PATIENTS AND METHOD
Twenty-one patients (15 men, 6 women) aged between 36 and 73 years (mean 59.2 years) who underwent polysomnography (PSG) for the diagnosis of obstructive sleep apnea syndrome in the sleep laboratory of Atatürk Training and Research Hospital, between October 2016 and March 2017 were included in this prospective study. Patients with moderate or severe apnea (apnea-hypopnea index ≥ 15 ) and the patients who have comorbid systemic illness (such as chronic obstructive pulmonary disease, heart failure)that we think may affect sleep architecture were excluded from study. Local ethical committee approval and written informed consents from patients were obtained.
Simultaneous PSG and BIS recordings of all patients during whole night were acquired.
All PSG recordings were performed with the Philips Respironics Alice 6 Equipment under supervision of experienced sleep technicians and all recordings were manually scored by the same experienced and certified medical doctor (GY). Sleep state scorings were performed according to ”AASM Manual for the Scoring of Sleep and Associated Events”, version 2.2.
BIS monitoring was performed with the BIS vista monitor (Covidien Medtronic VISTA application revision 3.20, vista platform revision 2.03). BIS Quatro electrodes were used for recordings.
BIS and PSG recordings were started simultaneously by using the internal clocks of the devices. By the reason of the fact that BIS device records at 1 minute intervals and the epochs in PSG are 30 seconds, 1 BIS value for 2 EEG epochs were obtained and used for analysis.
Only sleep stages lasting 2 minutes or more were included in the analysis (stable sleep / awake state). BIS signals with a signal quality index (SQI) <50 were not analyzed.