Medtronic’s new 530G Insulin Pump with Enlite CGM represents the first step towards closed loop technology.  530G is the first pump/CGM combination that acts upon a glucose value automatically, without the user’s intervention.   To see if the system is all it’s cracked up to be, we had our Director of Patient Care & Education (Lisa Foster, MSN, RN, CDE) and our Director of Lifestyle & Nutrition Services (Jennifer Smith, RD, LD, CDE) – both experienced pump/CGM users and trainers – wear 530G for several weeks and offer their candid feedback.  Here’s what they had to say.

Jenny’s Take

My “N of 1” experience

All experiences are personal. When reviewing a product I always keep this in mind since things can vary widely based on expectations and past experience.

Recently, I had the opportunity to trial the Medtronic 530G and Enlite sensor system.   To start on a positive note I’ll start with my list of likes!

Pros to the CGM:

Having tried the Medtronic Sof-Sensor in the past I can definitely say the insertion of the Enlite is so much easier.  There is no longer the need to set the insertion device at the proper angle to get the sensor inserted “correctly”. The insertion device makes it easy for anyone to use. The buttons that deliver the sensor below the skin are easy to push, even for those who may have dexterity issues, arthritis, etc. The directions to use the inserter device are easy to understand and don’t need an interpreter to follow!

Once inserted, it’s easy to attach the transmitter and the new adhesive tape that holds the transmitter down works nicely to keep it in place. The old system required a lot of adhesive tape over the transmitter to keep it secure on the body.

Pros to the 530G pump:

I have worn older models of the Medtronic pump.  I really like the menu-driven format.  It’s easy to navigate and it’s also quite easy to use the sensor with the pump. I also like the ability to turn off the automatic calibration so that I have the ability to calibrate at just the right time, or per my preference.  I really like having the ability to set various carb ratios that are in increments of whole numbers (such as 6.5g per unit) – although I didn’t use this, I can see its value for different times in life (teen years, pregnancy, insulin resistance, etc.).  The pump is easy to use, set up and has very user friendly language rather than clinical jargon that some who are new to pumping may not understand as easily right away.

With positive notes, there are always sour grapes features too. I think these are more from a personal standpoint honestly.  Everyone has different experiences and I certainly have a lot of friends who really love all features of their system as an all-in-one package (pump and CGM).

Cons to the CGM:

Personally, I did not have a very good experience with the sensor. I have worn several sensors systems since 2006 – having started out with what I consider the best which is no longer on the market (Navigator….so sad!). I transitioned to the Dexcom Seven Plus and finally to the current Dexcom G4. I did a true test of the Enlite sensor – comparing it to results I was getting at the same time while wearing the G4 sensor too (I love to be a guinea pig). Honestly – there was no comparison for me. The Enlite was very off – one day telling me that I was in the 40’s for several hours straight! Fingerstick after fingerstick as well as my G4 told me otherwise – which of course was frustrating to keep getting alerted to a false low.  The sensor then transitioned into readings that really would have convinced me that I was truly cured of diabetes. I in fact tried to get a rise out of the system by eating something I knew full well would raise my BG fast – mmmm Orange juice! My G4 gave me the quick reply that my BG was rising, yet the Enlite just kept plugging along telling me I was in target with no variance at all.  The sensors did finally come into a closer range of what my glucose was by the end their 6-day life, but it still didn’t compare or keep up with the changes in my glucose as well as my G4 system… and it wouldn’t have compared at all to my Navigator!

Cons to the pump:

As a note, I have to say this is really not specific to the Medtronic pump, but to tubed pumps in general. Having worn my Omnipod pump for many years already (since 2005), I’ve become very accustomed to no tubes. I also have a toddler – a 16 month old little boy, who is curious about everything.  I’ve found it quite easy to “hide” my pod as there is no tubing for him to see or pull and I’m not connected to the pump that has to be pulled out every time I want to bolus. I also found it a hassle to pull the pump out every time I wanted to check the CGM screen. In the past when I wore a tubed pump, I often kept it hidden in the middle of my chest clipped to my bra or under my armpit clipped to the inside of my bra. Having the CGM on the pump meant I had to have access to the face of the pump and thus I found it cumbersome to find a place to keep it secure, yet out of the reach/view of my curious little boy…especially the tubing.

Having access to preset carb values for foods I commonly eat has been a wonderful time saver with my Omnipod.  I didn’t have this feature on the Medtronic pump.   And to see my daily history including the tags I added to note exercise/illness, etc. I have to download the pump – and I don’t always have time to do this.  Having this feature on my Omnipod allows me to “check-up” on myself more often and spot trends at specific times of day (like the fact that I’ve been higher after lunch since I started working from home!).

If I didn’t have access to Omnipod, I’d likely use the Medtronic pump since it is a great pump. I would be sad to give up my Dexcom G4, and I can say that personally I wouldn’t choose to use the Medtronic sensor. Everyone has their N of 1 experience and this is mine. I know for a fact that most people who wear a pump are very happy with their product of choice – and it’s wonderful that we have so many options available!

Lisa’s Take

I really, really love my Medtronic pump.  A lot.  And if it disappeared from the marketplace, I’d have a really hard time picking a substitute.  Carelink is such a user-friendly program for patients as well as for clinicians.  So when the old Sof-Sensor was replaced by Enlite, I was really eager to try it.  I love having CGM and pump data integrated into one device and one set of reports.

I used to wear a Sof-Sensor, and I struggled with it.  There were so many times that it woke me (and my husband) up in the middle of the night, alarming that my BG was low.  I’d get up and check a BG, and it would be perfectly fine.  I’d recalibrate and go back to bed, only to be disturbed again and again.  Eventually, I just started sleeping through the alarms because they became meaningless to me, and I would simply cancel them out in my sleep without even looking at the screen.  Kind of defeated the purpose of having a CGM.

So when the 530G launched, I was really eager to give it a try.  I learned as much as I could about how to get the best performance from the new system—how to tape it in place, where to place it, when to calibrate, when not to calibrate, how to avoid getting a calibration error, paying attention to the interstitial signal in making calibration decisions, how to get an off-track sensor back on track…I have a lot of tricks up my sleeve.

My first impression was that the insertion process was much improved compared to the old Sof-Senors.  I started the sensor first thing in the morning so that I would have plenty of time to get some good calibrations under my belt before bedtime.  Despite my efforts, it woke me up several times during the night telling me that my BG was in the 40s, but it was not.  I recalibrated a couple more times but I just couldn’t get it on track, so I gave up and shut off the CGM so I could get some sleep.  I was tired the following day from my sleep being so fragmented.  And I had to go through the two hour warm up again.  Because I’d slept through alarms, the “thresh suspend” (the pump’s automatic basal shutoff when a low is detected by the sensor) had been activated during the night, and I woke up higher than usual because of the two hours of missed basal insulin.  This was not the experience I’d hoped for.

The next night I decided that sleep is too precious to sacrifice, so I chose to shut off the thresh suspend and the glucose alerts.  I got sleep, and the sensor did track better.  But at that point there was no real reason to be wearing the system, either.  So I turned it back on the following night.

In general, I found that once I got through the inaccuracies of the first 24 hours, things were better.  I still had nights where my sleep was interrupted because the sensor was underestimating my BG, though.   Most of the time my Dexcom ran closer to the fingerstick results, but sometimes the 530G came out ahead.  Several times I noticed that although I had set the same parameters into both CGM systems, I’d get arrows up or down on the 530G whereas the G4 showed that my BG was reasonably steady.  After the fact, I’d compare the trend tracings, and they’d look basically the same.  Once the 530G alerted me that I was double arrows down, but the G4 did not.  And I could feel that I was dropping fast.  I watched both sensors like a hawk.  I decided that I’d have to take glucose gel if I got down to 100, and both sensors leveled out just in time.  I was glad I’d waited and saved myself the hassle of going high again.

Following the first several days of wear, I was at a conference with other CDEs.  I was getting ready to eat dinner when I saw that the iSig had dropped really low.  Although my BG was 92 mg/dl, I was afraid to calibrate because the cal factor was out of range and I didn’t want to get a cal error message.  I consulted with my colleagues, and we decided that since the 12 hours was almost up, I had nothing to lose, so I calibrated.  And I didn’t get the cal error that I’d expected, so I was happy.  Then the iSig perked up considerably.  The next evening, though, it dropped again, and I was struggling with inaccuracies.  After consulting yet again with my cronies at dinner, we decided that the likely problem was that the sensor must have coiled, and I’d have to pull it.  So I did.  The filament was not at all coiled! So I was mad at myself for pulling the sensor before my 6 days were up.  Live and learn.

Technology is always changing and improving.  I have a lot of hope that going forward, the technology will keep getting better and better.  And I’m grateful that I get to pick which system I want to use… working with patients across the country and around the world, where choices are not always available, I’ve come to realize how lucky I really am.