Abstract
In response to the growing clinico-economic need for comprehensive home-based sleep testing, we recently developed a self-applicable facial electrode set with screen-printed Ag/AgCl electrodes. Our previous studies revealed that nocturnal sweating is a common problem, causing low-frequency artifacts in the measured electroencephalography (EEG) signals. As the electrode set is designed to be used without skin abrasion, not surprisingly this leads to relatively high electrode-skin impedances, significant impedance changes due to sweating and an increased risk of sweat artifacts. However, our recent electrochemical in vitro investigations revealed that the sweat artifact tolerance of an EEG electrode can be improved by utilizing an appropriate Ag/AgCl ink. Here we have investigated in vivo electrode-skin impedances and the quality of EEG signals and interference due to sweating in the population of 11 healthy volunteers. Commercial Ag and Ag/AgCl inks (Engineered Conductive Materials ECM LLC and PPG Industries Inc.) were used to test electrode sets with differently constructed ink layers. Electrode-skin impedances and EEG signals were recorded before and after exercise-induced sweating. There was extensive variation in the electrode-skin impedances between the volunteers and the electrode positions: 14.6–200 $\text{k}\Omega $ (PPG electrodes) and 7.7–200 $\text{k}\Omega $ (ECM electrodes). Sweating significantly decreased ( $p ) the impedances in most cases. The EEG signal quality was assessed by comparing average band powers from 0.5 to 2 Hz before and after sweating. Only slight differences existed between the ECM and PPG electrodes; however, the lowest band power ratio ( i.e . the smallest increase in the band power due to sweating) was achieved with ECM electrodes.
Highlights
The standard medical test for diagnosing sleep disorders such as obstructive sleep apnea (OSA) is in-lab polysomnography (PSG) [1]
There were no systematic differences in the impedance values between the ECM and PPG electrodes (p = 0.15 − 0.95) or between the A and B electrodes (p = 0.28 − 0.9), but the impedance values with ECM A and ECM C mastoid electrodes were different (p = 0.028)
Our results demonstrate that sweating reduced the absolute skin-electrode impedance values in almost all electrodes
Summary
The standard medical test for diagnosing sleep disorders such as obstructive sleep apnea (OSA) is in-lab polysomnography (PSG) [1]. PSG is an overnight measurement and provides detailed physiological data including. The associate editor coordinating the review of this manuscript and approving it for publication was Norbert Herencsar. Electroencephalogram (EEG), electrooculogram (EOG), electromyogram (EMG), and cardiorespiratory signals. Though PSG has many advantages, it is considered too expensive and time-consuming for routine OSA diagnostics [2]. As OSA is a global public health burden affecting nearly 1 billion adults [3] being associated with severe health consequences, new cost-efficient alternatives to the standard PSG are urgently needed.
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