Are you in Phoenix, by chance? I live in Prescott, hits 100 a few days in Summer, temps run about 20 degrees cooler than Phoenix.
A lot of people have the bubbles. According to Medtronic, it must be all our fault, since the reservoirs always meet their design (I sent several in for testing). Of course, what they don’t admit to is that the design itself is bad.
i found a technique that drastically reduces bubbles, as follows:
- pull insulin into reservoir as normal, except rotate the plunger while pulling it back. This often releases a few little bubbles around the rubber O-ring
- Leave the plunger in the reservoir, with new tubing attached. Hold tubing in the air, so that insulin will flow upward from the reservoir
- Holding reservoir on the counter top, slowly press the reservoir downward onto the plunger, which pushes the insulin up the tube, until you see a bubble emerge from the needle (just like using the pump to push up the seal and drive insulin up the tube.)
- insert reservoir into pump and follow the rest of the steps as normal. As pump pushes its little driver into the reservoir, let it press out one bubble, then proceed to insert the Inset and add insulin to the tube, filling the cannula. All done.
What I believe is different is that the pump built-in plunger rotates as it moves up into the reservoir, so that the rubber seal is also being rotated, while it is being pushed. I examined the rubber rings. They are round, not square, but the cutouts for them are square. I believe the pump action distorts the rubber a little bit, creating very small routes for air to enter the reservoir.
Since Medtronic refused to research the cause of bubbles getting into the reservoir, I filed a complaint with the FDA in 2014. So far they have taken no action to get it resolved. So this problem will only get fixed by having every diabetic who gets bubbles complain to both Medtronic and to the FDA.