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This article is part of the supplement: 29th International Symposium on Intensive Care and Emergency Medicine

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Plethysmography variability index: a new fluid responsiveness parameter

M Feissel1, R Kalakhy1, J Badie1, G Robles1, J Faller1 and JL Teboul2

Author Affiliations

1 CHBM, Belfort, France

2 APHP, Le Kremlin Bicetre, France

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Critical Care 2009, 13(Suppl 1):P205  doi:10.1186/cc7369


The electronic version of this article is the complete one and can be found online at: http://ccforum.com/content/13/S1/P205


Published:13 March 2009

© 2009 Feissel et al; licensee BioMed Central Ltd.

Introduction

New predictors of fluid responsiveness have been obtained from plethysmographic waveforms displayed on pulse oxymeters. However, they require recordings on a PC and offline operator-dependent analysis. A new parameter called the plethysmography variability index (PVI) has been proposed by a pulse oxymetry manufacturer to be used for the purpose of fluid responsiveness. Its advantage is that it can be automatically calculated and displayed on the screen of the pulse oxymetry monitor. The aim of the study is to test the accuracy of this parameter to predict fluid responsiveness in critically ill patients.

Methods

Inclusion criteria were septic shock patients fully adapted to their respirator and on sinus rhythm. Methods involved simultaneous recording of the following tracings: invasive blood pressure, plethysmography pulse oxymeter (Philips™), ECG, airway pressure and digit values inscribed on the device (Masimo™). Echocardiography was used to calculate the velocity–time integral (VTI). We infused fluid (500 ml saline) in patients with pulse pressure variation (ΔPP) ≥ 15% and performed passive leg raising (PLR) in patients with ΔPP <15%. We compared the PVI with ΔPP and with the variability of pulse oxymeter wave amplitude (ΔPPleth) and sought the best threshold PVI value that predicted ΔPP >15%. Patients who increased their VTI by more than 15% in response to fluid or to PLR were defined as responders. The significance of the PVI threshold to distinguish between responders and nonresponders was examined.

Results

In the first step 25 patients were enrolled. Fifty paired values were analysed. The r2 coefficients between ΔPP–PVI, ΔPPleth–PVI and ΔPP–ΔPPleth were 0.81, 0.79 and 0.74, respectively. A threshold PVI value of 20 identified patients with ΔPP >15% with a sensitivity of 84% and specificity of 90%. In a second step 18 other patients were enrolled. All patients with PVI >20 (n = 8) were fluid responders and 10 patients with PVI <20 were PLR nonresponders.

Conclusion

The PVI automatically obtained from a pulse oxymetry device seems an accurate index of fluid responsiveness. The numerical value of 20 distinguished responders from non-responders with good sensitivity and specificity.