More on Medtronic Insulin Pumps & Continuous Glucose Monitors (CGM)

Each insulin pump and continuous glucose monitor (CGM) offers its own distinct features – how do you choose the best one? The key is identifying which system has the key features that meet your family’s needs, while minimizing your personal deal-breakers. To help you make this choice, here we outline the unique features that might make the MinimedTM 670G* Insulin Pump / CGM System (released in Canada in December, 2018) or other Medtronic systems a great match for your diabetes management needs.

Medtronic Canada offers three separate insulin pump and/or CGM systems right now:

  1. Minimed™670GHybrid Closed-Loop Insulin Pump/CGM System (released in Canada in December, 2018), with some automatic insulin adjustment features for both highs and lows.
  2. Minimed™ 630G Insulin Pump/CGM (released in Canada in April, 2017), an integrated system which shuts of basal insulin delivery automatically when your glucose reading is low.
  3. Guardian™ Connect CGM, a stand-alone glucose monitoring system.
For a side-by-side comparison of these 3 systems, plus those by other manufacturers:

Comparing Insulin Pumps Available in Canada

Comparing Continuous and Flash Glucose Monitors Available in Canada

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Key Features of Medtronic Pump/CGM systems:

  • If you’re looking for an insulin pump system with integrated Continuous Glucose Monitor (CGM), both the Minimed 670G and 630G fit the bill.

What do we mean by “integrated”? The two parts – pump and CGM – work together within a single system: you can see your glucose data on the pump screen; the CGM communicates glucose data to the pump, pre-populating the bolus function so that you don’t have to manually enter your reading to correct a high.

    The 670G and 630G represent two of the three integrated pump/CGM systems currently available here in Canada. (Tandem t:slim with Dexcom G5 is the third.)

    If you’re looking for glucose monitoring options that are independent of a particular insulin pump, then consider the stand-alone Guardian Connect CGM system, which gives you the freedom to use it without a pump, or independently alongside any pump. (You may also want to include in your research the other stand-alone glucose monitoring systems currently available in Canada: Dexcom G5 Continuous Glucose Monitor; Freestyle Libre Flash Glucose Monitor.)

     
    • If you’re pump-shopping for a child under 7 years old or for someone with type 2 diabetes, or if your Total Daily Dose of insulin is less than 8 units, then the 670G is not for you. It has been approved by Health Canada for individuals age 7+ with type 1 diabetes. In this case, consider the 630G or the Guardian Connect.
    • If you’re looking for a pump that will stop basal insulin delivery when glucose is low, both the 670G and 630G have a feature called Suspend on Low which will do just that. When glucose drops below a set threshold, the system alerts you; if you do not acknowledge that Low Alert with a button press, it will suspend basal insulin delivery, giving your glucose time to rise. So if you are asleep during a hypoglycemic episode, or if you are awake but are unable to respond (experiencing a severe low blood sugar, for example) then you will not continue to receive insulin which would compound the low. When basal insulin delivery will automatically resume depends on the particular model: 630G will automatically resume after 2 hours; 670G will automatically resume when glucose rises.

    At first glance an interruption in basal insulin delivery may not seem like a good idea, as it tends to lead to high glucose a few hours later. However, when a user may not otherwise be able to deal with the low, the benefits may outweigh the drawbacks.

    • If you’re looking for automatic insulin adjustment for both lows and highs, then you’re looking for the 670G. It’s the only hybrid closed-loop (self-adjusting) insulin pump system currently available in Canada.

    (The Tandem t:slim insulin pump with Dexcom G6 CGM, which also has some automatic insulin adjustment features, is available in the USA, but not yet in Canada.)

    What does “Hybrid Closed Loop” mean? In short, the pump and CGM portions of the system are not just “integrated”, but the pump actually reacts to the information communicated from the CGM: in AUTO mode, the pump automatically adjusts your basal (background) insulin – up or down – every 5 minutes based on the glucose readings from the CGM. When glucose rises, background insulin is increased; when glucose drops, background insulin is decreased as needed. The goal is to increase your time in-target so that both lows and highs are reduced, through the day and night. (Sleep-deprived parents, take heart!)

    Why “Hybrid”? This term refers to the fact that the system is not fully automated. In a true closed loop system you would “set it and forget it”, and the system would take action with minimal user input. In a hybrid closed-loop system, however, user input is still required: For example, for meals you need to check glucose, enter the carb amount in the food you are about to eat, and then accept the bolus recommendation as calculated by the system.

    Note that automatic insulin adjustment does not include bolus insulin – the insulin dose that you deliver for food or to correct an existing high will NOT be adjusted automatically by the pump.

    Also be aware that auto basal adjustment will not eliminate lows (or highs) entirely – all the usual culprits (exercise, too much insulin, inaccurate carb-counting, stress, etc) may impact blood glucose more, or more quickly, than a change in basal insulin is able to cover.

    • All 3 systems include the Low Alert and High Alert features common to all CGM systems (called Alert on Low or Alert on High by Medtronic).
    • If you want a bit more of a heads up when you might be headed for a low, then you’ll may be interested in the predictive features:
      • Alert Before Low / Alert Before High notifies you when the system predicts that glucose will go low (or high) within the next 30 minutes (for the 630G and 670G) or within the next hour (for the Guardian Connect). With the 670G, insulin will be adjusted automatically to try to avoid the low (see the next point, Suspend Before Low); with the 630G and Guardian Connect, the advanced notice gives you a chance to take action to potentially avoid the low (by eating extra carbs or manually changing insulin delivery).
      • Suspend Before Low (670G only) takes this “heads up” one step further by stopping basal insulin up to 30 minutes before reaching your preset low limit, then automatically restarting it when your glucose levels recover. The goal of the Suspend Before Low feature is to help avoid lows and rebound highs.
    • Of the 3 systems, the 670G gives you the most flexibility in how you manage diabetes. Think of it as having 3 systems in one: you can use it in full auto mode, where insulin is automatically adjusted for both highs and lows (it’s the full Auto Mode as described above that sets the 670G apart from other insulin pump/CGM systems); you can turn off the automation and run the system essentially as a 630G with a few added features (Suspend Before Low, for example); or you can use it in manual mode (as a basic insulin pump without automation, giving you control over adjusting insulin and reacting to highs and lows). This manual mode is useful if you don’t want to use CGM full-time.

    Tips from the Trenches

    Our son only uses CGM part-time, to give us insight into glucose trends and to tweak insulin doses periodically; he doesn’t use it full-time because he has relatively little “real estate” and because we get Alert Fatigue when he wears CGM. Other families only use CGM intermittently to manage the cost of sensors. Sometimes pumpers just want to reduce the tech burden by taking a break from their CGM. In all of these cases, you could still use the 670G, but you wouldn’t have access to the glucose alerts or automatic insulin adjustment. ~Michelle

    • The 670G also seems to require a fair amount of user input to take advantage of the automated features. For example, if your glucose reading rises above 13 mmol/L for a period of time, the 670G will require you to input the result of a fingerstick BG check; if you don’t enter one, the system will shut off automated features, reverting back to a manual pump. This may result in more fingerstick checks than with other integrated pump/CGM systems.

    In addition, the 670G is missing some key features that some pumpers have come to rely on (like Extended Bolus and Temp Basal). The automatic insulin adjustment is designed to eliminate the need for these features, but the conservative algorithm may not be sensitive enough to accommodate for exercise, slow-digesting foods or high fat foods that traditionally require an extended bolus or temporary basal rate.

    Our family has not taken the 670G for a test drive, so I can’t speak from firsthand experience, but I encourage you to check out the commentary provided by Gary Scheiner in his review of (the US version of) the 670G.

    • The 670G CGM and Guardian Connect CGM both use a new and improved sensor, Guardian Sensor (3), to detect the glucose levels in the interstitial fluid at the sensor site. The Medtronic website notes that: “The Guardian Sensor (3) glucose values are not intended to be used directly for making therapy adjustments, but rather to provide an indication of when a fingerstick may be required.” This sensor has an overall Mean Relative Difference (MARD*) of 11.2% for Adolescents and 10.0% for Adults1 across all blood glucose levels. (See Note at the bottom of this page for accuracy measures broken down by glucose level, and by day vs. night.)

    Each Guardian Sensor (3) is approved for up to 7 consecutive days of use.

    The 630G CGM uses a previous version, the enhanced Second Generation Enlite® Sensor, which the company reports has an overall Mean Relative Difference (MARD) of 13.0%2, 3.

    Each Enlite sensor is approved for up to 6 consecutive days of use.

    For a side-by-side accuracy comparison of all systems:

    Comparing Continuous and Flash Glucose Monitors Available in Canada

    Fingerstick calibration twice each day is recommended for Medtronic CGM systems.

    *MARD = Mean Absolute Relative Difference, a measure of error (as an average %). MARD represents the difference between the patient’s CGM readings and the glucose values obtained from a lab analyzer. A lower value means values are closer to the lab reference value; that is, the sensor is more accurate than one with higher MARD values.

    • The 670G focuses on Time In Range as the main metric; more successful management is indicated by more of your readings falling within the upper and lower ends of your glucose goals (between 4 and 7 mmol/L, as one example). The company reports an average of 2% Time in Range within a controlled clinical trial environment4, and 70.7% Time in Range when the 670G system is used in the real world5… that’s amazing!

    To temper our excitement to a reasonable amount, we need to remember that the validity of Time In Range – or any other metric – as a measure of how effectively glucose is being managed depends on the accuracy of the system; in this case, on the accuracy of the CGM sensor.

    Let me illustrate with a hypothetical example:

    If the data generated from my d-device says that my glucose is between 4 and 7 mmol/L 100% of the time, but the d-device is wrong 50% of the time, then I’m actually only in-range 50% of the time (not 100%, like the system says).

    This is an extreme example, as no system will say you’re in-range 100% of the time, and accuracy rates for glucose monitoring systems (from CGM to Flash to BG meters) are typically below 15% (much more accurate than 50%). However, the point remains that accuracy must be considered when interpreting glucose data from any diabetes technology.

    • The 630G uses the “Guardian” CGM transmitter, and the 670G uses the newer Guardian Link 3 Transmitter, both of which have significant internal data storage: the transmitter itself stores up to 10 hours of glucose data.

    What this means for real life is that if you disconnect from your pump to go swimming, or you leave the pump in the locker room for an hour while you work out, or you take a 9-hour flight across the Atlantic and put the pump in airplane mode for the entire flight… at end of the swim, workout or flight, all of the data is transferred from the transmitter to the receiver, without a gap in data. (Note that if you have disconnected for less than 6 hours, the transmitter and receiver will automatically reconnect; if it’s been longer than that you’ll need to manually reconnect them.)

    • All three Medtronic systems provide the glucose trend information common to all CGM systems. Up or down arrows tell you if your child’s glucose is rising or falling, and how fast; horizontal arrows tell you that glucose is steady (not changing significantly).
      • The Medtronic CGM systems are unique in that they display three levels (rather than two levels) of glucose rate of change arrows:

      ↓      Single arrow down means that glucose is falling at a rate of 1-2 mmol/L over 20 mins

      ↓↓    Double arrow down means that glucose is falling at a rate of 2-3 mmol/L over 20 mins

      ↓↓↓  Triple arrow down means that glucose is falling at a rate of over 3 mmol/L over 20 mins

      (The same three levels of up-arrows exist to show rising glucose.)

      This glucose trend information allows you take action based on how your child’s glucose is changing – and how fast it’s changing. After all, 7.0 mmol/L with ↓ is quite different from 7.0 mmol/L with ↓↓↓!

      • Both the 630G and 670G pumps (which also act as the CGM receiver) are fully water-proof [IPX8 rating = waterproof when submerged up to 3.6m (12 ft.) for up to 24 hours].

      The CGM transmitter (which is attached to the sensor and worn on your belly, buttocks, arm, etc) has a different rating than the pump body/CGM receiver; it’s waterproof up to 2.4 meters (8 feet) for up to 30 minutes.

      • If you want to use your smartphone as the receiver, the Guardian Connect takes sensor glucose readings every 5 minutes, and uses smart technology to predict when you’re going too high or low, sending the notification to your phone.
      • If Remote Viewing of your child’s CGM data is a deal-breaker for you, then your search is narrowed down to just one Medtronic system: the stand-alone Guardian Connect, which offers an interface for up to 5 users via a compatible smartphone. You can stay connected to your loved ones with the CareLink™ Connect platform, which includes anytime access to glucose data, as well as automated text message alerts.

       (The only other system currently available in Canada that allows for remote viewing of CGM data is the Dexcom G5 Mobile, available as either a stand-alone or integrated system.)

      • Both the 630G and 670G systems include a linked Contour®Next blood glucose meter, which sends glucose readings wirelessly to the insulin pump, saving time and effort, as well as eliminating manual data entry errors.

      The meter can also be used as a remote to deliver a manual bolus, or one out of 8 preset bolus amounts (in units of insulin). So if your child has the same snack at school every day, she can simply select that preset program to deliver the correct amount of insulin for that snack. Or if you’re in the drive-through at Tim Horton’s with your child strapped in the car seat in the back, you can use the remote from the front seat to deliver the preset amount that corresponds to a Vanilla Dip.

      (If you’re looking for a remote that gives you the flexibility to deliver any bolus size on the fly, this linked BG meter doesn’t qualify – you can only deliver one of eight preset bolus sizes. If you’re looking for a remote that includes a bolus calculator, so that you can enter the amount of carbs and let the remote calculate and deliver the correct amount of insulin, again this meter won’t fit the bill; the linked BG meter does not include Bolus Wizard, which can only be accessed on the pump itself.)

      • Large capacity insulin reservoir holds up to 300 units of insulin.

      Tips from the Trenches

      When purchasing a pump for a 10 year old you cannot imagine needing more than 180 units over three days but by the time the warranty is up on the pump your 10-year-old is now 14, the size of a grown man and in the throes of puberty, using 100+ units of insulin a day.  The 300 unit reservoir was invaluable for our family when our son’s insulin needs increased dramatically!  Even before this happens, you do not have to fill the reservoirs – just put enough insulin in for three days and enough extra for priming out any air bubbles.
      -Jacky, mom of a 13-year-old boy with type 1 diabetes

      • 630G and 670G insulin pumps are fully operational on their own via buttons on the pump body itself. This means if you misplace or forget your linked meter, or if you don’t want your child to have a smartphone, you can still access all the functions of the pump and CGM.
        • (A smartphone is required to act as the receiver for the Guardian Connect system.)

        • Because of the venting mechanism, tubing-to-reservoir connections are proprietary– if you have a Medtronic pump, you must use Medtronic infusion sets. According to the company, venting is used to maintain the proper pressurized environment for the pump mechanisms; this venting mechanism is built directly into the infusion set connection, so new venting is provided with each set change to help maintain the reliability of insulin delivery.

        If it’s important to you to have the flexibility of using infusion sets from other manufacturers (i.e. those with a Luer-lock connection), then a Medtronic system may not be a good fit for you.

        • 4 year warranty period on the insulin pump/CGM receiver (plus up to 1 additional year under Medtronic’s Continuation of Therapy program, if insurance coverage will not allow you to replace the pump at 4 years – contact Medtronic for details).

        5-year warranty for pumps obtained through a provincial insulin pump funding program, where a new pump is covered only every 5 years.

        1 year warranty on the CGM transmitter.

        For an overview of all the features of the available pumps and glucose monitors:

        Insulin Pump Comparison Chart

        Continuous and Flash Glucose Monitor Comparison Chart

        Note on Sensor Accuracy:

        Comparing venous samples (i-STAT) and sensor glucose (SG) for the Guardian Sensor 3 (used by the Minimed 670G CGM).

        [From Garg, S. K., et al (2017). See References below for the full citation.]

        Time in Range:

        Adults:

        Proportion of in-target glucose values during the hotel stay (controlled clinical trial environment): 74.2% (– 17.5%) for i-STAT venous samples; 76.9% (– 8.3%) for SG measurements, both of which were relatively comparable to the…

        Proportion of adult in-target SG values during the entire in-home study at 73.8% (– 8.4%).

        Adolescents:

        Proportion of in-target glucose values during the hotel stay: 67.4% (–Standard Deviation (SD) of 27.7%) when assessed by i-STAT venous samples; 72.0% (– SD 11.6%) for SG measurements.

        Proportion of adolescent in-target SG values during the entire in-home study: 67.2% (– 8.2%).

        The lower percent of in-target values observed in adolescents relative to adults is not unexpected and likely due to higher activity levels and eating.

        Sensor Accuracy (as measured by the MARD– SD between SG and i-STAT venous blood glucose values) during the hotel stay:

        Overall sensor accuracy:

        11.2% (– 9.7%) for adolescents;

        10.0% (– 8.7%) for adults

        Sensor accuracy within the target range (71–180 mg/dL =~3.9–10.0 mmol/L):

        10.5% (– 9.7%) for adolescents;

        9.6% (– 8.3%) for adults.

        Sensor accuracy in the High Glucose range (>180 mg/dL = >~10.0 mmol/L):

        12.8% (– 9.1%) for adolescents;

        10.3% (– 7.8%) for adults.

        Sensor accuracy in the Low Glucose range (<70 mg/dL = <~3.9 mmol/L):

        12.3 (– 9.2 mg/dL) for adolescents;

        12.2 (– 10.6 mg/dL) for adults.

        By time of day:

        Overall daytime (from 7:00 a.m. to 10:00 p.m.) MARD: 10.4% (– 9.7%).

        Overall night-time (between 10:00 p.m. and 7:00 a.m.) MARD: 10.2% (– 8.3%).

        References

        1. Garg, S. K., Weinzimer, S. A., Tamborlane, W. V., Buckingham, B. A., Bode, B. W., Bailey, T. S., Brazg, R. L., Ilany, J., Slover, R. H., Anderson, S. M., Bergenstal, R. M., Grosman, B., Roy, A., Cordero, T. L., Shin, J., Lee, S. W., … Kaufman, F. R. (2017). Glucose Outcomes with the In-Home Use of a Hybrid Closed-Loop Insulin Delivery System in Adolescents and Adults with Type 1 Diabetes. Diabetes technology & therapeutics, 19(3), 155-163.
        2. Veeze HJ. et al Poster 136 ISPAD 2014 : Real-life performance evaluation of the New Generation Enlite™ glucose sensor in patients with Diabetes Mellitus.
        3. Enlite™ Sensor Performance Addendum, Paradigm® Veo™ Algorithm, True Alert Rate for Predicative and Threshold for 3.89 mmol/L @ 30 minutes; CLSI Guidelines, Method 2.
        4. Bergenstal R, Garg S, Weinzimer S, et al. Safety of a hybrid closed-loop insulin delivery system in patients with type 1 diabetes. JAMA. 2016;316(13):1407–1408. Actual results are based on clinical trial. Time in range results reported in pivotal trial were measured from 71-180 mg/dL (3.9-10.0 mmol/L).
        5. Agrawal, Pratik & Stone, Michael & Gopalakrishnan, Shweta & Fogel, Catherine & W. Lee, Scott & R. Kaufman, Francine. (2018). Real-World Data from the MiniMed ™ 670G System Commercial Launch. Diabetes Jul 2018, 67 (Supplement 1) 960-P; DOI: 10.2337/db18-960-P.

        Minimed 670G Support: https://www.medtronic.com/ca-en/diabetes/home/support/670G-support.html

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        This material has been developed from sources that we believe are accurate, however, as the field of medicine (in particular as it applies to diabetes) is rapidly evolving, the information should not be relied upon, as it is designed for informational purposes only. It should not be used in place of medical advice, instruction and/or treatment. If you have specific questions, please consult your doctor or appropriate health care professional.