Which blood pressure reading is correct?

snowyRN · May 11, 2009

I would think it would be the arterial line, I dont work in an ICU but this would be my first bet.

GOMER42 · May 11, 2009

Art line is the most accurate

They usually don't match up because the art line is a direct measurement, and it may read 15 more than the indirect cuff measurement.

Music in My Heart · May 11, 2009

Think about it this way:

The pressure from the arterial line is a direct measurement of the pressure inside the vessel by a transducer.

The pressure from a sphygmomanometer is the external pressure applied to the vessel which causes turbulent flow in the blood which can be discerned though auscultation or detected with an external pressure transducer. It is variable and depends on the size of the cuff, the location of the cuff, the patient's anatomy, and the means utilized to sense turbulent flow or pulsating pressure.

mommyX2 · May 11, 2009

What about a dynamap and a manual bp?

azhiker96, BSN, RN · May 11, 2009

What about a dynamap and a manual bp?

I trust my manual BP more than the dynamap. I've had patients where the dynamap couldn't deliver a blood pressure. The patient was talking so I was pretty sure they had pressure. For whatever reason the dynamap wasn't able to "hear" the Korotkoff sounds.

Regarding invasive versus non-invasive, there are a lot of factors. Radial art lines are often positional just like PIVs in the AC. You've got to make sure you have a good waveform before you trust it too much. Non-invasive have problems too as was mentioned, large arms, cuff size match/mismatch, etc.

WalkieTalkie, RN · May 11, 2009

You also need to consider the waveform of the artline. If it is overdampened or underdampened, you may see a false reading.

Here's a good explanation: http://co-5.college-online.com/lisa_conry/ARTERIAL%20PRESSURE%20MONITORING.doc

CABG patch kid, BSN, RN · May 11, 2009

There are a lot of factors that can affect both the invasive and noninvasive BP. Being a new CCU nurse, one of the things that I'm learning is that a lot of your time can be spent trouble-shooting equipment and making sure that the numbers you are referencing are accurate.

At the beginning of the shift, its always a good idea to make sure your transducers are at the patient's phlebostatic axis and secured, make sure the line flushes (do a square test), then zero the monitor. If its a radial art line, make sure the pt's wrist is in good position and the armboard is tight. Also look at the tubing to make sure that there are no air bubbles, and that your flush bag is full and the pressure bag is pumped up. Then check your cuff (size, location, pt's arm position) then look at your numbers to see if they correlate. If they are still a bit off, I'd just go ahead and document both numbers at all times so the other people can make their own interpretation of it.

Normal, accurate arterial BP does naturally run higher than cuff pressure. If I remember correctly, a difference of 15mmHg is okay.

If I was going to be titrating pressors on a pt and there is a big difference between the two, I would let the doc know and see what he prefers. Some would just prefer that you use the lowest number or the highest number; depends on the pt and what's going on with them. It can also depend on the doc, lol.

I hope that somewhat answers your question!!

bill4745, RN · May 11, 2009

And the aline is not accurate unless it is leveled.

WalkieTalkie, RN · May 11, 2009

If you're really interested in this sort of thing, this website is really good in teaching hemodynamic monitoring: http://www.pacep.org/

bethh1970 · May 11, 2009

What about a dynamap and a manual bp?

The manual read should be more accurate. When I get my vitals and the bp appears to be off I get a manual and let the doc know what that is. Actually, most docs ask if "off" bp's are manual or machine.

UofMRNBSN · May 11, 2009

A rule I live by... If the waveform looks good and your square wave test is good, then go by the art line. What I was taught is that an arterial line measures pressure directly a cuff measures pressure indirectly by measuring flow.