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Re: [IP] Pumping Questions

-----Original Message-----
From: Carl Baker <email @ redacted>
To: email @ redacted <email @ redacted>
Date: Monday, November 23, 1998 7:05 PM
Subject: [IP] Pumping Questions

>I'll be meeting with pump representatives in the near future.  I feel that
>each supplier with give me a sales pitch and claim their pump is superior.
>With only two choices, I have a 50% chance of choosing the best one.  Is
>there really any major differences in the pumps?  Please let me know your

Every user swears by his pump.  Minimed users report what I consider a
disturbing frequency of no-delivery alarms, a problem I feel stems from its
lower pumping pressures and use of plastic cartridges (see below).  Even so,
Minimed pumpers report being satisfied with the remediation to their
problems and its users swear by their pumps also.

After someone has made an investment of over four thousand dollars in a
piece of equipment, he tends to be very defensive about his choice.  So we
tend to build up our choice.  I would imagine what I have to say will
engender some defensive writing.

I have been using the Disetronic H-Tron plus V 100 for one year.

Here's some (objective I think) considerations that persuaded me to choose
that unit.

Disetronic sends two pumps, as the pump is programmed to turn off for
factory service after two years of pumping.  After service at the factory
each pump is returned with an additional two years of warranted service.
The extra pump can be used anytime as a back up.  Minimed sends one.

NOTE:  Some Minimed owners say the two pump approach turns them off; that
the unit must be bad if users need a spare.  Not so.  The reality:  I've
never even powered up my spare.  But if I need to send in a unit for
service, I'm assured I won't have to go back to multiple injections, or
worry how long they have to keep the pump.  I haven't taken a single
injection since I began pumping.

Minimed uses a solenoid to push insulin a tenth of a unit at a time.  If a
user has a basal dose of 8-tenths of a unit hourly, the Minimed will click
eight times an hour, or once about every seven and half minutes.  In
delivery of boluses of, say, 6-1/2 units, the Minimed will click 65 times
and it will take several minutes to deliver.

Disetronics pump an infinitely variable dose of insulin through a screw
drive.  Five percent of hourly basal dosages are delivered each three
minutes.   In the above case, 8/10 unit per hour, 4/100 unit is delivered
each three minutes.  The above cited bolus of 6-1/2 units is silently pumped
in a matter of seconds.

Minimed would not match the delivery frequency capabilities of the
Disetronic (that
is, a click every three minutes) until the basal dosages exceed 2 units an
hour.  That's much higher than the basal rate of virtually every user.

With this in mind, I concluded that the Disetronic's delivery is smoother,
faster and closer to natural than Minimed's.

I looked at the pumping pressures of the two pumps, in the belief that would
have some bearing on pumping through any obstructions in the tubing.
Disetronic pumps at 2-3x higher pressures.  It turns out that more Minimed
users are complaining about non-delivery alarms.  I worried that the higher
pressures would induce pain during boluses.  It doesn't.

The Disetronic can be operated without damage underwater without
modification or addition of waterproof casings.  There's a removable tappet
designed to keep moisture out of the cartridge chamber, but even a flooded
cartridge chamber has no detriment to the pump or its operation.  Just
remove the cartridge and towel off the chamber.  All of the mechanical and
electrical components are sealed.  Minimed's are exposed and the unit can be
operated underwater briefly only after the user adds an optional, additional
sports guard.  This turned out to be pretty important for me since I swim
regularly for extended periods of time.  Hanging the pump around one's neck,
the Disetronic can be taken into the shower as well.  Get your Minimed
really wet and you'll have to return it for service.

Humalog is the ideal insulin for use with the pump because it acts rapidly
(<10 minute) and because such small amounts are used and in the body when
delivered by pump.  This also has implications in making hypos more

There's another fairly important difference between the two pumps related to
Humalog, with the Disetronic holding an advantage.  The cartridges for the
Disetronic can be plastic or glass.  Glass costs more and is the preferred
material.  All Minimed cartridges are plastic.

Plastic cartridges tend to degrade Humalog molecularly.  The Humalog is
attracted ionically to the plastic wall of the cartridge.  The plastic ones
also present more opportunity or propensity for contamination with air.

Humalog has some degradability properties that are problematic for pump
users.  Many of the Minimed users find they have potency/delivery problems
before their cartridges empty, and they have to change them sooner.  Many
also report they have to dilute their Humalog for various reasons.

Here's a description of a regimen for filling cartridges from the Humalog
vial.  I fill three glass cartridges (315u/each) sequentially at the same
sitting, and refrigerate all until placing each into the pump.  In other
words, I leave a cartridge filled with Humalog as long as two weeks before
pumping from it, and each has as much potency as the one before it.  I don't
believe Minimed users can do it the same way and I don't think they can have
the same result.

Plastic cartridges cannot be prefilled with Humalog that far in advance.
And even if they fill them just before placing the cartridge in the pump,
the Humalog remaining in the used factory-filled vial may be degraded as
well, perhaps by as much as 30 percent.

BTW, my last hgba1c  was 4.9%.

>Also, I have the same question regarding infusion sets.  What are
>users having the most comfort and delivery with?  Any information will be
>appreciated.  I will be asking more questions in the future.

My opinion is those with Teflon catheters inserted at shallow angles
(Minimed's silhouette and Disetronic's tender) are superior to metal needles
or Teflon inserted perpendicular through the skin.  Subjectively, I find
them more comfortable.  Objectively they are more slender.  Appealing to me
are their quick disconnects at the catheter (no pony-tail hanging off like
on the Minimed sofset).

OTOH, sofset users claim this is an advantage because they can disconnect
even when they cannot reach the infusion set.  How do they put them on and
take them off?  Additionally, the sofset can be inserted with help of a
mechanical plunger.

Again, the pumpers on this listserv are using all the different hardware and
each swears by the one he is using.

Insulin-Pumpers website http://www.insulin-pumpers.org/