The t:slim Air Bubble Dilemma.

Editor's note: as always, nothing on this site should be taken as medical advice. I am sharing some troubleshooting I've done with my insulin pump and if you'd like to recreate anything you see or learn in this post, please know that you are doing so at your own risk. If you're unsure, contact your insulin pump manufacturer to make sure you aren't going to void your insulin pump warranty with whatever you're wanting to try. I cannot be held liable if you accidentally turn your functioning medical device into a really expensive paperweight. 

I've been noticing a pretty consistent bummer of an issue lately when it comes to pumping with the t:slim:

My pump likes to err when it comes to air.

Little buggers!

It seems that air bubbles (which, according to Tandem's safety information, can compromise insulin delivery) like to gather in the connector area where the "pigtail" - at the end of the couple inches of tubing that comes directly out of the cartridge - and the luer lock of my tubing meet. I've also noticed a bunch of tiny air bubbles (a Tandem rep I spoke with referred to them as "champagne bubbles") that accompany the insulin I'm priming through the tubing with each new cartridge change.

Here's a better look at the "connector bubble" I'm talking about:

Yeeeeah, that can't be good.

I'm not alone, either: a Google search for "tslim air bubbles" pulled up around 7.6 million results, many of them discussions between patients and caregivers about what they've tried and how one might "beat" the air bubble quandary. (Some of the threads on TuDiabetes and within the Facebook t:slim group are notable.)

That Google search also led me to a YouTube video from a fellow pumper named Scott who has some fairly unique ideas on how one might combat air bubbles. I've tried a variation of his method a couple of times and while I'm still getting the hang of it, it does seem promising to me so far. Actually, it's kind of brilliant (and more work than it seems like you should have to do, but if it works...). Scott told me he's relatively new to pumping - he started using his first pump, the t:slim, last November after years of MDI - and applied some of the same principles he knew from multiple daily injections to his t:slim cartridge changes. He's also an engineer by trade, so yeah, that probably helps.

I'm going to reiterate that this video isn't medical advice and isn't the official way to fill a cartridge as recommended by Tandem Diabetes (but for what it's worth, everyone I've talked to at Tandem seems to be open to the possibilities of other ways of doing things, as long as they don't harm the pump). If you're going to try this, do so at your own risk. (And thank you again, Scott, for letting me share your video!)




I realize that having to bang the side of an insulin cartridge with a Swiss Army knife (is that what he uses?) isn't an ideal solution, but sometimes you have to improvise. (I actually use the old cartridge as my "hammer" of choice, but you do you.) The two key things here for me are the angle at which you're holding the cartridge when pulling the air bubbles out, and the whole in-out-in thing you're doing with the syringe.

At the same time that I started trying out some of these techniques, I also reached out to Tandem Diabetes (makers of the t:slim) to see what their take is. They said they're aware of the air bubble that tends to appear at the connector - the rep even commented that she sees them too, in her demo pump. We ran through all of the normal troubleshooting bullet points - is the insulin room temperature when you're filling with it, are you keeping the pump pigtail-side up when filling and priming, are you making sure there are no air bubbles in the filled syringe (for the record, I don't think I've ever been able to get every air bubble out of a filled syringe - it's just the nature of the beast - but I am usually able to flick the side of the upside-down syringe enough that they all collect towards the plunger, and I stop just short when filling the cartridge so that these bubbles stay in the syringe) are you making sure the luer lock is tightened all the way, etc.

One idea that a Tandem rep gave me and I've tried with success is: when priming the tubing, don't connect the tubing to the pigtail before the fill starts. The pump requires you to prime a minimum of 10 units each time, so what you can do is prime most of your air bubbles out before you attach the tubing. (The thinking here is that a 3 inch piece of tubing is a lot less space for air bubbles to escape through, than through 20 inches or more.) Once you've hit the 10u mark - or if you're feeling especially dexterous, you can just do this part once you see insulin at the top of the pigtail and all of the bubbles have escaped, and the pump is still priming - attach your tubing and continue to prime.

It seems like some combination of these processes might work best for me, and I plan to keep experimenting. If you're using a t:slim - what have you tried? Are you getting the same air bubbles I am, and if so, what are you doing to avoid them?