EVD/ICP monitoring??

Hi guys- I posted this on the Neuro ICU thread- wanted your opinion too!

Ok all you Neuro ICU RNs- need some help here. So, I'm on my last day of orientation and my preceptor has to leave early today. So I continue on and give report to this "not so welcoming" RN that releived me. Let me first say that neurosurgeries are new to this unit, however, I have worked with head trauma pts with EVDs at previous jobs. Anyway, this pt had an EVD set at +20 open to continuous drain. - not a camino- just a simple EVD drain. I was always taught that you either drain or monitor- not able to do both at the same time. You are off to the transducer and open to drain, then to get an accurate ICP you turn the drain off and then get your waveform and ICP number. That being said, as you are draining, your transducer is off- right?
The oncoming nurse got her panties in a wad because the alarm was off- (because you are not able to continually monitor) so- the number on the monitor is not accurate unless the stopcock is off to drain and such there is no need to alarm a number that is not accurate right?
So, she is telling me that you can monitor trends and you should not need to turn the stopcock to get a reading. How can you monitor a trend when you are off to the transducer? Am I completely nuts? Have I had it all wrong? I know you can do continuous monitoring via camino. But this is just a simple drain.