Dynamic changes in EEG spectra during obstructive apnea in children

Children are less likely to demonstrate EEG arousal during obstructive sleep apnea (OSA) than adults. We hypothesized that changes in spectral EEG characteristics occur during REM-associated OSA in the absence of arousal. Eight snoring children underwent overnight polysomnography. OSA events during REM periods not associated with EEG or behavioral arousal were identified. EEG signals from C3A2 and C4A1 leads corresponding to 1) < or =10-sec epochs preceding OSA (PRE), 2) the obstructed period (OSA), and 3) < or =10-sec epochs following airflow resumption (POST) were subjected to fast Fourier transform (FFT) routines. Seventy-two isolated OSA, and 14 clusters of > 4 OSA events were analyzed. In single OSA, delta OSA amplitude was lower than in PRE (P < 0.01) and in POST (P < 0.001). Furthermore, POST delta amplitude was higher than PRE (P < 0.01). In contrast, in OSA clusters, the dynamic differences in delta amplitude disappeared after the second OSA. Reciprocal increases and decreases occurred for the theta frequency domain during OSA and post-OSA, while sigma and beta frequency power did not change. We conclude that during isolated OSA episodes without arousal, significant decreases in power selectively occur for delta frequency, and are followed by a rebound increase upon termination of apnea. The delta changes are progressively attenuated during repeated OSA. We postulate that delta changes may reflect ongoing adaptations in sleep pressure which are necessary to relieve the respiratory compromise, and may represent subtle evidence for arousal and consequent sleep fragmentation in children with OSAS.