German to English Medical Medical: Instruments CVC placement

I'm having some difficulty with this sentence, which concerns checking the proper intravenous placement of a CVC (central venous catheter):
The intravenous placement should be checked on the basis of the shape of a (wave?shaft?) which is (maintained?held?) by means of a calibrated (pressure converter?).

Here's the original:
Die intravenöse Platzierung sollte anhand der Form einer Welle, die mittels eines geeichten Druckumwandlers erhalten wird, überprüft werden.
What exactly do they mean here? TIA for any help.