Comparison of EEG Signal Characteristics Between Polysomnography and Self Applied Somnography Setup in a Pediatric Cohort

Abstract

We aimed to investigate differences in the electroencephalography (EEG) signal characteristics recorded with a type II polysomnography (PSG) setup including the American Academy of Sleep Medicine recommended EEG montage and Self Applied Somnography (SAS) setup. The PSG and SAS monitoring were simultaneously performed in a pediatric cohort ( $n=111$ ) with Nox A1 equipment (Nox Medical, Reykjavik, Iceland). The PSG channels F4-M1 and F3-M2 were compared to the SAS channels AF4-E3E4 and AF3-E3E4. The analyses were conducted separately in each sleep stage. The amplitude levels were compared by investigating envelope curves of each epoch and the frequency content by investigating the power spectrums obtained with Welch’s method. The EEG spectral morphology was similar between SAS and PSG. However, the SAS had consistently lower median amplitudes in all sleep stages compared to the PSG. In Stage N3 (slow-wave sleep), the lower and upper envelope curves had 42.4–47.4% lower median absolute amplitudes. Similarly, the SAS channels had consistently less power in the whole analysed frequency range of 0.3–35 Hz. In conclusion, the results illustrate that the SAS signals have similar EEG spectral morphology but consistently lower amplitudes and less power across the whole EEG frequency range compared to PSG signals. To achieve scoring corresponding to PSG, either the raw SAS signals should be digitally preprocessed or the amplitude threshold for identifying N3 should be lowered from $75~\mu \text{V}$ to e.g. $45~\mu \text{V}$ when using SAS instead of PSG. Further clinical validation studies are required to demonstrate scoring reliability using modified scoring rules.

Keywords

• Electroencephalography
• pediatric sleep disorders
• polysomnography
• self-applied somnography
• sleep staging
• spectral analysis