;s doctor or another healthcare provider, or the like, manipulates the client device  806  to execute a client application  808  that supports communicating with the medical device  802  via the network  810 . In this regard, the client application  808  supports establishing a communications session with the medical device  802  on the network  810  and receiving data and/or information from the medical device  802  via the communications session. The medical device  802  may similarly execute or otherwise implement a corresponding application or process that supports establishing the communications session with the client application  808 . The client application  808  generally represents a software module or another feature that is generated or otherwise implemented by the client device  806  to support the processes described herein. Accordingly, the client device  806  generally includes a processing system and a data storage element (or memory) capable of storing programming instructions for execution by the processing system, that, when read and executed, cause processing system to create, generate, or otherwise facilitate the client application  808  and perform or otherwise support the processes, tasks, operations, and/or functions described herein. Depending on the embodiment, the processing system may be implemented using any suitable processing system and/or device, such as, for example, one or more processor devices, central processing units (CPUs), controllers, microprocessors, microcontrollers, processing cores and/or other hardware computing resources configured to support the operation of the processing system described herein. Similarly, the data storage element or memory may be realized as a random-access memory (RAM), read only memory (ROM), flash memory, magnetic or optical mass storage, or any other suitable non-transitory short or long-term data storage or other computer-readable media, and/or any suitable combination thereof. 
     In one or more embodiments, the client device  806  and the medical device  802  establish an association (or pairing) with one another over the network  810  to support subsequently establishing a point-to-point or peer-to-peer communications session between the medical device  802  and the client device  806  via the network  810 . For example, in accordance with one embodiment, the network  810  is realized as a Bluetooth network, wherein the medical device  802  and the client device  806  are paired with one another (e.g., by obtaining and storing network identification information for one another) by performing a discovery procedure or another suitable pairing procedure. The pairing information obtained during the discovery procedure allows either of the medical device  802  or the client device  806  to initiate the establishment of a secure communications session via the network  810 . 
     In one or more exemplary embodiments, the client application  808  is also configured to store or otherwise maintain an address and/or other identification information for the remote device  814  on the second network  812 . In this regard, the second network  812  may be physically and/or logically distinct from the network  810 , such as, for example, the Internet, a cellular network, a wide area network (WAN), or the like. The remote device  814  generally represents a server or other computing device configured to receive and analyze or otherwise monitor measurement data, event log data, and potentially other information obtained for the patient associated with the medical device  802 . In exemplary embodiments, the remote device  814  is coupled to a database  816  configured to store or otherwise maintain data associated with individual patients. In practice, the remote device  814  may reside at a location that is physically distinct and/or separate from the medical device  802  and the client device  806 , such as, for example, at a facility that is owned and/or operated by or otherwise affiliated with a manufacturer of the medical device  802 . For purposes of explanation, but without limitation, the remote device  814  may alternatively be referred to herein as a server. 
     Still referring to  FIG.  8   , the sensing element  804  generally represents the component of the patient monitoring system  800  that is configured to generate, produce, or otherwise output one or more electrical signals indicative of a physiological condition that is sensed, measured, or otherwise quantified by the sensing element  804 . In this regard, the physiological condition of a patient influences a characteristic of the electrical signal output by the sensing element  804 , such that the characteristic of the output signal corresponds to or is otherwise correlative to the physiological condition that the sensing element  804  is sensitive to. In exemplary embodiments, the sensing element  804  is realized as an interstitial glucose sensing element inserted at a location on the body of the patient that generates an output electrical signal having a current (or voltage) associated therewith that is correlative to the interstitial fluid glucose level that is sensed or otherwise measured in the body of the patient by the sensing element  804 . 
     The medical device  802  generally represents the component of the patient monitoring system  800  that is communicatively coupled to the output of the sensing element  804  to receive or otherwise obtain the measurement data samples from the sensing element  804  (e.g., the measured glucose and characteristic impedance values), store or otherwise maintain the measurement data samples, and upload or otherwise transmit the measurement data to the remote device  814  or server via the client device  806 . In one or more embodiments, the medical device  802  is realized as an infusion device  102 ,  200 ,  502  configured to deliver a fluid, such as insulin, to the body of the patient. That said, in other embodiments, the medical device  802  could be a standalone sensing or monitoring device separate and independent from an infusion device (e.g., sensing arrangement  104 ,  504 ). It should be noted that although  FIG.  8    depicts the medical device  802  and the sensing element  804  as separate components, in practice, the medical device  802  and the sensing element  804  may be integrated or otherwise combined to provide a unitary device that can be worn by the patient. 
     In exemplary embodiments, the medical device  802  includes a control module  822 , a data storage element  824  (or memory), and a communications interface  826 . The control module  822  generally represents the hardware, circuitry, logic, firmware and/or other component(s) of the medical device  802  that is coupled to the sensing element  804  to receive the electrical signals output by the sensing element  804  and perform or otherwise support various additional tasks, operations, functions and/or processes described herein. Depending on the embodiment, the control module  822  may be implemented or realized with a general purpose processor device, a microprocessor device, a controller, a microcontroller, a state machine, a content addressable memory, an application specific integrated circuit, a field programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. In some embodiments, the control module  822  includes an analog-to-digital converter (ADC) or another similar sampling arrangement that samples or otherwise converts an output electrical signal received from the sensing element  804  into corresponding digital measurement data value. In other embodiments, the sensing element  804  may incorporate an ADC and output a digital measurement value. 
     The communications interface  826  generally represents the hardware, circuitry, logic, firmware and/or other components of the medical device  802  that are coupled to the control module  822  for outputting data and/or information from/to the medical device  802  to/from the client device  806 . For example, the communications interface  826  may include or otherwise be coupled to one or more transceiver modules capable of supporting wireless communications between the medical device  802  and the client device  806 . In exemplary embodiments, the communications interface  826  is realized as a Bluetooth transceiver or adapter configured to support Bluetooth Low Energy (BLE) communications. 
     In exemplary embodiments, the remote device  814  receives, from the client device  806 , measurement data values associated with a particular patient (e.g., sensor glucose measurements, acceleration measurements, and the like) that were obtained using the sensing element  804 , and the remote device  814  stores or otherwise maintains the historical measurement data in the database  816  in association with the patient (e.g., using one or more unique patient identifiers). Additionally, the remote device  814  may also receive, from or via the client device  806 , meal data or other event log data that may be input or otherwise provided by the patient (e.g., via client application  808 ) and store or otherwise maintain historical meal data and other historical event or activity data associated with the patient in the database  816 . In this regard, the meal data include, for example, a time or timestamp associated with a particular meal event, a meal type or other information indicative of the content or nutritional characteristics of the meal, and an indication of the size associated with the meal. In exemplary embodiments, the remote device  814  also receives historical fluid delivery data corresponding to basal or bolus dosages of fluid delivered to the patient by an infusion device  102 ,  200 ,  502 . For example, the client application  808  may communicate with an infusion device  102 ,  200 ,  502  to obtain insulin delivery dosage amounts and corresponding timestamps from the infusion device  102 ,  200 ,  502 , and then upload the insulin delivery data to the remote device  814  for storage in association with the particular patient. The remote device  814  may also receive geolocation data and potentially other contextual data associated with a device  802 ,  806  from the client device  806  and/or client application  808 , and store or otherwise maintain the historical operational context data in association with the particular patient. In this regard, one or more of the devices  802 ,  806  may include a global positioning system (GPS) receiver or similar modules, components or circuitry capable of outputting or otherwise providing data characterizing the geographic location of the respective device  802 ,  806  in real-time. 
     The historical patient data may be analyzed by one or more of the remote device  814 , the client device  806 , and/or the medical device  802  to alter or adjust operation of an infusion device  102 ,  200 ,  502  to influence fluid delivery in a personalized manner. For example, the patient&#39;s historical meal data and corresponding measurement data or other contextual data may be analyzed to predict a future time when the next meal is likely to be consumed by the patient, the likelihood of a future meal event within a specific time period, the likely size or amount of carbohydrates associated with a future meal, the likely type or nutritional content of the future meal, and/or the like. Moreover, the patient&#39;s historical measurement data for postprandial periods following historical meal events may be analyzed to model or otherwise characterize the patient&#39;s glycemic response to the predicted size and type of meal for the current context (e.g., time of day, day of week, geolocation, etc.). One or more aspects of the infusion device  102 ,  200 ,  502  that control or regulate insulin delivery may then be modified or adjusted to proactively account for the patient&#39;s likely meal activity and glycemic response. 
     In one or more exemplary embodiments, the remote device  814  utilizes machine learning to determine which combination of historical sensor glucose measurement data, historical delivery data, historical auxiliary measurement data (e.g., historical acceleration measurement data, historical heart rate measurement data, and/or the like), historical event log data, historical geolocation data, and other historical or contextual data are correlated to or predictive of the occurrence of a particular event, activity, or metric for a particular patient, and then determines a corresponding equation, function, or model for calculating the value of the parameter of interest based on that set of input variables. Thus, the model is capable of characterizing or mapping a particular combination of one or more of the current (or recent) sensor glucose measurement data, auxiliary measurement data, delivery data, geographic location, patient behavior or activities, and the like to a value representative of the current probability or likelihood of a particular event or activity or a current value for a parameter of interest. It should be noted that since each patient&#39;s physiological response may vary from the rest of the population, the subset of input variables that are predictive of or correlative for a particular patient may vary from other patients. Additionally, the relative weightings applied to the respective variables of that predictive subset may also vary from other patients who may have common predictive subsets, based on differing correlations between a particular input variable and the historical data for that particular patient. It should be noted that any number of different machine learning techniques may be utilized by the remote device  814  to determine what input variables are predictive for a current patient of interest, such as, for example, artificial neural networks, genetic programming, support vector machines, Bayesian networks, probabilistic machine learning models, or other Bayesian techniques, fuzzy logic, heuristically derived combinations, or the like. 
     An insulin infusion device of the type described above can be suitably configured to calculate an upper limit on the insulin delivery rate that can be used during an automatic basal insulin delivery mode. In such an automatic mode, the infusion device automatically delivers insulin (at a rate that is less than or equal to the calculated upper limit). This upper limit, Umax, can be dynamically adjusted to better suit the needs of the user. For example, an exemplary embodiment of the infusion device adapts Umax once a day, e.g., at midnight. In addition to the basal insulin that is automatically provided by the infusion device, the user (or a caregiver) can also issue additional insulin boluses by announcing (entering) a carbohydrate value for a meal and/or by entering a blood glucose meter reading. 
     If the insulin infusion device is already delivering insulin at the Umax rate (the upper limit) while in the automatic basal insulin mode, then it can be assumed that the patient needs additional insulin to better regulate blood glucose levels. To this end, the infusion device can respond to such a condition by considering whether a correction bolus is needed. In certain embodiments, when the automated insulin delivery rate exceeds a specified rate for at least a designated period of time, then the infusion device reacts by initiating an automated correction bolus procedure to calculate and possibly deliver a correction bolus. If the calculated correction bolus is above a baseline threshold amount and is determined to be safe to administer, then the infusion device issues the correction bolus as a supplement to the basal insulin that is already being delivered. As one non-limiting example, if the automatic basal insulin rate has been above a specified percentage of Umax (e.g., 90%, 92.5%, etc.) for at least one hour, then the insulin infusion device will proceed with the automated correction bolus procedure. As another non-limiting example, if the automatic basal insulin rate reaches Umax at any time, then the automated correction bolus procedure will be triggered. These and other triggering conditions and mechanisms can be employed in an exemplary embodiment of the insulin infusion device. 
     In accordance with the embodiments presented here, the initial (potential) correction bolus is calculated as follows: 
                     Correction   ⁢           ⁢   Bolus     =         BG   -   Target     ISF     -   IOB             (     Equation   ⁢           ⁢   1     )               
In this expression:
         BG is a blood glucose measurement for the user;   Target is the desired blood glucose level for the user (which is user-adjustable in the manual delivery mode, and is fixed during the automatic mode);   ISF is the user&#39;s Insulin Sensitivity Factor (which is user-adjustable in the manual delivery mode, and is determined according to       

     
       
         
           
             
               1 
               ⁢ 
               8 
               ⁢ 
               0 
               ⁢ 
               0 
             
             
               Total 
               ⁢ 
               
                   
               
               ⁢ 
               Daily 
               ⁢ 
               
                   
               
               ⁢ 
               Insulin 
               ⁢ 
               
                   
               
               ⁢ 
               Dose 
             
           
         
       
         
         
           
              during the automatic mode); and 
             IOB is the current Insulin On Board, or active insulin, that is determined by accounting for all bolus insulin deliveries, and by reducing the amount over time according to the user setting for active insulin time. For this example, the total daily insulin dose is a median value that is calculated based on two to six days of the patient&#39;s total daily dose. 
           
         
       
    
     The initial correction bolus can be scaled by a multiplier that has a value between 0.0 and 1.0 to reduce the bolus amount as needed. More specifically, the infusion device intelligently scales the initial correction bolus amount (or withholds the bolus) to prevent the risk of hypoglycemia following delivery of the correction bolus. 
     In accordance with certain embodiments, the insulin infusion device performs a correction bolus check during the automatic mode under the following conditions: a BG value (e.g., a BG meter reading or a glucose sensor reading) is entered into the device or is otherwise obtained by the device; the BG value is greater than a threshold value, such as 150 mg/dL or 120 mg/dL; and the calculated correction bolus value is greater than zero after deducting active insulin and applying safe correction bolus logic. If all of these conditions are met, then the infusion device provides a message recommending a correction bolus to the user. The user may decide to either accept the correction bolus or reject it. 
     As mentioned above, the baseline initial correction bolus value can be scaled, based on a safe correction bolus methodology utilized by the infusion device. The safe correction bolus methodology incorporates a prediction model to estimate whether the correction bolus is likely to lower the user&#39;s BG level below a stated low glucose threshold (such as 80 mg/dL) in the near future (such as within the next two to four hours). If the BG level is predicted to go below the low glucose threshold value, then the initial correction bolus value is incrementally reduced until the predicted level remains above the threshold value. 
     The improved methodology described here delivers correction boluses automatically without any user input or acknowledgement. The core computation of the automatic correction bolus is based on Equation 1 set forth above. However, the correction target is lowered from a default, standard, or typical value to a reduced value, such as 120 mg/dL. Moreover, correction boluses do not require BG meter readings; they can be computed based on readings from a patient-worn continuous glucose sensor. That said, if a valid BG meter value is available, then that value will be preferred. 
     A meal detection algorithm is also utilized in the exemplary embodiment of the insulin infusion device. In this regard,  FIG.  9    is a diagram that illustrates a scenario where an automatic correction bolus can be delivered. The vertical axis indicates BG measurements, and the horizontal axis represents time.  FIG.  9    includes a plot  902  of BG values, and an indication of the lowered correction target of 120 mg/dL. For this particular implementation, the BG values are actual (measured) values, although predicted values could also be used in certain applications.  FIG.  9    also depicts a zone  904  that identifies low BG thresholds that are used for comparison against predicted BG values in the manner described in more detail below. The BG limits for this particular example are 80 mg/dL and 50 mg/dL. In practice, different default and reduced BG limits (which may be fixed or dynamically adjustable) may be employed as desired for the given implementation. 
     The meal detection algorithm calculates the rate of change (slope) defined by previous sensor glucose readings (e.g., the last three to seven readings) to detect a post-prandial rise based on the direction, magnitude, and duration of the slopes. The four circled points of the plot  902  depict an instance of such a rise in measured BG values. If a meal is detected in this manner by the algorithm, then the low prediction threshold used in the safe correction bolus algorithm will be temporarily lowered from 80 mg/dL to 50 mg/dL. The timing of this reduction is depicted in  FIG.  9   , where the plot  906  indicates the value of the low prediction threshold (also referred to herein as the low BG threshold level) over time. As the plot  906  indicates, the low prediction threshold remains at its default value of 80 mg/dL unless the measured BG values exhibit a rising trend that is typically associated with consumption of a meal. If a meal is detected, the low prediction threshold is adjusted downward to 50 mg/dL. As a result of this low glucose threshold reduction, the safe correction bolus algorithm deducts less from a calculated correction bolus (if there is a detected pattern of sustained rising rate of change of sensed glucose values at the time of the correction bolus). That said, the final correction bolus amount will not exceed the initially calculated value (as computed by Equation 1). 
     For this particular embodiment, the automatic correction bolus algorithm computes a possible correction bolus amount with each new BG measurement that is obtained, and delivers the calculated correction bolus if the following conditions are met: (1) the automatic basal insulin delivery is currently at the maximum allowable rate of Umax; (2) the intended correction bolus amount is greater than 10% of the Umax level; and (3) the automatic delivery mode is neither operating in the Safe Basal mode nor the Temporary Glucose Target mode. 
     In general, automatic correction boluses will be relatively small and will occur during periods of positive rates of glucose change when BG values are rising above 120 mg/dL. For example, assume that the previous BG value was 120 mg/dL, the user&#39;s BG is rising rapidly at a rate of 2.0 mg/dL/min, the automatic basal delivery is at Umax, and there is no insulin on board from a prior bolus. If a new BG value of 130 mg/dL is received (for example, sensor glucose values are received every five minutes in the exemplary system described here), an automatic correction bolus would be delivered based on the 10 mg/dL difference between the current BG value of 130 mg/dL and the correction target value of 120 mg/dL. Note that for this example, the first automatic correction bolus must exceed Umax by at least 10% for it to be delivered. Accordingly, it is not obvious at what level of glucose the first correction bolus will be implemented. 
     Continuing this example, if glucose continues to rise at the same rate and the next BG value of 140 mg/dL is received five minutes later, then another correction bolus would be calculated based on the 20 mg/dL difference between the current BG value and the correction target, and the infusion device would deduct the active insulin from the prior correction bolus. Therefore, the new correction bolus would effectively only account for the 10 mg/dL difference between the current BG value and the previous BG value instead of the 20 mg/dL difference between the current BG value and the correction target. If the user&#39;s BG then stabilized at 140 mg/dL and a new BG value is received, then the insulin on board deduction from the previous two corrections would counter the correction calculation based on the 20 mg/dL difference between the BG and the correction target, so no additional correction would be given. 
     The benefits of automating the correction bolus will help to provide more effective therapy while reducing the burden on the user to manage their diabetes. There are multiple safeguards in place to prevent over-delivery of insulin by the automatic correction bolus feature. These safeguards include the following, without limitation: 
     The correction bolus target is fixed at 120 mg/dL, which provides a margin against hypoglycemia. 
     Safety of each correction bolus is checked by predicting BG two hours in the future with the help of a mathematical model. If hypoglycemia is predicted, the safeguard can reduce the size of the correction bolus (up to zero) until no hypoglycemia is predicted. 
     In certain embodiments, automatic correction boluses are suppressed when the total amount of correction bolus commands in a 45-minute moving window exceeds 8% of the total daily dose. Correction boluses resume when the total amount of correction bolus commands within the 45-minute window does not exceed 1% of total daily dose. 
     In certain embodiments, sensor glucose values that may be used for correction boluses are limited to 250 mg/dL when a new sensor is less than 12 hours old and the calibration factor is greater than 8 mg/dL/nA. 
     In certain embodiments, automatic correction boluses are suppressed when a sensor glucose spike is detected that is greater than 65 mg/dL/5 minutes (if a sensor glucose measurement is available) or 125 mg/dL/5 minutes (based on the current ISIG and calibration factor when a sensor glucose measurement is not available), and the associated ISIG spike is greater than 15 nA/5 minutes. Correction boluses may resume following a blood glucose entry with successful calibration factor. 
     Automatic correction bolus is delivered after deducting insulin on board. The duration of active insulin on board can be adjusted by the user (minimum two hours, maximum eight hours). 
     The insulin sensitivity factor, ISF, used in the automatic correction bolus calculation is adapted to the user&#39;s physiology based on total daily dose instead of an adjustable user setting. Accordingly, the user may not use the ISF setting to adjust the size of automatic correction boluses. 
     A prolonged high alert occurs if measured sensor glucose stays above 250 mg/dL for three hours. 
     The continuous glucose sensor is calibrated at least once every 12 hours by an independent fingerstick (or other blood sample) BG measurement. 
     All BG meter measurements that are entered into the insulin infusion device (either manually or through a linked meter) and confirmed by the user are used for a sensor integrity check and to calibrate the continuous glucose sensor. 
       FIG.  10    is a flow diagram that illustrates an exemplary embodiment of an insulin infusion device control process  1000 . The process  1000  is suitable for controlling the operation of an infusion device of the type described above with reference to  FIGS.  1 - 8   , namely, an infusion device having a fluid reservoir for insulin to be delivered from the device to the body of a user, and having at least one processor device that executes computer-readable instructions to carry out the process  1000 . The various tasks performed in connection with a process described herein may be performed by software, hardware, firmware, or any combination thereof. For illustrative purposes, a description of a process may refer to elements mentioned above in connection with  FIGS.  1 - 8   . It should be appreciated that a described process may include any number of additional or alternative tasks, the tasks shown in the figures need not be performed in the illustrated order, and an illustrated process may be incorporated into a more comprehensive procedure or process having additional functionality not described in detail herein. Moreover, one or more of the tasks shown for an illustrated process could be omitted from an embodiment of the process as long as the intended overall functionality remains intact. 
     The process  1000  represents one iteration that is performed for a current sampling point or period of time, which corresponds to the most recent sampling period. This example assumes that the insulin infusion device is already being controlled to operate in an automatic basal insulin delivery mode (task  1002 ) that delivers basal insulin to the body of the user. This example also assumes that the process  1000  receives relevant data in accordance with a predetermined schedule (e.g., a sampling period of five minutes). Accordingly, the process  1000  receives, obtains, or accesses information that may have an influence on the manner in which the infusion device delivers insulin to the user. For example, the process  1000  obtains a current or most recent BG measurement that indicates a current BG level of the user (task  1004 ). As mentioned above, the BG measurement can be obtained from a BG meter (typically a fingerstick measurement) or a continuous glucose sensor that is coupled to the body of the user. 
     For this particular embodiment, the correction bolus procedure is initiated when two conditions are satisfied: (1) the current BG measurement exceeds a correction bolus threshold value; and (2) a maximum allowable basal insulin infusion rate (Umax) has been reached during operation in the automatic basal insulin delivery mode. To this end, the process  1000  checks whether the obtained BG measurement is greater than the correction bolus threshold value, LIMIT 1 , (query task  1006 ) and whether the current basal insulin infusion rate equals Umax (query task  1008 ). For this non-limiting example, the correction bolus threshold value (LIMIT 1 ) is 120 mg/dL and Umax will typically fall within the range of about 0.5 to about 3.0 Units/hour (the actual value checked at query task  1008  is patient-specific). If either of these conditions are not met, then the process  1000  exits without considering an automatic correction bolus. If both of these conditions are satisfied, however, then the process  1000  continues by initiating and performing the correction bolus procedure to calculate an automatic correction bolus amount (task  1010 ). The manner in which the automatic correction bolus (ACB) amount is calculated will be described in more detail below with reference to  FIG.  11   . In certain implementations, an initial or proposed ACB amount is calculated and scaled or adjusted as needed to arrive at a final ACB amount. 
     The illustrated embodiment of the process  1000  performs an additional check before delivering a correction bolus. More specifically, the process  1000  checks whether the computed final ACB amount exceeds a bolus delivery threshold amount, LIMIT 2  (query task  1012 ). If the final ACB amount does not exceed the bolus delivery threshold amount (the “No” branch of query task  1012 ), then the insulin infusion device is controlled such that the calculated final ACB amount is not delivered to the user (task  1014 ). If the final ACB amount exceeds the bolus delivery threshold amount (the “Yes” branch of query task  1012 ), then the insulin infusion device is controlled to deliver the calculated final ACB amount to the user (task  1016 ). In other words, the final ACB amount is delivered only when it exceeds the bolus delivery threshold amount, which may be defined as a percentage of Umax, e.g., ten percent of the current value of Umax. The bolus delivery threshold amount is utilized in the exemplary embodiment to avoid delivery of small insulin boluses, which may have little effect and/or be unnecessary. Whether or not the final ACB amount is delivered, the process  1000  continues by delivering basal insulin at the rate of Umax for at least the next cycle or sampling period (task  1018 ). As depicted in  FIG.  10   , the process  1000  leads back to task  1002  to repeat itself for the next iteration. 
       FIG.  11    is a flow diagram that illustrates an exemplary embodiment of an ACB calculation process  1050 , which can be performed during task  1010  of the process  1000  (see  FIG.  10   ). The process  1050  is one suitable methodology for calculating the final ACB amount to be considered for delivery to the user. Alternative embodiments, however, may utilize different methodologies or approaches to determine a recommended ACB amount. 
     The exemplary embodiment of the process  1050  calculates an initial correction bolus amount for the user (task  1052 ). In this regard, the initial correction bolus can be calculated in accordance with Equation 1. The exemplary embodiment described here includes an optional feature that automatically detects a BG trend that is indicative of meal consumption and, in response to such detection, adjusts the methodology by which the final ACB amount is calculated. In this regard,  FIG.  11    includes a query task  1054  that checks whether the user&#39;s BG measurements are indicative of meal consumption. In practice, the process  1050  analyzes the current BG measurement and at least one historical BG measurement to check whether those measurements reflect a BG trend that is indicative of meal consumption by the user. As explained above, if the BG measurements under analysis exhibit a sharp rise over time, a slope that exceeds a threshold value, or the like, then the process  1050  will indicate that a meal has been detected for purposes of query task  1054  (the “Yes” branch); if not, then the process  1050  continues via the “No” branch of query task  1054 . 
     If query task  1054  detects conditions indicative of meal consumption, then the process  1050  continues by reducing a default value of a low BG threshold level to obtain a reduced value (task  1058 ). The resulting low BG threshold value, which is labeled LIMIT 3  in  FIG.  11   , is utilized as a comparison value in the manner described in more detail below with reference to query task  1062 . If query task  1054  determines that the user&#39;s BG trend does not reflect the recent consumption of a meal (the “No” branch of query task  1056 ), then the process  1050  continues with the default, unadjusted, value of the low BG threshold level (task  1056 ). Accordingly, the default low BG threshold level is utilized to calculate the final ACB amount unless the process  1050  detects conditions that indicate meal consumption—if so, the default low BG threshold level is lowered. As mentioned above, for the exemplary embodiment described here, the default low BG threshold value is 80 mg/dL and the reduced low BG threshold value is 50 mg/dL. It should be appreciated that these thresholds may vary from one embodiment to another, and that the thresholds may be fixed values, automatically adjustable values, or manually adjustable values if so desired. 
     After settling on the value to be used for the low BG threshold level (LIMIT 3 ), the process  1050  continues by computing a predicted future BG level (PBG) of the user, which results from simulated delivery of the calculated correction bolus amount (task  1060 ). In accordance with the exemplary embodiment presented here, the process  1050  calculates a set of predicted or forecasted glucose measurement values for the patient corresponding to a time period into the future and simulates delivery of the initial correction bolus amount (obtained at task  1052 ). The resulting PBG can be calculated as a function of the current BG measurement value, the current BG measurement derivative or trend, historical insulin delivery, the amount of carbohydrates associated with a detected or announced meal, and the amount of insulin for the correction bolus to be administered. Additionally, the PBG may account for estimated future insulin deliveries that may be automatically or autonomously delivered by the control scheme implemented by the insulin infusion device. 
     In exemplary embodiments, future glucose values are predicted using a mathematical model of the patient that characterizes the glucose response to insulin delivery by a set of differential equations. Meal information could also be incorporated into the predictions, but the described methodology is more conservative if the influence of carbohydrates on blood glucose is ignored. These equations may be based on a mass balance between estimated glucose utilization as result of insulin delivery. The mathematical model may also include specific parameters that enable it to predict the blood glucose at fasting. 
     The process  1050  uses the PBG for purposes of scaling the initial correction bolus amount (if needed) to obtain a final correction bolus amount for the user. The goal of the scaling is to reduce the initial correction bolus amount such that the PBG resulting from simulated delivery of the final correction bolus amount exceeds the low BG threshold level. The embodiment described here reduces the initial correction bolus amount in a stepwise (iterative) manner to obtain the final correction bolus amount. Thus, the final correction bolus amount can be equal to or less than the initial correction bolus amount. 
       FIG.  11    depicts an exemplary embodiment that iteratively reduces the initial correction bolus amount in a stepwise manner such that the scaling maximizes the final correction bolus amount without causing the PBG to fall below the low BG threshold level. In this regard, a query task  1062  of the process  1050  compares the PBG against the low BG threshold level (which may be its default value or the reduced value, as explained above). If the PBG is not lower than the low BG threshold level (the “No” branch of query task  1062 ), then the calculated correction bolus amount is used as the final ACB for delivery (task  1064 ). For the first iteration of the methodology, the calculated correction bolus amount is equal to the initial correction bolus amount calculated at task  1052 . For subsequent iterations of the methodology, the calculated correction bolus amount will be less than the initial amount. 
     If the PBG is lower than the low BG threshold value (the “Yes” branch of query task  1062 ), then the process  1050  checks whether the calculated correction bolus amount has reached a minimum value (query task  1066 ). The minimum value may be any defined amount of insulin, a percentage of the initially calculated correction bolus amount, or the like. For example, the minimum bolus value considered at query task  1066  may be zero Units of insulin. If the calculated correction bolus amount for the current iteration of the methodology has reached the minimum value (the “Yes” branch of query task  1066 ), then the process  1050  exits without delivering a correction bolus to the user (task  1068 ), or sets the final ACB amount to be equal to the minimum value, e.g., zero Units. 
     If the calculated correction bolus amount for the current iteration of the methodology has not reached the minimum value (the “No” branch of query task  1066 ), then the correction bolus amount is reduced or scaled down, preferably in a stepwise manner (task  1070 ). The type and amount of scaling/reduction may vary from one implementation to another, and different techniques can be used. The embodiment described here employs a simple scaling factor (multiplier) to progressively reduce the initial correction bolus amount as needed. More specifically, the first comparison at query task  1062  considers the unscaled initial correction bolus amount (i.e., 100% of the initial correction bolus amount), the second iteration of query task  1062  considers 75% of the initial correction bolus amount, the third iteration of query task  1062  considers 50% of the initial correction bolus amount, the fourth iteration of query task  1062  considers 25% of the initial correction bolus amount, and the fifth iteration of query task  1062  considers 0% of the initial correction bolus amount (i.e., no correction bolus). Ultimately, the scaling step multiplies the initial correction bolus amount by a scaling factor between 0.0 and 1.0, inclusive, to obtain the final correction bolus amount. 
     In other embodiments, a golden ratio-based search or a Fibonacci search is utilized to progressively or iteratively reduce the search space defined by the initial correction bolus amount using intermediate values within the search space that progressively converge toward an adjusted bolus amount that is selected to be administered in lieu of the initial correction bolus amount. In this regard, in exemplary embodiments, the search attempts to maximize the final correction bolus dosage within the search space defined by the initial correction bolus amount while maintaining a predicted future glucose level for the patient that satisfies a postprandial hypoglycemic threshold during a predefined postprandial analysis time period. The bolus search process identifies or otherwise determines an initial adjusted bolus amount to be used to probe or test for use in lieu of the initial correction bolus amount that was originally determined (e.g., at task  1052 ). In this regard, the bolus search process identifies the initial adjusted bolus amount within a search space defined by a bolus of zero as a lower limit and an upper limit equal to the initial correction bolus amount (b corr ). 
     In exemplary embodiments, the golden ratio is utilized to identify the initial adjusted bolus amount as a fraction of the initial correction bolus amount corresponding to the golden ratio by multiplying the initial correction bolus amount by 0.618. That said, the subject matter described herein is not intended to be limited to any particular manner for dividing the search space. The bolus search process also utilizes the initial adjusted bolus amount to define or otherwise determine search spaces for subsequent analysis. For example, an upper search space may be defined relative to the initial adjusted bolus amount as being bounded by the initial adjusted bolus amount as its lower limit and the initial correction bolus amount as its upper limit (e.g., [0.618b corr , b corr ]), while a lower search space may be bounded by the initial adjusted bolus amount as its upper limit and a bolus dosage of zero as its lower limit (e.g., [0,0.618b corr ]). This methodology can be used during each iteration of the described methodology to progressively adjust the correction bolus amount and arrive at the final ACB amount. 
     After reducing the calculated correction bolus amount (at task  1070 ), the process  1050  returns to task  1060  to compute another PBG, based on simulated delivery of the reduced correction bolus amount. Thereafter, the process  1050  continues in the manner described above. The stepwise scaling of the initial correction bolus amount results in a “maximized” correction bolus that should not result in a BG level that goes below the applicable low BG threshold level for the user. Assuming that a nonzero final correction bolus amount is eventually obtained at task  1064 , the ACB calculation process  1050  exits and leads to task  1012  of the insulin infusion device control process  1000  (see  FIG.  10    and the relevant description of tasks  1010  and  1012 ). 
     For the sake of brevity, conventional techniques related to glucose sensing and/or monitoring, bolusing, closed-loop glucose control, and other functional aspects of the subject matter may not be described in detail herein. In addition, certain terminology may also be used in the herein for the purpose of reference only, and thus is not intended to be limiting. For example, terms such as “first”, “second”, and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. The foregoing description may also refer to elements or nodes or features being “connected” or “coupled” together. As used herein, unless expressly stated otherwise, “coupled” means that one element/node/feature is directly or indirectly joined to (or directly or indirectly communicates with) another element/node/feature, and not necessarily mechanically. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or embodiments described herein are not intended to limit the scope, applicability, or configuration of the claimed subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope defined by the claims, which includes known equivalents and foreseeable equivalents at the time of filing this patent application.