Tandem Mobi Cartridge Bubbles

Type 1 and LADA
1

I am not new to pumps, but am new to the Mobi. I keep getting bubbles in the cartridge after change is complete. I admit it is the most challenging to fill I have ever experienced. I do the fill slowly, and work the bubbles out as I go. Later I discover a bubble. Apparently air gets into the cartridge when it is disconnected. I am experimenting with unscrewing the cannula rather than removing the clip.

If you have resolved this issue I am interested in learning how. Thank you so much.

2

Assuming you mean unscrewing the tubing (the cannula is inside your body, I think) that sounds like a way to introduce air into the tubing…and why do it?
Don’t know how you’d get air in the cartridge. You’re sure it’s air, not just a reflection in the mobi’s transparent cartridges?

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3

I don’t think air gets in later. I think it’s just the little champagne bubbles settling out. The cartridge is also difficult to flick to move any bubbles. I haven’t personally seen this issue, but admittedly I’m OCD about stuff like this, and I know others have reported similar issues.

Some of the things I do to avoid the bubbles:

  1. Room temp insulin. Cold insulin has long been known to make more bubbles.
  2. Make sure the cartridge/vial are positioned like in the instructions when you plug them together, with insulin vial on the bottom and cartridge above it. If you flip the apparatus the other way over, you bubble air through the insulin.
  3. After the cartridge is full, but still attached to the vial, I tap the plunger stick thingy against the table. It’s the most effective means of “flicking the syringe” I’ve found to force any bubbles up to the top.
  4. Then you have to expel more than just the bubbles back into the vial. There’s a couple inches of tubing you’ve got to push the bubbles past.
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4

You were getting bubbles in the tslim too you just couldn’t see them.
I agree using room temp insulin helps. Also make sure you inject air into the insulin vial then draw up the insulin. And push half back and draw it again. If I’m using long tubing I will then push through the tubing to fill it manually then I re fill the syringe. This way you can start with a full cartridge. I use only 150 in 3 days but I like to have extra.
If you hold the cartridge up while you fill the tubing, the tiny bubbles will be pushed out.

You could also try filling the cartridge and leaving it sit for a day before using it. Knock off bubbles before starting it. Those tiny bubbles will come together and this way you avoid the issue.

And lastly, I wear my mobi on my skin using double sided wig tape. I keep it so any air bubble would be trapped at the back end and won’t even find its way into the tubing. I know most people don’t wear it like this, but it works nicely for me. When my 3 days are up, I still have some insulin in there so no way would I be pushing that bubble through.

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5

Thank you for that response. I woke up in the middle of the night last night with my BS headed to 400. I know when I put the cartridge in service there were no bubbles. The only answer is; does air get in when I disconnect? The bubble was so large, there is no way I could have missed it when it was installed. The bubble came after the fact.

I do everything you suggested in your first paragraph. I will try what your second paragraph recommends.

I tried to find a double sided tape to use with my Mobi. I will try wig tape. I do not like the sleeve, too big and too thick. Would you tell me which one you use?

Thank you.

6

I normally unclip the connector at the infusion set before taking shower. I notice that one reasonable size bubble in the cartridge in one occasion for unknown reason. I just place the tube on top of the cartridge, ensure the bubble at the tube entrance, press the pump button to push the bubble out (follow instructions to change cartridge, then fill tube). It worked. From then on, I always inspect the cartridge and tube system for any sign of bubble and pump them out before reconnecting to the infusion set.

It is difficult for ambient air entering the needle tip at the clip when the tube is liquid (insulin) filled. The bubble is most likely generated from heat absorbed by the liquid.

7

FYI, this is a common issue. Tandem instructions here: