Spot-electrode Array for Impedance Cardiography Determined from the Measurement of Current Distribution on the Thorax

• Published in: Japanese journal of medical electronics and biological engineering Vol. 38; no. 3; pp. 238 - 245
• Main Authors: YAMAKOSHI, Ken-ichi, NAKAGAWARA, Minoru
• Format: Journal Article
• Language: Japanese
• Published: Japanese Society for Medical and Biological Engineering 2000; 一般社団法人 日本生体医工学会
• ISSN: 0021-3292; 2185-5498
• DOI: 10.11239/jsmbe1963.38.238

Transthoracic impedance or admittance cardiography has been one of the simple and useful methods for noninvasive monitoring of cardiovascular function. Generally, a tetra-polar band-electrode system proposed by Kubicek et al. has been used in this method. However, the band-electrode attachment is troublesome, makes the subject uncomfortable during long-term monitoring and is often inconvenient for clinical practice. We designed a new spot-electrode array in place of the band-electrode array. Its location was determined by measuring current distribution on the thorax using a 64-ch impedance mapping system. A uniform distribution of current density suitable for an electrical cylinder model of the thorax was evaluated using this mapping. The new spot-electrode array was developed and investigated for suitability in a cylindrical model using 11 normal male subjects in supine position. The current distribution made by the new spot-electrode array was similar to the uniform current distribution (γ=0.920-0.962, p<0.001) and capable of emulating the band-electrode array (γ=0.969-0.975, p<0.001). In a comparison between the new spot-electrode array and band-electrode array for impedance cardiography, the stroke volume values obtained by the spot electrode were 5-19% larger than those by the band electrode. The loss of uniform current distribution on the thorax under the impedance change related to cardiac ejection, which was observed in this study, may cause an over-estimation of the stroke volume measured by the new spot-electrode array.