The education of patients in prandial insulin dosing related to the structure of bolus calculators

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1 REVIEW ARTICLES / Prace poglądowe Pediatric Endocrinology, Diabetes and Metabolism 2010, 16, 4, ISSN X The education of patients in prandial insulin dosing related to the structure of bolus calculators Marlena Błazik, Ewa Pańkowska 2 nd Department of Pediatrics, Medical University of Warsaw, Poland II Katedra Pediatrii, Klinika Pediatrii Warszawskiego Uniwersytetu Medycznego Adrress for correspondence: Marlena Błazik MD ul. Opaczewska 13/12; Warszawa, Poland phone: (+48) ; fax. (+48 22) ; marlenkaba@op.pl Abstract The metabolic effect of insulin pump therapy depends on precise adjustments of insulin to food intake ratio. Calculation of prandial insulin dose is a complex process employing many variant factors such as pre-prandial glucose and carbohydrate (CHO) levels, glucose index, insulin to CHO ratio (ICR) and active insulin. Bolus calculators are very effective in controlling blood glucose level in patients treated with continuous subcutaneous insulin infusion (CSII). Most of modern bolus calculators are built into the insulin pump unit and are only accessible to pump users. In addition, some models offer nutrition database. Patients education is an essential step in proper interpretation and application of bolus calculators various algorithms. KEY WORDS: type 1 diabetes, bolus calculator, postprandial glycemia, education Streszczenie Wyrównanie metaboliczne w terapii przy pomocy osobistych pomp insulinowych zależy od dokładnego dopasowania dawki insuliny do spożywanego posiłku. Obliczanie dawki insuliny posiłkowej jest złożonym procesem, w którym biorą udział takie czynniki jak stężenie glikemii przed posiłkiem, ilość spożywanego posiłku, indeks glikemiczny, wskaźnik insulina/wymiennik węglowodanowy, jak również ilość insuliny aktywnej po poprzednim bolusie. Kalkulator jest efektywnym narzędziem w kontroli glikemii u pacjentów leczonych przy pomocy ciągłego podskórnego wlewu insuliny. Większość nowoczesnych pomp insulinowych posiada tego typu funkcję, która jest zintegrowana z głównym systemem urządzenia. Ponad to, niektóre modele kalkulatorów posiadają bazy z produktami bądź nawet całymi posiłkami. Podstawowym działaniem mającym na celu optymalizację stosowania tych urządzeń jest edukacja pacjentów. W niniejszym artykule przedstawiono przegląd dostępnych na rynku medycznym kalkulatorów bolusów. SŁOWA KLUCZOWE: cukrzyca typu 1, kalkulator, glikemii poposiłkowa, edukacja Introduction The epidemiological studies suggest that effective treatment of type 1 diabetes (T1D) presents a challenge to health care providers (1). Numerous evidence indicates that the basal/bolus, also referred to as intensive insulin therapy, is the most common method of treatment in patients with T1D (2). Continuous subcutaneous insulin infusion (CSII) has become a convenient treatment method and is now offered frequently (3). Many clinical studies have shown that CSII can improve the metabolic control and, subsequently, patient s quality of life (4, 5). Although, the CSII offers many obvious benefits, failures of CSII therapy have also been observed. The main documented reasons of the pump therapy failure resulting in high level of hemoglobin A 1 c (HbA 1 c) is are erroneous programming of the dose meter, setting wrong type of bolus for a meal or missing the existing prandial bolus (6-8). All of the above functions depend on patient s compliance and level of knowledge. Furthermore, an incorrect setting of prandial insulin dose or of a type of the programmed bolus, have direct impact on targeted postprandial glucose levels. Estimation of prandial insulin dose is a complicated process, in which the blood glucose level, the ingested food and patient s insulin sensitivity must be taken into account every time meal boluses are programmed. To make this complex calculative process more effective and easier on the patient, health care providers and scientists are looking into new tools that could more adequately assist patients in making an informed error-free decision on their prandial insulin dose. Bolus calculators a review of models and features Modern bolus calculators are either designed to be integrated into insulin pumps or work separately in prandial insulin adjusting. The currently available on the marked insulin pump currently available on the market are: the Bolus Wizard calculator built in the insulin pump Paradigm 515, (9), 301

2 The education of patients in prandial insulin dosing related to the structure of bolus calculators Pediatric Endocrinology, Diabetes and Metabolism 2010, 16, 4 Accu-Chek Combo System Roche with a built-in meter-remote for Accu-Check Spirit Combo insulin pump (10), Accu-Chek Compass Roche- personalised diabetes data management for Accu-Chek Spirit or Accu-Chek D-TRON plus pump users (11), bolus calculator with food database bulit in the Animas 2020 insulin pump (12), OneTouch Ping meter-remote by Animas Corporation Johnson-Johnson Company-500 food items from the 5,000-item CalorieKing food database integrated into bolus calculator on meter-remote (12), the Deltec Cozmo the pump calculates the total grams of carbohydrate in patient s meal and suggests the appropriate bolus according to patient s insulin-to-carbohydrate ratio (13), the Insulet Omnipod (Insulet Corporation) (14), the Dana DiabeCare R by Sooil (15), the Diabetics software Smart-Bits, Poland (16). The above described bolus calculators are designed to provide more accurate insulin dose calculation and are more userfriendly for the patient. Most of these instruments to calculate prandial insulin dose take into consideration many necessary factors such as individually targeted adjusted future and present blood glucose levels, insulin to CHO ratio (ICR), amount of CHO and active insulin left over in patient s body from the previous insulin boluses (tab. I). The insulin dose depends on applied insulin action formula. In addition to prandial bolus calculation, majority of these devices also calculate the adjusted bolus dose. Although insulin calculators share many similarities, some differences in their algorithms for calculation of prandial and correction doses can be found (14). One of the quantitative differences lies in the amount of insulin on board (IOB) used, due to variable insulin action scenarios. The IOB feature predicts the percentage of insulin remaining in a function of time (9). For example, when a patient calculates the second insulin bolus 3 hours after the first while the setting on the pump is 2 hours, therefore shorter, with no supplementary blood glucose reading or target range entered, the bolus calculator on the pump will recommend an adjusted higher full meal insulin dose to make-up for the difference. The same principle applies in a reverse scenario, in which the bolus calculator will automatically adjust to a lower bolus dose. The amount of calculated adjusted prandial insulin doses varies according to the actual demands and calls for extended boluses in individual models. Yet another factor that bolus calculator must take into account during the entire process is patient s existing pre-prandial blood glucose level. When the calculator gets information about glucose level and consorts it with diverse insulin action, the effective bolus dose can vary from one pump calculator to another. For example, when comparing a combo with different bolus calculators algorithms, authors found dif- Table I: Tabela I: The bolus calculators without food database comparison Porównanie kalkulatorów bolusów nieposiadających bazy produktów/posiłków Description Opis Users Użytkownicy Using IOB Aktywna insulina Using correction factors Wskaźnik korekcyjny Using current glucose Aktualna glkiemia CHO input Wprowadzenie gramów z węglowodanów Suggestion of bolus type Sugerowanie rodzaju Suggestion of time of an extended bolus Sugerowaanie miary czasu przedłużonego The Bolus Wizard build-in w pompę inuslinową Paradigm 515, 712, 715, 722 users pomp insulinowych yes / tak yes / tak yes / tak yes / tak no / nie no / nie The Dana DiabeCare R Sooil bulid-in insulin pump w pompę insulinową THE Dana DiabeCare users pompy Dana DiabeCare yes / tak yes / tak yes / tak yes / tak no / nie no / nie 302 The Accu-Chek Combo Roche build-in meterremote for insulin pump w glukometr pilot przeznaczony do pompy insulinowej Accu-Chek Spirit Combo pump users pompy Accu- Chek Spirit Combo yes, different algorithm then other bolus calculators tak, ale odmieny algorytm niż w pozostałych kalkulatorach bolusów yes / tak yes / tak yes / tak no / nie no / nie

3 ferent way of active insulin calculation that affected the adjusted correction insulin bolus dose. Most of bolus calculators count all the insulin given preprandially as IOB; whereas, the Accu-Chek Combo System Roche model only counts the insulin given in order to correct preprandial hyperglycemia as IOB, thus, the insulin given to satisfy CHO intake is not counted as IOB. The other advantage of the combo to non combo bolus calculators is providing recommendation for CHO intake in case of BG levels dropping below hypoglycemia alarm and a simple account for recurrent health activity events such as exercise or menstrual status that influence patient s insulin sensitivity. The following difference concerns the food database presentation. This option on the calculator is available in the Accu- Chek Compass Roche, the Animas 2020, the OneTouch Ping, the Insulet Omnipod, the Deltec Cozmo and in the Diabetics software (tab. II). The Diabetics algorithm considers CHO, fat and Table II: The bolus calculators with food database comparison Tabela II: Porównanie kalkulatorów bolusów posiadających bazę produktów/posiłków Description Opis Users Użytkownicy Food database / Baza produktów żywieniowych Food database possibility of addition new product Moliwość rozszerzania bazy produktów żywieniowych The Accu-Chek Compass pocket software program na Pocek PC Accu-Chek pump and/or glucometr users glukometrów i pomp insulionwych Accu-Chek The Animas 2020 build-in insulin pump w pompę insulinową Animas pump users insulinowej Animas The OneTouch Ping build-in insulin pump w pompę insulinową Animas pump users insulinowej Animas yes / tak yes / tak store 500 foods from Calorie King baza 500 produktów z Calorie King yes / tak yes / tak no, but Possibility nie, ale możliwośc The Deltec Cozmo build-in insulin pump w pompę insulinową Cozmo pump users insulinowej Cozmo 600 food database baza 600 produktów no, but possibility nie, ale możliwość The Insulet Omnipod pocket software program na Pocek PC Insulet Omnipod pump users insulinowej Insulet Omnipod 1000 food database baza 1000 produktów no, but possibility nie, ale możliwość The Diabetics pocket and PC software program na Pocek PC i komputery stacjonarne all patients with T1D treated with CSII and MDI*; overweight patients wszycy pacjenci z cukrzyca niezależnie od metody leczenia, pacjenci z nadwagą yes; Polish and English tak, wersja polskoi anglojęzyczna yes / tak CHO yes / tak yes / tak yes / tak yes / tak yes / tak yes / tak Calculation / Kalkulacja węglowodanów FPU no / nie no / nie no / nie no / nie no/ nie yes / tak Calculation Kalkulacja WBT Using IOB Insulina aktywna yes / tak yes / tak yes / tak yes / tak ye / tak no / nie Using correction factors yes / tak yes / tak yes / tak yes / tak yes / tak no / nie Wskaźnik korekcyjny Using current glucose Glikemia przed posiłkiem yes / tak yes / tak yes / tak yes / tak yes / tak no / nie CHO input Wprowadzenie gramów w węglowdanów Suggestion of bolus type Sugerowanie rodzaju Suggestion of time of an extended bolus Sugerowanie czasu przedłużonego * MDI multi daily injection / wielokrotne wstrzyknięcia insuliny yes / tak yes / tak yes / tak yes / tak yes / tak yes / tak no / nie no / nie no / nie no / nie no / nie yes / tak no / nie no / nie no / nie no / nie no / nie yes / tak 303

4 The education of patients in prandial insulin dosing related to the structure of bolus calculators Pediatric Endocrinology, Diabetes and Metabolism 2010, 16, protein (FP) contained in estimated meal boluses, which results in relevant variance in prandial doses of insulin for such rich in fat meals as, for example, pizza. The concept of prandial insulin dosage for the Diabetics software The Diabetics computer program calculates prandial insulin, not only for CHO, but also for FP products. Functions of this system are based on the findings by the Warsaw Pump Therapy School (WPTS) (16-18). According to the WPTS procedures, all potential meal components that are source of energy are taken into account in calculated prandial insulin dose. In order to standardize counting procedure of the food component system, a CHO unit (CU) was defined as 10g of CHO product, in addition, a new measure - a fatprotein unit (FPU), being an equivalent to 100 kcal of fat or/and protein food (17, 19) was added to the formula. The individual patient s insulin sensitivity expressed by ICR is included in calculating CU as well as FPU. Prandial insulin dose calculated by the Diabetics algorithm derives from both CU and FPU content. When IR is introduced into equation, the insulin dose is pre-programmed automatically. Furthermore, a suggestion of required type of bolus: (normal (BN); dual-wave (D-W) or square (S-W)); and D-W /S-W bolus over the span of time in extended bolus is also provided. The main difference between Diabetics and the other bolus calculators is that the former does not consider the current blood glucose concentration, the target blood glucose and the duration of insulin action, thus it does not calculate the adjusted correction insulin dose. Education in using bolus calculators Implementation of every available insulin control tool, particularly for patients with T1D, should be preceded by thorough educational process, focused on proper use of the device and proper insulin adjusting technique individualised to every patient. This well informed, carefully executed adjusting process is important, because in the end, it is the patient the insulin pump user who makes the final decision in the process. Thereby, the educator has to stress the importance of good communication with each individual patient and assuring his understanding of the following medical/technical jargon: ICR; correction factors; duration of insulin action; IOB; and influence of all additional external factors on a meal-bolus dose. Moreover, special attention should be paid to patient s medical/diabetes history and his physical condition that include but are not limited to: patient s recurrent hypoglycaemia episodes; his high glucose level variability; body mass index (BMI), particularly overweight or obesity and patient s current dietary habits, among others. Finally, since patients can forget the proper formula for calculating the manual boluses, a special introductory segment in the Instruction of Use of patient s pump contains a review of manual calculation. The process of implementation of bolus calculator should be completed by final verification and evaluation of the daily glycemia profile, combined with the information on calculated diet calories intake data and the anticipated type of exercise events two to three weeks in advance, in order to establish the insulin cofactors, such as ICR and insulin sensitivity factor (ISF) as well as glycemia target level. Clinically selected groups of diabetic patients and their insulin bolus calculations 1. Diabetic patients with recurrent, asymptomatic or severe hypoglycemia episodes For this group of patients, the time setting is the critical option for targeting blood glucose level and it must be set individually. Moreover, the emphasis is on matching the duration of insulin action with the decrease of ISF which determines the adjusted correction bolus dose. Thereby, when the patient uses various models of insulin pump, the variants in the adjusted correction dose calculation should be well understood. Patients with high variability due to postprandial hyperglycemia The useful model could be Accu-Chek Combo Roche, in which the adjusted correction bolus is not affected (diminished) by the existing active insulin. Moreover, it guides its users consciousness to the expected effect of insulin on blood glucose level over the time, and, accordingly, corrects the deviations from the calculated expected glycemia level. 2. Patients with high BMI, overweight and obesity The practical solution here is the bolus calculator equipped with nutrition data base and CHO estimator: the Accu-Chek Compass Roche; Animas 2020, the OneTouch Ping ; the Insulet Omnipod ; the Deltec Cozmo and the Diabetics). In addition, the Diabetics software can be particularly helpful in calculating the calories energy value of non carbohydrate food products such as: meat; cheese; dairy cream; and other invisible calories of fat contained in meals. Those devices provide many personalized options that can be chosen by the individual patients, however the decision based on individual needs of the patient should be defined by the medical health care provider and well explained by the educator. Impact of bolus calculator on metabolic control Particular attention to prevent postprandial glycemia is the key to avoiding later complications in diabetic patients (20, 21). As previously mentioned, the major cause of insufficient metabolic control of insulin pump treatment is a patient who misses his insulin boluses at mealtime (8). The effectiveness of bolus calculators has been evaluated in three published studies (22, 24). Gross et al. found that calculations of the prandial insulin bolus dose using the bolus calculator, were more effective than standard bolus calculation techniques in achieving target postprandial glucose level, with fewer adjusted correction boluses and supplemental CHO (22). Klupa et al. studies show that mean postprandial blood glucose level was significantly lower in bolus calculator users than in nonusers (23). Furthermore, a continuous glucose monitoring system (CGMS) showed higher subcutaneous glucose levels within the target range in bolus calculator users, although, this small difference was not statistically significant. Shashaj et al. also found that calculations of the prandial insulin bolus dose using Bolus Wizard were more effective than manual math calculations in improving preand postprandial glucose levels, resulting in fewer adjusted cor-

5 rection boluses and no restrictions in CHO content of a meal, and no prandial insulin requirements (24). In addition, the study has shown that bolus calculators are user-friendly and secure a high level of satisfaction among the pediatric diabetic patients (24). Conclusions Recent, more frequent applications of insulin pump therapy, challenged by the difficulties in achieving optimal glycemia control, welcome bolus calculators that assist programming process in achieving the optimal insulin bolus dose. Diabetic patients often forget the correct computation methods for insulin doses when based on empirical calculation. The obvious advantage of the bolus calculators is relieving the patient of the need to memorise all the necessary variables and, thus, avoiding likely eventual erroneous calculation since the recommended optimal bolus insulin dose is generated automatically by the device. Current studies confirm that insulin dose estimated by the bolus calculator, compared to standard manual methods of calculating is more efficient in achieving targeted postprandial blood glucose levels. Majority of available bolus calculators are built in the pump or are connected to it, therefore they are to be used only by their individual owners. Moreover, not all of them have CHO calculators. The Diabetics system is the first bolus calculator that includes CU and FPU for insulin dose calculations. Nevertheless, the introduction of Diabetics algorithm requires clinical trials and proven record of its efficacy, particularly in managing postprandial glycemia spikes following meal boluses. It is important to note that bolus calculators are only a tool and that the suggested bolus estimation is not an exact science, moreover, its function may lead to dependence on calculator algorithm. In conclusion, the introduction of bolus calculator in management technique of patients with T1D has to be preceded by informed adjusting of the bolus insulin dose. This article received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. 5. Churchill J.N., Ruppe R.L., Smaldone A.: Use of continuous insulin infusion pumps in young children with type 1 diabetes: a systematic review. J. Pediatr. Health Care., 2009, 23, Olinder A.L., Kernell A., Smide B.: Missed bolus doses: devastating for metabolic control in CSII-treated adolescents with type 1 diabetes. Pediatr. Diabetes, 2009, 10, Pańkowska E., Skorka A., Szypowska A., Lipka M.: Memory of insulin pumps and their record as a source of information about insulin therapy in children and adolescents with type 1 diabetes. Diabetes Technol. 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Diabetes Care, 2002, 25, Pankowska E., Blazik M., Dziechciarz P. et al.: Continuous subcutaneous insulin infusion vs. multiple daily injections in children with type 1 diabetes: a systematic review and metaanalysis of randomized control trials. Pediatr. Diabetes, 2009, 10, Received: Accepted: Conflicts of interest / Konflikt interesów: Marlena Błazik has received reimbursement of conferences costs from Roche Diagnostics, Abbott Diabetes Care, Sanofi-Aventis,. Moreover she has been a subinvestigator in Novo Nordisk study. Ewa Pańkowska has received reimbursement of conferences costs and speaker s honoraria from Roche Johnson&Johnson, Roche Diagnostics, Novo Nordisk. Moreover she has been an investigator in Novo Nordisk study. Marlena Błazik zatrudniona w Klinice Pediatrii Warszawskiego UM na etacie młodszego asystenta otrzymała finansowanie kosztów uczestnictwa w konferencjach od następujących firm: Roche Diagnostics, Abbott Diabetes Care, Sanofi-Aventis,. Ponadto była współbadaczem w badaniu finansowanym przez firmę Novo Nordisk. Ewa Pańkowska otrzymała finansowanie kosztów uczestnictwa w konferencjach, honoraria za wygłoszenie wykładów od następujących firm: Johnson&Johnson, Roche Diagnostics, Novo Nordisk. Ponadto była badaczem w badaniu finansowanym przez firmę Novo Nordisk 305