Removing Air From A New Cartridge

Being a type 2 Diabetic my insulin to carb ratio is very high and when I fill a new cartridge for my T-Silm X2 I fill my syringe with 300 units of insulin. With the new fill procedure for the cartridge before installing it on the pump I have very little air space in my insulin filled syringe to remove the air from the new cartridge during the fill process. My question is can I use an unfilled syringe to remove the air from the cartridge and then fill it with insulin. Will this work for air removal since I don’t have much draw back room in my filled syringe for air removal?

Just to be clear, are you filling the syringe with insulin & then trying to withdraw the air from the cartridge? If so, you need to use an empty syringe to withdraw the air, then fill it with insulin to fill the cartridge.

The newer T-Slim X2 no longer uses the pump to push out the air before you fill the cartridge. Now you load the syringe and hold the new cartridge vertically in your hand and insert the needle in the port and draw the plunger all the way to the rear to pull out the air the then let go and all the plunger to reset back its original position. Then you withdraw the syringe and take care of getting the air and bubbles out of the insulin in the syringe. According to the T-Slim people this is the best and easiest way to remove the air and get out the bubbles, lol. As I said, I was using used the pump to push out the air after you installed the cartridge in my old T-Slim, but that was the was the hard way, right. I use 300 units of insulin and that just about fills the syringe totally up, leaving me very little drawback room to work with.

So, yes I am using a filled syringe of insulin and withdrawing the air from the cartridge per instructions from the T-Slim folks. That is the reason I ask if it would be OK to just use an empty syringe to withdraw the air from the cartridge and then just fill it and move on.

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The method that @Bob_Martin describes is exactly what the Tandem reps state during training. I asked the trainer, and got a so-so answer why I could not purge the air first then load the cartridge. I have tried both ways - purge then fill, and purge with full needle then fill. As someone who also fills their cartridge to the brim, I have experienced no difference in fill quantities with either method. For my own ease, I purge twice, then fill the syringe, then fill the cartridge. Not Tandems way, but easier for me.

Not sure what is the “proper” approach. But this is what we do for our Tandem t:slim X2 to get the air out.

  • Using an empty syringe, extract air from the empty cartridge. Insert the empty syringe into the cartridge. While inserted, gently pull back on the syringe to about the 300 mark. Holding the syringe at the 300 mark, remove the syringe from the cartridge. No way to really know how much air removed. Seems no downside to at least trying.

  • At this point, the cartridge is always kept vertical with the tube at the highest point. For the duration of the cartridge change operation.

  • Using the same syringe, we now fill it with 200 or 250 units of insulin. (We were doing 250 but our insulin need seems to have dropped a bit so using 200 now). While filling the syringe, remove reasonably obvious air by shooting back into the vial then drawing back out. Standard.

  • Insert the syringe containing insulin into the cartridge. As we are only putting in 200 or 250 units and have a 300 unit syringe, we have a bit of room in the syringe. The syringe still holds the insulin. Draw back gently on the syringe and hold it at the 300 mark for a few seconds. A few air bubbles will pop out of the cartridge and float the the top of the syringe. (As mentioned, the cartridge continues to be held vertical with the tubing at the highest point).

  • Ignore the air now in the syringe. (Which is at the highest point of the syringe and furthest away from the cartridge. Gently depress the plunger and insert all the insulin into the cartridge. When you get at the end, the air will start to move but there is so little air at this point that it is just not enough to clear the tip of the syringe and never makes it to the cartridge.

  • Again, continue to keep the cartridge vertical with the tubing at the highest point.

  • Prime the pump. We still have 1 box left of the Leur Lock connectors so we are priming at 16 units. My understanding from Tandem Tech Support is when we switch to the new t:lock connectors, we will probably be priming 11 units.

This seems effective.

My approach is to do the best I can and not overly focus on tiny air bubbles that I can not control.

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I usually fill to around 2.8 and I still like more room to get the air out so I fill the syringe to around 2.
Then remove air with the normal procedure.

I then set for the 2.8 amount and put the air into the vial and fill the syringe fully.

I think I will call and ask Tandem to repair and send my old T-Slim back since it removed the air after the cartridge was installed after I tap the button during the fill process. I would fall asleep before I got half way through Tim35’s suggested procedure, lol. I might just be able to survive your suggested procedure JHE6,

I have one other question. Why do you need any insulin in the syringe to remove air from the cartridge???


The description may have been wordy. I was trying to be detailed in the event anybody was interested.

Certainly if the procedure you have works for you that is great. That is ultimately all that counts.

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By the way Tim35 why would you only be priming with 11 units and not 16 units just because you start using the t:lock connectors. I use the t:lock 23" inset and I prime around 16 units. So I am not sure why you would be priming less just because you change locks. Just curious .

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I stand on my head and try to get air into the needle. It always ens up in the bottom of the vial. It is almost like opposites LOL

This is what I do, I will partially fill the syringe before removing air from the cartridge. After air is removed from cartridge I will finish drawing my desired insulin into the syringe.

I wonder why the difference, because I don’t seem to have any of these issues. I only get a few units worth of air out of my cartridges. Because of this the recommended Tandem procedure works best because the air bubbles essentially fill the void in the luer lock syringe connection, so I’m not wasting insulin. I must be getting all the air out because it only takes me 11.3 units to fill the 23" t:lock tubing I only fill about 200 units, though, so I could see why you’d want more room to force suction on the cartridge.

I used to just suck as much air out as possible with the empty syringe first, and that worked exactly the same. So if you prefer that, go for it. It doesn’t really matter if you get all the air out, though. So long as you hold the pump and tubing upright during the fill processed (I give mine a tap on the table just to make sure any bubbles make their way to the top), the air will always get pressed out first during the fill, and any early bubbles in the line should get worked out in the lock connection. All air left in the carriage does is falsely inflate the fill volume.

By the way, these full procedures sound complicated, but they’re just wordy descriptions of a very simple short action. So don’t be intimidated.

And the only reason Tandem changed the fill procedure was because the biggest complaint about Tandem pumps is the fill time. They were trying to shorten steps, though I think it didn’t work well for them. I’ve found the pump to be Jerry reliable, resilient, and effective no matter how it’s treated. I can’t tell you how many times I jumped the gun and popped a cartridge out before I was “allowed” without breaking anything.

Just suck as much air as you comfortably can/however you comfortably can and go, don’t worry about the specifics. The only critical detail is that the pump is upright during the fill so air can escape.

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