Question

What is the measure of npo

Answer 1

It would be much much easier to answer this question
if we knew what "npo" means.

Last time I was in the hospital, "npo" meant "non per oro".
That's Latin for "nothing by mouth".  It's the way the doctor
tells the nurses "Don't give him anything to eat or drink".

So in that case, the measure of "npo" is zero.

If you mean something else by "npo", you'll have to come back
and tell us what it means.