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[IPk] Bent cannulas

Hi Bev,

During the first few months of pumping I had real problems with bent cannulas 
and control in general.  It was very frustrating at the time, I was almost 
dissuaded from pumping.  The following are my observations, hope they might 
be of some help.

With the normal-sized sof-sets, I found that about 50% of cannulas bent, 
usually at 90 degrees at halfway down the cannula.  I changed to the "Micro" 
version, supposed to be for children and skinny adults (I'm not skinny, but 
I'm fairly muscular) and practically overnight things changed - better 
control, far fewer bent cannulas.  Cannulas can bend particularly if you're 
not relaxed when you insert (I think this was the problem for some of the 
children on this list), or if you don't hold the "whanger" firmly enough 
against the skin (with these, you tend to get the 90 degree bend in the 
cannula at the top of the set - as opposed to the end inside you), and 
insertion often hurts.  It can also happen if you use a set with a cannula 
which isn't the right length for you (you're an athlete, perhaps the Micro 
type might be useful? - AMT let me try some out first, don't know if 
Medtronic will let you do that, I could send you a few to trial if you're 

But I am also interested that you changed your set the evening before and had 
a normal BG next morning.  That implies that your set was working during the 
night.  Don't discount the possibility that the cannula became dislodged and 
bent early that morning, especially as you had visitors and perhaps were 
doing more than or different from what you'd usually do.  This has happened 
to me before, and I've told the story of how, when helping a friend move 
house and doing some lifting I felt a sharp twang and yes, that was the 
cannula bending.  My bgs had been fine the previous day and that morning, but 
were in the 20s when I got home and the cannula was bent at 90 deg.  Have 
also had this occasionally after restless sleep at night, particularly when 
on holiday in an unfamiliar bed.

Like Pat, I've found that an alarm often doesn't sound when there's no 
delivery from a bent cannula.  In my case the limit seems to be 2 units 
delivery (as a bolus, not cumulative) so as my max basal is 0.9 units and I 
seldom bolus more than 1.5 units, this can be a problem.  I have deliberately 
bolused more than 2 units when I really think there's a problem, and the 
alarm does work then - at the 2 unit mark.  However, be aware that if the 
cannula has actually popped out of your skin and is lying under the dressing 
(has happened to me several times during physical exercise) then it can 
merrily pump away useless insulin without any alarm, whatever the dose, and 
surprisingly it can be a while before this is spotted.

Best wishes,

IDDM 30+, 508 23 m
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