Cardiac Monitoring with Textile Capacitive Electrodes in Driving Applications: Characterization of Signal Quality and RR Duration Accuracy

Figure 7. Driving simulator.

Figure 13. FFT-based method to measure cECG RR duration. (a) Raw cECG signal. To improve visualization, baseline wander has been removed by subtracting a moving average with a window of 125 samples and a step of 31 samples. (b) Processed cECG inspired by the Pan–Tompkins algorithm. (c) FFT of processed cECG, with the frequency range for RR duration and the frequency corresponding to RR duration.

Figure A1. Detection of R peaks on 35-s strips of reference ECG and textile cECG. (a) Raw reference ECG. (b) Textile cECG filtered with high-pass (5th order Butterworth, 5Hz cutoff frequency) and low-pass (15th order FIR, 50Hz cutoff frequency) filters. Signals were taken from subject #5 in session #3. Amplitudes are in normalized units (between zero and one).

Figure A2. Close-up of Figure A1 over 5 s. (a) Raw reference ECG. (b) Textile cECG filtered with high-pass (5th order Butterworth, 5Hz cutoff frequency) and low-pass (15th order FIR, 50Hz cutoff frequency) filters. Signals were taken from subject #5 in session #3. Amplitudes are in normalized units (between zero and one).

Figure A3. Scatter plot of delays between R peaks timing on reference ECG and R peaks timing on textile cECG.

Figure A4. Distribution of delays between R peaks timing on reference ECG and R peaks timing on textile cECG.

Figure 1. Tajima TMLX-1201 embroidery machine.

Figure 2. Prototyping process of the electrodes. (A) Embroidered electrode. (B) Woven electrode.

Figure 3. Textile capacitive electrode samples. (a) Electrode A.73.50: embroidered, square, 25.81 cm2. (b) Electrode A.73.46: woven, square, 58.06 cm2. (c) Electrode A.73.42: embroidered, rectangle, 58.06 cm2. (d) Electrode A.73.41: embroidered, square, 58.06 cm2. The gray metal ring seen in the center of each electrode is the socket side of a snap-in connector that allows the cECG active circuit board to be attached directly to the back of the electrode.

Figure 4. ECG acquisition pipeline.

Figure 5. Active circuit for capacitive ECG.

Figure 6. Software architecture.