There are numerous methodologies that we can utilize to determine fluid responsiveness in our critically ill patients in the emergency department or in the intensive care unit. In this post, I will be taking a deep dive into pulse pressure variation, PPV as the shorthand. For details about the other methods for determining fluid responsiveness, CLICK HERE.

If you use contents from this post on your own work, please cite this post as:
Eddy J. Gutierrez, “Fluid Resuscitation in Sepsis and Volume Responsiveness”, eddyjoemd blog, October 27, 2021. Available at: http://eddyjoemd.com/pulse-pressure-variation.

What is Pulse Pressure Variation (PPV)?

Pulse pressure variation (PPV) is a dynamic parameter for fluid responsiveness that incorporates the heart-lung interaction in patients on mechanical ventilation with an arterial line to predict if a patient needs additional volume/IV fluids. It is based on the principle that changes in intrathoracic pressure during mechanical ventilation can affect cardiac preload and stroke volume, and thus alter the pulse pressure.

In patients who are responsive to fluid administration, an increase in cardiac preload will result in an increase in stroke volume, which will be reflected in a corresponding increase in pulse pressure. Conversely, in patients who are not responsive to fluid administration, an increase in cardiac preload will not result in a significant increase in stroke volume or pulse pressure.

When did we learn that pulse pressure variation appropriately predicts fluid responsiveness?

The first analysis on pulse pressure variation that I could find was by Michard et al. in the Blue Journal circa 2000. This was the publication where it was determined that “the threshold ΔPp value of 13% allowed discrimination between responder and non-responder patients with a sensitivity of 94% and a specificity of 96%”. The areas under the ROC curves (±SE) were 0.98±0.03 for ΔPp in that study.

What is a normal pulse pressure variation (PPV)?

As mentioned, Michard et al. determined that using a PPV of 13% “allowed discrimination between responders and nonresponders with a sensitivity of 94% and a specificity of 96%”. So if the variation is ≤ 13%, then the patient likely does not need additional fluids.

What are the Limitations of Pulse Pressure Variation?

Patient needs to be on mechanical ventilation to enact the heart-lung interaction. They cannot be taking spontaneous breaths which means they need to be deeply sedated or paralyzed. Then, the tidal volume needs to be set at ≥ 8cc/kg of ideal body weight. Typically, we try to keep the the tidal volume at 6cc/kg IBW but one may quickly adjust this to obtain a better result. If the patient has an arrhythmia, this test is a no-go. In addition, the patient will need to have an arterial line to obtain the proper waveforms to analyze (Monnet et al.). The data has described using a radial or femoral line but the others should get the job done as well.

Can Pulse Pressure Variation be used on patients on Pressure Support or breathing over the vent?

Going back to the limitations mentioned before, there is some data from Grassi et al. that it could be used in patients on pressure support as well as those who are on mechanical ventilation and breathing at rates 20% above the set respiratory rate on the ventilator. In my career, I have no attempted PPV in this patient population because I do not have patients who I am actively resuscitating on pressure support, and generally speaking, I attempt to match their respiratory drive to avoid fatigue and other issues. They did find that the “receiver operator characteristic curve for pulse pressure variation was 0.87 (95% CI 0.74-0.99; p<0.0001) and the grey zone limits were 10% and 15%”. This has not been replicated, that I know of.

How do we know it does not work in spontaneously breathing extubated patients?

Heenan et al. performed a trial where they attempted to use PPV on patients who were spontaneously breathing on a face mask. Here, they found that “the ROC curve area of ΔPP… was 0.29 ± 0.17 in patients breathing through a face mask”. This AUC is not reliable. We should not use it.

Does using Pulse Pressure Variation actually work to predict fluid/volume responsiveness?

A meta-analysis by Yang et al. took a deep dive into 22 studies and 807 patients. They found that the AUC of using PPV to determine fluid responsiveness was 0.94 which is considered to be outstanding. Gold standard-type stuff.

How to set up PPV on your monitor.

The term “multi parametric monitor” is thrown around here so that we don’t have to whip out the rulers and start measuring things by hand like in the old days. The best image I have found of what the waveform tracings would look like when we change the sweep speed from 25mm/s to 6.25mm/s was published by Bronzwaer AS et al. I cannot show it here for copyright reasons. For the sake of simplicity, thankfully, multiple monitors now possess the software to be able to calculate the pulse pressure variation for us. Although one cannot forget the limitations that make it inaccurate.

Can you just eyeball the monitor to determine Pulse Pressure Variation?

No, Rinehart et al. performed a study where they found that we aren’t as good as we hoped we are at determining pulse pressure variation just by looking at the monitor. One actually has to calculate the numbers.

Final Thoughts

As I’ve mentioned before, finding perfection in fluid responsiveness is impossible which is why one needs to choose their method of performing these assessments based on their patient. One can use other parameters such as stroke volume variation, end-expiratory occlusion, or one of the various others in my compilation post on fluid responsiveness.

Citations

Michard F, Boussat S, Chemla D, Anguel N, Mercat A, Lecarpentier Y, Richard C, Pinsky MR, Teboul JL. Relation between respiratory changes in arterial pulse pressure and fluid responsiveness in septic patients with acute circulatory failure. Am J Respir Crit Care Med. 2000 Jul;162(1):134-8. doi: 10.1164/ajrccm.162.1.9903035. PMID: 10903232.
Link to Article
Link to FULL FREE PDF

Heenen S, De Backer D, Vincent JL. How can the response to volume expansion in patients with spontaneous respiratory movements be predicted? Crit Care. 2006;10(4):R102. doi: 10.1186/cc4970. PMID: 16846530; PMCID: PMC1750965.
Link to Article
Link to FULL FREE PDF

Michard F, Lopes MR, Auler JO Jr. Pulse pressure variation: beyond the fluid management of patients with shock. Crit Care. 2007;11(3):131. doi: 10.1186/cc5905. PMID: 17521454; PMCID: PMC2206397.
Link to Article
Link to FULL FREE PDF

Yang X, Du B. Does pulse pressure variation predict fluid responsiveness in critically ill patients? A systematic review and meta-analysis. Crit Care. 2014 Nov 27;18(6):650. doi: 10.1186/s13054-014-0650-6. PMID: 25427970; PMCID: PMC4258282.
Link to Article
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Citations Continued

Rinehart J, Islam T, Boud R, Nguyen A, Alexander B, Canales C, Cannesson M. Visual estimation of pulse pressure variation is not reliable: a randomized simulation study. J Clin Monit Comput. 2012 Jun;26(3):191-6. doi: 10.1007/s10877-012-9359-8. Epub 2012 Apr 11. PMID: 22491961.
Link to Article (NOT FREE)

Umbrello M, Formenti P, Galimberti A, Curti M, Zaniboni M, Iapichino G. On-line measurement of systolic pressure variation and pulse pressure variation on a multiparametric monitor. Intensive Care Med. 2008 Feb;34(2):386-7. doi: 10.1007/s00134-007-0913-7. Epub 2007 Oct 25. PMID: 17960363.
Link to Article
Link to FULL FREE PDF

Bronzwaer AS, Stok WJ, Westerhof BE, van Lieshout JJ. Arterial pressure variations as parameters of brain perfusion in response to central blood volume depletion and repletion. Front Physiol. 2014 Apr 23;5:157. doi: 10.3389/fphys.2014.00157. PMID: 24795652; PMCID: PMC4006039.
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Michard F, Chemla D, Teboul JL. Applicability of pulse pressure variation: how many shades of grey? Crit Care. 2015 Mar 25;19(1):144. doi: 10.1186/s13054-015-0869-x. PMID: 25887325; PMCID: PMC4372274.
Link to Article
Link to FULL FREE PDF

Teboul JL, Monnet X, Chemla D, Michard F. Arterial Pulse Pressure Variation with Mechanical Ventilation. Am J Respir Crit Care Med. 2019 Jan 1;199(1):22-31. doi: 10.1164/rccm.201801-0088CI. PMID: 30138573.
Link to Article
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Disclaimer

A hat tip to all these authors for their great work in looking into fluid resuscitation and volume responsiveness. Although great care has been taken to ensure that the information in this post is accurate, eddyjoe, LLC shall not be held responsible or in any way liable for the continued accuracy of the information, or for any errors, omissions or inaccuracies, or for any consequences arising therefrom.