Why can't a person push on a vp shunt reservoir if debris can't go into it?

Vp shunts: Hi, I am unclear about what you are asking as you seem to be referring to two different types of shunts. A VP shunt drains fluid from the patient's brain to their peritoneum. A shunt with a reservoir is a catheter between a patient's brain and an implanted reservoir, used to give medicines. It may be best to ask a neurosurgeon your question as they have the most expertise in this area.