Omnipod, Air Bubbles, and Varied Performance

Diabetes Technology Insulin Pumps
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This is a fairly long report on my quest to better understand the anatomy of the Omnipod and to help myself figure out why the performance often varies so much from pod to pod.

Having been an on and off Omnipod user for 10 or so years, I have both loved and hated the device. Some days, weeks, and even months, the pods seem to work great, and other days they seem to not work at all. One thing I’ve noticed in particular is that often times after a fresh pod change, it often takes a day or so of terrible BG before the pod suddenly appears to work perfectly and I stabilize. Recently it got me thinking, what could be the cause of this seemingly sporadic performance?

After racking my brain, I got to thinking about air bubbles. I know that it is possible for them to be introduced into the system while filling the reservoir. Does the initial Omnipod cannula purge successfully rid the system of ALL air bubbles in such a short amount of time? Also, if it fails to accomplish this, are there safeguards to prevent air from entering the system? I know it is capable of detecting an occlusion but I have not heard of it having the ability to detect whether it has inadvertently pumped air instead of insulin…

So in order to better understand the anatomy of the Omnipod, I took one apart recently piece by piece. The pod i deconstructed was a pod I had removed in frustration after horrible BG over the period of two days. It didn’t seem to be working at all. After ripping off the adhesive pad The first thing I noticed was a very large air bubble in the reservoir! Keep in mind, this is before I had broken into the pod at all, at this point it was completely intact and air tight. Once the case was split into two and the innards were removed I could finally see the route of the insulin from the reservoir to the tip of the cannula. I could observe that where the insulin would exit the reservoir was on one of the back corners towards the back side of the pod. I could also see that that the pump was driven by a gear which I could now turn with my finger.

Imagine looking down at your stomach where you might place one of your pods. If the front of the pod (where the cannula is) is facing towards the right side of your body, this will have the point where the insulin exits the reservoir at the top of the pod (of course air bubbles in liquid are always going to float to the top…)I did an experiment by facing the pod in this direction and spinning the pump gear. Small amounts of insulin filled with air began to form bubbles at the cannula tip and pop before ultimately no insulin came out at all! The pump was compressing nothing but air!

I then turned the pump where the front would be facing the left side of my body. This made the insulin exit point on the bottom of the pump with the air bubbles opposite it (simple physics right?) I then began to turn the pump gear and the insulin flowed out of the cannula with no issues whatsoever…

This was very disturbing to me. Especially as 99% of the time the purging process will happen while the pod is on it’s back which would place any air bubbles in the center of the reservoir and not in the corner where they could be removed by this process.

Now I do not claim to be a scientist, medical expert, or a mechanical engineer, and I know this is just an experiment performed at my kitchen table and not in a controlled laboratory, but honestly it doesn’t seem like rocket science to me. I truly believe that this could potentially explain some of the varying performance I am seeing personally from my Omnipod.

The first course of action for me in the future is to make sure ABSOLUTELY NO air bubbles are in the filling syringe at all. Second would be to make sure pods always face to the left side of my body (when placement is horizontal) to make floating air bubbles opposite the reservoir’s exit point. If the pod is being worn on my arm or leg (where it must face vertically) I will always face the cannula upwards in order to keep the air bubbles at the top of the reservoir and opposite the exit point.

I will personally take these steps in the coming months and see if I begin to find an uptick in performance from my pods. I will report back to you with my results.

Hope you have found this interesting :slight_smile:

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I don’t use Omnipod, but I’m sure this will be really helpful for those who do.

I recently took a dremel tool to one of my T:slim cartridges myself, just to see how it worked. It was remarkably unimpressive. Just a plastic bag inside the cartridge with a fill port, a hole the pump’s piston goes into, and the pigtail exit. Everything but the bag was pretty much already visible before cutting the cartridge open. Still, it was fun to see.

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Thanks @Robyn_H ! Now I won’t waste my time and cut a TSlim cartridge open. :slight_smile:

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Your OmniPod rep should have explained all of that to you when you 1st started it, although it was a long time ago :slight_smile: . Mine spent quite a bit of time on this exact subject when I started years back and I have never had any priming issues at all.

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I had a few days one box of pods ago, where I had some highs that didnt seem to want to go down. I had begun to think my whole system changed and I needed to change all my settings. But a few pods later, all was back to normal. I did remember having some issues with the vial of insulin, so I tossed it but the problem was still there. My next thought was air bubbles, and if one had gotten through. Usually I make sure the filling syringe is ok, but sometimes you get some that act kind of wonky. I had also tilted some pods downward a tiny bit. I guess it could be a lot of things, but all is well now and I really really dont even want to go back to my old pumps!

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I have found that if I wear the OMNIPod on it’s side it seems to work better than when it is placed vertical. When it is vertical it has to work against gravity to pump the insulin up through the cannula.

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I find this very interesting, and not something that’s been addressed by my Omnipod rep at all. She only mentioned that because there’s no tubing, and it’s a closed system, that there are no issues with air bubbles - ha! I also find some pods work great, others are terrible, and some days better than others.

I always wear my pods on my thighs, with the cannula down, so I’ll try them the opposite and see if I notice any differences. I have a hard time wearing them anywhere else - pain, site irritation and less good absorption. I’m curious to hear if these changes make a difference! I hope so.