April 22, 2020SensorsOpen Access

Two-Electrode ECG for Ambulatory Monitoring with Minimal Hardware Complexity

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Why the study?

Two-electrode ground-free ECG systems offer minimal hardware complexity for wearable battery-powered devices, but noise remains the main issue.

Structured PICO

Population

A living subject and a patient simulator

Intervention

Three proposed noise suppression methods for a two-electrode ground-free ECG acquisition system utilizing the ADS1191 analogue front-end

Comparator

Three-electrode sensing

Outcome

Noise suppression performance (Power Spectral Density at 50 Hz), current consumption, and hardware complexitysurrogate

A novel two-electrode ground-free ECG system with specific noise suppression methods can achieve high-quality signals comparable to three-electrode systems while maintaining low current consumption suitable for wearable devices.

Implication

Two-electrode ground-free ECG may simplify wearable devices; leaves open clinical validation and noise performance in diverse populations.

Abstract

This article introduces a two-electrode ground-free electrocardiogram (ECG) with minimal hardware complexity, which is ideal for wearable battery-powered devices. The main issue of ground-free measurements is the presence of noise. Therefore, noise suppression methods that can be employed for a two-electrode ECG acquisition system are discussed in detail. Experimental measurements of a living subject and patient simulator are used to investigate and compare the performance of the three proposed methods utilizing the ADS1191 analogue front-end for biopotential measurements. The resulting signals recorded for the simulator indicate that all three methods should be suitable for suppressing power-line noise. The Power Spectral Density (PSD) of the signals measured for a subject exhibits differences across methods; the signal power at 50 Hz is -28, -24.8, and -26 dB for the first, second, and third method, respectively. The digital postprocessing of measured signals acquired a high-quality ECG signal comparable to that of three-electrode sensing. The current consumption measurements demonstrate that all proposed two-electrode ECG solutions are appropriate as a battery-powered device (current consumption < 1.5 mA; sampling rate of 500 SPS). The first method, according to the results, is considered the most effective method in the suppression of power-line noise, current consumption, and hardware complexity.