How often to change your infusion set

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Simbul

Simbul

Active Member
Relationship to Diabetes
Type 1
I've been running a little test recently. My meter (Bayer Contour Next USB) makes it fairly easy to export data to a computer, so I've been crunching some numbers.

I've always changed my infusion set (Medtronic Silhouette) every 4 days, though the official recommendation is 3 days. Some time ago I started to wonder whether this was affecting my control at all: was that 4th day making my average blood sugar go up? I had the data, so I set out to experiment.

The hypothesis I wanted to prove was that absorption degrades the longer you wear the infusion set for, which means on average blood sugar should be higher 4 days after changing the set than a couple of hours after the change.

I won't bore you with the details, but running a linear regression on my BG measures shows that there is a correlation: my readings tend to creep up the longer I've been wearing the set for.
However, the increase is negligible: it's something around 0.2mmol/l each day. So if my average was 5.0, I could expect that to go up to 5.2 after 1 day, 5.4 after 2 days and so on.

Please keep in mind these are my personal results so they may not apply to anyone else. Also, I haven't been following a rigorous experimental protocol 😉

This answered my original question, as I think the comfort of having to change my set less often is totally worth an average increase of 0.2mmol/l (the difference between day 3 and day 4).

I hope this could be of interest to you as well, even if just as a reminder of how much power we hold, with all the data we're collecting about ourselves 🙂
 
So is it the cannula causing the increase or the insulin it's self?
Temperature/time of year could be an issue plus how often you change a cartridge could also play a major part.

Personally I change my set every 3 days and the cartridge when empty, about every 8 days at the moment (200/u animas cartridge) haven't noticed any difference in numbers.
 
I change every 2 days because it always starts to itch and irritates if I leave it in longer.
 
We usually change every 3 days which fits in nicely with cartridge lasting 6 days - so do cannula only one time and then the whole lot together the next time. Very very occasionally we get a rapid rise in BG on the third day but not yet often enough for me to think that we need to change every 2 days. And I'm talking rapid - normal reading at breakfast time, 12 at lunch, 19 at tea time (even after corrections) which usually then comes straight back down again after cannula change even if we don't change the insulin too.

I'm actually having more problems at the moment due to school holidays as we are out of routine and no two days are the same. So if we are just at home not doing much she's high most of the time and basal is going up and up, but then as soon as we have a day out or do anything at all she will be hypo all the time. So am using temp basals a lot at the moment and not getting it right very often :(
I'll probably just get it cracked in the last week of the hols and then she'll go back to school!
 
Pumper_Sue said:
So is it the cannula causing the increase or the insulin it's self?
Temperature/time of year could be an issue plus how often you change a cartridge could also play a major part.
Click to expand...

Initially I thought it was the insulin losing effectiveness, but after talking with some doctors and seeing how often folks on this forum are changing their reservoirs, I think that's a red herring.
Insulin is probably the most stable component here. My guess would be that the infusion site can only take so much insulin, probably something to do with lipohypertrophy and how it screws with insulin absorption (i.e. the same principle on a much smaller scale).
 
Pumper_Sue said:
Personally I change my set every 3 days and the cartridge when empty, about every 8 days at the moment (200/u animas cartridge)
Click to expand...

I hope this doesn't distract the original question, but I was fascinated by this bit, Sue.
How do you judge 'empty' - do you allow the pump to alert you that it is getting low in insulin? What happens if that's in the middle of the night? Or do you check the amount, and if so how much remaining do you class as empty?

I currently change cannula every 3 days and cannula and cartridge evey 6 days regardless of the amount of insulin.(Exactly as recommended by the DSNs at the pump clinic) If I haven't had to get rid of bubbles or eaten a high number of carbs, then I am probably discarding a fair amount of insulin, so it might be a good idea to try and keep the cartridge going another couple of days or so. Interested that you have found no problem - my results are pretty erratic anyway, I'm fairly sure cannula and cartridge changes don't affect the results
 
heasandford said:
I hope this doesn't distract the original question, but I was fascinated by this bit, Sue.
How do you judge 'empty' - do you allow the pump to alert you that it is getting low in insulin? What happens if that's in the middle of the night? Or do you check the amount, and if so how much remaining do you class as empty?
Click to expand...

Pump alarms at 10 units, so I change it when it get's down to 5 units so as little waste as possible.
I've never had it alarm in the middle of the night for low insulin so have been lucky and only had a couple of issues with bubbles in almost 8 years of pumping. If bubbles were or are seen then I would keep an eye on the tubing and prime them out once they reached the end of the tubing.
 
It has always interested me that some reservoirs seem to be rated for longer use than others. Medtronic ones are supposed to be used for a maximum of 3 days (as are their sets). I asked my nurse when I started as I already know some Roche pump users who changed full (reservoir and cannula) followed but cannula only. My nurse said something vague about 'manufacturers recommendations' and the possibility of insulin interacting/reacting with the plastic vial the longer it was in contact.

As a result I have only ever 'just over half' filled the smaller reservoir on my Veo and use the 'low reservoir' alert as a set change reminder.

I aim to change at between 2.5 and 3.5 days. Usually closer to 2.5.

I have seen (though I can't remember where!) a clinical research study into exactly this and from what I can recall with a larger cohort the effect increases to reach statistical significance. Sites in longer than 3 days do seem to produce measurably higher BGs for most people.

Having said that I can understand your logic Simbul given your results. One of the main things that put me off steel cannulas when I tried them out was that the 'every 2 days' change time came around reeeeeeaaaalllly fast. It wasn't like I was getting Amberzak's no itch reward - I was just spending a lot more time faffing with sets and cartridges.
 
Thanks Sue and Mike - I am thinking of changing what I do now. I will still change my cannula every 3 days , but cartridge as required. So not tomorrow as theere's 81 units left, but I won't go over 8 days, and will consider putting in less insulin - except for the bubble possibility
I don't really want to discuss bubbles (!) I have never actually seen them in the tube, but constantly in the cartridge. I prime them out every now and then, always with no effect whatsoever on my results. When I change the infusion tube, as I unscrew it there are always loads of bubbles in the exit from the pump itself. End of bubbles discussion!!
 
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I do do everything you do (!) on your video when filling my cartridge. I liked your description of 'champagne' bubbles, I see them too, and I think they conglomerate with time to form bigger ones. The presence of bubbles is the bane of my life. Having said that I genuinely never see any in the infusion tubes, so I don't think they cause me a problem, my pump always hangs upside down, so the bubbles are away from the feed. I do have very variable results but can't pin anything down in particular. It's mostly just constant attention to the fine detail - and then of course the usual unexpected highs or lows!
 
heasandford said:
I do do everything you do (!) on your video when filling my cartridge. I liked your description of 'champagne' bubbles, I see them too, and I think they conglomerate with time to form bigger ones. The presence of bubbles is the bane of my life. Having said that I genuinely never see any in the infusion tubes, so I don't think they cause me a problem, my pump always hangs upside down, so the bubbles are away from the feed. I do have very variable results but can't pin anything down in particular. It's mostly just constant attention to the fine detail - and then of course the usual unexpected highs or lows!
Click to expand...

Have you tried a different type of cannula? I ask because this made quite a difference to my readings.
 
I think I assumed that a cannula would be consistently wrong in one direction or the either - ie either high or low? Did you find that a different cannula worked with both?

I have eaten the same breakfast every day for the past fortnight, with the same amount of insulin and the same length of time before eating. Well, not quite the same time, using the Libre has allowed me to watch my BG, and when I see a downward arrow I eat. Admittedly this depends on how high I was before breakfast. Anyway, some days I am still over 8 two hours later, and sometimes I am below 4. Just having a diabetes moan you know!
 
heasandford said:
I think I assumed that a cannula would be consistently wrong in one direction or the either - ie either high or low? Did you find that a different cannula worked with both?

I have eaten the same breakfast every day for the past fortnight, with the same amount of insulin and the same length of time before eating. Well, not quite the same time, using the Libre has allowed me to watch my BG, and when I see a downward arrow I eat. Admittedly this depends on how high I was before breakfast. Anyway, some days I am still over 8 two hours later, and sometimes I am below 4. Just having a diabetes moan you know!
Click to expand...

I found results inconsistent and variable to say the least. Best results for me come from using the angled sets.
 
I am a bit afraid of putting the angled needle in - they are so long, and when I went on a pump I was so pleased to get the cannula inserter from Roche! I just drew blood with the angled one. I notce from Mike that he has an applicator for his angled set, maybe I should find out if it fits the Accuchek pump. I don't have a lot of body fat either
 
heasandford said:
I am a bit afraid of putting the angled needle in - they are so long, and when I went on a pump I was so pleased to get the cannula inserter from Roche! I just drew blood with the angled one. I notce from Mike that he has an applicator for his angled set, maybe I should find out if it fits the Accuchek pump. I don't have a lot of body fat either
Click to expand...

Yes it does look a bit of a monster compared to the shorter 90-degree ones, but it actually only reaches the same depth, or slightly less depending on the angle of insertion. I'm a *bit* surprised that Accu-check don't have an inserter - though I do know a lot of people choose to manually insert the Medtronic ones.

There is certainly something about angled sets that suits me really well. Far far less discomfort than 90-degree ones, and I don't get those kinked cannulas any more. Perhaps because any pressure against the site goes more 'sideways' through sub-cutaneous tissue than directly pushing the cannula further in against muscle or whatever.
 
heasandford said:
I am a bit afraid of putting the angled needle in - they are so long, and when I went on a pump I was so pleased to get the cannula inserter from Roche! I just drew blood with the angled one. I notce from Mike that he has an applicator for his angled set, maybe I should find out if it fits the Accuchek pump. I don't have a lot of body fat either
Click to expand...

I have been using the animas inset 30 which has an applicator and have gradually come to hate it :( So after discovering the comforts were on offer from Animas I tried those and was really surprised at how easy they went in and less painful (pain free) than using the inserter.
The comforts come in two lengths 13mm and 17mm. I use the 13 and didn't find then scary at all.
Animas kindly sent some sample packs for me to try. I can now save my CCG £30 a box on cannulas by changing over :D
 
When to change the insulin in your pump

I use a Medtronic 640G. It says change every 3 days, but I change the insulin set every 4 1/2 days. I test BG very frequently and almost never have higher BG readings at the end of that time. Maybe I'm mean, but I don't change the needle on my Accuchek Mobile BG tester often either. I've never had any skin irritation or infections from this. I've had Type 1 for 59 years. We are all different so do what works for you.
Adam
 
Well done Adam ! That's a long time to be T1. I also use a Medtronic & like you never have any problems with skin or sticky, don't use any extra sticky. Have a look at "Love my Pump" thread. 🙂
 
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