E series

All patients underwent a night of standard vPSG (Compumedics-E series, Australia) monitoring in the sleep center. The basic recordings included electroencephalogram (F3-A2, F4-A1, C3-A2, C4-A1, O1-A2, and O2-A1), electrooculogram (EOG, LOC-A2, and ROC-A1), chin EMG, electrocardiogram, nasal-oral pressure transducer airflow, thermal oronasal airflow, thoracic and abdominal respiratory efforts, oxyhemoglobin saturation, snoring sound, and body position. All the vPSGs were manually scored by experienced technologists according to the American Academy of Sleep Medicine guidelines.
The following vPSG data were obtained and analyzed: awakenings; total sleep time (TST); sleep efficiency (SE); sleep latency (SL); REM sleep latency (REML); wake after sleep onset (WASO); percentage of sleep spent in non-REM sleep stage (NREM) 1, NREM2, NREM3, and REM sleep; arousal index; apnea-hypopnea index (AHI); minimal oxygen saturation (SaO₂); mean SaO₂; and the percentage of time spent at SaO₂ <90% (time − [SaO₂ <90%]).

Polysomnography was performed using a computerized diagnostic system (E series; Compumedics) in the Sleep Laboratory. All participants received overnight PSG according to standardized criteria by an experienced sleep technician. PSG recordings included electroencephalography, electrooculography, electromyography of the submental muscles and of bilateral anterior tibialis muscles, electrocardiography, oxygen saturation, as well as oral and nasal airflow. The PSG recordings were scored based on the standard criteria of the American Academy of Sleep Medicine.²⁵ Apnea was defined as continuous cessation of airflow for >10 s. Hypopnea was defined as a ≥30% decrease in airflow persisting for >10 s accompanied by oxygen desaturation of ≥4%. AHI was expressed as the total number of apnea plus hypopnea events per hour during sleep. The mean oxygen saturation (MSaO₂) and lowest oxyhaemoglobin saturation (LSaO₂) value were also recorded during sleep as parameters of nocturnal hypoxemia.

Body weight and height were measured in the morning, body mass index (BMI) was calculated as weight (kg)/height^{2 (link)} (m). Waist circumference was measured at a level midway between the lower costal margin and the iliac crest. Blood pressure was measured on the right arm with the participants in a sitting position, using a mercury sphygmomanometer. PSG (E series, Compumedics, Australia) consisted of the following variables: oronasal airflow, snoring, thoracic and abdominal respiratory efforts, pulse oxygen saturation, body position, electroencephalography, electrooculography, electromyography, and electrocardiography. PSG records were staged in accordance with the criteria of the American Academy of Sleep Medicine (AASM).^{15 (link)} Apnea hypopnea index (AHI) was defined as the number of apneas and hypopneas per hour of sleep. Oxygen desaturation index (ODI) was defined as the total number of episodes of oxygen desaturation ≥4% from the immediate baseline. Percentage of total sleep time spent with SaO₂ < 90% and lowest oxygen saturation were also obtained. The severity of OSA was classified as simple snoring, mild, moderate, and severe by AHI <5, 5–14.9, 15–29.9, and ≥30 events/h, respectively. PSG was repeated during the CPAP titration.