ABC | Volume 113, Nº2, August 2019

Original Article Coll et al Non-invasive cardiac output measurement Arq Bras Cardiol. 2019; 113(2):231-239 1. Jhanji S, Dawson J, Pearse RM. Cardiac output monitoring: basic science and clinical application. Anaesthesia. 2008;63(2):172-81. 2. Myers J, Gujja P, Neelagaru S, Burkhoff D. Cardiac output and cardiopulmonary responses to exercise in heart failure: application of a new bio-reactance device. J Card Fail. 2007;13(8):629-36. 3. Klasnja AV, Jakovljevic DG, Barak OF, Popadic Gacesa JZ, Lukac DD, Grujic NG. Cardiac power output and its response to exercise in athletes and non- athletes. Clin Physiol Funct Imaging. 2013;33(3):201-5. 4. Myers J, Froelicher VF. Hemodynamic determinants of exercise capacity in chronic heart failure. Ann Intern Med. 1991;115(5):377-86. 5. Sullivan MJ, Knight JD, Higginbotham MB, Cobb FR. Relation between central and peripheral hemodynamics during exercise in patients with chronic heart failure. Muscle blood flow is reduced with maintenance of arterial perfusion pressure. Circulation. 1989;80(4):769-81. 6. Kovacs R, Baggish AL. Cardiovascular adaptation in athletes. Trends Cardiovasc Med. 2016;26(1):46-52. References the global cardiac performance. Such a data processing proceed is of course inadequately, when aiming to assess transient cardiac abnormalities during exercise like ischemia. Since the beat-by-beat reliability of our TB based measures remains unknown, we recommend other impedance-based technologies, which offer a reliable beat-by-beat analysis of hemodynamic parameters during exercise. 20 The third major finding was that CPO was found to be independent of cardiac structure and function at rest as well as to traditional cardiopulmonary exercise parameters. Klasnja et al. 3 previously demonstrated a weak correlation between CPO peak and resting parameters of left ventricular morphology and function. 3 We also did not find a strong relation between CPO peak and echocardiographic findings at rest. Our findings show once again that resting parameters cannot be used to estimate maximal cardiovascular performance. For the first time driven by our progressive statistics, 47 we report the SWDs for all investigated TB parameters. From a practical point of view, the provided thresholds can be used as a framework to judge in healthy adults, whether observed differences in the analyzed parameters should be interpreted or not in a daily medical routine. Further, it is promising to use these thresholds as cutting-off values for minimal required effects detected by longitudinal or cross-sectional studies using the here investigated TB measures in the future. For example, in healthy adults, the calculated SWD of the CPO was 0.7 W, meaning that longitudinal or cross-sectional differences should only be interpreted, when this cut-off value is exceeded. The major limitation of our study is the high dropout rate (n=8). However, to detect outliers, we objectively defined them as those values, which were greater than the pooled standard deviation. Based on this approach and our recruited healthy adults, it can be assumed that the detected outliers had not a physiological cause. Contrary, it is more likely that the identified outliers had rather an underlying technical reason. Therefore, further improvements in TB, for example, regarding the application and quality of electrodes are required. Consequently, technical errors must be executed by proprietary algorithms, before valid decisions are possible. When taken these aspects together, our findings indicate that TB can only be considered as a reliable technology for measuring hemodynamic parameters after outliers have been excluded. Conclusion In conclusion, at this stage, our results preclude the clinical use of TB in healthy subject population when outliers are not identified even if a previous study seem to show its possible application in a strictly controlled research setting. Author contributions Conception and design of the research: Coll MT, Dinh W; Acquisition of data: Coll MT, Kiefer C, Dinh W; Analysis and interpretation of the data: Hoppe MW, Dinh W; Statistical analysis: Hoppe MW; Obtaining financing: Krahn T, Mondritzki T, Dinh W; Writing of the manuscript: Coll MT, Hoppe MW, Boehme P, Dinh W; Critical revision of the manuscript for intellectual content: Coll MT, Boehme P, Krahn T, Kiefer C, Kramer F, Mondritzki T, Pirez P. Potential Conflict of Interest No potential conflict of interest relevant to this article was reported. Sources of Funding This study was funded by Bayer Pharma. Study Association This article is part of the thesis of Doctoral submitted by Christian Kiefer, from University Hospital Witten/Herdecke. Ethics approval and consent to participate This study was approved by the Ethics Committee of the University of Witten/Herdecke under the protocol number 131/2914. All the procedures in this study were in accordance with the 1975 Helsinki Declaration, updated in 2013. Informed consent was obtained from all participants included in the study. 237