Air Bubbles again!

My 18 year old son has been wearing the Medtronic Paradigm Revel for the past 3 1/2 years. This is the 3rd time -in this past year (March 2014 & Dec 2014) - that he has had a problem with air bubbles. The insulin is room temp., changed out the reservoir to a different lot, changed infusion set to different lot, changed out the battery, tried new vial of insulin, but still air bubbles. When the cartridge is first filled, it is perfect. Not even 'champagne' size bubbles. 2-3 hours later, at least 10+ bubbles fill the reservoir. This results in high blood sugars.

Medtronic has been pretty good about sending replacement pumps, but they keep telling us they have never heard of a pump being replaced because of air bubbles. Can anyone tell us if they HAVE heard of this problem?

When he gets the "new"/replacement pump the problem magically goes away. What gives??

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NONE of those things you mentioned has anything to do with bubbles. Namely, the pump, lot numbers of reservoirs or infusion sets, or room temp insulin.

I've pumped since 1996 and it took me a while to develop a technique for not getting bubbles. It's not about the hardware--it's about how one goes about filling the reservoir, and then removing the remaining air bubble that sits at the top of the reservoir. If I had the time, Id do a video of how to accomplish this as it takes more time to describe than I have patience for. bottom line it is none of the things you mentioned.

oh, and it took me more than a few years to "get it right".

make sure the insulin bottle is never shaken...

i've never made a video for online. i have an SLR and a cell phone. if anyone wants to give me a pointer for doing close up video without a helper, and how to post it online, i'll consider doing one.

I mentioned all of those things because that’s what the customer service rep gave as suggestions. I guess my frustration lies in more than a couple of years to get it right. He’s been pumping for 8 years but this last year has been very trying as far as air bubbles goes. I was looking/hoping for helpful input.

Air bubbles are a vexing problem for all insulin users (pump, pen or syringe). Every step in the cartridge filling process can introduce air bubbles, and more likely than not, you have air bubbles in virtually every cartridge fill (you may not see them!). I know I do! IMO, all you can do is minimize them and be on the lookout for if/when they enter the tubing.

I have been pumping for over 16 years and I still get them.

The single biggest successful step I have taken is to fill the new cartridge 12-24 hours in advance and let it sit upright until it's time to load into the pump. This helps all the bubbles to rise to the top, but it is not fool-proof as plastic is very cohesive to air in the cartridge.

The acts of inverting the insulin vial and drawing insulin into the cartridge will create air bubbles that are too small for the eye to see.

When I find bubbles in the cartridge days after I have loaded it, I just periodically pay attention to whether they have migrated to the business end of the cartridge, where they might enter the tubing. They rarely do, but if so, I just monitor and when they get near the infusion site, I prime them away. Normally, it only takes a small amount of priming (less than a unit) to clear if/when this happens.

I laugh sometimes at the instructions I received from my pump trainer to flick the side of the cartridge with my finger to get the bubbles off the sides/bottom of the cartridge, because with some bubbles, no amount of flicking will make them budge ... and then my finger hurts! Also, the flicking generally creates more micro-bubbles. This then makes some bubbles seem to disappear, but eventually they come back.

I also agree that none of the things mentioned by the Mini-Med folks has anything to do with air bubbles and everything to do with being in a call center with a script to follow - sigh!

Apologies in advance for the complete digression and nit picking ... OCD & all that.

plastic is very cohesive to air in the cartridge

I think you meant adhesive, not cohesive. "Cohesion is the property of like molecules (of the same substance) to stick to each other due to mutual attraction. Adhesion is the property of different molecules or surfaces to cling to each other." (copied from here).

Oh, thanks! I was writing this with a slightly lowered BG, so my editing hat was askew ...

Medtronic has been pretty good about sending replacement pumps, but they keep telling us they have never heard of a pump being replaced because of air bubbles.

I simply cannot see any way that changing the pump might directly relate to air bubbles. While I may just be missing something, I think it more likely that this is what some animal trainers refer to as a “cross association” or sometimes a "superstitious behavior". This refers to the assumption that something which is actually unrelated caused an unpleasant event to occur because it happened at/around the same time the "bad thing" happened.

In other words, I think some other change is actually responsible for the air bubbles being or not being there. It is most likely not changing the pump. You assume it's the pump because it appears to happen at the same time and you really want to find an answer.

I believe that the two most likely reasons for air bubbles forming in a vial after it is filled are:

  1. Using insulin that is colder than the (room) temperature the reservoir will be kept at. What happens is that as the temperature rises air which is dissolved in insulin comes out of solution.

  2. Drawing insulin from a vial containing air which is at a higher than "normal" pressure. This can happen if you don't equalize the air pressure in the vial after you have filled the reservoir. During storage, the air will dissolve into the insulin and reach equilibrium for the higher air pressure in the vial. If the air pressure is later reduced, that air then comes out of solution and you get bubbles.

So, if the insulin is always already at room temperature, perhaps it might be the latter problem. If you unintentionally leave pressurized air in the insulin vial, then you would get air bubbles later when insulin in the reservoir is at a lower (room ambient) air pressure.

That's all I have time to say for now. If any of the above is not clear I can try to talk at it further later.


I try to take at least 12 seconds or more (ie, draw SLOWLY) to fill the reservoir, to avoid pulling air into the res. I push a bit of insuling back into the vial, and draw to max fill level again, tap, push some more back in to the vial, tap, and make the final filling.

I hold the pump vertically, with the tubing pointing UP, and TAP TAP TAP the side of the pump against the hand not holding the pump, as I hold down the ACT button to fill the tubing. That action gets any stubborn bubbles to go to the tubing end of the reservoir, and thus get flushed out during the priming. At the end of 3 days of pumping, I still have no visible bubbles in the tubing. and I do mean NONE.

How do you equalize the air pressure in the insulin vial after you have filled the reservoir? I know to add in as much air as you draw out of insulin but don’t know about doing something after filling the reservoir.

You do NOT remove the needle guard during this process. You inject a FULL reservoir's worth of air into the vial (vial right side up), then follow my previous instructions. There is no issue of equalization when following my instructions.

this is why i wish i could easily do a video. :)