bubbles in resevoir

The blue piece provides direct connectivity between whatever is on each side. If you are getting air in as you disconnect from the vial, this is an indication of negative pressure in the reservoir, which will suck air in as you disconnect the vial. There are several ways to take care of this, some of which have been mentioned already, but I will repeat them here because (in my opinion) this is the best remedy for the issue you have described:

1) Make sure you are putting in as much POSITIVE pressure into the system as possible. This means treating the reservoir like a syringe and filling it with air before attaching to the vial. Unfortunately (for this but fortunately for breathing), air is compressible so this is not perfect, but make sure you pull the plunger back to the point where the o-ring is visible before you push the air into the vial, putting as much air into the system as possible.
2) Actually, I skipped another important piece. Make sure you do not have residual negative pressure in the vial. The symptom of this would be a concave rubber top, drawn in by the pressure. The easiest thing to do, pressure-wise, is to remove the reservoir plunger completely while the vial and reservoir are connected via the blue bridge, with the flat part of the vial resting on a counter. This will balance the pressure. Then, putting the plunger back in will pressurize the vial system.

3) Fill your reservoir.

4) Eliminate bubbles, place the flat part of the vial on a counter top and remove the RESERVOIR from the system. By removing the reservoir, you are doing 2 things:a) "sealing" the reservoir as it is removed so no air can be drawn inb) opening the vial to air, enabling a compensation for negative pressure.

Warm regards,