Alice diagnostic equipment

All patients underwent standard PSG in accordance with the American Academy of Sleep Medicine (AASM) recommendations,14 (link) with six leads for electroencephalography, electrooculography, electromyography for the chin and legs, electrocardiography, oxygen saturation (SPO2), thoracoabdominal movements, and airflow (thermistor and nasal pressure), using Alice^® diagnostic equipment (Philips, Respironics Inc., Murrysville, PA, USA). Raw data were scored manually according to the AASM scoring criteria.14 (link) Hypopneas scoring criteria included a decrement in nasal pressure signal by ≥50% for at least ≥10 seconds, followed by a ≥3% desaturation from the pre-event baseline or arousal. The desaturation index was computed as the number of desaturations (drop in oxygen saturation of ≥3%) divided by total sleep time expressed in hours. Obstructive apneas and hypopneas were calculated during REM and NREM sleep and expressed as REM-AHI and NREM-AHI.
REM-predominant OSA was defined as an obstructive AHI of ≥5, with a REM-AHI that was two times the NREM-AHI (REM-AHI/NREM-AHI of more than 2), an NREM-AHI of less than 15 events/h, and a minimum of 15 min of REM sleep.5 (link) Patients with an obstructive AHI of more than 5 events/h but did not fulfill the criteria for REM-predominant OSA were considered as having a non-stage-specific OSA group (NSS).

All referred patients with suspected SBD undertook a standard level I overnight attended polysomnography (PSG) using the Alice^® diagnostic equipment (Philips, Respironics Inc., Murrysville, PA, USA). Manual scoring of the raw data was done following scoring criteria of the American Academy of Sleep Medicine.19 The adopted definition of the desaturation index was ≥3% decrease in oxygen saturation from the pre-event baseline. The scorers of the sleep studies were blind to the results of the thyroid function test.