Filling the reservoir

I had been facing some issues with bubbles in reservoirs of my insulin pump in the past. I used to follow the manufacturer's gudelines, remove the insulin bottle from the fridge and leave it in a place with room temperature before filling the reservoir. But the bubbles used to develop a few hours after the reservoir was filled. This was because the amount of air absorbed by insulin depends on temperature and pressure. The higher temperature insulin has the lower amount of air it contains. And the higher pressure insulin has the higher amount of air it contains. If the temperature rises or pressure drops after filling the reservoir, the air is released from the insulin creating bubbles. The dependency on temperature is well known but the dependency on pressure is not. To avoid bubbles in the reservoir, pressure in the reservoir and the connected insulin bottle has to be kept lower than the atmospheric pressure during the whole process of filling the reservoir.

I recommend using the procedure described below when filling the reservoir. Please note that the reservoir should be kept in the vertical position during the whole process:
  0. Remove the insulin from the fridge and leave it at room temperature for some time.
  1. Unpack the reservoir, attach the needle (if not attached already) and move the piston up and down several times. Rotate the piston when moving it. This helps to spread the lubricant on the inner wall of the reservoir evenly.
  2. Pull the piston down to fill half of the reservoir with air.
  3. Connect the insulin bottle to the reservoir.
  4. Pull the piston down to the maximum position to soak up insulin into the reservoir.
  5. Push the piston up to squeeze the air from the reservoir to the insulin bottle. Make sure you keep at least a half of the reservoir filled with insulin and air.
  6. Repeat steps 4 and 5 until there is no air left in the reservoir with exception a few bubbles that may reside on the inner wall of the reservoir.
  7. Knock on the reservoir to move all bubbles to the very upper part of the reservoir. Push the piston up until all the bubbles are squeezed to the insulin bottle.
  8. Pull the piston down to the maximum position. If there are still some bubbles left, repeat steps 7 and 8.
  9. Disconnect the insulin bottle from the needle. This aligns pressure in the reservoir and needle to the atmospheric one.
10. Disconnect the needle from the reservoir and connect it to the insulin bottle. This aligns pressure in the insulin bottle to the atmospheric one and prepares the bottle for filling of the next reservoir.
11. Connect the tubing, mount the reservoir into the insulin pump and prime. When starting to prime, continue to keep the pump in the vertical position and knock on it. This helps to release air bubbles that may appear in the area where the tubing is connected to the reservoir.