Patent Publication Number: US-2022226566-A1

Title: Basal rate testing using frequent blood glucose input

Description:
RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 15/266,468 filed Sep. 15, 2016, which is a continuation of U.S. application Ser. No. 11/685,617 filed Mar. 13, 2007, which are hereby fully incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The field generally relates to patient insulin management devices and, in particular, but not by way of limitation, to systems, devices and methods for adjusting insulin therapy. 
     BACKGROUND 
     People who suffer from diabetes require insulin to keep their blood glucose level as close as possible to normal levels. It is essential for people with diabetes to manage their blood glucose level to within a normal range. Complications from diabetes can include heart disease (cardiovascular disease), blindness (retinopathy), nerve damage (neuropathy), and kidney damage (nephropathy). Insulin is a hormone that reduces the level of blood glucose in the body. Normally, insulin is produced by beta cells in the pancreas. In non-diabetic people, the beta cells release insulin to satisfy two types of insulin needs. The first type is a low-level of background insulin that is released throughout the day. The second type is a quick release of a higher-level of insulin in response to eating. Insulin therapy replaces or supplements insulin produced by the pancreas. 
     Conventional insulin therapy typically involves one or two injections a day. The low number of injections has the disadvantage of allowing larger variations in a person&#39;s insulin levels. Some people with diabetes manage their blood glucose level with multiple daily injections (MDI). MDI may involve more than three injections a day and four or more blood glucose tests a day. MDI offers better control than conventional therapy. However, insulin injections are inconvenient and require a diabetic person to track the insulin doses, the amount of carbohydrates eaten, and their blood glucose levels among other information critical to control. 
     Blood glucose (BG) management devices help a diabetic person manage their blood glucose. For example, an insulin pump is a BG management device that provides insulin throughout the day. A glucose monitor (GM) or meter is a BG management device that measures blood glucose levels. Some GMs require a finger-stick to acquire a sample of blood that is applied to a test strip to get a blood glucose reading. Some GMs are able to provide continuous monitoring of blood glucose. Other BG management devices include computers running software to help a diabetic person manage insulin therapy. However, most BG management devices are limited in the control over blood glucose that they offer. 
     SUMMARY 
     This document discusses, among other things, devices and methods for managing insulin therapy. A device example includes a user interface configured to generate an electrical signal to start a basal insulin rate test when prompted by a user, an input configured to receive sampled blood glucose data of a patient that is obtained during a specified time duration, including a time duration during delivery of insulin according to a specified basal insulin rate pattern, and a controller communicatively coupled to the input and the user interface. The controller includes an insulin calculation module configured for determining at least one of an amount of basal insulin over-delivered and an amount of basal insulin under-delivered during the basal insulin rate test in trying to meet a target blood glucose baseline. 
     A method example includes receiving a user prompt in a blood glucose (BG) management device to start a basal insulin rate test, receiving sampled blood glucose data that is obtained during a specified duration of time when insulin is delivered according to a specified basal insulin rate pattern, and determining at least one of an amount of basal insulin over-delivered and an amount of basal insulin under-delivered in trying to meet a target blood glucose baseline during the basal insulin rate test using the BG management device. 
     This summary is intended to provide an overview of the subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. The detailed description is included to provide further information about the subject matter of the present patent application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of portions of a BG management device. 
         FIG. 2  shows example illustrations of a blood glucose concentration graph and a basal rate pattern. 
         FIG. 3  is a block diagram of portions of an example of a BG management device that includes a pump mechanism. 
         FIG. 4  is an illustration of a BG management device that includes an insulin pump. 
         FIG. 5  is another block diagram of portions of a BG management device that includes a pump mechanism. 
         FIG. 6  is a block diagram of a BG management device that includes a blood glucose sensor circuit. 
         FIG. 7  is a block diagram of portions of another example of a BG management device. 
         FIG. 8  is a flow diagram of a method of using a BG management device to execute a basal rate test. 
         FIG. 9  is a flow diagram of another method of using a BG management device to execute a basal rate test. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and specific embodiments in which the invention may be practiced are shown by way of illustration. It is to be understood that other embodiments may be used and structural or logical changes may be made without departing from the scope of the present invention. 
     It is important for a diabetic person to be treated with the proper amount of insulin. As discussed previously, high blood sugar can lead to serious complications. Conversely, a person with low blood sugar can develop hypoglycemia. Ideally, insulin therapy mimics the way the body works. An insulin pump is one way to mimic the body&#39;s insulin production. An insulin pump can provide a background or basal infusion of insulin throughout the day and provide a quick release or bolus of insulin when carbohydrates are eaten. If a person develops high blood sugar, a correction bolus can be delivered by the pump to correct it. While insulin pumps improve convenience and flexibility for a diabetic person, they can be sophisticated devices. Some insulin pumps can be difficult to program. Proper use of an insulin pump requires a user to go through a learning curve to properly use and program the pump. 
     Basal rate refers to a type of twenty-four hour background infusion of insulin by an insulin pump that mimics the continuous background release of insulin from a normal pancreas. It is the rate of insulin delivery the patient normally needs independent of the consumption of meals. The basal rate is typically specified in insulin units per hour (u/hr). Typically, a basal rate for a pump is initially programmed by a clinician based on a total daily dose (TDD) of insulin for a diabetic person. The clinician may determine TDD based on many factors including the type of diabetes of the patient and the patient&#39;s weight, age, and level of fitness. The amount of basal insulin is typically determined to be a percentage of TDD, such as 40%, 50%, or 60% for example. The total daily dose is then divided by 24 to obtain an average basal rate. For example, if a patient&#39;s TDD is determined to be 40 units of insulin, and 50% of the TDD is used for basal delivery, the average basal rate is 20 units/24 hours or 0.83 u/hr. 
     Many insulin pump users may use three or more different basal rates during the course of a day. Basal rates can be adjusted to change delivery every few minutes (e.g., 20-30 minutes) by increments as small as 0.05 u/hr to better track changes in demand, such as from an increase typically needed before dawn or a decrease needed during long active periods. Insulin pump users may use different basal rates for overnight, for breakfast to mid-afternoon, and for mid-afternoon to bedtime. Appropriate basal rates vary from person to person, may be different for a person at various times of the day, and may change for a person over time. Inappropriate basal rate settings may result in low blood glucose levels overnight or high blood glucose levels in the morning. An insulin pump user may go through several iterations of trial and error before finding appropriate basal rates. Because a patient&#39;s basal insulin needs may change over time, such as with weight change or with a change in fitness level, basal rate testing may be performed periodically to ensure that an appropriate basal rate is being delivered by an insulin pump. Blood glucose (BG) management devices are more valuable to a diabetic person if the device conveniently assists them in determining their appropriate basal rate or rates. 
     Apparatus Embodiments 
       FIG. 1  is a block diagram of portions of a BG management device  100 . Examples of a BG management device  100  include, among other devices, an insulin pump, a blood glucose monitor (GM) or meter, and a computing device running software to assist a diabetic patient in managing insulin therapy. Examples of a computing device include, among other things, a personal computer or a personal data assistant (PDA). 
     The BG management device  100  includes a user interface  105 , an input  110 , and a controller  115  communicatively coupled to the input  110  and the user interface  105 . The controller  115  can be implemented using hardware circuits, firmware, software or any combination of hardware, firmware and software. Examples, include a microcontroller, a logical state machine, and a processor such as a microprocessor, application specific integrated circuit (ASIC), or other type of processor. 
     The user interface  105  generates an electrical signal to begin a basal rate test when prompted by a user. The user interface  105  may include a pushbutton, keypad, or a computer mouse. The user interface  105  may include a display operatively coupled to the controller  115  to provide patient or user instructions for the basal rate test. Examples of instructions include, among other things, instructing the patient not to eat during the test, to maintain a normal activity level, and not to administer an insulin correction bolus during the test. The display may include a touch-screen. The user of the device may be a clinician, caregiver, or a diabetic patient. The user prompts the BG management device  100  using the user interface  105  to begin a basal rate test. The basal rate test assists the user in determining one or more appropriate basal rates. 
     As part of a basal rate test, the patient receives insulin according to a specified basal rate pattern or profile. If the BG management device  100  includes an insulin pump, the basal insulin may be delivered using the BG management device  100 . If the BG management device  100  does not include an insulin pump, the basal insulin may be delivered using a separate device that includes an insulin pump. 
     If the BG management device  100  includes an insulin pump, the BG management device  100  may further include a memory  116  to store at least one basal rate pattern. The controller  115  may display instructions for the user to enter one or more basal rates to be delivered according to time of day. For example, the BG management device  100  may allow the user to enter basal rate values in 0.05 u/hr increments, and to enter time in increments of one-half hour throughout the day. In some embodiments, the BG management device  100  stores different basal rate patterns according to different segments of the day, such as early in the day, late in the day, and overnight for example. In some embodiments, the input  110  may include a communication port and a basal rate pattern may be loaded from a second device into memory  116 . 
     The input  110  is configured to receive sampled blood glucose data of the patient as part of the basal rate test. The blood glucose data provides an indication of the concentration level of the patient&#39;s blood sugar and the data may be obtained from blood directly or from insterstitial fluid. The blood glucose data is obtained during a specified time duration. The specified time duration includes a time when insulin is delivered according to a specified basal rate pattern, but may include a time prior or after the delivery of insulin as well. The configuration of the input  110  may depend on the type of BG management device  100 . If the BG management device  100  is an insulin pump, the input  110  may be coupled to a GM included in the pump or the input  110  may include a communication port to receive the blood glucose data from a second device. The second device may include a GM or the second device may receive the blood glucose data from a third device. In some embodiments, the input  110  is coupled to the user interface  105 , and the user may manually input the data into the pump through a keypad or keyboard included in the user interface. 
     The controller  115  includes an insulin calculation module  120 . Modules can be software, hardware, firmware or any combination of software, hardware, and firmware. Multiple functions can be performed in one or more modules. The insulin calculation module  120  determines at least one of an amount of basal insulin over-delivered and an amount of basal insulin under-delivered during the basal insulin rate test in trying to meet a target blood glucose baseline. 
       FIG. 2  shows example illustrations (not real data) of a blood glucose concentration graph  205  and a basal rate pattern  220  or profile during a basal rate test. Assume, as shown in the blood glucose concentration graph  205 , that the patient&#39;s target blood glucose baseline  215  is 150 mg/dl (milligrams per deciliter) and that this is the patient&#39;s blood glucose concentration level before the basal rate test. Basal insulin is being delivered according to a basal rate pattern  220 . At time t 0 , the user elects to begin a basal rate test. User instructions for the basal rate test may be provided. The blood glucose concentration is determined from blood glucose data received into the input  110  during the basal rate test. The basal rate test may run over several hours, e.g., six to eight hours. In some embodiments, the blood glucose data may be stored in memory for processing. In some embodiments, the blood glucose data may be processed by the insulin calculation module  120  as it is received. 
     If the patient&#39;s blood glucose level remains at the target blood glucose baseline  215  or within a specified range of the target blood glucose baseline  215 , the basal profile is appropriate. If the patient&#39;s blood glucose level rises above the target blood glucose baseline  215  or rises above a specified range of the target blood glucose baseline  215 , the basal rate is too low and there was an under-delivery of basal insulin. If the patient&#39;s blood glucose level falls below the target blood glucose baseline  215  or falls below a specified range of the target blood glucose baseline  215 , the basal rate is too high and there was an over-delivery of basal insulin. 
     In the example in  FIG. 2 , the patient&#39;s blood glucose begins to rise at time t 3 . The change in the blood glucose from the baseline reaches 190 mg/dl, or an increase of 40 mg/dl. At time t 4 , the basal rate pattern  220  includes an increase in basal rate. The blood glucose level of the patient begins to change direction, here a decrease, at time t 5 . The time duration from the increase at t 3  to the change in direction at is t 5  about two hours in this example. The blood glucose level of the patient eventually falls to 110 mg/dl, or a total decrease of 80 mg/dl. At time t 7 , the blood glucose level of the patient begins to again change direction. This time the change in direction is an increase in blood glucose concentration. The time duration from the decrease at t 5  to the change in direction at t 7  is about six hours. 
     In some embodiments, the insulin calculation module  120  is configured to determine the over-delivered amount or the under-delivered amount of basal insulin using a correction factor of the patient and a variance of a blood glucose level from the target blood glucose baseline  215 . A correction factor refers to the amount of drop in blood glucose concentration of the patient for one unit of insulin. In  FIG. 2 , the 40 mg/dl increase corresponds to an under-delivery of basal insulin. The under-delivery may be due to the basal rate being too low or due to an increased demand from the patient during that time of day. The 80 mg/dl decrease corresponds to an over-delivery of basal insulin. 
     To calculate the amount under-delivered, the insulin calculation module  120  divides the increase in blood glucose level (+40 mg/dl) by the correction factor of the patient to determine the amount of insulin required to lower the blood glucose level to the target blood glucose baseline  215 . This is the amount of insulin that was under-delivered to the patient during the basal rate test. Assume in the example of  FIG. 2  that the patient&#39;s correction factor is one unit per 40 mg/dl. In this case, a correction bolus of one unit of insulin would decrease the patient&#39;s blood glucose level to the blood glucose baseline. To calculate the amount of insulin over-delivered, the insulin calculation module  120  divides the decrease in blood glucose level (−80 mg/dl) by the correction factor of the patient (1 u per 40 mg/dl). This corresponds to a correction bolus of −2 units of insulin, i.e., the amount of insulin delivered needs to be reduced by 2 units of insulin. 
     The under-delivered or over-delivered amount can be used to recommend changes to the basal rate pattern. In the example of  FIG. 2 , the insulin calculation module  120  may determine that the existing basal rate pattern  220  needs to be increased at some point by one unit of insulin to address the 40 mg/dl increase and decreased at some point by 2 units of insulin to address the 80 mg/dl decrease. 
     The BG management device  100  is more valuable if recommended changes anticipate an under-delivery or over-delivery. However, anticipating when to change the basal rate is complicated by a delay, or a lag time, in insulin uptake before the insulin becomes effective. Another complication is that the lag time may be different for glucose levels measured using blood and glucose levels measured using interstitial fluid. Measuring blood glucose concentration using the interstitial fluid may make the uptake appear to have additional lag time. In some embodiments, the insulin calculation module  120  recommends a change in a basal rate that precedes any actual times of under-delivery or over-delivery by a time duration that compensates for a lag time associated with the subcutaneous insulin delivery and with the glucose measurement method. 
     In some embodiments, in addition to the uptake lag time, the insulin calculation module  120  uses the time from a beginning of a change in the blood glucose level to a change in direction of the blood glucose data values to determine a recommended change to the basal insulin rate pattern  220 . In the example of  FIG. 2 , it is determined that one unit of insulin is needed to correct the under-delivery of insulin resulting in the 40 mg/dl increase in blood glucose level. The increase began at t 3  and a change in direction occurred two hours later at t 5 . The insulin calculation module  120  may recommend a change that includes adding one unit of insulin to the basal rate pattern  220  and spreading the delivery out over two hours corresponding to the change in direction time, i.e., a rate of 0.5 u/hr. This shown by the basal rate increase  225  of 0.5 u/hr for two hours over time t 1  to t 2 . The time t 1  is shifted earlier than the time of the increase at t 3  by a time duration to compensate for a delay in the insulin uptake so that the insulin may act on the blood glucose. 
     Also in  FIG. 2 , an over-delivery of 2 units of insulin resulted in an 80 mg/dl increase in blood glucose level. The decrease began at t 5  and a change in direction occurred six hours later at t 7 . The insulin calculation module  120  may recommend a change that includes subtracting two units of insulin from the basal rate pattern  220  over six hours at a rate of 0.33 u/hr. This shown by the basal rate decrease  230  of 0.33 u/hr for six hours over time t 2  to t 6 . The time t 2  is early enough to compensate for the delay in insulin uptake. 
     The lag time for insulin uptake may depend on several factors. In some embodiments, the insulin calculation module  120  determines a time duration to compensate for such a time lag using the type of insulin delivered. Some insulin types have a faster uptake than other types, and the insulin calculation module  120  may use a table stored in a memory of the BG management device to correlate a time duration to an insulin type. In some embodiments, the insulin calculation module  120  calculates the compensating time duration using an activity level of the patient and/or the fitness level of the patient. In some embodiments, the compensating time lag is pre-determined from clinical studies and is stored in a memory for use by the insulin calculation module  120 . 
     In some embodiments, the insulin calculation module  120  may adjust the correction factor before determining an amount of insulin under or over-delivered. In certain embodiments, the insulin calculation module  120  may use a correction factor multiplier to adjust the correction factor when determining the amount of insulin under or over-delivered, and consequently adjusting the amount of insulin in any recommended changes to the basal rate pattern  220 . For example, assume as in  FIG. 2  that the patient&#39;s correction factor is one unit per 40 mg/dl. If the correction factor multiplier is 1.3, the insulin calculation module uses a correction factor of one unit per 52 mg/dl [(1.3)(40 mg/dl/unit)]. For the 40 mg/dl increase in  FIG. 2 , the insulin calculation module  120  divides the increase in blood glucose level (40 mg/dl) by the correction factor of the patient (1 u per 52 mg/dl). This corresponds to a correction bolus of 0.77 units [(40)/(52)] of insulin. The insulin calculation module  120  may recommend adding 0.39 u/hr for two hours to the basal rate pattern. 
     Using a correction factor multiplier results in a lower amount of basal insulin allowing adjustments to be made more safely made. This may give a user more confidence in using the recommended changes to the basal rate pattern  220 . The 80 mg/dl decrease corresponds to a correction bolus of 1.54 units of insulin. The insulin calculation module  120  may recommend subtracting 0.26 u/hr for six hours to the basal rate pattern. The controller  115  may store the correction factor multiplier in a memory. The correction factor multiplier may be manually set or programmed by a clinician. The clinician may set the correction factor multiplier to a value that accords to a level of confidence or comfort to the clinician in the recommended changes to the basal rate pattern  220 . 
     In some embodiments, if the blood glucose data received during the basal rate test indicates that the blood glucose level of the patient is outside of a specified range of blood glucose levels, the controller  115  cancels the basal insulin rate test. If the blood glucose level is above the range, the controller  115  may recommend a correction bolus to be taken by the patient. The insulin calculation module  120  calculates the amount of insulin in the correction bolus by dividing the blood glucose concentration by the specified correction factor for the patient. 
     If the blood glucose level is below the range, the controller  115  may recommend an amount of carbohydrates to be eaten by the patient. The insulin calculation module  120  calculates the amount of carbohydrates using a correction factor specified for the patient and a carbohydrate ratio specified for the patient. A carbohydrate ratio refers to the amount of carbohydrates reduced, or covered, by a unit of insulin. 
     For example, assume that at the beginning of a basal rate test, the blood glucose level of a patient is 40 mg/dl below the specified range and the specified correction factor is 1 unit per 80 mg/dl. The insulin calculation module  120  determines that −0.5 units of insulin (−40/80) are required to bring the blood glucose level back within the specified range. Negative insulin cannot be delivered so this corresponds to a requirement for carbohydrates. Assume that the carbohydrate ratio of the patient is 20 grams of carbohydrates per unit of insulin (20 g/u). The insulin calculation module  120  multiplies the amount of insulin by the carbohydrate ratio to determine that the patient should eat 10 grams of carbohydrates [(0.5)(20)]. The insulin calculation module  120  may take into account additional factors such as the health status of the patient and the activity level of the patient in recommending the carbohydrate amount. In some embodiments, if the blood glucose of the patient is outside the specified range of blood glucose levels, the controller  115  suspends the start of the basal insulin rate test until the blood glucose of the patient is within the specified range of blood glucose levels. 
     As discussed previously, appropriate basal rates may differ for a patient throughout the course of a day. The BG management device  100  may include a timer circuit  117  operatively coupled to the controller  115 . The controller  115  displays user instructions to execute a basal rate test at one or more specified times during a day. In some embodiments, controller  115  displays user instructions to run the basal insulin rate test on multiple days. The controller  115  may prompt the user to run the test during substantially the same time on the multiple days. This may result in more appropriate basal delivery rates being used at different times during the day. 
     It is often difficult to maintain a stable blood glucose target value overnight because the correction factor varies as a function of time. In order to stabilize the glucose value at a target blood glucose value, the basal rate may often be adjusted during overnight periods to compensate for changes in the correction factor. An insulin pump user may go through several iterations of trial and error while attempting to find appropriate overnight basal rates. A trial and error method may result in less than optimal control of overnight blood glucose level. 
     According to some embodiments, the BG management device  100  automatically executes a basal rate test during a period when food intake is restricted, such as overnight for example. The basal rate test may start a specified time after a user prompts the BG management device  100  to execute the basal rate test. For example, if the period is overnight, the user prompt may start a timer circuit and the controller  115  may initiate the overnight basal rate test when a time duration expires. The insulin calculation module  120  automatically determines one or more basal rates for a basal rate profile using a basal rate calibration and verification technique. The basal blood glucose value g can be approximated by 
         g ( t )≅ c ( t ) b ( t −τ),  (1)
 
     where c(t) is the basal correction factor, b(t) is the basal insulin rate, and τ is the delay or lag time associated with the uptake of a subcutaneous infusion of insulin. Food consumption and exercise are assumed to be negligible during the period of the test. 
     The insulin calculation module  120  may perform a rapid calibration that can be executed during a period as short as two time periods, such as two nights for example. The correction factor c(t) may vary as a function of time. To determine c(t), blood glucose data values g 1 (t) and basal insulin delivery rates b/(t) are recorded periodically throughout a first observation period. Rewriting Equation (1) to solve for c(t) for the first period yields 
     
       
         
           
             
               
                 
                   
                     
                       
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     The delay for insulin uptake τ 1  can be an assumed value based on current estimates from clinical studies that use that type of insulin, or can be determined on a per patient basis using stochastic or deterministic time series analysis of prior or current basal test data. The time series analysis of the blood glucose data values may be performed under pulse function, step function, or continuous changes in insulin delivery. The time-dependent changes in insulin delivery may be present in the user&#39;s current basal profile or the user may be prompted to create a time-dependent change by the insulin calculation module. The stochastic or deterministic time series analysis can be performed on blood glucose data obtained from previous calibration or observation periods, such as previous nights for example. Thus, the delay for insulin uptake may be determined using blood glucose data obtained prior to the basal rate test. 
     A desired target blood glucose value g t (t) may be a constant or a function of time. Equation (1) can be written as 
         g   t ( t )≅ c   1 ( t ) b   t ( t−τ   1 ),  (3)
 
     where c 1 (t) is the correction factor determined from the first period of data values from Equation (2). Solving equation (3) for a controlling basal insulin rate b t (t) that achieves the desired g t (t) yields 
     
       
         
           
             
               
                 
                   
                     
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     It is assumed that the correction factor c(t) is a periodic function that repeats on a twenty four hour cycle, and that c(t) determined from data and basal rates during the first period of reduced food intake will be similar on subsequent periods twenty-four hours later. 
     During the second period of observation, blood glucose data values g 2 (t) and basal rates b 2 (t) are again recorded periodically. Ideally g 2 (t)=g t (t), but in reality g 2 (t)=g t (t)+ε(t), where ε(t) is the residual deviation from the target blood glucose value. Thus, Equation (1) can be written as 
         g   t ( t )+ε( t )= c   1 ( t ) b   1 (τ 1 −δ)),  (5)
 
     Assuming that ε(t) is primarily due to the error in the estimate of τ 7 , Equation (5) can be rewritten as 
         g   t ( t )+ε( t )= c   1 ( t ) b   t1 ( t −(τ 1 −δ)),  (6)
 
     where δ is the error in the delay estimate. Combining Equations 5 and 6 gives 
       ε( t )= c   1 ( t )[ b   t ( t−τ   1 )− b   t ( t −(τ 1 −δ))].  (7)
 
     Curve fitting or other standard minimization techniques can be used to determine the most appropriate estimate of δ to satisfy Equation (7). Once 6 is determined, the control estimate for the basal insulin delivery rate or rates b t (t) that achieves the desired blood glucose target g t (t) can be written as 
     
       
         
           
             
               
                 
                   
                     
                       
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     where τ 2 =τ 1 −δ. The insulin calculation module may then recommend changes to the t basal rate pattern using b t (t). 
     The rapid calibration technique is a method to quickly achieve improved control over blood glucose level. In some embodiments, the insulin calculation module  120  executes a basal rate test that uses a generalized calibration technique to achieve more accurate estimates of b t (t). The generalized calibration method uses least squares estimation techniques with at least two periods of observing blood glucose data and basal insulin delivery rates. Referring back to Equation (1) and with g(t) and b(t) measured over several periods, τ and c(t) can be estimated by curve fitting with a finite order polynomial or an orthogonal series approximation such as a Fourier series approximation for example. The resulting estimate of b t (t) is calculated using Equation 3 with τ and c(t) estimated from the curve fit results. 
     According to some embodiments, the BG management device includes an insulin pump.  FIG. 3  is a block diagram of portions of an example of a BG management device  300  that includes a pump mechanism  330  to deliver insulin to the patient. The pump mechanism  330  is operatively coupled to the controller  115 . The controller  115  may track the amount of insulin delivered via the pump mechanism  330 . The BG management device  300  includes a memory  116  operatively coupled to the controller  115  to store one or more basal rate patterns  325 . The BG management device delivers basal insulin according to the basal rate patterns. The BG management device  300  also may deliver insulin through boluses such as a correction bolus or a carbohydrate bolus. In some embodiments, the BG management device  300  has a timer circuit  117  that includes a real time clock coupled to the controller  115 . The controller  115  is configured to vary a basal rate of insulin delivery by a time of day according to a basal rate pattern. 
     In some embodiments, the insulin calculation module  120  is able to keep track of the amount of active insulin in the patient. This is sometimes referred to as insulin on board (IOB). To track the amount of active insulin, the controller  115  uses the amount of insulin delivered, the time that elapsed since delivery of insulin and a duration of how long the insulin is active in the blood. The duration may be determined using kinetic action, which is the time it takes for insulin to disappear from the blood, or the duration of insulin action (DIA), which is how long the insulin lowers blood glucose. In some embodiments, the controller  115  cancels a basal rate test if the insulin calculation module  120  determines that the active insulin amount is above a specified threshold insulin amount. This minimizes the risk of IOB confounding the results of the basal rate test. 
     In some embodiments, the controller  115  cancels the basal insulin rate test if the controller  115  determines that an insulin bolus dose, such as a correction insulin bolus or a carbohydrate insulin bolus, is delivered during the basal insulin rate test. In some embodiments, if the user enables an insulin bolus delivery, the controller  115  displays a warning that the basal insulin test will be canceled if the user elects to proceed with delivery of the insulin bolus dose. 
       FIG. 4  is an illustration of a BG management device  400  that includes an insulin pump. The BG management device  400  includes a cassette or cartridge of insulin and tubing  440  connectable to a patient such as by a Luer lock  445 . The BG management device  400  includes a user interface that may include a display  402  operatively coupled to a controller  115 . The user interface may also include one or more keys  404 . 
     Returning to  FIG. 3 , the blood glucose data obtained during the basal insulin rate test may be produced by a second device separate from the BG management device  300 . The controller  115  displays user instructions for the basal rate test. The user interface  105  and the input  110  are configured to receive the sampled blood glucose data entered manually by the user through the user interface  105 . The controller  115  may periodically prompt the user to enter a blood glucose value at different times during the test, or to enter the blood glucose data all at once after the test. 
       FIG. 5  is another block diagram of portions of a BG management device  500  that includes a pump mechanism  530  and delivers basal insulin according to one or more basal rate patterns  525  stored in memory  116 . A blood glucose monitor, or GM  550 , is communicatively coupled to the input  110 . The input  110  is configured to receive the sampled blood glucose data from the GM  550 . In some examples, the GM  550  is included in the BG management device  500  and is coupled to the input  110 . In some examples, the GM  550  is included in a second device. The input  110  may receive the blood glucose data during the basal rate test or after the test is run. The input  110  may include a communication port, such as communication port  447  located on the rear face of the device in  FIG. 4 , and the GM  550  is communicatively coupled to the input  110  by the communication port  447 . In some embodiments, the communication port  447  is a wired port such as a serial interface or bus interface for communicating with the second device. In some embodiments, the communication port  447  is a wireless port such as an infrared (IR) communication port or a radio frequency (RF) communication port. The input  110  wirelessly receives the sampled blood glucose data from the second device. 
     Returning to  FIG. 5 , in some embodiments, the GM  550  is a continuous GM and automatically collects the sampled blood glucose data. For example, the GM  550  may include a blood glucose sensor. The blood glucose sensor produces a blood glucose signal representative of a blood glucose level of the patient. The GM  550  samples the blood glucose signal to obtain the sampled blood glucose data. 
     In some embodiments, the GM  550  may need to prompt the user to begin a blood glucose measurement. For example, the GM  550  may require diabetes test strips to take a blood glucose measurement. The controller  115  prompts the user, via a display, to begin a blood glucose measurement using the GM  550 . The user then provides a new test strip to the GM  550  when prompted during the basal rate test. In another example, the GM  550  may include a drum of diabetes test strips and the user advances the drum to a fresh or unused test strip when prompted by the controller  115 . The controller  115  may display a recommended basal rate after the basal rate test. The controller  115  may also communicate a recommended change in the basal rate to the second device via a communication port. 
     According to some embodiments, the BG management device is a GM.  FIG. 6  is a block diagram of a BG management device  600  that includes a blood glucose sensor circuit  635  operatively coupled to the input  110 . The blood glucose sensor circuit  635  produces a blood glucose signal representative of a blood glucose level of the patient and provides the sampled blood glucose data to input  110 . In some embodiments, the blood glucose sensor circuit  635  includes an implantable blood glucose sensor. In some embodiments, the blood glucose sensor includes a percutaneous blood glucose sensor. The blood glucose sensor circuit  635  may include signal conditioning circuits, such as for signal filtering and signal amplification for example. If an implantable blood glucose sensor is used, the blood glucose sensor circuit  635  may include a communication circuit configured to receive blood glucose data wirelessly, such as by RF communication. 
     The BG management device  600  includes a second input  630  communicatively coupled to the controller  115 . The second input  630  receives information related to basal insulin delivery, such as one or more basal rate patterns used during the basal rate test. The information related to insulin delivery may be received into a memory  116 . The insulin calculation module  120  determines at least one of an amount of insulin over-delivered and an amount of insulin under-delivered during the basal rate test using the insulin delivery information and the sampled blood glucose data. The BG management device  600  may include a communication port  647  coupled to the second input  630 . The communication port  647  receives the information related to insulin delivery from a second device. In some embodiments, the communication port  647  is a wired port such a serial interface or bus interface. In some embodiments, the communication port  647  is a wireless port such as an infrared (IR) communication port or a radio frequency (RF) communication port. The second input  630  wirelessly receives the insulin delivery data from the second device. As an example, the second device may be an insulin pump. The insulin calculation module  120  may determine changes to the basal rate pattern used to deliver basal insulin during the basal rate test. The controller  115  communicates recommended changes through the communication port  647  or may display the recommended changes on a display. 
     In some embodiments, the user interface  105  and the second input  630  are configured to receive the information related to insulin delivery by a user manually entering the information through the user interface  105 . The insulin delivery information may be obtained from a pump for example. The controller  115  may display any recommended changes to the basal rate pattern. 
       FIG. 7  is a block diagram of portions of another example of a BG management device  700 . BG management device  700  includes neither a GM nor an insulin pump. The BG management device  700  includes a user interface  105 , an input  110 , and a controller  115  communicatively coupled to the input  110  and the user interface  105 . The input  110  includes at least one communication port  747  configured for receiving sampled blood glucose information. The communication port  747  may provide a wired connection to a second device, or the communication port  747  may provide a wireless connection to a second device. The sampled blood glucose information may include at least one time-stamp in order to align the sampled blood glucose information to information related to insulin delivery. 
     The insulin delivery information may be received through the same communication port  747  or a second communication port. The communication ports may be any combination of wired or wireless communication ports. The insulin delivery information includes information related to basal insulin delivered according to a basal rate pattern, and may include at least one time-stamp to align the insulin delivery information with the blood glucose information. The insulin calculation module  120  determines at least one of an amount of insulin over-delivered and an amount of insulin under-delivered during the basal rate test using the insulin delivery information and the sampled blood glucose data. The insulin calculation module  120  may recommend changes to the basal rate pattern. The controller  115  may communicate recommended changes to the basal rate pattern through the communication port  747  and/or the controller  115  may display the recommended changes. 
     Method Embodiments 
       FIG. 8  is a flow diagram of a method  800  of using a BG management device to execute a basal rate test. At block  805 , a user prompt is received in a BG management device to start a basal insulin rate test. The user interface may include a push-button, keypad, or mouse. The user interface may also include a display to display one or more instructions for the user to execute the basal rate test, and to display to display any recommend changes to a basal rate or a basal rate pattern. In some embodiments, the method  800  includes displaying instructions for the basal insulin rate test using the BG management device. 
     At block  810 , sampled blood glucose data is received in the BG management device. The blood glucose data is obtained from a patient during a specified time duration, including a time during delivery of insulin according to a basal insulin rate pattern that is part of the basal rate test. 
     At block  815 , at least one of an amount of basal insulin over-delivered or an amount of basal insulin under-delivered is determined. The over-delivery and/or under-delivery occur in trying to meet a target blood glucose baseline during the basal insulin rate test. In some embodiments, the method  800  includes the BG management device automatically recommending changes, if any, to the basal insulin rate pattern. 
     In some embodiments, the method  800  includes determining an amount of basal insulin over-delivered or an amount of basal insulin under-delivered using the correction factor and the variance from the blood glucose baseline concentration. In some embodiments, the amount of insulin over or under-delivered is determined using an adjusted correction factor. The correction factor may be adjusted using a correction factor multiplier. In some embodiments, recommending a change may include spreading out the change to the basal delivery rate pattern out over a time duration corresponding to a time to a change in direction of the blood glucose data values. 
     In some embodiments, the method includes recommending changes to the basal insulin rate pattern that precede any actual times of over-delivery or under-delivery by a time duration that compensates for a delay or lag time associated with subcutaneous insulin delivery. In some embodiments, the method  800  includes calculating the lag time using at least one of i) the type of insulin delivered during the basal rate test, ii) the activity level of the patient at the time the basal rate test takes place, iii) the fitness level of the patient, and iv) the method of obtaining the blood glucose data, e.g., whether the blood glucose data was obtained from blood or from interstitial fluid. In some embodiments, the method  800  includes calculating the lag time using blood glucose data obtained prior to the basal insulin rate test. 
     According to some embodiments, the BG management device includes an insulin pump. The method  800  includes determining an amount of active insulin (IOB) at the beginning of the basal rate test. The IOB may be determined before delivering basal insulin according to a basal rate pattern of the basal insulin test. In some embodiments, if an amount of active insulin is above a specified threshold active insulin amount, the BG management device may cancel the basal rate test. In some embodiments, the method  800  includes canceling the basal insulin rate test if an insulin bolus dose, such as a correction bolus or a carbohydrate bolus, is delivered during the basal insulin rate test. 
     According to some embodiments, the BG management device includes an insulin pump and a GM. The method  800  includes automatically receiving the sampled blood glucose data from the blood glucose monitor. In some embodiments, the BG management device includes the insulin pump and the blood glucose data is obtained using a separate device. The method  800  includes receiving the sampled blood glucose data into the BG management device from the separate device through a communication port. The communication port may be a wireless port or a wired port. The separate device may be a continuous GM. 
     In some embodiments, the separate device may be a GM that requires some action by the user to obtain a blood glucose reading. For example, the GM may require the user to place a test strip into the GM in order to obtain a glucose reading. In some embodiments, the method  800  may include prompting the user through a user interface to obtain blood glucose data using the separate device. The prompting may be periodic during the basal rate test. 
     In some embodiments, the blood glucose data obtained from the separate device is entered manually into the BG management device. The method  800  includes the BG management device receiving the blood glucose data through the user interface. The user interface is configured for manual entry of blood glucose data, such as by including a keypad and a display. The user reads the blood glucose data from the separate GM and manually enters the blood glucose data into the BG management device. In some embodiments, the method  800  includes the BG management device periodically prompting the user to manually enter a blood glucose value during the basal rate test. 
     According to some embodiments, the BG management device includes a GM and does not include an insulin pump. The basal insulin is delivered according to a basal rate pattern using a second separate device. The sampled blood glucose data is received automatically using the included GM. The method  800  further includes receiving information related to insulin delivery into the BG management device from the separate device, including an amount of insulin delivered according to the basal rate pattern. The BG management device determines at least one of an amount of insulin over-delivered and an amount of insulin under-delivered during the basal rate test using the insulin delivery information and the sampled blood glucose data. 
     In some embodiments, the method  800  includes receiving the insulin delivery information into the BG management device through a communication port. As part of the basal rate test, the BG management device may communicate a recommended change to the basal rate pattern to the separate device using the communication port. This is useful if the separate device is an insulin pump. In some embodiments, the method  800  includes receiving the insulin delivery information into the BG management device by manually entering the insulin delivery information. The information is manually entered via a user interface on the BG management device. Any recommended changes to the basal rate pattern may be displayed on the BG management device. 
     According to some embodiments, the BG management device does not include a GM or an insulin pump. The basal insulin is delivered according to a basal rate pattern using a second separate device, such as an insulin pump for example. The method  800  includes providing insulin delivery information, such as an amount of insulin delivered according to the basal rate pattern, to the BG management device using the second device. 
     The BG management device receives sampled blood glucose data from the second separate device or a third device. At least one of the insulin delivery information and the sampled blood glucose data includes a time-stamp to allow for alignment of the insulin delivery information and the blood glucose data. For example, the time-stamp for the insulin delivery may be the time at which the basal rate changes. The BG management device determines at least one of an amount of insulin over-delivered and an amount of insulin under-delivered during the basal rate test using the insulin delivery information and the sampled blood glucose data. Any recommended changes to the basal rate pattern may be displayed on the BG management device. 
     In some embodiments, the method  800  includes executing the basal insulin rate test during a substantially same time on multiple days. In some examples, the method  800  includes executing an overnight basal rate test. In some examples, the method includes executing an overnight basal rate test that includes an overnight basal rate calibration and verification technique. 
       FIG. 9  is a flow diagram of another method  900  of using a BG management device to execute a basal rate test. At block  905 , sampled blood glucose data is received in a BG management device. The blood glucose data may be obtained from a patient during a specified time duration according to a specified basal insulin rate pattern that is part of the basal rate test. At block  910 , a time varying correction factor c(t) is determined using the sampled blood glucose data and the specified basal insulin rate pattern. At block  915 , a time varying basal rate pattern b(t) is determined. The time varying basal rate pattern is to achieve the target blood glucose baseline. The target blood glucose baseline may be a constant or a time varying function g(t). In some embodiments, the method  900  includes generating a change to the test-specified basal rate pattern using the determined time varying basal rate pattern b(t). In some embodiments, the method includes recommending a change to the test-specified basal rate pattern, such as by using a display for example. 
     The accompanying drawings that form a part hereof, show by way of illustration, and not of limitation, specific embodiments in which the subject matter may be practiced. The embodiments illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. This Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of various embodiments is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled. 
     Such embodiments of the inventive subject matter may be referred to herein, individually and/or collectively, by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept if more than one is in fact disclosed. Thus, although specific embodiments have been illustrated and described herein, it should be appreciated that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations, or variations, or combinations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description. 
     The Abstract of the Disclosure is provided to comply with 37 C.F.R. § 1.72(b), requiring an abstract that will allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own.