Signal processing technique for non-invasive real-time estimation of cardiac output by inductance cardiography (thoracocardiography)
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Inductance cardiography (thoracocardiography) non-invasively monitors changes in stroke volume by recording ventricular volume curves with an inductive plethysmographic transducer encircling the chest at the level of the heart. Clinical application of this method has been hampered, as data analysis has not been feasible in real time. Therefore a novel, real-time signal processing technique for inductance cardiography has been developed. Its essential concept consists in performance of multiple tasks by several, logically linked signal processing modules that have access to common databases. Based on these principles, a software application was designed that performs acquisition, display, filtering and ECG-triggered ensemble averaging of inductance signals and separates cardiogenic waveforms from noise related to respiration and other sources. The resulting ventricular volume curves are automatically analysed. Performance of the technique for monitoring cardiac output in real time was compared with thermodilution in four patients in an intensive care unit. The bias (mean difference) among 76 paired thoracocardiographic and thermodilution derived changes in cardiac output was 0%; limits of agreement (±2 SD of the bias) were ±25%. It is concluded that the proposed signal processing technique for inductance cardiography holds promise for non-invasive, real-time estimation of changes in cardiac output.
KeywordsInductance cardiography Thoracocardiography Non-invasive cardiac monitoring Stroke volume Cardiac output Real-time data analysis
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- Bland, M. J., andAltman, D. G. (1986): ‘Statistical methods for assessing agreement between two methods of clinical measurement’,Lancet,1, pp. 307–310Google Scholar
- Bloch, K. E., Jugoon, S., andSackner, M. A. (1994): ‘Thoracocardiographic derived left ventricular systolic time intervals’,Chest,106, pp. 1668–1674Google Scholar
- Bloch, K. E., Baumann, P. C., Stocker, R., andRussi, E. W. (1997): ‘Noninvasive monitoring of cardiac output in critically ill patients with thoracocardiography’,Am. J. Respir. Crit. Care. Med.,155, pp. 26–31Google Scholar
- Bloch, K. E. (1998): ‘Impedance and inductance monitoring of cardiac output’, inTobin, M. J. (Ed.): ‘Principles and practice of intensive care monitoring’ (McGraw-Hill, Inc., New York, 1998), pp. 915–930Google Scholar
- Kaplan, V., Bucklar, G., andBloch, K. E., ‘Noninvasive monitoring of cardic output during exercise by inductance cardiography’,Med. Sci. Sports Exerc. 2003 (in press)Google Scholar
- Konno, K., andMead, J. (1966): ‘Measurement of separate volume changes of ribcage and abdomen during breathing’,J. Appl. Physiol.,22, pp. 407–422Google Scholar
- Sackner, M. A., andKrieger, B.P. (1989): ‘Noninvasive respiratory monitoring’ inScharf, S. M., andCassidy, S. S. (Eds) ‘Heartlung interactions in health and disease’ (Marcel Dekker Inc., Basel, New York, 1989), pp. 663–805Google Scholar
- Sackner, M. A., Watson, H., Belsito, A. S., Feinerman, D., Suarez, M., Gonzalez, G., Bizousky, F., andKrieger, B. (1989): ‘Calibration of respiratory inductive plethysmograph during natural breathing’,J. Appl. Physiol.,66, pp. 410–420Google Scholar
- Sackner, M. A., Hoffman, R. A., Stroh, D., andKrieger, B. P. (1991): ‘Thoracocardiography Part 1: noninvasive measurement of changes in stroke volume; comparisons to thermodilution’,Chest,99, pp. 613–622Google Scholar
- Watson, H. L., Poole, D. A., andSackner, M. A. (1988): ‘Accuracy of respiratory inductive plethysmographic measurement of cross-sectional area of models’,J. Appl. Physiol.,65, pp. 306–308Google Scholar
- Yelderman, M. (1990): ‘Continuous measurement of cardiac output with the use of stochastic system identification techniques’,J. Clin. Monit.,6, pp. 322–332Google Scholar