I read there’s a 10% chance of a bent cannula. In about 3 months of using my insulin pump, I’ve had 2 bent cannulas on my infusion sets.

Yesterday, I replaced my infusion set in the morning. I noticed that I needed more insulin than usual, but didn’t suspect a bent cannula because recently I’ve been having higher stress than usual and needing more insulin… So I figured that’s what was going on, still.

In the late afternoon, I noticed that my blood glucose was increasing despite eating a salad for lunch and exercising. Hmm…

I still didn’t think it was the infusion set. With some manual overrides, I was able to get my blood glucose to be back down at around 130.

But then before bed, it started spiking. I figured that it was the food I ate… So I figured I must have under-counted the number of carbs, so I did a bolus at bedtime for this spike. It will still going up, so I thought wow I must really need insulin, so I did another bolus. At that second bolus, that’s when my Medtronic 670g Insulin Pump sounded its alarm and said “INSULIN FLOW BLOCKED! CHANGE RESERVOIR!” It was very noisy and forced me into a required rewind screen.

I removed the infusion set from my body and that’s when I found a severely bent cannula, as pictured above.

I loaded the insulin reservoir and replaced the infusion set and the pump returned to delivering the basal insulin. Pump was happy again.

It was quite a shake up for me before bed! Guidelines suggest not changing your infusion set before bed. You’re supposed to do it earlier in the day so that you can monitor to see if the infusion set is working correctly. And I did do that!! Sigh… So this shows you that a bent cannula can still deliver some insulin for a period of time. This is definitely one of the most disappointing things I’ve experienced since using my insulin pump. 😔 😩

The pump said to “consider an injection.” I was worried because I had just done a couple of boluses and didn’t know how much of that my body absorbed… My glucose was high (260) but it wasn’t still climbing. So I decided to hold off for a couple of hours to see what the active insulin would do. I silenced my pump’s high alerts for 2 hours, and went to sleep. I woke up a few hours later and bolused… My glucose was coming down. And then I bolused again later when the pump woke me up because it had reached maximum delivery in auto mode… I checked my blood glucose and administered the suggested correction dose.

By morning, I was down to 130!! When the cannula isn’t bent, this pump really excels. 👏

Next Steps

I’m going to try to get some samples of other types of infusion sets to see if the Sure-T ones that have a steel needle instead of a plastic cannula will work for me. It sounds like a lot of people like them but some people find them uncomfortable.

Related Reading

• Infusion Sets for Insulin Delivery – Medtronic page that describes the different infusion sets available.
• Medtronic: Which Infusion set is right for you? (PDF)
• Get Bent | Six Until Me – Blog post about a bent cannula experience.
• Bent Cannula – Why do Cannulas go bad? (Diabetes Forums discussion board)