Arterial Line Versus Cuff Pressure

jamie · Aug 3, 1999

When I have a pt. with an A-line I first make sure that I zero the line and compare the A-line to a cuff pressure, both manually and by the automatic cuff. The pressure that is most accurate with my manual check is used.

I usually compare all three presures for at least three hours, as to leave a record to the physician and the nurse following me, so they can see why I chose the one I used for my entire shift.

Bruce · Aug 22, 1999

The last literature I read on the subject gave the nod to an automatic cuff as being the most accurate.

lyraesullivan · Sep 16, 1999

An arterial pressure should be the most accurate IF the transducer is level at the insertion site (not the plebostatic axis),if it has been properly zero'd, if you don't have overshoot or a dampened wave form. However, if the cuff pressure is higher, I would assume that the arterial line pressure is not accurate as it should be more sensitive than the cuff. Patients on a lot of pressors are vasoconstricted at the periphery and that can affect an artline that is radially placed.

AnnieCCRN · Dec 4, 1999

the latest research i've read in CRITICAL CARE NURSE and in other journals indicates that comparing artline to cuff pressure is similar to comparing apples to oranges.. as artline measures flow and cuff measures pressure.. performing the square wave test is now the gold standard for verifying accuracy of artline..

after stating that, however, i would hazard a guess that the artline pressure that is lower than your cuff pressure is probably inaccurate and will be reflected as such in the square wave test.. but at least you will be able to clearly document that the NIBP was used rather than artline after reviewing the square wave test.

in regards to leveling at the phlebostatic axis versus insertion site.. i have not seen decisive research supporting the insertion site over the phlebostatic axis.. would love to have the sources to support this change in practice.. please post when you have time..

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As he waited to be launched into space "Dear God, don't let me F#@% up!" Alan B. Shepard...we all have our moments of self doubt

tracy maietta,RN · Dec 23, 1999

Hi all, I was just wondering if anyone would explain to me the square wave test to determine accuracy of an art line. I am a fairly new nurse working in MICU and would appreciate the info!!!!!

Thanks.

SGRC · Sep 26, 2000

Arterial lines are the most accurate BP's to compare them with peripheral pressures of any kind is comparing apples to oranges. If you have a good square wave then the pressure is accurate. I learned this after a class on hemodynamics with Tom Ahrens who literally wrote the book on this subject! He stated what if that chart went to court how would you explain how you picked the BP.

Stormy · Nov 28, 2000

Interesting comments....I am interesting in hearing what the references are for the various practices mentioned. We are in the process of revamping our arterial line procedures, and I was unable to come up with a lot of information. Most of us tend to use the arterial pressure over the cuff pressure so long as the waveform is not damped. We utilize the "square wave test" as well, which will indicate damping or overshoot of your waveform.

dka · Dec 5, 2000

[i have done a lot of research on this subject as well. There is a division of theroies on this subject. One says this the other says that. I have found one article in Critical Care Research suggests go by the MAP. Ever since I have found this info I experienced very little descrepency in the numbers. The zeroing site is extremly important. Be it cath tip or phleb axis.

hollykate · Dec 5, 2000

Our critical care policy hospital wide states to start the shift by taking a manual and the A line pressure. If they are within 14 points of each other, we are to use the a line, as long as the wave also looks appropriate and has a good square wave test. I often have patients with difficult blood pressures, and I often finally explain what I am getting with the two (a line and Cuff)and ask the MD which pressure he would like me to use. I then document that the MD made the decision and why.

and for tracy from GA- the square wave test, you pull on the fast flush line for a second or two and see the wave flatten out then you let go, the wave should zip down below baseline and rapidly come up to baseline. This is in every critical care textbook out there.

I do agree zeroing and manipulating the line so you are getting a good wave seems to make an enormous difference.

johnboy · Jan 26, 2001

It's been a couple of years since I attended the Ahrens class, but I agree I remember him stating that NIBP cuffs measure "flow" and art lines measure "pressures": as said previously, comparing apples and oranges. The square wave test should help in your decision.

Another thing does stick out in my mind that he said: don't put down both NIBP and art line pressures on the chart, because if the chart went to trial, the lawyer might try make you look "unsure" of what you were doing. Pick one, document why you did it over the other, and stick with it. And (i'll be the first to admit i never do this), try to get your square wave test documented on your strip containing the art line waveform! It's just another good piece of documentation about your waveform and BP!!

icu-nurse · Apr 21, 2001

I think I read one person say a-line measures flow and cuff pressure, and someone else say the opposite. Which is it? It seems to me the cuff would measure pressure and the a-line flow.