Prevent insulin pump cartridge bubbles


#1

I’ve been using insulin pumps for a long time and I’m aware of the challenge posed by air bubbles in the pump cartridge. A few weeks ago, I woke up with unexplained high glucose. I thought at first that the cause was insulin site absorption degradation - “third-day fade,” so to speak.

I change my infusion sites every three days and my cartridge/infusion tubing assembly about every 10 days. I do this for the convenience. My cartridge holds 300 units and I only use about 30 units/day.

Following my overnight high, I changed my infusion site and while doing so, noticed an insulin air gap in my infusion set tubing. Now that likely explained the high.

I know that air bubbles in the reservoir are the reason for the insulin air gaps. I’m careful about air bubbles when I load my cartridge with insulin and spend some time and attention expelling them from the cartridge. I’m also aware that this issue is a common problem and has been written about many times on TuDiabetes.

It’s been a problem for me from time to time but mostly I’ve been lucky with this. That recent episode, however, was not the only one to challenge me. I’ve had this happen like four or five times in the last two weeks.

I went onto another diabetes forum this morning and posted about this and one of the commenters wrote about a technique that she’s successfully used over the years. She called this technique, “degassing” and included a link to a YouTube video about it. I was surprised that this video was posted in 2008. I have never seen this suggestion before.

Here’s the Youtube video.

I just used this tactic and it appears to be successful. Time will tell.


#2

I wonder if your 10 day reservoir usage also contributes more time for air to get in as the pump mechanism pushes the “plunger” to deliver insulin.

I use the 1.8 ml reservoirs, fill completely and get about 6-7 days. I don’t fill reservoir every time I change infusion set, although sometimes it works out to be the same time.
When I do fill reservoir, I make sure there are no bubbles, even on the bottom near plunger.

I have seen small bubbles in tubing, but nothing as large as what you are showing.

I watched youtube, but think I will stick with my method. Hope it works for you.


#3

That’s possible but I don’t think I can prove it.

One thing I’ve observed, however, is starting with a bubble-free cartridge and then see bubbles develop over time. They seem to come out of nowhere. I’m thinking the bubbles come out of the insulin itself.

I’ve seen this topic raised many times over the years but it hasn’t been much of a problem for me until recently. Thanks for your comments.


#4

Great post Terry.

Gas coming out of solution makes perfect sense. The atmospheric gases (CO2, O2 and N2) are dissolved in the aqueous insulin when trapped in a vial under positive pressure (Henry’s Law).

Similar to N2 coming out of blood (the bends) when ambient pressure is reduced.

Definitely going to try this :+1:t3:


#5

Certainly fine if the reduced pressure does not hurt the insulin.

But does insulin last as long in a partial vacuum, which would be the case with the remaining insulin in the vial. I don’t know if that’s been studied.


#6

I see small bubbles too, by end of reservoir. My theory is that as plunger is pushed, there are tiny leaks between the rubber part and sides of reservoir. Before filling, I twist the plunger portion up and down in reservoir, as I think I was told there is some lubricant that is spread around by this action, may prevent leaks.

When I fill from insulin bottle, at the end I remove reservoir, but leave the connector part (between bottle and reservoir) on the bottle. This allows the insulin bottle to equalize the pressure if needed. Then I remove the connector from bottle.


#7

This is what the YouTube poster also does.

This process only subjects the insulin in the vial to a partial vacuum for about 10 minutes. I don’t know if this hurts the insulin or not. If it does to any significant extent, I’ll feel the effects of that soon.


#8

Goodness, that’s a lot of air! The only bubbles I get are “champagne” bubbles, which are totally inconsequential. I’ve been using Medtronic pumps since '96 and learned some time ago how to quickly purge the reservoir and line of air. I don’t have the patience to write out detailed instructions–sorry! HINT: it involves tapping and vertical orientation during the purging procedure…

FYI: I am currently using a 551 (530G).


#9

Before I began using a pump, bubbles were one of my major concerns as something I wouldn’t be able to easily see. After doing quite a bit of reading about what worked for others who were blind or severely visually impaired, I learned that people were having success using penfills (pen cartridges, not disposable pens) instead of vials. I think the fact that you don’t have to inject air to withdraw insulin plays a big part in why they get fewer bubbles. Sometimes I see a big bubble near the top and I’ll withdraw that first.

I’ve also more recently begun pre-filling cartridges by about a day or half a day. I started doing this mostly for convenience, as my pump often runs out of insulin at a very inconvenient time. But I’ve found by filling the cartridge a half day ahead of time and letting it sit, all the tiny “champagne bubbles” that I can’t see often settle into one big bubble at the top that I can then easily get rid of.

I also always have my pump cartridge facing up, with the tubing at the top, as I’m filling the tubing so that any bubbles rise to the top and are expelled through the tubing before the insulin.

Using all of these strategies I can’t say I’ve never had air in my tubing, but doesn’t happen all that often (I’ll often check my tubing under high magnification with an unexpected high, and most often I don’t find any air in the tubing or cartridge).


#10

I do this as well. I was told that the Cozmo cartridges had a lubricant that was spread around with this twisting and up-and-down motion. I don’t know if the same is true of Animas cartridges, but I’ve just continued to do it, and I’ll do the same when I switch to my next pump (likely a t:slim).


#11

That’s most likely, as @Jim_in_Calgary explains, gasses are dissolved in the solution. It’s similar to the formation of air bubbles in a glass of water left on the table for a couple of hours. In laboratory conditions, when air bubble formation may be undesirable, it is possible to remove dissolved gasses from a liquid using techniques like sonication, which uses ultrasound. But for home purposes, degassing isn’t feasible.


#12

Very clever, gonna have to give it a try. One minor thing is that MedT a while ago issued an alert about reversing the position so the vial is on the bottom when you remove the reservoir–something about avoiding any excess insulin drops from adhering to the reservoir and causing problems after it’s inserted in the pump. Not sure it’s really a big deal but I’ve always done it that way just because. But I have always hated bubble thwacking since back when syringes were all we had, and one of the things I loved about injector pens was not having to do that anymore, so it was one of the things that bugged me when I started on a pump. Oh no, not bubble-thwacking again, ugh! This is a little more elaborate but definitely worth a try.


#13

Quick tip: filling reservoir with room temperature insulin results in fewer bubbles.


#14

I’ve noticed that sometimes the champagne bubbles form and then go back into the insulin. Also, champagne bubbles can aggregate into a substantial bubble. I used to flick the connector checking for bubbles, but am now careful to flick on the reservoir. I think air might get in when the connector is disturbed.

I need to try the degassing procedure. Thanks for posting the video.


#15

An inch of tubing holds about 1/3 unit of insulin, so it’s going to take a LOT of air in the tubing to harm someone from high blood sugars due to air in the tubing. People get way too worked up about small amounts of air in tubing.


#16

In 32 years of pump use, it has never been a problem for me. There was a time when it was possible to over tighten the tubing and the hub cracked. This would leak insulin and cause bubbles. Very obvious. Infusion set manufacturer changed material hub was made of. May be 25 years ago.

There are so many variables that affect blood sugar that this seems insignificant. Is this a solution in search of a problem?


#17

I generally agree with your sentiment here. I’ve also used insulin pumps almost continuously for 32 years. Bubbles in the insulin cartridge have not happened a lot to me but when they do, it means my blood sugar is subject to a sustained rise into hyperglycemia.

I also agree about the many factors that play into blood glucose levels. Cartridge bubbles are not a significant player in this category but I’ve found that addressing all of the factors collectively leads to overall improved BG performance.

No, I don’t think this is a solution in search of a problem. I’m interested in every factor that sends me into hyperglycemia.


#18

I take relatively small amounts of insulin daily, 15 units or less, total. With my Animas pumps I had constant bubble problems so I had a constant habit of disconnecting and holding the tubing up to the light to see bubble possibilities. My comments/complaints went nowhere so I simply accepted the fact that I was getting…bubbles. And the idea that 1 inch of tubing contains 1/3 unit of insulin is…significant, at least to me. So imagine 5 inches or more of space–those big bubbles. My helpful scientific husband and I have never figured out a cause except for the fact that I use a reservoir for several days—not just three. With my “new” 630G, I heard people say that they had NEVER had bubbles. What a lovely thought. However, same problem – I just save a plunger for the reservoir so I can remove the cartridge, push out the bubble, reconnect everything and go on. Not checking is dangerous.


#19

I have been on various Medtronic pumps since the early 1990s and never had a “bubble” issue. My technique: hold the pump upright with the tubing held tightly above it during priming. Allow 4-5 drops if insulin to come out, then put the needle into my body. Bubbles and air conditioner me out during the priming.


#20

As I replied to @Penn, this situation with cartridge bubbles has occurred infrequently with me. I primarily used your technique apparently successfully over the years. And I used it when I ran into a spate of bubbles in the cartridge. I wonder if there is some quality aberration in the cartridge manufacture that contributes to this phenomena.