How do you calculate your CVP's?

Specialties MICU

Published

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?

Specializes in CVICU.
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.

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.

If you get good at doing it the way I posted, sometimes you can ballpark it by looking the monitor, even if the monitor displays the wrong number, like -3.

Specializes in Critical Care, Education.

1. 300mmHg pressure in pressure bag. Be sure there is saline in it.

2. Patient supine(if you can and HOB 0 to 45 degrees. I say

3. Zero transducer to phlebostatic axis (4th intercostal space/ mid thoracic line)

4. Print ECG + CVP. Use a scale where the tops or bottoms of the waves aren't lopped off.

5. Determine end-expiration by the oscillating of the CVP baseline.

6. Read the max and min of the a wave (just after the p wave on the ECG.

7. Calculate min +max /2 which gives the mean. unless a fib. Otherwise:

8. Alternatively look for the c wave (notch) below or just behind the R wave on the ECG. This is the Z point and is where the tricuspid valve closes and is therefore the RVEDP. (Which is afterall the definition of preload.)

Note: There is no systolic or diastolic to read because there is no valve in front of the venacava/ right atrium, just minimum and maximum pressures. The a wave is the active filling of the right ventricle which is why you find it behind the P wave. For every inch the transducer is above the phlebstatic axis the pressure will be 2 mmHg too low and visa-versa. Read at end expiration if spontaneously breathing or vented. PEEPS > 10 raise the CVP because of the increase in transmural pressure. I hope this helps.

Specializes in ICU and EMS.

If you don't mind, I have another question to add. I was always taught that CVP should only be measured from a central line such as an internal jugular or sub clavian triple lumen. The other day I was asked to get one from a brachial PICC. The waveform was terrible and the reading I got did not seem appropriate. The rationale that I got from the MD was that "Power PICCs" should be able to get CVPs. Does anyone else get CVPs from PICCs?

Specializes in Critical Care, Education.

The CVP from a picc should read high I am told, but there is literature that defends its use. The problem is the length of the tubing. The longer the tubing greater than 4 feet the more damping of the dynamic response. Even though the picc is in the body, it is still 10 + inches long, and it is distensible tubing. The system must be of low compliance tubing. So you've added a foot of stretchable tubing with the picc. So a cvp with a picc may not be completely accurate, but it is precise. In otherwords the error in reading is the same error each time. Therefore, it can be used for trending with confidence. IMHO.

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