T-I-066 RELATIONSHIP BETWEEN SYMPATHETIC AND CORTICAL REACTIVITY IN RESPONSE TO RESPIRATORY EVENTS DURING SLEEP

Abstract

Introduction and Objectives: Several studies have suggested a tight and reciprocal relationship between autonomic and cortical reactivity to different types of stimuli during sleep, with concomitant cortical arousal and sympathetic activation after the stimulus and an increase in sympathetic basal activity when the stimulus gives rise to an arousal. However, this relationship remains unclear in case of respiratory events. Thus, we studied autonomic reactivity after respiratory events according to sleep stages, type of respiratory events, presence of cortical arousal (CA) and autonomic activity during respiratory events. Materials and Methods: Fourteen untreated patients with obstructive sleep apneas/hypopneas syndrome underwent laboratory polysomnographic recordings. RR intervals (RR) and spectral analysis of RR by wavelet transform were used to study sympathetic (LFWV and LFWV/HFWV ratio) and parasympathetic (HFWV) activities before and after the end of respiratory events. These RR variability indexes were compared according to sleep stages (stage 2, slow wave sleep and paradoxical sleep), to the severity of respiratory events (hypopnea with or without oxygen desaturation, and obstructive apnea) and presence cortical arousal. The possible relationship between RR variability indexes before the end of respiratory events and the occurrence of subsequent CA were studied by adjusted multivariate statistic analysis. Results: After respiratory events, RR (p<0.001) and HFWV (p=0.033) decrease whereas LFWV (p=0.006) and LFWV/HFWV ratio (p=0.001) increase, without any statistical difference according to sleep stages and severity of respiratory events. Decrease in RR (p=0.001) and increase in LFWV/HFWV ratio (p=0.008) were significantly higher when respiratory events gave rise to CA. Multivariate analysis showed that high level of LFWV and LFWV/HFWV ratio during respiratory events were related to CA (p<0.001). Conclusion: These results suggest that the sympathetic cardiac reactivity to respiratory events is modulated by arousal process rather than by sleep stages or severity of respiratory events, and reciprocally, sympathetic dominance during respiratory events could facilitate the occurrence of subsequent cortical arousal.