Hello, New to the forum, so apologies if this is not the correct sub-category. I am testing compliances of materials by filling balloons with different fluids. I do this by filling up a 30 mL syringe with fluid and placing it into an infusion pump set to infuse at a rate of 0.1 mL/min. The syringe is attached to a serial pressure transducer which is then attached to a 23 gauge needle inserted into a PE-50 catheter (350 mm long). The free end of the catheter is then implanted into the balloon. To secure the implantation, the end of the catheter is flared with a lighter to make a small lip, then it is placed into the balloon via a small hole and sealed using a purse-string suture. Following infusion I disconnect the catheter from the transducer and attach it to a 1 mL syringe and recollect the fluid. One thing that I noticed is that in a lot of cases I cannot extract the fluid and there is resistance while pulling the 1 mL syringe. I have checked that the end of the catheter is in the middle of the balloon and not sucking the wall of the balloon. I can understand that if the balloon is being emptied, the catheter tip might not be in the remaining fluid, but I see this issue when the balloon is full. I was curious to see if others might know what be happening and possible solutions to get around this issue. What I can think of: - flared catheter tip opening causing issues - air? - length of catheter - equilibration of air pressure when transferring to 1 mL syringe? Attached a pic of setup (green rectangle is pressure transducer): Any help is much appreciated!