I'm sure this has been discussed many times on this site, but here goes......I have been in the MS ICU for about 6 months, and don't have a lot of experience with hemo monitoring with A-lines, Swanz, etc. We just don't get many patients that critical who need them, and when we do, they go to the more experienced nurses. I have had maybe 3 patients who have had A-lines. I have asked the more experienced nurses for help in setting up, leveling, and zeroing the A-line, and have repeatedly been told to level the transducer to the insertion site rather than the phlebo axis.I really trust and respect these nurses, but tried to do some research to support what they were telling me. However, all I could find was to level all lines (Art, CVP, Swanz) to the phlebo axis. Last night, I had a post-brain biopsy pt who had an A-line that I leveled to the radial artery. She also happened to be laying on her side on that same arm with the BP cuff on the opposite arm. Anyway, her A-line and cuff pressures in no way correlated. Her cuff pressure was like 120-130 and her A-line pressure was 170-190. I'm assuming the A-line pressure was artificially high since she was laying on that arm, and her cuff pressure was artificially low since it was on the upper arm.And, as a theoretical question, if leveling to the A-line insertion site, I am assuming the pressure reading would be an accurate measurement of blood pressure AT THE INSERTION SITE. But, if leveled to the phlebo axis, the BP reading would be an artificial APPROXIMATION of central pressure due to the effects of atmospheric pressure on the transducer. Does that make sense? And, if so, why would we want an APPROXIMATION when we can have an ACTUAL? Thanks all!