Color density spectral array for quick evaluation of sleep during nasal continuous positive airway pressure

EEG color density spectral array enables quick evaluation of sleep. The aim of the study was to evaluate if an easily calculated sleep score based on this method could be used to assess the improvement of sleep after nasal continuous positive airway pressure (CPAP) in patients with sleep apnea syndrome (SAS). Eight hours of sleep are displayed on a single sheet along with EEG amplitude, 2 EEG channel spectra (FFT), electromyogram envelope and electro-oculogram. The x-axis corresponds to time, the y-axis to EEG frequency (range 0-16 Hz), and the color to the frequency power. This system allows the detection of sleep spindles, REM sleep and deep sleep (stages 3 and 4) as well as the evaluation of the sleep cyclic organization and its fragmentation by apnea. Based on these findings a sleep score is calculated. Eight young normal subjects were successively recorded as well as 15 SAS patients and with and without nasal CPAP. During the 1st night, the sleep score was lower in SAS patients than in normal subjects. With CPAP the apnea number decreased and the sleep score returned to normal in all patients except 1. A positive correlation was found between sleep score and duration of stage 2, stage 3 or REM sleep. A negative correlation was found between sleep score and the apnea index. This sleep score enables a quick and reliable evaluation of sleep in patients with SAS before and during nasal CPAP.