Journal of Clinical Monitoring and Computing

, Volume 30, Issue 6, pp 753–755 | Cite as

Cardiac output monitoring: less invasiveness, less accuracy?

  • Bernd Saugel
  • Julia Y. Wagner
  • Thomas W. L. Scheeren

Measuring and optimizing cardiac output (CO) as one major determinant of oxygen delivery is a mainstay in the treatment of hemodynamically unstable patients in intensive care and perioperative medicine. Advanced hemodynamic monitoring using technologies allowing the assessment of stroke volume and thus CO is therefore highly recommended in these patients [1, 2, 3].

Although intermittent pulmonary artery thermodilution using a pulmonary artery catheter is still supposed to be the clinical gold standard for the assessment of CO [4], less-invasive and even non-invasive technologies have been developed in growing numbers in recent years and proposed for CO monitoring—including single-indicator transpulmonary thermodilution and calibrated or uncalibrated pulse contour analysis [3, 5].

While less- and non-invasive hemodynamic monitoring is certainly a striking concept in terms of patient safety and clinical applicability, the “measurement performance” of those monitoring technologies with regard to accuracy and precision of CO measurements in comparison with intermittent pulmonary artery thermodilution has repeatedly been questioned.

Therefore, the question arises whether “less invasiveness” necessarily means “less accuracy”. Cho et al. [6] need to be commended for aiming to answer this clinically relevant question by performing a very elegant study published in this issue of the journal. In their method comparison study, they compared agreement and trending ability between different methods for CO assessment with different degrees of invasiveness in patients undergoing off-pump coronary artery bypass surgery. As the reference method they used intermittent pulmonary artery thermodilution and evaluated the measurement performance of different test methods, namely continuous pulmonary artery thermodilution, transpulmonary thermodilution, pulse contour analysis calibrated to transpulmonary thermodilution, and uncalibrated pulse contour analysis.

Interestingly, the percentage error of CO measurements using continuous versus intermittent pulmonary artery thermodilution was 27 %. The percentage errors observed for transpulmonary thermodilution, pulse contour analysis calibrated to transpulmonary thermodilution, and uncalibrated pulse contour analysis were 13, 29, and 34 %, respectively. Only transpulmonary thermodilution showed a good ability to follow CO changes as determined by intermittent pulmonary artery thermodilution.

We don’t want to discuss statistical problems related to the percentage error [7, 8], the trending analysis [9, 10], and the definition of “acceptable agreement” in CO method comparison studies in this editorial.

Yet the findings of Cho and colleagues warrant some further discussion regarding the selection of monitoring technologies for our patients. Of note, the authors’ findings show better agreement between pulse contour analysis-derived CO and CO assessed with pulmonary artery thermodilution than most previous studies [11, 12, 13]. But yet, the study demonstrates that “invasive” transpulmonary thermodilution shows better agreement with pulmonary artery thermodilution compared with calibrated pulse contour analysis (that in turn showed better agreement than uncalibrated pulse contour analysis). As the study design allowed simultaneously comparing the various technologies for CO assessment (characterized by different degrees of invasiveness) it very elegantly shows that less invasiveness indeed seems to imply less accuracy.

This leads to the question how the clinician should choose the appropriate hemodynamic monitoring technology for the individual patient from the arsenal of the numerous commercially available systems.

We obviously need to be aware that every single hemodynamic monitoring technology has its own technical limitations. Knowledge of these specific limitations is a prerequisite for a wise use of these technologies. CO assessment with pulmonary artery thermodilution can only be accurate if there is no loss of thermal indicator between the injection site and the thermistor and no recirculation of the indicator [14, 15]. Therefore, pulmonary artery thermodilution measurements can be falsified by tricuspid or pulmonary valve insufficiency, intracardiac shunts, low CO states, or technical errors related to indicator injection (temperature, volume, timing, and duration of indicator injection) or catheter positioning [14, 15]. Transpulmonary thermodilution-derived CO measurements are basically affected by the same limiting factors related to the thermal indicator loss and recirculation, but compared with pulmonary artery thermodilution they are less influenced by CO variations over the respiratory cycle [15]. For both techniques, a close visual observation of the thermodilution curve is therefore key to verify correct CO measurements. For pulse contour analysis, several factors might influence the measurement performance. Self-evidently, pulse contour analysis depends on the signal quality of the arterial pressure waveform. Moreover, changes in vasomotor tone can impair the measurement performance of pulse contour analysis that might however be improved by frequent calibration to CO assessed with a more invasive technology (e.g. transpulmonary thermodilution) [16, 17, 18, 19]. In addition, the proprietary pulse contour analysis algorithms consider biometric patient data or properties of the arterial pressure waveform to derive CO; in certain patients or clinical situations these mathematical assumptions might not hold true [19]. Various limitations regarding technical problems and mathematical algorithms have also been described for all completely non-invasive technologies for CO assessment [5].

Besides potential limitations, we need to consider various other properties of different monitoring modalities when choosing the optimal tool for the individual patient; this includes accuracy, precision, and trending ability of the CO measurements, continuity of measurements (continuous, semi-continuous, or intermittent CO might be required in different clinical situations), and options to calibrate to reference CO values [2]. For instance, in many occasions it may not be essential to know if the actual CO is 3.9 or 4.2 L/min rather than to reliably track its changes after a certain intervention, e.g. volume expansion. In this context, we need to balance the risk of invasive hemodynamic monitoring tools against the limited accuracy of less-invasive technologies for the individual patient. We also need to consider which additional variables each monitoring technology is able to provide in addition to CO. Therefore, pulmonary artery catheterization might be indicated in a critically ill patient with circulatory shock and right ventricular failure or pulmonary artery hypertension [3] but not in a low or intermediate risk non-cardiac surgery patient. Transpulmonary thermodilution additionally allows the assessment of extravascular lung water and therefore might be a good way to monitor a patient with circulatory shock and acute respiratory failure [3]. During dynamic tests of fluid responsiveness (i.e. passive leg raising [20] or fluid challenge [21] tests) pulse contour analysis can be a monitoring option allowing the continuous real-time monitoring of changes in CO. In addition, in the perioperative setting, pulse contour analysis-based monitoring can be indicated to apply goal-directed hemodynamic therapy [2, 22].

Finally, institutional factors, costs, and personal experience with and confidence in different monitoring systems may play a role which technology we use for the individual patient.

To achieve our ultimate goal—improving the individual patient’s outcome by monitoring and optimizing cardiovascular dynamics—we need to understand and integrate all aspects related to invasiveness and measurement performance of the different monitoring technologies. This allows responsibly applying hemodynamic monitoring to the individual patient based on a differential indication.


Compliance with ethical standards

Conflict of interest

BS collaborates with Pulsion Medical Systems SE (Feldkirchen, Germany) as a member of the medical advisory board and received honoraria for giving lectures and refunds of travel expenses from Pulsion Medical Systems SE. BS received research support from Edwards Lifesciences (Irvince, CA, USA). BS and JYW received institutional research grants, unrestricted research grants, and refunds of travel expenses from Tensys Medical Inc. (San Diego, CA, USA). BS received honoraria for giving lectures from CNSystems Medizintechnik AG (Graz, Austria). BS and JYW received refunds of travel expenses from CNSystems Medizintechnik AG (Graz, Austria). TS received honoraria from Edwards Lifesciences and Masimo Inc. (Irvine, CA, USA) for consulting. TS received honoraria from Pulsion Medical Systems SE for lecturing.


  1. 1.
    Cecconi M, De Backer D, Antonelli M, Beale R, Bakker J, Hofer C, Jaeschke R, Mebazaa A, Pinsky MR, Teboul JL, Vincent JL, Rhodes A. Consensus on circulatory shock and hemodynamic monitoring. Task force of the European Society of Intensive Care Medicine. Intensive Care Med. 2014;40:1795–815. doi:10.1007/s00134-014-3525-z.CrossRefPubMedPubMedCentralGoogle Scholar
  2. 2.
    Vincent JL, Pelosi P, Pearse R, Payen D, Perel A, Hoeft A, Romagnoli S, Ranieri VM, Ichai C, Forget P, Della Rocca G, Rhodes A. Perioperative cardiovascular monitoring of high-risk patients: a consensus of 12. Crit Care. 2015;19:224. doi:10.1186/s13054-015-0932-7.CrossRefPubMedPubMedCentralGoogle Scholar
  3. 3.
    Teboul JL, Saugel B, Cecconi M, De Backer D, Hofer CK, Monnet X, Perel A, Pinsky MR, Reuter DA, Rhodes A, Squara P, Vincent JL, Scheeren TW. Less invasive hemodynamic monitoring in critically ill patients. Intensive Care Med. 2016. doi:10.1007/s00134-016-4375-7.Google Scholar
  4. 4.
    Rajaram SS, Desai NK, Kalra A, Gajera M, Cavanaugh SK, Brampton W, Young D, Harvey S, Rowan K. Pulmonary artery catheters for adult patients in intensive care. Cochrane Database Syst Rev. 2013;2:CD003408. doi:10.1002/14651858.CD003408.pub3.Google Scholar
  5. 5.
    Saugel B, Cecconi M, Wagner JY, Reuter DA. Noninvasive continuous cardiac output monitoring in perioperative and intensive care medicine. Br J Anaesth. 2015;114:562–75. doi:10.1093/bja/aeu447.CrossRefPubMedGoogle Scholar
  6. 6.
    Cho YJ, Koo CH, Kim TK, Hong DM, Jeon Y. Comparison of cardiac output measures by transpulmonary thermodilution, pulse contour analysis, and pulmonary artery thermodilution during off-pump coronary artery bypass surgery: a subgroup analysis of the cardiovascular anaesthesia registry at a single tertiary centre. J Clin Monit Comput. 2015. doi:10.1007/s10877-015-9784-6.Google Scholar
  7. 7.
    Hapfelmeier A, Cecconi M, Saugel B. Cardiac output method comparison studies: the relation of the precision of agreement and the precision of method. J Clin Monit Comput. 2016;30:149–55. doi:10.1007/s10877-015-9711-x.CrossRefPubMedGoogle Scholar
  8. 8.
    Saugel B, Reuter DA. Are we ready for the age of non-invasive haemodynamic monitoring? Br J Anaesth. 2014;113:340–3. doi:10.1093/bja/aeu145.CrossRefPubMedGoogle Scholar
  9. 9.
    Saugel B, Grothe O, Wagner JY. Tracking changes in cardiac output: statistical considerations on the 4-quadrant plot and the polar plot methodology. Anesth Analg. 2015;121:514–24. doi:10.1213/ane.0000000000000725.CrossRefPubMedGoogle Scholar
  10. 10.
    Saugel B, Wagner JY, Reuter DA. Haemodynamic monitoring: the inseparable relation of accuracy and trending. Br J Anaesth. 2015;115:943. doi:10.1093/bja/aev391.CrossRefPubMedGoogle Scholar
  11. 11.
    Peyton PJ, Chong SW. Minimally invasive measurement of cardiac output during surgery and critical care: a meta-analysis of accuracy and precision. Anesthesiology. 2010;113:1220–35. doi:10.1097/ALN.0b013e3181ee3130.CrossRefPubMedGoogle Scholar
  12. 12.
    Marik PE. Noninvasive cardiac output monitors: a state-of the-art review. J Cardiothor Vasc Anesth. 2013;27:121–34. doi:10.1053/j.jvca.2012.03.022.CrossRefGoogle Scholar
  13. 13.
    Slagt C, Malagon I, Groeneveld AB. Systematic review of uncalibrated arterial pressure waveform analysis to determine cardiac output and stroke volume variation. Br J Anaesth. 2014;112:626–37. doi:10.1093/bja/aet429.CrossRefPubMedGoogle Scholar
  14. 14.
    Nishikawa T, Dohi S. Errors in the measurement of cardiac output by thermodilution. Can J Anaesth. 1993;40:142–53. doi:10.1007/bf03011312.CrossRefPubMedGoogle Scholar
  15. 15.
    Reuter DA, Huang C, Edrich T, Shernan SK, Eltzschig HK. Cardiac output monitoring using indicator-dilution techniques: basics, limits, and perspectives. Anesth Analg. 2010;110:799–811. doi:10.1213/ANE.0b013e3181cc885a.CrossRefPubMedGoogle Scholar
  16. 16.
    Monnet X, Anguel N, Naudin B, Jabot J, Richard C, Teboul JL. Arterial pressure-based cardiac output in septic patients: different accuracy of pulse contour and uncalibrated pressure waveform devices. Crit Care. 2010;14:R109. doi:10.1186/cc9058.CrossRefPubMedPubMedCentralGoogle Scholar
  17. 17.
    Monnet X, Vaquer S, Anguel N, Jozwiak M, Cipriani F, Richard C, Teboul JL. Comparison of pulse contour analysis by Pulsioflex and Vigileo to measure and track changes of cardiac output in critically ill patients. Br J Anaesth. 2015;114:235–43. doi:10.1093/bja/aeu375.CrossRefPubMedGoogle Scholar
  18. 18.
    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. doi:10.1097/01.CCM.OB013E318161FEC4.CrossRefPubMedGoogle Scholar
  19. 19.
    Vincent JL, Rhodes A, Perel A, Martin GS, Della Rocca G, Vallet B, Pinsky MR, Hofer CK, Teboul JL, de Boode WP, Scolletta S, Vieillard-Baron A, De Backer D, Walley KR, Maggiorini M, Singer M. Clinical review: update on hemodynamic monitoring—a consensus of 16. Crit Care. 2011;15:229. doi:10.1186/cc10291.CrossRefPubMedPubMedCentralGoogle Scholar
  20. 20.
    Monnet X, Teboul JL. Passive leg raising: five rules, not a drop of fluid! Crit Care. 2015;19:18. doi:10.1186/s13054-014-0708-5.CrossRefPubMedPubMedCentralGoogle Scholar
  21. 21.
    Cecconi M, Parsons AK, Rhodes A. What is a fluid challenge? Curr Opin Crit Care. 2011;17:290–5. doi:10.1097/MCC.0b013e32834699cd.CrossRefPubMedGoogle Scholar
  22. 22.
    Salzwedel C, Puig J, Carstens A, Bein B, Molnar Z, Kiss K, Hussain A, Belda J, Kirov MY, Sakka SG, Reuter DA. Perioperative goal-directed hemodynamic therapy based on radial arterial pulse pressure variation and continuous cardiac index trending reduces postoperative complications after major abdominal surgery: a multi-center, prospective, randomized study. Crit Care. 2013;17:R191. doi:10.1186/cc12885.CrossRefPubMedPubMedCentralGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  • Bernd Saugel
    • 1
  • Julia Y. Wagner
    • 1
  • Thomas W. L. Scheeren
    • 2
  1. 1.Department of Anesthesiology, Center of Anesthesiology and Intensive Care MedicineUniversity Medical Center Hamburg-EppendorfHamburgGermany
  2. 2.Department of AnesthesiologyUniversity of Groningen, University Medical Centre GroningenGroningenThe Netherlands

Personalised recommendations