Tohoku J. Exp. Med., 2004, 202(3)

Validity of the Adaptive Filter for Accurate Measurement of Cardiac Output in Impedance Cardiography

TAKASHI ONO, YOSHIFUMI YASUDA,¹ TOMONORI ITO,¹ ALLAN K. BARROS,² KOJI ISHIDA, MIHARU MIYAMURA, MAKOTO YOSHIZAWA³ and TOMOYUKI YAMBE⁴

Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya 464-8601,
¹Health Science Center, Toyohashi University of Technology, Toyohashi 441-8122,
²Universidade Federal do Maranho, Maranho, Brazil, and
³Information Synergy Center, and ⁴Institute of Development, Aging and Cancer, Tohoku University, Sendai 980-8575

The purpose of this study was to assess the validity of an adaptive filter, the scaled Fourier linear combiner (SFLC), in the impedance cardiography (ICG). Eight healthy males underwent constant-load bicycle exercise at different intensities from unloaded to near maximal intensity. The stroke volume (SV) and cardiac output (Q) measured by ICG at each condition were compared with those by the CO₂ rebreathing method. We found that the noises were greatly reduced in the impedance waveform and that the inflection points, so-called the B- and X-points, were clearly detected even during strenuous exercise using the SFLC. Although a high correlation was observed between Qs measured by the two methods, the mean values of Qs in each method differed significantly and the regression line also differ�ed significantly from the identity line. Likewise, a significant correlation was observed between SVs obtained by the two methods, but a significant difference in the group mean values and a trend of the regression line were observed. These findings suggest that the use of SFLC in ICG improves the performance in eliminating the noises and in detecting the inflection points in the waveform, thereby contributing to the accurate and beat-to-beat measurements of SV and Q especially during exercise.

keywords —— impedance cardiography; adaptive filter; cardiac output; stroke volume; CO₂ rebreathing

© 2004 Tohoku University Medical Press

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Present address for Takashi Ono, Department of Health and Sports Science, Health and Welfare Technical College, Edogawa University, 474 Komaki, Nagareyama, Chiba 270-0198, Japan.

e-mail: tono@edogawa-u.ac.jp

For reprints request, contact T. Ono at the address above.