My vents never change. I have what is called as non compliant vents. Usually the only way to show truely if a shunt is flowing and working is to have a shunt flow study. It's a scan that takes about an hour and a half. They watch it drain from your head to the distal end. I'm bad to not check my message boards as much since most of my hydro peeps have a facebook or myspace...Feel free to add me
Monica Ball on facebook or www.myspace/monica_denice