This is how I change my cartridge:
1. Open new cartridge and use syringe to pull air out of new cartridge until the plunger is harder than normal to pull.
2. Pull up room temp insulin into 3ml syringe being careful to avoid creating bubbles in the syringe. I find that pulling it up until there is a discernible bubble at the top of the syringe and then pushing that bubble back into the bottle until there is ONLY insulin in the syringe before finishing filling the syringe cuts way down on the air in the syringe.
3. I use Animus insets for the most part so at this point I would insert the new cannula and then disconnect the tubing from the set.
4. Pull up 50-100u into another syringe using the same technique as #2.
5. Finish changing the cartridge in the pump per SOP (do you flick the back of the pump while it's removing air and priming the pigtail to encourage bubbles to the top?) and prime the pigtail until there are no bubbles in the pigtail and a bubble free meniscus at the top of the luer lock. Do not "end" filling at this point but just leave it be for just in case.
6. Detach needle from the 50-100u syringe and attach to the luer lock of the tubing and use that to prime the tubing. Remove the syringe from the tubing and return the needle to the syringe and use the needle end to finish filling the tubing side of the luer lock, flicking away any small bubbles in the lock as the lock is filled, until there is a bubble free meniscus on the tubing luer lock.
7. Attach the tubing to the pigtail. If you've kept the tubing and lock bubble free and made sure there is a meniscus on both sides there will not be any bubbles at all. Examine the tubing to make sure there are no bubbles, they should have been primed out manually with the syringe but make sure. If you are bubble free then finish the fill at the pump.
8. Attach the tubing to the site and prime the cannula.
This process is the only way I've been able to prevent ALL air from getting in my tubing or lock.