Preliminary Proposal For Insulin Pump Standards

Standards to improve insulin pump use and medical outcomes

These proposals are not yet final but are made available for review and editorial comment. Any suggestions you have for improvements or changes, or for additional approaches to improve diabetes care are welcomed. Any major contributions will be attributed.

These Standards Are Supported By: John Walsh, PA, CDE, and Ruth Roberts, MA

You (#4,6)*

* Any reservations you have about a particular standard will be noted

ReviewDefinitions

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 or 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.

The Role Of Insulin Pumps

Insulin pumps should 1. Lower A1c and eAG levels

2. Decrease the frequency and severity of hypoglycemia

3. Provide safe and reliable insulin dosing to users

4. Reduce complications

5. Improve quality of life

Proposal For Insulin Pump Standards

These standards to improve pump use and outcomes are designed to:

1. Reduce inconsistencies in pump settings between pump manufacturers

2. Improve the accuracy and safety of carb and correction factors in use

3. Improve safety of DIA time increments and defaults that are in use

4. Consistently account for and apply BOB

5. Improve monitoring and identification of infusion set failure

6. Improve monitoring of hypoglycemia & hyperglycemia

7. Identify excessive use of correction boluses

8. Reduce blind bolusing and non-entry of glucose values into pumps

ReviewInconsistent Dosing From Insulin Pumps

There are several significant sources for error in bolus doses from today’s insulin pumps. Widespread use of inaccurate carb factors

Excessively large carb factor increments

Widespread use of inaccurate correction factors

Wide variations in how BOB is handled and in DIA default times between pump manufacturers

Wide variations in DIA defaults between pump manufacturers

Intellectual Property

Issue: Optimal glucose values for those who have diabetes is critical to prevention of disability and early death. Devices owned and used by those with diabetes contain unique information that can be used to improve control and reduce complication risks.

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Standard For:Intellectual Property

We recommend that all existing and future patents that may contribute to improvements in glucose control be made available at a reasonable cost to any device manufacturer who wants to use them to improve glucose control.

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Issue: Current carb factor increments are too large for smaller carb factor numbers. This lack of precision for carb boluses may create excess hyperglycemia or hypoglycemia for many pump users.

2Carb Factor (CarbF) Increments

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% in most pumps.

A shift in the carb factor from 1u/5g to 1u/4g causes each subsequent carb bolus to increase by 25%.

When carb boluses make up 50% of the TDD, a change in the a carb factor larger than 2.5% would be expected to create more than a 25 mg/dl shift in the glucose following each meal.

Finer CarbF increments would allow safer and more precise adjustment of subsequent carb boluses.

2ExampleCarb Factor Increments

Example: TDD = 40u, carb factor ~1u/11g, corr factor ~1u/60 mg/dlcarb boluses = 20u or ~6u/meal x 6% =.36u x 60 = a 22 mg/dl change in BG

What Current Changes In CarbFs DoTable shows how a one-step reduction in the CarbF using various CarbF increments affect the size of subsequent carb boluses. Yellow

area shows impact from most pumps. Green (preferred) areas show increments that impact subsequent boluses less than 5%.

Orig. CF CF step 1 g/u CF step 0.5 g/u CF step 0.25 g/u CF step 0.12 g/u CF step 0.06 g/u20 5.26% 2.63% 1.32% 0.66% 0.32%19 5.56% 2.78% 1.39% 0.69% 0.34%18 5.88% 2.94% 1.47% 0.74% 0.36%17 6.25% 3.13% 1.56% 0.78% 0.38%16 6.67% 3.33% 1.67% 0.83% 0.41%15 7.14% 3.57% 1.79% 0.89% 0.44%14 7.69% 3.85% 1.92% 0.96% 0.47%13 8.33% 4.17% 2.08% 1.04% 0.51%12 9.09% 4.55% 2.27% 1.14% 0.56%11 10.00% 5.00% 2.50% 1.25% 0.61%10 11.11% 5.56% 2.78% 1.39% 0.68%9 12.50% 6.25% 3.13% 1.56% 0.77%8 14.29% 7.14% 3.57% 1.79% 0.87%7 16.67% 8.33% 4.17% 2.08% 1.02%6 20.00% 10.00% 5.00% 2.50% 1.22%5 25.00% 12.50% 6.25% 3.13% 1.53%4 33.33% 16.67% 8.33% 4.17% 2.04%3 50.00% 25.00% 12.50% 6.25% 3.06%2 100.00% 50.00% 25.00% 12.50% 6.12%

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ExampleImpact On BG From CarbF Adjustments

This table shows the average additional fall in glucose that is likely 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 again a reduction from 5 grams per unit to 4 grams per unit.

How A 1-Step Reduction In Carb Factor Impacts Avg. Meal BG

Change in CarbF

Typical weight

Carb/dayAvg carb gms/meal

Increased units/meal

Additional BG fall per meal*

1/10 to 1/9 160 lb 220 gr 73 gr + 0.9 u - 40 mg/dl

1/5 to 1/4 240 lb 330 gr 110 gr + 5.5 u - 124 mg/dl

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Calculated as carb grams per day X increase in avg. carb bolus size 3

We recommend that carb factor increments be small enough that a single step adjustment in a factor causes subsequent carb boluses to change by no more than 5% from previous bolus doses for the same number of grams of carb.

Standard For:Carb Factor Increments

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Inaccurate Carb Factors

Issue: A carb factor that does not match the individual using it will significantly magnify other sources of error in the calculation of carb bolus doses. Many carb factors used in insulin pumps today are poorly tuned to users.

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Review Actual Carb Factors In Use 1

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

7

10

115

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J. Walsh, D. Wroblewski, and TS Bailey: Insulin Pump Settings – A Major Source For Insulin Dose Errors, Diabetes Technology Meeting 2007

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3

ReviewActual Carb Factors In Use 1

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, though consistent bolus errors that magnify other sources of error

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10

115

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J. Walsh, D. Wroblewski, and TS Bailey: Insulin Pump Settings – A Major Source For Insulin Dose Errors, Diabetes Technology Meeting 2007

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3

1. To encourage use of consistent and accurate carb factors in pumps, we request that insulin pump companies jointly determine what range of carb factor rule numbers (CarbF x TDD) provide optimal glucose results that lead to a lower eAG and less hypoglycemia for various TDD ranges and carb intakes as a percentage of calories.

2. We request that insulin pump companies measure and publish each year the carb factors in use for 200 random downloads from pumps that use carb factors. This information is needed as an overview to guide interventions directed at reducing errors in carb factor settings.

3. We recommend that carb factors be monitored within each pump for accuracy and effectiveness with a report available to users or clinicians.

Standards For:Carb Factor Settings

3

To assist users in setting accurate CarbFs, insulin pumps should allow the user to compare their current CarbF against an optimal settings range of CarbF Rule Numbers. Proposed CarbF Rule Numbers for various TDDs:

3ExampleCarb Factor Settings

Proposed Rule # Ranges For Recommending Carb Factors *

Carb Factor Rule Number Range

Avg. TDD More aggressive Less aggressive

40 u or less 400 500

40 to 80 u 425 600

Over 80 u 500 650

* Optimal ranges would be determined from research studies of best practices

Inaccurate Correction Factors

Issue: A correction factor that does not match the individual using it will significantly magnify other sources of error in the calculation of correction bolus doses. Many correction factors used in insulin pumps today are poorly tuned to users.

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Review Actual Correction Factors In Use 1

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

Users or clinicians often select “magic” numbers for their correction factors.

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10

115

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J. Walsh, D. Wroblewski, and TS Bailey: Insulin Pump Settings – A Major Source For Insulin Dose Errors, Diabetes Technology Meeting 2007

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1. To encourage use of consistent and accurate correction factors in pumps, we request that insulin pump companies jointly determine what range of correction factor rule numbers (CorrF x TDD) provide optimal glucose results that lead to a lower eAG and less hypoglycemia for various TDD ranges, and publish them for users and clinicians to use.

2. We request that insulin pump companies voluntarily measure and publish each year the correction factors in use for 200 consecutive downloads from pumps that use correction factors.

3. We recommend that correction factors be monitored within each pump for accuracy and effectiveness with a report available to users or clinicians.

Standards For:Correction Factor Settings

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To assist users in setting accurate CorrFs, insulin pumps should allow the user to compare their current CorrF against an optimal settings range of CorrF Rule Numbers. Proposed CorrF Rule Numbers for various TDDs:

4ExampleCorrection Factor Settings

Proposed Rule # Ranges For Recommending Corr. Factors*

Correction Factor Rule Number Range

Avg. TDD More aggressive Less aggressive

40 u or less 1700 2000

40 to 80 u 1800 2200

Over 80 u 1800 2400

* Optimal ranges would be determined from research studies of best practices

Basal/Carb Bolus Balance

Issue: Correction boluses are used to correct for deficits in insulin that arise from inadequate basal delivery or inadequate carb boluses. Because the reason for their use cannot be clearly identified as basal or bolus, they should not be included in basal/bolus balance.

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Standard For:Basal/Carb Bolus Balance

We propose that basal/carb bolus balance is a more definitive term and should replace basal/bolus balance. Basal/carb bolus balance should NOT include correction bolus doses which will be listed separately to more clearly define and understand control issues.

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ExampleBasal/Carb Bolus Balance

How a pump might display insulin information:

TDD = 40.0 u in last 7 days:

% of TDD units

Basal 30% 12 u

Carb boluses50% 20 u

Corr. boluses20%(+12%) 8 u (+ 4.8 u)

Basal/Carb bolus balance = 0.6 (12u/20u) or 60%. This particular imbalance would typically favor adding more of the correction bolus excess to basal delivery.

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Issues:

1. The default DIA times in current pumps vary widely between 3 and 6 hours*

2. Many users shorten their default DIA to increase the size of their boluses without realizing that this introduces significant errors into bolus (and ultimately basal) doses.

* DIA times that are too short hide bolus insulin activity and create insulin stacking. DIA times that are too long overestimate bolus activity.

6Duration Of Insulin Action Default Times

Standard For:Duration Of Insulin Action (DIA) Time

We recommend that a panel of experts in insulin action review existing pharmacodynamic studies, consider differences between pharmacodynamics and DIA time, and provide guidance on an acceptable range of DIA times to recommend to clinicians and users to improve the accuracy of bolus calculations.

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Issue: Current DIA time increments vary from 15 minutes to 1 hour in different pumps

When a DIA time is changed in a pump, a larger time increment, such as 1 hr, can create an excessive change in subsequent estimates of BOB.

For example, when the DIA is reduced from 5 hours to 4 hours, subsequent BOB estimates are decreased, while recommendations for carb boluses would increase.

7DIA Time Increments

Most GIR studies suggest that pharmacodynamic action of insulin varies about 25% between individuals. For a DIA time of 5 hr, a 25% range is equivalent to 1 hr and 15 min, such as from 4 hrs and 15 min to 5hr and 30 min.

A pump that has only 1 hr DIA increments would enable the user to select only one setting within a physiologic range, while a 30 min increment would allow only 2 or 3 choices that are close to a physiologic range.

7ReviewGlucose Infusion Rate (GIR) Studies

For safety and accuracy, we recommend that DIA time increments be no greater than 15 minutes to allow more accurate estimation of residual BOB.

Standard For:DIA Time Increments

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ReviewBolus On Board (BOB)

An accurate measurement of the glucose-lowering activity that remains from recent boluses helps:

• Prevent insulin stacking

• Improve 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)

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ExampleAn Accurate BOB Can Avoid Insulin Stacking

Bedtime BG = 173Is there an insulin or a carb deficit?

6 pm 8 pm 10 pm 12 am

DinnerDinner

DessertDessertCorrectionCorrection Bedtime BG

= 173 mg/dl

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ReviewInsulin Stacking Is Common

CDA1 Study ResultsOf 201,538 boluses, 64.8% were

given within 4.5 hrs of a previous bolus

An accurate DIA shows that some BOB is present for MOST boluses

Note that 4.5 hours may underestimate true DIA

4.5 hrs

J. Walsh, D. Wroblewski, and TS Bailey: Disparate Bolus Recommendations In Insulin Pump Therapy. AACE Meeting 2007

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ReviewHow Current Pumps Handle BOB

What’s In the BOB & What Is It Applied Against?

BOB Includes This Type Of Bolus

BOB Is Subtracted From This Type Of Bolus

Carb Correction Carb Correction

Animas 2020 Yes Yes No* Yes

Deltec Cozmo Yes Yes Yes Yes

Insulet Omnipod No Yes No Yes

Medtronic Paradigm Yes Yes No Yes

* Except when BG is below target BG

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ExampleBolus Recommendations Differ Significantly

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

0

1

2

3

4

60 90 120 150 180 210 240

Deltec Cozmo Animas 1250 Medtronic 522

units

mg/dl

Omnipod bolus cannot be determined - it counts only correction bolus insulin as BOB

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The graphic shows how widely bolus recommendations vary from one pump to another for the same situation.

ExampleUnsafe BOB Handling

If a pump user gets frustrated with high BGs and they overdose to speed the drop in their BG, or they exercise longer or more intensely than they anticipated, they can acquire a significant excess in BOB.

In this situation, most pumps bolus for all carb intake regardless of how much BOB is present. A subsequent bolus will deliver an excess of insulin if the glucose is not high enough to offset the excess BOB.1

This introduces a significant risk for hypoglycemia from the pump’sexcessive bolus recommendations.

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1 Pumping Insulin, 1st ed, 1989, Chap 12, pgs 70-73: The Unused Insulin Rule

Issue: Most bolus calculators in current insulin pumps assume that excess BOB does not need to be taken into account when determining the next carb bolus.

Because of the way they are determined, bolus dose recommendations from most pumps can cause unexplained and unnecessary insulin stacking and hypoglycemia.

8Current BOB Handling

Standard For:BOB Handling

For safe and accurate BOB measurement, we recommend that:

BOB include all carb and correction boluses Residual BOB be subtracted from both carb and correction bolus recommendations delivered within the DIA*

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* Assumes that the DIA time chosen by the clincian or user is accurate.

BOB Handling

Exception to usual BOB handling: When a second bolus is taken for unplanned carb intake

or desert that is consumed within 60 minutes or so* of a meal bolus, BOB should not be taken into account for the second bolus because the impact of the first bolus cannot be accurately determined.

Given that, it is wise to account for BOB as soon after a meal as possible, such as within 60 to 90 minutes (adjustable), to provide early warning if the bolus given was excessive or inadequate.

It is always safer, though not always more accurate, to account for and apply all BOB in subsequent boluses.

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* Adjustable

Blind Bolusing

Issue: Pump users often bolus for carbs without checking their glucose first. With no glucose reading, the pump does not account for BOB that may be present at the time, and the bolus is not appropriately adjusted for potentially high or low glucose levels.

Blind bolusing often leads to insulin stacking.

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Standard For:Blind Bolusing

We recommend that insulin pumps alert* the wearer when there is sufficient insulin stacking to introduce a significant error in a current bolus.

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* Adjustable for an expected mg/dl drop in glucose with visible, audio, or vibratory output.

When a carb bolus is planned without a recent BG check, but BOB is more than 1.25% of the average TDD (enough to cause about a 25 mg/dl drop in the glucose), the pump will recommend that the wearer do a BG check due to an excess in BOB.

For instance, for someone with:Avg TDD 1.25%* of TDD43 units 0.54 units

This individual would be alerted whenever they give a bolus but have 0.54 u or more of BOB present.

9ExampleInsulin Stacking or BOB Alert

* 1.25% of TDD provides a reasonable degree of safety but may need modification

Inadequate Manual Entry Of BGs

Issue: Pump users often do not enter BG values into their pump if they must do it manually.

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Inadequate Manual Entry Of BGs

Issue: In the CDA study where BG values can be entered either manually or automatically, users entered only 2.6 BG values per day manually versus 4.1 values per day for pumps that had an attached glucose meter. This means that BOB may be taken into account for 1.5 additional boluses per day when BG readings are not automatically entered.

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Standard For:Inadequate Manual Entry Of BGs

Due to a significant decrease in glucose entry when BGs must be entered manually, and the benefit to control that this provides, we recommend that all pumps be enabled to have direct BG entry of BG test results from two or more meters.

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Correction Bolus Excess

Issue: Hyperglycemia is more common than hypoglycemia for most people on insulin pumps.

When glucose levels consistently run high, many pump users address the problem by giving frequent correction boluses rather than increasing their basal rates or carb boluses.

In these cases, the correction bolus % of the TDD can become excessive, but this information is either not shown in some pumps or no alert is given regarding the excess.

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Standards For:Correction Bolus Excess

We suggest that the pump wearer and clinician be alerted when the wearer uses more than 8% (adjustable) of their TDD for correction bolus doses for at least 4 days in a row (adjustable).

We recommend that, once an excess in correction bolus is identified, that the user be given instruction in how to safely distribute any excess into carb boluses or basal rates.

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Excess Hypoglycemia

Issue: Current insulin pumps and glucose monitors do not warn users that they are experiencing hypoglycemia that is too severe or too frequent.

Although most insulin pumps contain adequate data to do so, they do not provide sufficient guidance for correcting this serious problem.

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Standard For:Excess Hypoglycemia

We recommend that insulin pumps which store glucose and insulin dosing data alert users when they experience severe or excessive hypoglycemia and provide specific guidance regarding likely causes.

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Excess Hyperglycemia

Issue: Current insulin pumps and glucose monitors do not warn users that they are experiencing hyperglycemia that is too severe or too frequent.

Although most insulin pumps contain adequate data to do so, they do not provide sufficient guidance for correcting this serious problem.

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Standard For:Excess Hyperglycemia

We recommend that insulin pumps which store glucose and insulin dosing data alert users when they experience severe or excessive hyperglycemia and provide specific guidance regarding likely causes.

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Duration Of Insulin Action

Issue: Although DIA is designed to measure the glucose-lowering activity of a carb or correction bolus at any time, various clinicians recommend DIA times that vary from 2 to 6 hours or more, despite the fact that interindividual variation in pharmaco-dynamics time is generally less than 25%.

There are also questions about whether pharmaco-dynamic time from GIR studies is equivalent to DIA time?

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ReviewHow Long Do Boluses Lower The BG?

Novolog claims 3 to 5 hours 10, but numerous studies show rapid insulin lowers 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.

10 Novolog product labeling information, October 21, 2005. 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.

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An Accurate DIA Can Prevent Lows

Accurate DIA Time

Accurate BOB

Accurate Boluses Accurate HypoManager

Better Readings, Fewer Lows

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Prevention Prediction

A short DIA time creates significant problems because it hides true BOB level and its glucose-lowering activity. This: Leads to “unexplained” lows

Leads to incorrect adjustments in basal rates, carb factors, and correction factors

Causes user to start ignoring their “smart” pump’s advice

In contrast, an inappropriately long DIA overestimates bolus insulin activity. DIA should be selected, based on its real insulin action time.

Do NOT modify the DIA time to fix a control problem

ReviewShort DIAs Hide Bolus Insulin Activity

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ReviewDuration Of Insulin Action (DIA)

4 hrs 6 hrs2 hrs0

Glu

cose

-lowe

ring

Activ

ity

Accurate bolus estimates require an accurate DIA. DIA times shorter than 4 to 7 hrs will hide BOB and its glucose lowering activity

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ReviewDIA

Large doses (0.3 u/kg = 15 u for 110 lb. person) of “rapid” insulin in 18 non-diabetic, obese people

Med. doses (0.2 u/kg = 10 u for 110 lb. person)

Apidra product handout, Rev. April 2004a

Regular

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ReviewDoes Dose Size Affect Duration Of Action?

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.

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

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ReviewPharmacodynamics Is Not DIA 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 action routinely underestimates insulin’s true duration of action. See next slide.

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ReviewPharmacodynamics Underestimates DIA And Overestimates Impact Of Bolus Size

To measure pharmacodynamics, glucose clamp studies are done in healthy individuals (0.05 to 0.3 u/kg)

Injected insulin ALSO SUPPRESSES normal basal release from the pancreas (grey area in figure)

The basal suppression makes smaller boluses appear to have a shorter DIA

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ReviewPharmacodynamic Time Does Not Equal DIA

After accounting for the lack of basal suppression, True DIA times become longer

than the pharmacodynamic times derived from typical research

At least some of the apparent variation in DIA due to relative bolus size disappears

Some of the apparent inter-individual variation in pharmacodynamics may also disappear

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Standard For:Duration Of Insulin Action

We recommend that a panel of researchers and clinicians who are familiar with insulin pharmacodynamics recommend consistent and safe guidelines for DIA times in pumps for children and adults.

These guidelines will be used to advise clinicians, train pump users, and as a reference on the DIA setting screen in insulin pumps.

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Linear Versus Curvilinear DIA

Issue: The current straight-linear method of measuring DIA is less accurate than curvilinear method for estimation of residual BOB.

DIA times selected in pumps which use a linear method must be shorter to approximate the DIA in a pump that uses a curvilinear method.

Pump manufacturers currently use at least 3 different methods to measure glucose-lowering activity

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Linear And Curvilinear DIA Compared

Set5 hr Linear

5 hr Curvilinear

From Pumping Insulin, 4th ed., adapted fom Mudaliar et al: Diabetes Care, 22: 1501, 1999

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The Modified Triple-Linear DIA

An alternative and more accurate approach would be to modify the linear method into a triple-linear method to provide more precise BOB estimates.

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ExampleTriple-Linear DIA Times

A triple linear line can more closely imitate a curvilinear DIA.

For a 5 hr DIA:30 min – no change3 hrs – fall 75%1.5 hrs – fall last 25%

(approximate values)

5 hr Triple Linear

From Pumping Insulin, 4th ed., adapted fom Mudaliar et al: Diabetes Care, 22: 1501, 1999

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Standard For:Linear Versus Curvilinear DIA

We recommend that insulin pumps use either a 100% curvilinear or a triple-linear method to improve the accuracy of BOB estimates.

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Infusion Sets

Issue: Infusion set design issues and inadequate site preparation training introduce erratic losses of control for a significant number of pump wearers.

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ReviewInfusion Set Failure

Loss of glucose control caused by infusion set failure can occur due unrecognized pullout of the set.

A more common error occurs when Teflon infusion sets come loose and some insulin leaks back to the skin surface. This causes unexplained high readings rather than the complete loss of control typically seen with a complete pullout.

Metal needle sets can also cause occasional bleeding under the skin that interferes with insulin delivery and leads to elevated glucose readings.

Selecting the right infusion set plus good site technique can significantly reduce this unnecessary loss of control.

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ReviewCauses For Infusion Sets Failure

Certain infusion sets are more prone to failure due to their design.

Other sets fail when tugging and pulling on an unanchored infusion line during routine wear loosens the Teflon beneath the skin.

In a review of dozens of pictures of infusion sets online and insulin pump manuals, anchoring of the infusion line is usually not recommended and is not generally done. Anchoring of the infusion line can:

• Stop movement of Teflon catheter under the skin

• Stop “unexplained highs” caused when insulin leaks back to surface

• Reduce skin irritation

• Prevent many pull outs

Example

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ReviewDetection Of Bad Infusion Set Or Site

If a pump user has “unexplained” highs, ask:

How often do unexplained highs happen?

Do they usually correct when you replace your infusion set?

For “yes” answers:

• Always use tape to anchor the infusion line

• Consider changing to a different infusion set

The right infusion set and good site technique prevents headaches and improves the A1c

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ToolInfusion Set Monitor

Insulin pumps with direct BG entry can identify those who may be having consistent but intermittent loss of glucose control secondary to infusion set failure. The pump can: Show avgerage time and interval variation between use

of reservoir loads or the prime function in the pump. Show average BGs for each 12 hour segment following

set changes (indicated by the prime function) over at least the last 7 set changes (or as soon as statistical significance is reached).

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Need For An Infusion Set Monitor

Many pump wearers have random erratic readings that are greatly reduced in number when they change to a different infusion set or start to anchor their infusion lines with tape to stop line tugging.

However, there is currently no tool for clincians or pump users to tell who is having problems with their infusion sets.

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Standards For:Infusion Sets

1. We recommend that infusion sets be expected to perform at least 72 hours without a loss of glucose control.

2. We recommend that monitoring be provided in all insulin pumps to detect consistent patterns of infusion set problems or failure for individual pump users.

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Standards For:Infusion Sets

3. We recommend that insulin pump manuals and training cover methods to identify and prevent infusion set failure.4. We recommend that future infusion set designs incorporate easy to use methods to anchor infusion lines and minimize tugging of the infusion line near the infusion site.

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