IUPCs and baseline uterine pressure
Ok folks – I gotta a braintwister for us all.
I was on call this morning and the nurse was letting me know that a patient with an IUPC had a baseline pressure of 40 mm Hg, and anything above 30 mm Hg was considered abnormal. I didn’t know what to say to that, because the whole idea of baseline pressure never made sense to me.
First, the IUPC is zeroed theroetically to the air, so the baseline pressure should be relative to air. But, we have no idea what intraabdominal pressure is! When we do urodynamics we need to subtract intraabdominal pressure from the bladder pressure to really understand how hard the detrusor is contracting. It seems to me that we would need the same information to say anything meaningful about the intrauterine pressure in an absolute sense. Otherwise, the baseline pressure could be influenced by things like patient position and position of the baby (making a different amount of direct pressure on the IUPC.) The whole concept seems sort of flawed to me.
Certainly if baseline uterine tone were really increasing, that might have some meaning. But are we really measuring what we think we are measuring?
So what did I tell the nurse? I said “don’t worry about it. the whole concept makes no sense.”
What would you have told her?