Effectiveness evaluation of shielding material in reducing electromagnetic interference of cardiac pacemaker induced by portable information terminals.

In order to guard continuously patients with a cardiac pacemaker from radio waves emitted by the portable information terminal, an effective way is to shield the human body electromagnetically with a shielding material. There remain many unknown points regarding the effectiveness of wearing the shielding material. The authors have proposed a model for estimating the electromagnetic interference (EMI) with the pacemaker as a receiving antenna. This paper applies the model to the qualitative evaluation of the EMI reduction produced by wearing the shielding material. The result of the proposed evaluation method is compared to the result of the conventional evaluation method, which is based on the reduction of the electromagnetic field in the torso not containing a pacemaker. It is found that, although the conventional method does not reflect exactly the true EMI reduction for the pacemaker, it is useful as a preliminary evaluation of the EMI level for the pacemaker. The elliptic cylinder torso model, composed of three layers of skin, fat, and muscle, is considered, and the reductions of the EMI level by the conductive and the magnetic sheets for the pacemaker are evaluated by the proposed method. The following results are obtained. When the antenna is placed at a distance of 1 cm from the torso, the EMI reduction effect of the magnetic material is equivalent to placing the antenna at 7 cm, and that of the conductive sheet is equivalent to placing the antenna at more than 20 cm. The latter result indicates that, even if the antenna approaches within 1 cm of the torso, the equivalent distance satisfying essentially the guideline (22 cm) of the Japanese Pacemaker Association is realized, if the conductive sheet is worn on the torso. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(1): 48–53, 2003; Published online in Wiley InterScience (<URL>www.interscience.wiley.com</URL>). DOI 10.1002/ecja.10023 [ABSTRACT FROM AUTHOR]