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[IP] Animas Pump Problems

Tom Wrote:
 There may be a tremendous variation re: occlusion detections which the Animus
pumps do not take into account. Yours was set to HIGH and mine was set to LOW
for occlusion sensitivity.

Ricardo Responds:
 Pure speculation on my part, but I suspect part of the function of the
occlusion sensitivity is that it allows Animas some breathing room for QC
purposes given the task of delivering .025 units of insulin.

 Pumps have to distinguish between intentional movement of the pump piston (such
as delivery of the basal or bolus) and unintentional movement (such as may occur
if a small bubble is in the cartridge and its volume changes due to temperature
and/ or pressure, which can cause the piston to move or increase the back
pressure). For cartridges of similar bore, Animas competitors have approximately
twice the breathing room since they can only deliver .05 basals as compared to
the Animas .025. This makes the Animas more sensitive to environmental
conditions, but in my opinion, the Animas track record is outstanding given such
tight tolerances.

 Having observed the occlusion error once in my 4 years of Animas pumping, my
observations are that moving from a relatively low temperature area to a high
temperature with the smallest of bubbles in the cartridge, may cause the bubble
to expand and be interpreted as an occlusion due to the increase in back
pressure. This was easily solved by rewinding the piston, reloading and priming.

 OTOH, I experienced the no prime alarm when moving from a relatively high
temperature area to a lower temperature area. In this case an air bubble will
contract and the piston may lose contact with the cartridge which the pump
interprets as no prime. In this case a simple load cartridge and prime resets
the piston onto the cartridge and eliminated the alarm.

 Some users have their sensitivity set on high and never get the occlusion
error. If occlusions occur on high, Animas seems to have a 2 step resolution.
Step 1 is to tell the user to set it to low. If step 1 does not work, step 2 is
to have the user send the pump back for replacement. To deliver .025 units of a
liquid in a pump subject to various environments and end users is no small feat.
I think this would show up frequently in the FDA database if this was a
significant reoccurring problem.
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