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Highly Accessed Letter

Pulse pressure variation, stroke volume variation and dynamic arterial elastance

Raphael Giraud, Nils Siegenthaler and Karim Bendjelid*

Author Affiliations

Medecin Adjoint Agrégé, Division des Soins Intensifs, Hôpitaux Universitaires de Genève, CH-1211 Genève 14, Switzerland

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Critical Care 2011, 15:414  doi:10.1186/cc10088


See related research by Monge García et al., http://ccforum.com/content/15/1/R15

The electronic version of this article is the complete one and can be found online at: http://ccforum.com/content/15/2/414


Published:23 March 2011

© 2011 BioMed Central Ltd

Letter

We read with interest the recent article by Monge Garcia and colleagues [1]. We have two comments regarding this interesting physiological study.

First, although we support their observation [2], their explanations may lead to some confusion. Indeed, the Edwards Vigileo™ system-FloTrac™ sensor calculates stroke volume (SV) using the equation:

where σAP is the standard deviation of the arterial pressure (AP) curve and Khi a constant quantifying arterial elastance and vascular resistance [3]. As stroke volume variation (SVV):

Which means that SVV (%) ≈ pulse pressure variation (PPV; %) for FloTrac™.

With the present mathematical equation, it can be demonstrated that the SVV calculated by FloTrac™ (SVVFT) is not influenced by Khi, which means that SVVFT calculation does not include effective arterial elastance (Ea). The originality of Garcia and colleagues' finding is that they realized that when measuring PPV conventionally [4], the ratio PPV/SVVFT becomes a mirror of a dynamic Ea, as the conventional PPV selected integrates Khi (Figure 1). However, when the present innovative method is used, PPV and SVV should be sampled during the same period of time.

thumbnailFigure 1. Model of two different arterial elastances (Ea and Ea) on the pulse pressure variation (PVV) relationship curve, with the same stroke volume variation (SVV) value.

In conclusion, we believe that dynamic Ea predicting arterial pressure response to volume loading in preload-dependent patients is an interesting physiological concept. However, this demonstration cannot be achieved without taking into consideration the impact of PPV/SVV sampling.

Abbreviations

AP: arterial pressure; Ea: arterial elastance; PP: pulse pressure; PPV: pulse pressure variation; SV: stroke volume; SVV: stroke volume variation.

Competing interests

The authors declare that they have no competing interests.

References

  1. Monge Garcia MI, Gil Cano A, Gracia Romero M: Dynamic arterial elastance to predict arterial pressure response to volume loading in preload-dependent patients.

    Crit Care 2011, 15:R15. PubMed Abstract | BioMed Central Full Text OpenURL

  2. Bendjelid K: When to recalibrate the PiCCO? From a physiological point of view, the answer is simple.

    Acta Anaesthesiol Scand 2009, 53:689-690. PubMed Abstract | Publisher Full Text OpenURL

  3. Manecke GR: Edwards FloTrac sensor and Vigileo monitor: easy, accurate, reliable cardiac output assessment using the arterial pulse wave.

    Expert Rev Med Devices 2005, 2:523-527. PubMed Abstract | Publisher Full Text OpenURL

  4. Michard F, Chemla D, Richard C, Wysocki M, Pinsky MR, Lecarpentier Y, Teboul JL: Clinical use of respiratory changes in arterial pulse pressure to monitor the hemodynamic effects of PEEP.

    Am J Respir Crit Care Med 1999, 159:935-939. PubMed Abstract | Publisher Full Text OpenURL