Validation
Accuracy, Precision, Directional Changes & Time Responsiveness
NICOM has been validated extensively against the Swan-Ganz PAC-CCO Vigilance® Continuous Cardiac Output system by Edwards Life Sciences. Like NICOM the Vigilance CCO system is also a continuous monitoring device, but is based on the gold standard Pulmonary Artery Catheter (PAC). The FDA regulatory process involved comparing simultaneous measurements of both devices in critical care patients which were analyzed for inter-device agreement.
NICOM has also been validated against Bolus Thermodilution and arterial pulse contour devices.
Rigorous research in the last years yields many validation trials demonstrating the accuracy of the NICOM in real life settings, and in a variety of patients’ populations.
Both of the PAC-based systems - continuous cardiac output and Bolus thermodilution methods were employed as reference (1-2). Further studies involved simultaneous comparisons of the NICOM system to Swan Ganz and other devices based on pulse contour analysis (3-4).
The main endpoints evaluated for accuracy were:
- Accuracy-absolute bias compared to the reference method
- Precision
- Sensitivity and specificity to detect directional changes in CO
- Time Responsiveness
A recent landmark paper published in Intensive Care Medicine by several European leaders of the critical care specialty outlines the state of the art method to validate a continuous CO monitor(5). Of note, the aforementioned NICOM studies uniquely adhered to this protocol as was highlighted in the article.
The main parameters that were observed were:
- Absolute bias vs. the reference method. Care should be taken to ensure that both devices are on similar time averaging modes and that the reference device’s precision and time responsiveness are taken into account because different technologies have different precision, averaging and responsiveness attributes which need to be taken under consideration when comparing numbers on the screen.
- Precision. The variability of values due to random errors of measurement.
- Time responsiveness: How quickly does a hemodynamic change such as increase in stroke volume or CO manifest when measured with the tested technology vs. the reference. Fast responsiveness is a key enabler for optimal hemodynamic differential diagnosis, early warning signal and determination of fluid responsiveness, drug titration and the like. For example, thermodilution which is considered by many to be a reference device may not be an ideal reference for continuous devices due to inability to quickly determine responses and given the underlying technology’s precision and responsiveness profiles (figure 1).
- Sensitivity and specify for directional changes. The value of CO Monitoring is most profound and helpful during times of hemodynamic changes, as an excellent tool for quick differential diagnosis, guided resuscitation and monitoring. It is therefore imperative to evaluate the device accuracy during periods of increasing and decreasing CO vs. simply comparing static CO values during stable periods. When looking at directional changes however, it is even more important to consider the underlying differences in time responsiveness.
References:
<ol>
<li><span><span>Squara P, Denjean D, Estagnasie P, et al. </span><span>Noninvasive Cardiac Output Monitoring (NICOM): a Clinical Validation. Intensive Care Med. 2007 Jul;33(7):1191-4 </span></span></li>
<li><span>Raval NY, Squara P, Cleman M, et al. Multicenter Evaluation of Noninvasive Cardiac Output Measurement by Bioreactance Technique. </span><span>J Clin Monit Comput. 2008 Mar 14 </span></li>
<li><span>Marque S, Cariou A, Chiche JD, et al. </span><span>Comparison between Flotrac-Vigileo, and Bioreactance, a totally noninvasive method for cardiac output monitoring. Crit Care. 2009 May 19;13(3):R73 </span></li>
<li><span>Squara P, Rotcajg D, Denjean D, et al. Comparison of monitoring performance of Bioreactance vs. pulse contour during recruitment </span><span>Maneuvers. Crit Care. 2009;13(4):R125 </span></li>
<li><span>Squara P, Cecconi M, Rhodes A, et al. </span><span>Tracking changes in cardiac output: methodological considerations for the validation of monitoring devices.Intensive Care Med. 2009 ;35(10):1801-8<span id="1277385628838E"> </span></span></li>
</ol>
Fig 1. Adapted from Marque S et al. Comparison between Flotrac-Vigileo, and Bioreactance, a totally noninvasive method for cardiac output monitoring. Crit Care. 2009 May 19;13(3):R73 click to enlarge
References
- Squara P, Denjean D, Estagnasie P, et al. Noninvasive Cardiac Output Monitoring (NICOM): a Clinical Validation. Intensive Care Med. 2007 Jul;33(7):1191-4
- Raval NY, Squara P, Cleman M, et al. Multicenter Evaluation of Noninvasive Cardiac Output Measurement by Bioreactance Technique. J Clin Monit Comput. 2008 Mar 14
- Marque S, Cariou A, Chiche JD, et al. Comparison between Flotrac-Vigileo, and Bioreactance, a totally noninvasive method for cardiac output monitoring. Crit Care. 2009 May 19;13(3):R73
- Squara P, Rotcajg D, Denjean D, et al. Comparison of monitoring performance of Bioreactance vs. pulse contour during recruitment Maneuvers. Crit Care. 2009;13(4):R125
- Squara P, Cecconi M, Rhodes A, et al. Tracking changes in cardiac output: methodological considerations for the validation of monitoring devices.Intensive Care Med. 2009 ;35(10):1801-8