For each device tested from Boston Scientific, Medtronic (Minneapolis, MN), and Abbott (Chicago, IL), we performed a frequency sweep, increasing the frequency from 1 Hz to 1000 kHz. Unlike smart scales or smart watch devices, this instrument gave us total control to change the frequency, the amplitude of the signal, as well as the signal measurement duration at each frequency. To evaluate a bioimpedance hardware system equivalent to our simulation study, we connected an impedance analyzer MFIA (Zurich Instruments, Zurich, Switzerland) to the input C terminal of the tissue-equivalent interface circuit defined by the ISO 14117 standard ( Figure 2). Simulated ICD, permanent cardiac pacemaker, and leads The smart ring inner current electrodes had dimensions of 7 × 7 mm with an edge-to-edge distance of 4 mm ( Figure 1C).
We simulated an EDA measurement placing a smart ring on the left fourth digit. The current source electrode (1.56 cm 2) was positioned in the caseback of the watch in contact with the dorsum of the wrist while the current sink electrode (1.69 cm 2) was positioned on the case to allow index-finger contact ( Figure 1B). For wrist-to-finger smart watch simulations, we posed the models wearing the B-Secur (Belfast, United Kingdom) HeartKey Test Watch below the left wrist bone, a watch developed to acquire simultaneous electrocardiographic and BIA measurements. Hand and foot current electrodes were modeled with surface areas of 31.9 and 106.7 cm 2, respectively.
For hand-to-foot smart scale simulations ( Figure 1A), we posed the models and aligned the heels in the feet electrodes with the center of the electrodes evenly distributed on the surface of the heels while the fingers were positioned flat on the hand electrodes.
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