The application of bioimpedance method for foot sole blood perfusion characterization

The bioimpedance technology may be applied to provide valuable information for clinical diagnosis in a costeffective way. In homecare for the diabetic foot, the monitoring of perfusion for foot sole becomes an important issue. In this paper, a bioimpedance based perfusion monitoring system for foot sole is developed. The temperature compensation is also taken into account for improving the bioimpedance measurement. The hardware design for the proposed system includes impedance measurement, temperature measurement, electrode design, and channel selection circuitry. The software design contains subject information setting, signal demodulation and measurement calibration, and data acquisition and analysis. From the performance testing, the total harmonic distortion of bioimpedance measurement for the proposed system is below 0.17% with the maximal error no greater than 0.2%. In the electrode design, the current paths for varied gaps between the electrodes are also simulated using finite element analysis so as to reveal the possible penetration depth of current for perfusion measurement. From the experimental results, the dynamic bioimpedance response shows in a good correlation with the measurements of laser Doppler flowmetry (r = 0.86).