Position of Insulin Pump Can Cause Fluctuations In Insulin Delivery Rates

Found this last week at Diabetes In Control

Lede paragraph reads:
A new study showed that changes in the position of a conventional insulin pump, relative to its infusion set, can significantly impact expected insulin delivery rates. The rates depending on how the insulin pump was worn varied from 74.5% of the expected delivery upward to 123.3% of expected delivery rates.

The issue is one of gravity: whether the site is above the pump, and it has to fight gravity to send the insulin through the tubing, or whether it is below the pump and the flow of insulin is aided by gravity.

All-in-one pump designs – such as the OmniPod – are affected by the position of the reservoir relative to the body, but the difference in insulin delivery is more like 1.5% than 25% difference.

The link above should bring you directly to the article in question.

Please note that the study was supported by a grant from Insulet Corporation (Nasdaq: PODD) of Bedford, MA. Insulet manufactures OmniPod and has a vested interest in showing their devices to be more accurate than competitors’ devices.

I just read the article and giving percentage makes it look like there is some huge discrepancy between a pod and a pump with tubing and the affects of gravity. If the results actually had a huge impact on insulin delivery every time I go to bed I should see something crazy happen to my BG because the pump is now horizontal and not vertical and below the infusion site.

This study seems a bit far fetched, I look forward to reading more on how they came to their conclusion.

I have to agree. Suspicious. But at least semi-transparently.

Read a bit closer…

“They found that raising or lowering a conventional insulin pump, to the full extent of its tubing, can significantly affect the accuracy of insulin delivery, especially at low basal infusion rates. “This is particularly important for children, for whom low basal rates are often used,” Dr. Zisser noted. The most pronounced differences were seen during basal delivery in the Cozmo and MiniMed pumps. For the 1U/hr rate, differences ranged from 74.5% of the expected delivery when the pumps were below the pipettes and pumping upward to 123.3% when the pumps were above the pipettes and pumping downward. For the 1.5U/hr rate, differences ranged from 86.7% to 117.0% when the pumps were below or above the pipettes, respectively.”

I don’t ever extend my tubing completely, nor have I seen another pump user do so. But I think if it makes a difference then the pump manufacturers should investigate and update their literature and perhaps their technology. This study looked at the Minimed 512 and 515 pumps, and the Deltec Cozmo 1700. Perhaps the 700 series Minimed pumps do not share this alleged problem.

Actually, the 700 and 500 series Minimeds are the same models - just different reservoir capacities. The 512 is the smaller 712, the 515 is the smaller 715, the 522 is the smaller 722, etc.

But, yes, you’re absolutely right. The current model pumps for both Minimed (522/722) and Cozmo (1800) were not reviewed in the study and few people I know ever walk along with their pumps trailing 42" behind them on the ground. Although now I’m picturing some kind of field day event for diabetics with tails…

The interesting part is they said gravity but if you think about it it could be caused by the tubing expanding or contracting based on air temperature. Not to mention tubing length, I use the 24inch tubing since it is shorter has less time for expansion!! Most toddlers are probably not using 42in tubing, seems like it would be a strangulation hazard.

Similar to what David said, many people do use the 24" tubing, which is much shorter. I often put my site on my thigh and have my pump tucked in my bra. During those times, my tube is fully extended and almost directly vertical, with the pump being above the site.

I’m not sure how much difference there is btw the 500/700 series, 515/715 series, and 522/722 series. It’s possible that it WAS an issue with the 500/700 series, but has since been resolved. Someone with more knowledge about the difference between these pumps could probably answer that better.

Disclaimer: These comments are more about the summary and replies, since I haven’t read the article yet. :slight_smile: