Pulse pressure variation, stroke volume variation and dynamic arterial elastance

  • Raphael Giraud1,

    Affiliated with

    • Nils Siegenthaler1 and

      Affiliated with

      • Karim Bendjelid1Email author

        Affiliated with

        Critical Care201115:414

        DOI: 10.1186/cc10088

        Published: 23 March 2011

         

        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:
        http://static-content.springer.com/image/art%3A10.1186%2Fcc10088/MediaObjects/13054_2011_9357_Equa_HTML.gif
        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):
        http://static-content.springer.com/image/art%3A10.1186%2Fcc10088/MediaObjects/13054_2011_9357_Equb_HTML.gif

        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.
        http://static-content.springer.com/image/art%3A10.1186%2Fcc10088/MediaObjects/13054_2011_9357_Fig1_HTML.jpg
        Figure 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.

        Declarations

        Authors’ Affiliations

        (1)
        Medecin Adjoint Agrégé, Division des Soins Intensifs, Hôpitaux Universitaires de Genève

        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.View Article
        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.PubMedView Article
        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.PubMedView Article
        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

        Copyright

        © BioMed Central Ltd 2011

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