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A Patient Safety Initiative For Insulin Pumps

A Patient Safety Initiative For Insulin Pumps. Manufacturing Standards to improve insulin pump use and medical outcomes These proposals are near final, although suggestions for editorial changes are still welcome.

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A Patient Safety Initiative For Insulin Pumps

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  1. A Patient Safety Initiative For Insulin Pumps Manufacturing Standards to improve insulin pump use and medical outcomes These proposals are near final, although suggestions for editorial changes are still welcome. Send your approval or comments to: John Walsh, PA, CDE at jwalsh@diabetesnet.com or by calling (619) 497-0900

  2. Over 500,000 insulin pumps are in use around the world, yet no formal guidelines regarding manufacturing standards and medical practice have been adopted by the diabetes clinical community and pump manufacturing industry. These are suggestions for such standards and once approved will be incorporated into future insulin pumps or into current pumps where software changes allow. These manufacturing standards are designed to Provide safer dosing increments to pump users Allow clinicians to make consistent dosing decisions when managing a variety of pumps Allow adjunctive medical and accessory personnel (ER, surgical, school nurses, etc.) to more easily be trained and interact with insulin pumps Introduction

  3. Background • Older insulin pumps were primarily designed to improve insulin delivery. • Technological advances have transformed today’s pumps and controllers into data collection centers. As additional data from continuous glucose monitoring devices becomes more widely used, the value of this data becomes even greater. • Data needed for clinical monitoring and decisions is available in today’s pump and can be accessed through screen displays, alerts, or recommendations. Using routine monitoring techniques and data analyses, a pump can inform the wearer regarding their current control and changes in control.

  4. John Walsh, PA, CDE Ruth Roberts, MA Gary Scheiner, MS, CDE Timothy Bailey, MD, FACE Steve Edelman, MD Carol Wysham, MD Joseph Largay, PA, CDE David Horwitz, MD Etc These Mechanical Standards Are Supported By: * Reservations by a signatory about a standard will be noted

  5. Definitions • TDD – total daily dose of insulin (all basals and boluses) • Basal –background insulin pumped slowly through the day to keep BG flat • Bolus – a quick surge of insulin as • Carb boluses to cover carbs • Correction boluses to lower high readings that arise from too little basal insulin delivery or insufficient carb boluses • Bolus On Board (BOB) – the units of bolus insulin with glucose-lowering activity still working from recent boluses • Duration of Insulin Action (DIA) – time that a bolus will lower the BG. This is used to calculate BOB.

  6. Why Insulin Pump Guidelines Are Needed These mechanical standards are designed to improve: • Consistency of pump settings between pump manufacturers • Accuracy and safety of carb and correction factor increments • Safety and consistency of DIA defaults and increments • Consistency in the handling of BOB and insulin stacking • Improved monitoring for hypoglycemia & hyperglycemia • Improved entry of glucose values into bolus calculations • Faster notification of excessive use of correction boluses • Faster identification of control problems related to infusion sets

  7. # Topic Carb Factor Increments Correction Factor Increments Carb Factor Accuracy Correction Factor Accuracy DIA Default Times DIA Time Increments Handling Of BOB Overview Slides are numbered by topic for easy reference. # Topic 8. Multi-Linear And Curvilinear DIA 9. Hypoglycemia Alert 10. Hyperglycemia Alert 11. Correction Bolus Alert 12. Insulin Stacking Alert 13. Automatic Entry Of BG Values 14. Infusion Set Monitoring

  8. ReviewWhat % of The TDD Changes The BG? To understand some slides that follow, it helps to know the significance of the effect that a change in the TDD has on the glucose level. Using a 450 Rule to set the carb factor and a 2000 Rule to set the correction factor: • 1.25% of an appropriate TDD for an individual is sufficient to change the glucose about 25 mg/dl when given as a single dose • A 5% change in the TDD is equivalent to about a 25 mg/dl increase or decrease in the glucose through the day • A 5 to 6% change in the carb factor (about 2.5% to 3% of the TDD) is sufficient to change the glucose about 20 mg/dl per meal.

  9. 1 Carb Factor Increments

  10. 1 Standard For: Carb Factor Increments Carb factor increments shall be less than or equal to 5% of the next larger whole number so that each single step adjustment causes subsequent carb boluses to change by no more than 5% from previous doses. We recommend minimum carb factor increments of: 5 1.0 g/u above 20 g/u 0.5 g/u for 10 to 20 g/u 0.2 g/u for 5 to 9.8 g/u 0.1 g/u for 3 to 4.9 g/u 0.05 g/u for 0.1 to 2.95 g/u 5 Improved carb factor increments recommended by Gary Scheiner, MS, CDE

  11. Carb Factor (CarbF) Increments 1 Issue: Current carb factor increments are too large to provide accurate carb boluses, especially for those who use smaller carb factors. This can represent a safety issue in situations where current carb factors lack the precision required to avoid excessive hyperglycemia and hypoglycemia.

  12. ExampleCarb Factor Increments 1 • Most pumps offer 1 gram per unit as their smallest CarbF increment. This increment becomes relatively large for CarbFs below 15 or 20 g/u. • For instance, when the carb factor is reduced from 10 to 9 g/u, all subsequent carb boluses are increased by 11.1%. A shift in the carb factor from 1u/5g to 1u/4g causes each subsequent carb bolus to increase by 25%. • For most pump users, a change in the carb factor larger than 5 or 6% would be expected to create more than a 20 mg/dl shift in the glucose following each meal.

  13. ExampleImpact On BG From CarbF Adjustments 1 This table shows the average additional fall in glucose after each meal of the day when a carb factor is reduced from 10 grams per unit to 9 grams per unit (for appropriate weight & TDD), and from 5 gr per unit to 4 gr per unit. ** Meals with higher carb intake would magnify these sample glucose changes * Calculated as avg. carbs/day – avg. carbs/day X 1 X 2000 new carb factor old carb factor 3 TDD

  14. ReviewMedian Carb Factor 1 In unpublished data from the Cozmo Data Analysis Study: • The median (middle) carb factor was 11.2 g/u • Almost all pumpers used carb factors below 20 g/u • 40% or more use carb factors of 10 g/u.

  15. What Current Changes In CarbFs Do 1 Table shows how subsequent carb boluses are affected by a one-step reduction in the CarbF using different CarbF increments. Yellow area shows values for most current pumps. Green areas show safer increments that impact subsequent boluses less than 5%.

  16. 2 Correction Factor Increments

  17. 2 Standard For: Correction Factor Increments For similar reasons, correction factor increments shall be less than or equal to 5% of the next larger whole number so that each single step adjustment causes subsequent correction boluses to change by no more than 5% from previous doses. We recommend minimum correction factor increments of: 5.0 mg/dl per u above 80 mg/dl per u 2.0 mg/dl per u for 40 to 78 mg/dl per u 1.0 mg/dl per u for 20 to 39 mg/dl per u 0.5 mg/dl per u for 10 to 19.5 mg/dl per u 0.2 mg/dl per u for 5 to 9.8 mg/dl per u 0.1 mg/dl per u for 3 to 4.9 mg/dl per u 0.05 mg/dl per u for 0.1 to 2.95 mg/dl per u

  18. 3 Carb Factor Accuracy

  19. 3 Standard For: Verification Of Carb Factor Accuracy Insulin pump companies shall record and publish each year the carb factors used in insulin pumps returned for upgrade or repair. This report will include sufficient numbers of pumps to ensure statistical significance for commonly used carb factors between 5 and 20 grams per unit to ensure that pump training and clinical followup are assisting in the selection of accurate carb factors. To improve accurate selection of carb factors, efforts shall be undertaken to automate carb factor testing.

  20. Personal Carb Factors 3 Issue: Many carb factors used in insulin pumps today are poorly tuned to the user’s need. When a carb factor does not match an individual’s need, other sources of error in carb bolus calculations are significantly magnified.

  21. Review Carb Factors In Use 1 3 Avg. carb factors* for 468 consecutive Cozmo insulin pump downloads (>126,000 boluses) are shown in blue Note that they are NOT bell-shaped or physiologic People prefer “magic” numbers – 7, 10, 15, and 20 g/unit – for their carb factors * Determined directly from grams of carb divided by carb bolus units for each carb bolus 10 7 115 20 1

  22. ReviewCarb Factors In Use 1 3 MANY magic carb factors, shown in blue, are inaccurate. A more normal or physiologic distribution is shown in green Use of magic numbers creates major, consistent bolus errors that magnify other sources for error 10 7 115 20 1

  23. 4 Correction Factor Accuracy

  24. 4 Standard For: Verification Of Corr Factor Accuracy Insulin pump companies shall record and publish each year the correction factors used in insulin pumps returned for upgrade or repair. This report will include sufficient numbers of pumps to ensure statistical significance for commonly used correction factors between 20 and 80 mg/dl per unit to ensure that pump training and clinical followup are assisting in the selection of accurate correction factors. To improve accurate selection of correction factors, efforts shall be undertaken to automate correction factor testing.

  25. Personal Correction Factors 4 Issue: Many correction factors used in insulin pumps today are poorly tuned to the user’s need. This inaccuracy significantly magnifies other sources of error in correction bolus calculations.

  26. Review Correction Factors In Use 1 4 Avg. correction factors in use for 452 consecutive Cozmo insulin pump downloads Like carb factors, correction factors in use are NOT bell-shaped or physiologic. A more accurate choice of correction factors would create a bell-shaped curve. Users or clinicians appear to frequently select “magic” numbers for correction factors. 10 7 115 20 1

  27. 5 DIA Default Times

  28. 5 Standard For:DIA Default Times Default duration of insulin action (DIA) times in current pumps vary widely between 3 and 6 hours. For safety in bolus calculations that depend on DIA, the DIA default shall be set no shorter than 4.5 hours in pumps that determine DIA in a linear fashion and no shorter than 5 hours in pumps that determine DIA in a curvilinear or multi-linear fashion. These default times apply for the rapid insulins (lispro, aspart, and glulisine) in use at this time.

  29. DIA Default Time Settings 5 Issue: DIA measures the glucose-lowering activity of a carb or correction bolus over time. Current default times for DIA range from 3 to 6 hours in different pumps. • The DIA is often considered another tool to “improve control” rather than being set at an appropriate value and focusing on more appropriate changes in basal rates or carb and correction factors to improve control. • A DIA that is too short allows excess unrecognized bolus insulin to accumulate, usually in the afternoon and evening hours. • Example: a bolus given at 7 am appears to have no activity after 10 am. If a high BG occurs 10 am, more bolus than needed will be given. At lunch, the bolus will be excessive, regardless of the BG at that time, creating a high likelihood of hypoglycemia.

  30. ReviewHow Long Do Boluses Lower The BG? 5 • Numerous GIR studies show rapid insulins lower the glucose for 5 hours or more. • With Novolog (aspart) at 0.2 u/kg (0.091 u/lb), 23% of glucose lowering activity remained after 4 hours.12 • Another study found Novolog (0.2 u/kg) lowered the glucose for 5 hours and 43 min. +/- 1 hour.13 • After 0.3 u/kg or 0.136 u/lb of Humalog (lispro), peak glucose-lowering activity was seen at 2.4 hours and 30% of activity remained after 4 hours. 11 These times would be longer if the unmeasured basal suppression in pharmacodynamic studies were accounted for. 11 From Table 1 in Humalog Mix50/50 product information, PA 6872AMP, Eli Lilly and Company, issued January 15, 2007. 12 Mudaliar S, et al: Insulin aspart (B28 Asp-insulin): a fast-acting analog of human insulin. Diabetes Care 1999; 22:1501-1506. 13 L Heinemann, et al: Time-action profile of the insulin analogue B28Asp. Diabetic Med 1996;13:683-684.

  31. ReviewShort DIAs Hide Bolus Insulin Activity 5 A short DIA time hides true BOB level and its glucose-lowering activity. This can be a safety issue in that it: • Leads to “unexplained” lows • Leads to incorrect adjustments in basal rates, carb factors, and correction factors • Causes users to start ignoring their “smart” pump’s advice An inappropriately long DIA time overestimates bolus insulin activity – this leads to underdosing rather than overdosing on subsequent boluses. DIA should be based on an insulin’s real action time. Do NOT modify the DIA time to fix a control problem

  32. ReviewDuration Of Insulin Action (DIA) 5 Accurate bolus estimates require an accurate DIA. DIA times shorter than 4.5 to 7 hrs may hide BOB and its glucose lowering activity Glucose-lowering Activity 0 6 hrs 2 hrs 4 hrs

  33. ReviewDIA 5 Large doses (0.3 u/kg = 30 u for 220 lb. person) of “rapid” insulin in 18 non-diabetic, obese people Med. doses (0.2 u/kg = 20 u for 220 lb. person) This study suggests that residual insulin activity can lower glucose levels for 7-8 hours Regular Apidra product handout, Rev. April 2004a

  34. ReviewDoes Dose Size Affect DIA? 5 This graphic suggests that smaller boluses do not lower the BG as long as larger boluses. However, this may not be true – see next 2 slides. Size of the injected Humalog dose for a 154 lb or 70 kg person: 0.05 u/kg = 3.5 u 0.1 u/kg = 7 u 0.2 u/kg = 14 u 0.3 u/kg = 21 u Woodworth et al. Diabetes. 1993;42(Suppl. 1):54A

  35. ReviewPharmacodynamics Is Not DIA 5 • The DIA time entered into an insulin pump is based on studies of insulin pharmacodynamics. • However, the traditional method used to determine the pharmacodynamics of insulin may underestimate insulin’s true duration of action, as shown in the next two slides.

  36. ReviewPharmacodynamics Underestimates DIA And Overestimates Impact Of Bolus Size 5 • To measure pharmaco-dynamics, glucose clamp studies are done in healthy individuals (0.05 to 0.3 u/kg) • Because there is no basal suppression, this injected insulin ALSO SUPPRESSES normal basal release from the pancreas (grey area in figure)

  37. ReviewPharmacodynamic Time Does Not Equal DIA 5 After accounting for the lack of basal suppression, • True DIA times become longer than the PD times derived in traditional research • If basal suppression activity is accounted for, small boluses may be found to have a longer DIA than it currently appears, erasingsome of the apparent variation in DIA related to bolus size • Some of the apparent inter-individual variation in pharmacodynamics may also disappear

  38. 6 DIA Time Increments

  39. 6 Standard For: DIA Time Increments For safe and accurate estimates of residual BOB, DIA time increments shall be no greater than 15 minutes.

  40. DIA Time Increments 6 Issue: Current DIA time increments vary from 15 minutes to 1 hour in different pumps • When a pump’s DIA time is adjusted, large time increments, such as 1 hr, can introduce large changes in subsequent estimates of BOB. • For example, when the DIA is reduced from 5 hours to 4 hours, subsequent BOB estimates are decreased and recommendations for carb boluses are increased by about 25%.

  41. ReviewGlucose Infusion Rate (GIR) Studies 6 Most GIR studies suggest that pharmacodynamic action of insulin varies only about 25% to 40% between individuals. For a DIA time of 5 hr and 15 min, a 25% range is equivalent to 1 hr and 20 min, such as from 4 hrs and 30 min to 5hr and 50 min. A pump that has 1 hr DIA increments would enable the user to select only 1 or 2 settings within this physiologic range, while a 30 min increment would allow only 2 or 3 choices that are close to a physiologic range.

  42. 7 Handling Of BOB Bolus On Board (BOB)

  43. 7 Standard For:Handling Of BOB For safe and accurate BOB measurement: BOB measurements shall include all carb and correction boluses given within the selected DIA When residual BOB is present at the time of a bolus, the BOB shall be subtracted from both carb and correction bolus recommendations. When BOB exceeds the current correction bolus need or the current carb plus correction need, the user will be alerted to how many grams of carb they need to eat.[(BOB – correction & carb bolus need) X carb factor]

  44. Handling Of BOB 7 Issue: Current pumps differ significantly in what is counted as BOB and in whether or not BOB is subtracted from subsequent carb boluses. Most insulin pumps assume that excess BOB does not need to be taken into account when determining the next carb bolus. Though commonly determined in this way, the resulting bolus dose recommendations can cause unexplained and unnecessary insulin stacking and hypoglycemia.

  45. ExampleInsulin Stacking 7 With a bedtime BG of 173 mg/dl, is there an insulin deficit or a carb deficit? Bedtime BG = 173 mg/dl Correction Dessert Dinner 6 pm 8 pm 10 pm 12 am

  46. ReviewFrequency Of Insulin Stacking 7 CDA1 Study Results Of 201,538 boluses, 64.8% were given within 4.5 hrs of a previous bolus Although 4.5 hours may underestimate true DIA, use of this minimal DIA time shows that some BOB is present for MOST boluses 4.5 hrs

  47. ReviewBolus On Board (BOB) 7 An accurate measurement of the glucose-lowering activity that remains from recent boluses: • Prevents insulin stacking • Improves bolus accuracy • Allows the current carb or insulin deficit to be determined aka: insulin on board, active insulin, unused insulin* * Introduced as Unused Insulin in 1st ed of Pumping Insulin (1989)

  48. ReviewHow Current Pumps Handle BOB 7 * Except when BG is below target BG * “Yes” is generally safer

  49. ExampleUnsafe BOB1 Handling 7 If a pump user gets frustrated with a high BG and they overdose to speed its fall, or they exercise longer or more intensely than anticipated, they can acquire a significant excess in BOB. In this situation, most current pumps recommend that a bolus be given for all carb intake regardless of how much BOB is actually present. If BOB is greater than the correction bolus requirement at the time, the pump’s bolus recommendation may introduce a risk for hypoglycemia. 1 Pumping Insulin, 1st ed, 1989, Chap 12, pgs 70-73: The Unused Insulin Rule

  50. ExampleDifferences In Bolus Recommendations 7 The graphic shows how widely bolus recommendations vary from one pump to another for the same situation. Situation: BOB = 3.0 u and 30 gr. of carb will be eaten at these glucose levels Carb factor = 1u / 10 gr Corr. Factor = 1 u / 40 mg/dl over 100 Target BG = 100 TDD = ~50 u units mg/dl Omnipod bolus cannot be determined - it counts only correction bolus insulin as BOB

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