Please Refer to the Supplementary File As Online Resource 1

Please refer to the supplementary file as Online Resource 1.

Information provided by the analysis of the arterial pressure waveform

The analysis of the arterial pressure wave shape using specific devices (PiCCO™, LiDCO™, and Vigileo™) has been recently developed in order to obtain a real-time CO monitoring. A mathematical analysis allows the transformation of an arterial pressure curve into a flow or a stroke volume. The first two systems require calibration using an independent method of cardiac output measurement (lithium dilution for the LiDCO™ system, transpulmonary thermodilution for the PiCCO™ system). The third system (Vigileo™) uses demographic information and a database of known waveform parameters.

The LiDCO™ system’s algorithm is based on the principle of mass and power conservation [1]. The system analyzes power and mass variations which are reflected by volume variations. SEV determination is based on lithium dilution, allowing assessment of arterial compliance. Implementing the system requires both a central or peripheral venous catheter as well as an arterial catheter.

The PiCCO™ system algorithm, based on the Windkessel principle, analyzes the arterial pulse wave shape [2]. System calibration is based on cold bolus (<8 C) transpulmonary thermodilution. The arterial catheter is equipped with a thermistance that measures the temperature changes induced by the injection of a cold bolus through a central venous catheter. Calibration requires three cold bolus injections and must be repeated regularly so as to ensure measurements’ reliability [3]. Cardiac output is assessed continuously based on the analysis of the systolic part of the BP curve.

The Vigileo™ device is based on statistical analysis of the shape changes of the arterial pulse wave. The arterial catheter used contains a transducer able to sample the BP wave at a frequency of 100 Hz. The algorithm compares PP standard deviations at each beat and incorporates patient demographical data (age, weight, height, and gender) [4].

PiCCO™ and LiDCO™ systems have been validated in comparison with pulmonary arterial catheterization [5, 6]. The validity of the Vigileo™ system is still questionable in particular in patients with sepsis and/or receiving norepinephrine [7, 8].

More detailsof the principles, the validation studies, the advantages and the limitations of each systemhave been well described in previous review articles[9-11].

1.Chatti R, Cholley B, (2007) Les nouvelles techniques de monitorage du débit cardiaque : gadgets ou avancées réelles. Réanimation16: 156-62.

2 .Woods AR (2009) Analyse de l'onde de pouls. In : Richard C, Teboul JL, ed. Insuffisance circulatoire aiguë. Arnette, Paris pp. 193-204.

3. Hamzaoui O, Monnet X, Richard C, Osman D, Chemla D, Teboul JL, (2008) Effects of changes in vascular tone on the agreement between pulse contour and transpulmonary thermodilution cardiac output measurements within an up to 6-hour calibration-free period. Crit Care Med 36: 434-40.

4. Morgan P, Al-Subaie N, Rhodes A, (2008) Minimally invasive cardiac output monitoring. Curr Opin Crit Care 14: 322-326.

5. Costa MG, Della Rocca G, Chiarandini P, Mattelig S, Pompei L, Barriga MS, et al, (2008) Continuous and intermittent cardiac output measurement in hyperdynamic conditions : pulmonary artery catheter versus lithium dilution technique. Intensive Care Med 34: 257-263.

6. Sakka SG, Reinhart K, Meier-Hellmann A, (1999) Comparison of pulmonary artery and arterial thermodilution cardiac output in critically ill patients. Intensive Care Med25: 843-846.

7. Sakka SG, Kozieras J, Thuemer O, van Hout N, (2007) Measurement of cardiac output : a comparison between transpulmonary thermodilution and uncalibrated pulse contour analysis. Br J Anaesth 99: 337-342.

8. Monnet X, Anguel N, Naudin B, Jabot J, Richard C, Teboul JL, (2010) Arterial pressure-based cardiac output in septic patients: different accuracy of pulse contour and uncalibrated pressure waveform devices.Crit Care;14:R142.

9.Morgan P, Al-Subaie N, Rhodes A, (2008) Minimally invasive cardiac output monitoring. Curr Opin Crit Care 14: 322-326

10.de Waal EE, Wappler F, Buhre WF, (2009) Cardiac output monitoring. Curr Opin Anaesthesiol 22: 71-77

11.Mayer J, Suttner S, (2009) Cardiac output derived from arterial pressure waveform. Curr Opin Anaesthesiol 22: 804-808