Detailed Evaluate of the MiniMed 670G from Medtronic

The MiniMed 670G from Medtronic is an insulin pump coupled with a glucose sensor.  It makes use of a pc program (known as an “algorithm”) to automate sure facets of insulin supply.  I made a decision to strive the 670G partially out {of professional} curiosity (everyone and their nice aunt have been asking for my opinion on the system), and partially out of private curiosity, as my blood glucose management hasn’t been the best the previous couple of years.

Let me begin out by saying this:

Since I began utilizing 670G, my total blood glucose management is healthier.

I’ve to maintain reminding myself of this non-inconsequential truth, as a result of on daily basis I discover issues about this technique that I don’t notably like.

In my view, the pump itself leaves lots to be desired.  There are such a lot of options and so many menus and so many security/affirmation steps that my button thumb is beginning to type a blister.  The colour display screen is sweet, however not giant sufficient to show every thing it must show.  And the freakin’ clip is the other way up.  The reservoir connector pokes me within the intestine each time I bend over, and I’ve to unclip it to see the display screen and programming menus within the correct orientation.

The “hybrid closed loop” a part of the system (what I choose to name the “semi-automatic function”) is what makes 670G particular.  It features by making changes to the BASAL insulin based mostly on information acquired from the linked glucose sensor.  Since previous-generation Medtronic sensors (Sof-Sensor, Enlite) had been, let’s consider, lower than optimum, I went into this extremely skeptical.  In any case, if the sensor isn’t feeding the pump a gentle stream of dependable information, what’s the purpose?

I’ve been pleasantly stunned by the efficiency of Medtronic’s new Guardian sensor.

In my expertise, the Guardian sensor tends to under-estimate glucose values (typically considerably) and the general accuracy nonetheless falls wanting the Dexcom G5.  And it nonetheless requires three palms and 4 completely different types of tape to safe it to the pores and skin, together with 4 to 6 fingerstick calibrations per day.  However the insertion course of is fast and painless and the transmitter sign virtually by no means misses a beat.  Total, Guardian represents a significant enchancment over Medtronic’s earlier CGM methods.

The algorithm that determines the basal insulin doses makes changes each 5 minutes based mostly on latest sensor glucose measurements, insulin supply and meal (carb) entries.  The algorithm adapts each day based mostly on what occurred over the earlier six days.  So there are each reactive (based mostly on what’s already occurred) and proactive (predicting what is going to occur) elements to the algorithm.

Nonetheless, the algorithm is extremely conservative in nature, doing every thing in its energy to maintain the person far, far-off from something resembling hypoglycemia.  The basal algorithm targets a glucose worth of 120 mg/dl, and there are limits to how lengthy the system can ship zero basal insulin in addition to the magnitude and length of most basal supply.  The utmost fee of basal supply is predicated on a fee that (the system believes) would trigger the glucose to drop beneath 70 if it was to run for about 8 hours constantly.

Consider it this manner:  The max basal in auto mode is kind of like not permitting the captain of the ship to show the rudder too sharply for worry that the ship would possibly sway an excessive amount of.  In fact, when you might have a giant ship and a small rudder, that isn’t prone to occur.  So why the ultra-conservative strategy?  Most probably as a result of regulatory authorities such because the FDA prefer it that means.  Much less danger of hypoglycemia = much less probability for damaging suggestions and authorized points.  However it does make the system much less responsive than it could possibly be.

For individuals who usually have a major distinction between their “peak” basal and their “valley” basal, maybe attributable to a pronounced daybreak phenomenon, the algorithm’s max basal will not be sufficient to satisfy peak basal wants.

By the best way, bolus doses are NOT automated.  Customers should nonetheless enter their carbs into the pump’s bolus wizard calculator in addition to the blood glucose worth.  However the person’s authentic sensitivity (correction issue) and goal settings are NOT utilized.  The system calculates correction doses based mostly on a conservative goal of 150 mg/dl and a sensitivity/correction issue that it determines by itself.

Regardless of these shortcomings, I’m seeing much less total variability (extra time in-range, fewer excessive highs & lows), and my in a single day glucose ranges are extra steady than they’ve been in years.  It’s uncommon that I don’t get up inside an inexpensive vary within the morning.

The in a single day half makes excellent sense.  As a result of the system adjusts the basal supply each time glucose ranges are trending up or down, it is ready to alter the glucose sample over the course of many hours and preserve issues in-range… assuming nothing else interferes.

It jogs my memory of a giant cruise ship.  When the ship is shifting at excessive pace, a small rudder won’t permit it to vary instructions shortly sufficient to keep away from issues like icebergs (that is what occurred to the Titanic).

Not that 670G goes to trigger anybody to crash and sink, however there are similarities when it comes to what it might and can’t do to self-regulate blood glucose ranges.  On lengthy stretches of open water, a giant cruise ship with a small rudder can get you from port to port very successfully.  In the course of the journey, if the ship begins to veer astray, it has sufficient area and time to get again on the right track.

670G does the identical factor:  Over the course of many hours, with nothing affecting glucose ranges apart from the liver’s common glucose manufacturing, the basal insulin may be adjusted to offset delicate ebbs or flows in glucose ranges.  Begin to rise a bit?  The basal supply will increase in order that over the subsequent a number of hours, you’re again on monitor.  Begin to drop a bit?  The reverse takes place.  In consequence, you get up fairly near the system’s set level of 120 mg/dl most mornings.

Right here Come the Icebergs

Everybody who lives with diabetes is aware of in regards to the hour-to-hour, minute-to-minute challenges we should cope with.  These are the icebergs – the issues the system should navigate round in an effort to stop excessive highs and lows.

Basically, something that may trigger a speedy, abrupt rise or fall in glucose ranges represents an iceberg.  Keep in mind, we’re coping with an enormous, fast-moving ship with a small rudder.

The pump’s basal adjustment simply isn’t highly effective or responsive sufficient to forestall excessive and low glucose ranges when confronted with icebergs.

The icebergs embrace:

• Meals (notably rapidly-digesting carbohydrates)
• Bodily exercise (notably heavy train)
• Stress (notably sudden, sudden crises)
• Sudden hormone modifications (ensuing from accidents/trauma, rebounds from lows)
• “Guide” Bolus insulin (from injections or inhaled insulin)

There are additionally a number of limitations to the system which hinder its capability to maintain glucose ranges inside vary constantly:

• Limits to the automated basal adjustment.  As described earlier, the automated basal changes are restricted when it comes to magnitude and length.  The “most basal” is comparatively conservative and might solely run for a most of 4 hours.  The “minimal basal” (zero supply) can solely run for a most of two.5 hours.  Generally, stronger and longer changes are really wanted to realize and preserve in-range glucose ranges, these limits may be… nicely… limiting.

• Sensor reliability.  Even when the system is correctly calibrated, there will likely be occasions when the sensor studies incorrect/inaccurate data to the pump.  And the algorithm is simply nearly as good as the info being fed into it.

• Absorption points.  Simply because a dose of insulin is delivered beneath the pores and skin doesn’t imply that the insulin reaches the bloodstream as anticipated and works as anticipated.  This is applicable to each basal and bolus insulin.  Customers should change websites steadily/frequently, rotate correctly, and troubleshoot successfully.

• Undetected pump issues.   There’s a lengthy checklist of issues that may go fallacious!  Air within the tubing, displaced infusion units, partial occlusions, partially (or utterly) spoiled insulin, leakage, and unintended disconnection simply to call a couple of.

• Instances out of auto mode.  “Auto-mode” is what we name it when the system is robotically adjusting basal insulin based mostly on information fed into it by the glucose sensor.  There are a number of conditions wherein the system will section out of auto-mode.  There’s a transition section known as “secure mode” that initiates below these situations.  Protected mode can run for as much as 90 minutes, with a flat basal supply and no automated adjustment.  If the problems famous beneath aren’t resolved inside 90 minutes, the pump returns to “handbook mode”, which implies that every thing returns to the person’s default settings.

Auto mode is exited if:

• The sensor is in its warm-up section
• The sensor just isn’t speaking with the pump
• The sensor requires calibration
• There’s a vital discrepancy between the sensor and the calibration worth
• “Minimal” basal supply has taken place for two.5 hours
• “Most” basal supply has taken place for 4 hours
• Glucose is above 300 for greater than an hour
• Glucose is above 250 for greater than 3 hours
• An occlusion is detected

Regardless of these “icebergs”, I’ve managed to realize higher glucose management with 670G than I may obtain alone utilizing a pump and non-integrated CGM.

Tying the Captain’s Fingers

To compound among the challenges, Medtronic took away sure instruments that many contemplate important to good self-management.  That is like taking away sources that the captain of that massive, fast-moving cruise ship would usually use to bypass the icebergs.

Listed below are a couple of of the lacking items:

1. Prolonged Bolus. When in “auto mode”, customers not have the choice of extending supply of their boluses. Extending boluses is a great tool when consuming giant parts, slowly-digesting (low-glycemic-index) meals, or meals that take appreciable time to eat.  It’s also important for anybody with impaired digestion (gastroparesis).  Underneath these situations, “regular” boluses will peak too early, leading to hypoglycemia quickly after consuming {followed} by a delayed rise.  Medtronic might have assumed that the 670G’s basal adjustment would stop this drawback, however it doesn’t.  It might cut back the severity of the fall-followed-by-rise sample, however the sample nonetheless exists.  Customers should assume lengthy and arduous about timing their boluses correctly to keep away from the sort of sample.

1. Guide bolus adjustment. Auto mode doesn’t permit customers to regulate bolus doses as soon as they’ve been calculated by the pump, and handbook boluses aren’t an possibility. Planning to train?  Robust cookies.  Take what we are saying.  Sensor reveals a definite rise or fall on the time of the bolus?  Too dangerous.  Take what we are saying.  To change the dose, customers are pressured to “lie” to the system by deliberately getting into incorrect carb quantities or glucose values.

1. Correction doses in “auto mode” are decided by the system, not the person. And the system doesn’t goal a glucose of 120 (as does the basal algorithm); it targets 150.  Why?  Most probably to appease the FDA and get the product to market as quickly as attainable.  The system additionally doesn’t base correction doses on the “sensitivity” or “correction issue” that the person (and their healthcare workforce) might know to work, however on a mystery-clad part of the system’s secret algorithm sauce.  Regardless of all that, as a result of the algorithm sometimes cranks up basal supply previous to the necessity for a correction bolus (for the reason that glucose is rising and elevated), the correction boluses typically overshoots and results in lows.

1. The one allowable adjustment to the basal algorithm is a short lived goal of 150 somewhat than 120. Presumably, that is for train.  Bother is, it takes a few hours for this adjustment to really get the glucose as much as 150 (so it needs to be set a couple of hours prematurely of train), and it isn’t ample to forestall hypoglycemia with longer and extra intense types of bodily exercise.

1. Temp Basal. Consumer-set momentary basal changes aren’t an possibility in “auto mode” for the reason that system adjusts the basal by itself. And there are limits to how a lot (and for a way lengthy) the system will increase/decrease basal supply.  If the person is aware of that their basal wants are going to be considerably larger (or decrease) for a time frame, it is smart to have the ability to inform the system earlier than glucose ranges begin trending out of vary.  For instance, having a high-fat restaurant dinner at all times causes my glucose ranges to rise all through the night time.  I do know that I can quickly increase my basal fee to take care of this, however the 670G doesn’t permit for this sort of enter.  As a substitute, it waits till the glucose ranges begin rising (normally a number of hours after the meal), after which, after 4 hours of delivering what it considers my “maximal basal,” it alarms and shifts out of auto mode and into “secure mode” the place the basal supply is even decrease than what it had been delivering.

A inventive captain can determine methods round day by day challenges.  Customers have the choice of switching out and in of auto-mode in the event that they wish to have entry to issues like temp basal settings, sq./twin boluses, and self-adjustment of bolus doses.  I typically swap out of auto-mode throughout the daytime because of this. One can alter the timing and quantity of boluses doses when delayed meals absorption is anticipated.  Supply may be suspended quickly and carbs may be consumed earlier than/throughout train to maintain from dropping low.

Trusting the 670G system, mixed with some inventive self-management methods, has led to improved glucose administration.

The Supreme Passenger

So who can profit most from 670G?  When functioning correctly, it pushes the person in the direction of glucose values within the 130-160 vary, and A1c’s within the excessive 6s to low 7s.  If this represents a pleasant enchancment for you, then go for it.  If it represents a step backwards, or just isn’t constant together with your private objectives, you then would possibly wish to cross.

Belief me, passengers on this cruise ship don’t get to lie round on lounge chairs and be waited readily available & foot.  This can be a working cruise!  Anticipate to spend a good period of time within the kitchens and engine rooms.  You’ll must handle/preserve each the glucose sensor and the pump.  Plan to carry out fingersticks 4 to eight occasions a day for sensor calibrations and to maintain the auto-mode function working easily.  Anticipate extra alarms and alerts than common.  You’ll must plan well-ahead to forestall lows (and highs, every now and then) when exercising.  And also you’ll nonetheless must handle issues the old style means when out of auto-mode (sometimes 10-20% of the time), and which means ensuring your basal and bolus settings are correctly fine-tuned.

It additionally takes a shrewd captain to navigate this ship.  Utilizing the 670G and its full array of automated supply options requires a substantial amount of coaching, aptitude, and a focus to element.  In comparison with conventional pump remedy (with or with out an unbiased steady glucose monitor), 670G may be fairly advanced.  Coaching sometimes requires three separate periods:  one to be taught the pump, one to be taught the sensor, and one to be taught the automated basal supply system (auto-mode).  One should perceive the entire situations which might be obligatory for auto-mode to activate.  There may be even an “auto-mode readiness” standing display screen that’s 9 objects lengthy!  You’ll must know when/why the system might exit of auto-mode, and easy methods to get again in.  After which there’s “secure mode” – a kind of purgatory between auto-mode and handbook mode wherein the pump is delivering basal insulin however not self-adjusting it till an auto-mode drawback is mounted.  I’m nonetheless making an attempt to wrap my mind round that one.

Individuals who preserve a structured and predictable life-style additionally are likely to succeed with 670G.  There may be a lot much less probability of a cruise ship mishap within the Caribbean than within the Arctic Circle due to the shortage of icebergs.  Somebody whose life consists of frequent/inconsistent meals & snacks, random bodily exercise, altering work shifts, assorted sleep schedules or vital stress goes to battle in auto-mode.   In contrast, those that eat constant/well-spaced meals (with minimal snacks), work out frequently (or by no means) and lead typically relaxed and predictable lives have a tendency to remain in-range more often than not in auto-mode.  And for that matter, these whose basal necessities embrace a vital peak & valley (based mostly on earlier pump use & basal fine-tuning) might battle a bit as a result of restricted basal variations that may happen in auto-mode.  These with comparatively steady basal necessities all through the day & night time usually tend to expertise success in auto-mode.

One different advantage that may’t be understated is PATIENCE.  Don’t anticipate your diabetes worries to fade the second the field arrives from Medtronic.  The corporate is struggling to satisfy sensor provide demand and furnish licensed trainers, so you could have to attend some time to get began.   When you get began on the pump, you’ll possible want to attend for a second spherical of coaching to get arrange on the sensor.  And the system’s algorithm would require a number of days in “handbook mode” earlier than it has sufficient information so that you can swap over to auto-mode (which requires yet one more coaching session).  Even then, the system continues to self-analyze information in an effort to enhance its efficiency, so it would take a number of weeks earlier than it reaches peak efficiency.  Backside line:  affected person folks in the end reap the advantages of the system.

To achieve “auto mode” one should:

• Have conservative glucose administration objectives
• Put in a certain quantity of labor
• Possess some technical aptitude
• Lead a comparatively structured life
• Be affected person when it comes to expectations

Suggestions for Insulin Pump Customers

To get probably the most out of a cruise, it helps to know somebody who is aware of cruises.  They’ll information you on issues like avoiding “inside” cabins (except you take pleasure in claustrophobia), hitting eating places throughout non-peak hours, and snagging poolside lounge chairs early.  Listed below are a couple of insider suggestions that will help you get probably the most from 670G:

• Change the sensors weekly. The Guardian sensors are designed for seven days of use, and also you’ll do nicely by abiding to that.  In contrast to Dexcom sensors (which just about beg to be reused), Guardian sensors typically begin to deteriorate after the primary week of use.  And for the reason that sensor is directing your basal insulin supply, it simply isn’t definitely worth the danger.

• Name in your Medtronic trainers and medical specialists for ongoing help. They’ve insight-a-plenty  to assist reduce the system’s downsides, shorten your studying curve, and in the end extract probably the most attainable profit.

• Common use of 670G has been proven to scale back the frequency and severity of hypoglycemia, however don’t depend on the system to repair your lows as soon as they’ve occurred. Chopping again (or turning off) basal insulin will assist to lift the blood sugar, however it gained’t accomplish that shortly.  It normally takes a couple of hours for this to happen.  By that point, you may get into an accident, have a seizure, or worse.  Use rapid-acting carbs to deal with your lows.  And whenever you deal with your lows, accomplish that conservatively.  Since low blood sugars will normally coincide with a marked discount in basal supply by the pump, you gained’t want as a lot carb as common to convey your lows again as much as regular.

• Take note of the timing of your boluses. Glucose ranges are prone to spike simply as a lot in auto-mode as they do in handbook mode (or with every other system) if the boluses are given too late.  For many meals and snacks, it’s nonetheless essential to bolus 15-20 minutes prematurely.  Nonetheless, with out an prolonged (twin/sq.) bolus possibility, bolusing for slowly-consumed, high-fat or low-glycemic-index meals, the person might want to delay or “cut up” their boluses so as stop a post-meal drop and post-post-meal rise.

• Plan forward when exercising. The one auto-mode function that may assist in any respect is the “momentary goal” of 150.  If you wish to use this, it can must be set no less than 1-2 hours previous to the exercise.  Setting it on the onset of train will do no good because it takes a few hours for basal modifications to affect glucose ranges (keep in mind: massive ship, tiny rudder).  And if you happen to anticipate a delayed drop following your heavier exercises, preserve the momentary goal of 150 in place for a number of hours post-exercise.

• Obtain your information, and work together with your healthcare workforce to research the outcomes. Carelink Private and Carelink Professional will allow you to see the place enhancements are going down and the place changes might wanted.  The 2 variables that you’ve got management over in auto-mode are the carb ratios and lively insulin time.  Carelink studies will allow you to to optimize each of those settings.  For individuals who didn’t fine-tune their basal settings by a collection of fasting checks previous to utilizing 670G, it’s possible that your basal supply will likely be diminished when in auto-mode.  This, in flip, normally implies that carb ratios might want to turn out to be extra aggressive – one thing to look at for.

Points With the Whole Fleet

Curiously, I don’t consider the restrictions inherent to 670G are restricted to this explicit system, though shortcomings to 670Gs algorithm and elimination of sure self-management instruments might amplify the challenges.  ANY hybrid closed-loop system that depends on basal adjustment alone goes to battle to keep away from the day by day icebergs.  My hope is that future iterations of the Medtronic hybrid closed-loop system and people developed by Medtronic’s rivals (Insulet, Tandem, Bigfoot and Beta-Bionics to call a couple of) will supply enhancements resembling:

• Skill for the person to customise how aggressive or conservative the algorithm features
• Permitting the person to implement conventional superior options resembling prolonged bolus supply, momentary basal charges, and the power to override the pump’s bolus calculations
• Simplified and extra logical pump programming, with fewer affirmation steps and overlapping menus
• Improved sensor accuracy with diminished calibration necessities
• Incorporation of faster-acting insulin, resembling Novo Nordisk’s Fiasp. This may primarily improve the dimensions of the ship’s rudder and permit it to do a greater job of avoiding the icebergs

It could be good to have a system that performs nicely in lengthy stretches of open water AND navigates the icebergs deftly, and does so with minimal inconvenience to the person.  Nonetheless, we have now some excellent choices already.  Except you’re a topic below the United Healthcare dictatorship, you might have CHOICES.  You possibly can pursue the 670G instantly, take care of a few of its shortcomings however take pleasure in the benefits of semi-automated supply instantly, and improve to its next-generation (new and improved, to some extent) system in a few years.  Or you’ll be able to go along with one other pump firm, take pleasure in a pump which will have fewer drawbacks, make the most of a separate CGM, and wait a few years for them to catch as much as (or bypass) Medtronic on the hybrid closed-loop entrance.

The 670G represents an vital step in the direction of absolutely automating glucose management.  Nonetheless, you will need to put it within the correct context and set expectations at an acceptable stage.  Regardless of the system’s many limitations, it can enhance the standard of life for many individuals affected by insulin-dependent diabetes.

And that’s saying one thing.