Eli5: why does an IV drop into that capsule that’s half full of iv and half air?

Question

Eli5: why does an IV drop into that capsule that’s half full of iv and half air?

In: 1726

Answer 1

I have a follow up question; if I may…-

Why is that capsule that is half full of IV and half full of air ALWAYS half full until the bag is finished??

To explain:
If I stop the flow by interrupting the line BELOW the chamber, by accidentally sitting on it, twisting it etc. then the chamber stays half full, and the bag above stops dripping into the chamber, right?

WHY doesn’t the chamber just fill up with the IV fluid? There’s a blockage downstream after all…?

(I’ve just started having therapy needing regular day long IVs in clinic)