Tandem Occlusion Alarms: An Engineering Experiment

I began using the Tandem t:slim X2 insulin pump in December 2016. Since then I don’t think that I have written a blogpost about the pump without mentioning false occlusion alarms. In my first review of the pump, I wrote:

“I have used the Tandem t:slim X2 for almost 10 weeks. In that time I have had 9 occlusion alarms resulting in an immediate stoppage of insulin delivery. The first couple of times I panicked at the shrieking pump alarm fearing that something was actually wrong. Nope. Not once has there been a problem that did not disappear by working my way through the menu screens and pressing “Resume Insulin.” The vast majority of these alarms have been while delivering meal boluses, but not all.”

Periodically I have thought that I have solved the problem and interestingly I have had completely different experiences with my three X2 pumps. Pump #1 got weekly occlusion alarms during the first four months of use. I eliminated the alarms by either using a case or wearing the pump on my waistband with a Nite Ize Clip. But I hated those solutions and eventually went back to carrying my case-less and clip-less pump in my pocket. For no discernible reason the occlusion problem didn’t reoccur and I only had two or three occlusion alarms in the next 11 months. In February 2018 Pump #1 was replaced due to a battery failure. I only used Pump #2 for a month due to a defective T-button. But in that time I did not have a single occlusion alarm.   

Then I got Pump #3 and immediately returned to weekly occlusion alarms and sometimes two or three a week. I figured these alarms were the price of refusing to use a case or clip and I just lived with them. Then a couple of 2-alarm days convinced me that enough is enough. I dug the case out of my supply box. The pump became heavy and large with the case and would no longer would easily fit into the waistband pockets of my workout pants and pajamas. Total PITA. But I didn’t get occlusion alarms. Hating the case, I went back to the Nite Ize clip with the pump on my waistband. And ugh, I started getting occlusion alarms again.

So now my question became: Why does the case eliminate false occlusion alarms? A Tandem tech rep once told me that the case eliminated temperature fluctuations that occurred when I took the pump out of my pocket to enter a bolus. Seemed kind of far-fetched and if that was the case, why doesn’t everyone who carries the pump in their pocket get occlusion alarms? And when I was wearing the pump on my waistband with a clip, why did I get occlusion alarms because there was no temperature change?

My current hope is that the case works because the cut-out over the pump vent holes stops the vents from being blocked during insulin delivery. How could I replicate that without using a case? On Tuesday I went to the nearby Ace Hardware and wandered down the aisle with screws, washers, nuts, springs, etc. I bought a couple of gizmos including black plastic rings with a hole large enough to protect the 6 vent holes on the back of the pump. (It should be mentioned here that there are constant discussions on Facebook about the purpose of these tiny holes and some people swear that they are only for sound. A Tandem tech rep recently told me that the holes are dual-purpose and function both as vents and speaker holes. So that’s what I am choosing to believe.) I also bought 2-sided adhesive strips. 

Working in my kitchen laboratory, I used a hole puncher to cut a perfect-sized hole in the adhesive and then used scissors for the outer circle. Carefully I attached the ring to the pump. Voila! (It wasn’t quite that simple so if my experiment is a success, I will share more detailed instructions.)

It will take a week or two to see if this MacGyver fix works. I started a new cartridge yesterday and I rarely get occlusion alarms until the cartridge measure 80-120 units. If I make it a week without an occlusion alarm, I will have to see what happens with my next cartridge. And then another. 

Diabetes. A science experiment that sometimes requires engineering solutions.

7/26 Late Morning: Unfortunately my science experiment is already a FAILURE with an occlusion alarm during basal delivery this morning. I totally jinxed myself by publishing this blogpost. In defeat I have already taken off the black washer. I spent 45 minutes on the phone with Tandem and the pump passed all of the tests. Of course it would because the pump works fine most of the time. I even changed my cartridges every 3 days for the last week and a half and got 4 alarms within the last 8 days. The issue has been sent to the local rep and I guess I can try to work with him to get a replacement pump. But I am not convinced that a replacement pump will matter. Why do I get these alarms and so many people don’t??? 😩😩😩

*********

Other Comments: I truly believe that false occlusion alarms are related to a design flaw in Tandem pumps. I have so many questions. What percentage of Tandem pumpers experience these alarms? It is hard to tell because social media only attracts those having the problem. Are there common characteristics for those of us getting the alarms such as low TDD of insulin and small boluses? Or is it that certain pumps have overly sensitive occlusion sensors? I could go on and on with questions.

At the same time I want Tandem to succeed. I like almost everything about my t:slim X2 and I appreciate the innovation and good customer service that comes from this company.  There are few pump choices these days and my being on Medicare reduces that number even farther. My primary D-tech loyalty is to Dexcom as my CGM and I am unlikely to return to Medtronic although I was previously happy with my Medtronic pumps. At this time Omnipods are not a good financial option for many of us on Medicare and I have always been fine with a tubed pump. I am intrigued by Bigfoot Biomedical using the Freestyle Libre and keep my fingers crossed that it will be a future option for me. 

I do not follow all of the Tandem rules. Because of my low TDD of insulin, I refuse to change my cartridge every 3 days and throw away more insulin than I use. I change it about once a week while replacing my infusion sets every two days. This was how I operated on Medtronic and Animas and it works for me. With my first X2 I tried changing the cartridge every 3 days a few times and still got occlusion alarms.

I have always had superb customer service from Tandem. Although I am continually frustrated by false occlusion alarms, I do not regret my choice of the Tandem t:slim X2. If I had to choose a new pump today, I would probably choose the X2 again.

But false occlusion alarms are a problem.

*****   Relevant Links   *****

A Review of the Tandem t:slim X2

A 5-month Review of the Tandem t:slim X2

Tandem t:slim X2 and Dexcom G5: It Takes Flexibility

9 thoughts on “Tandem Occlusion Alarms: An Engineering Experiment

  1. Greetings Laddie My experience w occlusions and chats w Tandem folks led me to this process. If I do a touch Bolus while my pump is in a pocket (like u I don’t use a case/clip) — all is fine. If I Bolus using the touch screen – obviously while pump is out of my pocket – all is fine. If I start delivery and put my pump into/out of jeans pocket during delivery, I get a predictable occlusion alarm. If the pocket is in a thin garment (gauze or light *loose* cotton, no problems.

    ABQLaurie Albuquerque NM

    Sent from iPhone 6 – complete with bizarre typos and iOS auto-corrections

    >

  2. I’m hoping to get to an X2 early next year before my Animas support drops off in September-2019 so am watching your experience with the ‘fake’ occlusions.
    My Dexcom rep moved to an X2 about a year ago and has had only one occlusion and she said she caused it by kinking the tube. She has never (yet) experienced what you have noted. I had shared your events with her after our talks in the past.
    Keeping fingers crossed for you.

  3. Oh thanks for the information. Despite being a Medtronic user, I sometimes get folks who ask about Tandem Pumps. It is cool to hear about this.

  4. I use the t:slim x2 with the 90 degree 9mm infusion set and have had it for 2 years. I’ve gotten only 3 occlusion alarms and each time it was due to me bending the tubing and making a kink when I was shoving it into my SPI belt. I keep my pump in the belt 24/7.

    Just sharing in case that helps narrow down the cause!

    • Thanks for sharing your experience, Daytona. I own a Spibelt and a Flipbelt but can’t stand wearing things around my waist. After another occlusion alarm today, I have put my pump in the case clipped on my waistband to see if it really prevents the alarms.

  5. Pingback: Tandem Occlusion Alarms:  Crying Uncle | Test Guess and Go

  6. Pingback: Thank-you Tandem: A Replacement Pump | Test Guess and Go

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