# How do you calculate your CVP's?

1. There's a million methods to it, I have my own way but I've seen some absolutely horrendous ways people have done them. What's yours?
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Joined: Mar '09; Posts: 416; Likes: 324
RNAS; from US

3. Ok this is going to sound dumb, but I look at the CVP monitor, after zeroing & flushing it, if the patient has one! No one has ever asked me to calculate it, nor have I learned how to as of yet.

lol
4. Quote from LoveActually
Ok this is going to sound dumb, but I look at the CVP monitor, after zeroing & flushing it, if the patient has one! No one has ever asked me to calculate it, nor have I learned how to as of yet.

lol

The number displayed by the monitor is nothing more than a mean central venous pressure. The CVP should be measured at end expiration (for non-PPV patients). Print a strip of your CVP and respirations, set your scale to the appropriate number based on what you CVP has been and then be sure to actually measure the CVP on the strip at end expiration. The best way to determine PAS/PAD is in the same fashion. But most people and most units just take the mean CVP given by the monitor.
5. I never trust what the monitor says unless there's very little fluctuation in the waveform (i.e. a straight line).

I'll wait for more responses before I post my method.
6. I guess until you post your answer, I'm not sure what you are asking about calculating. What do you mean you don't trust the number unless there is a straight line? If there is I straight line, I don't think my line is in the right spot....there should be fluctuation in the waveform, correlating with the EKG.

Interested to see your calculating technique.
7. I have found that as long as there is a nice pretty wave form our monitors have been very accurate at giving the correct value. I do agree with the end expiration is the point of measurement, but it is for both vented and non vented pt.
8. I was always taught to measure with the patient lying flat, supine and end expiration. The only way I think you can really do it really accurately is to either freeze the waveform on the monitor and find the correct mean at end expiration. But I dont see most people doing it that way. HOB is usually up, and people are recording it hourly and not measuring it supine. That was just the way I was taught.
9. This has come up a few times...meandragonbrett how do you know where to set your scale? This is the part that's always confused me, even more so when measuring wedge pressures (which we do VERY rarely).
10. Quote from OkieICU_RN
I guess until you post your answer, I'm not sure what you are asking about calculating. What do you mean you don't trust the number unless there is a straight line? If there is I straight line, I don't think my line is in the right spot....there should be fluctuation in the waveform, correlating with the EKG.

Interested to see your calculating technique.
I wouldn't trust a straight line either (I suppose using trust before was a bad word choice), but if you've got a comatose patient who is as stiff as a wooden plank and you can't move their head, you gotta go with what it shows. We actually had a patient like that the other night, big ol' dude too. His CVP wave was as flat as could be, but yet if you gave him some extra fluids it did change. Whether it was accurate or not, who knows.

My method is to print 2 strips; CVP and respirations, CVP and one cardiac lead. Look at the CVP and respirations first and determine end inspiration or expiration. Then line up your CVP's from both strips, laying all of the waves on top of one another like a mirror image. Run your mark from the end inspiration/expiration on the respiratory strip and align the a-wave to the PR interval.
Last edit by detroitdano on Feb 1, '10
11. Here's a pretty good site for CVP information I came across. You need PowerPoint to access it though.

http://www.uth.tmc.edu/anes/Assets/p...Monitoring.pps
13. Another question...really 2...

After reading this thread I was playing around with the monitor at work trying to print a strip with CVP and resp waveforms...couldn't get it. I asked someone and she used the cursor to find the lowest point in the waveform. It seemed to corretlate with end expiration - end expiration should usually be the lowest point in the CVP waveform, right?

Also, is anyone subtracting for PEEP > 5?
14. Quote from tri-rn
Another question...really 2...

After reading this thread I was playing around with the monitor at work trying to print a strip with CVP and resp waveforms...couldn't get it. I asked someone and she used the cursor to find the lowest point in the waveform. It seemed to corretlate with end expiration - end expiration should usually be the lowest point in the CVP waveform, right?

Also, is anyone subtracting for PEEP > 5?
If the patient is being mechanically ventilated, yes.

However, I have to admit that no one in my unit actually takes the time to measure out the exact mean of the a wave at end expiration and we just take what the monitor gives us. Unless theres a marked variation in pressure with the resp. cycle, I dont see why that should be a big deal. It seems to me that watching the trend of the number on the monitor should do the trick and usually does fit in with the clinical picuture.