AB 83. EEG significance in polysomnography applying continuous positive airway pressure therapy (CPAP) in patients with Obstructive Sleep Apnea Syndrome

Background: The goal of this study is to explore the variations of EEG and evaluate the impact of its recording upon the process of discovering the optimal CPAP pressure, aiming at eliminating Obstructive Sleep Apnea episodes.

Patients and methods: 34 individuals diagnosed of OSAS by a polysomnography (PSG) were included in the study to whom during a second PSG a titration of CPAP was performed. The patients were divided in two groups depending on the Sleep Efficiency (SE) during the CPAP titration. The SE variation in relation to the initial PSG was further used to separate the patients into three sub-groups showing stable, improved or decreased SE. The examination of the EEG commences 5 minutes before and ends 5’ after finding the optimal CPAP pressure. For the analysis of the EEG Fractal dimension (FD) and Sample Entropy were used.

Results: No statistically important findings emerged comparing the eras before and after finding the optimal pressure in regards to the FD and its parameters in EEG. An important statistical difference between the 2 patients groups was found in the stages of sleep (S2 P=0.011, S3 P=0.029, REM P=0.026), the sleep total time (P=0.000), the latency of each stage (S2 P=0.036, S3 P=0.014). All groups showed a tendency of entropy decline after the optimal CPAP pressure, but it wasn’t statistically important. In the sub group of patients with diminished SE, a significant statistical difference was found between the various sleep stages that the optimal pressure was found, with the mean value of entropy (P=0.024) and its variation (P=0.001), as well as in the coefficient variance of the FD (P=0.040) and the mean FD values before (P=0.005) and after (P=0.05) the optimal CPAP pressure.

Conclusions: The changes in the EEG, as it appeared from the analysis of the various parameters using FD and Sample Entropy, are considered indirect evidence of the improvement of the EEG signal and therefore the microstructure of sleep. Further analysis is needed to evaluate the significance of EEG during CPAP titration.