A Protocol for Comparing Dry and Wet EEG Electrodes During Sleep

Sven Leach; Ku-Young Chung; Laura Tüshaus; Reto Huber; Walter Karlen

doi:10.3389/fnins.2020.00586

A Protocol for Comparing Dry and Wet EEG Electrodes During Sleep

Front Neurosci. 2020 Jun 17:14:586. doi: 10.3389/fnins.2020.00586. eCollection 2020.

Authors

Sven Leach¹, Ku-Young Chung², Laura Tüshaus², Reto Huber^{1

3}, Walter Karlen²

Affiliations

¹ Child Development Center and Pediatric Sleep Disorders Center, University Children's Hospital Zurich, University of Zurich, Zurich, Switzerland.
² Mobile Health Systems Lab, Department of Health Sciences and Technology, Institute of Robotics and Intelligent Systems, ETH Zürich, Zurich, Switzerland.
³ Department of Child and Adolescent Psychiatry and Psychotherapy, Psychiatric Hospital, University of Zurich, Zurich, Switzerland.

Abstract

Background: Sleep is commonly assessed by recording the electroencephalogram (EEG) of the sleeping brain. As sleep assessments in a lab environment are cumbersome for both the participant and researcher, it would be highly desirable to record sleep EEG with a user-friendly and mobile device. Dry electrodes that are reusable, low-cost, and easy to apply would be an essential component of such a device. In this study, we developed a testing protocol to investigate the performance of novel flat-type dry electrodes for sleep EEG recordings in free-living conditions.

Methods: Overnight sleep EEG, electrooculogram and electromyogram of four young and healthy participants were recorded at home. Two identical ambulatory recording devices, one using novel flat-type dry electrodes, the other using self-adhesive pre-gelled electrodes, simultaneously recorded sleep EEG. Between both electrode types, we then compared the signal quality, the incidence of artifacts, the sensitivity, specificity and inter-scoring reliability (Cohen's kappa) of sleep staging, as well as the agreement of important characteristics of sleep-specific EEG microstructure features, such as slow waves (0.5-4 Hz) and sleep spindles (10-16 Hz).

Results: Our testing protocol comprehensively compared the two electrode types on a macro- and microstructure level of sleep. The dry and pre-gelled electrodes both had comparable signal quality and sleep staging was feasible with both electrodes. Also, slow-wave and spindle characteristics were similar. However, sweat artifacts were more prevalent in the flat-type dry electrodes.

Conclusion: With a reliable testing protocol, the performance of dry electrodes can be compared to reference technologies and objectively assessed also in free-living conditions.

Keywords: dry electrodes; mobile EEG; natural settings; signal quality; sleep slow waves; sleep spindles; sleep staging; testing protocol.