Hi
Air bubbles in the cartridge are a problem for most pumpers..... they drove me round the twist with frustration until a lovely person posted a common sense message which went along the lines of if you position the tube so that it's always at the bottom of the cartridge when you have the pump on your body, then the air bubbles will always rise to the other end of the cartridge and not go down the tube...... so that's a good get out of trouble tactic to use.......Put pump in baby sock and shove in side of bra cup will also make it that any bubble in cartridge wont go down the tube.
I always fill the cartridges up with insulin straight from the fridge but do this when the pump gets down to the last 30u and then shove the cartridge in my bra for about 12hrs so it gets up to body temp and not just room temp. I then screw in the blue plunger and gently flick the cartridge with my thumb nail and hold it slightly diagonal so that the bubble will line up under the luer neck and then push the plunger up and quickly remove the cartridge cap holding a piece of tissue (to catch any insulin) around the luer neck so that the bubble can come out the top of the cartridge and then quickly push on the black tube connector with a new tube already screwed in and then push that on top of the cartridge. I then keep the cartridge and tube in an upright position and hold it alongside the pump and then advance the piston in the pump upwards (button on the side of the pump) so that there is about a 10u gap between the top of the piston and the bottom of the cartridge.... ie if you fill the cartridge up to 150u, advance the piston to 160u to allow for the 10u gap. I have found that creating a gap enables the piston to gently glide upwards to prime the tube and ensures that an air bubble doesn't mysteriously appear and once insulin is primed through the tube, you are good to go..... All that you have to do then, is keep an eye on the level of insulin in the cartridge as the pump will register 30u left when there is only 20u but this just a small price to pay in order to be ok with the bubble problem and then you can position the pump on your body in any direction that you want.
Hope this makes sense