A Novel CB/PDMS Electrode For ECG Monitoring During Swimming

Abstract

To collect reliable electrocardiogram (ECG) signals during swimming, waterproof tape must be generously applied to commercial Ag/AgCl electrodes to seal off water penetration. Prolonged use of waterproof tape can lead to skin irritations and when the tape is removed it can tear the skin. PURPOSE: The purpose of the study was to examine if our reusable hydrophobic ECG electrodes, which are composed of carbon black powder/Polydimethylsiloxane (CB/PDMS), can be effectively used to collect reliable ECG signals underwater. METHODS: An ECG signal (Lead I configuration) was collected using a custom-made chest strap which incorporated our hydrophobic electrodes. Two CB/PDMS electrodes were attached to the strap, which also had a miniaturized ECG data acquisition board. The ECG signal and tri-axis accelerometric data were saved directly into a micro-SD card in the ECG circuit board. Three participants were recruited to examine the electrodes’ performance during two types of swimming (freestyle and breaststroke). The experimental protocol included having the subjects stand while not immersed (dry condition, 1 min) and then swim each type of stroke (1 lap each (45 meter)). We examined the ECG signal quality by observing if there were reductions of QRS peak amplitudes during swimming when compared to the dry condition. Specifically, we calculated cross-correlation indices of ECG templates to quantitatively determine possible morphological changes in ECG waveforms when electrodes were exposed to water. Moreover, we computed the amount of signal dropout due to either motion artifacts or water penetration into our electrodes. RESULTS: No significant reduction of QRS peak amplitude was observed between dry and swimming conditions, for both freestyle and breaststroke. The cross correlation indices of ECG templates between dry and swimming conditions for freestyle and breaststroke were both 99.9%. Moreover, there was minimal ECG signal loss (less than 1%) due to either motion artifacts or water penetration. CONCLUSIONS: Our CB/PDMS electrodes can provide high-fidelity ECG signal morphologies without any amplitude degradation and minimal signal dropout during swimming. These electrodes have the potential to be applicable to better understanding underwater physiology, and as a performance-enhancement training aid.