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Performance of the FloTrac™/Vigileo™
- Friederike D Compton, Bianca Zukunft, Clemens Hoffmann, Walter Zidek, Juergen-Heiner Schaefer (16 May 2008)
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Performance of a minimally invasive cardiac output monitoring system (Flotrac/Vigileo)
- Thomas W.L. Scheeren, Christoph Wiesenack (4 May 2008)
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Friederike D Compton Department of Nephrology, Charité University Medicine Berlin, Campus Benjamin Franklin, Bianca Zukunft, Clemens Hoffmann, Walter Zidek, Juergen-Heiner Schaefer
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Dear Sir, We would like to thank Scheeren and Wiesenack for their interest in our work. It is correct that two versions of the FloTrac™/Vigileo™ software were used in the study. Despite our timely inquires, we were only informed after publication that six of our patients were not measured using the latest version (1.10). According to Edwards Lifesciences, the software was updated sometime in August 2006. Omitting those six patients (57 measurement pairs) and recalculating the data, however, yields comparable lack of success, as can be seen below. Our results and thus our conclusions remain unchanged. Agreement between arterial pressures: MAPfem/MAPrad bias 3 mmHg, limits of agreement (LOA) – 12 to 18 mmHg Comparison of radial and femoral artery pressures: systolic arterial pressures p = 0.2517, mean arterial pressures p < 0.001, diastolic arterial pressures p < 0.001, Agreement between cardiac indexes: Reference-CI/AP-CI bias 0.69 litre min-1 m-2, LOA -1.22 to 2.62 litre min- 1 m-2, TD-CI/AP-CI bias 0.77 litre min-1 m-2, LOA -1.11 to 2.65 litre min-1 m-2 As suggested by Scheeren and Wiesenack we also calculated agreement between PiCCO pulse contour values only (PC-CI) and the corresponding FloTrac/Vigileo measurements (AP-CI): PC-CI/AP-CI bias 0.72 litre min-1 m-2, LOA -1.23 to 2.66 litre min-1 m-2 Re-analysis of subgroups and ΔCI values did not yield significant changes either. We regret any confusion concerning the measurements in our study. Conflict of Interest:None declared |
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Thomas W.L. Scheeren Department of Anaesthesiology and Intensice Care Medicine, University Hospital Rostock, Germany, Christoph Wiesenack
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Dear Sir, we read with great interest the study by Compton and coworkers 1 comparing minimal invasive measurements of cardiac output obtained with two devices, the PiCCO™ and the FloTrac™/Vigileo™ system. The latter has been introduced into clinical practice in 2005, and early studies comparing this device with established methods to determine cardiac output have shown limited agreement only. As a consequence, the algorithm for calculating stroke volume, heart rate and hence cardiac output derived from the arterial pressure waveform (pulse contour analysis) has been modified and several software updates have been released. Compton and colleagues claim that in their study they used the new, improved software version named 1.10, which was released in November 2006, and not in spring 2006 as stated. On the other hand they describe that patients were included between July 2006 and May 2007. Thus the question arises which software version was really used or how many of their 25 patients were studied using the latest software update. This question is of importance since the manufacturer’s efforts to improve the software resulted in an improved percentage error of measurement values compared with standard techniques (for details compare table 1, which updates table 4 presented by the authors). Furthermore, one of the software improvements refers to the detection of arrhythmias, eliminating one of the study limitations raised by the authors. A second point refers to the data presentation. In the method section the authors claim that both the transpulmonary thermodilution derived cardiac output and the pulse contour derived continuous cardiac output values of the PiCCO™ system were used for comparison with the new device. However, in the results section, no comparison between both pulse contour derived methods is presented. Instead, PiCCO™ data obtained from transpulmonary thermodilution and pulse contour analysis were pooled. In addition, it would be interesting to see the agreement between data obtained from transpulmonary thermodilution and pulse contour analysis obtained with the PiCCO™. Finally, we wonder if transpulmonary thermodilution is a good choice for obtaining reference values for cardiac output particularly in patients with acute lung injury, as the femoral thermodilution curve is likely affected by pulmonary edema. In the Compton study, 19 of the 25 patients suffered from acute respiratory failure. Furthermore, the authors state that re-calibration of the PiCCO™ device was done at least every 24 hours. This interval seems inadequate, since a recent paper has shown that the accuracy of obtained values exceeds the accepted percentage error of 30%2 as early as 60 minutes after re-calibration 3. Hence, a frequent recalibration of the PiCCO™ device (every 20-30 min) is required to obtain reliable results, particularly in the presence of vasopressor therapy4 as used in the Compton patients. In their discussion the authors state that arrhythmia was a “limitation” but provide no information regarding its incidence. In this respect it is noteworthy that the key feature of the latest software version (v1.10) is the improved performance during arrhythmia 5, 6. Last but not least, the authors compared measurements obtained from different sites in the same patient (e.g. radial and femoral artery), so that two arterial lines must have been inserted. We wonder if this is in accordance with ‘routine patient care’ in the authors’ department. In conclusion, we challenge the conclusions presented by the authors concerning the (lack of) accuracy of the FloTrac™/Vigileo™ system since they obviously did not consistently use the improved new software version throughout their study as stated. Furthermore, the inappropriate choice and use of the reference method precludes expecting a close agreement between the two techniques. Sincerely T.W.L. Scheeren1 C. Wiesenack2 1University Hospital of Rostock, Department of Anaesthesiology and Intensive Care, Rostock, Germany 2University Hospital of Regensburg, Department of Anaesthesiology, Regensburg, Germany Table 1. Clinical evaluation studies on FloTrac™ accuracy of cardiac output measurement Author Year Patients Software 2SD/mean Reference deWaal EE 2007 CABG V 1.01 33 % 7 Mayer J 2007 Cardiac V 1.01 46 % 8 Opdam HI 2006 Cardiac V 1.03 ∼40 % 9 Sander M 2006 CABG V 1.03 54 % 10 Manecke GR 2007 Cardiac V 1.03 33 % 11 Prasser C 2007 Neuro-ICU V 1.03 49 % 12 McGee WT 2007 Mixed V 1.03 ∼50 % 13 Breukers RM 2007 Cardiac V 1.03 36 % 14 Sakka SG 2007 Septic V 1.07 35 % 15 Lorsomradee S 2007 Cardiac V 1.07 29%-56 % 16 Button D 2007 Cardiac V 1.07 ∼40 % 17 Canneson M 2007 CABG V 1.07 37 % 18 Prasser C 2007 CABG V 1.10 26,9 % 5 Mayer J 2008 CABG V 1.10 24,6 % 6 Compton FD 2008 Medical-ICU V 1.10 51,7 % 1 Abbreviations: CABG = coronary artery bypass grafting; ICU = intensive care unit; SD = standard deviation; 2SD/mean = percentage error according to Critchley&Critchley. References 1 Compton FD, Zukunft B, Hoffmann C, Zidek W, Schaefer JH. Performance of a minimally invasive uncalibrated cardiac output monitoring system (Flotrac/Vigileo) in haemodynamically unstable patients. Br J Anaesth 2008; 100: 451-6 2 Critchley LA, Critchley JA. A meta-analysis of studies using bias and precision statistics to compare cardiac output measurement techniques. J Clin Monit Comput 1999; 15: 85-91 3 Hamzaoui O, Monnet X, Richard C, Osman D, Chemla D, Teboul JL. 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 2008; 36: 434-40 4 Bein B, Meybohm P, Cavus E, et al. The reliability of pulse contour- derived cardiac output during hemorrhage and after vasopressor administration. Anesth Analg 2007; 105: 107-13 5 Prasser C, Trabold B, Schwab A, Keyl C, Ziegler S, Wiesenack C. Evaluation of an improved algorithm for arterial pressure-based cardiac output assessment without external calibration. Intensive Care Med 2007; 33: 2223-5 6 Mayer J, Boldt J, Wolf MW, Lang J, Suttner S. Cardiac output derived from arterial pressure waveform analysis in patients undergoing cardiac surgery: validity of a second generation device. Anesth Analg 2008; 106: 867-72 7 de Waal EE, Kalkman CJ, Rex S, Buhre WF. Validation of a new arterial pulse contour-based cardiac output device. Crit Care Med 2007; 35: 1904-9 8 Mayer J, Boldt J, Schollhorn T, Rohm KD, Mengistu AM, Suttner S. Semi- invasive monitoring of cardiac output by a new device using arterial pressure waveform analysis: a comparison with intermittent pulmonary artery thermodilution in patients undergoing cardiac surgery. Br J Anaesth 2007; 98: 176-82 9 Opdam HI, Wan L, Bellomo R. A pilot assessment of the FloTrac(TM) cardiac output monitoring system. Intensive Care Med 2007; 33: 344-9 10 Sander M, Spies CD, Grubitzsch H, Foer A, Muller M, von Heymann C. Comparison of uncalibrated arterial waveform analysis in cardiac surgery patients with thermodilution cardiac output measurements. Crit Care 2006; 10: R164 11 Manecke GR, Jr., Auger WR. Cardiac output determination from the arterial pressure wave: clinical testing of a novel algorithm that does not require calibration. J Cardiothorac Vasc Anesth 2007; 21: 3-7 12 Prasser C, Bele S, Keyl C, et al. Evaluation of a new arterial pressure - based cardiac output device requiring no external calibration. BMC Anesthesiol 2007; 7: 9 13 McGee WT, Horswell JL, Calderon J, et al. Validation of a continuous, arterial pressure-based cardiac output measurement: a multicenter, prospective clinical trial. Crit Care 2007; 11: R105 14 Breukers RM, Sepehrkhouy S, Spiegelenberg SR, Groeneveld AB. Cardiac output measured by a new arterial pressure waveform analysis method without calibration compared with thermodilution after cardiac surgery. J Cardiothorac Vasc Anesth 2007; 21: 632-5 15 Sakka SG, Kozieras J, Thuemer O, van Hout N. Measurement of cardiac output: a comparison between transpulmonary thermodilution and uncalibrated pulse contour analysis. Br J Anaesth 2007; 99: 337-42 16 Lorsomradee S, Lorsomradee S, Cromheecke S, De Hert SG. Uncalibrated arterial pulse contour analysis versus continuous thermodilution technique: effects of alterations in arterial waveform. J Cardiothorac Vasc Anesth 2007; 21: 636-43 17 Button D, Weibel L, Reuthebuch O, Genoni M, Zollinger A, Hofer CK. Clinical evaluation of the FloTrac/VigileoTM system and two established continuous cardiac output monitoring devices in patients undergoing cardiac surgery. Br J Anaesth 2007; 99: 329-36 18 Cannesson M, Attof Y, Rosamel P, Joseph P, Bastien O, Lehot JJ. Comparison of FloTracTM cardiac output monitoring system in patients undergoing coronary artery bypass grafting with pulmonary artery cardiac output measurements. Eur J Anaesthesiol 2007; 24: 832-9 Conflict of Interest:None declared |
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